Essential Practice of Neurosurgery [1st ed.] 9784904992012, 4904992016

Citation preview

I

CONTENTS Foreword Kazadi K.N. Kalangu ..............................................................................................

XI

Professor Head of department of neurosurgery Director of postgraduate training program in neurosurgery and neurosciences Second Vice President World Federation of Neurosurgical Societies (WFNS) President of Associations of Neurosurgical Societies of Africa (ANSA) University of Zimbabwe – College of health sciences Harare – ZIMBABWE

Yoko Kato M.D........................................................................................................

XII

Chairman of the Education and Training Committee of the WFNS Secretary of WFNS foundation Professor, Department of Neurosurgery Fujita Health University

Gilbert Dechambenoit ...........................................................................................

XIII

Professor of Neurosurgery Secretary of the College of Neurosurgeons (France) Chairrman_Pan African Association of Neurological Sciences /Neurosurgery Editor-in-Chief African Journal of Neurosurgical Sciences

Preface Armando Basso MD, PhD ....................................................................................

XIV

President of the WFNS Foundation Director of Neurosciences Institute Buenos Aires University

Madjid Samii, M.D., Ph.D. ...................................................................................

XV

Pesident of the International Neuroscience Institute (INI) at Otto-von-Guericke-University President of China INI Chairman (Retired) of Neurosurgical Departments Medical School Hannover and Nordstadt Hospital Hannover Honorary President of the World Federation of Neurosurgical Societies

Albert L. Rhoton, Jr., M.D. ...................................................................................

XVI

R.D. Keene Family Professor and Chairman Emeritus Department of Neurosurgery University of Florida Member Honorary Editorial Board

Alexander Konovalov ............................................................................................

XVII

Director of the Burdenko Neurosurgery Institute

Peter Black ............................................................................................................... XVIII President, World Federation of Neurosurgical Societies Department of Neurosurgery Brigham and Women's Hospital,Harvard Medical School, Boston, MA

II CONTENTS Jacques Brotchi, MD, PhD, FACS, ......................................................................

XIX

Past-President of the World Federation of Neurosurgical Societies (WFNS) Emeritus Professor & Honorary Chairman Department of Neurosurgery, Erasme Hospital-Université libre de Bruxelles

Maurice Choux

............................................................................

XX

Department of Pediatric Neurosurgery Hopital La Timone Marseille, France

Edward R. Laws, MD, FACS .................................................................................

XXI

Department of Neurosurgery Brigham & Women's Hospital, PBB3

Atos Alves de Sousa, M.D., Ph.D. ........................................................................

XXII

Chairman of the Education and Training Committee of the WFNS Professor and Chairman of Neurosurgery Faculdade de Ciências Médicas de Minas Gerais Santa Casa and Life Center Hospital

Albino Bricolo, M.D. ............................................................................................. XXIII Past President WANS Vice-President WFNS Professor Department of Neurosurgery University Hospital of Verona

Tetsuo Kanno .......................................................................................................... XXIV Founder of ACNS Vice President of WFNS Member of the Director of Fujita Health Univ. Emeritus professor of Fujita Health Univ.

Roberto C. Heros, MD ..........................................................................................

XXV

President, XIV World Congress of Neurological Surgery of the World Federation of Neurosurgical Societies Lois pope Life Cente Professor and Director Department of Neurosurgery University of Miami

Robert Spetzler, M.D., Ph.D. ................................................................................ XXVI Director, Barrow neurological Institute J.N. Harber Chair, Division of Neurological Surgery Barrow Neurological Institute Phoenix, Arizona

James T. Rutka, MD, PhD, FRCSC, FACS, FAAP, ........................................... XXVII Dan Family Chair in Neurosurgery, Professor and Chairman, Division of Neurosurgery, The University of Toronto

Essential Practice of Neurosurgery ...........................................................

XXVIII

CONTENTS

III

Ⅰ. Introduction 1 . The Making of a Great Neurosurgeon ................................... Madjid Samii

2

2 . The Making of An Excellent Neurosurgeon ............................................ Jacques Brotchi, Florence Lefranc, Michael Bruneau

4

3 . Ein Helden Leben: A Life in Neurosurgery ..................................... Michael L.J. Apuzzo, Edwin M.Todd, Trent H. Wells, Jr.

6

4 . Towards a better future in profession and life for women neurosurgeons-and their patients ................................................ Yoko Kato

20

Ⅱ. General Principle 1 . Anatomical Basis of Skull Base Surgery: Skull Osteology ......... Carolina Martins, Alvaro Campero, Alexandre Yasuda, Shigeyuki Osawa, .................. Luiz Felipe Alencastro, Luiz Carlos de Alencastro, Albert Rhoton Jr.

24

2 . Neurological Examination ............................ Junko Matsuyama, Anil Sangli

36

3 . Evaluation and Management of Coma Patients ................................................................................ Jun Shinoda, Yoshitaka Asano

51

4 . Nutritional management in neurosurgical field ................... Chie Mihara

67

5 . Anaesthesia for intracranial surgery: general principles ............................................................................... Pol Hans, Vincent Bonhomme

72

Ⅲ. Neuro-oncology 1 . Brain Tumor Surgery in Eloquent Areas ............................................................................ Roberto Zaninovich, Peter Black

82

2 . Venous system in brain tumor surgery ...................................................................... Tetsuo Kanno, Kostadin Karagiozov

97

3 . Brain Tumours ................................................ Kathleen Joy Khu, Wai Hoe Ng

116

4 . Current Management of Parasagittal Meningiomas ............................................ Jacques Brotchi, Florence Lefranc, Michael Bruneau

128

5 . Principles and practice of skull base surgery ...................................................................... Madjid Samii, Venelin M. Gerganov

144

6 . Microsurgical treatment of Olfactory Groove Meningiomas ................. Rossana Romani, Martin Lehecka, Mika Niemelä, Juha Hernesniemi

154

IV CONTENTS

7 . Surgical Treatment of Complex Tumors of The Anterior Skull Base: The Transbasal Extended Approach ............ Miguel A. Arraez

162

8 . Parasellar Meningioma (Tuberculum Sellae Meningioma) ............................................................................... Hee-Won Jung, Chul-Kee Park

174

9 . Petroclival Meningioma ..................................................... Lixin, Zhao Jizong

179

10. The optimal protocol of treatment for petroclival meningioma ............................................. Tetsuo Kanno, Kostadin Karagiozov

182

11. Foramen magnum meningioma ................................... Mitsuhiro Hasegawa, Koichiro Yoshida, Tsukasa Kawase, ............................................................................Junko Matsuyama, Yuichi Hirose

187

12. Assessment of Pituitary Function ........ Carrie R. Muh, Nelson M. Oyesiku

194

13. The Surgical Management of Pituitary Adenoma ............................................................................ Ian F. Dunn, Edward R. Laws, jr.

221

14. The Endoscopic Transsphenoidal Approach: Evolution and Personal Experience ......................................... Gail Rosseau

233

15. Management of Pituitary Tumors with Supra-Sellar Extention ................................... Andre A. le Roux, Fred Gentili

241

16. Non-functioning pituitary adenomas ................................................................... Armando Basso, A. Chervin, N. Vitale

246

17. Treatment of patients with Acromegaly ................................... Fred Gentili

263

18. Craniopharyngioma .............................................................. Takayuki Inagaki

270

19. Craniopharyngioma ............................................. Chandrashekhar E Deopujari, Vikram S Karmarkar

274

20. Posterior Fossa Tumor .......................................................... Takayuki Inagaki

286

21. Surgery of Vestibular Schwannomas ...................................................................... Madjid Samii, Venelin M. Gerganov

304

22. Management of Vestibular Schwannoma ........................... Basant K Misra

313

23. Intraventricular Tumors .................. Chandrashekhar E Deopujari, N.Biyani

328

24. Surgical Management of Gliomas ............................................ Keki E. Turel

340

25. Tumors of the Optic Pathway and Hypothalamus ........................................................................... M. Memet ÖZek, Kamran Urgun

348

26. Biological basis for understanding of temozolomide-based chemotherapy for malignant gliomas ................................... Yuichi Hirose

362

CONTENTS

27. Pineal Region Tumors ................. Alexander.N.Konovalov, D.I. Pitskhelauri

V

371

28. Surgical Removal of Neoplasms in the Pineal Region via an Infratentorial Supracerebellar Keyhole Approach ....................................................................... Qing Lan, Zhigang Gong, Yufu Zhu

392

29. Brain Metastases ............................................................ Gilbert Dechambenoit

403

30. Gamma Knife Radiosurgery for Metastatic Brain Tumors ........................................................................................................... Toru Serizawa

411

Ⅳ. Vascular neurosurgery 1 . Management of the Unruptured intracranial aneurysms ............................................................................. Akio Morita, Toshikazu Kimura

420

2 . Natural history of aneurysmal subarachnoid hemorrhage and risk factors of rebleeding ........................................ Hildo R. C. Azevedo-Filho, Moysés L. Ponte de Souza, ......................................................................Saul C. M. Quinino, Renata Azevedo

434

3 . Subarachnoid Hemorrhage ................................ Yoko Kato, Hirotoshi Sano

446

4 . Language and cognitive disturbances following aneurysmal subarachnoid hemorrhage ........................................ Hildo R. C. Azevedo-Filho, Moysés L. Ponte de Souza, ................ Ana Cláudia C. Vieira, Saul C. M. Quinino, Renata Cirne de Azevedo

459

5 . Cerebral Vasospasm ....................................................................... Rahul Mally

472

6 . Anterior communicating artery aneurysms .......................................... Yoko Kato, Hirotoshi Sano, Junpei Oda, Shuei Imizu

477

7 . Anterior Circulation Cerebral Aneurysms ....................................................... Michel W. Bojanowski, Nancy M.C. Laughlin

483

8 . Surgical Management of Giant Intracranial Aneurysms ..................................................................... Matthew O. Hebb, Robert F. Spetzler

503

9 . Treatment of complex intracranial aneurysms of anterior circulation using multiple clips ............................... Hirotoshi Sano, Yoko Kato, Takeya Watave, Daikichi Oguri

516

10. Cerebral Arteriovenous Malformations ............................ Ivan Ng, Jai Rao

527

11. Microsurgical principles to remove cerebral arteriovenous malformations. ....................... Juha Hernesniemi, Rossana Romani, Mika Niemelä, Aki Laaksos

540

VI CONTENTS

12. Management of Deep-Seated Arteriovenous Malformations ................................................. Maria Toledo, Shervin Dashti, Robert F. Spetzler

546

13. Gamma Knife Radiosurgery for Arteriovenous Malformations .................................................................... Masaaki Yamamoto, Bierta E. Barfod

558

14. Dural Arterio-Venous Fistula (d AVF) .............................. Makoto Negoro

571

15. Practical Endovascular Neurosurgery ...................... Akiyo Sadatou, Motoharu Hayakawa, Makoto Negoro, Keiko Irie

574

16. Cavernous Angiomas ............... Nancy MC Laughlin, Michel W. Bojanowski

583

17. Bypass Surgery for Moyamoya Disease .............................................. Kiyohiro Houkin, Satoshi Iiboshi, Takeshi Mikami

601

18. The basic technique of OA-PICA anastomosis: Surgical anatomy and the Detail ...................................... Rokuya Tanikawa

610

19. Carotid Endarterectomy .................. Atos Alves de Sousa, Bruno Silva Costa

616

20. Carotid Endarterectomy .............. Markus Bookland, Christopher M. Loftus

628

21. Functional neuroimaging for secondary stroke prevention using bypass surgery ....................................... Jyoji Nakagawara

642

22. Endoscopic removal of intracerebral hemorrhage ............................... Takeya Watabe, Daikichi Oguri, Yoko Kato, Hirotoshi Sano

653

Ⅴ. Head Trauma 1 . Head Trauma ................. Ahmed Ammar, Mariam AlRashid, Munir Nasser, Hosam Al Jehani, ...................................................... Ossama Abd Al Hadi, Abdul Rahman Al Anizi

660

2 . Neurotrauma, The ABC’s ................................................ Sharad S. Rajamani

680

3 . Management of severe traumatic brain injury (TBI) ......................................................................... Alexander Potapov, L. Likhterman

689

4 . Neuromonitoring for Head Injury Monitoring of intracranial pressure and cerebral blood flow and metabolism -basic and advanced monitoring tools............................................. Nobuyuki Kawai, Kenya Kawakita, Takashi Tamiya

699

5 . Depressed Skull Fracture ............................... Ápio Cláudio Martins Antunes, André Cerutti Franciscatto, ............................................................. Rafael Modkovski, Thiago Torres de Ávila

716

CONTENTS

6 . Extended Decompression and Neuroprotection for Traumatic Brain Injury (TBI) ............. Tomoya Miyagi, Minoru Shigemori

VII

724

7 . Therapeutic Hypothermia for Traumatic Brain Injury .................................................................................................... Takashi Tokutomi

731

8 . Traumatic Brain Injury in Children .......................... Alexandru V Ciurea, Stefan M Iencean, Aurelia Mihaela Sandu

734

9 . New trends in the pathophysiology, diagnosis and treatment of diffuse axonal injury: A proposal of simple guidelines ............................... Visocchi Massimiliano

745

Ⅵ. Spine 1 . The importance of neurological examination for Spine Disorders ................................................... Gene Bolles, Lars Widdel

752

2 . Treatment for craniovertebral instability ........... Atul Goel, Abhidha Shah

762

3 . Transoral approach to the skull base and the upper cervical spine .............................................. Visocchi Massimiliano

781

4 . Cervical posterior approach: Laminoplasty ........................... Satoshi Tani

790

5 . Anterior approach to the cervical spine for degenerative spinal disorders ......................................... Izumi Koyanagi

800

6 . Surgical Management of Cervical Disc Herniation ..................... Patrick-Alain Faure, Jean-Jacques Moreau, Gilbert Dechambenoit

808

7 . Cervical Spine Injuries ........................................................... Bernard Irthum

822

8 . Treatment of Thoracolumbar Injuries ....................... Toussaint A Leclercq

842

9 . Basic techniques of the Lumbar Spine Surgery .................................... Yoshitaka Hirano, Junichi Mizuno, Sadayoshi Watanabe, .................................. Shinichi Numazawa, Tadao Matushima, Kazuo Watanabe

852

10. Surgical Management of Lumbar Stenosis ............ Gilbert Dechambenoit

863

11. Lumbar Disc Surgery ............................................ Muhammad Raji Mahmud

878

12. Isthmic Spondylolisthesis in Adults Surgical Treatment .................................................................... Jean-Marc Fuentes, StéPhane Fuentes

893

13. Minimally Invasive Treatments for Spinal Degenerative Pathologies. ...................................... Alberto Alexandre, Andrea M. Alexandre

903

VIII CONTENTS

14. Percutaneous Endoscopic Lumbar Discectomy (PELD) -Transforaminal and Interlaminar approaches- ......................... Fujio Ito

939

15. Persistent and recurrent lumbosciatica after lumbar discectomy. Surgical aspects of Failed Back Surgery Syndrome. ................................................................... Svetoslav K. Kalevski, Nikolay A. Peev

947

16. Spinal tumors ...................... Suresh Nair, Girish Menon, Ravi Mohan Rao, Mathew Abraham, ............................................................................... Harihar Easwer, Krishnakumar

958

17. Current Management of Intramedullary Spinal Cord Tumors .................... Jacques Brotchi, Florence Lefranc, Ryad Djedid, Michael Bruneau

980

18. Metastatic Tumors of the Spine Surgical Management of Symptomatic Spinal Metastases ............................................................................................... Perrin, RG, Wilson, J

992

Ⅶ. Peripheral nerve 1 . Notions regarding the basic management of peripheral nerve injuries, compression syndromes, and tumors ....................................... Mariano Socolovsky, Mario Siqueira, Roberto Martins, ........................................................................ Gilda Di Masi, Eduardo Fernández 1016

2 . The benign tumors of the peripheral nervous system. .............................................................. Alberto Alexandre, Andrea M. Alexandre 1037

Ⅷ. Functional Neurosurgery 1 . Introduction to Stereotactic and Functional Neurosurgery ............... Takaomi Taira, Taku Ochiai, Hiroyuki Akagawa, Tsuyoshi Nakajima, ................................................... Shinichi Goto, Toshiyuki Sasaki, Ayako Mandai 1058

2 . Surgery for Parkinson’ disease ................. Sylvie Raoul, Jean-Paul N’Guyen 1077 3 . Neurosurgical Management of Neuropathic Pain ................................................................................ Marc Sindou, Patrick Mertens 1085

4 . Motor cortex stimulation in neuropathic pain : Technique and perspectives ............................................................. Benoit Jm Pirotte, Mathieu Bourguignon, ................................................................ Philippe Voordecker, Danielle Baleriaux 1098

5 . Neurosurgical management of Trigeminal Neuralgia ........ Marc Sindou 1117

CONTENTS

IX

6 . Microvascular decompression: Analysis of un-successful cases ........... Tetsuo Kanno, Kostadin Karagiozov 1121 7 . Percutaneous Techniques for Treatment of Trigeminal Neuralgia ....................................................... Benaissa Abdennebi 1139 8 . The Management of Spasticity .............................. Sasha Burn, James Drake 1150 9 . Neurosurgical Management of Spasticity ................................................................................ Patrick Mertens, Marc Sindou 1165

10. Surgical Management of Epilepsy ........... Praveen R. Baimeedi, Ug˘ur Türe 1176 11. Surgical Treatment of Epilepsy................................................... Badih Adada 1190 12. Epilepsy Surgery in Children ............................ Ryan Alkins, James T Rutka 1199

Ⅸ. Pediatric Neurosurgery 1 . Past, Present, and Future of Pediatric Neurosurgery ..... Maurice Choux 1218 2 . Arachnoid cysts ............... Concezio Di Rocco, Luca D’Angelo, Luca Massimi 1235 3 . Developmental Anomalies of the Central Nervous system ........................................................................... Cheng Kiang Lee, Wan Tew Seow 1244

4 . Pediatric Neurosurgery ........................................................ Takayuki Inagaki 1255 5 . Encephaloceles ...................................... Seydou Badiane, Kazadi K.N.Kalangu 1282 6 . Spinal Dysraphism ........................... Patrick Dhellemmes, Matthieu Vinchon 1290 7 . Traumatic Spine injury in Childhood ................................................................ Matthieu Vinchon, Patrick Dhellemmes 1310

8 . The Craniovertebral Junction in Children: Normal Development and Management of Developmental Anomalies ............... Shobhan Vachhrajani, James T. Rutka 1327

Ⅹ. Parasitosis and infections 1 . Brain Abscess ............................... Ápio Cláudio Martins Antunes, André Cerutti Franciscatto, ............................................................. Rafael Modkovski, Thiago Torres de Ávila 1350

2 . Intracranial Supuration ................................................. Kazadi K.N. Kalangu 1363 3 . Neurocysticercosis ......................................................... Vedantam Rajshekhar 1379

X CONTENTS

4 . Neurocysticercosis .............................. Marcos Dellaretti, Atos Alves de Sousa 1390 5 . Brain and Spinal Hydatidosis ........... Najia El Abbadi, Kazadi K.N. Kalangu 1402

É. Miscel Ianeous 1 . Physiopathology of Intracranial Hypertension ......................................................................................... St M Iencean, AV Ciurea 1418

2 . Idiopathic Intracranial Hypertension (Pseudotumor Cerebri) ................................................... J. André Grotenhuis 1428 3 . Pathophysiology and Treatment of Hydrocephalus ................................................................................................. J. André Grotenhuis 1441

4 . Normal Pressure Hydrocephalus: from a practical point of view ................................................ Kiyoshi Takagi 1455 5 . Chronic CSF Depletion Syndrome (Intracranial Hypotension Syndrome) ....................... J. André Grotenhuis 1464 6 . Endoscopic Third Ventriculostomy (ETV) ......................... Tamotsu Miki 1473 7 . Neurosurgeon training in China ......................... Zhao Yuanli, Jizong Zhao 1479 8 . Educational laboratories for young neurosurgeons ................. Ling Feng 1481

Ⅰ. Introduction

2

The Making of a Great Neurosurgeon MADJID SAMII, MD, PhD President - International Neuroscience Institute, Rudolf Pichlmayr Str. 4, 30625 Hannover, Germany Key words: neurosurgery, training in neurosurgery, surgical skills

The career in neurosurgery is built on several cornerstones: the personality and intellectual ability of the person, the level of the teacher, and the quality of the training program. For a successful career in neurosurgery, the basic education and training are of fundamental importance. There are two main concepts related to the philosophy of education in neurosurgery: in the first the focus is put on theory (study of textbooks, guidelines, internet sources etc.), while in the second the focus is the practical training (or “learning by doing”- concept). The ideal training should be based on a balance between theory and practice. Factors that influence the neurosurgical education are the ability of the educators and trainees on the one hand, and the organization of the program and technical standards in the teaching center, on the other hand. The influence of an educator or mentor is of paramount importance. His/her knowledge and behavior should be live examples to follow for the trainees. It is almost impossible to become a great neurosurgeon without having a teacher with a high level of moral and ethic - a person that demonstrates honesty in his professional behavior, both to his pupil and to his environment. In a good neurosurgical school, the patient's welfare must be in the center of all considerations. The knowledge in neurosurgery and neurosciences are growing permanently and the management standards are improving. Therefore, the competent and excellent educator must have the ability to remain flexible and capable to keep with the changing demands. He/she has to have high ability for acquisition of new knowledge, for its critical appraisal, and for its clinical application. There are many parameters that could be considered as a prerequisite for a trainee to become a great neurosurgeon: family background; outstanding results at school; sport activity; ability to play a musical instrument, languages proficiency; social engagement; motivation for neurosurgery; knowledge how to write a good scientific paper; ability to present a project. But all these cannot substitute for the character of the person. Honesty and dedication to the patients from the beginning of the education will determine the success in the future. What about the technical skills? Generally, it is believed that the skill of a neurosurgeon is equal to his manual dexterity. According to my personal experience with hundreds of pupils, I found that only those could make great careers who were dedicated and competent in all aspects, related to the patent's management: starting with the thorough history taking, complete examination and analytical evaluation of neurological, neurophysiological, neuroradiological findings, and laboratory findings. Besides, it is

The Making of a Great Neurosurgeon

3

essential that the trainee has a profound interest in the social life, mental condition and expectations of the patient. Last but not least, the endurance, mental power and health condition of the trainees during surgeries influence the stability of their performance. The manual skills reflect the intellectual ability for analysis of different situations during surgery. I do not believe that a very skillful artist who is able to perform repeatedly a very complicated piece would necessarily become a skillful neurosurgeon. For the career of a great neurosurgeon, the research activity is of great value. Both basic and clinical research is fundamental to achieve an academic position. I always give an advice to my young residents to start as soon as possible to work on scientific projects and write papers. After finishing such a paper they learn how to plan a study project, to organize and perform it; how to decide on and carry out the varying statistical evaluation of the data; and how to review the relevant literature. Moreover, they acquire the expertise and knowledge on the state of the art of a certain topic. A great neurosurgeon has to continue in all his professional life the scientific research and keep the ambition to develop and further improve neurosurgery to the benefit of his patients. Notably, the patient has to remain always in the center of his/her attention.

4

The Making of An Excellent Neurosurgeon JACQUES BROTCHI MD, PhD, FLORENCE LEFRANC MD, PhD and MICHAEL BRUNEAU MD Department of Neurosurgery, Erasme Hospital-Université libre de Bruxelles Key words: neurosurgeon, excellgce, humility, multidisciplinary, experience Humility, honesty, availability, team spirit and hard work are some of the conditions to make an excellent neurosurgeon. Combination of brain excellence and hand skilful is one of the characteristics of an outstanding neurosurgeon. Training in allied specialties is also a key. To-day, with the development of imaging, patients are coming with their CD-Rom when asking our opinion. We should never forget we have to cure patients but not pictures. Therefore, good knowledge in medical neurology, neuroradiology and pathology is really helpful in taking a good decision on the indication for surgery. Taking time making a good anamnesis and precise neurological examination contributes to an excellent diagnosis. Taking time to talk with the patient and family before and after surgery is the base of confidence. Even if we are micro-neurotechnicians, we should never forget human sense. We should teach our trainees to avoid falling in computerized world and remind them that a patient is a human being waiting for clear explanations on the treatment and post-operative course. In addition, a patient has also an anxious family waiting for daily news. An excellent neurosurgeon should combine technical and heart qualities. Availability to the patient, the family, the nurses and younger colleagues is also a way of life we should teach. That also means a team spirit. To-day, neurosurgery in no more a one man show. Multidisciplinary approach is mandatory. Moreover, a leader must share his knowledge with younger colleagues who should be associated in all events. Excellence is also based on experience. Experience means success and pitfalls. Success in 100% of our surgeries does not exist and we should learn from our mistakes or pitfalls. Every complication should be analyzed and be a lesson for avoiding its repetition. Therefore, humility and honesty make a neurosurgeon greater. A colleague who declares he has no complications, no pitfalls, who has 100% success in his hands, is a danger for our specialty and should never be trusted. It is our duty to train our fellows in a tradition of auto-critics whenever something uneventful happens. Knowledge of his limits is also a key, but it should not hidden self-confidence which is close-related with experience. About surgery itself, there are no small details. Every step is important. An example is the position of the head which makes the procedure easy of difficult. Learning all

The Making of An Excellent Neurosurgeon

5

approaches makes the difference between a neurosurgeon prisoner of one way to go and the other who is able to propose the best approach to cure in a panel of different approaches. Hand skilful is also based on hours of work and training in the lab and in the operative theatre. Neurosurgery of excellence needs a combination of a well trained brain with skilful hands. It means hours of hard work during training time but also after. Learning from colleagues all our life is a guarantee to stay aware of all new development and progress. We should never stop learning. Our specialty is in constant progress and excellence also means to be aware of all new publications on research and development. Facilitating and encouraging research (basic and clinical) from our young trainees will stimulate new vocations towards finding solutions in different problems we still have to face like vasospasm or malignant brain and spinal cord tumors. At the end, I want to say that a teacher should be proud when he is surpassed by his fellows.

6

Ein Helden Leben: A Life in Neurosurgery MICHAEL L.J. APUZZO, M.D., Ph.D. (hon) EDWIN M.TODD/TRENT H. WELLS, JR. Professor of Neurological Surgery, Radiation Oncology, Biology and Physics Keck School of Medicine, University of Southern California, Los Angeles, CA USA Key words: neurosurgery, autobiography There are many exciting and noble professions but the gravity and concept of a life in neurosurgery is clearly in its own category of elite status. It is a life of involvement with the dramatic events of life and death and a terrible gray area in-between where lives are disrupted and emotional pain is intense. It is by any measure an extraordinary calling. This is a brief and somewhat fragmented story of a life in neurosurgery-–my life

I. Beginnings New Haven, Connecticut is a smallish Connecticut town rooted deep in American colonialism and uniquely blessed by the presence of Yale University within its limits. It is a physically beautiful setting on Long Island sound, multicultural but predominantly Italian in its inhabitants' cultural origins. I was born just before the second World War. My father, Dominic, a machinist and fine craftsman, was a devoted husband and exemplary father. Intelligent and diligent, he at times worked as many as three individual jobs to maintain the upward mobility of his family. Our paternal ancestors were from Amalfi, Italy. Sailors for generations, they left Italy for Argentina in the early twentieth century with the advent of steam, an Atlantic storm and damaged ship brought them to Ellis Island in New York. My mother, Ann Lawrence, was a nurse. Multifaceted in talents, she was a mother who challenged her children to excel and left no stone unturned to provide an intellectually fertile environment directed to music, art painting, and sports. The Lorenz family, Austrian in origin, had originally migrated to Mahoney City, Pennsylvania, where my grandfather worked in coal mines, later with my grandmother, they migrated to New Haven. My original home was a two family edifice with a chicken coop set in a "collision" area for Italians, Blacks, and Hispanics in what might be termed a somewhat less than desirable part of town. The atmosphere within the family was clearly upwardly mobile with progress in both education and socioeconomic status expected and driven home emphatically each day. Progress and change was expected on all fronts with hard work, perseverance, and sustained goal orientation at the base of the behavioral pattern. Honesty and a firm moral grounding in Catholicism was stressed. As the oldest of three siblings I was expected to be a "pathfinder," setting the pace for my young brother and sister. I was immersed in the piano, painting, the public library, films and sports at

Ein Helden Leben: A Life in Neurosurgery

7

an early age–interests that would be life threads.

II. Education At the age of four we moved to Westville, a largely middle class part of town, first in an apartment and later in a three family house in a predominantly second generation Irish culture. Our move was impaired by prejudice and bigotry that existed at the time related to our Italian surname (after WWII). The Lorenz name was changed to Lawrence and this was used to allow initial entry into the area. Due to the style of my parents and a supportive group of Irish friends, I hardly felt a ripple. After a brief period in public school, I transferred to Saint Aidans Elementary, a parochial school established by our parish church where discipline and religion were emphasized. The nuns, predominantly Boston Irish in origin, affected a peculiar brand of education–effective with strong points of order and a fundamental sense of respect for classes but with overtones of anger and prejudice. I was one of only two Italian in the class and was constantly reminded of it–in less than flattering terms. Even at the age of ten I found this curious and reveled in the multicultural attitude of my parents who stressed the dramatic beauty of differences of racial and cultural groups. Problematically, the Sisters of Notre Dame insisted that all should set their course to cut a path to Catholic secondary education. At the age of twelve I decided that things would be different for me. Hopkins Grammar was secondary school for boys, a preparatory school that offered an enhanced opportunity for an elite college or university education. I had been introduced to it through a summer camp where counselors were either faculty members or students at Hopkins. I visited the campus–like an old English boarding school in the film "Tom Brown's School Days." It was for me! Largely comprised of students who were children of professionals and Yale faculty members, it offered a unique experience. Founded in 1660 it was steeped in the tradition of American Colonial times and insisted on honing individuals in all respects–mind and body–art, culture, music, history, classics, language etc etc. It was an elite and invigorating environment and my acceptance there was a major turning point in my life, giving me the opportunity to develop and grow and to have a chance to be accepted at Yale College. As a good but not exceptional student and much better than average athlete, I was accepted by early action decision at the College. Their decision was no doubt further influenced by my New Haven residence, Italian surname and some strange endorsement of Hopkins Headmaster F. Allen Sherk, a former Yale man, Mr. Sherk–a strict Puritan–presided over a no nonsense–zero tolerance environment. Perhaps he was taken with my effort or application to tasks or my emerging romanticism and idealism. I entered Yale at 16 from a class of 40. I suddenly was consumed in a class of 1000–I was overwhelmed! As a freshman, I survived academically and even made the Dean's Honor list due to my Hopkins grounding. I had initially entered with ideas of a career in architecture. (I was a moderately gifted painter and sculptor and had won a number of local prizes). However, the introductory course challenged my discipline in that chaotic Yale environment. Coming from a family heavily engaged in the medical profession as nurses, I felt some indirect pressure to consider that course but initially I resisted.

8 Introduction

Fig. 1 Cushing Historical Library, Yale School of Medicine, New Haven, Connecticut

During my sophomore year my academics suffered and I was required to meet with Henry Chauncey, Dean of students for the College–I thought it was over. After a long discussion, Dean Chauncey arranged for me to work at the Medical School as part of my scholarship requirement–out of all places–at the Harvey Cushing Historical Library! (Figure 1) There my supervisor was Madelyn Stanton–the deceased Cushing's former secretary after he had returned to Yale after his time at Harvard. She was proper and stern! I would descend into the "stacks" three afternoons a week, instructed to catalogue the Cushing collection books on three by five inch cards. However, I spent time infatuated with the "ancient" tomes on medical history and Cushing's neurosurgical collection in multiple languages. Few cards were completed and I felt Miss Stanton's wrath! But I found a direction–another turning point. In those stacks I decided that I would try to enter a course in medicine. Unfortunately, I was distracted by sports involvement and social interactions. My grades, although satisfactory, were hardly of medical school candidate caliber. By March of my senior year I had had been rejected by all but one of my applications and that was the Boston University School of Medicine. I was called for an interview late in March and was taken by its intimacy, warmth, and academic flavor–only 80 students per class and associated with the then magnificent Boston City Hospital!–and Boston!! In spite of welling enthusiasm and very congenial interviews I remained guarded, even pessimistic. After finishing my time at the Cushing library, because of a secondary interest in Oceanography, I was assigned as a work student to the Bingham Oceanographic Laboratory–a fabulous place and opportunity. There I worked for Evelyn Hutchinson, the first woman to earn a PhD from Cambridge, and came into contact with the niece of John Fulton, the renowned neurophysiologist, who introduced me to many of the elements of his character. Fulton was the Chairman of Physiology at the Medical School and an exceptional neurophysiologist. He was probably one of the foremost individuals in his field in the past 100 years and a founder of the American Association of Neurological Surgeons as well as the Journal of Neurosurgery. Under the direction of Fulton's niece, I learned to do hypophysectomies in 3 inch Keli fish to determine seasonal change on gross weight. Many other interesting activities consumed my interest there and I decided to work at the lab during the summer before

Ein Helden Leben: A Life in Neurosurgery

9

my senior year. I was relatively well known as an earnest work student. Two days after the interviews at Boston University Medical School, the laboratory's director, Daniel Merriman, stopped me (I didn't even suspect that he knew who I was). Dr. Merriman inquired about my medical school progress and said–"Oh Bunny Soutter (the Dean at BU) was a classmate of mine at Harvard!" Three days later I received a letter of acceptance. Although New Haven had proximity to New York and I was familiar with that immense city, I had never lived in a major city before. Boston was a revelation. My love of music and art was indulged. I was finally out of the "nest" and I began to mature and thrive in the supportive environment of the Boston Medical setting. The order and direction of the medical program appealed to me and I naturally gravitated to subjects of anatomy, pathology, and physiology. I became especially attracted to neuroanatomy, where I excelled. In New Haven, I had ultimately majored in Psychology and Physiology and had done a senior thesis studying lobotomized patients at the West Haven Veteran's Administration Hospital. I was being drawn to a career related to diseases of the nervous system. I was attracted to a number of colorful individuals in the neurological sphere, particularly to the iconic Derek Denny-Brown, Harvard's noted neurologist-physiologist who had weekly brain cutting conferences at the Boston City Hospital. Flavir Romanul, his pathologist, was especially articulate and a unique cast of residents, students, and staff contributed to the energy of the academic theater each week, cataloguing a variety of common and esoteric neurological diseases. I was totally taken by the intellectual and dramatic exercise. But I was certain that I needed to move in a surgical direction–the combination of intellect and physicality was attractive and the exotic and challenging nature of neurological diseases were, in my opinion, unmatched. After all, my mother, an operating room nurse, had told me–"I'm happy that you're planning a career in surgery–but whatever you do, don't do neurosurgery! None of the patients do well or die!" I was moved to take up the challenge! For a variety of reasons and with the help of Richard Egdahl, the renowned endocrine surgeon, I decided to do a surgical internship at the Royal Victoria Hospital at McGill in Montreal. Egdahl has been a resident with Lloyd MacLean, the chairman of surgery at "the Vic" and had counseled me on various surgical opportunities along with John Mannick, who later left BU to be chief of surgery at the Peter Bent Brigham. Part of the attraction was the proximity of the Montreal Neurological Institute and the possible opportunity to work there–epilepsy and the mystique of Wilder Penfield and the Institute's lore were irresistible and I thought attainable. Medical school had been successful in establishing both a firm grounding and direction.

III. Surgical Transitions and Neurosurgery Montreal was a fabulous, exotic, and international place. McGill and the Royal Victoria Hospital reflected its character with the ultimate medical, surgical, and academic standards. The hospital was outstanding across the board with modern pace setting services in Cardiac, Transplant, and Orthopedic Surgery. All support services were

10 Introduction high caliber with all medical specialties superb. Many of surgery's and medicine's great luminaries seemed to be everywhere. As a "straight" surgical intern, I held special status, moving into first year resident level duties and responsibilities after three months. My four principle rotations involved general, cardiothoracic, and trauma surgeries, with every other night and weekend call in house for one year with 4 days off at Christmas! The intense experience was exhilarating. We provided full surgical support for the adjacent Montreal Neurological Institute. This gave me the opportunity to meet and observe many important people in the field, including Bryce Weir (chief resident and later Chairman at University of Chicago), Henry Garretson (junior staff member and later chair at Louisville as well as AANS president), Phanor Perot (junior staff member and later Chair at South Carolina), and the Institute Co-Directors, Theodore Rasmussen and William Feindel. As an aspiring neurosurgeon, I was welcomed, embraced, and encouraged. I was both touched and energized. However, although I had had aspirations of possibly training at the MNI, this proved not to be feasible given the lack of available openings. I was given the opportunity to work in the laboratories "in limbo" but I was anxious to move on with my training. Yale provided a great opportunity and so after a valuable year in Montreal, I returned to YaleNew Haven Hospital to begin a residency in neurosurgery. As embracing as the experience as Montreal proved to be, Yale was harsh, insensitive, and chaotic. Once again, I was struggling in transition. Entering the Tomkins 4 Ward full of hissing respirators and patients left quadriplegic from motorcycle accidents, I was shocked at what seemed to be the human carnage under my "care." At that time (July) the summer trauma was in high gear and the evidence consumed the neurosurgical service day and night, seven days a week. The house staff, all high caliber individuals, were driven by the pace and, although low in their numbers, valiantly dealt often in disruptive fashion with mayhem. I wondered, "What am I doing here?" Gradually and painfully, I adapted. Slowly the more elegant aspects of our craft began to present themselves and I began to evolve as a resident and an embryonic neurosurgeon. William German, one of Cushing's late fellows, was chairman on my arrival; he was in his seventies and in the later and closing months of his career; however, he provided inspiration and the faculty was full of highly competent individuals, all of which exhibited the strong persona required for success in the field. Upon his retirement, German was replaced by William F. Colllins, Jr., a native New Havener and Yalie who enforced high standards of practice both in the university and private setting. He was a superb role model in his consummate professionalism and devotion to the highest of intellectual standards. The bar was set exceptionally high. Although Dr. Collins had inherited me, I never felt like a step-son. He gave me attention and support, even working personally during an 18 month-laboratory experience in a complex neurophysiological experiment. He always worked beyond what was expected, passionately setting the proper example for his residents and staff. He was then and is now, for me, extraordinary. Collins went on later to be editor of the Journal of Neurosurgery and in the capacity helped me to gain experience that I would later bring into play as editor of Neurosurgery. As part of the Yale experience, we did important rotations at the Hartford Hospital, then one of the nation's busiest clinical services, with a surgical volume of more than three

Ein Helden Leben: A Life in Neurosurgery

11

thousand cases annually. This experience was, in theory, our exposure to high powered technical neurosugery–with Yale New Haven providing principally the intellectual and academic grounding. Hartford was a rich and memorable experience! There, William Beecher Scoville and Benjamin Bradford Whitcome–two giants in the field, provided the forces that drove the service. We were not only exposed to an exotic variety of problems but had exposure to Scoville's creative personality and primal force. Periodically showing evidence of technical genius, he constantly was impressive with his passion of invention and reinvention, his lust for life and thirst for the extraordinary. An avid and practicing internationalist, he was active in the World Federation of Neurosurgery and had a steady stream of international luminaries and trainees as guests. The energy and sense of vigor of the service was non-stop. There, my surgical confidence began to emerge and I was inspired by the combination of surgical events and creative forces with an eye toward progress. It lit my passion for the same and it continued to burn.

IV. Life as a Submariner My residency was formally interrupted by the Cold War and VietNam. All medical trainees were obliged to serve in some capacity. I had always been fascinated with exotic science, Jules Verne, space travel etc etc. The Submarine base at Groton (New London) was 50 miles from New Haven and the goings on at that installation were always a source of intrigue for me. Nuclear power was in its infancy and the exploits of the Nautilus, Seawolf, and Trident were a source of fascination. Given this and my "nautical genes," I volunteered for extended service on Polaris missile submarines, (Figure 2, page 1118) the most modern, complex device that man had ever devised up to that time. The duty had the added perk of training and duty as a deep sea diver with scuba, hard hat, and mixed gases qualifications. My application was accepted and in January I traveled to Groton for induction and a six-month period of training in areas of nuclear medicine, nuclear physics, radiation medicine, submarine operations, submarine design, diving, and diving medicine. It was another turning point in the honing of interests that would prevail during my time as a neurosurgeon in academia. The training was intense with 10 hours per day, six days a week of class, laboratory, and practical exercises. I presume it was military education at its best–as a product of elite

Fig. 2 Nuclear-powered Polaris Fleet ballistic missile submarine, Robert E. Lee, under way in the North Atlantic, circa 1967. The Robert E. Lee was commissioned in 1960 at Newport News Virginia, and was one of the five original 598 Class (George Washington) of submarine missile platforms. The nuclear-powered submarine changed international strategies of defense and deterrence.

12 Introduction scholastic setting, I can now say that it was the most thorough and best organized program for relating a body of knowledge and skills that I have ever experienced. At the end of this taxing mental and physical period in which 40% "washed out," I was confident and prepared to take on the challenge of hazardous duty service on a polaris submarine. I was assigned to the SSB(N) (Submarine Ship Ballistic Nuclear) 601 Robert E. Lee, a 400 ft., 7 story "monster" that was foot by foot the most expensive vehicle ever created (Figure 2). In the middle of winter, my crewmates and I left New London for Holy Loch Scotland to assume the service of the boat and undertake a sustained submerged 100 day "patrol" to regions unknown, carrying more firepower than all weapons detonated in all mankind's previous wars–but this time as a deterrent. During a series of those three month patrols, I was able to observe and contemplate regarding advanced submarine operations, complex navigation methods, nuclear events and utilizations, radiation physics, robotics, communications and satellite operations. It was a three month immersion into ultimate high technology, perhaps like none other at the time. It was a remarkable experience, particularly when combined with the concept of neurological surgery. It would be central in directing my intellectual research and ideas during next decades in neurosurgery and played a primary role in the reinvention of our field!

V. Los Angeles The last year of my military service was spent in San Francisco as nuclear medical office for San Francisco Bay. At the time, Charles Wilson, a friend of Bill Collins, was beginning his period as chairman of UCSF. Charlie was very welcoming and an important friendship was forged with that important service and Charlie himself. I returned to New Haven to finish the remaining two years of training–a relatively uneventful period except that people like Ted Kurze in Los Angeles were beginning to introduce the operating microscope into neurosurgery and we were performing a number of hyposecomies for metastatic pain and occasional clipping of cerebral aneurysms using the instrument. Collins and Kurze had served in the Army together. I met Kurze at an AANS meeting and we immediately established a bond but I wasn't interested in working at the Los Angeles County General hospital. Ted was charismatic but the service was not well grounded and its infancy was a full time academic enterprise. I desperately tried to find a job at a University but, even with Collins's help, nothing seemed to materialize. As the months passed by I was compelled to agree to taking a less than attractive opportunity in private practice. Two weeks before my residency was to end, I was contacted by my employers to be that the group had dissolved and there was no job! Collins kindly gave me a temporary appointment as Instructor at Yale but within 3 months I joined Ted Kurze at USC and I have never left (Figure 3). People had warned me about USC and the lack of future in that environment but I saw something different, a high volume of patients in a 3000 bed medical center, a futuristic thinking, colorful and charismatic leader (Kurze), and a highly intelligent, energized "big" brother in Martin Weiss, Kurze's established Vice Chairman. I quickly saw Marty as a valued colleague with solid grounding in science, high ambition, and a remarkable sparkling intelligence. In addition, I sensed a fabulous chemistry at USC with academic

Ein Helden Leben: A Life in Neurosurgery

13

Fig. 3 Los Angeles County/University of Southern California Medical Center, circa 1975.

freedom unencumbered. I sensed that anything–mostly good could happen!! I soon discovered that all I had perceived was correct but there was more–fertile resources in science, high technology, and futuristic perspective–all played into a substrait of person that had been developing during the previous three decades–I was comfortable in a second home!! But not immediately!! The most difficult times in a neurosurgeon's career are during points of transition and the period between residency and immersion in practice (either private or academic) is highly stressful. Events in the socioeconomic environment of Los Angeles impacted severely on my adaptation in spite of support from Ted and Marty. I, in spite of being in a sea of clinical opportunity, could not seem to get things started. I was very active in the training program, surgery stream, and participated in hundreds of cases–in fact, my application for the American Board of Neurosurgery Certification was thought to be exaggerated in case numbers as they had never seen the variety and volume of pathology presented in such short period. Otherwise, it seemed I had no ideas, no creative thought, no inroad to a meaningful academic contribution. Bill Collins had told me "All I would like to leave to neurosurgery is one meaningful contribution!" His words echo for me each day. For whatever reason, there seemed no opportunity in sight and a malpractice insurance crisis had me working weekends in the General Hospital Emergency Room to make financial ends meet for my young family. I began to investigate opportunities away from the university in Santa Barbara particularly–nothing seemed to fit. My board examination approached. The exams were held in Memphis, Tennessee. At that time Marty Weiss suggested that I see Harold Young at the Medical College of Virginia who had begun some innovative work on the immunology of gliomas. I had been fascinated with the immune response in our transplantation patients at the Royal Victoria and brain tumors as now, were a real challenge. I met with Harold Young after the board exam. The concept of a tumor immunology lab was born. And that began a stream of repetitive exciting events, discoveries opportunities, innovations, and major contributions that have helped to reinvent neurosurgery-–each is a story in itself. It has been a deluge of exciting events and involvement in the most exotic of settings imaginable traveling with meaningful purpose

14 Introduction throughout my country and the world. The areas have included tumor immunology, microsurgery, minimally invasive surgery, endoscopy, imaging directed surgery, interstitial brachytherapy, stereotactic radiosurgery, functional restoration, molecular and cellular neurosurgery, neuromodulation navigation, vagal stimulation for epilepsy, and now nanotechnology!! All of these initiations and developments studded with remarkable people, places, and events and a bibliography that was 0 when I left Yale cites more than 600 contributions to the literature, including 45 individual published volumes. These opportunities and contributions have been realized by effecting a vigilant, innovative, and opportunistic spirit making the most of each seized chance and maintaining a deep seeded, inveterate persistent modus operandi.

VI. Reinventing Neurosurgery The thirty year period from 1976 to 1986 was a momentous "generation" for neurosurgery and often it seemed that I was standing on "ground zero" for each momentous and seminal event as the new neurosurgery was developed. Work at USC had already focused on microsurgery before my arrival and I immediately became engrossed in its possibilities and nuances with Kurze. We had one of the first operating rooms "designed" for microneurosurgery with an overhead microscope and a fertile relationship with Zeiss, (a leading manufacturer). We worked on new instrumentation, scope sterilization, and application of the new craft. The new capability seemed aptly suited for deep cerebral surgery and the service had a "tradition" of transcallosal surgery with Phil Vogel who had worked at Sperry at Cal Tech in his studies on callosal disconnection. Vogel showed me his transcallosal technique and I decided to apply it to third ventricular midline access; the microscope made the process fluid and the case volume of intreventricular lesions especially cystocercosis at the general hospital gave more than ample opportunity to apply various maneuvers for third ventricular access. We were able to quickly achieve a substantive experience that lent a new dimension to deep cerebral surgery. To augment this, Milton Heifetz, the creative surgical genius was a member of our attending staff. He had acquired a very early set of the then new Hopkins angled endoscope from Storz. Milt asked me if I had any use for them. We went to work immediately. First in the laboratory and then in the clinical setting–applying endoscopy to interventricular situations, aneurysm surgery, transsphenoidal procedures, and spinal surgeries–it was 1977 and a new era in neurosurgery was born. Incidentally, one of my greatest fascinations on submarine duty was the opportunity to use the periscope–the parallel to endoscopy was obvious. During the same period, I was intellectually compelled to make contact with the Jet Propulsion Laboratory (JPL), NASA's center for robotic space exploration. At the time, the Viking Project for a Mars Landing was underway. I used a few connections through the Navy to get access and began to discuss neurosurgical issues with influential people at the Lab. They were anxious to establish parallel relationships with potential "spin off" applications of their technologies. I was welcomed and began to make transits between Cape Canaveral, Florida, NASA's principal launch site, and Los Angeles, gaining an

Ein Helden Leben: A Life in Neurosurgery

15

intimate view of the entire program and using Mars surface analysis technologies to create and assess "finger-prints" of various brain tumors. The experience proved to be a valuable catalyst for innovation related to concepts of miniaturization and surgical minimalism as well as opening doors at the California Institute of Technology for future research efforts. Most importantly, was a primer for creative thought and a desire for large scale enterprise! With the advent of CT scanning a new realm of opportunities opened for us in neurosurgery. We now had maps of some accuracy to follow and I was determined to take advantage of them. The department of Radiation/Oncology at USC had an active radiobrachytherapy program using Iridium 192 (Ir-192) for sarcomas, gynecological, rectal and various head and neck tumors. Fred George, a former Navy Captain, was chairman and constantly looking for new ideas and applications of technology. We had an immediate "meeting of minds." As the first Hospital based CT scanner in Los Angeles was 25 feet from my office in the General Hospital, it was natural that we would begin to make some efforts to establish in primitive fashion operative application of the new technology. I began to create a program of free hand placement of catheters in brain tumors that were later afterloaded with Ir192. This was an initial step toward stereotactic radiosurgery and none of us had any idea of what we were getting into. However, it was not an ideal first step. I knew we had to create an instrument that would allow stereotactically refined placement of sources–in an operating room. In 1977 at a ski meeting in Alta, Utah, I found it a plastic prototype of what would eventually become the Brown/Roberst/Wells Steretotactic System (Figure 4). I "stalked" Trent Wells, the brilliant engineer/designer/machinist who helped to create the Todd/Wells frame more than a decade before had designed the device. He did not initially receive me with open arms but he listened to my ideas and spoke with Ed Todd later. Edwin Todd, a true Renaissance man with a doctorate in Renaissance History, had spent time in John Fulton's Laboratory at Yale and had been very paternal to me from the time of my arrival in Los Angeles. He endorsed me to Trent and Trent in turn introduced me to Ted Roberts, then Chairman of Neurosurgery at the University of Utah. Ted had financed the frame project. Ted and I had immediate positive chemistry. He was a neurosurgeon and pediatric specialist, ever an intellect and true gentleman. Highly collegial, he welcomed an amalgam with USC with me as a principle investigator on his prototype instrument. The instrument was being fabricated at Trent Wells's machine shop in Southgate, California-–only 10 miles from the General Hospital. We were given prototype Number one, with two going to University of Utah and

Fig. 4 Original plastic conceptual prototype of the BRW stereotactic instrument, 1978. Note the novel "N" configuration of localization in Cartesian space through secondary algorithms–the seminal concept in imagingdirected stereotactic neurosurgery. 1978

16 Introduction three to David Thomas at Queen's Square, London. We quickly went to work on "watermelon phantoms" and did our first human case–one of the world's first–of imaging directed stereotactic surgery in the fifth floor neurological operating room at the Los Angeles County General Hospital in 1978 on a 60-year-old man with B-cell lymphoma. This point biopsy was a seminal moment for all of imaging directed stereotactic surgery including navigation and radiosurgery over the next thirty years. The base algorithm, principles, and hardware were proven in humans with that case. I should add that a number of other investigators, notably in France, Sweden, and Germany, simultaneously were exploring similar concepts and devices. However, this gave impetus to a new era in stereotactic neurosurgery and a cascade of applications which are now in operation. We immediately initiated a complex radiobrachitherapy program that reached its highest sophistication in 1984 when it was replaced by radiosurgery. By 1981, I had begun to be interested in Leksell's work in Stockholm and although a gamma knife was not available, I thought that linear accelerators were an obvious choice for a number of reasons to act as a delivery unit for energy. I spoke with the investigators in Italy and Spain who had created primitive linear accelerator radiosurgery systems and related the concepts to Zbignew Petrovich an intellectual activist who had assumed the chair in Radiation Oncology at USC. He was supportive. Colleagues at Boston's Joint Center were working on a similar project and Trent Wells was providing the hardware. Trent and I went to work as did Gary Luxton, our radiation physicist. Quickly, the first radiosurgery on a human was performed by us at the Norris Cancer Hospital in 1984–the rest is history. We went on to acquire Gamma Knifes in 1994, 2001, and 2008. Also, we played an important role in the development of the Cyberknife, installing one of the initial prototype units at USC in 2002. We played an essential role in popularizing the concept and refining its application over a 24 year period–a remarkable source of satisfaction as the method has taken its place as one of the essential features of the neurosurgical armamentarium. Other than radiosurgery we were fortunate because of our industry ties to be central on the development of "frameless" navigation systems, another methodology thhat has revolutionized our discipline. The concept of functional restoration with cellular substrates was introduced in the late 1980's with adrenal medullary autografts for Parkinson's disease; because of our experience, reputation, and resources we were central in the exploration of the concept. Although it was immediately successful, it served as a catalyst for an impending stage of cellular therapies with stem cells and the employment of factors through our new ally nanotechnology. We helped to establish and coined the terms neurorestoration, cellular, and molecular neurosurgery! These are only a few of the seminal involvements that we were privileged to experience involvement with. Oh yes, the prototype ultrasonic aspirator (CUSA) was clinically proven at USC and New York University in 1977!!!

VII. The Power of the Pen There is no doubt that there is power in the pen!! Perhaps no greater contribution to

Ein Helden Leben: A Life in Neurosurgery

17

our field can be accessible to each of us than a contribution to the literature of our time and especially the peer reviewed literature of our fine journals. Through my residency, I was nonproductive in this regard in spite of great support and the academic diligence of William Collins and other faculty at Yale. I did develop a great respect for books, writing, and scientific journals but the chance for a contribution seemed virtually inaccessible to me at the time. However, during my period on nuclear submarines I was required to write a meaningful medical thesis to be certified (qualified) as a bona fide submarine and diving medical officer thus earning the right to wear the highly significant "gold dolphin emblem" of a submariner who had truly "earned his spurs!" I decided to address the topic of the "Management of Head Injuries on Nuclear Powered Submarines." I poured myself into the task and over the course of a year produced a meaningful work that drew considerable attention from the Bureau of Naval Medicine. Because of its practical value it was ultimately published by the Navy and distributed to all submarines in service and made a requirement of Submarine Medical training for several decades–a source of great pride to me and a source of confidence and inspiration as well. Still, my ideas and development in writing meaningful manuscripts was very slow in development. I began a very modest case report on an incident of "Pineal Apoplexy" but left my formal training time without a publication. Upon my arrival in Los Angeles, Marty Weiss, some years my senior, took me under his wing getting me involved in laboratory reports at first, later more complex clinical studies, and little by little I began to blossom. Through, my general will and discipline and the fertile environment of Los Angeles, I began to formulate ideas. Papers began to evolve in rapid succession and, surprisingly, my name began to emerge from obscurity. This required nearly a decade of hard work, commitment, and persistence in many difficult circumstances. I was determined to be an academician and to make a contribution to the field. As an associate professor in 1977 things became economically difficult. Because of a malpractice insurance crisis I was unable to work in private practice to augment my meager academic income and I was required to work "shifts" in the fabulously chaotic emergency room of the General Hospital–this is a story in itself–very dramatic but hardly the venue for a budding academic neurosurgeon! However, persistence prevailed and as time passed circumstances improved and opportunities presented themselves among which was a call from Carolyn Brown, book editor for Williams and Wilkins in 1982. W + W was a highly respected medical publishing house–family operated and keen in developing new young "editorial talents." I was asked to prepare a small (250 page) monograph on the third ventricle as I had just published on concept of the interformical third ventricular approach in NEUROSURGERY. I seized this opportunity and with Carolyn's help went on to edit a 900 page classic work that went on to be the best selling monograph in the company's history–a fact that put me "on the map" so to speak as a figure in operative neurosurgery. This served as a catalyst for more literary opportunities and respect. There were a multitude of invitations to speak at major national and international meetings. Ultimately, I would go on to edit a total of 45 volumes to this point, thirteen of which were surgical topical monograms. Thousands of new ideas welled up with travel, observations, and acquaintances. It was a consummate "snow ball effect" with peer reviewed papers being produced, oddly enough, with seeming ease as a barrier were broken. Now more than 600

18 Introduction publications are evident in my bibliography. Perhaps my greatest honor and task has been the stewardship of NEUROSURGERY. Since 1991, it has been a challenging and formidable chore which I assumed with no formal training–however I brought a broad knowledge of the field, energy, honesty, and a passion for the advancement of Neurosurgery--–these are essential elements for the stewardship and ultimate success in the task which grows relentlessly more complex each day. The challenges are unending but the rewards and satisfaction that is attendant have been unmatched in my experience. Involvement with the "power of the pen" is always rewarding, satisfying, and edifying. It is one of the consummate pleasures of neurosurgery and a catalyst for the development of the mind, soul, and person. It is a ticket for the blossoming of the self.

VIII. Internationality and the Flattening of the Neurosurgical World From my youngest days and educational period, I was fascinated by people, countries, and differences. This was fueled by my interests in reading and motion pictures which provided a catalogue of countries and characters. The fire was further stoked by my family and the University setting in New Haven. Later Yale, Boston, and particularly Montreal taught me the importance of understanding race, nationality, the joy of various contributions to the experience of human existence. I have then always been a student and advocate of internationalism and exchange at that level. In 1988 an unusual opportunity came forward. I was scientific chair of the American Association of Neurological Surgeons Annual Meeting. The large North American meeting, although not overtly biased, were largely characterized by North American ideas and individuals in podium sessions. International presence was minimal with the exception of the occasional "glitterati" from abroad. We decided to augment and showcase the New Orleans Meeting (1989) with an accentuated international flavor–a radical step at the time. There was resistance but David Kelly, president, and James Robertson, president-elect, endorsed the idea. It proved to be a unique success and be a turning point. The 1990 Meeting San Francisco was enormous given the emphasis on internationalism in 1989 and set new records in meeting attendance. The theme has been replayed repeatedly in subsequent years. Jet travel and the internet proved to be strong catalysts for the exchange of ideas and I invested immense amounts of energy in those regards. In 1991, I was asked to assume the Editorship of NEUROSURGERY. Immediately, I established an expanded international advisory board which played and continues to play a major role in the journal's function. Now more than 50% of all submissions and published manuscripts are from outside of the United States, 45 countries and 150 international advisors are listed and play an active role on the board. I have advocated increased involvement of the global community in all activities of the journal, Congress, and any organization where I am active. Over the past generation the world of neurosurgery has flattened and I have passionately worked for this to be reality. The availability of high level practice is more widespread and evident than at any time before. Each congress and specialty meeting is more globally representative and through the internet information is readily available,

Ein Helden Leben: A Life in Neurosurgery

19

conveyed by our website Neurosurgery-Online, raising local standards worldwide. NEUROSURGERY, OPERATIVE NEUROSURGERY, and our special supplements have a penetration of 13 MILLION readers worldwide and our podcasts will soon be available in spanish, portugese, mandarin, korean, italian, and german. More work needs to be done but inventive minds and unique personalities have greater access to each other than ever before–and the catalysts for the information and knowledge escalation is internationalism. My particular journey has been highlighted by a myriad of high level professional and personal international relationships that have created great depth and satisfaction in the quest for self development. I suggest a similar effort for all–the rewards are immense!

IX. Lessons Learned The neurosurgeon's life and the process of truly becoming a neurosurgeon is hardly simple. Each individual cuts their own path. This is the reality and beauty of it. However, for me to approach the issue in more concrete and direct terms, I would make the following suggestions after four decades of struggling within this unique area: 1) 2) 3) 4) 5) 6) 7)

Set distinct, long-term, lofty goals - one can't aim too high Set your standards high Have courage. There is no real loss in occasional failure There is no need to conform Be patient and satisfied with small rewards and steps all will add up Aggressively explore every opportunity Enjoy the process - most of all it a fabulous experience!

Enjoy the journey of a "hero's life" as a neurosurgeon–few have the opportunity!

Works Cited: 1. Apuzzo ML: A fantastic voyage: A personal perspective on involvement in the development of modern stereotactic and functional neurosurgery (1974-2004). Neurosurgery 56:1115-1133, 2005 2. http://www.uscneurosurgery.com/faculty_folder/apuzzo.html, Accessed 7-16-08

20

Towards a better future in profession and life for women neurosurgeons-and their patients YOKO KATO Dept. of Neurosurgery, Fujita Health University, Japan Key words: neurosurgery, neurosurgeon, women, professional Almost 30 years ago, women rarely chose surgery as a profession. Even in 1978 when I graduated, 7 or 8 women out of a 100 student group, kept away from surgery, which was considered to be too intense and heavy. They tended to choose ophthalmology, otolaryngology, or pediatrics. At that time, without a doubt, there were many female doctors who were especially interested in surgery, as they were efficient and skillfull. However, they didn’t know anyone who had managed family, children and housework all together, being primarily a doctor, not even thinking of becoming a neurosurgeon. There was not enough social environment and confidence built to undertake such a career at that time. However, time passes rapidly, and now the percentage of female students and female doctors in Europe approaches 70-80%. There are more women-neurosurgeons nowadays, but still female interns tend to avoid tough specialties, and surgery is given a cold shoulder. A national survey of women surgeons in Canada1) was undertaken to evaluate their ability to combine career with personal and family care. A 93 item questionnaire was mailed in July 1990 to 459 female surgeons. Most surgeons were married. Only 6.5% were separated or divorced. 70% of them had at least one child. The most common surgical specialty was obstetrics and gynecology. Women surgeons practicing in Canada were able to combine productive careers with rewarding family lives and were satisfied with their decision to do so despite the compromises involved. Medical science has been dominated by men 2). There are still very few women researchers in medical science. This science should be developed by both male and female researchers if it is to be equally fair and offer good medical service to female and male patients. Thus, gender neutrality in medical research is most desirable. Sandrick3) has given her comments of the residency experience: the woman’s perspectives in the journal Bull Am Coll Surg. She comments that every surgeons has to go through residency with its long hours, the heavy case loads, the three-in-the-morning emergencies, the probing questions on rounds, the snatches of sleep in the on-call room, and the physical and emotional rigors of the OR. Many surgeons characterize residency training as brutal, uncompromising, even harassing; it is no different for men or women. Female neurosurgeons in Japan comprise only 3% of total number of neurosurgeons in Japan, while the total number of female doctors will hopefully reach 30% of the total Japanese doctors by the end of 2015. However, the present work environment of female

Towards a better future in profession and life for women neurosurgeons-and their patients

21

neurosurgeons is not so good. The recent tendency amongst the younger generation is to enjoy life and thus to avoid selecting such professions where there is lot of dedication and hard work demanded, besides a long residency program. The present generation of female doctors does not want to take up surgical fields, especially the cardiac and neurosurgical fields of surgery where maximum work load and tension exist in the profession. It is the previous generation who still have to struggle to maintain their positions and to progress ahead of their male counterparts. The social scenario for and aspiring young female doctor to become a professional neurosurgeon in any institution is not favorable. Hence, a basic solution lies in making social romance has prevented female neurosurgeons from progressing and proceeding a step ahead of male neurosurgeons in both the research field and clinical practice. The male chauvinistic thinking of females being a weaker sex, whose only role in society is to bear and rear a baby is an absolute misconception. We see achiever women in all walks of life, topping their fields of interest, but the situation is not the same for female neurosurgeons as hardly ever do we see a lady neurosurgeon being the president of any neurosurgical institution or a neurosurgical conference. Recently there were a series of medical reforms that drastically changed the medical system of education and practice. Increased monitoring and control of responsibility in medical practice and higher interest toward the QOL (Quality of life)among the patients and general public, has shifted the frontline forward. Achievement in the treatment of certain illnesses is considered a significant QOL improvement. In this new environment, in which female doctors, account for nearly 40% of all doctors in Japan, have to work. Neurosurgery has aspects that will keep young aspiring physicians away from it: long working hours and many emergencies, and thus increasing numbers of female doctors may therefore stay away from neurosurgery. There is no maternity leave in Europe and this states that environment has been arranged for female doctors. I hope that Japan will be the same way like Europe someday. There are currently 369 female neurosurgeons in Japan. As the numbers of female doctors is growing, we are facing lots of problems in neurosurgery. We have just established a “Women doctors’ bank” and I hope this will give us some kind of solutions. Regardless of the mixed responses, pregnancy, delivery and child raising, family problems, inconvenient working time and discriminatioin have been clearly found. That is the main concern at choosing residency too. The need for social, financial and educational support has been outlined as a recommendation to the institutions regulating the health care labor force. The implementation of a reform is very important and may help the currently practicing women neurosurgeons, however, increasing their number is a process that will be the result of the active intervention of our organizations and supporters to all levels of social interaction-at national, governmental, academic, NGO, informal groups, through media, family support and education, educational institutions. We are certain that the evolution of the Japanese society we are witnessing now will provide the highly qualified professionals-women the place they derserve. I am having a hard time trying to envisage how neurosurgery will look in the future and how can I, personally, contribute. Let me talk a little bit about myself- I received enthusiastic congratulations from the media when in April 2006 I became the first

22 Introduction female Japanese Professor in 60 years of neurosurgery, considered as a very male dominated field of surgery. Neurosurgery has numerous charms and thrills. This is the only branch where you can get actively in contact with living brain, and I am quite sure this is one of the medical specialties where you are constantly able to refine your skills, as if there is a mistake it can lead to disastrous results. Therefore, it was considered a “scared” area in medicine. However, it also means it is stressful, with long hours of surgery, with dedicated care for the patient for prolonged periods, making it a difficult specialty to choose for a woman. As in the proverb “We tend to be good at those things we like,” the first priority in choosing your specialty is that you must love it to make it a life-long work. As for myself, I love neurosurgery and this is why I have chosen it. I can not remember regretting my passion toward it because of the hard work. My desire to complete it as my life-long treasure was always bigger than my worries. On the other hand, you may think it would be physically easier in the specialties, such as dermatology or internal medicine. That, however, totally depends on how you live and how much you are dedicated to your medical professional role and what are you trying to accomplish in medicine. If you think that way, there is no easy choice. At any department of surgery, operations are the daily routine, but in medicine the personal psychological contact with the patients and the beginning I found some families stating they did not like female doctors, but as I built up my confidence after each case, these minute issues became less and less important to me. I felt very strongly that once I built up relations of trust and personal contact with patients, everything should be fine. Now in the age of less invasive treatment, neurosurgery will see significant changes in treatment methods. But the important thing is to have the spirit of a surgeons and improve your skills, and this is something that should not ever change as time goes by. As said in the old days, “Once in doubt, go for it,” if you are hesitating, take the challenge, and if any young female doctors have this spirit, step in and go for neurosurgery. If you can pursue that endeavor for the rest of your life or not, depends on your own determination and spirit, and if you are brave enough, people around you will accept you, approve you, and help you improve. When you have those hours of fatigue and desperation, stop for a while and rest, and then start again, to make your dream come true with each step forward you make. If you like neurosurgery, take it seriously, do not hesitate, and take the challenge, and think of it as your future.

REFERENCES 1. Mizgala C, Mackinnon S, Walters B, Ferris LE. Women Surgeons. The results of the Canadian population Study. Ann Surg 1993; 218: 37-46 2. Enker IC, Schwarz K, Enker J. The disproportion of female and male surgeons in cardiothoracic surgery. Thorac Cardiovasc Surg 1999; 47: 131-135 3. Sandrick K. The residency experience: the woman’s perspective. Bull Am Coll Surg 1992; 77: 10-17

Ⅱ. General Principle

24

Anatomical Basis of Skull Base Surgery: Skull Osteology CAROLINA MARTINS1,2, MD, PhD, ALVARO CAMPERO2, MD, ALEXANDRE YASUDA2, MD, PhD, SHIGEYUKI OSAWA2, MD, PhD, LUIZ FELIPE ALENCASTRO2, 3, MD, LUIZ CARLOS DE ALENCASTRO3, MD, PhD, ALBERT RHOTON JR.2, MD 1

Medical School of Pernambuco – IMIP, Recife/Brazil Department of Neurosurgery, University of Florida, Gainesville 3 Hospital Mãe de Deus, Porto Alegre, Brasil 2

Key words: Skull Base Osteology, Microsurgical Anatomy Understanding the osteology of the skull base is a fundamental step in skull base surgery. It allows for accurate topographic location and helps tailoring surgical routes to specific skull base areas. This chapter reviews the osseous anatomy of the skull base, its major divisions and components.

Introduction The skull is divided into cranium and facial skeleton. The cranium, by its turn, is divided into calvarium, which is the domelike superior portion of the cranium, formed by the frontal, parietal and squamous parts of the occipital and temporal bones, and the cranial base. The cranial base has an endocranial surface, which faces the brain and is naturally divided into anterior, middle and posterior fossae (Fig. 1) and an exocranial surface (Fig. 2), which faces the nasal cavity, sinuses, orbits, pharynx, infratemporal fossae and pterygopalatine, parapharyngeal and infrapetrosal spaces. On the endocranial side of the skull base, the border between the anterior and middle fossa is marked the sphenoid ridge, joined medially by the chiasmatic sulcus, and the border between the middle and posterior fossae is formed by the petrous ridges joined by the dorsum sellae and posterior clinoid processes (Fig. 3). On the exocranial side, the anterior and middle fossae are divided by a transverse line, extending through the pterigomaxillary fissures and pterygopalatine fossae at the upper level, and the posterior edge of the alveolar processes of maxilla at a lower level. Medially, this corresponds to the attachment of vomer to the sphenoid bone. The middle and posterior cranial fossae are separated on each side, by a transverse line crossing near the posterior border of vomer-sphenoid junction, foramen lacerum, carotid canal, jugular foramen, styloid process and mastoid tip (Fig. 4).

Anterior Skull Base The anterior endocranial surface is formed by the combination of three bones:

Anatomical Basis of Skull Base Surgery: Skull Osteology

25

frontal, ethmoid and sphenoid (Fig. 5). The orbital plates of the frontal bones form most of the lateral portions of this fossa, contributing to the roof of orbital cavities and giving support to the dura and orbital gyri of the frontal lobe. The medial gap between the orbital plates is filled by the cerebral surface of the ethmoid bone, presenting the crista galli, which gives attachment to the falx and the cribriform plates, which, by its turn, gives support to the olfactory bulbs. The anterior fossa is closed posteriorly by the lesser wings of the sphenoid bone laterally, and the sphenoid body medially. In this way, the medial portion of the anterior fossa is formed by three bones, while the lateral part, which covers the orbit and optic canals, is formed only by two, the orbital plate of frontal bone and the lesser sphenoid wing on each side. On the exocranial side, the lateral portion of the anterior skull base is on the top of the orbit and maxillary sinus. Medially, it corresponds to the sphenoid sinus of sphenoid body and the ethmoid sinuses, on top of the nasal cavity (Fig. 6). In fact, the most posterior portion of the medial exocranial anterior surface is related with the sphenoid, while the medial and anterior thirds are related with the ethmoid bone. The nasal septum, which is formed by vomer and perpendicular plate of ethmoid, divides the nasal cavity along midline, while the lateral plates of the ethmoid bones divide the nasal cavity from each orbit (Fig. 7, 8). Some foramina and grooves connect the endo and exocranial surfaces in this area as the supraorbital grooves, on the superior orbital limits, the ethmoid canals, located along the suture line formed by the frontal and ethmoid bones, the superior orbital fissure between the lesser and greater sphenoidal wings and optic canals, between the anterior and posterior roots of the anterior clinoid processes.

Middle Skull Base The endocranial surface of the middle fossa is formed by the sphenoid and temporal bones. The division between these bones usually is not well seen unless focusing attention to the sphenoid spine, the most posterior prominence of the sphenoid bone, just behind the foramen spinosum and following the petro-sphenoidal and squamoussphenoidal sutures (Fig. 9). The sphenoid contributes to the middle fossa mainly with the lateral parts of its body, the sphenoid crests and the greater wings. The sphenoid crest is the posterior edge of the lesser sphenoid wings. The lesser wings connect across midline through the sphenoid planum. The chiasmatic sulcus is located posterior to the planum. On each side of the chiasmatic sulcus are the endocranial openings of the optic canals. Posteriorly, the chiasmatic sulcus is separated from the sella cavity by the tubercullum sellae. The posterior limit of sellae is comprised by dorsum and posterior clinoid processes, which are the medial boundaries between the middle and posterior cranial fossae (Fig. 10). The largest opening at the greater sphenoid wing is the foramen ovale, which transmits the third trigeminal division and, most of the times, the accessory meningeal artery. Lateral to this opening is the foramen spinosum for the middle meningeal artery. Occasionally there may be an opening medial to foramen ovale: the emissary sphenoid foramen (foramen of Vesalius), which transmits a vein connecting the pterygoid venous plexus and the cavernous sinus and, on occasions, might transmit the accessory

26 General Principle meningeal artery. The lingula is a protrusion of the sphenoid bone located at the junction of body and greater wing. As soon as the carotid artery leaves its canal on the petrous portion of the temporal bone it is embraced by lingula, which holds the artery in place, and allow it to run along the carotid sulcus on each side of sellae. Anteriorly, the carotid artery rests against the optic strut, in close relationship with the anterior clinoid. Lingula gives attachment to the petrolingual ligament that divides the horizontal petrous carotid from vertical cavernous carotid segment (Fig. 11). The endocranial surfaces of the petrous and squamosal parts of the temporal bone also form the middle fossa (Fig. 12, 13). In this area, the greater petrosal nerve runs into the facial hiatus just medial to tensor tympani muscle and lateral to the carotid canal. Next to petrous apex there is the trigeminal impression which houses the trigeminal nerve. Exocranially, the lateral middle fossa is related to the infratemporal, pterygopalatine and infrapetrosal spaces, while the central part is divided into pharyngeal and parapharyngeal spaces by a line passing through the medial pterygoid plate (Fig. 14, 15). The lateral pterygoid plate is the anteromedial boundary of the infratemporal fossa, which is separated from the temporal fossa by the infratemporal crest. The pterigomaxillary and inferior orbital fissures, the alveolar canals, foramen spinosum, ovale and emissary sphenoid foramen open into the infratemporal fossa. The exocranial surface of the temporal bone is comprised between the mandibular fossa, petrous apex and mastoid tip. In the center of this area are the styloid process and the stylomastoid foramen for the facial nerve. From this area two grooves radiate: digastric groove, for the posterior belly of the digastric muscle and the occipital groove for the occipital artery (Fig. 15). The carotid canal is anterior to the jugular foramen and medial to external auditory meatus.

Posterior Skull Base The endocranial surface of the posterior fossa is formed medially by union of the sphenoid and clival portion of occipital bones. Laterally, it is composed by the apposition of mastoid and the posterior surface of petrous portion of temporal bone with the condylar and basal portions of the occipital bone (Fig. 16). The occipital bone is the major osseous component of the posterior fossa. It is formed by a squamosal, condylar and basal parts. The basal part fuses with the sphenoid to form clivus. Laterally, it articulates with the temporal bone at the petroclival fissures. The squamosal part forms the posterior boundary of the fossa and presents three angles. The superior angle fills the gap between the parietals along the lambdoid suture. The lateral, paired angles mark the most lateral extension of the lambdoid sutures and the ending point of the transverse sinus. It joins the occipitomastoid and parietomastoid sutures at asterion, an important surgical landmark for posterior fossa craniotomies. The condylar part of the occipital bone forms a bridge between the squamosal and basal parts (Fig. 17 & 18). The posterior surface of the petrous portion of the temporal bone presents a medial area, containing the sulcus for the inferior petrosal sinus and a lateral area comprising the jugular fossa and sulcus for the sigmoid sinus (Fig. 19). In the articulated skull, the jugular fossa of temporal bone faces the jugular area of occipital bone, while the anterior angle of occipital bone, located at the quadrilateral plate of the jugular process adapts to the temporal bone lateral to the jugular fossa (Fig. 20 & 21), in

Anatomical Basis of Skull Base Surgery: Skull Osteology

27

such a way that the jugular process of the occipital bone forms the posterior lip of the jugular foramen. The occipital condyles are located on the exocranial surface of the condylar part of the occipital bone (Fig. 22 & 23). In this area, basion is the midline point at the anterior arch of foramen magnum, while the opisthion is the midline point at the posterior arch the foramen. If the basion is considered 12:00 o’clock and opisthion 06:00 o’clock, the occipital condyles can be projected in a position between 1-3 and 9-11:00 o’clock. Posteriorly, on top of the condyles are the supracondylar fossae, which house the posterior opening of the posterior condylar canals. These canals transmit the posterior condylar veins, which connect the vertebral venous plexus to the jugular bulb. The anterior condylar veins, also called hypoglossal veins, course through the hypoglossal canals. The exocranial surface of the squamosal part of the occipital bone is marked by five lines arranged around the external occipital protuberance (Fig. 23). Four of these are transverse lines. The supreme nuchal lines are the highest ones, and give attachment to the occipital aponeurosis. The superior nuchal line is just inferior to the previous ones. From medial to lateral, it gives attachment to trapezius, splenius capiti and sternocleidomastoid muscles. The vertical, unpaired line that radiates vertically from the external occipital protuberance is the external occipital crest. It affords attachment to the ligamentum nuchae and from its midpoint arise the inferior nuchal lines, which give attachment to the superior oblique and rectus capitis posterior muscles.

28 General Principle

Fig. 1-4 1. Cranial base: endocranial surface. 2. Cranial base: exocranial surface. The upper surface of the anterior cranial base is formed by the frontal bone, which roofs the orbit, the ethmoid bone, which is interposed between the frontal bones and is the site of the cribriform plate; and the lesser wing and the anterior part of the body of the sphenoid, which forms the posterior part of the floor of the anterior fossa. The upper surface of the middle cranial base floor is formed by the greater sphenoid wing and posterior two thirds of the sphenoid body anteriorly and the upper surface of the temporal bone, posteriorly. The posterior part of the cranial base is formed by the temporal and occipital bones. The exocranial surface is formed by the maxilla, the zygoma, palatine, sphenoid, temporal and occipital bones

Anatomical Basis of Skull Base Surgery: Skull Osteology

29

and vomer. The maxilla, orbits and the nasal cavity are located below the anterior fossa. The anterior part of the hard palate is formed by the maxilla and the posterior part is formed by the palatine bone. The anterior part of the zygomatic arch is formed by the zygoma and the posterior part, by the squamosal part of the temporal bone. The mandibular fossa is located below the posterior part of the middle fossa. The vomer attaches to the lower part of the body of the sphenoid and forms the posterior part of the nasal septum. The infratemporal fossa is located below the greater sphenoid wing and is limited anteriorly by the infratemporal crest. 3. On the endocranial side of the skull base, the limit between the anterior and middle fossa is marked the sphenoid ridge, joined medially by the chiasmatic sulcus (dotted light blue line), and the limit between the middle and posterior fossae is formed by the petrous ridges joined by the dorsum sellae and posterior clinoid processes (dotted dark blue line). 4. On the exocranial side, the anterior and middle fossae are divided by a transverse line, extending through the pterigomaxilary fissures and pterygopalatine fossae at the upper level, and the posterior edge of the alveolar processes of maxilla at a lower level. Medially, this corresponds to the attachment of vomer to the sphenoid bone (dotted light blue line). The middle and posterior cranial fossae are separated on each side, by a transverse line crossing near the posterior border of vomer-sphenoid junction, foramen lacerum, carotid canal, jugular foramen, styloid process and mastoid tip (dotted dark blue line).

Fig. 5-8 5. The frontal ethmoid and sphenoid bones combine to form the anterior fossa, which is divided into medial and lateral portions. The medial part, covering the upper nasal cavity and sphenoid sinus, is

30 General Principle formed by the crista galli and the cribriform plate of the ethmoid bone anteriorly and the planum of the sphenoid body posteriorly. The lateral part, which covers the orbit and the optic canal, is formed by the frontal bone and the lesser wing of the sphenoid bone, which blends medially into the anterior clinoid processes and point towards the middle fossa. 6. On the exocranial side, the anterior cranial base is divided into a medial part related to the ethmoidal and sphenoidal sinuses and nasal cavity below, and a lateral part that corresponds to the orbit and maxilla. The ethmoid bone forms the anterior and middle thirds of the exocranial surface and the sphenoid body forms the posterior third of the medial part. The ethmoid presents the perpendicular plate that joins the vomer in forming the nasal septum and two lateral plates located in the medial wall of the orbits. The lateral plates separate the lateral wall of the nasal cavity and the orbit. The main foramina of the region are the anterior and posterior ethmoidal foramina located in the superomedial orbital wall, along the frontoethmoidal suture, which transmit the ethmoidal nerves and arteries, the supraorbital and supratrochlear notches or foramina, transmitting the arteries and nerves of the same name, and the optic canal which transmits the optic nerve and ophthalmic artery. The superior orbital fissure is located between the lesser and greater sphenoidal wings on the lateral side of the optic canal. It transmits the oculomotor, trochlear, ophthalmic, and abducens nerves, a recurrent meningeal artery, and the superior and inferior ophthalmic veins. 7. The osseous nasal septum is formed by the attachment of the perpendicular ethmoid plate and vomer at the sphenoidal crest. 8. Anterior norma. The orbital rim is formed by the frontal bone, zygoma and maxilla. The nasal bone is interposed above the anterior nasal aperture, between the maxillae. The nasal cavity is located between the ethmoid bone above and the maxillae, palatine bones, and sphenoid pterygoid process below. It is roofed by the frontal and ethmoid bones and the floor is formed by the maxillae and palatal bones. The nasal septum forms the medial walls of the nasal cavities. The nasal conchae are located on the lateral walls of the nasal cavity. The inferior concha (insert) is a separate bone, and the middle and superior concha are appendages of the ethmoid bone.

Anatomical Basis of Skull Base Surgery: Skull Osteology

31

Fig. 9-13 9. The endocranial surface of the middle cranial base is formed by the sphenoid and temporal bones and can be divided into three regions: a medial part, the sellar region (blue shaded area), formed by the sphenoid body; a lateral part, the temporal fossa (pink shaded area), formed by the sphenoidal wings and the cerebral surface of the squamosal and petrous parts of the temporal bone, and an intermediate part, the parasellar area (yellow shaded area), formed by the transitional part of the sphenoid bone between the greater wing and body, and receiving posteriorly a small contribution of the petrous apex of the temporal bone. The greater wing forms the largest part of the endocranial surface of the middle fossa, with the squamosal and the petrosal parts of the temporal bone completing this surface. 10. Enlarged view of the medial part of the middle fossa. The medial part of middle fossa is formed by the body of the sphenoid bone. 11. Lateral view of the parasselar region. The course of the petrous, cavernous and supraclinoid carotid have been represented. The cavernous sinus sits on the lateral aspect of the body of the sphenoid bone. The carotid sulcus is the shallow groove on the lateral aspect of the body of the sphenoid bone along which the cavernous carotid courses. The cavernous carotid sits against and is separated from the carotid sulcus by the dura of the medial sinus wall. The carotid sulcus begins inferior and lateral to the dorsum sellae at the intracranial end of the carotid canal, turns forward to groove the body of the sphenoid immediately below the lateral edge of the floor of the sella, and turns upward to end medial to the anterior clinoid process. 12. The upper surface of the petrous bone is grooved along the course of the greater and lesser petrosal nerves. The lesser petrosal nerve from the tympanic plexus passes through the tympanic canaliculus, which is located anterior to the facial hiatus and courses in an anteromedial direction parallel to the greater petrosal nerve, which courses along the facial hiatus. The carotid canal extends upward and medially and provides passage to the internal carotid artery and carotid sympathetic nerves in their course to the cavernous sinus. The posterior trigeminal root reaches the middle fossa and, at the trigeminal impression, on the upper surface of the petrous bone, are located Meckel’s cave and the semilunar ganglion. The arcuate eminence approximates the position of the semicircular canals. The internal auditory canal can be identified below the floor of the middle fossa by drilling along a line approximately 60 degrees medial to the arcuate eminence, near the middle portion of the angle between the greater petrosal nerve and arcuate eminence. The petrous apex, medial to the internal acoustic meatus, is free of important structures. A thin lamina of bone, the

32 General Principle tegmen tympani, extends laterally from the arcuate eminence and roofs the mastoid antrum and tympanic cavities and the canal for the tensor tympani. Opening the tegmen from above exposes the heads of the malleus, incus, the tympanic segment of the facial nerve, and the superior and lateral semicircular canals. 13. The anterior surface of the temporal bone has been drilled to expose the internal structure of the temporal bone. The carotid artery is represented in red, the facial nerve in yellow, the cochlear nerve in black and the vestibular nerves in green. The arcuate eminence approximates the position of the superior semicircular canal; however, the relationship between these two structures is greater at their anterior end, from which their main axis diverge. From the brainstem to its peripheral branches, the facial nerve can be divided into six portions: cisternal, meatal (a), labyrinthine, tympanic, mastoid (c) and extracranial. The labyrinthine segment, which is located in the petrous part, extends from the meatal fundus to the geniculate ganglion and is situated between the cochlea anteromedially and the semicircular canals posterolaterally. The labyrinthine segment ends at the site at which the greater superficial petrosal nerve arises from the facial nerve at the level of the geniculate ganglion. From there, the nerve turns laterally and posteriorly along the medial surface of the tympanic cavity, thus giving the name tympanic segment to that part of the nerve. The tympanic segment runs between the lateral semicircular canal above and the oval window below. As the nerve passes below the midpoint of the lateral semicircular canal, it turns vertically downward and courses through the petrous part adjacent to the mastoid part of the temporal bone; thus the third segment, which ends at the stylomastoid foramen, is called the mastoid or vertical segment. Into the temporal bone the facial nerve gives off the greater petrosal (e) and chorda tympani nerves (f). The corda tympani nerve, which arises from the mastoid part, runs upwards, passes along the roof of the tympanic cavity and exits the cavity through the anterior canaliculus. The greater petrosal nerve runs initially along the facial hiatus runs beneath the dura of the middle fossa, reaches the sphenopetrosal groove formed by the junction of the petrous and sphenoid bones, immediately superior and anterolateral to the horizontal segment of the petrous carotid and joins the sympathetic carotid nerves to help forming the vidian nerve into the pterygoid canal. The cochlea lies below the floor of the middle fossa in the angle between the labyrinthine segment of the facial nerve and the greater petrosal nerve, just medial to the geniculate ganglion, anterior to the fundus of the internal acoustic meatus, and posterosuperior to the lateral genu of the petrous carotid artery.

Anatomical Basis of Skull Base Surgery: Skull Osteology

33

Fig. 14-15 The exocranial surface of the middle cranial base is also divided into medial (blue shaded area), intermediate (yellow shaded area) and lateral (pink shaded area) parts. The medial part encompasses the sphenoid body and the upper portion of the basal (clival) part of the occipital bone and corresponds to the sphenoid sinus and the nasopharynx. The lateral part is formed by the greater sphenoid wing, the petrous, tympanic, and squamous and styloid parts of the temporal bone and the zygomatic, palatine, and maxillary bones. The intermediate part corresponds to the area comprised between the pterygoid plates, encompassing the area inferior to the cavernous sinuses, which extend from the pterygopalatine fossa in front to the pterygoid fossa posteriorly. 15. Temporal bone. Exocranial surface.The temporal bone is divided into squamosal, petrous, mastoid, tympanic, and styloid parts. The tympanic and squamosal parts, which form the roof of the mandibular fossa, are located anteriorly to the styloid part, the mastoid part is postero-lateral, radially grooved by the occipital groove and mastoid notch, and the petrous part is located medial to the styloid part.

Fig. 16-19 16. The posterior cranial base is formed by three bones: sphenoid, temporal and occipital bones. The posterior fossa can be divided into medial and lateral portions. Medially, the sphenoid and the basal (clival) portion of occipital bone fuse at the sphenoclival syncondrosis. Laterally, the posterior fossa is composed by the apposition of mastoid and posterior surface of petrous portion of temporal bone with condylar and basal portions of the occipital bone. The occippital bone is the main component of the posterior cranial fossa. It has three parts, clival, condylar and squamosal; three borders, petrous, mastoid and parietal and three angles: paired, anterior and lateral angles, and an unpaired, superior angle. The anterior angle marks the combination of the different parts of temporal and occipital bones: medial to the anterior angle, the petrous border meets the petrosal part of the temporal bone at the petroclival fissure, and the jugular fossa of the temporal bone combines with the jugular notch of the occipital bone to form the jugular foramen. Lateral to the anterior angle, the mastoid border meets the mastoid part of the temporal bone to form the occipitomastoid suture. The parietal border, between the lateral and superior angle, combines with the parietal bone forming the lambdoid suture. 17. Superior view of the endocranial side of the condylar and basal (clival) parts of the occipital bone. The condylar part can be considered a bridge connecting the clival and squamosal parts of the occipital bone. The clival part is concave from side do side and present the sulcus for the inferior petrosal

34 General Principle sinus. The inferior petrosal sinus links the cavernous sinus to the medial part of the jugular foramen. On the exocranial side, there is a similar sulcus for the inferior petrosal vein. The condylar part comprises a quadrilateral plate of bone, the jugular process, whose anterior border presents the jugular notch and the anterior angle of the occipital bone. Medial to the jugular notch, on the endocranial surface is the jugular tubercle, a protrusion related to the course of the lower cranial nerves. 18. Exocranial surface of the condylar part of the occipital bone. The jugular notch is located superolateral to the hypoglossal canal and occipital condyle. On its posterior wall there is the opening of the posterior condylar canal, which transmits an emissary bvein connecting the vertebral plexus to the sigmoid sinus. The hypoglossal canal can be divided by a fibrous or a bony septum. 19. The posterior surface of the temporal bone forms the anterolateral limit of the posterior fossa. It extends from the petrous apex medially to the sigmoid sulcus laterally and from the sulcus for the superior petrosal sinus and petrous ridge superiorly, to the sulcus for the inferior petrosal sinus and jugular fossa inferiorly. The nerves passing through the internal acoustic meatus have been represented with colored material: the facial nerve (yellow) is located anterosuperior, the cochlear nerve (black) is anteroinferior, and the vestibular nerves are located posterolaterally. The petrous carotid (red) is represented in the carotid canal.

Anatomical Basis of Skull Base Surgery: Skull Osteology

35

Fig. 20-23 20. Petroclival area. The combination of the basal (clival) part of the occipital bone and petrosal part of the temporal forms the petroclival fissure. The combination of the jugular notch of the occipital bone and the jugular fossa of the temporal forms the jugular foramen. The intrajugular processes of the temporal and occipital bones project into the jugular foramen and divide this area into petrosal and sigmoid parts. The intrajugular process of the temporal bone is usually more prominent. 21. Arrangement of parietal, temporal and occipital bones on the right side of the skull. Lateral to the jugular foramen, the mastoid border of the occipital bone meets the mastoid part of the temporal bone, forming the occipitomastoid suture. The parietal bone meets the mastoid part of the temporal at the parietomastoid fissure and the parietal border of the occipital bone combines with the parietal bone at the parieto-occipital or lambdoid suture. The meeting point of the occipitomastoid, parietomastoid and lambdoid sutures forms the asterion. The asterion is related to the lateral angle of the occipital bone and marks the transition between the transverse and sigmoid sinuses at the most lateral part of the posterior cranial fossa. 22. The occipital bone surrounds the foramen magnum. The occipital bone is divided into a squamosal part located above and behind the foramen magnum, a basal (clival) part situated in front of the foramen magnum, and paired condylar parts, located lateral to the foramen magnum. Basion is the most anterior part of the anterior edge of foramen magnum. Opisthion is the most posterior point along the posterior edge of foramen magnum. 23. Exocranial surface of squamosal part of the occipital bone.The exocranial surface is marked by four paired transverse ridges and one vertical crest that radiate from the external occipital protuberance. The supreme nuchal lines are the highest ones, and give attachment to the occipital aponeurosis. The superior nuchal lines are just inferior to the previous ones, and usually more marked. From medial to lateral, they give attachment to trapezius, splenius capiti and sternocleidomastoid muscles. The superior nuchal lines have a transverse part, close to the external occipital protuberance. Laterally, close to the mastoid, they describe an arched course, related to the mastoid emissary foramina. The transverse part of the superior nuchal line marks externally the position of the transverse sinuses and the transition between the supratentorial and infratentorial compartments. The external occipital crest radiates vertically from the external occipital protuberance close to midline. It affords attachment to the ligamentum nuchae. From the midpoint of the external occipital crest, an arched paired ridge, the inferior nuchal line radiates, just above the posterior edge of foramen magnum. The inferior nuchal line on each side gives attachment to the superior oblique and rectus capitis posterior major and minor. The occipital bones sit over the cervical atlas adapting the convex occipital condyles adapt to the concavity of the lateral masses of atlas and piling on top of the cervical column. Ant.: Anterior, Ac.: Acoustic, Arc.: Arcuate, Can.: Canaliculus, Car.: Carotid, Cav.: Cavity, Chiasm.: Chiasmatic, Clin.: Clinoid, Cond.: Condyle, Condylar, Em.: Emmissary,Emin.: Eminence, Eth.: Ethmoid, Ethmoidal, Eust.: Eustachian, Ext.: External, Fiss.: Fissure, For.: Foramen, Front.: Frontal, Gr.: Greater, Horiz.: Horizontal, Hypogl.: Hypoglossal, Impres: Impression, Inf.: Inferior, Infratemp.: Infratemporal, Int.: Internal, Intrajug.: Intrajugular, Jug.: Jugular, Lat.: Lateral, Less.: Lesser, Mand.: Mandibular, Mast.: Mastoid, Mid.: Middle, Occip.: Occipital, Occipito, Orb.: Orbital, Palat.: Palatine, Par.: Parietal, Pet.: Petrous, Perp.: Perpendicular, Pharyng.: Pharyngeal, Post.: Posterior, Proc.: Process, Pteryg.: Pterygoid, Pterygomax.: Pterygomaxillary, Subarc.: Subarcuate, Sem.: Semicircular, Sphen.: Sphenoid, Sphenoidale, Squam.: Squamous, Squamotymp.: Squamotympanic, Sup.: Superior, Supraorb.: Supraorbital, Surf.: Surface, Sut.: Suture, Supracond.: Supracondylar, Supraorb.: Supraorbital, Sig.: Sygmoid, Stylomast.: Stylomastoid, Temp.: Temporal, Trig.: Trigeminal, Tymp.: Tympanii, Tympanic, Tuberc.: Tubercle, Transv.: Transverse, Vest.: Vestibular, Zyg.: Zygomatic.

REFERENCES 1. Rhoton Al Jr. The posterior cranial fossa. Microsurgical anatomy and surgical approaches. Neurosurgery 47(1):S1-S298, 2000. 2. Rhoton AL Jr. The supratentorial cranial space. Microsurgical anatomy and surgical approaches. Neurosurgery, 51(1):S375-S410, 2002.

36

Neurological Examination JUNKO MATSUYAMA1, ANIL SANGLI2 1

Department of Neurosurgery, Fujita Health University, Aichi, Japan Department of Neurosurgery, Apollo BGS Hospitals, Mysore, India (I, II) Junko Matsuyama, (III~VI) Anil Sangli 2

Key words: neurological examination, cortical function, cranial nerve, motor and sensory Neurological examination is an initial, most essential and critical diagnostic method involved in clinical decision making. It enables the neurosurgeon to decide on further imaging and therapeutic interventions. Neurological examination aims to answer three questions – Is there a lesion?, What is the lesion?-- which tells about the pathology and Where is the lesion?.. which defines the anatomical localization. This sequence of methodology is crucial for the treatment plan, prognosis, understanding the natural history and assists in the management. Careful, meticulous and detailed history taking obtained from the patient, his family members and colleagues along with a proper neurological examination, aids in giving diagnosis in more than 90% of the cases. In this era of superior and accurate diagnostic modalities, neuro-imaging and laboratory tests further helps in confirming the diagnosis and assists in management. The neurological examination begins the moment a patient walks into the clinician’s room. Even before touching the patient, the gait, the demeanor, the behaviour etc., gives a major idea regarding diagnosis. Neurological diseases may have negative manifestations in the form of loss of function like hemi paresis, weakness, memory loss, impaired sensation etc., or positive manifestations like seizures, spasticity, tingling paresthesias etc. Gray matter abnormalities interfere with neuronal cell body and synaptic functions, causing negative or positive abnormalities, whereas white matter lesions involve axonal conduction fibers, causing disconnection syndromes. Combination of signs and symptoms aids in localizing the lesion whether in the brain or the spinal cord. When confounding signs and symptoms suggestive of two or more sites of lesions are encountered, physician should pose the question “Whether a single lesion can account for the abnormalities?”. Several mechanisms like destruction e.g., stroke, parkinsonism, spinal cord injury or compression like a tumor, bleed, ventricular pathway obstruction etc., can cause symptoms. Different processes like a focal pathology e.g., stroke, multifocal pathologies like multiple sclerosis, metastatic tumors, diffuse processes like toxic and metabolic disorders, can cause neurological disease. The temporal profile aids in diagnosis. A recent onset, sudden onset, slow progressive dysfunction, sub-acute progressive dysfunction or a chronic and delayed progression aids in helping diagnosis. The first step in solving a clinical problem is accurate anatomical localization. Cortico spinal tracts descend ipsilaterally upto the spino medullary junction and then cross over

Neurological Examination

37

to the opposite side to descend until they reach the lower motor neuron of that side. The ascending somato sensory tracts named the spino-thalamic tract which carry sensation of pain and temperature and the dorsal column medial leminiscus system which carries discriminatory touch and position sense, have the anatomical localization as follows : 1. Spino-thalamic tract cross immediately upon entering the cord, whereas, dorsal column tracts cross at the level of medulla 2. These two sensory systems reach the rostral pons where they are in close proximity and then ascend to the thalamus and further on to the sensory cortex

I. Examination of the cortical functions Cerebral hemispheres represent the highest and the most complex level of neurological function. This is influenced by mental status and hence the integrated cortical function is divided according to the corresponding divisions of the cerebral hemispheres which are given in the figure. The mental status examination begins with listening to the patient, watching the patient, especially during the history. The assessment of level of alertness and intactness of the reticular activating system is the first step in mental assessment. 1. Frontal lobe A. Motor area - Precentrssal gyrus exists just in front of the central gyrus and in the most posterior part of the frontal lobe. This part plus paracentral lobule which surfaces interhemispheric fissure is called motor area and Brodmann area 4. Function of the motor area is voluntary movement of opposite side of the both upper and lower extremities and face. Premotor area is area 6. This has the arrangement with head in lower part, especially larynx and pharynx being the lowest, feet being upper. (Fig. 1). Pyramidal tract (corticospinal pathway and corticobulbar pathway) arise from this precentral gyrus. 70 to 90% of the pyramidal tract crosses at the lower part of the medulla and forms the lateral corticospinal tract. B. Premotor area -Premotor area is Brodmann’s area 6, which locates just rostral to motor area. The function of the premotor area is controlling motor function, and its arrangement is similar to motor area. Frontopontine fibers that arise from middle frontal gyrus in front of the area 6 and area 8, forms the important part of the corticopontocerebellar tract. If these fibers are affected, frontal ataxia in the opposite side occurs. C. Frontal motor eye field - Area 8 locates just in front of the area 6, and this is the frontal motor eye field which controls conjugate ocular movements. If area 8 is stimulated, very strong, rapid conjugate deviation to the opposite side occurs. D.Motor speech area - The lower part of the motor and premotor area is Brodmann’s area 44 and 45, and that is known as Broca’s area or motor speech center. If this part is disturbed, expressive aphasia (motor aphasia) will occur. Area 46 and 47 are also related. E. Frontal association areas - Brodmann’s area 9,10,11,12,32 locates anterior to area 6,8, and these areas are called prefrontal areas. Prefrontal association areas are related with memory, judge, abstract thinking, emotional control. There are 3 major syndromes when frontal association areas are affected. ① frontal convexity syndrome: When areas 9, 10 are affected, the patient will lack in voluntary activity,

38 General Principle

Fig. 1

and becomes apathetic. Judge, complicated thinking will be affected. ② orbitofrontal syndrome: If frontal lobes which faces to orbital roof is affected, the patients become euphoric, and cannot control emotion. ③ medial frontal syndrome: Disturbance of bilateral cingulated gyrus causes akinetic mutism. 2. Parietal lobe A. Somatosensory area - Brodmann’s areas 3,1,2 are postcentral gyrus which locates behind the central sulcus, and are called somatosensory area or sensory receptive area. If this area is affected, parietal hemianesthesia or hypesthesia on the opposite side of the body will occur, also, sensory extinction, two point discrimination disturbance, graphanesthesia and astereognosis will occur (Fig. 2). B. Right parietal lobe - If right side of the parietal lobe is affected, unilateral spatial neglect, dressing apraxia, hemiasomatognosia, anosognosia for hemiplegia, loss of topographical memory could occur. C. Left parietal lobe - Disorder of left angular gyrus (area 39) causes the famous Gerstmann syndrome which shows finger agnosia, right-left disorientation, acalculia, and agraphia. Other disorders that are caused by affect in left parietal lobe are conduction aphasia, autopagnosia, ideational apraxia & ideomotor apraxia. 3. Occipital lobe - Occipital lobe is composed of area 17 which locates both sides of the calcarine fissure (striate cortex, primary visual area), area 18 and area19. Area 17 is the

Neurological Examination

39

receiving center of the visual stimulation, area 18 receives the stimulation from area 17 and identify and recognize the things. Area 19 has connection between area 17,18 and other brain cortex, and involves in more complex visual recognition, and spatial orientation (Fig. 3). A. Temporal lobe - auditory receptive region (lateral superior part of temporal lobe) Areas 41 and 42 are so called Heschl’s gyrus and exist in the dorsosuperior part of the superior temporal gyrus. These areas have function to recognize sound. So, near

Fig. 2

Fig. 3

40 General Principle this area (posterior part of the superior temporal gyrus) in the left side is area 22 which is called Wernicke area. If area 22 is affected, sensory aphasia will occur. B. Anteromedial part of temporal lobe - Amygdala and hippocampus exist in this area which is important as limbic system. Parahyppocampal area is related to olfactory function. These areas are called emotional brain. Psychomotor seizure or temporal lobe epilepsy is caused by affected anteromedial part of temporal lobe, which shows automatism. C. Posterior medial part of temporal lobe - A part of optic radiation (Meyer’s loop) exists in this part. If this part is affected, quadrantanopsia will occur. D.Kluver- Bucy syndrome - Kluver-Bucy syndrome is caused by resection of bilateral anterior part of temporal lobe (uncus and hippocampus). The symptoms of this syndrome are psychic blindness, visual agnosia, loss of fear and rage reactions, bulimia (abnormal appetite), hypermetamorphosis (overreaction to visual stimulation). 4. Limbic system Hyppocampus gyrus, uncus, isthmus and Cingulate gyrus belong to limbic system. This system is related to thalamus and hypothalamus. If this system, especially mammilary body, hypppocampus gyrus, and occasionally fornix, and medio-dorsal or anterior nucleus of thalamus are affected, Korsakoff syndrome occurs. Korsakoff syndrome is known as recent memory disturbance, disorientation, confabulation. The frontal lobes help in functions of attention, behavior, motivation, working memory, judgment, fund of knowledge, organizing tasks and naming of things etc. Temporal lobes, especially connections between amygdala and hypothalamus, help in emotional response, whereas, hippocampal and limbic connections aid in memory. Receptive language area called Wernicke’s area is situate in the posterior part of superior temporal gyrus of the dominant temporal lobe. The expressive language area called Broca’s area is located in the posterior part of inferior frontal gyrus of the dominant lobe. Homologous regions of the non-dominant hemisphere help in nonverbal contextual emotional and prosody or rhythm of language. Parietal lobe functions help in perception and interpretation of somato-sensory information, wherein, the non-dominant lobe is important for visual-spatial function and the dominant lobe for praxis which is formation of idea of a complex, purposeful motor act. The frontal lobe helps in execution of the act. Occipital lobes help in recognition of faces, color, shape and projections to the superior temporo-parietal area are important for perceiving motion of objects. Orientation and memory is evaluated by asking questions about the day, date, month, place etc., which involves not only memory but also attention and language. Three-word recall tests for temporal lobe and remote memory such as the state’s President and Prime Minister, helps in assessing association cortices. Attention span is evaluated by digit span, spelling backwards and naming months of the year, backwards, which helps in assessment of the working memory, which is a frontal lobe function. Judgment is a frontal lobe function, which is assessed by testing problemsolving, verbal similarities and evaluating proverbs, especially rephrasing proverbs or giving simple consequences of a particular action. Problems with judgment, abstract reasoning and executive function is seen in frontal

Neurological Examination

41

lobe dysfunction. Verbal fluency and ability to generate a set of items like to give 10 or more words in a minute is a frontal lobe function, where, patients with dysfunction abruptly stop after four words. Following commands demonstrate that they understand the meaning of what is heard or read. Evaluation of this function either spoken or written language, evaluates receptive functions. The fluency of expressive language, correctness of content and grammar that requires spontaneous speech, writing, naming, repetition of sentences and reading comprehension is a function of Broca’s area. Performing skilled motor activity without any non-verbal prompting involving the face and limbs must require the patient to have normal comprehension and intact volitional movement. Inability to perform this act is called ‘apraxia’ seen in dominant inferior parietal lobe lesions. Ability to recognize objects (gnosis) perceived by the senses – somato sensory area with the patient’s eyes closed and a familiar object placed on their hand (stereognosis) or numbers written on the hand (graphesthesia) test the parietal lobe sensory perception. Dominant parietal lobe function includes right-left orientation, naming fingers and calculation with simple arithmetic. Dysfunction of this, leads to Gerstmann’s syndrome. Non-dominant parietal lobe function involves visual spatial sensory tasks like attention to contra lateral half of the body and constructional task such as drawing a face, clock or geometric figures. Patient with such dysfunction draws a clock by listing the numbers of the clock in two columns and draws a line between 8 and 3, for 08:15. Visual association areas which is the inferior occipito temporal cortex, helps in recognition of colors and faces. Achromatoxia is inability to distinguish colors and visual agnosia is inability to name or point to a color and prosopagnosia is inability to identify familiar faces.

II. Examination of the Cranial Nerves 1. Olfactory nerve (Nerve I) The first neuron of the olfactory nerve exists in nasal mucosa. The famous syndrome which is caused by anterior cranial fossa tumor is Foster Kennedy syndrome, which reveals anosmia and primary optic atrophy on tumor side and papilledema on the other side. 2. Optic nerve (Nerve II) After optic nerve reaches optic chiasm, half of the optic nerve fibers will cross. Therefore, optic tract is composed of fibers from the same side lateral part and opposite side medial part. After changing the neuron at lateral geniculate body, they format optic radiation and end at occipital visual cortex, area 17. Examination of the Optic Nerve ¡) Visual acuity ™) Visual field; confrontation test, perimetry enables us to find constriction of the visual field, homonymous hemianopsia or quadrant anopsia which is generally caused by cerebrovascular disease in occipital region, bitemporal hemianopsia which is mainly caused by seller or supraseller tumors (pituitary adenomas, craniopharyngiomas, arachnoiditis at optic chiasm). £) opthalmoscopic examination- Opthalmoscopic examination is one of the most important neurological examination to find papiledema, subhyaloid hemorrhage due to subarachnoid hemorrhage and observe the retinal vessels.

42 General Principle

Fig. 4

Fig. 5

Neurological Examination

43

3. Ocular nerves (Nerves III, IV, VI) - It is composed of motor nerve and parasympathetic nerve. Lateral nucleus of Oculomotor Nerve (Nerve III) controls upper, lower, medial rectal muscle of eye ball and inferior oblique muscle. Central nucleus of Perlia controls levator muscle. Edinger-Westphal nucleus controls miosis and accommodation. Trochlear nerve (Nerve IV) - Trochlear nerve is pure motor nerve that controls superior oblique muscle. Trochlear nerve nucleus exists in the lower part of the oculomotor nerve nucleus in midbrain, and it is the only cranial nerve which arise from dorsal part of the brainstem. Abducens nerve(Nerve VI)- Abducens nerve is pure motor nerve which controls lateral rectal muscle of eye ball and locates in the lower pons. Paramedian pontine reticular formation (PPRF) locates just close to this abducens nerve nucleus and stimulates oculomotor nerve via medial longitudinal fasciculus, and coordinates the one side of lateral rectal muscle and other side medial rectal muscle, and make lateral gaze smooth. Examination of Ocular Cranial Nerves Size of the pupil, isocoria or anisocoria, light reflex, accommodation reflex, eyelids, ocular movement, nystagmus are important factors to find brain disease. 4. Trigeminal nerve (Nerve V)-Sensory branch of the trigeminal nerve arise from Gasser ganglion and ends at long sensory nerve nucleus which locates pons, medulla, and upper cervical cord. Motor branch arise from motor nucleus at lateral part of pons, and controls mainly masseter muscle and pterigoid muscles. Examination of Trigeminal Nerve Sensory function of face, oral cavity, tongue, nasal cavity, masseter muscle constriction, jaw reflex or masseter reflex, and corneal reflex. Cerebello-pontine angle tumor, paraseller tumor, Cavernous sinus region, trigeminal neurinoma might cause abnormality. 5. Facial nerve (Nerve VII)-Motor branch arise from motor cortex and goes through genu of internal capsule, medial part of the cerebral peduncle and then goes into the pons and crosses and ends at facial nerve nucleus. Among the inermedius nerve, gustatory branch arises from sensory cell in the geniculate ganglion, joins the chorda tympani and distribute in the anterior tongue. Or goes to fasciculus solitarius nucleus in the medulla and through thalamus, goes to area 43 which is gustatory cortex. Examination of Facial Nerve See the patient if she or he has peripheral or central facial palsy. 6. Vestibulocochlear Nerve (Nerve VIII)- Cochlear nerve (auditory function) Cochlear Nerve arise from hair cells in the cochlear in the internal ear, and ends at cochlear nucleus in the pons, and then through lateral leminiscus, medial geniculate body, and then reaches Heshl areas 41,42, which is auditory cortex. Examinations are interview, test with tuning fork, and audiogram. Distinguish whether the patient got sensorineural hearing impairment or conductive hearing impairment. Vestibular Nerve (equilibrium function)- Arising from vestibular ganglion in semicircular canal and maculae, vestibular nerve goes into lateral medulla where

44 General Principle nucleus Deiters, nucleus Schwalbe, nucleus Bechterew and inferior nucleus exists, connects to medial longitudinal fasciculus, controls eyes, head and neck movement by stimulation to semicircular canal. Vestibulo-spinal system controls muscle tone and posture. Examination of vestibular nerve are stepping test, nystagmus, postural deviation, caloric test. 7. Glossopharyngeal and Vagal nerve (nerve IX and X)- These nerves are composed of motor branch which arise from nucleus ambiguus, sensory branch which arise from petrous ganglion, and autonomic fiber which arise from inferior salivary nucleus. Examination; taste of posterior one third of tongue, pharyngeal or gag reflex, curtain sign in soft palate because of the deviation of the palatal arch, oculocardiac reflex. 8. Spinal accessory nerve (nerve XI)- This nerve is pure motor nerve and controls sternocleidomastoid muscle and trapezius muscle. Examination of this nerve ; To know the function of sternocleidomastoid muscle, hold the patient’s jaw and make patient see the opposite side. 9. Hypoglossal nerve (nerve XII)- This nerve is pure motor nerve which arise from hypoglossal nucleus in medulla, and controls tongue movement. Examination of this nerve is observation of the tongue movement, atrophy of the paretic side, and tongue deviation to the paretic side. Evaluation of the cranial nerves allows the assessment of the brain stem with the midbrain having cranial nerve nuclei 3 and 4, the pons with cranial nerve nuclei 5-8 and medulla oblongata with cranial nerve nuclei 9-12. Except for the 4th nerve, cranial nerves do not cross and clinical findings are always on the same side of the nerve involvement. Evaluation of cranial nerves with the corticospinal and somatosensory tracts helps in accurate localization. Olfaction is tested one nostril at a time by a non-irritating smelling agent. Detection of smell is important than identification of the agent. Visual acuity is assessed by a pocket Rosenbaum Chart or a Snellen chart. Ability to read the smallest letters helps in evaluating the acuity. Visual field examination is tested by holding up both hands superiorly and inferiorly and asking the patient if they can see both hands and whether they are symmetric. Each eye is tested individually using fingers in all four quadrants of the visual field and asking patient to count fingers. Focusing on a dot in the center of a grid card and asking the patient whether any part of the grid is missing, is another method. Testing one eye at a time and asking the patient to say ‘yes’ as soon as they see a bright object coming into the side of the vision while the patient focuses on the examiner’s nose, is the third method. Formal perimetry is more accurate than screening test. Direct visualizationof the optic nerve head to assess the disc, vessels, fovea and the background retina is a part of fundoscopy. Loss of venous pulsation, swelling of the optic nerve head, venous engorgement, disc hyperemia, obliteration of the optic cup and flame-shaped hemorrhages are stages in papilledema. Complete pallor of the optic disc indicates complete damage to optic nerve, either due to ischemia, pressure or demyelineation. Assessment of pupiliary reflex both direct and consensual, by flashing a light on each eye,

Neurological Examination

45

evaluates the papillary light reflex. Marcus Gunn Pupil is a relative afferent papillary defect (RAPD), which is evaluated by swinging a flash light back and forth between the two eyes and identifying whether one pupil has lesser light perception than the other. Shine a light on one eye. Note the size of both pupils. Swing the flash light to the other eye. If both pupils now dilate, then that eye has perceived less light stimulus than the opposite eye i.e., a defect in the sensory pathway. Cranial nerves 3, 4 and 6 are assessed together by the extra-ocular range of movements and following a target which is called ‘version’, along the 6 principle position of gaze and note made of whether the patient has double-vision. Diplopia on version dictates assessment of each eye separately called ‘duction’. Evaluation of supra-nuclear gaze is to ensure that image is centered on the fovea. It is evaluated by saccades, smooth pursuit, optokinetic nystagmus, vestibule-ocular reflex. 6 nerve palsy may be a false localizing sign, due to its longest intracranial route, which is susceptible for increased ICP. Diplopia is maximum in the direction of the action of the parietic muscle and the most peripherally seen image is the false image. It is horizontal if medial or lateral rectii are involved and vertical if the elevator or the depressor muscle are involved. A lesion in the medial longitudinal fasciculus causes nystagmus of the abducting eye with absent adduction of the other eye. The lesion is on the side of the eye that should be adducting. This is called internuclear ophthalmoplegia (INO). In bilateral INO, neither eye adducts with horizontal gaze The 5th cranial nerve sensory component for light touch, sharp objects in all the three divisions along with corneal reflex which assesses the 7th nerve sensory function, must be performed. Contraction of temporalis, masseter and pterygoids along with testing for jaw-jerk evaluates 5th motor nerve. The muscles of facial expression involving frontalis, orbicularis occuli, buccinator, orbicularis oris, evaluates the motor component of 7th nerve. Sensory modalities of the 7th nerve is evaluated by sweet, salt, sour or bitter sensation of the tongue. 8th cranial nerve having vestibular and auditory components are evaluated by vestibule-ocular reflex and auditory acuity by Rinne’s and Weber’s test. 9th and 10th nerves are assessed together by seeing the elevation of the palate and uvula with or without deviation to one side and the gag reflex. Trapezius and sternocleidomastoid muscles are evaluated for function of the 11th nerve. Movements of the tongue, atrophy, fasciculations and making the patient say la, pa and ka evaluates motor components of the 12th, 7th, 9th and 10th nerves. (Junko Matsuyama, MD.)

III. Examination of the motor system Motor system examination involves evaluation of muscle, tone, power, co-ordination, assessment of symmetry, atrophy, reflex activity and gait. There are several levels of motor integration – the neuromuscular pathway along which all impulses travel to the muscles, the spinal which is the simple reflex, the hindbrain involving postural and standing reflexes, the midbrain characterized by complex standing and righting reflexes, the striatal with locomotor and automatic movements, the cortical motor integrated skilled movements and cortical associative movements involving memory and symbolization. The spino-muscular level constitutes impulses from anterior horn cell of the spinal cord and brain stem motor nuclei which go to myoneural junction and then to individual

46 General Principle muscles. The extrapyrimidal level originates in the basal ganglia and has multiple complex connections. The cortico-spinal – pyramidal level originates from cerebral cortical motor nuclei. The cerebellar nuclei helps in co-ordinating mechanisms. The psycho-motor level involves memory, initiation, consciousness and unconscious control of motor activities. Sensory and motor functions are inter-dependent in performance of volitional movement and may affect volitional, reflex, postural, tonic and phasic movements. Upper motor neuron lesions involve the cortico spinal tract that innervate the muscles of the distal extremities – hands and feet. Involvement of the cortico spinal tract causes clinical findings which are a combination of loss of direct effect of the cortico spinal tract on the lower motor neurons and the control and modulation of the indirect effects on brain stem motor fibers. UMN lesions result in loss of strength in distal extremities, dexterity, Babinski’s sign, increased tone and reflexes with a clasp-knife phenomenon, due to loss of control over indirect brain stem centers. LMN lesions result in loss of tone, strength, reflexes with wasting and fasciculations, due to denervation hypersensitivity. Decorticate posturing with thumb tucked under fingers in a fisted position, with pronation of fore arm, flexion at elbow with lower extremity in extension with foot inversion is seen in lesions above the level of red nucleus. In lesions below the level of red nucleus and above the vestibulospinal and reticulospinal nuclei, a decrebrate posturing with upper extremity in pronation and extension with lower extremity in extension is seen. In localizing UMN lesions, the lesion is on the opposite side of the clinical findings for those situated above the decussation of pyramids, whereas, it is on the same side as the clinical findings if it is in the spinal cord. Spinal cord lesions give UMN signs below the level of the lesion and LMN signs at the level of the lesion. Hypertonia can be either spasticity or rigidity. Spasticity is due to UMN lesion, has rate dependent resistance on range of movement with a collapse of the resistance at the end of movement which is called clasp-knife phenomenon. Rigidity is due to basal ganglia disease and causes uniform and constant resistance through out the range of movement and is called lead-pipe or plastic like rigidity. Motor system examination is begun by initially asking the patient to relax, breathe normally and instructing the patient to flex and extend at the fingers, wrist, elbow, ankle and knees. There is an initial normal small continuous resistance to passive movements. Observation with respect to decrease in tone (flaccidity) or increase in tone (rigidity or spasticity), must be noted. The muscles are inspected for bulk and fasciculations and palpated for tenderness, consistency and contractures. Examples of abnormalities include presence of fasciculations which ae spontaneous contactions of a motor unit noted especially due to atrophy in the deltoid muscle, interosseous muscles of the hand, in motor neuron disease or amyotrophic lateral sclerosis The strength of the muscles is evaluated by moving the patient’s arms or legs against resistance from proximal to the distal extremity in comparison with the opposite side and grading the power on a scale of 0-5, as shown in the table. The table also illustrates the muscle group involved along with the respective innervations and grading. Increased tone in the upper extremities with clasp-knife phenomenon is seen in upper motor neuron lesions. Fine fractionated movements of the fingers and hands are lost in UMN lesions. Distal extremity weakenss is greater than proximal weakness. Synkinteic movements or

Neurological Examination

47

Table

mirror movements are seen on greater effort to move the paretic hand with over flow activation of the proximal muscles of the contra lateral extremity. Hypertonia and hyperreflexia are signs of upper motor neuron lesions Stretch reflexes or deep-tendon reflexes are examined in the upper and lower extremities by a brisk tap on the muscle tendon to stretch the muscle which causes reflex contraction of the muscles and are graded according to the segmental levels as shown in table. The patient is asked to stand with both arms held straight forward with palms up and eyes closed for about 20 seconds and note made of whether he will be able to maintain extension and supination. A Pronator drift is seen in upper motor neuron lesions. Pronator drift is due to overpowering of the pronators over the weak supinators. – also called Pronator Babinski. The plantar reflex is a superficial reflex, obtained by stroking the skin of the plantar aspect beginning of on the sole of the foot at the lateral aspect of heel and advancing to the ball of the foot and continuing medially to the base of the great toe. The normal response is flexion of all the toes. An abnormal response is called Babinski’s sign and consists of extension of the great toe with fanning of the remaining toes. Pathological reflexes called frontal release signs are patterned behavioral reflexes which appear when there is a frontal lobe damage. These are primitive reflexes which are absent in the normal individuals. Pressing the blade of a tongue-depressor on the lips causes a snout reflex. The abnormal response causes pouting of thelips. Root reflex is tested by stroking the lateral upper lip. An abnormal response includes movement of the mouth towards the stimuli. Palmomental reflex causes contraction of ipsilateral mentalis of the lower lip on stroking the palm of the hand. The muscles of the lower extremities including the pelvic girdle and upper leg muscles can be assessed by making the patient squat. Patient trying to get up from sitting posture using his hands to climb the wall and pushing on his thighs to get his trunk upright is suggestive of proximal pelvic girdle weakness. When the patient uses his hands to climb up his legs, it is called Gower’s sign. Making the patient walk on the heel and then on the toes test the muscles of the foreleg. Hypertrophy of the leg with hyperpigmentation of the skin may suggest segmental neurofibromatosis. Dermatological examination evaluates various neurocutaneous syndromes.

48 General Principle

IV. Examination of the sensory system Examination of the sensory system is one of the most tricky and time consuming parts in the neurological evaluation. It is entirely subjective and sometimes, the patient response can be difficult to elicit or may be misleading. There are two major somato sensory pathways – the spinothalamic and the dorsal column lemniscus (DCML). The primary modalities for spino-thalamic system are pain and temperature and for DCML is vibration, position, sense and discriminatory sensation. The spinothalamic axons form the first order dorsal nerve root ganglion enter the root entry zone with several segmental synapses with second order neurons in the dorsal horn. Axons from second order neurons cross via ventral white commissure to the anterolateral quadrant of the spinal cord and then ascend as the spino-thalamic tract to the VPL – ventral posterior lateral nucleus of the thalamus. The 3rd order neurons project to post central gyrus or somatosensory cortex along with insular and anterior singulate cortex. The dorsal column lemniscus have axons from dorsal nerve root ganglion and enter the root entry zone ascend in the dosal column, ipsilaterally to reach second order neurons in the medualla after which they cross the midline in the medial lemniscus near the rostral pons and move laterally in proximity with the spino thalamic tract and ascends to VPL of the thalamus. The 3rd order neurons project from here to primary somatosensory cortex. The trigeminal system is the somato-sensory innervations of the face which serves for pain and temperature. It descends to the level of upper cervical spinal cord and the second order neurons cross at the opposite sides and ascends to the VPM nucleus of the thalamus. The level of crossing of the axons of the 2nd order is immediate in the spinal cord for the spino-thalamic system and not until the medulla for the DCML system. The spino-thalamic tract is lateral in the cord and the lower brain stem, while the DCML system is dorsal and medial in the cord and medial in the lower brain stem. At the level of rostral pons, both the tracts are anatomically close to each other. The descending trigeminal tract is ipsilateral to its origin and axons from 2nd order neurons cross at lower medulla and upper spinal cord level. The spinal cord and lower brain stem lesions can result in sensory dissociation which is affection of one sensory system without involving the other. Crossed findings for example, one side of the face being affected with the opposite side of the body in brain stem lesions. In spinal cord lesions, DCML system findings can be seen on one side of the body with a spino- thalamic findings on the opposite side The spino-thalamic tract is tested by examination of pain and temperature whereas the DCML system is examined by testing vibration, position, discrimination including parietal cortical sensation like tactile localization, 2-point discrimination, graphethesia, stereognosis and double simultaneous stimulation. Sharp pain is used to determine the sensory level, which is usually 1-2 spinal cord segments, below the actual lesion and the deficit confines to a dermatomal distribution. Lesion from a peripheral nerve confines itself in conformity with the peripheral nerve distribution. Polyneuropathic lesions will have stocking and glove distribution since longest axons are most affected.

Neurological Examination

49

V. Examination of gait Gait testing is an important part of the neurological evaluation which contributes to the whole neuro-axis. Most gait abnormalities are motor in nature. The basal ganglia and cerebellar system is also involved in gait abnormalities. In examining gait, the patient should be able to stand still with feet less than shoulder width apart. The patient should be able to walk with a smooth and co-ordinated gait with normal associated upper limb movements. Heel and toe walk evaluates balance and strength of the distal lower extremities. Tandem walking – heel-to-toe walk helps in evaluation of balance Basic pathological gaits include hemiplegic gait, spastic diplegic gait, neuropathic, myopathic, Parkinsonian, ataxic and choreform gait.. In hemiplegic gait, the patient has unilateral weakness and spasticity with upper limb inflexion and lower limb in extension. The foot is in extension and is too long, so that, the patient circumducts or swings the leg around to step forward. The patient has the upper extremity flexed at the elbow and hand with thumb tucked under closed fingers called cortical fisting. In diplegic gait, patient’s hips and knees are flexed and adducted with ankles extended and internally rotated. The patient walks with lower extremities, bilaterally circumducted with upper extremities in a low guard position. This is seen in paraventricular abnormalities. Legs are more affected than hands due to cortico spinal tract, axons being close to ventricles. In neuropathic gait, due to peripheral nerve disease, the distal extremity is more often affected with weak foot dorsiflexors and the patient has a high stepping gait to avoid dragging the toe. In myopathic gait, due to muscular disease, the proximal pelvic girdle muscles are weak and the patient cannot stabilize the pelvis as he moves the leg so that, the pelvis tilts towards the non-weight bearing leg, resulting in a waddling gait. In Parkisonian gait, rigidity and hypokinesia, due to basal ganglia disease, the patient stoops forward with slow, small shuffling steps and tries to catch his centre of gravity. He turns like a statue. In choreiform gait, due to basal ganglia disease, there is hyperkinesias along with irregular jerky involuntary movements of upper and lower limbs along with irregular writhing, snake like movements. In Ataxic gait due to midline cerebellar disorders, patient has a wide base with trunkal instability and walks with lurching steps with lateral veering and may fall. This gait is also seen in loss of proprioception due to peripheral neuropathy.

VI. Examination of coordination The principal area of the brain examined by co-ordination is the cerebellum which helps in motor learning, timing of motor activity, fine tuning the agonistic and antagonistic muscle activity across multiple joints for goal directed movements, dysfunction results in decomposed movements with under or over shooting causing dysmetria. Decomposed movements and dysmetria are the elements of cerebellar ataxia. Dysfunction of vestibule cerebellum causes nystagmus trunkal instability and ataxia. Spino cerebellar system dysfunction causes involvement of vernian and para-vernian regions causing trunkal instability and gait ataxia. Midline cerebellar lesions involve vestibulocerebellar and spinocerebellar connections causing trunkal ataxia, gait ataxia with wide based irregular lateral veering gait. Cerebro-cerebellar connections helps in motor planning and dysfunction causes speech ataxia – scanning dysarthria and appendicular

50 General Principle ataxia, with hypotonia decomposed movements dysmetria and dysdiadochokinesia altered rapid alternating movement dysfunction. Vestibule and spino-cerebellar (midline cerebellum) is assessed by station, walking and tandem gait. Appendicular cerebrocerebellum is assessed by rapid alternating movements, finger-nose test, toe-finger test, heel-shin test, rebound-check reflex and speech. (Anil Sangli, MD)

REFERENCES 1. Functional neuroanatomy for clinical practice. Gotoh F, Amano T. 2-59, 1992 2. Neurological Examination in Neurosurgery. Ohta T. 2-100, 2004 3. Medical Neurosciences. Daube JR, Raegan TJ, Sandock BA, Westmorend BF. Second Edition, 154-161, 1987 4. Neuroanatomy. Sano Y. 369-426, 1982

51

Evaluation and Management of Coma Patients JUN SHINODA, MD, PhD, FRCSEd1 & YOSHITAKA ASANO, MD, DMSc2 1

Center Director & Hospital Vice President, Chubu Medical Center for Prolonged Traumatic Brain Dysfunction, Kizawa Memorial Hospital Professor, Department of Clinical Brain Sciences, Gifu University Graduate School of Medicine 2 Academic Neurosurgeon-in-Chief, Chubu Medical Center for Prolonged Traumatic Brain Dysfunction, Kizawa Memorial Hospital Associate Professor, Department of Clinical Brain Sciences, Gifu University Graduate School of Medicine Key words: Coma Evaluation, Coma management, Examination of Comatosed Patient

Introduction A conscious state is regarded as a state of both full arousal and full awareness of self and surroundings. Impaired consciousness is due to disturbed arousal or content of awareness. Anatomically and physiologically, consciousness depends on the ascending reticular activating system, which ascends from the medulla oblongata to the pons, the midbrain, the hypothalamus, the thalamus and the cerebral hemispheres, and on the hypothalamic controlling system, which relates to the autonomic and the limbic systems.8,19,26) Lesions diffusely affecting the cerebral hemispheres or directly affecting these systems cause impairment of the consciousness level. Conventionally, coma has been defined as a state of unarousable psychologic unresponsiveness, in which the subject lies with his or her eyes closed, with no evidence of awareness of the environment and no response to external stimuli. A state of stupor appears as deep sleep; the patient may be transiently aroused, but only by vigorous and repeated stimuli. Obtunded is an incompletely aroused state with either auditory or tactile stimuli, with limited awareness of the environment. Somnolent, semi-coma, and drowsy are other traditional descriptors of impaired consciousness. These classical terms are often used without an accurate understanding of their meaning. Recently, because of the inexact judgment of the consciousness level based on these terms, the frequency of their use has decreased in the setting of the scientific assessment of a patient’s consciousness level. Instead, scoring based on coma scale systems, as described below, is being used.12,21,22,25)

Causes The causes of impaired consciousness are divided into two categories: intracranial and extracranial disorders. Intracranial disorders include brain trauma, such as diffuse

52 General Principle white matter injury and traumatic hematomas; cerebrovascular diseases, such as subarachnoid hemorrhage, intracerebral hemorrhage, and cerebral infarction; brain tumors; infectious diseases, such as meningitis, abscess, empyema, and encephalitis; epilepsy; and hydrocephalus.15) Extracranial disorders include metabolic diseases, endocrine diseases, respiratory insufficiency, arterial occlusion, drug-induced conditions, toxin-induced conditions, states with decreased cardiac output, and psychiatric disorders.15)

Management of Patients with Impaired Consciousness Evaluation, prompt and appropriate treatment, and investigation of the pathogenesis and mechanism of impaired consciousness are important in the initial management of patients with impaired consciousness. In an evaluation of impaired consciousness, the physician must make an objective consciousness assessment and measure the patient’s vital signs to estimate the severity of the condition. In a patient showing critical deterioration of vital signs, prompt and appropriate treatment is required. The pathogenesis and mechanism are to be investigated by taking the patient’s history, performing neurological and physical examinations, and making use of medical diagnostic technology, such as X-ray, computed tomography (CT), magnetic resonance imaging (MRI), electroencephalogram (EEG), angiography, electrocardiogram (ECG), and ultrasonography, along with laboratory data from blood, urine, and cerebrospinal fluid analyses. The results may enable an accurate diagnosis and lead to suggestions for more appropriate treatment of the condition. A high level of treatment and care are given to patients in an operating room, intensive care unit, high care unit and/or neuro-care unit, with monitoring of blood pressure, central venous pressure, SpO2, PaO2, EEG, intracranial pressure, urine, body temperature, and blood chemistry under respiratory supportive management.

Patient History Taking a history from patients with impaired consciousness is extremely difficult, and questioning friends, relatives or the ambulance team about the history of the illness often provides useful diagnostic clues. Information about situations of head injury, previous head injury, sudden collapse, limb twitching, incontinence, gradual development of symptoms, previous illness, such as diabetes, epilepsy, psychiatric diseases, alcoholism, drug abuse, viral infection and/or malignancy, is important.

Evaluation of the Consciousness Level Accurate assessment and recording are essential to determine deterioration or improvement in a patient’s impaired consciousness. To evaluate the consciousness level objectively and quantitatively in an acute clinical state, the Glasgow Coma Scale (GCS)12,25) is used internationally (Table 1), and the Japan Coma Scale (JCS)21,22) is widely used in Japan (Table 2). These scales yield scores with which to express the consciousness level. They are easy-to-understand scoring systems for not only medical

Evaluation and Management of Coma Patients Table 1 Glasgow Coma Scale 12,25)

Table 2 Japan Coma Scale 21,22)

53

54 General Principle doctors but also medical support staff, and they are useful for measuring the change in a patient’s state over time. These representative scoring systems are briefly presented.

GCS The GCS was devised by neurosurgeons at Glasgow University in 1974.12,25) Because it classifies the patient’s responsiveness into three different categories, it allows any combination of functional disorders to be recorded. These three categories correspond to the components of conscious activity, which are “arousal” (eye opening response), “activity” (motor response), and “awareness” (verbal response), and the score is given according to the response level in each category. Normally, the consciousness level can be evaluated by the sum of the scores in these three categories. This scale does not include vague terms such as stupor, semicoma, and deep coma. Eventually, the consciousness level can be graded into thirteen levels by 120 combinations of different scores in each category. This is the first scale in the world that described coma with a scoring system.

JCS The JCS was established by Ohta, et al. in 1974.21,22) In terms of emergent medicine in the acute stage, impaired consciousness is due mainly to cerebral herniation, especially tentorial/uncal herniation, and should be alleviated by intracranial decompression at the appropriate time. From the viewpoint of neuroemergent management, impairment of consciousness is to be graded according to the level of arousal. Impaired consciousness is classified primarily into three code levels in the JCS: awake without any stimuli, rousable but reverts to previous state if stimulus stops, and unrousable using any forced stimuli. This scale ultimately grades consciousness into ten levels, including a normal consciousness level (alert), and supplements that with two care-need condition terms: restlessness and incontinence.

Evaluation of Vital Signs When evaluating the consciousness level in patients with severely impaired consciousness, the clinician should not overlook vital signs, including blood pressure, pulse, respiration, cyanosis, and anemia. Even in cases of mildly impaired consciousness, changes in vital signs are important. Checking vital signs is essential for early detection of deteriorated conditions that need emergency treatment.4,9,16)

Respiration In patients with impaired consciousness, airway obstruction by oral, nasal, and tracheal oversecretion, blood, foreign body, and/or vomited foods is often seen. Additionally, breathing impairment due to a disturbed respiratory system resulting from damage in the central or peripheral nervous system, mechanical damage or injury of the thorax, and convulsive disorders is also important to treat. Regardless, if the airway

Evaluation and Management of Coma Patients

55

is not patent, prompt correction is mandatory. After airway establishment, oxygen and ventilatory support are to be provided, and gas concentration and oxygen saturation in blood are to be monitored. Even in states of less critical respiratory disturbance, it is essential to check the movement of the thorax and the respiratory pattern (depth, rhythm and rate). For example, the patient should be observed for signs of Cheyne-Stokes breathing, central neurogenic hyperventilation, apneusis, cluster breathing and ataxic breathing, lung sounds, wheeze, and cyanosis (Figure 1).23) Patients with impaired consciousness are always under the condition of swallowing disturbance, and are exposed to the risk of aspiration pneumonia throughout their clinical course. Appropriate treatment in the early stage is mandatory. The autonomic respiratory center of the central nervous system is located in the reticular formation in the medulla. The center’s rhythmic discharges produce spontaneous respiration and are regulated mainly by alternations in arterial PO2, PCO2, and H+ concentration. Well-known abnormal respiratory rhythm patterns include the following: Cheyne-Stokes breathing, characterized by repetitive cycles of waxing and waning respiration (damages of the diencephalon or the diffuse or bilateral cerebral

Fig. 1 Abnormal respiratory patterns associated with pathological lesions (shaded areas) at various levels of the brain. Tracings by chest-abdomen pneumograph, inspiration reads up. A: Cheyne-Stokes respiration. B: Central neurogenic hyperventilation. C: Apneusis. D: Cluster breathing. E: Ataxic breathing. (From Plum F, Posner JB: The diagnosis of stupor and coma. 2nd ed. Philadelphia, Davis, 1972 23))

56 General Principle hemispheres); central neurogenic hyperventilation, characterized by rapid and deep respiration (damages of the midbrain); apneusis, characterized by a 2 to 3 seconds pause at full inspiration (damages of the mid- or caudal pons) and ataxic breathing, characterized by irregular respiration (damages of the medulla) (Figure 1).23) These are typical abnormal respiratory patterns seen during the progression of cerebral herniation. The efferent output from the autonomic respiratory center to the respiratory motor neurons is located in the white matter of the spinal cord between the lateral and ventral corticospinal tracts. The nerve fibers mediating inspiration converge on the phrenic motor neurons located in the ventral horn from C3 to C5 and the external intercostal motor neurons in the ventral horn throughout the thoracic cord.4,9,16) In patients with impaired consciousness and respiratory malfunction, especially those with traumatic injury including the neck, damage to the spinal cord should be taken into consideration.

Circulation Measurement of the blood pressure and assessment of the pulse rate, rhythm, and bruit of the carotid artery are essential in cases of carotid atherothrombotic carotid occlusion or stenosis. A carotid ultrasonogram is also useful. Subclavian occlusion may result in diminished blood pressure measured at the arm, but the carotid pulse is preserved. 4,9,16) Cerebral perfusion pressure (CPP) is determined as a balance between arterial pressure (AP) and intracranial pressure (ICP). Cerebral blood flow (CBF) is normally maintained in the range of 50 to 60 ml/100 g/min (mean hemisphere flow), as long as the CPP is kept in the range of 50 to 150 mmHg by autoregulation of the CBF. After the CCP is decreased to less than 50 mmHg (at an AP of approximately less than 65 mmHg, when the ICP is in the normal range), CBF diminishes, and brain dysfunction, including consciousness impairment, can be induced by cerebral ischemia.4,9,16) Ten seconds after the cerebral circulation ceases completely, consciousness is lost. Electrical activity of the neurons in the brain disappears 20 seconds later, and irreversible brain damage results 3 to 8 minutes later. Prompt improvement of circulation is essential in cases of impaired consciousness with circulation failure.

Evaluation of Pupil and Eye Position Pupil size, light reflex, corneal reflex, oculocephalic reflex, oculovestibular responses, ciliospinal reflexes, and eye position should be evaluated. A funduscopic examination should also be performed. In cases of lesions in the hypothalamus, the pupils are miotic, accompanied with Horner’s syndrome (ptosis, miosis, and enophthalmos). Bilateral diencephalic damage induces miosis, but the light reflex is preserved. The light reflex is absent when the midbrain is involved, and the shape of the pupils is sometimes irregular, and anisocoria is common. Pin-point pupil is well known in cases of pontine lesions, and lesions of the medulla oblongata often induce mild Horner’s syndrome with preservation of the light reflex (Figure 2).23) Horizontal or perpendicular roving eye movement, which is often seen in patients with severely impaired consciousness, suggests supratentorial lesions. In cases of supratentorial

Evaluation and Management of Coma Patients

57

Fig. 2 Pupils in comatose patients. (From Plum F, Posner JB: The diagnosis of stupor and coma. 2nd ed. Philadelphia, Davis, 1972 23))

lesions, the eyes look to the paralytic side as a conjugate deviation, while in cases of infratentorial lesions, they look to the stimulated side. Retraction nystagmus, in which the eyeballs turn backward to the orbita irregularly and rapidly, is seen in cases of lesions in the posterior third ventricle to the pineal body. Seesaw nystagmus, which is a pendulum-like nystagmus with eyeball dissociation, is seen in cases of lesions around the third ventricle. Ocular bobbing (rapid and perpendicular eye movement) and skew deviation suggest lesions in the pons. The oculocephalic reflex (doll’s head maneuver) is tested by rapid passive turning of the head. If the reflex is intact, the eyes move together in the direction opposite to the head movement. In cases of infratentorial lesions, the oculocephalic reflex disappears. This maneuver should not be performed until it is certain that the patient has not sustained a neck injury. Eye movements can be tested by irrigating each external auditory canal with 50 ml of ice water with a small catheter (cold caloric stimulation). If the oculovestibular pathways are intact, cold caloric stimulation results in ipsilateral, conjugate tonic deviation of the eyes toward the side of the stimulus.

Evaluation of Motor Response Patients who obey commands are considered to be the group that gives the best motor response. For patients who can not obey commands, a painful stimulus is applied

58 General Principle to the supraorbital nerve (e.g., rubbing the thumb nail in the supraorbital groove and increasing the pressure until a response is obtained) and the response evaluated in the limbs without motor paralysis.15) If the patients respond by bringing the hand up beyond the chin, they are considered as patients who can localize to pain. If the patient does not localize to pain, pressure with a pen or hard object to the nail bed is applied. Patients who demonstrate elbow flexion without spastic wrist flexion are considered patients who can withdraw from a stimulus. Bilateral, unilateral or diffuse brain damage induces such motor responses.15) Inappropriate motor response includes decorticate posture and decerebrate posture. Decorticate posture consists of flexion of the arm, wrist, and fingers, with adduction in the upper extremity and extension, internal rotation, and plantar flexion in the lower extremity in response to noxious stimuli. In patients who show decorticate posture, moderate to large sized lesions of the diencephalon, basal ganglia, internal capsule, and/or thalamus may be involved. Decerebrate posture consists

Fig. 3 Motor responses to noxious stimulation in patients with acute cerebral dysfunction. The first line: patients who obey commands, localize pain, and withdraw extremities. The second line: patients showing decorticate posture. The third line: patients showing decerebrate posture. The fourth line: patients showing no response with flaccidity. (From Plum F, Posner JB: The diagnosis of stupor and coma. 2nd ed. Philadelphia, Davis, 1972 23))

Evaluation and Management of Coma Patients

59

of arm extension with external rotation of the wrists and leg extension with internal rotation of the feet to noxious stimuli. Patients who show decerebrate posture may have damage of the midbrain and/or the rostral pons. In patients who show no motor responses, but instead demonstrate bilateral flaccidity to noxious stimuli, the caudal pons and/or the medulla may be damaged (Figure 3).23)

Evaluation of Seizure Seizures are recognized in various types of brain disorders with impaired consciousness, and seizures can cause consciousness disturbance as well. A convulsive seizure is usually recognized by its dramatic motor manifestations. Even with a short-duration convulsive seizure, it is difficult to check vital signs in an emergency, and the seizure requires prompt treatment. In status epilepticus, patients appear to have impaired consciousness for several hours to a few days, and an EEG is required for diagnosis and appropriate and prompt medical treatment. Anti-convulsive drugs and sedatives also may induce prolonged consciousness impairment and affect vital signs. Serum concentrations of these drugs should be monitored in these cases.

Evaluation of Blood and Urine The causes of impaired consciousness without intracranial or vascular lesions include metabolic, drug-induced, and toxin disorders. Metabolic disorders, such as hypo/hypernatremia, hypo/hyperkalemia, hypo/hypercalcemia, hypo/hyperglycemia, diabetic ketoacidosis, uremia, hepatic failure, and porphyria can be diagnosed by blood and urine assessment. In cases of hypercapnia and hypoxia due to respiratory insufficiency, blood gas analysis is required. In patients suspected of drug-induced disorders or toxin abuse, blood and urine concentrations of the corresponding agents, such as sedatives, opiates, antidepressants, anticonvulsants, anesthetic agents, alcohol, carbon monoxide, and heavy metals, should be investigated.

Evaluation of Fever Fever is the oldest and most universally known hallmark of disease. It often occurs not only in infectious diseases in the central nervous system, such as meningitis, encephalitis, intracranial empyema, and brain abscess, but also in non-infectious disorders with dysfunction of the thermoregulatory center in the hypothalamus. Brain damage involving the hypothalamus to the midbrain, such as severe traumatic brain injury, brain tumors, cerebrovascular disease, and hydrocephalus, sometimes causes consciousness impairment accompanied with intractable hyperthermia (nearly 40°C) known as dysautonomia syndrome. 2,5) This is a syndrome with a dramatic and paroxysmal presentation characterized by tachycardia, arterial hypertension, hypersudation, muscle hypertonia, hyperthermia and increased respiratory rate. Intrathecal baclofen therapy has been reported to be efficient in controlling this syndrome.2,5)

60 General Principle

Other General Examinations The presence of lacerations, bruising, cerebrospinal fluid (CSF) leaks, bleeding from the internal auditory meatus after traumatic head injury, neck stiffness, Kernig’s sign, an infection source, pyrexia, or tense anterior fontanelle in infants is informative for diagnosis.

Evaluation of Intracranial Pressure Commonly seen clinical features caused by raised ICP are headache, vomiting, and papilloedema. Raised ICP is a condition often seen in patients with impaired consciousness due to brain disorders. However, these clinical features cannot be communicated by patients with impaired consciousness. When the ICP is raised to more than 30 mmHg in a short period, CBF is reduced. To maintain CBF, the AP rises. Stimulation of vagal outflow induces bradycardia, and respiration becomes deep and slow. These three phenomena (AP rising, bradycardia, and slow and deep respiration) are called the Cushing reflex, which is an important sign of raised ICP and which can be recognized in patients with impaired consciousness.6,7) The cranial cavity normally contains a brain weighing approximately 1400 g, 75 ml of blood and 75 ml of CSF, which are encased in a rigid bony enclosure in adults. When the volume of one or more of the three components is increased, the volume of the remaining components is decreased, and the total volume in the cranium is to be kept constant (Monro-Kellie doctrine).3,14,18) In cases in which any one component’s volume or a combination of component volumes is increased over the compensation, the ICP is increased. Respiratory failure emerges according to the Cushing reflex in patients with progression of raised ICP and induces metabolic acidosis caused by CO2 accumulation. In this condition, blood vessels are enlarged, cerebral blood volume is increased, and ICP is accelerated to increase further. Hyperventilation decreases the PCO2 concentration and cerebral blood volume by vascular contraction, and results in improvement of ICP in such cases.

Brain shift and herniation The inelasticity of the skull and the limited elasticity of the falx and the tentorium limit the ability of the brain to adjust to space-occupying masses, and the brain expands by squeezing through the tentorial edge, the falx edge, the sphenoidal ridge, and/or the foramen magnum, and the situation is called brain herniation. Brain herniation is a critical condition that causes consciousness impairment and results in death. Brain herniation causes not only regional damage of the herniated brain, but also injuries to the vessels and nerves passing nearby, which may cause remote neurological symptoms. Brain herniation is divided into the following five major types: tentorial (lateral), tentorial (central), subfalcine, sphenoidal ridge, and tonsillar.23) Tentorial herniation (lateral): A unilateral expanding mass causes tentorial (uncal) herniation, as the medial edge of the temporal lobe herniates through the tentorial hiatus. The posterior cerebral artery is sometimes occluded, and a homonymous

Evaluation and Management of Coma Patients

61

hemianopsia may result. Compression of the third nerve (the oculomotor nerve) causes pupil dilatation and failure to react to light. The contralateral hemiparesis is due to compression of the ipsilateral cerebral peduncle. Pressure from the tentorial edge on the opposite cerebral peduncle (Kernohan’s notch) may produce limb weakness on the same side as the lesion (false localizing). As the ICP continues to rise, tentorial herniation (central) follows (Figure 4).23) Tentorial herniation (central): A midline lesion or diffuse swelling of the cerebral hemispheres results in a vertical displacement of the midbrain and diencephalon through the tentorial hiatus. Damage to these structures occurs either from mechanical distortion or from ischemia secondary to stretching of the perforating vessels. Pressure on the tectum impairs eye movements (upwards gaze is initially lost). Diencephalon and midbrain damage cause deterioration of the consciousness level. The pupils are initially small and become moderately dilated and fixed to light. Downward traction on the pituitary stalk and the hypothalamus may cause diabetes insipidus (Figure 4).23) Subfalcine herniation: Unilateral space-occupying hemispheric mass lesions force the cingulate gyrus under the falx. Ipsilateral anterior cerebral artery occlusion sometimes occurs (Figure 4). Sphenoidal ridge herniation: Unilateral space-occupying hemispheric mass lesions force a part of the frontal lobe through the sphenoidal ridge to the middle cranial fossa. This is a rare type of cerebral herniation. Tonsillar herniation: An infratentorial expanding mass causes herniation of the cerebellar tonsils through the foramen magnum. Brainstem pressure results in deterioration of the consciousness level and respiratory abnormality. Tonsillar impaction in the foramen magnum produces neck stiffness and head tilt. A degree of upward cerebellar herniation through the tentorial hiatus is usually present. An injudicious lumbar puncture in the presence of an infratentorial mass may cause a pressure gradient sufficient to induce tonsillar herniation.

Fig. 4 Brain herniations. 1: Subfalcine herniation. 2: Tentorial herniation (lateral). 3: Compression of the opposite cerebral peduncle against the unyielding tentorium, producing Kernohan’s notch. 4: Tentorial herniation (central). (From Plum F, Posner JB: The diagnosis of stupor and coma. 2nd ed. Philadelphia, Davis, 1972 23))

62 General Principle

Treatment of raised intracranial pressure As dictated by the Monro-Kellie doctrine, raised ICP can be lowered by reducing the volume of any of the intracranial components, even if that component is normal. Head elevation: A patient with raised ICP is positioned with the head raised 30 to 40 degrees above the level of the heart. The rationale has been that elevation of the head enhances venous drainage, thus reducing intracranial blood volume and ICP. Hyperventilation: Hyperventilation induces a PaCO2 decrease, which causes pHmediated cerebral vasoconstriction and a decrease in ICP. An appropriate level of PaCO2 is 25-30 mmHg. Too much hyperventilation, which may induce a critical CBF decrease, should be avoided. Hypothermia: Conventional hypothermia (core body temperature less than 30°C) has been shown to decrease ICP, CBF, and cerebral metabolism. However, because of complications including cardiac arrhythmia and coagulopathy and the difficulty in maintaining the required core temperature, conventional hypothermia has been abandoned clinically. Mild (34°C) to moderate (32-34°C) hypothermia has been reported to reduce ICP and CBF significantly with fewer complications, and it is commonly used clinically. Hypertonic solution: Some hypertonic solutions, including sucrose, albumin, urea and mannitol, have been used in the treatment of raised ICP. These agents create an osmotic gradient between the blood and the brain parenchyma, resulting in movement of water from the brain to the vascular compartment. Mannitol is the most common agent in the treatment of raised ICP, and the recommended dose ranges from 0.25 to 2.0 g per kg intravenously every 4 to 8 hours. The peak reduction in ICP occurs in about 15 minutes, and the duration of action is about 4 hours. These are effective only when the blood-brain barrier (BBB) is intact. Furosemide: Furosemide, which is one of the loop diuretics, has been shown to reduce CSF production and to decrease ICP. Furosemide is effective even in cases of BBB disruption, in contrast to osmotic agents. Steroids: The mechanism by which steroids reduce brain edema remains unknown. Neuronal membrane stabilization is suggested as a rational mechanism experimentally. Steroids are effective for raised ICP resulting from brain tumors; however, there is no evidence supporting their efficacy in lowering ICP in traumatic brain injury and cerebral infarction. Barbiturates: Barbiturates reduce neuronal activity and depress brain metabolism, oxygen consumption, and intracellular accumulation of calcium, and they scavenge free radicals, resulting in suppression of brain edema. Another beneficial action of barbiturates is vasoconstriction in normal brain, resulting in a decrease in cerebral blood volume (CBV) and a lowering of ICP. This mechanism results in shunting of blood from wellperfused normal brain areas to ischemic areas, an effect termed “inverse steal” or the “Robin Hood phenomenon”, which protects the brain from further ischemia.4,9,16) Surgical interventions: CSF withdrawal using lumbar puncture or ventriculostomy via skull burr hole immediately reduces the ICP. Continuous CSF drainage may make most advantage of this method. Other surgical modalities include large craniectomy as external decompression and internal decompression by means of lobectomy and

Evaluation and Management of Coma Patients

63

debulking of the mass lesion.

Chronic Consciousness Impairment Consciousness impairment in a chronic phase means a state in which brain damage due to any neurological disorder remains, whereby consciousness impairment is prolonged, and includes the following states: vegetative state, minimally conscious state, locked-in syndrome, akinetic mutism, apallic syndrome, and transit syndrome. Of these terms, akinetic mutism, apallic syndrome, and transit syndrome are classical and may cause confusion because of their obscure meaning. They are rarely used today. Vegetative state: This is a chronic neurological condition characterized by lack of awareness of external stimuli, with preservation of sleep-wake cycles and vital vegetative functions, such as cardiac action, respiration, and maintenance of blood pressure. As far as can be determined, the patient remains unaware of both self and environment. Minimally conscious state: This state is defined as patients who show more than reflex responsiveness but remain unable to communicate their thoughts and feelings, and differs from the vegetative state by the presence of inconsistent but clearly discernible behavioral evidence of awareness of self or environment, responding purposefully to sensory stimuli and/or responding to command. Locked-in syndrome: The patient is aware and awake, but is paralyzed and unable to talk, although some facial and eye movements are preserved. Bilateral damage at the medullary or the ventral pons level usually causes this syndrome. Akinetic mutism: The patient does not move or talk in spite of no motor or sensory disturbance anatomically, but sleep-wake cycles are present. No voluntary movement or behaviors can be seen, and sometimes the eyes open. Responses are barely present to extremely strong external stimuli. This can be divided into two types according to the lesions. One is due to a widespread bilateral frontal lesion including the anterior cingulum, and the other is due to lesions of the diencephalon or the brainstem. Apallic syndrome: A state without any cognitive activity due to diffuse severe damage of the cerebral cortex. Transit syndrome: This is a syndrome which is deemed to be recognized in the recovery course of coma patients, in which decreased activity, emotional instability, and amnesia are prominent. Recently, vegetative state and minimally conscious state also have been considered transit states in the recovery course in some coma patients under certain circumstances.

Evaluation of chronic impaired consciousness level Chronic impaired consciousness level has rarely been evaluated qualitatively using scoring system. Two representative scoring systems are presented. The Coma Remission Scale (CRS), which aims at the assessment of restoration of impaired higher cortical function from coma and apallic syndrome/vegetative state, was established by the German Task Force on early neurological-neurosurgical neurorehabilitation in 1993.27,28) This scale includes six categories for clinical evaluation, which are arousability/attention, motor response, response to acoustic stimuli, response

64 General Principle to visual stimuli, response to tactile stimuli, speech motor response, and is successfully used in German-spoken countries. The consciousness or the higher cortical function level can be evaluated by the sum of the scores in these six categories (Table 3).27,28) Table 3 Coma Remission Scale 27,28)

In the Chubu Medical Center for Prolonged Traumatic Brain Dysfunction in Japan, another evaluation system is used.24) Patients with prolonged consciousness impairment are normally divided into three grades according to their awareness level in this system.

Evaluation and Management of Coma Patients

65

This is an easily evaluable scale called the “Communication Grading System for Prolonged Consciousness Impairment” for the bedside clinic (Table 4).24) Table 4 Communication Grading System for Prolonged Consciousness Impairment 24)

Brain Death Brain death must be distinguished from reversible coma and from prolonged consciousness disturbance, including vegetative state and minimally conscious state. Numerous guidelines to determine brain death have been published internationally. Commonly accepted features include irreversible coma, established cause, absent brainstem reflexes, apnea, and lack of factors that may obscure or complete the examination (i.e. hypothermia, sedative medications, and neuromuscular blocking medications).1,10,11,13,17,20)

REFERENCES 1. An appraisal of the criteria of cerebral death: a summary statement. A collaborative study. JAMA 237: 982-986, 1977 2. Baguley IJ, Cameron ID, Green AM, Slewayounan S, Marosszeky JE, Gurka JA: Phalmacological management of dysautonomia following traumatic brain injury. Brain Injury 18: 409-417, 2004 3. Burrows G: Disorders of the cerebral circulation. Philadelphia, Len & Blanchards, 1848 4. Cohen DS, Quest DO: Increased intracvranial pressure, brain herniation, and their control. In Wilkins RH, Rengachary SS, eds. Neurosurgery. Vol 1. 2nd ed. New York, McGraw-Hill, 1996, pp345-356 5. Cuny E, Richer E, Castel JP: Dysautonomia syndrome in the acute recovery phase after traumatic brain injury: relief with intrathecal Baclofen therapy. Brain Injury 15: 917925, 2001 6. Cushing H: Concerning a definite regulatory mechanism of the vasomotor center which controls blood pressure during cerebral compression. Johns Hopkins Hosp Bull 12: 290-292, 1901

66 General Principle 7. Cushing H: Some experimental and clinical observations concerning states of increased intracranial tension. Am J Med Sci 124: 375-400, 1902 8. Gelhorn F: Experimental ontribution to duplicity theory of consciousness and perception. Pfluger Arch ges Physiol 255: 75-92, 1952 9. Goldstein LB, Roses AD: Initial evaluation and treatment of the comatose patient. In Wilkins RH, Rengachary SS, eds. Neurosurgery. Vol 1. 2nd ed. New York, McGraw-Hill, 1996, 307-314 10. Guideline for the determination of death. JAMA 246: 2184-2186, 1981 11. Guideline for the diagnosis of brain death. Can J Neurol Sci 14: 653-656, 1987 12. Jennett B, Bond M: Assessment of outcome after severe brain damage: A practical scale. Lancet 1: 480-485, 1975 13. Kaste M, Hillbom M, Palo J: Diagnosis and management of brain death. Br Med J 1: 525527, 1979 14. Kellie G: An account of the appearance observed in the dissection of two of three individuals presumed to have perished in the storm of the 3D and whose bodies were discovered in the vicinity of Leith on the morning of the 4th of November 1821, with some reflections on the pathology of the brain. Trans Med Chir Sci Edinb 1: 84, 1824 15. Lindsay KW, Bone I: Neurology and neurosurgery illustrated. 4th ed. Churchill Livingstone, 2004 16. Marshall LF, Marshall SB: Differential diagnosis of altered states of consciousness. In Youmans JR, ed. Neurological Surgery. Vol.1. 4th ed. Phyladelphia, Saunders, 1996, pp61-70 17. Mohandas A, Chou SN. Brain death. A clinical and pathological study. J Neurosurg 35: 211-218, 1971 18. Monro A: Observations on the structure and the function of the nervous system. Edinburgh, Creek & Johnson, 1783 19. Moruzzi G, Magoun HW: Brain stem reticular formation and activation of the EEG. Electroencephalogr Clin Neurophysiol 1: 455-473, 1949 20. O’Brien MD: Criteria for diagnosing brain stem death. Br Med J 301: 108-109, 1990 21. Ohta T, WAga S, Handa H, Saito I, Takeuchi K, Suzuki J, Takaku A: New grading of level of disordered consciousness. No Shinkei Geka 2: 623-627, 1974 (Jpn) 22. Ohta T, Kikuchi H, Hashi K, Kudo Y: Nizofenone administration in the acute stage following subarachnoid hemorrhage. Results of a multi-center controlled double-blind clinical study. J Neurosurg 64: 420-426, 1986 23. Plum F, Posner JB: The diagnosis of stupor and coma. 2nd ed. Philadelphia, Davis, 1972 24. Shinoda J, Okumura A, Ito T, Takenaka S: Communication grading system for prolonged consciousness impairment used in the Chubu Medical Center for Prolonged Traumatic Brain Dysfunction. Proceeding of the 17th Annual Meeting of the Japan Coma Society. 2008, p66 (Jpn) 25. Teasdale G, Jennett B: Assessment of coma and impaired consciousness: A practical scale. Lancet 2: 81, 1974 26. Tokizane T: Functional differentiation of the brain activating systems. Seishin Igaku 4: 793-798, 1962 (Jpn) 27. von Wild KRH: Perioperative management of severe head injuries in adults. In Schmidek H, ed. Operative neurosurgical techniques: indications, methods, and results. Philadelphia, Saunders, 2000, pp45-60 28. von Wild KRH: Early rehabilitation of higher cortical brain functioning in neurosurgery, humanizing the restoration of human skills after acute brain lesions. Acta Neurochir Suppl 99: 3-10, 2006

67

Nutritional management in neurosurgical field CHIE MIHARA, MD, PhD Chief Director, Brain-checkup Center, NST supervisor, Hibino Hospital Address: 7955, Tomo, Numata-cho, Asaminami-ku, Hiroshima, 731-3161, Japan Key words: nutrition, neurosurgery, nutrients, nutritional status, nutritional assessment

Characteristics of neurosurgical diseases 1. Comprehension of nutritional status Most of neurosurgical diseases occur suddenly, especially stroke and trauma. The patient had usual food before the onset of a disease, so nutritional status of most patients is normal. However, the patients with chronic neurological disease, that is gradually getting worse (degenerative disease or tumor), might reveal appetite loss and malnutrition. And the elderly patients often show silent dehydration. In any case, medical staff should take enough nutritional information besides neurological findings. 2. Time course of symptoms Nutritional management of neurosurgical patients should be arranged along time course of their symptoms. Usually, stage of disease is defined in three phases; acute phase (within 1 week), sub acute phase (within1 month), and chronic phase (over 1month). We should select nutritional strategy as per symptoms of each phase. 3. Dysphagia Many patients show dysphagia. Motor weakness from face to pharyngeal cavity leads to swallowing disturbance. Especially, elderly patients basically have weakness of muscles around throat, and then even healthy person can easily suffer aspiration. Patients with dysphagia often show weakness of cough reflex. When the patient's cough reflex is weak, aspiration pneumonia will occur without cough. It is called as silent aspiration, and other persons around the patient should be careful for this difficult situation to notice.

Practice of nutritional management for neurosurgical disease 1. Nutritional management for each clinical stage Method of nutritional management should be selected along clinical situation from mild to severe symptoms. And it will change with each stage of a disease. So adequate nutritional replenishment should be provided to the patient as per severity and stage of the disease1) (Fig.1). The time course of neurosurgical diseases is usually divided in three stages (Fig 2).

68 General Principle

Fig. 1 Nutritional management according to stage and severity of a disease

Fig. 2 Time course of nutritional management

1) Acute stage: Brain edema has a peak after operation or onset of injury, and continues for a week. This stage is very important, because neurological outcome depends on the damage of the brain. Nutrition is supplied to a patient mainly through parenteral root with giving neurological treatment priority over nutrition. When the situation of a disease is mild, enteral or oral nutrition will be started within a week. 2) Subacute stage: This stage is between acute stage and chronic stage, usually from 3 to 4 weeks. Neurological symptoms are unstable in most patients, so method of

Nutritional management in neurosurgical field

69

nutritional management varies. For the mildly damaged patients, oral intake will be started. For moderate damaged patients, enteral nutrition will be started. When a patient has dysphagia or unconsciousness, parenteral nutrition is continued. 3) Chronic stage: The symptoms and neurological deficits will be fixed around a month. When a patient has enough swallowing ability, oral intake is the main feeding route. For patient with prolonged unconsciousness or severe dysphagia, enteral route of nutrition is continued for a long period. 2. Methods of nutritional supply 1) Parenteral nutrition: Basically nutrition should be supplied to a patient through oral or enteral route. When gut works, enteral nutrition is better for a patient than parenteral route, because the membrane of gut has immunological defending ability and enteral route is natural. However, when a patient shows difficulty of enteral nutrition with some troubles such as severe nausea or diarrhea, parenteral nutrition is selected. Total parenteral nutrition (TPN) through with central venous route is recommended for a prolonged enteral nutrition more than a week. TPN will easily cause infection such as sepsis through an intravenous catheter, it is to be desired that enteral or oral intake will start as soon as possible. 2) Enteral nutrition: A nasogastric tube is usually used at the start of treatment. It is an easy nutritional way in even early stage of a disease for aspiration of gastric contents and administration of drug. If a patient shows severe nausea or vomiting and has a risk of aspiration pneumonia, post pylorus way should be selected. Some nutritional guidelines recommend percutaneous endoscopic gastrostomy (PEG), when a patient needs enteral nutrition for more than 4weeks2). Recently, intermittent oroesophasial tube feeding (IOE)3) is used for a cooperative patient with dysphagia. A patient may have some complications, which relates tube troubles, digestive trouble (ex, diarrhea or vomiting), metabolic troubles (ex, glucose imbalance or electrolyte imbalance), and so on. There are many nutritious formulas, so we can select an adequate composition for a patient's nutritional condition. Most of formula is made as 1kcal /ml, and can be started without dilution. Diarrhea may be caused by high speed administration, so enteral nutrition should be started slowly in a speed of 25~30ml/hr, then gradually be increased. 3) Oral intake: It is most natural and best way for nutritional management, but has a risk of aspiration pneumonia for a patient of dysphagia. When a patient has consciousness disturbance or dysphagia, oral intake should be started under the careful watching to avoid aspiration. Liquid goes through the pharynx faster than solid substance, so oral intake should be started with jelly or half solid food. Liquid should be supplied with mixing viscous substance. Swallowing ability can be correctly assessed by swallowing examination of video fluoroscopy (VF) or video endoscopy (VE). When a patient has not enough swallowing ability, swallowing rehabilitation is necessary with cooperation of a medical team of co-medical staffs (nurse, speech therapist, physical therapist, occupational therapist, dental hygienist, et al). PEG or IOC is more recommendable route than nasogasiric route, because a patient has low risk of aspiration and irritability.

70 General Principle

Important points 1. Nutritional assessment Before starting nutritional management, we should know the nutritional condition of a patient. There are many nutritional parameters. Most simple and reliable one is subjective global assessment (SGA)4). We can easily assess the nutritional condition of a patient from information of change of body weight, food taking, digestive symptoms, and edema of body surface. Then we also can understand the details of a patient's nutritional condition with measurement of body (height, weight, triceps skin fold, arm circumference, et al) and laboratorial data (serum protein, glucose level, lymphocyte counts, et al). 2. Energy expenditure Energy expenditure of a patient is very important for nutritional management. Real time energy expenditure is changing by every hour, so we should calculate it by machine or formula. Resting energy expenditure is gained by an indirect energy expenditure measuring machine, which uses respiratory quotient, but it is very expensive. So we usually use basal energy expenditure, which is calculated by Harris- Benedict's formula5). More simple way is using 25-30 kcal/kg/day. In any case, we should regularly assess the nutritional condition every time, and control supply of energy. In adding, prolonged unconscious patient's energy expenditure is low as about 22 kcal/kg/day in author's data6). 3. Opportunistic infection Severe case is treated in intensive care unit for a few weeks. When a patient has severe brain edema, control of intracranial pressure is more dominant matter than nutritional management for most neurosurgeons. After moving to usual ward, many patients may be malnourished and cause opportunistic infection because of malnutrition. Short bowel's membrane has immunological protecting system, called as GALT (gutassociated lymphoid tissue). To avoid opportunistic infection, nutritional management should be started from acute stage for supporting GALT. Immunonutrition, which contains glutamine, n-3 fatty acid, and antioxidant, is recommended to be used in acute stage of diseases7). 4. Water supply Unconscious patients are completely under passive control for nutritional management. A patient can not complain of hunger or thirstiness. Water supply is usually thought enough as 1ml/kcal. Neurosurgical patients, especially stroke patients, suffer from muscle atrophy which causes decrease of weight. So calculated water volume tends to show smaller amount than real necessity. Dehydration leads to cerebral infarction, deep vein thrombosis, pneumonia, and so on. Water supply should be controlled enough for each patient's condition. During swallowing rehabilitation, enough water and calorie should be supplied through an enteral route (PEG or IOE) beside of oral intake.

Nutritional management in neurosurgical field

71

5. Oral care Oral care is very important for oral intake. Patients who suffer from dysphagia often show weakened both swallowing and cough reflexes, and saliva or sputum is aspirated, even if a patient does not eat. When oral cavity is dirty, aspiration pneumonia can easily occur. Cooperation of patient attendant, dentists and dental hygienists is essential for high-quality oral care. 6. Elementary nutrients Bed ridden patients are often decubitus for very long time thus making them prone for pressure sores / ulcers. When ulceration or erosion of skin continues for a long time, insufficiency of elementary nutrients, such as Zn, should be remembered. Anemia is caused by insufficiency of Fe and Cu. Se is recently focused as cause of cardiac dysfunction. Most enteral formula contains these elementary nutrients. But prolonged unconscious patients tend to receive small amount of enteral nutrition, hence insufficiency of elementary nutrients may occur, which necessarily require replenishment.

REFERENCES 1. Chie Mihara, Kanji Yamane, Saori Ishinokami, et al: Nutrtional management for stroke patients. Surgery for Cerebral Stroke (Japanese) 33: 323-329, 2005 2. Fertl E, Steinhoff N, Schofl R, et al: Transient and long-term feeding by means of percutaneous endoscopic gastrostomy in neurological rehabilitation. Eur Neurol 40: 2730, 1998 3. Nakajima M, Kimura K, Inatomi Y, et al: Intermittent oro-esophageal tube feeding in acute stroke patients -- a pilot study. Acta Neurol Scand 113:36-39, 2006 4. Detzky AS, McLaughlin J R, Baker J P, et al: What is subjective global assessment of nutritional status? JPEN 11: 8-13, 1987 5. Harris JA, Benedict FG: A biometric study of human basal metabolism. Proc Natl Acad Sci USA 4: 370-373, 1918 6. Chie Yamanaka, Takeshi Shima: Nutritional assessment of neurosurgical patients. Neurological Surgery (Japanese) 21: 703-709, 1993 7. Jones NE, Heyland DK: Pharmaconutrition: a new emerging paradigm. Curr Opin Gastroenterol 24: 215-222, 2008

72

Anaesthesia for intracranial surgery: general principles POL HANS, VINCENT BONHOMME Department of Anaesthesia and ICM, Liege University Hospital, Belgium Key words: Intracranial surgery, Anesthesia, General principles Intracranial surgery has considerably evolved over the last two decades. Major changes mainly trend towards minimally invasive and functional procedures including endoscopic surgery, small size craniotomies, intra-operative magnetic resonance imaging and stereotactic approaches in different pathologies. It aims at preserving or restoring brain function, achieving immediate and good recovery, and avoiding as far as possible the usual stay in the intensive care unit. Those objectives may require long duration interventions, heavy operative equipments, electrophysiological monitoring and patient’s cooperation in the operating room. Such an evolution raises a question to anaesthesiologists. Should new fashion neurosurgery unavoidably cause new trends in anaesthesia practice? The answer is obviously yes. In the textbooks of neurosurgical anaesthesia, the classical criteria that characterize the ideal anaesthetic agent include a list of well known properties such as smooth induction, haemodynamic stability, absence of impairment of cerebral autoregulation, decrease of intracranial pressure (ICP) as well as brain relaxation, rapid emergence and neuroprotection. None of them can be discarded today but some should probably draw more attention than others and additional ones should be considered. The new challenge of neurosurgical anaesthesia looks at anaesthetic agents and techniques that provide good operating conditions, minimally affect brain function, are devoid of any interference with electrophysiological monitoring, facilitate new neurosurgical procedures, allow cooperation of the patient during surgery and are associated with rapid and excellent recovery.

Brain relaxation Brain relaxation is considered as a cornerstone in anaesthesia for intracranial surgery, being mandatory in case of intracranial hypertension and of great interest for the surgical approach of the base of the skull in the absence of expanding lesions. It can be considered as a neuroprotective measure in so far as it may reduce surgical compression, local hypoperfusion and cerebral ischaemia. It is of outstanding importance in minimally invasive surgery for the removal of brain lesions through small size craniotomies. Brain relaxation can be achieved by different drugs and techniques including anaesthetic agents, diuretics, hypertonic saline, corticosteroids, muscle relaxation, head elevation, cerebrospinal fluid drainage, and moderate hyperventilation. Propofol and sevoflurane are the most common hypnotic agents in neurosurgical anaesthesia. Propofol has several theoretical advantages over volatile agents by reducing cerebral blood

Anaesthesia for intracranial surgery: general principles

73

volume and ICP and preserving both autoregulation and vascular reactivity to carbon dioxide. During craniotomies for cerebral tumour resections, ICP and cerebral swelling at the opening of the dura have been shown to be lower, and mean arterial blood pressure and cerebral perfusion pressure (CPP, which corresponds to the difference between the mean arterial pressure and ICP) to be higher in propofol-anaesthetized patients compared to patients anaesthetized with isoflurane or sevoflurane (1). Hence, operating conditions have been considered better with propofol than with isoflurane or sevoflurane anaesthesia. Sevoflurane, even when used at subanaesthetic concentrations, increases regional cerebral blood flow and regional cerebral blood volume (2). It may impair dynamic cerebral autoregulation (3). Those effects are also observed with isoflurane and desflurane and are worse with halothane. The detrimental effects of nitrous oxide are well documented (4). Through vasodilatation, it causes a significant increase in CPP and a decrease in zero flow pressure in healthy subjects. This vasodilating effect increases cerebral blood volume, and thus ICP in patients with low intracranial compliance. Therefore, nitrous oxide is not recommended in patients with reduced intracranial compliance. Mannitol is an osmotic diuretic that not only lowers ICP but also improves the intracranial compliance. It may theoretically worsen oedema by crossing a damaged blood brain barrier but is routinely used in trauma patients with diffuse brain injuries. Furosemide is a loop diuretic, which can be administered on its own or in combination with mannitol. It has the advantage of mobilizing oedema fluid more effectively but may be responsible for ionic disturbances. Hypertonic saline solutions are an alternative to mannitol to treat intracranial hypertension and are often combined with hyperoncotic solutions. They are of particular interest in hypovolemic patients. However, caution is advised when high osmolar loads are administered, because they carry increased risks for hypernatremia, hyperchloremic acidosis and damage of the blood brain barrier. Steroids reduce oedema surrounding brain tumours and improve cerebral compliance, but this effect may take several hours. Positioning the patient using a head-up tilt of the table is essential to facilitate cephalic venous drainage and help in relaxing the brain. Hyperventilation is expected to lower intracranial pressure and improve brain relaxation by decreasing cerebral blood volume. However, excessive hyperventilation may compromise cerebral blood flow and brain oxygenation, particularly in case of arterial hypotension. Haemodynamic stability may also play a key role in brain relaxation, particularly in case of disturbed autoregulation. Both high and low blood pressures may negatively affect ICP and CPP. A too high blood pressure increases cerebral blood volume, and hence ICP. A too low blood pressure lowers CPP itself, but is also responsible for a possible autoregulation-driven vasodilatation, which in turn increases cerebral blood volume and ICP. According to several studies, more episodes of arterial hypotension are observed with sevoflurane than with propofol anaesthesia during elective intracranial surgery (5,6). Opiates such as sufentanil and remifentanil are frequently used in combination with the hypnotic agent and help to achieve a stable haemodynamic status. Total intravenous anaesthesia using propofol and remifentanil for craniotomies is well tolerated in normotensive patients but may be associated to some degree of arterial hypertension in hypertensive patients (5). Those episodes of arterial hypertension are usually not

74 General Principle resolved by deepening the level of anaesthesia or analgesia, impede the neurosurgeon’s work and may favour brain bulk in case of disturbed autoregulation. They can often be treated by the intravenous administration of hypotensive drugs but may also be successfully controlled by adding sevoflurane at subanaesthetic concentrations to the basic intravenous regimen (5).

Fluid management Perioperative fluid management in brain-operated patients should aim at preserving CPP and therefore maintaining normovolaemia without adversely influencing ICP. In contrast to systemic capillary membranes, cerebral capillary membranes of the blood brain barrier are impermeable to ions. Normal plasma osmolality, which averages 290 mosmol/kg, is mainly attributable to sodium and its associated anions. In contrast to sodium anions, colloids minimally contribute to the osmolality and the osmotic pressure. Consequently, the fluid movement across capillaries is predominantly governed by the transcapillary ionic gradient rather than the oncotic or colloidosmotic pressure gradient which has negligible effect on brain water content. Cristalloids such as lactated ringer’s solutions, which have an osmolality of 270 mosm/kg, are hypotonic, while 0.9% sodium chloride has an osmolality of 308 mosm/kg. In addition and contrarily to the systemic environment, the cranio-spinal space is closed and can only accommodate for a relatively small increase in intracranial volume, depending on the intracranial compliance. Consequently, isotonic cristalloids are the first choice solutions to be administered in neurosurgical patients. Colloid solutions are often used in hypovolaemic patients but do not prevent the formation of cerebral oedema. The rules for fluid administration differ according to specific situations such as routine craniotomy, traumatic brain injury, diabetes insipidus or still subarachnoid haemorrhage. However, it should never be restricted to such a point that cardiac output and blood pressure might be compromised.

Electrophysiological monitoring Electrophysiological monitoring can be used to assess the depth of anaesthesia but also to localize cortical or subcortical regions and so facilitate the surgical approach of lesions or the placement of deep brain stimulation electrodes. It can also be of interest to control for the integrity of neural structures in patients at risk of ischaemia. In so far as interference with electrophysiological monitoring is concerned, propofol has a considerable advantage over volatile anaesthetics. Inhalational agents significantly decrease the amplitude and prolong the latency of cortical components of somatosensory evoked potentials (SSEP) in a dose-dependent manner (7). Propofol, when compared to isoflurane in patients undergoing spine surgery, causes less suppression of cortical SSEP’s with better preservation of amplitude and less variability at an equivalent depth of anaesthesia (8,9). Regarding motor evoked potentials, isoflurane inhibits intraoperative neurophysiological monitoring to a greater extent than propofol. The later is recommended when motor pathway function is monitored (10). Motor evoked potentials can also be non-invasively elicited using transcranial magnetic stimulation. This

Anaesthesia for intracranial surgery: general principles

75

technique has been recently shown to be feasible during anaesthesia with propofol and remifentanil (11). Propofol has also been successfully used in spinal surgery patients subjected to double-train transcranial electrical stimulation (12). Therefore, although intravenous and volatile anaesthetics affect evoked potential characteristics, the significantly smaller effect of propofol would incite to use this drug rather than inhalational agents when electrophysiological monitoring is required. This choice is still reinforced by the “anaesthetic fade” reflecting a progressive depression of transcranial motor evoked potentials over time at a constant level of anaesthesia (13). Finally, it must be noted that the alpha2-adrenergic agonist dexmedetomidine has been demonstrated to provide a successful sedation without impairment of electrophysiological monitoring during functional neurosurgery (14).

Recovery and awake craniotomies Neurosurgery is more and more focusing on neurological function, which is best monitored by looking at the patient himself. After classical craniotomies, neurological function is clinically assessed when patients emerge from general anaesthesia and recover consciousness. A rapid emergence will allow immediate neurological examination, early detection and efficient management of any potential surgical complication. In a study comparing propofol-remifentanil with propofol-sufentanil for supratentorial craniotomy, the propofol-remifentanil regimen was shown to provide quicker recovery (15). On the other hand, studies comparing sevoflurane and propofol combined to either remifentanil or sufentanil in patients undergoing neurosurgical procedures have shown to be comparable in terms of time to recovery and cognitive functions(6,16). In the absence of any demonstrated difference between propofol and volatile agents regarding the speed and quality of recovery, a lower incidence of nausea and vomiting with propofol should be kept in mind when considering the post-operative comfort of patients, and the risk of intracerebral haemorrhage secondary to vomiting (17). This property of propofol was observed in an ambulatory anaesthesia meta-analysis. Referring to it for neurosurgical patients could sound inappropriate. However, outpatient craniotomy for brain tumour has been reported to be feasible (18). Recovery from anaesthesia must also be as smooth as possible in order to avoid dramatic complications. Cough and haemodynamic bounce may precipitate the occurrence of intracranial bleeding. Again, propofol may be of help in preventing cough upon recovery (19). Prompt use of anti-hypertensive medications to counterbalance the haemodynamic bounce at the time of recovery is also recommended. In particular situations, the neurosurgeon may require the patient’s cooperation during surgery, either for the removal of lesions located close to functional areas of the brain and concerning vision, language or motor areas, or for the checking of the therapeutic efficacy of deep brain stimulations, such as during a surgery for Parkinson’s disease. In those cases, anaesthesia relies on the concept of monitored anaesthesia care and should fulfil the following criteria: sufficient depth of anaesthesia during opening and closure, full consciousness during functional testing, smooth transition between anaesthesia and consciousness, adequate ventilation, immobility and comfort throughout

76 General Principle the entire procedure (20). The drugs that are most frequently employed for an awake craniotomy include local anaesthetic agents, sufentanil or remifentanil, propofol, dexmedetomidine and a2-adrenergic agonists. Propofol is still the first choice hypnotic agent in this indication. Its administration can be performed using a target-controlled infusion technique, guided by a depth of anaesthesia monitor and combined to a remifentanil infusion (21,22). During a propofol-based anaesthesia for the excision of brain tumours located in eloquent brain areas, patients wake up within 5-15 min after stopping the propofol infusion; the airway device may then be temporarily removed and easily replaced thereafter (23) . In a retrospective analysis of 98 patients undergoing craniotomy and requiring intra-operative awake functional brain mapping, combined infusion of propofol and remifentanil has been recognized to provide satisfactory anaesthetic conditions and allow a wake up time of 9 minutes(24). In epilepsy surgery, the cessation of propofol infusion to allow patient awakening has not been found to interfere with electrocorticographic recordings and has been proposed with fentanyl as a safe and useful regimen for awake craniotomy in selected paediatric patients (25). The epileptogenic potency of anaesthetic agents is still a matter of debate. Sevoflurane is known to cause epileptiform patterns in the electroencephalogram such as simple or complex spikes followed by periodic discharges (26). However, no enduring neurological sequelae are evident and a potential morbidity of the epileptogenic electroencephalogram is unproven (26). Regarding propofol, some reports suggest that it can induce disinhibition of the brain and warn about its use in epileptic patients, while others have shown anti-convulsive properties of this drug (27).

Neuroprotection Cerebral ischaemia/hypoxia can occur in a variety of peri-operatives circumstances, and outcome may range from sub-clinical deficits to severe neurological disability and death (28). Mechanisms of ischaemic brain damage and neuronal death vary over time and may prolong for several weeks. Excitotoxicity appears to be a critical event during the opening stages of ischaemia. The afterward-initiated oxidative stress and inflammatory response directly affect neurons but also play a key role in triggering delayed apoptotic neuronal death. Neuroprotection is a therapeutic measure that is initiated before the onset of ischaemia, in order to improve neurological outcome. However, many interventions that were promising in animal models have failed to successfully translate in humans. The capacity of general anaesthesia, as compared to the awake state, to increase neuronal tolerance to hypoxic-ischaemic insults has been established for a long time, although this beneficial effect appears to be transient. The anaesthetic state, while potentially protective, may also mask brain ischaemia that might otherwise be functionally evident in the awake individual. It is well established that the potential neuroprotective effect of anaesthetics is not only related to their capacity to depress cerebral metabolism. Despite promising results in animal models, the absence of human outcome data does not allow stating that volatile or intravenous anaesthetics improve outcome from perioperative ischaemic insults. Nitrous oxide could have potentially neuroprotective properties in animals when given alone at non-anaesthetic concentrations (29). On the contrary, it has been shown to favour delayed ischemic neurologic deficits in patients

Anaesthesia for intracranial surgery: general principles

77

subjected to temporary cerebral arterial occlusion during aneurysm clipping surgery, without affecting long-term outcome (30). Xenon is a new promising anaesthetic agent whose interesting neuroprotective properties shown in animal studies remain to be validated in humans. While oxygen is required to ensure survival of neuronal cells, hyperoxygenation as a measure of neuroprotection is a matter of debate, mainly related to the production of activated oxygen species and free radicals. Hyperventilation, initially proposed to reduce elevated ICP, may impair cerebral perfusion pressure and is no longer recommended at least at a high degree. If hyperventilation has been advocated to reduce cerebral blood volume and ICP, this technique has been shown to increase the volume of ischaemic tissue in brain trauma patients (31). It has also been reported to worsen outcome after head injury and to have no benefit in the context of focal ischaemic stroke. The delivery of oxygen to tissues is also dependent on blood oxygen content and cardiac output. Hence, maintaining them is important for neuroprotection. The threshold for transfusion of red blood cells should therefore be raised up to a level that is unfortunately not precisely defined (32), but it seems reasonable to keep hemoglobin level higher than 8 g dl-1. Although blood glucose is essential for aerobic glycolysis, hyperglycaemia has been proven to worsen ischemic brain injury. Maintaining euglycaemia by insulin treatment could improve outcome in patients at risk of ischaemic insults. It is established from clinical and experimental studies that hyperglycaemia lowers the ischaemic threshold and aggravates outcome in the presence of neurological injury from trauma, stroke and subarachnoid haemorrhage. However, the benefit of intensive insulin therapy should be balanced with the risk of hypoglycaemia, which is detrimental in terms of neurological outcome (33,34). If there is a strong evidence to support tight glycaemic control in critically ill, cardiac surgical and neurologically impaired patients, little evidence is available to guide intra-operative glucose management in neurosurgical patients. In contrast, there is evidence that hyperglycaemia worsens outcome in patients undergoing stereotactic brain biopsy and suffering from severe head injury (35,36). Deep hypothermia is highly neuroprotective but has only few indications in clinical practice. Moderate hypothermia, which has been proven protective in animal studies, has been investigated in different clinical settings and appears to be efficient in only a few specific situations such as out-off-hospital cardiac arrest (37). The multicenter study investigating hypothermia in patients with a subarachnoid haemorrhage consecutive to an intracranial aneurysms rupture yielded disappointing results (38). In contrast, hyperthermia is associated with poor outcome in humans and should be definitely avoided during neurosurgical anaesthesia.

Conclusions In this beginning of the third millennium, modern neurosurgery faces great and fascinating prospects that involve profound modifications in anaesthesia practice. If the main principles of anaesthesia remain the same, important changes are taking place in terms of new objectives to achieve, new management strategies, and new risks (39). The success of this challenge will depend not only on large clinical multicenter studies but also

78 General Principle on a close cooperation between the neurosurgeon, the anaesthesiologist and the paramedical staff.

REFERENCES 1. Petersen KD, Landsfeldt U, Cold GE, et al. Intracranial pressure and cerebral hemodynamic in patients with cerebral tumors: a randomized prospective study of patients subjected to craniotomy in propofol-fentanyl, isoflurane-fentanyl, or sevoflurane-fentanyl anesthesia. Anesthesiology 2003;98:329-36. 2. Kolbitsch C, Lorenz IH, Hormann C, et al. A subanesthetic concentration of sevoflurane increases regional cerebral blood flow and regional cerebral blood volume and decreases regional mean transit time and regional cerebrovascular resistance in volunteers. Anesth Analg 2000;91:156-62. 3. Ogawa Y, Iwasaki K, Shibata S, et al. The effect of sevoflurane on dynamic cerebral blood flow autoregulation assessed by spectral and transfer function analysis. Anesth Analg 2006;102:552-9. 4. Hancock SM, Nathanson MH. Nitrous oxide or remifentanil for the "at risk" brain. Anaesthesia 2004;59:313-5. 5. Bonhomme V, Demoitie J, Schaub I, Hans P. Acid-base status and hemodynamic stability during propofol and sevoflurane-based anesthesia in patients undergoing uncomplicated intracranial surgery. J Neurosurg Anesthesiol 2009;21:112-9. 6. Sneyd JR, Andrews CJ, Tsubokawa T. Comparison of propofol/remifentanil and sevoflurane/remifentanil for maintenance of anaesthesia for elective intracranial surgery. Br J Anaesth 2005;94:778-83. 7. Zhang J, Liang WM. [Effects of volatile anesthetics on cortical somatosensory evoked potential and Bispectral index.]. Zhonghua Yi Xue Za Zhi 2005;85:2700-3. 8. Liu EH, Wong HK, Chia CP, et al. Effects of isoflurane and propofol on cortical somatosensory evoked potentials during comparable depth of anaesthesia as guided by bispectral index. Br J Anaesth 2005;94:193-7. 9. Clapcich AJ, Emerson RG, Roye DP, Jr., et al. The effects of propofol, small-dose isoflurane, and nitrous oxide on cortical somatosensory evoked potential and bispectral index monitoring in adolescents undergoing spinal fusion. Anesth Analg 2004;99:133440. 10. Chen Z. The effects of isoflurane and propofol on intraoperative neurophysiological monitoring during spinal surgery. J Clin Monit Comput 2004;18:303-8. 11. Hargreaves SJ, Watt JW. Intravenous anaesthesia and repetitive transcranial magnetic stimulation monitoring in spinal column surgery. Br J Anaesth 2005;94:70-3. 12. Journee HL, Polak HE, de Kleuver M, et al. Improved neuromonitoring during spinal surgery using double-train transcranial electrical stimulation. Med Biol Eng Comput 2004;42:110-3. 13. Lyon R, Feiner J, Lieberman JA. Progressive suppression of motor evoked potentials during general anesthesia: the phenomenon of "anesthetic fade". J Neurosurg Anesthesiol 2005;17:13-9. 14. Rozet I. Anesthesia for functional neurosurgery: the role of dexmedetomidine. Curr Opin Anaesthesiol 2008;21:537-43. 15. Gerlach K, Uhlig T, Huppe M, et al. Remifentanil-propofol versus sufentanil-propofol anaesthesia for supratentorial craniotomy: a randomized trial. Eur J Anaesthesiol 2003;20:813-20. 16. Magni G, Baisi F, La R, I, et al. No difference in emergence time and early cognitive function between sevoflurane-fentanyl and propofol-remifentanil in patients undergoing

Anaesthesia for intracranial surgery: general principles

17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30.

31. 32. 33. 34. 35. 36. 37.

79

craniotomy for supratentorial intracranial surgery. J Neurosurg Anesthesiol 2005;17:1348. Gupta A, Stierer T, Zuckerman R, et al. Comparison of recovery profile after ambulatory anesthesia with propofol, isoflurane, sevoflurane and desflurane: a systematic review. Anesth Analg 2004;98:632-41, table. Bernstein M. Outpatient craniotomy for brain tumor: a pilot feasibility study in 46 patients. Can J Neurol Sci 2001;28:120-4. Hans P, Marechal H, Bonhomme V. Effect of propofol and sevoflurane on coughing in smokers and non-smokers awakening from general anaesthesia at the end of a cervical spine surgery. Br J Anaesth 2008;101:731-7. Yamamoto F, Kato R, Sato J, Nishino T. Anaesthesia for awake craniotomy with noninvasive positive pressure ventilation. Br J Anaesth 2003;90:382-5. Hans P, Bonhomme V, Born JD, et al. Target-controlled infusion of propofol and remifentanil combined with bispectral index monitoring for awake craniotomy. Anaesthesia 2000;55:255-9. Sarang A, Dinsmore J. Anaesthesia for awake craniotomy--evolution of a technique that facilitates awake neurological testing. Br J Anaesth 2003;90:161-5. Fukaya C, Katayama Y, Yoshino A, et al. Intraoperative wake-up procedure with propofol and laryngeal mask for optimal excision of brain tumour in eloquent areas. J Clin Neurosci 2001;8:253-5. Keifer JC, Dentchev D, Little K, et al. A retrospective analysis of a remifentanil/propofol general anesthetic for craniotomy before awake functional brain mapping. Anesth Analg 2005;101:502-8, table. Soriano SG, Eldredge EA, Wang FK, et al. The effect of propofol on intraoperative electrocorticography and cortical stimulation during awake craniotomies in children. Paediatr Anaesth 2000;10:29-34. Constant I, Seeman R, Murat I. Sevoflurane and epileptiform EEG changes. Paediatr Anaesth 2005;15:266-74. Walder B, Tramer MR, Seeck M. Seizure-like phenomena and propofol: a systematic review. Neurology 2002;58:1327-32. Fukuda S, Warner DS. Cerebral protection. Br J Anaesth 2007;99:10-7. Haelewyn B, David HN, Rouillon C, et al. Neuroprotection by nitrous oxide: facts and evidence. Crit Care Med 2008;36:2651-9. Pasternak JJ, McGregor DG, Lanier WL, et al. Effect of nitrous oxide use on longterm neurologic and neuropsychological outcome in patients who received temporary proximal artery occlusion during cerebral aneurysm clipping surgery. Anesthesiology 2009;110:563-73. Coles JP, Fryer TD, Coleman MR, et al. Hyperventilation following head injury: effect on ischemic burden and cerebral oxidative metabolism. Crit Care Med 2007;35:568-78. Hare GM, Tsui AK, McLaren AT, et al. Anemia and cerebral outcomes: many questions, fewer answers. Anesth Analg 2008;107:1356-70. Prakash A, Matta BF. Hyperglycaemia and neurological injury. Curr Opin Anaesthesiol 2008;21:565-9. Thiele RH, Pouratian N, Zuo Z, et al. Strict glucose control does not affect mortality after aneurysmal subarachnoid hemorrhage. Anesthesiology 2009;110:603-10. McGirt MJ, Woodworth GF, Coon AL, et al. Independent predictors of morbidity after image-guided stereotactic brain biopsy: a risk assessment of 270 cases. J Neurosurg 2005;102:897-901. Jeremitsky E, Omert LA, Dunham CM, et al. The impact of hyperglycemia on patients with severe brain injury. J Trauma 2005;58:47-50. Nolan JP, Morley PT, Vanden Hoek TL, et al. Therapeutic hypothermia after cardiac

80 General Principle arrest: an advisory statement by the advanced life support task force of the International Liaison Committee on Resuscitation. Circulation 2003;108:118-21. 38. Anderson SW, Todd MM, Hindman BJ, et al. Effects of intraoperative hypothermia on neuropsychological outcomes after intracranial aneurysm surgery. Ann Neurol 2006;60:518-27. 39. Dinsmore J. Anaesthesia for elective neurosurgery. Br J Anaesth 2007;99:68-74.

Ⅲ. Neuro-oncology

82

Brain Tumor Surgery in Eloquent Areas ROBERTO ZANINOVICH, MD, PETER BLACK, MD, PhD Department of Neurosurgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA Key words: Brain function, pre-operative techniques, brain mapping, neuronavigation

Introduction Objectives in surgery for cerebral tumors include achieving total resection of the imaged abnormality, reducing neurological deficits from mass effect, minimizing morbidity by preserving functional tissue, and treating intractable tumor-related epilepsy. Achieving these objectives in eloquent areas of the brain requires knowledge of the function of brain in the vicinity of the lesion. Unfortunately, the prediction of function through classical anatomy is insufficient because of the variability of cortical organization, distortion of cerebral topography resulting from mass effect, and functional reorganization due to plasticity. General Concept: The brain is not a computer in which multipurpose hardware is separated from specialized software; each segment of brain tissue appears to have specialized physical machinery for implementing a particular processing function (44). The existence of functionally specialized areas is a logical consequence of the anatomical parcellation of the cortex, or perhaps, the biological necessity for functional specialization imposes anatomical parcellation (44). Whatever came first, any anatomically distinct brain area is probably functionally distinct (40,41,48). The cerebral hemispheres include the cerebral cortex, which consist of four lobes on each side: frontal, parietal, temporal, occipital; the insula; the limbic system; the underlying cerebral white matter; and a complex of deep gray matter masses, the basal ganglia (40,41,48). From a phylogenetic point of view, the cerebral cortex is relatively new. It is well developed in humans and is responsible for “higher” brain functions, including manual dexterity, conscious, discriminative aspects of sensation, and cognitive activity, including language, reasoning, learning, and memory(40,41,48) (Fig-1). Primary Motor Cortex: The primary motor projection cortex, is located in the anterior wall of the central sulcus and the adjacent portion of the precentral gyrus, corresponding generally to the distribution of the giant pyramidal Betz cells (41,48,49) (Fig-2). These cells control voluntary movements of skeletal muscle on the opposite side of the body, with the impulses traveling over their axons in the corticobulbar and corticospinal tracts to the branchial and somatic efferent nuclei in the brain stem and to the ventral horn in the

Brain Tumor Surgery in Eloquent Areas

Fig. 1

Fig. 2

83

84 Neuro-oncology spinal cord (41,48,49). Lesions of the primary motor cortex in one hemisphere result in paralysis of the contralateral extremities (48). Primary Sensory Cortex: The primary sensory cortex for sensory information received from the skin, mucosa, and other tissues of the body and face is located in the postcentral gyrus and is called the somatesthetic area (Fig- 3). From the thalamic radiations, this area receives fibers that convey touch and proprioceptive (muscle, joint, and tendon) sensations from the opposite side of the body (41,48,49). A relatively wide portion of the adjacent frontal and parietal lobes can be considered a secondary sensory cortex because it receives sensory stimuli. The cortical taste area is located close to the facial sensory area and extends onto the opercular surface of the lateral cerebral fissure (41,48). Lesions of the primary somatesthetic area of the cortex result in contralateral sensory disturbances, which are most severe in the distal parts of the limbs (48). The concept of cortical localization with respect to language, dates back to Broca’s reporting two cases with nonfluent aphasia after having autopsy-proven left inferior frontal strokes (10). In 1874, Wernicke added another form of aphasia termed fluent aphasia. These observations began an extensive research in localizing various aspects of language and motor function to specific region of the brain cortex (33,34,48). Brodmann’s naming of brain areas, which is based on cytoarchitectonics, uses numbers to label individual areas of the cortex that Brodmann believed had separate functions from others(33,34,49)(Fig-4). Some of the major cortical areas are:

Fig. 3

Brain Tumor Surgery in Eloquent Areas

85

Fig. 4 Brodmann Area’s Frontal Lobe: 4-Primary Motor Cortex, 6-Premotor Cortex, 8-Frontal Eye Field, 44.45- Motor Speech Area (Broca’s Area), 10-Anterior Prefrontal Cortex, 11-Orbitofrontal Area, 9.46-Dorsolateral Prefrontal Cortex, 47-Inferior Prefrontal Gyrus. Parietal Lobe: 3,1,2-Primary Sensory Cortex, 5.7-Somatosensory Association Cortex, 39-Angular Gyrus, 40-Supramarginal Gyrus, 43-Subcentral Area(between insula and post/precental gyrus). Occipital Lobe: 17-Primary Visual Cortex(Striate Cortex), 18.19Visual Association Cortex. Temporal Lobe: 41-Primary Auditory Cortex, 42-Associate Auditory Cortex, 22-Language Comprehension Area (Wernicke’s Area), 21Middle Temporal Gyrus, 20-Inferior Temporal Gyrus, 37-Fusiform Gyrus, 38-Temporopolar Area (most rostral part of the superior and middle temporal gyri), 52-Parainsular Area (at the junction of the temporal lobe and the insula).

Frontal Lobe: Area 4 is the primary motor area in the precentral gyrus. The motor cortex is organized somatotopically: lips, tongue, face, and hands, represented in order within a map on the lower part of the convexity of the hemisphere (42,49). A distorted figure drawn to represent the body’s motor map in the prefrontal cortex was popularly recognized as the brain’s homunculus (Fig-2). The function of the human brain is far much more complex than this simple figure suggests; however, stimulation of this area causes discrete movements of one muscle or a small group of muscles, which the patient is unable to prevent. The movements are contralateral to the side stimulated except in movements of the palate, the pharynx, the masseter, and often the tongue, in which movements are bilateral because the partially crossed and uncrossed corticobulbar tracts (33,34,42,48,49). Area 6 in the premotor area, contains a second motor map, this appears to have importance for complex movements “setting up” the movement. Other motor zones, including the supplementary motor area, are clustered nearby (49). Area 8, the frontal eye field, is concerned with saccadic eye movements; stimulation

86 Neuro-oncology of this area causes horizontal or oblique conjugate movements to the contralateral side, mediated in part by direct projections to the brainstem (42,48,49). Within the third inferior frontal gyrus, anterior areas 44 and 45 (Broca’s area) are located anterior to the motor cortex, controlling the lips and the tongue. Broca’s area is an important area for speech (10). Stimulation of this area can produce speech arrest without motor movement (10,50). Damage to Broca’s area produces a nonfluent aphasia, conserving intact language comprehension (10,48,49). Anterior to these areas, the prefrontal cortex has extensive reciprocal connections with the dorsomedial and ventral anterior thalamus and with the limbic system (40,41,48,49). This association area receives inputs from multiple sensory modalities and integrates them. The prefrontal cortex serves a set of executive functions, planning and initiating adaptive actions and inhibiting maladaptive ones; prioritizing and sequencing actions; and weaving elementary motor and sensory functions into a coherent, goal-directed stream of behavior (48,49). Damage of this area can result in impulsive behavior and trouble suppressing inappropriate responses and actions (40,41,48,49). Parietal Lobe: The parietal lobe has an important role in motor control by the preparation and redirection of movements and movement intentions (31,40,41,48,49). Areas 3, 1, and 2 are the primary sensory areas, which are somatotypically represented in the postcentral gyrus. This area receives somatosensory input from the ventral posterolateral (VPL) and ventral posteromedial (VPM) nuclei in the thalamus. Movements can be elicited from this region with stimulation. The remaining areas are sensory or multimodal association areas. The inferior parietal cortex abutting the dominant perisylvian sulcus is involved with language comprehension; damage to this area can produce Wernicke’s aphasia, which is characterized by fluent speech with the ability to produce written and spoken words, but the words or the sequences in which they are used, are defective in their linguistic content (40,41,48,49). The nondominant parietal lobe (areas 5-7), has been implicated in spatial orientation, lesions in this area can produce neglect of half of the body and other objects. The dominant angular gyrus of the inferior parietal lobule, is involved with calculation; a lesion of this area can produce Gerstmann’s syndrome (agraphia without alexia, finger agnosia, acalculia, and disorientation for right and left) (40,41,48,49). Occipital Lobe: Area 17 is the striate or primary visual cortex. The geniculocalcarine radiation relays visual input from the lateral geniculate to the striate cortex. Upper parts of the retina (lower parts of the visual field) are represented in upper parts of area 17, and lower parts of the retina (upper parts of the visual field) are represented in lower parts of area 17. Areas 18 and 19 are visual association areas within the occipital lobe (40,41,48,49). Temporal Lobe: Area 41 is the primary auditory cortex and area 42 the associative auditory cortex; together these areas are referred as Heschl’s gyrus (49). They receive input from the medial geniculate. The surrounding temporal cortex (area 22) is the auditory association cortex. In the posterior part of area 22 (posterior third of the superior temporal gyrus, with extensions around the posterior end of the lateral sulcus into the

Brain Tumor Surgery in Eloquent Areas

87

parietal region) is Wernicke’s area, which plays an important role in the comprehension of language; this area is also responsible for both reading and word repetition. Wernicke’s area is connected to Broca’s area by a bundle of nerve fibers called the arcuate fasciculus (41,48,49). The medial temporal lobe, which includes the hippocampus, is related to learning and memory processes. The remaining temporal areas are multimodal association areas (41,48,49). Insula: The insula is a sunken portion of the brain cortex. It lies deep within the lateral cerebral fissure, and can be exposed by separating the upper and lower lips (opercula) of the lateral fissure (40,41,48,49). The insula has connections with the white matter of the surrounding lobes through the subcortical U-fibers that extend through the bases of periinsular sulci, providing a route via which tumors of the insula can spread into the different lobes (40,41,48,49). Limbic System: The term Limbic System referred by Broca in 1878 as the Limbic Lobe, was loosely used to include structures that lie in the border zone between the cerebral cortex and the hypothalamus (9). The cortical components of the limbic system include the cingulate, parahippocampal, and subcallosal gyri, as well as the hippocampal formation (40,41,48,49). Olfaction, memory, and drive-related emotional behavior are related with the limbic lobe. Stimulation can alter somatic motor responses, leading to bizarre eating and drinking habits, changes in sexual and grooming behavior, and defensive postures of attack and rage (40,41,49). Subcortical Pathways: Knowledge of the subcortical pathways for movement, sensation, language and vision are important (14), to preserve brain function during tumor resection (3,7). The white center of the adult cerebral hemisphere contains myelinated transverse fibers, projection fibers, and association fibers(40,41,48,49) (Fig-5). Transverse fibers interconnect the two cerebral hemispheres.The corpus callosum comprises the largest bundle of these fibers, most of which arise from part of the neocortex of one cerebral hemisphere and terminate in the corresponding parts of the opposite cerebral hemisphere (40,41,48,49). The anterior commissure connects the two olfactory bulbs and temporal lobe structures, the hippocampal commissure joins the two hippocampi (40,41,48). Projection fibers, connect the cerebral cortex with lower portions of the brain or spinal cord (40,41,48). The corticopetal fibers (afferent) include the geniculocalcarine, auditory and thalamic radiations and tend to terminate in the more superficial cortical layers. Corticofugal fibers (efferent) proceed from cerebral cortex to the thalamus, brain stem, or spinal cord. Association fibers connect the various portions of cerebral hemispheres and permit the cortex to function as a coordinated whole (40,41,48). These fibers tend to arise from small pyramidal cells in cortical layers II and III. The short association fibers lie beneath the cortex and connect adjacent gyri. The long association fibers are collected into named bundles. The uncinate fasciculus connects the first motor speech area and the gyri on the inferior surface of the frontal lobe with the cortex of the pole of the temporal lobe (40,41). The cingulum connects the frontal and parietal lobes with parahippocampal

88 Neuro-oncology

Fig. 5

and adjacent temporal cortical regions (40,41). The superior longitudinal fasciculus connects the anterior part of the frontal lobe to the occipital and temporal lobes. The inferior longitudinal fasciculus connects the temporal and occipital lobes; finally the fronto-occipital fasciculus connects the frontal lobe to the occipital and temporal lobes (40,41). To summarize, motor and sensory cortex are reliably localized to the precentral and postcentral gyri, respectively in both hemispheres, and are often readily identified on magnetic resonance imaging (MRI). The majority of essential motor neurons are located in the posterior portion of the precentral gyrus adjacent to the central sulcus. There is a wide variability in number and location of essential language sites within individual patients. Language functions are a network of interconnected areas involved in parallel processing to accomplish a task and cannot be accurately defined with anatomic imaging only.

Preoperative Techniques for Brain Mapping Several methods have been described for localizing eloquent areas, becoming an important issue at the time of planning surgery. Methods of pre-operative imaging such as Magnetic Resonance Imaging (MRI), Functional Magnetic Resonance Imaging (fMRI), Single Photon Emission Computed Tomography (SPECT), Positron Emission Tomography (PET), Magnetic Source Imaging (MSI), Diffusion Tensor Imaging (DTI), and intra-operative functional mapping, have all allowed better identification and organization of brain regions. Their reliability must be verified, however. Their use decreases the risk of complications and permanent morbidity following surgical resection. Conventional Computed Tomography (CT): Noncontrast CT scans are often the initial imaging modality for symptomatic patients with unknown brain lesion (53). Most low-grade gliomas do not enhance on CT, and usually are hypodense. In glioblastoma

Brain Tumor Surgery in Eloquent Areas

89

multiforme the low density center represent necrosis; the enhancing ring is cellular tumor: however, tumor cells also extend far beyond the ring. Magnetic Resonance Imaging (MRI): MRI provides the best anatomic detail of any imaging technique. High resolution, multiplanar imaging is essential for neuronavigational systems for operative and radiosurgical planning. MRI with T2weighted images should be obtained in the preoperative phase in order to identify the central or Rolandic Sulcus and the motor strip located within the gyrus directly in front of it; this will allow to predict where the functional motor region is before surgery (4,6). On mid-sagittal MRI scans we can identified posteriorly and superiorly to the termination point of the cingulate sulcus the Rolandic cortex, that is located directly in front of this sulcus; on far lateral images, the inferior to mid portion of the motor cortex is localized by a perpendicular line emanating from the posterior corner of the insular triangle(6). Functional Magnetic Resonance Imaging (fMRI): Functional MRI is thought to detect physiologic activation of the brain by differential tissue oxygenation (24,25,46). When a specific region of the cortex is stimulated, regional cerebral blood flow increases resulting in relative hyperoxemia. As the level of oxyhemoglobin rises, the relative concentration of deoxyhemoglobin falls in the capillaries, venules, and draining veins of the activated cortex. Deoxyhemoglobin is paramagnetic, whereas oxyhemoglobin is not. Gradient-echo, T2-weighted images can detect the difference between concentrations of oxyhemoglobin and deoxyhemoglobin in the hyperoxemic cortex compared with the resting cortex; this detecting method is called blood oxygen level-dependent (BOLD) contrast MRI (24,25). Because of the availability of MRI and the lack of radioactive tracers, the fMRI has had an impact in the diagnosis of lesions in eloquent areas of the brain; however, the precision can be variable, with up to a 20 mm discrepancy with electrical stimulation mapping (52). There are some inherent advantages and disadvantages to fMRI images. Functional MRI can be performed during the same sitting as a standard MRI, and the images can be superimposed on anatomic MRI images. The disadvantages include the need for patient cooperation, and usually takes extra time to obtain functional images that may not be tolerated (19,23). Also, a further concern is that fMRI does not distinguish between the various components of an evoked response and may be affected by a confounding overlap of different brain processes. Positron-Emission Tomography (PET): PET is a technique that can be used to detect functional areas of the brain. PET imaging is based on the use of the O[15] isotope of H2O that localizes noninvasively cortical activation based on changes in cerebral blood flow(46). It does not detect white matter tracts. The breakdown of the blood-brain barrier in combination with the local alteration of cerebral oxygen metabolism and extraction has allowed for the imaging of brain tumors by PET. Brain tumors tend to exhibit increased blood volume, decreased oxygen metabolism, oxygen extraction and blood flow, and increased pH; a relatively low glucose metabolism is observed. 18F fluorodeoxyglucose (FDG) and 11CL-methionine (CMET) radioisotopes have been used to image brain

90 Neuro-oncology tumors by PET, and also to establish their pathological grade and metabolic character (1,20). Increased FDG in brain tumors is thought to be related to the presence of anaerobic glycolysis, and is correlated with survival time in patients with malignant gliomas (21). Areas of increased FDG uptake in low-grade gliomas, may be used to predict malignant evolution or differentiation of these tumors. The malignancy of tumor cells has a positive correlation with increased enzyme activity of the glycolysis system (50,51). CMET/ PET allows a more accurate delineation of high grade gliomas than CT-MRI scanning, and is also a sensitive method for the detection of tumor recurrence (12,26). However, PET requires a sophisticated nuclear medicine team. Magnetoencephalography (MEG): MEG relies on the small magnetic fields that are induced by neuronal electrical currents (dendritic excitatory and inhibitory postsynaptic potentials). Neurons within the sulci elicit electrical currents tangential to the scalp, these currents induce radial magnetic fields; the neurons along the gyral surface produce radial neuronal currents, resulting in magnetic field potentials tangential to the scalp. Abnormal vascular supply may impede detection of a hemodynamic response if tumor is located within functional cortex. The cerebral oscillations in the specific frequencies of the alpha, beta, and gamma bands can be measured by MEG. Desynchronization (attenuation of the oscillation amplitude of a specific frequency) and synchronization (increase of the oscillation amplitude of a specific frequency) are both related to a specific neuronal activity (29). Several MEG studies have suggested that oscillatory changes in the gamma band reflect higher cognitive processes such as language processing, attention, and perception (8,16). Advantages of the MEG system include direct, noninvasive monitoring of neuronal activity in response to a stimulus; the biggest disadvantage is the need for a magnetometer, which is expensive and not widely available. Magnetic Source Imaging (MSI), that coregisters the source localization of functional cortical regions with anatomic MRI, has paved the way for the use of MEG in preoperative planning in patients with brain tumors. Tractography (DTI): Tractography based on MRI Diffusion Tensor Imaging (DTI) is a noninvasive and relatively new approach to map axonal connections through white matter in the human brain (39). Either alone, or with functional MRI, the axonal connections provide important new information to decipher the structure and function of the brain (39). DTI depends on the directional dependence of water molecular diffusion (anisotropic diffusion) to form the basis of mapping axonal tracts in the white matter (39). Diffusion is much faster along the fiber than orthogonal to the fiber. Thus measuring diffusion along different directions in 3D space makes possible assessment of the direction of axonal tracts. The diffusivity of water is affected by the orderly arrangement of neuronal fiber structures such as axonal membranes suggesting that DTI tractography may be limited in areas where the tracts pass through tumor or edema(6). Eigenvectors (orthogonal principal direction of diffusion) can be calculated from the diffusion tensor for each MRI voxel; the primary and associated eigenvalue indicate, respectively, the direction and magnitude of greatest water diffusion. Berger et al 2007 have found that the course of

Brain Tumor Surgery in Eloquent Areas

91

motor pathways beneath the cortex can be revealed by the combination of intraoperative cortical mapping information and DTI of fiber tracks, reducing potential morbidity after tumor resection in an eloquent area. Single-Photon Emission Tomography (SPECT): SPECT is more widely available than PET, despite the recent proliferation of PET and PET/CT scanners, but suffers from decreased resolution and sensitivity (54). SPECT provides physiological imaging with a variety of radiopharmaceuticals such as technetium-labeled agents (i.e., 99mTc-hexamethylpropylene amine oxime [HMPAO], 99mTc-ethyl cysteinate dimer [ECD], and thalium201 [201TI](54). There has been extensive research into the use of [201TI] for brain tumor grading, localization, and survival assessments. Accumulation of [201TI] occurs in viable tissue via the sodium-potassium adenosine phosphatase dependent membrane transport system, as well as the regional blood flow and breakdown of the brain blood barrier. It is important to remark that [201TI] detects 100% of large lesions, but only 22% of small lesions (45). Diffusion MRI: Conventional diffusion weighted images (DWI) characterize the diffusive transport of water using the diffusion coefficient D, which is then calculated into the scalar apparent diffusion coefficient (ADC) map to represent mean diffusivity(54). Increased cellularity is characterized by a low ADC value. Some cystic or ring-enhancing tumors have restricted diffusion with DWI hyperintensity and ADC hypointensity (13,47). Changes detected in mean tumor ADC values after treatment with radiation or chemotherapy have shown diffusion MRI as a biomarker for early prediction of treatment response in patients with high-grade gliomas (6,22).

Intraoperative Techniques for Localizing Tumors Intraoperative Tumor Localization (Visualization): 5-aminolevulinic acid (ALA) has been shown effective in the identification and resection of malignant primary brain tumors (43). High-grade glioma tissue selectively synthesizes highly fluorescent porphyrins when exposed to ALA in a process that reflects tumor cell density and proliferation. Neuronavigation: Computer-assisted image-guided surgery allows the surgeon to localize a tumor more accurately, making tumor resection in eloquent areas of the brain safer and more effective. Most procedures are managed by frameless surgical navigation systems (SNSs), that require imaging data such as CT and MRI scans. These systems use three dimensional digitizers to link a volume of image data with a volume of space on the operating room that includes the intended surgical area. The accuracy of these devices is dependent on the correlation or registration of reference points or shapes in image space to surgical space (6,18). Registration is done point to point through scalp fiducials or facial landmarks (2). Somato-sensory evoked potentials (SSEP): SSEP mapping has more recently been used to identify eloquent areas of the brain, making possible the identification of the primary somatosensory gyrus (and therefore rolandic localization). This can be performed

92 Neuro-oncology under general anesthesia, nitrous oxide combined with thiopental sodium{Pentothal}or low-dose propofol, or in awake patients (intravenous propofol) (17,37). SSEP mapping has an advantage over stimulation mapping, in that seizures cannot be evoked because the cortex itself is not stimulated (36). A peripheral nerve, such as the median nerve, is chosen for stimulation because its robust signal can be recorded at the cortical surface. Other nerves such as the tibial nerve can also be used, depending on which area of the brain we are interested in (medial surface) (36). The stimulus generates a signal that is transmitted to the contralateral somatosensory cortex. Cortical responses have a number of different components designated by their positive (P) or negative (N) polarity with respect to the reference electrode. A strip with multiple electrodes is placed over the assumed pre and post rolandic gyrus, the peripheral stimulus is performed using a bipolar montage, and one looks for phase reversal across the somatosensory gyrus (35). Although SSEPs may be helpful in identifying primary somatosensory gyrus, they do not help localize descending subcortical motor and sensory white matter tracts (35).

Cortical Stimulation Motor and Sensory Mapping Intraoperative cortical mapping leads to the identification of functional brain cortex, including motor and speech areas, making it possible to plan an adequate surgical strategy in order to preserve cerebral function during the resection of tumors or epileptic regions in the brain (5,6,35). Advances in functional imaging, including functional magnetic resonance imaging (fMRI), positron emission tomography, and frameless stereotactic navigational systems, contribute to identify the functional topography of the brain, helping to guide surgical resection (35). Functional localization by cortical stimulation mapping has been performed for more than 40 years (28). Harvey Cushing was the first to perform this procedure in a patient when he stimulated the motor and sensory cortex producing contralateral limb movements and paresthesias (11). Although this technique is reliable, it is often difficult to elicit responses in children or adults who are under general anesthesia. Stimulation mapping of somatosensory cortex requires an awake patient, but motor cortex can be stimulated with the patient under general anesthesia. It should be taken into account that repetitive stimulation at or near the same area, can generate local or generalized seizure activity and subsequent swelling. Therefore, the patient must have adequate serum anticonvulsant levels preoperatively. Measures for terminating intraoperative seizures include the administration of cold irrigation solution (Ringer’s Lactate) applied to the cortex, short term benzodiazepines, and deeper levels of general anesthetic in intubated patients(32). A constant-current, biphasic square wave, 60-Hz, bipolar stimulator set at 2 to 10mA is used to elicit movement, sensation, or both in the awake patient (38). Not only the cortical sensory and motor homunculi can be mapped using this technique, but when stimulating subcortical structures, descending subcortical motor fibers can be identified utilizing the same current values. It is advisable to repeat the stimulation several times during the surgical procedure, in order to be sure that functional areas are not being damaged (35).

Brain Tumor Surgery in Eloquent Areas

93

Localization of Language cortex The goal of surgery in the dominant hemisphere is the preservation of language function, as permanent or even minor language deficits can be of considerable distress to the patient and family (30). Because there is significant individual variability with regard to the number and location of essential language sites, standard anatomic resections do not always spare language function. Although resections in or near functional brain can be made safer by localizing important brain functions, the surgeon must avoid pitfalls causing functional deficits (35). In contrast to mapping rolandic cortex, language cortex mapping depends on electrical blockade of cortical function rather than elicitation of function (27). Most patients, even children as young as 10 years, have little difficulty with the procedure, especially when anesthesia (Propofol) is used during placement of the field block, cranial opening, the majority of the resection, and closure (35,37). A detailed neurological examination of the patient prior to surgery in order to determine language alteration will be useful to obtain a baseline against which to compare intraoperative testing. If speech function, reading, or comprehension is impaired because of the location of the tumor, intraoperative stimulation mapping for language will not be helpful. A patient undergoing language mapping is typically asleep with propofol during surgical approach (6,37), but awake during language mapping. A wide approach is used to ensure that enough cortical sites are available for testing (6). Bipolar stimulation is then used, starting with a current 2 mA, and gradually increasing (0.5 to 1mA) increments with successive stimulations until the after-discharge threshold is determined (35). The current used for language mapping is then set to 0.5 to 1 mA below the after-discharge threshold (35). Each cortical site is checked three times to ensure that there is no stimulation-induced error in the form of anomia or dysnomia. Fifteen to 20 perisylvian sites are selected and marked with small numbered tags before mapping. Sites for stimulation mapping are randomly selected (35). The patient is shown images of simple objects every 2 to 4 seconds; cortical stimulation is applied before presentation of each image, and is continued until there is a correct response or the next image is presented (35). Sites where stimulation produces consistent speech arrest or anomia are considered essential to language function. It has been demonstrated that resections within 10mm of essential language cortex will lead to transient speech impairment (27). Patients with injury to essential language areas will have permanent difficulties (35). Visual Cortex Mapping: The primary visual cortex (area 17) is located in the occipital lobe. It lies in the cortex of the calcarine fissure and adjacent portions of the cuneus and lingual gyrus (49). Visual cortex mapping during surgery can be undertaken by three different methods: 1. Implanted subdural electrodes, visual cortex can be mapped by evoking visual phenomena while stimulating through the subdural electrodes (49). 2. Stimulation of the occipital cortex in an awake craniotomy to allow the patient to report visual sensations (49). 3. Visual evoked potential results during surgery have been decidedly mixed and is

94 Neuro-oncology not widely used (49). Auditory Cortex Mapping: The primary auditory receptive area is located in the transverse temporal gyrus, which lies in the superior temporal gyrus toward the lateral fissure (49). The auditory cortex on each side receives the auditory radiation from the cochlea of both ears, and the projection of the cochlea on the acoustic area (49). Low tones are projected or represented in the frontolateral portion, and high tones in the occipital medial portion of area 41. Low tones are detected near the apex of the cochlea, and high tones near the base. Area 22 that includes Wernicke’s area, is involved in high-order auditory discrimination and speech comprehension (49). It is difficult to do accurate auditory cortex mapping.

REFERENCES 1. Alavi JB, Alavi A, Chawluck J, Kushner M, Prowe J, Hickey W, Reivich M: Positron emission tomography in patients with glioma. A predictor of prognosis. Cancer 62:10741078, 1988. 2. Barnett GH: The role of image-guided technology in the surgical planning and resection of gliomas. J Neurooncol 42:247-258, 1999. 3. Berger MS: Lesion in functional(“eloquent”)cortex and subcortical white matter. Clin Neurosurg 41:444-463, 1994. 4. Berger MS, Cohen WA, Ojemann GA: Correlation of motor cortex brain mapping data with magnetic resonance imaging. J Neurosurg 72:383-387, 1990. 5. Berger MS, Deliganis AV, Dobbins J, Keles GE: The effect of extent resection on recurrence in patients with low grade cerebral hemisphere gliomas. Cancer 74:1784-1791, 1994. 6. Berger MS, Hadjipanayis CG: Surgery of Intrinsic Cerebral Tumors. Neurosurgery 61:279-305, 2007. 7. Berger MS, Ojemann GA: Intraoperative brain mapping techniques in neurooncology. Stereotact Funct Neurosurg 58:153-161, 1992. 8. Braeutigam S, Bailey AJ, Swithenby SJ. Phase-locked gamma band responses to semantic violation stimuli. Brain Res Cogn Brain Res 10:365-377, 2001. 9. Broca P: Anatomic considerations of cerebral convolutions: The great limbic lobe and limbic sulci in a series of mammals[in French]. Rev Anhtropol 1:385-498, 1878. 10. Broca P: Remarks on the seat of the faculty of articulate language, followed by an observation of aphemia[in French]. Bull Soc Anat Paris 36:330-357, 1861. 11. Cushing H: A note upon the faradic stimulation of the postcentral gyrus in conscious patients. Brain 32:44-54, 1909. 12. Derlon JM, Bourdet C, Bustany P, Chatel M, Theron J, Darcel F, et al. [11C]Lmethionine uptake in gliomas. Neurosurgery 25:720-728, 1989 13. Desprechins B, Stadnick T, Koerts G, Shabana W, Breucq C, Osteaux M: Use of diffusion-weighted MR imaging in differential diagnosis between intracerebral necrotic tumors and cerebral abscesses AJNR Am J Neuroradiol 20:1252-1257, 1999. 14. Duffau H, Capelle L, Sichez N, Denvil D, Lopes M, Sichez JP, et al. Intraoperative mapping of the subcortical language pathways using direct stimulations. An anatomofunctional study. Brain 125: 199-214, 2002 15. Duffau H, Velut S, Mitchell MC, Gatignol P, Capelle L. Intra-operative mapping of the subcortical visual pathways using direct electrical stimulations. Acta Neurochir (Wien) 146:265-274, 2004.

Brain Tumor Surgery in Eloquent Areas

95

16. Eulitz C, Maess B, Pantev C, Friederici AD, Feige B, Elbert T. Oscillatory neuromagnetic activity induced by language and non-language stimuli. Brain Res Cogn Brain Res.4:121132, 1996. 17. Gordon E: The neurophysiology of anaesthesia. In Stockard JJ, Bickford RG (eds): A Basis and Practice of Neuroanaesthesia. Amsterdam, Excerpta Medica, 1975, pp 3-46. 18. Helm PA, Eckel TS: Accuracy of registration methods in frameless stereotaxis. Comput Aided Surg 3:51-56, 1998. 19. Hoeppner TJ, Bergen D, Morrell F: Hemispheric asymmetry of visual evoked potentials in patients with well-defined occipital lesions. Electroencephalogr Clin Neurophysiol 57:310-319, 1984. 20. Kaplan AM, Bandy DJ, Manwaring KH, Chen K, Lawson MA, Moss SD, et al: Functional brain mapping using positron emission tomography scanning in preoperative neurosurgical planning for pediatric brain tumors. J Neurosurg 91:797-803, 1999. 21. Kim CK, Alavi JB, Alavi A, Reivich M: New grading system of cerebral gliomas using positron emission tomography with F-18 fluorodeoxyglucose. J Neurooncol 10:85-91, 1991. 22. Moffat BA, Chenevert TL, Lawrence TS, Meyer CR, Johnson TD, Dong Q, et al. Functional diffusion map: A none invasive MRI biomarker for early stratification of clinical brain tumor response. Proc Natl Acad Sci USA 102:5524-5529, 2005. 23. Noachtar S, Hashimoto T, Luders H: Pattern visual evoked potentials recorded from human occipital cortex with chronic subdural electrodes. Electroencephalogr Clin Neurophysiol 88: 435-446, 1993. 24. Ogawa S, Lee TM, Kay AR, Tank DW: Brain Magnetic Resonance imaging with contrast dependent on blood oxygenation. Proc Natl Acad Sci USA 87:9868-9872, 1990. 25. Ogawa S, Tank DW, Menon R, et al: Intrinsic signal changes with sensory stimulation: Functional brain mapping with magnetic resonance imaging. Proc Natl Acad Sci USA 89:5951-5955, 1992. 26. Ogawa T, Shishido F, Kanno I, Inugami A, Fujita H, Murakami M, et al. Cerebral glioma: Evaluation with methionine PET. Radiology 186:45-53, 1993. 27. Ojemann G, Ojemann J, Lettich E, et al: Cortical language localization in left, dominant hemisphere: An electrical stimulation mapping investigation in 117 patients: J Neurosurg 71:316-326, 1989. 28. Penfield W, Jasper H. Epilepsy and the Functional Anatomy of the human Brain. Boston, Little, Brown, 1954. 29. Pfurtscheller G. Event-related synchronization (ERS): An electrophysilogical correlate of cortical areas at rest. Electroencephalogr Clin Neurophysiol 83:62-69, 1992. 30. Pichelmann M, Meyer F. Surgical Management of Lesions in Eloquent Areas of the Brain. In Schmidek H, Roberts D (edts): Operative Neurosurgical Techniques, Indications, Methods, and Results, 5th Edition, Vol 1, pp 696-706, Elsevier Inc, Philadelphia, PA, 2006. 31. Sanes JR, Donaghue JP, Thangaraj V, et al: Shared neural substrates controlling hand movements in human motor cortex. Science 268:1775, 1995. 32. Sartorius CJ, Berger MS: Rapid termination of intraoperative stimulation-evoked seizures with application of cold Ringer’s lactate to the cortex.: Technical note. J Neurosurg 88:349-351, 1998. 33. Schieber MH: Rethinking the motor cortex. Neurology 52:445, 1999. 34. Schmitt FO et al: The Organization of the Cerebral Cortex. MIT Press 1981. 35. Schuster J, Silbergeld D: Motor, Sensory, and Language Mapping and Monitoring for Cortical Resections. In H. Richard Winn (editor): Youmans Neurological Surgery 5th Edition, Vol(2) 2531-39, Elsevier Inc, Philadelphia, Pennsylvania, 2004. 36. Silbergeld DL, Miller JW: Intraoperative cerebral mapping and monitoring. Contemp Neurosurg 18:1-6, 1996.

96 Neuro-oncology 37. Silbergeld DL, Mueller WM, Colley PS, et al: Use of propofol (Diprivan) for awake craneotomies: Technical note. Surg Neurol 38:271-272, 1992. 38. Silbergeld DL, Ojemann GA: The tailored temporal lobectomy. Neurosurg Clin N Am 4:273-281, 1993 39. Singh M, Kwatra A, Wong CW, Prasanna V: Acceleration of fiber tracking in DTI tractography by reconfigurable computer hardware. Conf Proc IEEE Eng Med Soc. 4819-22, 2006. 40. Snell RS. The Cerebrum. In Snell RS (editor) Clinical Neuroanatomy 6th Edition, pp 241274, Lippincott Williams & Wilkins, Baltimore, MD, 2006. 41. Snell RS. The Structure and Functional Localization of the Cerebral Cortex. In Snell RS (editor) Clinical Neuroanatomy 6th Edition, pp 275-295, Lippincott Williams & Wilkins, Baltimore, MD, 2006. 42. Strick PL: Anatomical organization of motor areas in the frontal lobe. In Waxman SG(editor): Functional Recovery in Neurological Disease. Raven, 1988 43. Stummer W, Novotny A, Stepp H, Goetz C, Bise K, Reulen HJ: Fluorescence guided resection of glioblastoma multiforme by using 5-aminolevulinic acid-induced porphyrins: A prospective study in 52 consecutive patients. J Neurosurg 93:1003-1013, 2000. 44. The Chronoarchitecture of the Human Brain. In Frackowiak RJS, Friston KJ, Frith CD, Dolan RJ, Price CJ, Zeki S, Ashburner J, Penny W (edts) Human Brain Function 2nd Edition, pp 201-229, Elsevier Science, London, UK, 2004. 45. Togawa T, Yui N, Kinoshita F, Yanagisawa M, Namba H: A study on thallium-201 SPECT in brain metastases of lung cancer. With special reference to tumor size and tum or to normal brain thallium uptake ratio. Kaku Igaku. 32:217-225, 1995. 46. Tozer KR, Skirboll SL, Winn HR: Monitoring and Mapping of Vision in the Neurosurgical Patient. In H.Richard Winn (editor): Youmans Neurological Surgery 5th Edition, Vol(2) 2541-49, Elsevier Inc, Philadelphia, Pennsylvania, 2004. 47. Tung GA, Evangelista P, Rogg JM, Duncan JA III. Diffusion-weighted MR Imaging of rim-enhancing brain masses: Is markedly decreased water difusión specific for brain abscess? AJR Am J Roentgenol 177:709-712, 2001. 48. Watson C. Functional Neuroanatomy of the Major Sensory and Motor Pathways. In Watson C (editor) Basic Human Neuroanatomy, An Introductory Atlas, 5th Edition, pp 13-68, Little, Brown and Company (Inc), Boston, MA, 1995. 49. Waxman SG: Cerebral hemispheres/Telencephalon. In Foltin J, Lebowitz H, Panton N (eds): Clinical Neuroanatomy 25th Edition, pp 137-154. New York, Large Medical Books/McGraw-Hill, 2003 50. Weber G. Enzymology of cancer cells (first of two parts). N Engl J Med 296:486-492, 1977. 51. Weber G. Enzymology of cancer cells (second of two parts). N Engl J Med 296:54152. Yetkin F, Mueller W, Morris G, et al: Functional MR activation correlated with intraoperative cortical mapping. Am J Neuroradiol 18:1311-15, 1997 53. Young RJ, Sills AK, Brem S, Knopp EA: Neuroimaging of Metastatic Brain Disease. Neurosurgery 57:54-10-54-23, 2005.

97

Venous system in brain tumor surgery TETSUO KANNO, KOSTADIN KARAGIOZOV Department of Neurosurgery, Fujita Health University Key words: brain tumor, surgery, venous drainage, vein occlusion, sinus occlusion, vein sacrifice, sinus sacrifice

I. Introduction Cerebral venous system must be treated with respect in neurosurgery; focusing on the important point whether a vein and a sinus could be sacrificed or not. Generally, it is supposed to be risky to sacrifice venous channels in surgery of acute diseases such as trauma. For instance, the sacrifice of the superior sagittal sinus (S.S.S.) is followed by decrease of flow velocity and marked increase of venous pressure. (Fig.1 in monkey) Then, acute brain swelling occurs with patchy small hemorrhages. (Fig.2 in monkey) However, what will happen in cases of a chronic disease? Generally, they have established a broader venous collateral circulation. In this article, authors will discuss the possibility whether the venous system could be sacrificed in brain tumor surgery.

Fig. 1 Velocity and venous pressure of superior sagittal sinus when bilateral transverse sinuses are occluded. (Monkey)

98 Neuro-oncology

Fig. 2

II. Sinus 1) Superior Sagittal Sinus (S.S.S.) ① unilateral parasagittal meningioma (Fig.3)

Fig. 3

Venous system in brain tumor surgery

99

In lesions without complete occlusion of S.S.S.,the removal can be done rather easily without producing any damage to S.S.S. Pre-operative angiography shows the partial occlusion of S.S.S. (Fig.4).

Fig. 4

The tumor is pulled out from S.S.S. and the sinus wall is sutured. (Fig.5)

Fig. 5

100 Neuro-oncology The bleeding from S.S.S. is well controlled by a slight compression on the proximal side of S.S.S. by the suction tip on a cottonoid by the assistant. (Fig.6)

Fig. 6

This technique does not lead to any significant bleeding from S.S.S. Regarding the bridging vein around the tumor, the authors recommend two small but very useful technical tips. The first is not to open the arachnoid membrane widely and completely. The arachnoid membrane is a protective cover of the bridging vein. [“Don’t make the bridging vein “naked”]. (Fig.7)]

Fig. 7

Venous system in brain tumor surgery

101

The second is to apply a little drop of surgical glue over a surgicel mesh piece, placed around the entrance zone of the bridging vein to S.S.S. This reduces the possibility of rupture and bleeding from this vulnerable site. (Fig.8)

Fig. 8

② bilateral parasagittal meningioma 1) anterior 1/3 of S.S.S. In case of a bilateral parasagittal meningioma located within the anterior 1/3 of S.S.S., the total removal of the tumor with the involved S.S.S. should be done. There is no risk to sacrifice the S.S.S. at this site. 2) mid. 1/3 of S.S.S. (Fig.9,10)

Fig. 9

Fig. 10

102 Neuro-oncology Pre-operative angiograpgy usually shows no patency of S.S.S. (Fig.11)

Fig. 11

Another point for special attention in meningiomas at this site generally is the very high proliferation rate (Mib-1). Therefore, total removal is ideal and it is possible without causing any problems. The cases with long history usually have already developed a very good collateral circulation. (Fig.12) The removal is done as Fig.12 shows.

Fig. 12

Venous system in brain tumor surgery

103

3) posterior 1/3 of S.S.S. (Fig.13,14)

Fig. 13

Fig. 14

The authors are not so aggressive during total removal of meningioma with involved posterior third S.S.S., inferior sagittal sinus and straight sinus. According to the authors experience (Fujita Health University TK series), the proliferation rate of meningiomas at this site is not so high. Rapid recurrence after partial removal has never been experienced. Radiosurgery after partial removal can be the proper method to control them.

104 Neuro-oncology Our strategy for bilateral parasagittal meningioma is shown in Fig.15 and 16.

Fig. 15

Fig. 16

2) Transverse Sinus Transverse sinus can be occluded without causing any increase of venous pressure except in cases when the transverse sinus is not seen on one side on the preoperative Angiography. The outflow can be compensated by the change of the flow direction and velocity. (Fig. 17,18)

Venous system in brain tumor surgery

Fig. 17

Fig. 18

105

106 Neuro-oncology 3) Sigmoid Sinus Sigmoid sinus can be occluded safely. The flow can be maintained by the change of flow direction and collateral flow. (Fig.19,20)

Fig. 19

Fig. 20

Venous system in brain tumor surgery

107

In experiment (monkey), there is no any change on ABSR and É¡-CBF before and after the sacrifice of the Sigmoid Sinus (Fig.21)

Fig. 21

Generally, the effects of sinus occlusion are compensated by the change of velocity and flow-direction except for the acute occlusion of the superior sagittal sinus. (Fig.22)

Fig. 22

108 Neuro-oncology

III. Bridging veins In brain tumor surgery, a surgeon often encounters bridging veins interfering with the goal of his work. If the surgical field and necessary surgical manipulation allows, their preservation is the best option. However, they often obstruct surgical field manipulation. The possibility to sacrifice bridging veins is still controversial, but there some helpful points to mind.. 1) Bridging veins to S.S.S. In anterior interhemispheric approach, only the first bridging vein to S.S.S. can be sacrificed. (Fig.23)

Fig. 23

Bridging veins enter in the sinus more posteriorly should not be divided. Particularly, if retraction is applied over a sacrificed bridging vein, the possibility of hemorrhagic infraction sharply rises to 60% in our experimental study. (Fig.24,25) Once a vein is sacrificed, even staged surgery should be considered, if the outflow compromise became significant

Venous system in brain tumor surgery

Fig. 24

Fig. 25

109

110 Neuro-oncology 2) Vein of Labbé (Fig.26,27) Vein of Labbè is a dangerous vein during surgery. It is already well known that its sacrifice causes hemorrhagic infarctions. This happens mostly in surgery via subtemporal approach, but it can be seen also in a combined petrous approach. However, most of the cases with infarct after its occlusion can recover the accident without suffering severe morbidity.

Fig. 26

Fig. 27

Venous system in brain tumor surgery

111

3) Infratentorial bridging veins (Fig.28)

Fig. 28

In the infratentorial supracerebellar approach, several veins may need to be sacrificed. Bridging veins over cerebellum to the tentorium could be sacrificed in almost of all cases. If the surgeon encounters 3~4 thick bridging veins, he will hesitate which of them ( or all) could be sacrificed. We explored the change of γ-CBF over the cerebellum before and after the temporary clipping of the bridging veins. (Fig.29)

Fig. 29

112 Neuro-oncology In most of the cases, É¡-CBF did not show any significant change, however, in some cases, a single vein clipping showed remarkable decrease of É¡-CBF after clipping. In those cases, the authors tried to preserve the thickest vein, but the surgery became more difficult. (Fig.30)

Fig. 30

Precentral cerebellar vein can also be sacrificed without side effects in most of the cases. However, in cystic pineal lesions it can be preserved.There is one important point regarding the site of division of this precentral cerebellar vein. If coagulated and cut at high position near the confluence, the thrombus may extend to the Rosenthal veins bilaterally and the internal cerebral vein, and that can cause deep venous infarction. (Fig.31,32)

Fig. 31

Venous system in brain tumor surgery

113

Fig. 32

So, when coagulated and cut, it must be done at the very low position, at the most distant point from the confluence. (Fig.33)

Fig. 33

4) Superior petrous Veins Whether or not to divide the petrous veins, encountered during surgery for CP angle and petroclival tumors, is still controversial. In most of the cases it is possible to sacrifice them. However, when there are 3-4 veins or when it is thick, the division and retraction over it, may lead to severe hemorrhagic infarction. Therefore, no retraction surgery is recommended after sacrifice this vein. There is a point to remember in this situation.. If cerebellum is retracted too hard, bleeding from the entrance point to the sinus may occur. With a small surgicel patch and a drop of surgical glue, bleeding can be avoided. (Fig.34)

114 Neuro-oncology

Fig. 34

Once the bleeding occurs, the blood must be drained outside. If the blood goes into the pre-pontine area, you may produce acute brain swelling within just 5 minutes. (Fig.35)

Fig. 35

Venous system in brain tumor surgery

115

Fig. 36

5) Internal cerebral Veins In the interhemispheric, transcallosal interforniceal approach, the tumor must be removed through the space between the internal cerebral veins. A few personal communications regarding the safety of sacrificing internal cerebral vein unilaterally indicated that it is safe. However, there is no sufficient evidence yet. Also no report has appeared about the risks the bilateral occlusion.

V. Conclusion In neurosurgery, there is no more discussion that a surgeon must take care the arteries. But, he also must take care for the venous system. Sacrifice of veins causes disturbance of the venous return that can be followed by increased ICP. Generally, cases in the chronic stage of venous occlusion can tolerate sacrifice more than cases in the acute stage. Collateral circulation develops to some extent in chronic cases. However, it cannot be in all cases. If you sacrifice a vein, the best is not to use retractor. Sometimes, even staged surgery must be considered. The neurosurgeon should learn again and again the importance of preserving veins.

116

Brain Tumours KATHLEEN JOY KHU MD; WAI HOE NG MBBS, FRACS Department of Neurosurgery National Neuroscience Institute, Singapore Key words: primary brain tumor, glioma, astrocytoma, glioblastoma, ependimoma, oligodendroglioma

1.1 Primary Brain Tumours Brain tumours are one of the most common tumours in humans. They are the second most common form of malignancy in children and the sixth to eight most common form of malignancy in adults. Primary tumours of the brain and spine account for less than 2% of all malignancies but are responsible for 7% of the years of life lost from cancer prior to 70 years of age. In childhood, these figures are even more dramatic, with primary brain tumours accounting for 20% of malignant tumours diagnosed before 15 years of age1. The most common form of primary brain tumours are gliomas, which originate from glial cells. There are many forms of gliomas: astrocytomas, ependymomas and oligodendrogliomas are some of the examples.

1.2 Astrocytomas Astrocytomas are the most common gliomas and account for more than 60% of all primary brain tumours2-3. They arise from star-shaped glial cells known as astrocytes. In adults, astrocytomas most often arise in the cerebrum, whereas in children, they occur in the brain stem, the cerebellum, and the cerebrum. Astrocytomas are classified by various grading systems. The most commonly used grading system is the World Health Organisation (WHO) Classification system which separates the astrocytic tumours into two major categories: the diffusely infiltrating astrocytomas and the relatively more circumscribed, specialised variants of astrocytoma (pilocytic astrocytoma, pleomorphic xanthoastrocytoma and subependymal giant cell astrocytoma)4-5 . The diffusely infiltrating group consists of astrocytic tumours which generally infiltrate beyond the macroscopically apparent brain-tumour interface and frequently undergo anaplastic transformation. The more circumscribed group comprises tumours which show limited infiltration into surrounding brain and which infrequently undergo malignant transformation6. Four different tumour grades are classified under the WHO grading system: Grade I to Grade IV. Tumours with nuclear atypia alone are designated Grade II; those which demonstrate mitotic activity in addition to nuclear atypia are Grade III; and neoplasms showing atypia, mitosis, endothelial proliferation and/or necrosis are considered Grade IV. WHO Grade I and II tumours are known as low-grade astrocytomas whereas WHO Grade III and IV tumours are known as high-grade or malignant astrocytomas. The most

Brain Tumours

117

common WHO Grade III astrocytoma is anaplastic astrocytoma, and the most common WHO Grade IV astrocytoma is glioblastoma. High-grade astrocytomas are highly infiltrative and aggressive tumours with marked proliferative potential. Anaplastic astrocytoma may arise from a previously low-grade astrocytoma or may arise de novo as a high-grade astrocytoma, without an identifiable precursor lesion. The progression of anaplastic astrocytoma to glioblastoma influences the prognosis of the disease. The mean time to progression is 2 years and the mean survival is 3 years7-9.

1.4 Epidemiology of Malignant Astrocytoma Malignant astrocytomas are the most common primary brain tumours, constituting over 40% of this group of tumours. The distribution of malignant astrocytoma in the population is age specific. The incidence per 100,000 population of glioblastoma and astrocytoma rises from 0.2 and 0.5 in the under-14 age group to 4.5 and 1.7 respectively after the age of 45 years10. There is a distinct difference in the location of these tumours in the different age groups. In the younger age group (25 years), 90% of the tumours are located in the supratentorial compartment. The incidence of malignant astrocytoma is more common in males compared to females, with a 3:2 ratio11.

1.5 Aetiology In the vast majority of cases, malignant astrocytomas occur sporadically without any identifiable familial tendency or environmental risk factors. Aetiological agents associated with increased incidence of brain tumours include genetic syndromes, familial clustering and environmental factors. Several hereditary and congenital diseases have been identified which have a high preponderance of developing not just astrocytoma but also other brain tumours such as meningioma, haemangioblastoma and vestibular schwannoma. Examples of these diseases include Neurofibromatosis Type 1 (NF-1), Neurofibromatosis Type 2 (NF-2)1213 , tuberous sclerosis14, Von Hippel-Lindau disease (VHL)15-16, ataxia telangiectasia17, and Gorlin and Turcot syndromes18. Other genetic diseases with increased incidence of brain tumours are Li-Fraumeni syndrome19 and the multiple endocrine neoplasia (MEN) type 120. A familial association of astrocytomas, wherein certain families have increased incidence of astrocytomas is also seen21-23. Environmental and other aetiological agents implicated include radiation24, chemicals such as benzene, organic solvents, lubricating oils, acrylonitrile, vinyl chloride, formaldehyde, polycyclic aromatics and phenol25-26.

1.6 Clinical Features The clinical features of high-grade astrocytoma are similar to that of any other spaceoccupying mass lesion in the brain. The signs and symptoms are a function of the location rather than the actual pathology.

118 Neuro-oncology The presentation generally falls into one or more of the following categories: (A) Signs and symptoms of elevated intracranial pressure - This can result from the tumour mass, cerebral oedema or obstructive hydrocephalus, and can manifest as headaches, drowsiness, nausea and vomiting. Classically, the headaches are worse in the morning and are relieved by vomiting, although this relationship is frequently not observed. Clinical signs may include evidence of altered consciousness, papilloedema and 6th nerve palsy. In severe cases of herniation syndrome, decerebration and evidence of 3rd nerve palsy and coma will ensue and the condition will rapidly lead to death if no active emergent therapy is instituted. (B) Focal neurological deficit- This is dependent on the location of the tumour. For instance a tumour located in the speech centre will present with speech disturbance. Examples of focal deficits are cranial nerve deficits, hemiparesis, dysphasia, paraesthesia, visual problems, mental and personality change. (C) Seizures- Brain tumours are a frequent cause of first seizure in adults. Seizure incidence has been reported as 37% in glioblastoma, which is nearly half as frequent as low-grade gliomas27. The most frequently epileptogenic areas are the frontal, parietal and temporal lobes.

1.7 Management and Outcome 1.7.1 Diagnostic Management When the diagnosis of brain tumour is considered, imaging studies should be performed. The initial diagnostic study should be a contrast enhanced computed tomography (CT) or preferably a magnetic resonance imaging (MRI) scan. The identification of any mass lesion, particularly in the presence of contrast enhancement, is highly suggestive of a high-grade astrocytoma. There have been recent advances in neuroradiological techniques in functional and metabolic imaging of brain tumours. The functional imaging techniques of positron emission tomography (PET), single positron emission computed tomography (SPECT) and magnetic resonance spectroscopy (MRS) are able to quantitate various aspects of brain tumour metabolism. Information regarding tumour blood flow, tumour growth rate, degree of oxygenation, potential of hydrogen (pH) and chemical composition such as lactate (Lac), choline (Cho), N-acetylaspartate (NAA), phosphocreatine (PCr), creatine (Cr) and lipids (Lip) can be obtained. Increased glucose uptake and glycolysis has long been associated with malignancy28. The analog of glucose used in PET is 18F-fluoro-2-deoxyglucose (18FDG). Low uptake of 18 FDG has been found to be a good prognostic indicator29-30. SPECT scanning uses radioisotopes utilised in nuclear medicine, namely technetium, gallium, thallium and iodine which act as blood flow markers31. Thallium is highly sensitive for detecting viable tumour and has even been used to grade astrocytomas32-36. Magnetic resonance spectroscopy (MRS) uses the interaction between atomic nuclei and magnetic fields which then detects the resonance spectra of chemical compounds giving a reflection of in situ chemistry. Magnetic nuclear isotopes such as carbon 13, deuterium, fluorine 19, hydrogen 1, phosphorus, sodium 23 or tritium absorb radio

Brain Tumours

119

frequency energy when placed in a magnetic field. The energy absorption results in resonance of the nuclei of the atoms in the chemical compound studied. Different atoms resonate at different frequencies, and this difference in resonance frequency reveals structural information about the brain metabolites such as choline (Cho), creatine and phosphocreatine (Cr), lactate (Lac), myoinositol (MI), lipids (Lip) and NAcetylaspartate (NAA). Elevated Cho/NAA and Cho/Cr ratios have been recognised to be an important malignancy marker for histological grading of astrocytoma and proposed as a non-invasive method to enhance the grading of human brain tumors37-41. Apart from Cho, the concentrations of other metabolites such as Lac, Lip and MI can vary even among tumors of similar histological grade, and these chemicals are the subject of active research42. Metastases and glioblastomas showed definite lipid or lipid/lactate mixture, but anaplastic astrocytomas showed no definite lipid signal41. MRS can also serve as an adjunct in brain biopsy, since targeting areas with elevated lipid content may provide the highest diagnostic yield. Regions with highest lipid content (Lip/Cr ratio) revealed glioblastoma (WHO Grade IV) whereas a region with high Cho/NAA ratio but low Lip/Cr ratio revealed anaplastic astrocytoma (WHO Grade III)43. Functional and metabolic imaging can however only provide a guide to the probability of malignancy, and have inherent problems with false positivity and negativity as well as issues with sensitivity and specificity. It has an important role in target selection to improve diagnostic yield and reduce sampling error in stereotactic biopsy, and also has an important role in the follow-up of patients to help distinguish between tumour recurrence and treatment effects. However, it has severe limitations in definitive diagnosis and can certainly not provide histological proof of the disease.

Fig. 1 MR Spectroscopy of deep seated glioma with elevated Cho and Lipid peaks

120 Neuro-oncology

1.7.2 Therapeutic Management The mainstay of therapy is a combination of surgery, radiation therapy and chemotherapy.

1.7.2.1 Surgery The main role of surgery is to obtain tissue diagnosis. This is crucial as the radiological appearance of malignant astrocytomas may mimic numerous neoplastic and nonneoplastic lesions such as metastatic tumours, lymphoma, bacterial abscess, tuberculosis and cerebral infarction. It is also critical to distinguish between the various forms of primary brain tumours such as oligodendroglioma or ependymoma, as tumour histology will dictate the need for, as well as the type of, adjuvant therapy such as radiation therapy and chemotherapy. Surgery can also significantly and rapidly reduce intracranial hypertension, leading to symptomatic relief and recovery of reversible neurological deficits such as hemiparesis. The role of radical surgical resection of high-grade astrocytomas remains controversial, although there is retrospective data demonstrating increased survival in patients who underwent gross total or even merely subtotal resection, as opposed to biopsy alone44. Surgical options range from a simple stereotactic biopsy, subtotal debulking of tumour or radical resection of tumour. The type of surgery performed is dependent on the following factors: the functional status of the patient, the presence of significant comorbidities, tumour size and tumour location. Stereotactic biopsy utilises the concept of a cartesian coordinate system that identifies a target in three-dimensional space by its relationship to three planes intersecting at right angles to each other. It is especially useful in elderly patients with significant neurologic deficits and medical co-morbidities, who cannot tolerate a lengthy and extensive operation. This procedure is also appropriate for tumours that are small and deep-seated, cases in which aggressive resection is associated with an unacceptable risk of morbidity and mortality. There are currently two types of stereotactic biopsy, frame-based and frameless. Frame-based stereotaxy was developed as early as the late 19th century and involves the application of a rigid stereotactic frame onto the patient’s head, then doing a CT or MRI with the frame in situ. The coordinates of the target are then computed, and the biopsy carried out based on the coordinates. Meanwhile, frameless stereotactic biopsy systems came into being nearly a century later, and enjoyed widespread use only in the 1990s. This procedure does away with attaching a bulky frame onto the patient’s head, and utilises more sophisticated neuronavigation systems and software. Based on the preliminary data, it was found that the diagnostic yield, complication rates and biopsy-related mortality did not differ between the two techniques. Furthermore, it has been shown that frameless procedures incurred a shorter operating time and a shorter hospital stay45-47. For patients with malignant glioma who warrant surgical resection, the aim of surgery should be to remove as much tumour as is safely possible, with maximal preservation of the structural and functional integrity of surrounding structures. The rationale for

Brain Tumours

121

radical resection is listed as follows48-49: (A) Rapid reduction of tumour burden (B) Reduce sampling error associated with a small biopsy (C) Decrease intracranial hypertension (D) Improve neurological function (E) Potentiate adjuvant therapy such as radiation therapy and chemotherapy (F) Possibly improve survival and disease-free progression Radical resection can be hazardous in brain tumour surgery because of the potential neurological deficits that may be incurred with wide margin resection, especially near eloquent cortex. Thus, the main limitation for radical resection is fear of injuring normal brain and causing further neurological deficits. In order to increase the margin of safety as much as possible, various techniques have been developed to identify eloquent cortex, especially language, motor and sensory cortex, with the aim of maximising glioma resection and minimising damage to eloquent brain tissue. These include functional and intraoperative magnetic resonance imaging (MRI), tractography, virtual reality surgery, image-guided surgery and awake craniotomy50. Functional MRI(fMRI) detects changes in cerebral blood flow and oxygen metabolism that reflect neuronal activity, imaging the areas of the brain that are active during task activation51. Thus, it is used to locate eloquent cortices controlling language, motor and sensory functions, enabling the neurosurgeon to avoid these areas and reduce the risk of injury. Diffusion tensor tractography (DTT) identifies the fiber tracts connecting the cortex to the other parts of the brain and spinal cord, specifically the corticospinal and corticobulbar tracts, arcuate fasciculus, optic radiations and callosal projections52. A working knowledge of where the important tracts are in relation to the tumour prevents accidental injury to the tracts leading to neurologic deficits. Virtual reality surgery employs a surgical simulator that takes patient-specific data sets from multiple imaging techniques (CT, MRI, magnetic resonance arteriography and venography) and superimposes the three-dimensional (3-D) reconstructed scan on a live video image of the patient53. This allows the surgeon to study the tumour, blood vessels, skull and the surrounding cortex in a 3-D model, resulting in a greater understanding of the relationship between the tumour and adjacent structures. Neuronavigation and image-guided surgery utilises computer software to triangulate the location of the tumour and more importantly for gliomas, the extent. Intraoperative MRI takes image-guided surgery one step further by allowing repeated acquisitions of the patient’s brain during surgery, thereby correcting for brain shift and providing greater accuracy. This can facilitate resection of any remaining tumour safely with updated visualisation of critical structures50. Awake craniotomy, as the name implies, involves excising the tumour while the patient is awake and responsive. This technique allows the localisation of eloquent areas by cortical stimulation, as well as monitoring of the functional integrity of awake patients while the tumour is being resected54.

122 Neuro-oncology

Fig. 2 fMRI mapping out motor cortex

Fig. 3 Scan showing relationship of tumour to motor cortex and corticospinal tract

1.7.2.2 Radiation Therapy For the last three decades, radiation therapy has remained the single most effective treatment for malignant astrocytoma55-57. All patients with high-grade astrocytomas should be given a course of radiation therapy after surgery if their functional status remains reasonable. The duration and dose of radiation given depends on the functional status of the patient.

1.7.2.3 Chemotherapy The role of chemotherapy is to potentiate and augment radiation therapy. Chemotherapy is markedly limited by penetration into the central nervous system through the blood-brain-barrier, toxicity and chemoresistance to therapeutic agents used.

Brain Tumours

123

Traditional regimens have been based on nitrosourea compounds. In 1970, two separate groups of investigators reported a 40% response rate with 1,3-Bis(2-chloroethyl)-1nitrosourea (BCNU) alone58-59. Other agents used include losmustine (CCNU) and procarbazine. Chemotherapy is conventionally used as an adjuvant after surgery and radiation therapy. The most recent significant advancement has been the "Stupp Regimen" which was published in 2005. This protocol essentially involves the concomitant administration of temozolamide chemotherapy with radiation therapy followed by adjuvant chemotherapy with temozolamide to glioblastoma patients in one arm of study. The patients in the other arm of the study received no concomitant temozolamide with radiation therapy. Results showed that the two-year survival rate was 26.5% with radiation and temozolamide and 10.4% with radiation alone60. Further studies have shown that the benefit is mainly observed in patients whose gliomas have a methylated methylguanine transferase gene promoter and are thus unable to repair some of the chemotherapy-induced DNA damage61. Because of these dramatic results, as well as the fact that temozolamide is an orally administered chemotherapeutic agent with very little adverse effects, this drug is the chemotherapy of choice practised by many units world-wide.

1.7.2.4 Other Modes of Therapy Because of the generally poor survival outcome of glioma patients despite intensive treatment with surgery, radiotherapy and chemotherapy, other treatment modalities and methods of drug delivery have been developed. These include new chemotherapeutic drugs, local delivery of chemotherapy using polymer wafers, immunotherapy and gene therapy. Some of the newer systemic chemotherapeutic agents have been shown to have promising results in the treatment of recurrent gliomas. These include topoisomerase inhibitors such as irinotecan62-63, epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors such as gefitinib64, erlotinib65 and imatinib66, and vascular endothelial growth factor (VEGF) inhibitors such as bevacizumab67. Carmustine-impregnated polymer wafers (Gliadel wafers) are a form of interstitial chemotherapy designed to circumvent the blood brain barrier by delivering the drug directly to the surrounding brain after tumour excision. Westphal et al68 reported that the patients receiving carmustine polymer therapy had a survival advantage over the control group, with a median survival of 13.8 months in the treatment group and 11.6 months in the placebo group. On the other hand, Stupp et al61 analysed that the survival benefit disappeared when only glioblastoma patients were considered, excluding patients with anaplastic histologies. Perry et al69 recommended this treatment as an option for selected patients with newly diagnosed or recurrent malignant glioma where a near total resection is possible, but that further investigations are needed to ascertain the exact patient population that may benefit from this treatment.

1.7.3 Outcome Despite advances in neuroimaging and treatment techniques in the past 30 years, the

124 Neuro-oncology outcome for malignant glioma remains poor. Without treatment, patients with glioblastoma multiforme die within three months. Patients treated with the optimal therapy of surgical resection, radiation therapy and chemotherapy have a median survival of approximately 12 months. Less than 25% of patients survive up to 2 years, and less than 10% do so up to 5 years70. Death is usually due to increased intracranial pressure from tumour progression. Several factors have been shown to influence patient survival. These prognostic factors include age, functional status and administration of radiation therapy71. Younger age and good functional status by way of a higher Karnofsky Performance Score (measure of the ability of the cancer patients to perform activities of daily living) are favorable prognostic factors. Some authors also include chemotherapy60 and surgical resection72 in addition to the other factors.

REFERENCES 1. Andrew H Kaye, Edward R Laws. Historical perspective in Brain Tumors Andrew H Kaye and Edward R Laws eds, 2nd ed. Churchill Livingstone. 2. Zulch KJ (1986). Brain Tumors. Their Biology and Pathology. 3rd ed, Springer Verlag: Berlin Heidelberg. 3. Lantos PL, Vandenberg SR, Kleihues P (1986). Tumors of the Nervous System. In Greenfield's Neuropathology, Graham DI, Lantos PL (eds), 6th ed. Arnold: London. 4. World Health Organisation of Tumours. Pathology and Genetics of the Tumours of the Nervous System (2000). Paul Kleihues, Webster K Cavenee eds. IARC Press. 5. Kleihues P, Louis DN, Scheithauer BW, Rorke LB, Reifenberger G, Burger PC, Cavanee WK (2002). The WHO classification of tumors of the nervous system. J Neuropathol Exp Neurol 61: 215-225; discussion 226-229. 6. Vandenberg S, Lopes M (1999). Classification. In: The Gliomas. Berger M and Wilson C eds. WB Saunders Company. Philadelphia. 7. Watanabe K, Tachibana O, Sato K, Yonekawa Y, Kleihues P, Ohgaki H (1996). Overexpression of the EGF receptor and p53 mutations are mutually exclusive in the evolution of primary and secondary glioblastomas. Brain Pathol 6: 217-224. 8. Kleihues P, Ohgaki H (1999). Primary and secondary glioblastoma: from concept to clinical diagnosis. Neuro-Oncology 1: 44-51. 9. Louis DN, Gusella JF (1995). A tiger behind many doors: multiple genetic pathways to malignant glioma. Trends Genet 11: 412-415. 10. Cohen A, Modan B (1968). Some epidemiologic aspects of neoplastic diseases in Israeli immigrant population. III. Brain tumors. Cancer 22: 1323-1328. 11. Trouillas P, Mennaud G, De The G et al. (1975). Etude epidemiologique des tumeurs primitives du neuraxe dans la region Rhone-Alphes. Rev Neurol 131: 691-708. 12. Blatt J, Jaffe R, Deutsch M, Adkins JC (1986). Neurofibromatosis and childhood cancers. Cancer 57: 1225-1229. 13. Riccardi VM (1991). Neurofibromatosis: Phenotype, natural history, and pathogenesis, 2nd ed. Johns Hopkins University Press, Baltimore, 1-450. 14. Shepherd CW, Scheithauer BW, Gomez MR, Altermatt HJ, Katzmann JA (1991). Subependymal giant cell astrocytoma: a clinical, pathological, and flow cytometric study. Neursurgery 28: 864-868. 15. Seizinger BR (1991). Toward the isolation of the primary genetic defect in von HippelLindau disease. Annals of the New York Academy of Science 615: 332-337. 16. Seizinger BR, Rouleau GA, Ozelius LJ et al (1988). Von Hippel Lindau disease maps to

Brain Tumours

125

the region on chromosome 3 associated with renal cell carcinoma. Nature 332: 269-270. 17. Swift M, Morrell D, Cromartie E, Chambelin AB, Skolnick MH, Bishop DT (1986). The incidence and gene frequency of ataxia-telangiectasia in the United States. American Journal of Human Genetics 39: 573-583. 18. Bolande RP (1989). Teratogenesis and oncogenesis: a developmental spectrum. In: Lynch HT, Hirayama T (eds) Genetic epidemiology of cancer. CRC Press, Boca Raton, Florida, 55-68. 19. Lynch HT, Marcus JM, Watson P, Conway T, Fitzsimmons ML, Lynch JF (1989). Genetic epidemiology in breast cancer. In: Lynch HT, Hirayama T (eds) Genetic epidemiology of cancer. CRC Press, Boca Raton, Florida, 289-332. 20. Daly AF, Jaffrain-Rea ML, Beckers A (2005). Clinical and genetic features of familial pituitary adenomas. Horm Metab Res. 37(6): 347-354. 21. Tijssen CC (1985). Genetic aspects of brain tumors- tumors of neuroepithelial and meningeal tissue. In: Muller H, Weber W (eds) Familial cancer. Karger, Basel, pp 98-102. 22. Maroun FB, Jacob JC, Heneghan WD, Mangan MA, Russell NA, Ali SK, Murray GP, Clarke A (1984). Familial intracranial gliomas. Surg Neurol 22(1):76-78. 23. Challa VR, Goodman HO, Davis CH Jr (1983). Familial brain tumors: studies of two families and review of recent literature. Neurosurgery.12(1): 18-23. 24. Ron E, Modan B, Boice JD Jr, Alfandary E, Stovall M, Chetrit A, Katz L (1988). Tumors of the brain and nervous system after radiotherapy in childhood. N Engl J Med. 20; 319(16):1033-1039. 25. Waxweiler RG, Stringer W, Wagoner, JK Jones J, Falk H, Carter C (1976). Neoplastic risk of workers exposed to vinyl chloride. Annals of the New York Academy of Science. 271: 40-48. 26. Thomas TL, Stewart PA, Stemhagen A, Correa P, Norman SA, Bleecker ML, Hoover RN (1987). Risk of astrocytic brain tumors associated with occupational chemical exposures. A case-reference study. Scand J Work Environ Health. 13(5): 417-423. 27. Penfield W, Erickson TC, Tarlov IM (1940). Relation of intracranial tumors and symptomatic epilepsy. Archives of Neurology and Psychiatry 44: 300-315. 28. Warburg O (1930). The metabolism of tumors. Constable, London. 29. Patronas NJ, Di Chiro G, Kufta C, Bairamian D, Kornblith PL, Simon R, Larson SM (1985). Prediction of survival in glioma patients by means of positron emission tomography. J Neurosurg. 62(6): 816-822. 30. Di Chiro G, DeLaPaz RL, Brooks RA, Sokoloff L, Kornblith PL, Smith BH, Patronas NJ, Kufta CV, Kessler RM, Johnston GS, Manning RG, Wolf AP (1982). Glucose utilization of cerebral gliomas measured by [18F] fluorodeoxyglucose and positron emission tomography. Neurology. 32(12): 1323-1329. 31. Mut F, Bianco A, Nunez M, De Palma G, Touya E (1993). Tc-99m isonitrile uptake in a brain metastatic lesion. Comparison with Tc-99m DTPA using planar and SPECT imaging. Clin Nucl Med.18(2):143-146. 32. Kaplan WD, Takvorian T, Morris JH, Rumbaugh CL, Connolly BT, Atkins HL (1987). Thallium-201 brain tumor imaging: a comparative study with pathologic correlation. J Nucl Med. 28(1): 47-52. 33. Mountz JM, Raymond PA, McKeever PE, Modell JG, Hood TW, Barthel LK, StaffordSchuck KA (1989). Specific localization of thallium 201 in human high-grade astrocytoma by microautoradiography. Cancer Res.15;49(14): 4053-4056. 34. Kim KT, Black KL, Marciano D, Mazziotta JC, Guze BH, Grafton S, Hawkins RA, Becker DP (1990). Thallium-201 SPECT imaging of brain tumors: methods and results. J Nucl Med. 31(6): 965-969. 35. Black KL, Hawkins RA, Kim KT, Becker DP, Lerner C, Marciano D (1989). Use of thallium-201 SPECT to quantitate malignancy grade of gliomas. J Neurosurg. 71(3): 342346.

126 Neuro-oncology 36. Burkard R, Kaiser KP, Wieler H, Klawki P, Linkamp A, Mittelbach L, Goller T (1992). Contribution of thallium-201-SPECT to the grading of tumorous alterations of the brain. Neurosurg Rev.15(4): 265-273. 37. Preul MC, Caramanos Z, Collins DL, Villemure JG, Leblanc R, Olivier A, Pokrupa R, Arnold DL (1996). Accurate, noninvasive diagnosis of human brain tumors by using proton magnetic resonance spectroscopy. Nat Med. 2(3): 323-325. 38. Fountas KN, Kapsalaki EZ, Gotsis SD, Kapsalakis JZ, Smisson HF 3rd, Johnston KW, Robinson JS Jr, Papadakis N (2000). In vivo proton magnetic resonance spectroscopy of brain tumors. Stereotact Funct Neurosurg. 74(2): 83-94. 39. Magalhaues A, Godfrey W, Shen Y, Hu J, Smith W (2005). Proton and magnetic resonance spectroscopy of brain tumors correlated with pathology. Acad Radiol 12:517 40. Veena AN, Ye JR, Xu MS, et al. Multivoxel MR spectroscopic imaging - distinguishing intracranial tumors from non-neoplastic disease. Accepted Annals Academy Medicine. 41. Ishimaru H, Morikawa M, Iwanaga S, Kaminogo M, Ochi M, Hayashi K (2001). Differentiation between high-grade glioma and metastatic brain tumor using single voxel proton MR spectroscopy. Eur Radiol 11:1784-91. 42. Nagar VA, Ye J, Xu M, Ng WH, Yeo TT, Ong PL, Lim CC (2007). Multivoxel MR spectroscopic imaging--distinguishing intracranial tumours from non-neoplastic disease. Ann Acad Med Singapore 36:309-313. 43. Ng WH, Lim T (2008). Targeting regions with highest lipid content on MR spectroscopy may improve diagnostic yield in stereotactic biopsy. J Clin Neurosci. 15(5):502-506. 44. Pang BC, Wan WH, Lee CK, Khu K, Ng WH (2007). The role of surgery in high grade glioma – Is surgical resection justified? A review of the current knowledge. Ann Acad Med Singapore 36: 358-363. 45. Dammers R, Haitsma IK, Schouten JW, Kros JM, Avezaat CJ, Vincent AJ (2008). Safety and efficacy of frameless and frame-based intracranial biopsy techniques. Acta Neurochir (Wien) 150: 23-29. 46. Woodworth GF, McGirt MJ, Samdani A, Garonzik I, Olivi A, Weingart JD (2006). Frameless image-guided stereotactic brain biopsy procedure: diagnostic yield, surgical morbidity, and comparison with the frame-based technique. J Neurosurg 104: 233-237. 47. Dorward NL, Paleologos TS, Alberti O, Thomas DG (2002). The advantages of frameless stereotactic biopsy over frame-based biopsy. Br J Neurosurg 16: 110-118. 48. Sawaya R (1999). Extent of resection in malignant gliomas: a critical summary. J Neuro-Oncology 42: 303-305. 49. Salcman M (2001). Glioblastoma and malignant astrocytoma. In Brain Tumors 2nd edition (eds: A Kaye and E Laws), Harcourt Publishers Ltd, London. 50. Ng WH, Khu K (2007). Neurosurgical strategies to maximise glioma resection with minimal morbidity. Asian Journal of Neurosurgery 1: 9-15. 51. Hardenbergh J (2004). FMRI visualization of multiple functional areas. SIGGRAPH poster. 52. Nimsky C, Ganslandt O, Hastreiter P, Wang R, Benner T, Sorensen A, et al (2005). Preoperative and intraoperative diffusion tensor imaging-based fiber tracking in glioma surgery. Neurosurgery 56(1): 130-138. 53. Kockro RA, Serra L, Yeo TT, Chan C, Sitoh YY, Chua GG et al (2000). Planning and simulation of neurosurgery in a virtual reality environment. Neurosurgery 46(1): 118137. 54. Jaaskelainen J, Randell T (2003). Awake craniotomy in glioma surgery. Acta Neurochir Suppl 88: 33-35. 55. Andersen AP (1978). Postoperative irradiation of glioblastomas. Results in a randomized series. Acta Radiol Oncol Radiat Phys Biol. 17(6): 475-484.

Brain Tumours

127

56. Walker MD, Alexander E Jr, Hunt WE, MacCarty CS, Mahaley MS Jr, Mealey J Jr, Norrell HA, Owens G, Ransohoff J, Wilson CB, Gehan EA, Strike TA (1978). Evaluation of BCNU and/or radiotherapy in the treatment of anaplastic gliomas. A cooperative clinical trial. J Neurosurg. 49(3): 333-343 57. Walker MD, Green SB, Byar DP, Alexander E Jr, Batzdorf U, Brooks WH, Hunt WE, MacCarty CS, Mahaley MS Jr, Mealey J Jr, Owens G, Ransohoff J 2nd, Robertson JT, Shapiro WR, Smith KR Jr, Wilson CB, Strike TA (1980). Randomized comparisons of radiotherapy and nitrosoureas for the treatment of malignant glioma after surgery. N Engl J Med. 303(23): 132358. Wilson CB, Boldrey EB, Enot KJ (1970). 1,3-bis (2-chloroethyl)-1-nitrosourea (NSC409962) in the treatment of brain tumors. Cancer Chemother Rep. 54(4): 273-281. 59. Walker MD, Hurwitz BS (1970). BCNU (1,3-bis(2-chloroethyl)-1-nitrosourea; NSC409962) in the treatment of malignant brain tumor--a preliminary report. Cancer Chemother Rep. 54(4): 263-271. 60. Stupp R, Mason WP, van den Bent MJ, Weller M, Fisher B, Taphoorn MJ, Belanger K, Brandes AA, Marosi C, Bogdahn U, Curschmann J, Janzer RC, Ludwin SK, Gorlia T, Allgeier A, Lacombe D, Cairncross JG, Eisenhauer E, Mirimanoff RO; European Organisation for Research and Treatment of Cancer Brain Tumor and Radiotherapy Groups; National Cancer Institute of Canada Clinical Trials Group (2005). Radiotherapy plus concomitant and adjuvant temozolomide for glioblastoma. N Engl J Med. 10; 352(10): 987-996. 61. Stupp R, Hegi ME, Van den Bent MJ, Mason WP, Weller M, Mirimanoff RO, Cairncross JG (2006). Changing paradigms – an update on the multidisciplinary management of malignant gliomas. Oncologist 11(2); 165-180. 62. Friedman HS, Petros WP, Friedman AH et al (1999). Irinotecan therapy in adults with recurrent or progressive malignant glioma. J Clin Oncol 17: 1516-1525. 63. Batchelor TT, Gilbert MR, Supko JG et al (2004). Phase 2 tudy of weekly irinotecan in adults with recurrent malignant glioma: final report of NABTT 97-11. Neuro-oncol 6: 21-27. 64. Rich JN, Reardon DA, Peery T et al (2004). Phase II trial of gefitinib in recurrent glioblastoma. J Clin Oncol 22: 133-142. 65. Raizzer JJ. Abrey LE, Wen P et al (2004) A phase II trial of erlotinib (OSI-774) in patients with recurrent malignant glioma not on EIAEDs. J Clin Oncol 22: 107s. 66. George D (2001). Platelet-derived growth factor receptors: a therapeutic target in solid tumors. Semin Oncol 28 (suppl 17): 27-33. 67. Stark-Vance V (2005). Bevacizumab and CPT-11 in the treatment of relapsed malignant glioma. Neuro-oncol 7: 369. 68. Westphal M, Hilt DC, Bortey E, et al (2003). A phase 3 trial of local chemotherapy with biodegradable carmustine (BCNU) wafers (Gliadel wafers) in patients with primary malignant glioma. Neuro-oncol 5(2): 79-88. 69. Perry J, Chambers A, Spithoff K, Laperriere (2007). Gliadel wafers in the treatment of malignant glioma. Curr Oncol 14(5): 189-194. 70. Krex D, Klink B, Hartmann C, et al (2007). Long-term survival with glioblastoma multiforme. Brain 130(10): 2596-2606. 71. Ulutin C, Fayda M, Aksu G, et al (2006). Primary glioblastoma multiforme in younger patients: a single-institution experience. Tumori 92(5): 407-411. 72. Laws ER, Parney IF, Huang W, et al (2004). Survival following surgery and prognostic factors for recently diagnosed malignant glioma: data from the Glioma Outcomes Project. J Neurosurg 100(6): 467-473.

128

Current Management of Parasagittal Meningiomas JACQUES BROTCHI MD, PhD, FLORENCE LEFRANC MD, PhD and MICHAEL BRUNEAU, MD Department of Neurosurgery, Hôpital Erasme, Université Libre de Bruxelles, 808, Route de Lennik, B-1070, Brussels, Belgium Key words: parasagittal meningiomas, preoperative evaluation, surgical treatment, cortical veins, radiosurgery, fractioned radiotherapy

Introduction Cushing and Eisenhardt defined parasagittal meningioma as one that fills the parasagittal angle, with no brain tissue between the tumor and the superior sagittal sinus (SSS). Parasagittal meningiomas are tumors arising at the convexity of the hemisphere, just off the midline adjacent to SSS and falx, which may involve one, two or three walls of the SSS with or without occlusion of its lumen. They comprise 21% to 31% of intracranial meningiomas, and the distribution of the meningiomas along the SSS ranged from 14.8% to 33.9% in the anterior third, from 44.8% to 70.4% in the middle third, and from 9.2% to 29.6% in the posterior third of the sinus. Most parasagittal meningiomas are benign tumors that can be cured with surgical treatment. To-day, Magnetic Resonance Imaging (MRI) is the exam of choice to assess the diagnosis and to get all the needed informations before surgery, especially with angiographic sequences (MRA) allowing a precise study of the venous circulation. Indeed, surgery of parasagittal meningioma is mainly surgery and dissection of all the veins that surround the tumor: bridging and parasagittal veins, SSS and collateral channels. MRA will show if the SSS is patent or not, will demonstrate the direction of the venous flow and help good planification of surgical technique. The goal is complete removal of the tumor but quality of life challenges with surgical exploit. The principal evolution of the idea in the last 15 years is towards a less aggressive attitude in the SSS reconstruction.

Clinical Findings Clinical signs are more often generalized seizures that partial ones, headache are frequently observed as well as a focal deficit ie hemiparesia. The discovery of a parasagittal meningioma could also be incidental or more rarely associated with visual loss, behavior disturbance, monoparesis, disorientation and even apathy, dementia or depression. 20% of the patients present manifestations of intracranial hypertension due to occlusion of posterior third of the SSS, torcular or predominant lateral sinus.

Current Management of Parasagittal Meningiomas

129

Pathology The histology is the same as for other locations of meningiomas. Histological classification is performed according to the WHO with frequent benign grade I meningiomas (transitional, meningothelial, psammomatous, angiomatous, fibroblastic, secretory), more rarely grade II (atypical) and rarely grade III malignant meningiomas.

Radiological Diagnosis Parasagittal meningiomas may pose a difficult surgical challenge because venous patency and collateral anastomoses have to be clearly defined for correct surgical planning. Surgery for parasagittal meningiomas requires meticulous preservation of the cortical veins that surround the tumour; thus, knowledge of the relevant venous anatomy would be extremely helpful during surgery. CT scan keeps interest to see the bone invasion by the meningioma but to-day, MRI is the exam of choice to assess the diagnosis and to get all the needed informations before surgery, especially with angiographic sequences (MRA) allowing a precise study of the venous circulation. MRA will show if the SSS is patent or not, will demonstrate the direction of the venous flow and help good planification of surgical technique without the invasive aspect of the digital substraction angiography (DSA). The importance of DSA is obvious only if preoperative embolization being considered but it is an invasive diagnostic procedure with a certain degree of risk, for well-known reasons inherent to the technique. MRA is even more superior to DSA because MRA detects blood flow in all directions simultaneously: - Two dimensional (2D) phase contrast provides a global overview of the SSS and lateral sinuses. - 2D time of flight is more sensitive to see the flow so as the permeability of the anterior part of SSS. - 3D phase contrast sequences improved by injection of Gadolinium obtain optimal visualization of the cortical veins. Moreover, the most important information provided by the MRA (that DSA cannot show) is the information about the flow direction in given vascular structure by special reconstruction procedure using 2D and 3D sequences. As the redistribution of the venous circulation is a frequent and important phenomenon in intracranial occlusive venous diseases of any type (thrombosis, tumoral invasion, etc.), this option is particularly valuable in certain situations because it gives a “pseudodynamic spell” to the otherwise static images. Conventional MRI and MRA are complementary and inseparable. Both types of images are necessary for diagnosis and preoperative classification of the meningioma type. However, MRA has some limits since it is unable to demonstrate the arterial supply of meningiomas. This is why these two exams, DSA and MRA are not conflicted but complementary and DSA useful in certain circumstances as said above. As others, we rarely use DSA in convexity meningiomas unless the tumor is very large and embolization considered. We know that most of the blood supply comes from the meningeal arteries, and these can be occluded in the early steps of the operation during

130 Neuro-oncology the opening of the dura of the convexity.

Surgery General considerations Although cranial base meningiomas have received the most attention in the past two decades, the management of cranial vault meningiomas has also changed significantly. Particular issues include decisions about when to treat, deciding between surgery and radiosurgery, increasing use of image-guided surgery, the understanding of the biology of these tumors, and changing attitudes in the management of the sagittal sinus. The treatment of parasagittal meningiomas is predominantly surgical. Besides major hemorrhage from the scalp, bone, dura, tumor, and sinus, the attachment to the dura, sinus, or falx makes it more difficult to remove the tumor and increases the chance of injury to the normal brain. Radical removal of meningiomas involving the major dural sinuses remains controversial. In particular, whether the fragment invading the sinus must be resected and whether the venous system must be reconstructed continue to be issues of debate. SURGERY OF MENINGIOMAS INVOLVING MAJOR DURAL SINUSES LEAVES THE SURGEON CONFRONTED WITH A DIFFICULT DILEMMA: leave the fragment invading the sinus in place and have a higher risk of recurrence, or attempt a total removal with or without venous reconstruction and expose the patient to a potentially greater operative danger. Some surgeons consider SSS invasion a contraindication for complete resection, and others advocate total resection with venous reconstruction.

Position The patient is placed in a supine, lateral or prone position according to the location of the meningioma (anterior third, middle third or posterior third of the SSS). If the attachment to the dural convexity is wide, it is important to position the head in such a way that the meningioma is located in the upper part of the operative field. This provides an excellent view of the tumor and sinus with good control of blood loss. In anterior third, the patient is supine with the head slightly elevated. In middle third, the patient is placed in a lateral position with the head well elevated so that the scalp over the center of the tumor is uppermost. In posterior third, we prefer to place the patient in a three-quarter prone position with the tumor below the midline. That position takes advantage of gravity by allowing the brain to fall away from the midline which avoids unnecessary brain retraction. This is of special interest when the connection with the falx is significant, or when the attachment to the dural convexity is small.

Scalp Incision The head is supported by a three-point skeletal fixation. A bicoronal skin incision is used for the anterior third of SSS (for better cosmetic results). For the other localizations of meningioma along the SSS, a horseshoe shape incision is used, extending

Current Management of Parasagittal Meningiomas

131

approximately 2 cm across the midline. The pericranial tissue is always carefully preserved for dural reconstruction.

Bone flap That is one of the major steps of the procedure. If not well done, surgery may be very difficult and bleeding out of control. A free parasagittal bone flap, centered over the tumor (2 to 3 cm posterior and 2-3 cm anterior to the tumor boundaries) is performed with several burr holes just over the midline in type I and beyond the midline in all other types except in special cases described below. Indeed, it is necessary to have a perfect control over the SSS in most of the cases. However, great care should be taken to avoid injuring the controlateral dura and subsequent veins. The bone cuts across the midline are performed last, when the other bone cuts have already been made. So, if there is any suspicion of air embolus, the bone flap can be quickly elevated. Cautious preoperative study of the diploic veins led the surgeon to preserve those important anatomic networks in designing and cutting the bone flap to avoid injuring those vital pathways channels when SSS occluded. The dura mater and the bone are carefully separated because of the presence of draining veins and the possible invasion of the dura or the bone by the meningioma to avoid cortical damage. If there is an extensive bone invasion, it may be safe to do a crown of burr holes around the involved bone and to let it attached to the tumor. It is therefore possible to elevate the around bone flap without any risk of cortical damage. Invaded bone is removed by rongeurs or high speed drill. After the bone flap elevated, venous bleeding from the SSS may be controlled by Gelfoam and gentle pressure with cotton strips. The dura is held along the craniotomy with suture placed from the dura into burr holes drilled around the bone flap. That immediately stops extradural bleeding.

Dural opening The tumor can often be palpated through the dura which is cut around the tumor about 5 to 10 mm from the meningioma. It is safe starting the dural incision opposite to the SSS, then curving laterally, along the anterior and posterior limits of the tumor as a horse-shoe shape preserving the SSS and the draining cortical veins. The dura is not used to retract the tumor as described in the convexity meningioma because of the danger to damage the bridging draining veins which often are very close to the tumor, sometimes lying over it in the parasagittal area. The dura is never opened on the opposite side except in type V with an occluded SSS. Sagittal cutting of the dura is performed after most of the tumor has been dissected from the brain.

Tumor removal The dissection of the meningioma from the adjacent brain is carefully made under the control of the microscope. It is important to stay close to the tumor capsule. When the

132 Neuro-oncology tumor is extra-pial, it may be separated by forceps and cottonoid strips. When the lesion is subpial, it is important to clearly define the plane with adjacent brain. Again, the use of cottonoid is useful and safe. The key is to work circumferentially from the periphery to the midline, from the surface to the depth, with meticulous coagulation and division of all the small blood vessels between the brain and the tumor capsule. As a blood vessel on the surface of the meningioma is encountered, it must first be identified and if the vessel supplies to the tumor (and not the brain) it may be coagulated on the tumor and cut. Most of the arteries may be freed from the tumor at the condition to locate the small lateral feeding branches, which are coagulated and divided. Sometimes, it may be useful to make an internal debulking with the ultrasonic aspirator or the cautery loops in very firm meningiomas, to get easier access to the separation plane to dissect. As few retraction as possible of the adjacent brain should be made, since most of those tumors have close relationship with the motor area. Another key point is the absolute preservation of all the bridging veins which should be separated from the tumor and not injured to avoid neurological deficit. Nevertheless, it may be sometimes necessary to reconstruct a bridging vein. For example, a large rolandic vein may be totally embedded by the meningioma and its separation without wall injury is not always possible. Smooth dissection will preserve it, but sometimes, a tear may happen. The injury should be cautiously repaired. We did it twice with good clinical and radiological results. In the case of sinus repair (see below), we take the advantage of a venous graft collateral branch which is end to end sutured to the stump of the bridging vein. Working in a clean field without blood contamination is also the ideal way to safely dissect all the vessels. When SSS is not concerned, surgery may end by cutting the dura parallel to the midline after separation of the parasagittal veins which corbel the tumor. Then, the tumor may be completely removed.

Closure Dural closure is performed with the pericranial tissue that has carefully been preserved for dural reconstruction. It is important to do a watertight suture. If there has been a bone invasion by the meningioma, a piece is removed and replaced by an acrylic cranioplasty. Otherwise, the bone flap is replaced and secured with modern bone clips.

Debates: How to manage the superior sagittal sinus involvement We review here some of the major series recently published In 2001, Marc Sindou reports a series of 80 meningiomas (72 of the sagittal sinus, 5 of the transverse sinus and 3 of the torcular) for which gross total removal was perdormed in 73 cases, and a venous reconstruction attempted in a majority. In total, 70 patients (87.5%) had a good outcome and resumed their previous activites. There was a permanent neurological deficit in seven (8.7%) due to infarction secondary to injury of central veins. Three patients (3.6%) died from brain swelling; all with meningioma totally occluding the sinus and in whom resection was achieved without sinus reconstruction. There were two recurrences (2.5%) in this series which has a mean follow-

Current Management of Parasagittal Meningiomas

133

up of 8.5 years. The conclusion is to favour, whenever possible, total removal with sinus reconstruction, using a patch for meningiomas with partial sinus invasion and a venous bypass for those with total sinus occlusion. DiMeco et al (2004), on the basis of their results on 108 patients, conclude that if the sinus is partially invaded, it can be opened to obtain as complete a resection as possible and to attempt to preserve the patency of the sinus. If the sinus is obstructed, the portion of the sinus involved can be resected completely. In both situations, extreme care is vital to preservation of cortical veins, which may offer important collateral drainage. With their approach, good results are achieved and it is not necessary to reconstruct the sinus. More recently, Caroli et al (2006) describe 328 patients with meningiomas that were infiltrating the SSS. All the patients were surgically treated. Patients with meningioma involving the anterior segment of the sinus underwent total sinus resection. Patients with meningioma that was infiltrating the middle and posterior third of the sinus had a complete sinus removal if the dural sinus was completely obliterated by meningioma and incomplete removal if the sinus was not occluded. The tumor removal was grade I according to Simpson's grading system in 193 cases and grade II or III in the remainder. The SSS was totally resected in 215 patients and marginally resected in 113. The tumor reappeared in 38 patients. The number of re-interventions did not affect clinical outcome. The extent of removal significantly influenced the regrowth or recurrence rate. Their results suggest that the risks of aggressive surgery, with sinus reconstruction, may be avoided and conservative surgery for meningiomas that are infiltrating but not obliterating the superior sagittal sinus may be a reasonable choice. Colli et al. (2006) based on 53 patients, opte to perform a subtotal resection when the posterior two thirds of the sinus are significantly invaded by a tumor and they never interrupt and reconstruct the sinus. By contrast, Sindou and Alvernia (2006) reviewed 100 consecutive patients who had undergone surgery for meningiomas originating at the SSS and were in favor of a complete tumor removal, including the portion invading the sinus. They showed that the subgroup of patients without venous reconstruction displayed statistically significant clinical deterioration after surgery compared with the other subgroups (p = 0.02). According to their result, they concluded that venous flow restoration seems justified when not too risky. It was clearly explained that some of the patients with complete occlusion of the SSS caused by tumor invasion could deteriorate after complete resection of the neoplasm, whereas others do not. It is highly possible that in most of such cases, the neurological impairment after surgery is caused by sudden interruption of the collateral pathways of the venous blood flow, particularly through diploic and subcutaneous veins. In the series of 242 parasagittal meningiomas reported by Chernov (2007), which were surgically treated at the Department of Surgical Neurooncology of the Russian Polenov Neurosurgical Institute (St. Petersburg, Russia), involvement of the extracerebral veins into collateral cerebral venous outflow was identified in 56% of cases. Their preoperative functional evaluation was done by assessment of the electroencephalography (EEG) before and after circular compression of the scalp at the level of the glabella and inion. If at the time of testing significant changes of the bioelectrical activity were observed, it was

134 Neuro-oncology considered a result of the functionally important involvement of the subcutaneous veins in the cerebral venous outflow. In such cases the surgical treatment was electively performed in two stages: at first, carefully planned skin incision and craniotomy were done, whereas the tumor was resected 2 to 3 weeks later. It is evident that such a test could not be helpful for evaluation of the collateral venous pathways through the diploic veins. Therefore in all cases intraoperative neurophysiological monitoring using scalp EEG was routinely used. A decrease in the amplitude or an increase in the interhemispheric asymmetry of the bioelectrical activity after craniotomy, which were observed in 14.9% of cases, were considered a result of decompensation of the collateral venous blood flow, and also served as an indication for division of the surgical procedure into two stages. It was expected that a staged surgical procedure in cases of meningioma involving the SSS could provide an opportunity for gradual adaptation of the brain for the new conditions of the venous outflow. It might be of interest that in some of these cases mild-tomoderate impairment of the neurological symptoms developed after the first stage of the surgical procedure and steadily regressed thereafter. Patients with coexistent complete occlusion of the SSS and bone invasion by the tumor were in particular risk of neurological deterioration after surgery. Whereas the noncontrolled and nonrandomized nature of the cited studies could not permit to clarify the specificity and sensitivity of the described methods for prediction of the outcome after resection of meningiomas involving the SSS, a zero mortality rate among 242 surgically treated cases can make the proposed treatment strategy reasonable. Nevertheless, additional studies are definitely needed for evaluation of the different options for possible prediction of the outcome after resection of tumors with involvement of the major dural sinuses.

Our surgical strategy based on sinus invasion We categorized parasagittal meningiomas using a sinus invasion classification scheme created by Bonnal and Brotchi and after simplified in accordance with our current surgical policy (Fig 1).

Fig. 1 Classification of parasagittal meningiomas in 5 categories. Type I: Meningioma attached only to the outer surface of the sinus wall. Type II: Meningioma entering the lateral recess of the SSS. Type III: Meningioma invading one SSS wall. Type IV: Meningioma invading two walls of a still patent sinus. Type V: Meningioma spreading over the midline, invading the three walls with occlusion of the SSS.

Current Management of Parasagittal Meningiomas

135

In types I and II, SSS grafting is not necessary. In type I, the attachment of the tumor to SSS can be coagulated with bipolar forceps and peeled until a clean, shiny dural surface is obtained, even by resection of the external dural sinus layer. In type II, the lateral angle recess is progressively opened and a meningioma bud is very often removed. Then, as soon as cleaned, the opening is closed by a 6.0 nylon suture at the level of the angle while taking care not to narrow the SSS. In types III and IV, one or two sinus walls are invaded by the meningioma. Total resection implicates the reconstruction of one or two walls with an autogenous vein graft. But the question to-day is the absolute need to do it as we shall discuss below. In type III, one lateral sinus wall is invaded. This wall, as well as the intraluminal extension of the tumor, can be excised and replaced by a vein graft taken from the saphenous vein. When the wall resection is small, it may be possible to suture a simple piece of vein with a suitable tension, the two other sinus walls remaining sufficiently distant and stable to maintain the SSS lumen open. In type IV, two sinus walls are invaded. The SSS is not completely occluded. The third wall, which is sound, receives venous inflow from the opposite side, since SSS drains both hemispheres. It would be very dangerous to excise all three walls and to interrupt SSS. If a grafting is deciding, it should have been prepared on the table at that stage. Then, the intrasinusal portion of the meningioma may be excised as well as the two invaded sinus walls, without touching the sound third wall, to preserve the rolandic vein inflow from the controlateral cortex. The vein graft, which consists of a segment of the internal saphenous vein, is longitudinally opened and prepared at the size of the sinus walls to be replaced. The internal valves of this vein determine the direction of blood flow. Great care should be taken not to place the graft in the wrong direction. Atraumatic and very regular suture keeps watertight closure. When there is a rolandic vein opening in the third wall, it should be left opened and blood loss is grossly controlled by digital compression by the assistant on both opening of the SSS. When there is no controlateral main vein entering the sinus, the technique described by Hakuba is very helpful. It consists of using a shunting extracorporeal tube, ballooned at each end, and inserted into SSS beyond each extremity of the tumoral invasion. That avoids air embolism or unnecessary bleeding. Then, it is important keeping the venous graft open by attaching it by a broad suture to a piece of dura, the extremities of which being sutured under tension to the dural edges and hinged to the bone. That keeps the triangular anatomical shape of the SSS which is mandatory for patency. Local perfusion of saline-heparin solution is maintained during the suture and platelet antiaggregates are given in an oral way before and after surgery. Type V parasagittal meningioma is discussed below.

What do we do? Present indications of SSS reconstruction. Since 1978, we have other diagnostic tools like MRI which is more accurate to define and to show the tumor but especially to follow the precise evolution of a residual meningioma. It is now well- established that a meningioma is a slight growing tumor. Even if the resection is not totally performed, the residue can remain stable during years. And even if a regrowth occurs it can be of a few millimeters per years with a progressive

136 Neuro-oncology collateral circulation and progressive sinus thrombosis avoiding any neurological deficit. The interest of gamma knife radiosurgery has also been reported (see below). With these new informations and even if we showed thirty years ago the feasibility of a sinus reconstruction, we keep in mind that this surgery is not without risk and needs experienced neurosurgeons. Furthermore, we observed two recurrences at 10 and 13 years after complete tumor removal and total SSS grafting, which raised in our mind the question of radical resection with SSS grafting. Both cases had postoperative patent graft which came to late secondary occlusion due to tumor recurrence without any neurological deficit. This is why we reviewed our position on the indication of the sinus reconstruction which is not a surgery without risk. The reconstruction of the sinus wall becomes rarely performed in our center now. If a parasagittal meningioma invades the sinus wall without occlusion of the SSS (types III and IV), we remove the extrasinusal meningioma and we follow the residue by annual MRI and MRA. If the residue regrows, a complementary radiosurgery is performed in the aim to control the tumor before any second surgery. We try no to touch the sinus anymore until its complete obliteration. SSS receive blood from both hemispheres, but also from other dural, cortical or diploic veins. Because of these anastomotic networks, clinical signs are frequently absent after SSS obstruction. Progressive gradual obstruction of the SSS may lead to a well developed collateral venous pathway that should mandatory be kept intact in parasagittal meningioma surgery. That is what we do now with Type V meningiomas. Preoperatively, we carefully study the venous pathway, the venous flow direction, we search for all collateral venous channels, and we do a pre-operative venous chart and planning to preserve all those channels at surgery. By doing so, we may safely remove completely a Type V parasagittal meningioma, with the occluded SSS, without the need of a venous graft. But great care is taken to keep intact all the collateral venous by-passes that have developed with time, shunting the occluded SSS without any neurological warning.

Morbidity and mortality The routine use of microsurgical techniques has reduced the surgical mortality, but the postoperative morbidity and rate of recurrence for these tumors remain high. Operative mortality for resection of parasagittal meningiomas varied from 1.85% to 12.3%. Mortality is associated significantly with old age, is greater for patients with tumor located in the middle third of the sinus, and did not depend on the extension of the resection. Di Meco et al reported a decrease from 3.7% to 1.85% in operative mortality after the introduction of microsurgical techniques in the treatment of patients with parasagittal meningiomas operated on from 1986 to 2001. Causes of death among the patients of the larger series were predominantly cerebral swelling, followed by pulmonary embolism, postoperative hematoma, cardiac failure, and bronchopneumonia. Predominance of cerebral swelling in patients with tumor in the middle third of the SSS probably indicates surgical damage to cortical veins closely related to the tumor. The operative mortality (first 30 days after surgery) observed in the series of Colli et al. (2006) was 1.9%, the surgery related mortality was 5.7%, and the overall mortality rate in the follow-up was 26.4%. Surgery-related deaths were caused by circulatory chock in 1 patient, by pulmonary infection in another, and by pulmonary

Current Management of Parasagittal Meningiomas

137

embolism in a third patient. In the follow-up, 8 deaths were not related to tumor and 3 patients with grade III meningiomas died because of progression of the disease. In this study, all neurologic deterioration occurred in patients with tumors located in the middle third of the SSS. As these complications are generally caused by interruption of the SSS or by lesion of cortical veins draining to the SSS, every effort should be exerted to preserve the bridging veins located over or anterior or posterior to the tumor to avoid surgical interruption or inducing thrombosis of such veins which could lead to regional venous infarction with delayed neurologic deficit. Moreover, neurological deficits are cumulative when multiple resections are required.

Recurrence Recurrence of parasagittal meningiomas occurs in 7.9% to 29%, and it is dependent on the extent of the follow-up (5%-17.7% at 5 years and in 14.4%-24% at 10 years). Many factors are reputed to influence the recurrence of all intracranial meningiomas. For some of them, this role is incontestable, but for others it is controversial. Most authors agree that recurrence rates for patients with atypical or malignant meningiomas are greater than for patients with WHO grade I, and this is also true for patients with parasagittal meningiomas as demonstrated by Di Meco et al and by Colli et al. There was no patient with grade III tumor without recurrence at the 5-year follow-up. Among the subtypes of WHO grade I intracranial meningiomas, psammomatous tumors with a high density of calcification rarely recur, and the angioblastic meningiomas, even if they are separated from the hemangiopericytomas, seem to have a markedly high rate of recurrence. Delay in recurrence is variable among patients with intracranial meningiomas and it has been detected early after the routine use of follow-up CT scans. Recurrence has been reported as more than half occurring by the end of the fourth/fifth year. Simpson, in 1957, established the recurrence of meningiomas according to the extent of resection, and since then other authors have confirmed his findings. Recurrence at 5 years after tumor plus dural resections ranges from 5% to 16%, after total tumor resection from 11.9%to 18%, and after partial resection of the tumor from 14% to 41.9%. In the Colli series, age did not interfere with the recurrence rates. Females had less recurrence than males for all patients. The extent of resection influenced the decrease in recurrence rates for all patients with parasagittal meningiomas and for patients with WHO grade I meningiomas. Considering all patients, patients with tumors located in the anterior third of the SSS had significantly less recurrence than patients with tumors located in the middle and posterior third of the SSS. By contrast, Di Meco et al reported no interference of tumor location along the SSS. The extent of invasion of the SSS (Bonnal and Brotchi grades I-IV vs grades V-VIII) influenced positively the rates of recurrence for all patients and for patients with WHO grade I meningiomas. Despite a high recurrence rate in all the follow-up (32.7%), and the better RFS curves for radical resection in the Colli series, if we consider that the recurrent rates were 12% at 5 years and 16% at 10 years and that more than half of the recurrences occurred in patients with WHO grades II and III tumors, Colli et al (2006) consider that their results justify a less aggressive policy in relation to the resection of the SSS.

138 Neuro-oncology

Relevance of radiotherapy The study by Rosenberg et al. (2009), is one of the few studies reporting the outcomes for malignant meningioma patients according to recent definitions. Their results are consistent with existing reports of the overall poor outcomes for atypical and malignant meningioma patients. From the available data, surgical resection followed by radiotherapy and salvage therapy can lead to extended survival.

Radiosurgery Stereotactic radiosurgery has become an important primary or adjuvant minimally invasive management strategy for patients with intracranial meningiomas with the goals of long-term tumor growth prevention and maintenance of patient neurological function. In patients with smaller tumors ( 6 cm) The olfactory tracts are usually compressed or destroyed by a large tumor (> 6 cm), and there is less room for dissection due to brain edema. If the basal cisterns cannot be reached to release CSF, the tumor is debulked with high power coagulation. Devascularization of the tumor as early as possible is especially important in large OGMs. An ultrasonic aspirator is seldom used, as the combined repetitive movement of suction and bipolar forceps achieves the same result with less bleeding. Mechanical retractors are not used to prevent long-lasting compression of the already edematous frontal lobe brain. As the debulking progresses, the remaining tumor is brought down away from the brain tissue towards the cribriform plate. Monopolar coagulation is seldom used since the current spreads much wider than the bipolar coagulation, with the risk of additional damage to adjacent neural structures. Attachments to ACAs and to the optic chiasm Large OGM can be attached in the posterosuperior part to the ACAs. Sharp dissection is used to detach both ACAs from the tumor (Fig. 4A, 4B). All arterial branches coming from the ACAs should be preserved, but some of the small branches supply the tumor directly and must be coagulated (Fig. 4C). The posterior part of the tumor can be attached to the supraclinoid carotid arteries and the optic nerves or chiasm. High magnification, sharp bipolar forceps (Malis +20, +25), and sharp dissection are necessary when working in this area, with the aim of preserving all of the small perforators, including the blood supply of the chiasm.

158 Neuro-oncology

Fig. 4 Large OGM operated on through right LSO. Axial (A) and sagittal (B) views of T1-contrasted MRI showing the posterior attachment of the tumor to the ACA (white arrows); C: Coronal T2-sequence showing the small perforator coming from the ACA to the tumor (dark arrows). D: Axial view of T1contrasted MRI, 3 months after tumor removal.

Hyperostosis Once the tumor has been completely removed, the dura of the anterior skull base is carefully coagulated with bipolar forceps (Simpson grade 2). In patients with long life expectancy, the dura near the origin of the tumor is stripped off with either monopolar or knife modality, and the hyperostotic bone is drilled away (Simpson 1) (1). Infiltration of ethmoid sinuses In patients with a good prognosis and long life expectancy, the tumor infiltrating the ethmoid sinuses must be removed. This requires a larger bone flap, resection of the crista galli, and partial transection of the basal portion of the anterior margin of the falx. A highspeed diamond drill is used to open the ethmoid sinuses. Unless the bony window is sufficiently large, some tumor may go unnoticed behind the corner. The bony defect can be closed with the help of pericranial tissue, autologous fat, muscle, or fascia grafts. Fibrin glue, used widely over the last 20 years, has proved to be an important adjunct in preventing postoperative CSF leakage.

Differences between LSO, pterional, bifrontal, frontoorbital approaches The pterional approach (23-25) has the advantage to spare the SSS and frontal cortical veins, to avoid compressing the frontal lobes, and simultaneously to allow the surgeon to visualize the anterior circulation, the basal feeders, and the optic nerve and chiasm. This approach does not allow preservation of the contralateral olfactory nerve (6, 10). The middle fossa extension of the pterional approach is unnecessary in removal OGM and only the frontolateral part of the approach is needed. The LSO approach has been used by the senior author (J.H.) in 66 consecutive OGM patients operated on since 1997. In this approach, the sylvian fissure remains at the border of the craniotomy and can be easily opened if necessary, as our experience with MCA and other anterior circulation even posterior circulation aneurysms shows (11-13). The LSO approach provides the same advantages as the classic pterional approach, but is less traumatic and faster. CSF release after opening the basal cisterns gives space to visualize the necessary neurovascular structures. In large meningiomas, debulking of the tumor enables

Microsurgical treatment of Olfactory Groove Meningiomas

159

dissection of the A2 branches and the posterior part of the tumor. Compared with the bifrontal approach, the LSO approach ha less exposure of the frontal lobes with less surgical manipulation or frontal lobe retraction, the anterior third of the SSS is preserved with the frontal draining veins with less risk of frontal infarction and increased edema; only rarely the frontal sinus can be opened, requiring much less reconstruction at the end of the procedure. In a recent surgical study, about OGM, comparing a simple frontolateral approach (very similar to our LSO approach) with the bifrontal approach, three patients in the bifrontal group died due to postoperative brain edema. No deaths occurred in the frontolateral group. The authors concluded that the anterior third of the SSS should be preserved during OGM surgery, and this is better achieved with the frontolateral approach (16). Al-Mefty and Babu recommended a unilateral frontal craniotomy with orbital osteotomy to prevent bifrontal retraction, leading to possible mental changes (1, 2). A recent anatomical study compares the surgical exposure of the pterional, orbitozygomatic, and minisupraorbital approaches. The authors conclude that the minisupraorbital approach with removal of the orbital rim gives a similar surgical view as the pterional and orbitozygomatic approaches (8). In our experience, inclusion of orbital osteotomy is not necessary or beneficial when the LSO approach is used to remove OGMs.

Surgical complications Postoperative CSF leakage CSF leakage can happen especially in those tumors infiltrating the ethmoid sinus. Our policy is first to use the lumbar drainage for a few days and if the fistula still persists we perform a recraniotomy with plastic of the skull base by using autologous fat or fascia lata. Six of our 66 patients (9%) developed CSF leakage from the nose, three of them with tumor infiltration into the ethmoid sinuses. Four of the six patients were treated with lumbar drainage for a few days. The other two patients required a fascia lata graft. Hydrocephalus This is a rare surgical complication and we had only two patients with postoperative hydrocephalus, one received a ventriculoperitoneal shunt. Postoperative hematoma Especially in large meningioma a postoperative hematoma can happen. We had only one patient with large meningioma who presented postoperative hematoma in the resection cavity requiring evacuation.

Clinical complications Anosmia New postoperative anosmia unrelated , in our experience, with the tumor size is a frequent clinical complication after OGM surgery. New postoperative anosmia appeared in six patients (9%). All six tumors were of either hard (n=3) or medium (n=3) consistency. Three of these six patients had tumor infiltration into the ethmoid sinuses. Olfactory function improved in two patients, both of them with a medium-sized tumor extending more to the right side.

160 Neuro-oncology Visual deficit Postoperative visual deficit is in our experience unrelated to the tumor consistency and size. In our experience five patients developed new deficits. Two were large, soft tumors. Of the other three, one was small, one was medium, and one was large; all had a medium consistency. No patients with a hard tumor developed new postoperative visual deficits. Of the 14 patients with a preoperative visual deficit, three improved after surgery and 11 remained unchanged. Surgical mortality No surgery-related mortalities occurred. Four patients died of unrelated cause during the follow-up.

Conclusion We believe that all size of OGM can be safely removed by using a small LSO approach.

REFERENCES 1. Al-Mefty O : Tuberculum sella and olfactory groove meningiomas. In Sekhar LN,Janecka IP:Surgery of Cranial Base Tumors New York:Raven Press 1992. 2. Babu R, Barton A, Kasoff SS: Resection of olfactory groove meningiomas: technical note revisited. Surg Neurol 44:567-572, 1995. 3. Bakay L,Cares HL: Olfactory meningiomas.Report on a series of twenty-five cases. Acta Neurochir 26:1-12, 1972. 4. Bassiouni H, Asgari S, Stolke D: Olfactory groove meningiomas: functional outcome in a series treated microsurgically. Acta Neurochir (Wien) 149:109-121, 2007. 5. Cushing H,Eisenhardt L: Meningiomas: Their classification, regional behaviour, life hystory, and surgical end results. Springfield, IL, Charles C Thomas 1938. 6. Dare AO, Balos LL, Grand W: Olfaction preservation in anterior cranial base approaches: an anatomic study. Neurosurgery 48:1142-5; discussion 1145-6, 2001. 7. El Gindi S : Olfactory groove meningioma: surgical techniques and pitfalls. Surg Neurol 54:415-417, 2000. 8. Figueiredo EG, Deshmukh V, Nakaji P, Deshmukh P, Crusius MU, Crawford N, Spetzler RF, Preul MC: An anatomical evaluation of the mini-supraorbital approach and comparison with standard craniotomies. Neurosurgery 59:ONS212-20; discussion ONS220, 2006. 9. Gerber M, Vishteh AG, Spetzler RF: Return of olfaction after gross total resection of an olfactory groove meningioma: case report. Skull Base Surg 8:229-231, 1998. 10. Hassler W,Zentner J: Pterional approach for surgical treatment of olfactory groove meningiomas. Neurosurgery 25:942-5; discussion 945-7, 1989. 11. Hernesniemi J, Romani R, Niemela M: Skull base and aneurysm surgery. Surg Neurol 30-31, 2009. 12. Hernesniemi J, Ishii K, Niemela M, Smrcka M, Kivipelto L, Fujiki M, Shen H: Lateral supraorbital approach as an alternative to the classical pterional approach. Acta Neurochir Suppl 94:17-21, 2005. 13. Hernesniemi J, Dashti R, Lehecka M, Niemela M, Rinne J, Lehto H, Ronkainen A, Koivisto T, Jaaskelainen JE: Microneurosurgical management of anterior communicating artery aneurysms. Surg Neurol 70:8-28; discussion 29, 2008. 14. Lang J: Clinical anatomy of approaches. Bifrontal and frontolateral approach. Lang J (ed): Skull Base and Related Structures. Stuttgart: Schattauer, 1995, pp 97-112.

Microsurgical treatment of Olfactory Groove Meningiomas

161

15. Nagy L, Ishii K, Karatas A, Shen H, Vajda J, Niemela M, Jaaskelainen J, Hernesniemi J, Toth S: Water dissection technique of Toth for opening neurosurgical cleavage planes. Surg Neurol 65:38-41; discussion 41, 2006. 16. Nakamura M, Struck M, Roser F, Vorkapic P, Samii M: Olfactory groove meningiomas: clinical outcome and recurrence rates after tumor removal through the frontolateral and bifrontal approach. Neurosurgery 60:844-52; discussion 844-52, 2007. 17. Ojemann RG : Meningiomas:Clinical features and surgical management. In Wilkins RH,Rengachary SS:Neurosurgery New York:McGraw-Hill 1985. 18. Olivecrona H,Urban H: Uber Meningeome der Siebbeinplatte. Brun's Beitr Klin Chir 161:224-253, 1935. 19. Solero CL, Giombini S, Morello G: Suprasellar and olfactory meningiomas. Report on a series of 153 personal cases. Acta Neurochir (Wien) 67:181-194, 1983. 20. Spektor S, Valarezo J, Fliss DM, Gil Z, Cohen J, Goldman J, Umansky F: Olfactory groove meningiomas from neurosurgical and ear, nose, and throat perspectives: approaches, techniques, and outcomes. Neurosurgery 57:268-80; discussion 268-80, 2005. 21. Tonnis W: Zur Operation der Meningeome der Siebbeinplatte. Zentralblatt fur Neurochir 1:1-7, 1938. 22. Turazzi S, Cristofori L, Gambin R, Bricolo A: The pterional approach for the microsurgical removal of olfactory groove meningiomas. Neurosurgery 45:821-5; discussion 825-6, 1999. 23. Yasargil MG: Surgical Approaches. Yasargil MG (ed): Microneurosurgery. Microneurosurgery of CNS Tumors. New York: George Thieme Verlag Stuttgart, 1996, pp 29-68. 24. Yasargil MG: Meningiomas. Yasargil MG (ed): Microneurosurgery. Microneurosurgery of CNS Tumors. New York: Thieme, 1996, pp 134-185. 25. Yasargil MG: General Operative Techniques. Yasargil MG (ed): Microneurosurgery. New York: Thieme-Stratton, 1984, pp 208-233.

162

Surgical Treatment of Complex Tumors of The Anterior Skull Base: The Transbasal Extended Approach MIGUEL A. ARRAEZ Chairman, Dept. of Neurosurgery Carlos Haya University Hospital. Malaga. Spain Key words: Anterior fossa, Skull base surgery, Transabasal extended approach

INTRODUCTION The anterior skull base is a very difficult and challenging field for the neurosurgeon. It comprises different anatomical compartments and structures (bone, brain, meningeal layers, vessels, cranial and peripheral nerves, nasal cavity and paranasal sinuses, orbit). Tumors arising at the anterior skull base may growth in a very capricious manner invading the surrounding structures. The skull base surgery philosophy (cranial and facial osteotomies) is extremely useful to expose and resect those lesions insofar as these approaches allow for the adequate and simultaneous exposure of the different compartments. After resection, the skull base reconstruction is of outstanding importance to restore anatomy, function and to avoid complications.

ANATOMICAL CONSIDERATIONS The proper knowledge of the relevant anatomy of the anterior skull base is very important. The frontal, sphenoidal and ethmoidal bones compose the anterior fossa floor. The anterior midbase corridor is located between both orbits, and is a very frequent origin of skull base neoplasms arising at the anterior fossa and upper nasal cavity. The anterior midbase is very close to nasal/paranasal contaminated cavities: Sphenoid sinus, ethmoid sinuses and frontal sinus. The postero-lateral aspect of the anterior midbase is in close vicinity with the optic canals and optic nerves. The orbit is a very important and eloquent structure at the anterior skull base. Sometimes is distorted and invaded by the lesion. The removal of the tumor must be followed by reconstruction of the orbital walls (usually medial wall and/or orbital roof) to avoid cosmetic problems and diplopia. The orbital apex is another area of great concern, as sometimes is also involved. Optic nerve, carotid artery and oculomotor nerves can be affected. In some cases of mailgnacy, orbital exenteration must be carried out when the orbital content is involved. The optic nerve is very frequently affected by tumors at the anterior skull base. It can be compressed at the intradural, intracanal or intraorbital segment. The carotid artery and cavernous sinus are the lateral limits of the transfrontal

Surgical Treatment of Complex Tumors of The Anterior Skull Base: The Transbasal Extended Approach

163

midline approaches. The carotid artery can be damaged during surgery at the posterior vertical portion (C5 segment). Inferiorly, hypoglossal nerves are the lateral limits. The sellar region can be also approached trough the subfrontal/transfrontal route, although we have to take into account that the posterior clinoids are a blind area for this approach. The body of the sphenoidal bone can be reached until the lower third and anterior foramen magnum. The clival approach requires careful frontal lobe retraction. The anterior skull base bone is bearing both frontal lobes. The duramater is adherent to the bone, and very thin at the cribiform plate, anterior clinoids and lesser sphenoid wing. These areas are very difficult to be sutured after tumoral resection, and are very prone to postoperative fistula. The inferior aspects of both frontal lobes (rinencephalon and olfactory nerves) are in close contact with the anterior skull base. The tumor usually damages the olfactory anatomy because of cribiform plate involvement.

DIAGNOSTIC EVALUATION OF THE ANTERIOR SKULL BASE NEOPLASMS The diagnostic preoperative evaluation is of paramount importance to define the anatomical extension of the tumor. Only after careful preoperative evaluation can we adequately choose the most appropriate approach and also plan the reconstruction of the anterior skull base. This is especially important in reoperation cases. Magnetic Resonance Image with and without gadolinium is necessary to assess the extent and neuroradiological characteristics of the lesion. It helps to guess the degree of vascularization and outline the invasion of brain parenchyma, orbit and nasal/paranasal structures. CT scan with bone algorithm (axial and coronal images) is of great help to establish the involvement of the bone. The current equipments provide really useful 3D reconstructions that incorporates tumor, bony and vascular anatomy. Angiography must be done if high vascularization is suspected. If so, preoperative embolization must be tried. The vascularization of the tributaries from external carotid artery can be embolized, unlike the component from the internal carotid artery and its branches. Intraoperative direct embolization is sometimes done, but the risk increases as the vascularization comes from the internal carotid circulation.

SURGICAL APPROACHES: THE TRANSBASAL-TRANSFRONTAL EXTENDED APPROACHES The current standard approach to remove complex lesions at the anterior skull base includes a bifrontal craniotomy with the addition of a supraorbital rim bilateral osteotomy. This philosophy has received many denominations (transbasal, extended subfrontal, frontal transbasal, standard subfrontal). Transbasal extended approach is a term that can give honor to the initial description (Derôme, transbasal approach) incorporating also the concept of the extended added osteotomy (Shekhar, Sen). From this concept of bifrontal craniotomy and orbital rim osteotomy, different approaches can

164 Neuro-oncology be devised in a modular fashion. The transbasal extended approach can provide adequate exposure for lesions growing at the anterior midbase with involvement of spheno-ethmoidal bone and adjacent dural/intradural subfrontal region. The paranasal sinuses and upper nasal cavity can be also reached. Both orbits are easily exposed. The clivus can be approached even to the lower third (anterior foramen magnum) with the lateral limits of the cavernous sinus and hypoglossal nerves (lateral and inferiorly). When the lesion is beyond the above mentioned lateral limits, a modified procedure (antero-lateral resection) is needed. When the tumor is malignant and is also affecting the maxillary region, a combined transfacial approach (craniofacial resection) is indicated, that can even incorporate orbital structures amenable for resection.

SURGICAL STEPS Positioning The patient is positioned in supine position, with the head neutral and slightly extended to ease the retraction of frontal lobes. Spinal drainage, manitol and dexametasone are used to relax the frontal lobes.

Scalp and soft tissue A bifrontal-coronal incision far behind the hairline is done, reaching both preauricular creases. It precludes from unaesthetic scar visible at the forhead and provides exposure to get a very long and broad based pericraneal flap for reconstruction of the skull base and/or dural plane (Figure 1). The temporal fascia must be preserved, and also the supratrochear and supraorbital arteries at the orbital rim, as they supply the pericraneal and miofascial frontal flap. The supraorbital nerve and artery are not damaged if the supraorbital foramina is opened carefully (small punch or chisel). The detachment of the soft tissue must expose the glabelar region and orbital rim.

Fig. 1 Exposition of the cranial vault after scalp incision (A) beyond the hairline to avoid frontal scars. This exposition also provides a broad pericraneal flap (B).

Surgical Treatment of Complex Tumors of The Anterior Skull Base: The Transbasal Extended Approach

165

Craniotomy and skull base osteotomies A bifrontal craniotomy is carried out. Usually five burr holes (Figure 2) are needed (two at both sides of the sagital sinus, one in midline besides the frontal sinus and one lateral burr hole at each side behind the frontozygomatic suture, that is hidden under the temporal muscle). The release of CSF (spinal drainage) helps to gentle retract both frontal lobes. Both orbital roofs are exposed after careful detachment of the duramater. The periorbital layer is dissected from the medial and superior orbital walls. The anterior base is cut accordingly with the extension of the tumor. If the olfaction is yet preserved, an osteotomy of the cribiform plate including the adjacent nasal mucosa can avoid postoperative anosmia. If already present, both olfactory rootlets and duramater are cut at the level of the anterior ethmoid, and the duramater sutured. The biorbital rim ostetomy is done with a different extension and anatomical variation according to the need for exposure of the lesion (Figure 3).

Fig. 2 A: Bifrontal craniotomy and fronto-orbital osteotomy. The bifrontal craniotomy is done with the aid of five burr holes: two at both sides of the sagital sinus, one in midline besides the frontal sinus and one lateral burr hole at each side behind the zygomatic process of the frontal bone. B: Transillumination through the anterior fossa (left orbit) showing the weak areas where the osteotomy can be more easily done at the roof of the orbit.

Fig. 3 Lines of cutting at the anterior skull base to carry out the fronto-orbital osteotomy. Superior (A) and anterior (B) view. In C we can see the orbital bandeau obtained after cutting through the white line of image A. In D we can see a fronto-ethmoidorbital flap after cutting through the yellow line of osteotomy.

166 Neuro-oncology

Tumor resection The tumor is resected according to the anatomical involvement, extension and biological characteristics. The midbase corridor is easily exposed and removed. Malignant tumors can be excised “en bloc” if possible. The sphenoidal and ethmoidal extension can be removed, as well as the nasal invasion (Figures 4 and 5). Optic nerve compression is a frequent finding in anterior skull base neoplasms (Figures 6 and 7). The optic canals must be skeletonized following any bony landmark not distorted by the tumor (i.e, entering the sphenoid sinus or following the medial orbital wall from an anterior to posterior direction). The carotid artery can be exposed drilling very carefully the lateral wall of sphenoid sinus. The intradural extension of the tumor needs dural opening and careful microsurgical exposure and dissection from relevant structures. Complex cases can include extradural and intradural involvement of carotid arteries and optic nerves (Figure 8).

Fig. 4 Recurrent low grade sarcoma. Nasal cavity, paranasal sinuses and intracranial-intradural invasion (A and B). The tumor is seen through the left nostril.

Fig. 5 Intraoperative view after tumoral resection (A) of the case of figure 5. Arrows are pointing out both orbits. The tumor has been removed from the midbase. DP= Dural patch (cadaveric liofilized dura). Postoperative MRI (B) showing radical resection. The bright signal (arrow) corresponds with autologous fat. This patient was one of the early cases done by the author. The patient developed extradural infection. Now, fat is not used anymore near aerial cavities, and dural reconstruction is always done with autologous pericranium or fascia.

Surgical Treatment of Complex Tumors of The Anterior Skull Base: The Transbasal Extended Approach

167

Fig. 6 16 years old boy with progressive loss of vision. CT scan (A) showing recurrent osseus hemangioma, operated on two years ago. Intraoperative view (B) after resection and bilateral extradural optic nerve decompresion. Left optic nerve and carotid artery (arrow, C) after drilling. Postoperative CT scan (D) shows no remaining tumor.

Fig. 7 12 years girl with headache and right blindness. RMN showing a very invasive neoplasm at of presumed bony origin the anterior fossa (B). Both carotid arteries are encased by the tumor. Intraoperative picture showing optic nerve decompression. The tumor was removed subtotally. Histological diagnosis: Osteosarcoma

168 Neuro-oncology

Clivectomy and posterior fossa involvement The retraction of both frontal lobes allows for exposure of the region of the pituitary gland, sphenoid sinus and clivus. The tumor involving the clivus (Figure 9) can be removed. If the tumor penetrates the clival dural plane, the posterior fossa can be also reached (Figure 8). We have to take into account that the posterior clinoid region is considered a blind area (dead angle) for the microsurgical approach. If the tumor is

Fig. 8 Simultaneous extra and intradural invasion of the neurovascular structures at the anterior fossa. Recurrent malignant meningioma

Fig. 9 Clival chordoma. Sagital MRI showing the “hour-glass” growing at the preclival area and posterior fossa (A, B, C). The tumor is located between both carotid arteries and cavernous sinus at the midbase (D).

Surgical Treatment of Complex Tumors of The Anterior Skull Base: The Transbasal Extended Approach

169

Fig. 10 Patient of figure 9. Extended subfrontal approach. Surgical steps: 1) Removal of the preclival portion. 2) Drilling of the clivus (A). 3) Removal of the posterior fossa component. Reconstruction with pericraneal graft (PG). MRI one month after surgery, showing that the brain stem compression has disappeared (B) and after three years (C). The pericraneal graft has lost some volume.

intermingled with the sphenoidal bone (as chordoma does), the drill with diamond burr is very helpful (Figure 10). Laterally, the cavernous sinus and the hypoglossal canal are the limits of the clivectomy.

Modifications of the technique. Complementary approaches The extended subfrontal approach is very helpful for complex tumors involving the fronto-naso-ethmoid midbase, usually with intracranial and intradural extension. When the tumor is growing far from the midbase corridor, the extended subfrontal approach must be modified adding complementary osteotomies at the lateral skull base or facial skeleton. For those cases that affect the spheno-ethmoidal region with almost no intracranial extension, the subcranial approach (popularized by Raveh) is very suitable. The access is given by a limited osteotomy of the frontal sinus, exposing the subcranial region. Only small intradural-intracranial extension can be controlled with this route. When the tumor is growing lateral to the cavernous sinus, a orbito-zygomatic ostetomy is added to the bifrontal and orbital rim ostetomy (anterolateral resection). The extradural-infratemporal component of the tumor can be reached (Figures 11 and 12). If the tumor is involving the anterior fossa and also the facial skeleton beyond the scope of the subfrontal view, an additional transfacial approach can be done. This is the principle of the craniofacial resection, usually done to resect malignant tumors involving the lower, lateral, anterior or posterior maxillary walls. The transfacial approach includes a facial Weber-Fergusson incision and partial or total maxillectomy (Figure 13). The extended subfrontal approach can be also combined with Le Fort I osteotomy, facial degloving and transorbital approach. The transfrontal-transorbital approach is indicated for resection of malignant tumors that penetrates the bony orbit and its content. The orbit must be exenterated with meticulous dissection. The filling and

170 Neuro-oncology

Fig. 11 Nasopharyngeal Juvenile Angiofibroma. Involvement of anterior fossa with lateral paracavernous and infratemporal extension. Angiography showed the typical high vascularization of this tumor, with a very important supply from the external and internal carotid artery.

Fig. 12 Same patient of figure 12. Total resection after combined skull base procedure: antero-lateral approach combined with transfacial LeFort I approach with midline sagital section. Bifrontal craniotomy including some area of the temporal skull vault (A). Fronto-orbitozygomatic osteotomy osteotomy (B) allowing for the control of the lateral extradural component of the lesion. Intraoperative view of the transfacial approach and complete removal of the tumor (C).

Surgical Treatment of Complex Tumors of The Anterior Skull Base: The Transbasal Extended Approach

171

Fig. 13 Chondrosarcoma with maxillary, orbital and anterior fossa involvement (A and B). Postoperative CT scan showing (C) orbital and anterior fossa reconstruction with temporal muscle (single arrow) in continuity with pericraneal and contralateral temporal fascia (single flap; double arrow). Intraoperative view (D) showing the temporal muscle nicely epitelized several weeks after surgery, restoring the anatomy and function of the palatal region.

reconstruction of the orbital cavity can be done with temporal muscle or free muscle transfer (microvascular flap) from rectus abdominis or radial antebraquial area.

Reconstruction The reconstruction of the different anatomical elements after surgical approach and tumoral resection is one of the most important steps of the procedure. Any dural defect should be repaired, by direct suture or by means or dural patch. Autologous graft from vicinity must be used, rather than alien materials. The pericranial tissue is the first choice, although the temporal fascia can be also used. The most problematic defects are those at the subfrontal area in the vicinity of the anterior clinoid, tuberculum sellae and lesser sphenoid wing, where the dural layer is very thin. If the dura is infiltrated by the tumor and must be resected, the probability of a watertight closure is very low and the risk of CSF fistula and/or pneumochephalus is very high. Tenting sutures try to avoid extradural fluid accumulation and “dead space”. The bony skull base is also reconstructed with the aid of microplates. The frontoorbital badeau is secured to the frontal bone after removing the mucosa of the frontal sinus, previously exposed. The midbase defect (between both orbits) only the interposition of soft tissue (pericraneal vascularized flap; galea-frontalis flap) trying to insulate the intracranial cavity from the nasal and paranasal cavity. This technique prevents also from

172 Neuro-oncology

Fig. 14 Steps of the reconstruction of the anterior skull base (patient of figure 8). Pericraneal graft covering the anterior fossa (A and B). Bifrontal craniotomy and orbito-frontal flap (C and D). Bony assembly with the aid of microplates (E and F).

any possible herniation of the intracranial content (Figure 14). There is no need of interposition of any bone (as formerly done). Fat graft is not advisable if there is some possible contact with the aerial cavity. The temporal muscle can be used also for anterior fossa reconstruction, after proper rotation. If maxillectomy has been done, the temporal muscle can be very useful restoring the anatomy and fuction. As a rule, non biologic alien materials should be avoided, as they increase the probability of infection. Before closure of the skin, a drainage system is left at the subgaleal space.

POSTOPERATIVE CARE The postoperative care in this patients is of paramount importance. Antibiotic should be administered perioperatively. The subgaleal drainage is kept no more tan two days, paying attention to the vacuum pressure: If the dural plane has not been watertight closed, CSF aspiration can lead to serious complications. The spinal drainage is kept initially closed after surgery, as the release of CSF can provoke mental disturbance that can be misleading in the immediate postoperative period. If there is some suspicion of CSF leak, the drainage is opened. A daily CSF sample can be taken, checking cellularity and glucose. Any increase of the cellularity and lowering of the glucose must be interpreted as possible CSF infection and culture must be done. The patient must be seated and walking as soon as possible, to avoid complications related to bedridden. Care must be also taken regarding the avoidance of pulmonary infection, as cough may “inject” contaminated air into the cranial (and even intradural) cavity, increasing the risk of pneumocephalus, meningitis and extradural empyema (Figure 15).

Surgical Treatment of Complex Tumors of The Anterior Skull Base: The Transbasal Extended Approach

173

Fig. 15 Pneumonia in the postoperative period with persistent cough (patient of figure 8). Headache and deorientation due to pneumocephalus with mass effect (A). Coronal MRI (B). The arrow is pointing out the bubbles of air after entering the intradural cavity beacuse of failure in the reconstruction. The tumor resection included the paraclinoid dura, precluding the reconstruction in a watertight fashion.

CONCLUSIONS Complex tumors at the anterior skull base are a formidable and challenging problem for the neurosurgeon. The simultaneous involvement of several anatomical compartments and the intricate anatomy of the region make surgery difficult and risky. Complications associated to these approaches are very common, many of them associated with failures in the reconstruction of the skull base.

FURTHER READINGS 1. Arita N, Mori S, Sano M, Hayakawa T, Nakao K, Kanai N, Mogami H. Surgical treatment of tumors in the anterior skull base using the transbasal approach. Neurosurgery. 1989 Mar;24(3):379-84 2. Chandler JP, Pelzer HJ, Bendok BB, Hunt Batjer H, Salehi SA. Advances in surgical management of malignancies of the cranial base: the extended transbasal approach. J Neurooncol 2005 73(2):145-52. 3. Chandler JP, Silva FE.Extended transbasal approach to skull base tumors. Technical nuances and review of the literature. Oncology 2005 Jun;19(7):913-9 4. Feiz-Erfan I, Han PP, Spetzler RF, Horn EM, Klopfenstein JD, Porter RW, Ferreira, MA, Beals SP, Lettieri SC, Joganic EF. The radical transbasal approach for resection of anterior and midline skull base lesions. J Neurosurg 2005 103(3):485-90. 5. Honeybul S, Neil-Dwyer G, Lang DA, Evans BT, Weller RO, Gill J. The extended transbasal approach: a quantitative anatomical and histological study. Acta Neurochir (Wien). 1999;141(3):251-9. 6. Kawakami K, Yamanouchi Y, Kawamura Y, Matsumura H. Operative approach to the frontal skull base: extensive transbasal approach. Neurosurgery. 1991 May;28(5):720-4. 7. Kurtsoy A, Menku A, Tucer B, Suat Oktem I, Akdemir H, Kemal Koc R. Transbasal approaches: surgical details, pitfalls and avoidances. Neurosurg Rev. 2004 Oct;27(4):26773. 8. Lang DA, Honeybul S, Neil-Dwyer G, Evans BT, Weller RO, Gill J. The extended transbasal approach: clinical applications and complications. Acta Neurochir(Wien) 1999;141(6):579-85. 9. Sekhar LN, Nanda A, Sen CN, Snyderman CN, Janecka IP. The extended frontal approach to tumors of the anterior, middle, and posterior skull base. J Neurosurg. 1992 Feb;76(2):198-206. 10. Spetzler RF, Herman JM, Beals S, Joganic E, Milligan J. Preservation of olfaction in anterior craniofacial approaches. J Neurosurg. 1993 Jul;79(1):48-52.

174

Parasellar Meningioma (Tuberculum Sellae Meningioma) HEE-WON JUNG and CHUL-KEE PARK Department of Neurosurgery, Seoul National University College of Medicine Key words: Tuberculum Sellar Meningiomas, Visual Coutome, Approach

Introduction Tuberculum sellae meningioma is midline tumor that originates from the dura of planum sphenoidale, limbus sphenoidale, chiasmatic sulcus, tuberculum sellae, and diaphragm sellae. Sometimes the tumor involves the dura of the anterior clinoid process and medial surface of optic canal. The most common presenting symptoms and signs are visual disturbances that are asymmetric, starting in one eye, worsen, and then spread to the other eye. This is due to the tumor displaces the optic nerve and chiasm posterolaterally. Therefore, visual field defect usually starts from the temporal area. The blood supply to the tumor is frequently from the ethmoidal branches of the ophthalmic artery, the anterior branch of the middle meningeal artery, and the meningeal branches of the internal carotid artery. Surgical resection of the tumor is the treatment of choice. Various approaches are possible for the access to the tumor including unilateral subfrontal approach, pterional approach, orbitopterional approach, bifrontal interhemispheric approach, and transsphenoidal approach. Whatever the surgical approach, the main steps of the tumor resection are the devascularization of the basal blood supply, followed by internal debulking and capsule dissection. Small sized tumors can be removed by unilateral subfrontal approach or pterional approach. Medium sized tumors with possible anterior clinoid process and optic canal involvement can be more safely removed by orbitopterional approach with anterior clinoidectomy with better chances for the preservation of visual function. (Figure 1) Larger tumors, although it is not an usual situation for tuberculum sellae meningiomas as visual disturbance in relatively early stage renders the diagnosis of the tumor, needs greater surgical flexibility which can be provided by bifrontal interhemispheric approach. The surgical procedure of the orbitopterional approach for the resection of the tuberculum sellae meningioma is described in this chapter. The orbitopterional approach has several advantages. Firstly, working distance during the surgery is much shorter than any other approaches. Secondly, removal of bony obstacles including anterior clinoidal process and orbital roof extradurally before debulking a tumor provides sufficient space for tumor dissection and helps preserving visual function by securing the optic nerve from excessive stretching during manipulation. Thirdly, with minimal brain retraction, upper portion of the tumor can be visualized so that safe dissection of tumor from inferior part of the optic apparatus can be performed more safely.

Parasellar Meningioma (Tuberculum Sellae Meningioma)

175

Fig. 1 Magnetic resonance (MR) images showed a 3.5x 3.5 x 3.5 cm sized mass, in the sellar and suprasellar region, which compressed optic chiasm and compressing both bilateral intracerebral arteries and anterior cerebral arteries based on tuberculum sellae, chiasmatic sulcus, limbus sphenoidale, and diaphragma sellae.

Surgical procedure Position Supine with the head turned 30 degree from midline parallel to the floor, inclined slightly downward to minimize torsion to the contralateral jugular vein, and skeletal fixation was done. Lumbar puncture and cerebrospinal fluid drainage is optional procedure to aid exposure and preventing excessive brain retraction. In determining the side of the unilateral surgical approach, it is reasonable to choose the direction of the worse vision due to it is usually correspond to the side of the greater tumor extension which requires early relief of optic apparatus compression during surgery.

Craniotomy and clinoidectomy An extended curvilinear frontotemporal incision acrossing the midline is made starting from just anterior to the tragus to ensure the exposure of orbital rim. The skin flap and the temporalis muscle are elevated utilizing the interfascial technique to protect the frontalis nerve and reflected as separate layers. After exposure of frontotemporal bone including the superior orbital rim and the frontal process of zygoma, key burr hole is made just behind the junction of the frontal root of the zygoma followed by additional burr holes at temporal and frontal bone. It is much convenient if the key burr hole can be cover the anterior fossa, middle fossa and orbit simultaneously. A standard frontotemporal craniotomy using these burr holes is performed. Anterior frontal margin should be parallel to the superior orbital rim

176 Neuro-oncology carefully avoiding the margin of the frontal sinus. And then the periorbita is dissected off of the superior and lateral side of orbit, and the supraorbital nerve is dissected from its notch. To remove the orbital rim, the initial cut is made from the key hole to the frontal process of zygoma. Osteotomes are then used at the orbital roof from key hole to the medial craniotomy edge of orbital rim only to elevated and fractured. (Figure 2) It is also recommendable to make a single craniotomy flap without making a cut at the supraorbital area.

Fig. 2 Burr hole placement and craniotomy lines for orbitopterional approach.

The lateral sphenoid ridge is drilled. When the sphenoid ridge drilling approaches to the anterior clinoid process, the dura is then circumferentially dissected off the anterior clinoid process. The anterior clinoid process is then removed after drilling the root of the anterior clinoid process to the optic strut and by gentle fracture. Caution is needed to avoid any injury to optic nerve, ophthalmic artery and internal carotid artery. Unroofing of the optic canal is needed additionally if the tumor has grown into the optic canal. This early removal of anterior clinoidal process done extradurally before debulking a tumor provides sufficient space for tumor dissection and helps preserving visual acuity by securing the optic nerve from excessive stretching during manipulation.

Tumor removal A curvilinear dural incision is made centered on the sylvian fissure. After sylvian dissection and gentle frontal lobe retraction, the tumor compressing optic apparatus and internal carotid artery is exposed. Usually thin pale optic nerve angulated against falciform ligament is identified superiorly or superolaterally of the tumor. Devascularization of the tumor from the anterior part of tumor origin, that is usually planum sphenoidale, is performed. And then the debulking of tumor is done with suction, the ultrasonic aspirator, or a bipolar coagulator and microscissors. After sufficient internal debulking of the tumor, the dissection of the tumor surface tracing arachnoid membrane is performed carefully. Once dissection approaches the neurovascular structures, only bi-polar cautery and microdissection should be used. Despite apparent encasement or severe adherence of the optic nerve, a plane of dissection

Parasellar Meningioma (Tuberculum Sellae Meningioma)

177

Fig. 3 After complete removal of the mass well-preserved structures, bilateral optic nerves decompressed, right ICA and its bifurcation, ACA, pituitary stalk, and MCA and its branches are presented. The origin of tumor is coagulated and removed clinoid process was marked with slanting lines. (ACA: anterior cerebral artery, ICA: intracerbral artery, L: left, MCA: middle cerebral artery, ON: optic nerve, Rt: right)

can be obtained under high magnification. Dissection is then continued to free the middle and anterior cerebral arteries. Arterial supply to the optic nerves and chiasm, especially on the inferior surface of the optic apparatus from superior hypophyseal artery, should be preserved by keeping an arachnoid plane during the sharp microdissection. If the tumor grows into the optic canal, it can be removed by curettage with ring curette. This procedure is accompanied with early release of optic nerve by anterior clinoidectomy and unroofing of optic canal. After the tumor has been removed, the origin of tumor is coagulated once again. (Figure 3)

178 Neuro-oncology

Closure The dura is closed in a water-tight fashion. The bone flaps are repositioned and secured with miniplates and screws. It is important to make a good alignment in orbital rim due to the cosmetic outcome. The muscular flap and the skin are closed layer by layer. After surgery, visual assessment should be done in a week and followed-up carefully afterwards. Short-term postoperative visual outcome is a strong indicator of permanent visual outcome after surgery for tuberculum sellae meningioma, and recurrence or regrowth of tumor can be detected by the deterioration of visual function very sensitively.

One point memo 1. In determining the side of the unilateral surgical approach, it is reasonable to choose the side of the worse vision as it usually corresponds to the side of the greater tumor extension, which requires early relief by optic apparatus decompression by surgery. 2. Removal of anterior clinoidal process extradurally before debulking a tumor provides sufficient space for tumor dissection and helps preserving visual acuity by securing the optic nerve from excessive stretching during manipulation. 3. Arterial supply to the optic nerves and chiasm, especially on the inferior surface of the optic apparatus from superior hypophyseal artery, should be preserved by keeping and arachnoid plane using the sharp microdissection.

179

Petroclival Meningioma LIXIN M.D., ZHAO JIZONG M.D. Department of Neurosurgery Beijing Tiantan Hospital Key words: meningioma, Petroclival, casediscussion

A 48-year-old female presented with a-year history of leflower extremity weakness, a several history of occasional nausea and vomiting. Several years prior to her admission. She was medically treated for trigeminal neuralgia on the right side, which has subsided temporarily, but recurred without carbamazepine. Her general examination was normal and neurological examination revealed the muscle strength of left lower extremity was grade Ⅳ-Ⅴ without pathological positive signs. Preoperative MRI scans revealed a mass with stronenhancement after the admission of gadolinium diethylenetriamine penta-acetic acid, involving the petrous ridge, CPA area, tentorium, and middle cranial fossa on soft tissue windows.(A,B,C). Its size was approximately 5×5×5 cm. Moderate compression of the brainstem was demonstrated from this extraaxial lesion. The diagnosis was a petroclival meningioma according to the history and radiological findings. We performed a presigmoid infra- and supratentorial approach to remove the tumor from the posterior and middle fossae. This photographs showed a Horseshoe shape skin line(D,E) which began from up margin of zygomatic arch termination and end to 2cm apart from post aurem. Intraoperative the petrous bone was grinding and the superior petrous sinus(F) was ligated. The tumor(G) was exposed after incided the dura mater. The whole procedure was difficult and the tumor could only be resected piecemeal, We carefully protected CNs Ⅲ, Ⅳ, Ⅴ1, Ⅵ-Ⅷ intraoperative. The patient sustained a temporary palsy of CNs Ⅲ postoperatively(O). Because the dura was partially defect we

A

B

C

Axial(A) , coronal(B) and sagittal(C) T1WI with contrast enhancement show an homogeneous totally enhancing extraaxial mass, involving the petrous ridge, CPA area, tentorium, and middle cranial fossa.

180 Neuro-oncology

D

F

E

G

J H repaired the dura with artificial dura and replaced the two bone flaps like photo(H) with Craniofix-clamp for avoiding a CSF collection under the skin flap and CSF skin fistula. Pathological examination was revealed it was a meningothelial meningioma(J). The postoperative MRI and CT scans confirmed a totally removement of the tumor (k,L,M,N).

Petroclival Meningioma

181

The patient sustained a temporary palsy of CNs Ⅲ which demonstrated that she could not fully open her right up eyelid postoperatively(O). She recovered smoothly without facial nerve palsy and eyeball motion nerves. Her preoperative symptoms such as left lower extremity weakness and trigeminal neuralgia recovered 1-month after operation.

K

L

N O

M

182

The optimal protocol of treatment for petroclival meningioma TETSUO KANNO, KOSTADIN KARAGIOZOV Department of Neurosurgery, Fujita Health University Key words: petroclival meningioma, surgical approach, treatment protocol, results

I. Introduction Petroclival meningiomas remains one of the most difficult lesions for surgical removal. Their location in the midline and between the middle fossae on both sides makes the approach to this lesion through a craniotomy very deep and complex as at the same time they involve critically important nerves, arteries and veins. (Fig.1)

Fig. 1

Although the surgical mortality dramatically reduced in recent years, the surgical morbidity remains significantly high. On the other hand, it is slowly growing meningioma. Therefore, the optimal treatment protocol is still controversial.

II. Cases and long-term result The authors experience(these are the personal series of TK) is based on 138 cases of which 43 cases were operated by retrosigmoid approach, 38 - by combined petrous approach and 57 - by retrosigmoid plus orbitozygomatic approach. (Fig.2,3)

The optimal protocol of treatment for petroclival meningioma

183

Fig. 2

Fig. 3

Gross total resection for tumors arising from petrous apex was 95.3%, however, in tumors with some extension to clivus, the gross total removal was 26.3%. In tumors with some extension to cavernous sinus the gross total removal was 59.7%. The low rate of gross total removal, particularly in cases with tumor extension to clivus is because of ① tumor’s strong attachment to brain stem and/or ② an artery is passing through the tumor (Fig.4). The reason of the low rate of complete removal in cases with tumor extension to cavernous sinus was the involvement the preoperatively non-symptomatic cranial nerves. (Fig.5)

184 Neuro-oncology

Fig. 4

Fig. 5 cranial nerves.

The optimal protocol of treatment for petroclival meningioma

185

The overall complication rate was 41%, of which new cranial nerve deficit was in 30% and facial nerve particularly was worse in 23% of the operated (Fig.6) The excellent resection with a low rate of morbidity depends upon, 1) The presence of Arachnoid membrane around the tumor 2) The consistence of the tumor (hard and fibrous vs. soft and succable) 3) The degree of its involvement with critical neurovascular structures.

Fig. 6

Fig. 7

186 Neuro-oncology

III. Available results of other authors Fig.7 shows the results of surgery for petroclival meningioma by various authors in literatures. The mortality ranges between 0~10% (average 4.11%), and the morbidity between 11~59% (average 24%). These rates are still high. We must take into account also the new cranial nerve palsy, which ranges between 22~91% (average of 46%), and the gross total resection - from 26 to 85% (average 63%). (Fig.7) We have to accept that these studies have not yet shown satisfactory results.

IV. Radiosurgery On the other hand, the radiosurgery shows a rather good result so far. They revealed a good tumor growth control rate. Kondziolka (Neurosurgery 2008) showed 93% of overall control rate.

V. Conclusion The optimal protocol of the treatment for petroclival meningioma is still controversial. The reason of this controversy is mainly due to high morbidity and impairment of the postoperative quality of life. This high morbidity makes the patients unhappy. On the other hand radiosurgery also remains controversial. We need longer follow up to estimate permanent control and cure rates, comparing to surgery.. Therefore the authors can recommend subtotal removal (safe of complications ) followed by radiosurgery.

187

Foramen magnum meningioma MITSUHIRO HASEGAWA, KOICHIRO YOSHIDA, TSUKASA KAWASE, JUNKO MATSUYAMA, YUICHI HIROSE Department of Neurosurgery, Fujita Health University, Japan Key words: foramen magnum, meningioma, transcondyle approach, vertebral artery

Introduction Meningiomas are the most common benign tumors of the foramen magnum. However, the frequency is approximately 1 % of all intracranial meningiomas and this lesion involves lower part of brainstem and lower cranial nerves for live-threatening vital functions. Therefore, this is one of the most challenging surgery for neurosurgeons because of the rarity and the location. Both understanding precise surgical anatomies, selection of proper approaches, and performing meticulous microsurgical techniques are mandatory. Clinically, motor weakness is main symptom, and followed by nuchal rigidity, sensory disturbance, coordination disturbance, and dysphasia. Approximately 60% of foramen magnum meningiomas are located antero-lateraly, 25% anteriorly, and 10% posteriorly (figure 1).

Fig. 1 Locations of foramen magnum meningiomas. Circles indicate attachment of anterior (red circle), antero-lateral (blue), and posterolateral (yellow) type foramen magnum meningiomas.

188 Neuro-oncology

Surgical procedure For posteriorly located foramen magnum meningiomas, midline suboccipital approach can be used associated with or without C1 laminectomy. The tumors attached to the anterior and anterolateral margin of the foramen magnum can be given access by lower lateral suboccipital approach with the several additional corridors advocated depending on the tumor location and the size; conventional posterior suboccipital approach, suboccipital transcondylar approach, transcondylar fossa approach (supracondylar transjugular tubercle approach), far lateral approach combined with and without transposition of SS, extreme lateral approach, extreme lateral infrajugular trans-tubercular exposure, and transoral approach.

Position and skin incision (lower lateral suboccipital approach) The patient is placed in the lateral oblique position (figure 2). The head is placed in the lateral position with the face oriented slightly flexed with vertex down to gain wide space between head and shoulder. Monitoring should be applied (figure 3): NIM response for facial nerve function, an electromyography from endotracheal tube for function of recurrent laryngeal nerve and superior laryngeal nerve (Xth CN), macroscopic muscle movement of trapezius muscle for accessory nerve, and ABR and SEP for brainstem function. The incision is blunt S-shape or hockey-stick. The suboccipital triangle is exposed, and access the horizontal portion of extradural vertebral artery on the C1 vertebral sulcus.

Fig. 2 Schematic drawings and photos of operative position and skin incision for lower lateral approach. For posterolateral type foramen magnum meningiomas, standard prone position is applied.

Foramen magnum meningioma

189

Fig. 3 A photo of setting for intraoperative monitorings for facial, vagal nerves, and SEP.

Craniotomy (figure 4) The procedure consists of the posterior fossa craniotomy (craniectomy), opening the foramen magnum, and C1 hemi-laminectomy, drilling posteromedial one third of the condyle (transcondyle approach), drilling occipital bone of condyle fossa (transcondyle fossa approach), infrajugular drilling to open hypoglossal canal (ELITE) are added, if necessary, depending upon the lesions extension (figure 5). Usually drilling of jugular tubercle (transjugular tubercle approach) or presigmoid drilling is not necessary for foramen magnum meningiomas. The extradural vertebral artery (V3 segment) can be mobilized out with venous plexus of the vertebral groove on C1, so that C1 lamina can be removed safely as lateral as possible up to C1 lateral mass. The resection of additional occipital bone and the posteromedial one third of the occipital condyle and lateral mass of C1 can give easy access to the anterior part of the foramen magnum.

Fig. 4 Standard craniotomy (left, yellow line indicates midline craniotomy and red line indicates lower lateral craniotomy) and postoperative 3D-CT image of craniotomy of posterior midline from outside (right).

190 Neuro-oncology

Fig. 5 Anatomy around the condylar fossa and compartments of craniotomy sites on dry bone.

Dural opening and tumor removal A curvilinear dural incision begins at the superior-lateral part of the craniotomy, extends through foramen magnum to lower part of the laminectomy. Bleeding from marginal and occipital sinuses is managed by coagulation by bipolar forceps and/or hemoclip. The posterior fossa and spinal dura are reflected laterally with retraction stitches. The injury of the cerebellar surface is avoided. CSF is aspirated at the cisterna magna. The brain stem is displaced and rotated to the contralateral side by the tumor bulk. The surgeon can access the lesion through the triangle medial and lateral to the spinal root of XIth cranial nerve. Brain stem should never be retracted. After the lower cranial nerves and spinal roots on the dorsal surface of the tumor and the course of the vertebral artery in the direction of the basilar junction is identified, the surgeon enters between these nerves, open a window in the tumor, internally decompress the tumor, and coagulates the dural feeding arteries. After reaching and coagulating the feeding dural arteries, the devascularized tumor can be removed by ultrasonic aspirator. The peripheral dissection of the tumor is carefully performed without injury of perforators. To expose and remove the tumor located in front of the cervico-medullary junction, the dentate ligaments are cut and stitches are made to gently reflect the spinal cord posteriorly.

Closure The dura has to be closed in a watertight fashion to avoid CSF leak. Dural defect should be replaced by homologous materials, such as fascia or muscle. The muscle and fascia are approximated, superficial fascia and skin are sutured. Suction drain is usually unnecessary. Pre- and postoperative MRIs and surgical views of representative three cases are demonstrated in figures 6-10.

Foramen magnum meningioma

Fig. 6 Sagittal MRI of case 1 with anterolateral type of foramen magnum meningioma. Postoperative MRI (right) indicates total removal.

Fig. 7 Surgical view and schematic illustration of the same case of figure 6. The tumor compresses brainstem posteriorly, and stretches lower cranial nerves and high cervical dorsal rootlets, making operative window (upper left). Right photo indicates total removal.

191

192 Neuro-oncology

Fig. 8 Case 2 with anteriorly located small foramen magnum meningioma. Preoperative (left) and postoperative (right) MRI, indicating total removal.

Fig. 9 Pre (left) and Postoperative (right) MRIs of case 3 with foramen magnum meningioma. Huge meningioma involves bilateral vertebral arteries (red arrows), the small tumor tissue, which adhered to VA and its perforators, was left behind (yellow arrow).

Foramen magnum meningioma

Fig. 10 Surgical view and schematic illustration of the same patient in figure 9. The tumor was gross totally removed, except tumor fragments around the VA.

193

194

Assessment of Pituitary Function CARRIE R. MUH, MD, MS; NELSON M. OYESIKU, MD, PhD, FACS Emory University Hospital, Department of Neurological Surgery Key words: pituitary gland, pituitary function, hypothalamic-pituitary-adrenal (HPA) axis, pituitary dysfunction workup

The Pituitary Gland The pituitary gland controls the function of multiple other glands in the human body, including the thyroid, adrenals, ovaries and testes. It regulates growth, lactation, uterine contractions in labor as well as osmolality and intravascular fluid volume via resorption of water in the kidneys. It secretes eight peptide hormones; six from the anterior lobe and two from the posterior lobe (Table 1). Table 1 Summary of Pituitary Function. (Copied from Oyesiku N: Assessment of Pituitary Function, Rengachary S, Ellenbogen R (eds): Principles of Neurosurgery. New York, Elsevier Mosby, 2005)(30)

Assessment of Pituitary Function

195

The pituitary lies in the sella turcica, a concavity in the sphenoid bone. Its stalk, which contains the pituitary portal veins and neuronal processes, passes through the diaphragma sella, just above which pass the optic nerves (Figure 1). The cavernous sinuses form the lateral borders of the sella, and contain within them the internal carotid arteries, cranial nerves III, IV and VI, and the ophthalmic and maxillary divisions of cranial nerve V.

Fig. 1 Anatomic relationships of the pituitary gland. A coronal view through the sella turcica shows the pituitary gland, its stalk and the relationship to surrounding structures including the cavernous sinuses, carotid arteries and cranial nerves II, III, IV, V1, V2 and VI. (Figure from Oyesiku N: Assessment of Pituitary Function, in Rengachary S, Ellenbogen R (eds): Principles of Neurosurgery. New York, Elsevier Mosby, 2005, pp 559-591)(30)

Because of its diverse array of functions as well as the multiple structures in close proximity to the gland, tumors or abnormalities of pituitary function can present in many different ways. Disorders can lead to an excess or deficiency of pituitary hormones, mass effect from tumors can lead to compression of the pituitary stalk or adjacent structures, and lesions may cause a blockage of the blood supply to the gland. Therefore, a thorough assessment of the pituitary requires clinical examination for signs of hormonal abnormalities, endocrine evaluation of pituitary and related target-organ hormones, and ophthalmologic evaluation to assess for damage to the adjacent cranial nerves. These evaluations not only help to define the pathology prior to treatment, but they can be used to assess the effects of surgery, radiation or medical treatment. Here, we will discuss details the endocrine evaluations needed to determine pituitary function. Anterior Pituitary Hormones Six hormones are produced in the anterior pituitary by five distinct cell types. Lactotroph cells make prolactin (PRL), somatotroph cells produce growth hormone (GH), corticotrophs secrete adrenocorticotrophic hormone (ACTH), thyrotrophs make thyroid-stimulating hormone (TSH), and gonadotrophs produce follicle-stimulating

196 Neuro-oncology hormone (FSH) and luteinizing hormone (LH). The secretion of these hormones is regulated by complex feedback controls from the hypothalamus and target glands (Figure 2).

Fig. 2 Hypothalamic control and feedback regulation. The neural processes of the hypothalamic nuclei terminate on the portal venous system in the median eminence. The portal veins carry releasing and inhibiting factors to the anterior lobe of the pituitary, where they regulate the release of hormones. The production and secretion of these hormones is inhibited by the hormonal products of the target organs via negative feedback. The neural processes of the hypothalamic neurons of the supraoptic and paraventricular nuclei carry ADH and oxytocin which are released from nerve terminals in the posterior pituitary. (Figure from Oyesiku N: Assessment of Pituitary Function, Rengachary S, Ellenbogen R (eds): Principles of Neurosurgery. New York, Elsevier Mosby, 2005)(30)

PRL release is largely determined by dopamine release from the hypothalamus. Corticotropin-releasing factor (CRH), thyrotropin-releasing factor (TRH) and gonadotropin-releasing hormone (GnRH) are secreted by the hypothalamus to stimulate the release of ACTH, TSH and the gonadotropins, respectively. Both excitatory and inhibitory signals are sent from the hypothalamus to the pituitary to control hormone production; for instance, growth hormone-releasing hormone (GHRH) and somatostatin alternately increase and decrease growth hormone secretion. Target gland hormones generally cause a negative feedback loop, inhibiting further production of the hormone that stimulated their release. Prolactin The lactotrophs that secrete PRL are unique in that they can proliferate during adulthood. PRL production is inhibited by dopamine, also known as prolactin-inhibiting factor (23). Dopamine travels along the portal circulation from nerves that originate in the hypothalamic arcuate nucleus. PRL production is stimulated by sleep, vasoactive peptide (VIP), GnRH, peptide histidine methionine (PHM), opiates and estrogen. Exogenous TRH leads to a rapid release of PRL, though the normal physiologic role of this interaction is unclear.

Assessment of Pituitary Function

197

PRL is secreted episodically, peaking 13-14 times per day, with an interpulse interval of about 90 minutes. Small post-prandial rises can be seen, secondary to central stimulation from the amino acids in food (9). During pregnancy, estrogen stimulates lactotroph hyperplasia, leading to hyperprolactinemia. The effects of PRL on the breasts are blocked until after delivery, at which time PRL initiates lactation. Within 4-6 months after delivery, basal PRL levels return to normal (35). Prolactin Deficiency Hypopituitarism leads to a decrease in PRL release. A blunted PRL response in a TRHstimulation test, with a less than 2-fold increase over basal levels, is evidence of inadequate lactotroph reserve which may occur with hypopituitarism. Insufficient PRL can lead to a failure of lactation. This may be an early indication of peripartum pituitary necrosis, or Sheehan's syndrome. Lymphocytic hypophysitis is an autoimmune disorder which usually occurs during or immediately following pregnancy. Transient hyperprolactinemia occurs during its active phase, followed by hypopituitarism and hypoprolactinemia. Prolactin Excess Multiple causes can lead to the over-stimulation of prolactin release and elevated serum PRL levels. Hyperprolactinemia may be due to: 1. excess autonomous production, such as from a pituitary prolactinoma; 2. decreased hypothalamic production of dopamine or blockage of delivery of dopamine to the pituitary, such as from a hypothalamic tumor, drugs that inhibit dopamine production, interruption of the portal venous system in the stalk from a pituitary tumor or aneurysm, or following pituitary irradiation; 3. inhibition of dopamine activity on lactotrophs, such as from phenothiazines that block the interaction of dopamine from its receptors; or 4. overstimulation of PRL by estrogens or opiates. Non-hypothalamic-pituitary causes may be responsible as well, including pregnancy, polycystic ovarian syndrome or primary hypothyroidism. Physiologic, transient hyperprolactinemia occurs with exercise, stress, nipple stimulation, sexual intercourse, and breast-feeding. Women with hyperprolactinemia generally present with amenorrhea, galactorrhea, diminished libido and infertility. Gonadal deficiency and decreased estrogen secretion can lead to osteoporosis. Hyperprolactinemia in men generally manifests as decreased libido, impotence and decreased sperm count leading to infertility. Workup Laboratory tests for suspected hypo- or hyperprolactinemia include serial measurements of basal, resting serum PRL levels by radioimmunoassay. Normal values are gender-specific, and peak values occur during the late hours of sleep (37). PRL is secreted episodically, so random levels may be above or below normally-accepted limits. Because of this variability, minimally elevated levels should be confirmed from several samples, or from a pooled sample. In normal subjects, serum PRL levels range from 5-20 ng/mL. PRL deficiency of 1. In a patient with hyperthyroidism, or a patient with a pituitary tumor who has been previously treated for hyperthyroidism, an elevated TSH level combined with an elevated ratio of alpha-subunit to TSH, indicates a TSHsecreting pituitary adenoma. In patients who have had ablative thyroid treatments for misdiagnosed TSH-secreting pituitary tumors, elevated plasma TSH levels do not fully suppress when the patient is given thyroid hormone, and the pituitary TSH response to TRH is blunted. Gonadotropins FSH and LH are produced and released by the gonadotrophs of the adenohypophysis to regulate ovarian and testicular function. In women, FSH stimulates growth of the granulosa cells of the ovarian follicle and controls their estrogen secretion. At the midpoint of the menstrual cycle, the increasing level of estradiol stimulates a surge of LH secretion, which then triggers ovulation. After ovulation, LH supports the formation of the corpus luteum. Exposure of the ovary to FSH is required for expression of the LH receptors. In men, LH is responsible for the production of testosterone by Leydig cells in the testes. The combined effects of FSH and testosterone on the seminiferous tubule stimulate sperm production. FSH and LH secretion occur in a pulsatile fashion in response to pulses of secretion of GnRH from the hypothalamus. GnRH is also known as LH-releasing hormone (LHRH) because of its potent stimulation of LH secretion. Levels of FSH and LH are regulated by a balance of GnRH stimulation, negative feedback regulation from the inhibin peptide secreted by the ovaries and the testes, and the effect of the sex steroids on the pituitary and the hypothalamus. Appropriate concentrations of FSH and LH are required for normal sexual development and reproductive function in both women and men. LH and FSH circulate in blood predominantly in the monomeric form found in the pituitary. FSH has a half life of 3-5 hours, so serum levels are more stable than are those of LH, which has a half life of 30-60 minutes.

Assessment of Pituitary Function

211

GnRH stimulates gonadotropin secretion from the pituitary for the first few months of life, then the pituitary becomes unresponsive to GnRH until puberty, when pulsatile secretion of FSH and LH occur in response to pulses of GnRH. At menopause, when gonadal failure occurs, the negative feedback provided by the hormonal products of the gonads is eliminated so serum levels of FSH and LH increase. Gonadotropin Deficiency and Workup Hypogonadism presents in women as amenorrhea and loss of libido associated with uterine and vaginal atrophy. In men, low testosterone results in loss of libido, impotence, decreased beard growth and body hair, and testicular softening. When hypogonadism is suspected, endocrine evaluation should include measurement of plasma FSH, LH and sex hormones estradiol in women and testosterone in men. FSH and LH are measured by immunoassay. In men above the age of puberty, these levels are within a fairly narrow range. In women, however, the pulsatile nature of LH and FSH, and their marked fluctuation during the menstrual cycle, pregnancy and menopause have to be considered in the interpretation of these lab results. In adolescents and women, isolated and random FSH and LH levels are of little diagnostic use alone, and must be correlated with the results of simultaneous levels of estradiol or testosterone and the results of dynamic testing. Estradiol binds to sex-hormone binding globulin which will have elevated levels in women who are taking oral contraceptive pills or hormone replacement therapy. Testosterone in men has a significant diurnal variation, and should be assessed between 8:00am and 9:00am. Primary hypogonadism is associated with low levels of sex steroids and high levels of FSH and LH. This may be due to primary ovarian failure such as with ovarian dysgenesis, oophorectomy or premature ovarian failure, or primary testicular failure such as with Klinefelter's syndrome or orchiectomy. Decreased levels of FSH and LH may also be found in hypothalamic disease including tumors such as craniopharyngiomas or hypothalamic region meningiomas, germinomas, gliomas or hamartomas, as well as other hypothalamic infiltrative or infectious pathology such as sarcoidosis, eosinophilic granuloma, tuberculosis, fungal infections or syphilis. Hypothalamic trauma, vascular disease and radiation therapy can also be the cause. If FSH and LH are inappropriately low and are associated with a decreased level of estradiol or testosterone, then hypogonadotropic hypogonadism can be diagnosed. This may be a primary result of congenital causes, as with Kallman's syndrome, in which GnRH deficiency is associated with anosmia and defective development of the midline structures of the brain. More commonly however, hypogonadotropic hypogonadism is a secondary, acquired defect of GnRH production associated with hypothalamic dysfunction, as occurs with destruction of the pituitary gonadotrophs or interruption of pituitary stalk function from a sellar mass or apoplexy, or from surgery or radiation to treat a sellar tumor, or as a result of stress, systemic disease, anorexia nervosa or bulimia, or sometimes seen in very athletic women. GnRH stimulation testing is rarely used today, but at times may be useful to determine the presence of adequate gonadotroph reserve. If a detectable elevation of FSH and LH levels occurs after GnRH administration, functional gonadotropic cells are still present.

212 Neuro-oncology This response to GnRH may require priming of the gonadotrophs with repeated injections of GnRH. Gonadotropin Excess and Workup Elevated FSH and LH may be seen with polycystic ovary syndrome, paraneoplastic gonadotropin secretion, precocious puberty and gonadotrope-secreting adenomas. Though FSH-secreting and LH-secreting pituitary adenomas are rarely observed clinically, approximately 5% of pituitary adenomas have immunohistochemical staining for the gonadotropins or their subunits. Nearly all of these tumors are clinically nonfunctioning pituitary macroadenomas that cause symptoms because of their mass effect on sellar or parasellar structures, as there is no characteristic hypersecretory endocrinopathy, as occurs with other hormone secreting tumors. About 20% of these tumors secrete the alpha-subunit rather than a complete gonadotropin. Precocious puberty is often associated with hypothalamic hamartomas in children. These tumors interrupt the normal suppression of pituitary gonadotropin function by higher neural centers, leading to pulsatile secretion of GnRH and, in turn, secretion of FSH and LH, estrogen, and testosterone and premature sexual development. Sustained, non-pulsatile exposure to GnRH desensitizes the gonadotrophs to GnRH and inhibits FSH and LH release. A long-acting analogue of GnRH is used to suppress pituitary gonadotropin secretion and reverse sexual development in children with idiopathic precocious puberty or precocious puberty due to a hypothalamic hamartoma. Ectopic production of gonadotropin, usually of human chorionic gonadotropin which has LHlike activity, by germinomas, lung carcinomas and other tumors may also lead to precocious puberty. Posterior Pituitary Hormones The neurohypophysis is the posterior lobe of the pituitary. This lobe secretes antidiuretic hormone (ADH) and oxytocin, which are produced by hypothalamic neurons but are stored in secretory granules in the nerve terminals of the neurohypophysis and are released from there in response to various stimuli. If the posterior pituitary is selectively damaged but the median eminence and hypothalamus remain intact, these hormones can be secreted from the median eminence. Antidiuretic Hormone ADH conserves water by reducing the rate of urine output. This antidiuretic effect is achieved by promoting the reabsorption of solute-free water in the distal collecting tubules of the kidney. Though this hormone is also known as vasopressin, it has little to no cardiac pressor effect in healthy humans. Through the action of ADH, serum sodium concentrations and serum osmolality are maintained within a narrow range, despite large daily variations in sodium intake and water loss. Derangements in ADH secretion can lead to severe, life-threatening disturbances in serum osmolality and volume. Though multiple hypothalamic signals influence ADH secretion, the primary stimuli for ADH release are an increase in plasma osmolality or a decrease in plasma volume. Even a 2% increase in plasma osmolality caused by an impermeable solute, such as NaCl, causes shrinkage of hypothalamic osmoreceptor cells, stimulating ADH release as well as

Assessment of Pituitary Function

213

thirst. This osmoregulatory mechanism is differentially sensitive to various plasma solutes. Sodium and its anions, which normally contribute >95% of the osmotic pressure in plasma, are the most potent stimulators of ADH release. Sugars, such as sucrose and mannitol, are nearly as powerful. Decreased intravascular volume is also a potent stimulator of ADH secretion. Small decreases in volume activate stretch receptors in the left atrium which lead to ADH release, while decreases in volume of about 10% stimulate ADH release via baroreceptors in the carotid arteries and the aortic arch (Figure 4).

Fig. 4 Regulation of ADH secretion. The main stimulators of ADH release by the posterior pituitary are an increase in plasma osmolality or a decrease in intravascular volume. Osmolality is detected by hypothalamic osmoreceptor cells, while volume changes are detected by atrial stretch receptors and carotid and aortic baroreceptors. (Figure from Oyesiku N: Assessment of Pituitary Function, Rengachary S, Ellenbogen R (eds): Principles of Neurosurgery. New York, Elsevier Mosby, 2005)(30)

Higher neural centers also influence ADH levels. Beta-adrenergic and cholinergic agonists stimulate ADH secretion, while alpha-adrenergic agonists and atropine inhibit it. Psychological factors, pain, and stress can therefore increase ADH release. Nausea is an instantaneous and extremely potent stimulus for ADH secretion in humans. Other stimuli for ADH release include hypoglycemia, angiotensin, nicotine, morphine, and barbiturates, while inhibitors of ADH release include alcohol, phenytoin, and narcotic antagonists.

214 Neuro-oncology Deficient ADH; Diabetes Insipidus The typical clinical manifestations of diabetes insipidus (DI) include polyuria, polydipsia, excessive thirst and nocturia. Polyuria may be defined as the excretion of more than 2.5 L of urine per 24 hours on at least 2 consecutive days, provided that patients are allowed free access to and drink water ad libitum. The severity of diabetes insipidus varies widely, with urine volumes ranging up to 20 L per day. If access to water is restricted, dehydration can rapidly become severe and result in altered mentation, fever, hypotension, and death. Central DI is deficient ADH secretion from the neurohypophysis in response to normal osmotic stimulation. This disorder is also known as hypothalamic DI, cranial DI or neurogenic DI. These patients generally have normal thirst sensation though they have insufficient circulating antidiuretic activity. Diabetes insipidus secondary to renal tubular insensitivity to the antidiuretic effect of ADH is usually called nephrogenic diabetes insipidus. These patients generally have a normal of high level of circulating ADH. Primary polydipsia is a third mechanism leading to diabetes insipidus. This is the ingestion of excessive volumes of water, resulting in suppression of vasopressin release and consequent polyuria. Causes of central DI include sellar and parasellar tumors, especially craniopharyngiomas, large non-functional pituitary adenomas, germinomas, and metastatic tumors; hypothalamic tumors or infiltrative processes such as sarcoidosis and histiocytosis-X; pituitary or hypothalamic injury or surgery; head trauma; subarachnoid hemorrhage from ruptured intracranial aneurysms; and idiopathic causes. DI is rarely a presenting feature in patients with pituitary adenomas, but is more common in patients with craniopharyngioma or hypothalamic lesions. DI from head trauma or damage to the pituitary stalk or hypothalamus generally presents with 24 hours of injury. In about 50% of cases of posttraumatic diabetes insipidus, the condition resolves spontaneously within a few days. Permanent diabetes insipidus develops in another 30-40% of these patients, and the remainder exhibit a triphasic response to injury. In this last group, the onset of polyuria is abrupt but lasts only a few days. It is followed by a period of antidiuresis similar to SIADH that lasts 2-14 days before permanent DI develops. This triple response to injury is believed to be attributable to release of the stored ADH within the neurohypophysis (27, 40). Glucocorticoid deficiency or thyroid hormone deficiency can lead to impairment of the kidney's ability to excrete a water load and to dilute urine maximally. This impairment of anterior pituitary function can therefore mask central DI, which becomes apparent only when the hypopituitarism is treated. Workup Patients with DI will demonstrate persistent urine osmolality of less than 300 mOsm/kg H2O associated with urine specific gravity of 1.005 or less and plasma osmolality greater than the normal 287 mOsm/kg H2O. To confirm the diagnosis, patients are tested to document that there is inadequate release of ADH to an osmotic stimulus. The safest and most widely used test to raise plasma osmolality is the water deprivation test. In this test, baseline body weight, urine and plasma osmolality, and vital signs are measured, then all oral intake is stopped. Water deprivation begins the night

Assessment of Pituitary Function

215

before the test in patients with mild polyuria, and early on the day of the test in patients with severe polyuria. It is important that the test only be performed while the patient is under constant supervision, to prevent severe dehydration. For patients with DI this test can be dangerous. Hourly measurements of urine osmolality and weight are obtained. Dehydration continues until either two sequential urine osmolalities vary by 9% after vasopressin injection. This test not only establishes whether or not diabetes insipidus is present, it also distinguishes central DI from other causes of polyuria. In patients with polyuria from renal disease or nephrogenic DI, the rise in urine osmolality with dehydration is limited and does not increase after vasopressin administration. In patients with primary polydipsia, water deprivation is prolonged before urine osmolality plateaus, and urine osmolality does not increase after the injection of vasopressin. The measurement of plasma ADH concentration under basal conditions can be used as an adjunct to the water deprivation test, but this radioimmunoassay test is not routinely available and is rarely affords diagnostic benefit. Excess ADH; Syndrome of Inappropriate ADH Secretion The syndrome of inappropriate antidiuretic hormone (SIADH) is the most common cause of euvolemic hypo-osmolality. It is also the most prevalent cause of hypoosmolality of all etiologies encountered in current clinical practice, occurring in 30-40% of all hypo-osmolar patients (21). SIADH results from excess ADH secretion, either from the hypothalamus or from an ectopic source. This excess ADH stimulates excessive retention of free water and leads to the inability to excrete dilute urine. This results in hyponatremia and serum hypotonicity. When a patient has hyponatremia and low serum osmolality, then continued ADH release, with the osmolality of urine higher than that of plasma, is inappropriate. The etiology of SIADH is diverse. Causes include ectopic production of ADH by tumors, classically oat cell carcinoma; by lung tissue during inflammatory diseases such as tuberculosis; excessive neuro-hypophyseal release of ADH caused by intracranial disorders, including head trauma, subarachnoid hemorrhage, subdural hematoma, pituitary apoplexy, pituitary stalk damage, intracranial surgery, encephalitis, meningitis, intracranial abscess, or hydrocephalus; Guillain-Barré syndrome; delirium tremens; acute psychosis; or by drugs that stimulate ADH release such as chlorpropamide, carbamazepine or tricyclic antidepressants (20, 21). The clinical features of SIADH include weight gain, weakness, lethargy, and mental confusion. As serum sodium drops below 120 mEq/L seizures and coma can occur. Hypo-osmolality is associated with a broad spectrum of neurologic manifestations. In the

216 Neuro-oncology most severe cases, death can result from respiratory arrest after tentorial cerebral herniation and brainstem compression. This process has been termed hyponatremic encephalopathy and primarily reflects brain edema resulting from osmotic water shifts into the brain due to decreased plasma osmolality (3, 17). Significant symptoms generally do not occur until plasma sodium concentration falls below 123 mEq/L, and the severity of symptoms can be roughly correlated with the degree of hypo-osmolality (3). The period over which hypo-osmolality develops also greatly affects the severity of symptoms. Rapid development of hypo-osmolality will cause marked neurologic symptoms, whereas gradual development over several days or weeks often presents with only mild symptomatology despite profound degrees of hypo-osmolality. If given sufficient time, the brain can counteract osmotic swelling by excreting intracellular solutes such as potassium and organic osmolytes, an adaptive process known as volume regulation (17, 39). Rapid development of hypo-osmolality may cause brain edema before this adaptation can occur. Underlying neurologic disease also affects the level of hypo-osmolality at which CNS symptoms appear. Moderate hypo-osmolality that would be of little concern in an otherwise healthy patient can cause morbidity in a patient with an underlying seizure disorder. Non-neurologic metabolic disorders such as hypoxia, hypercapnia, acidosis and hypercalcemia, can similarly affect the level of serum osmolality at which CNS symptoms occur. Workup Laboratory findings in SIADH include hyponatremia, serum hypotonicity, urine osmolality that exceeds that of plasma, and elevated urinary sodium concentration. Plasma osmolality is generally >275 mOsm/kg H2O, urine osmolality is >100 mOsm/kg H2O with normal renal function, and urine sodium will generally be greater than or equal to 20 mEq/L, though this may be lower in patients who are chronically sodium depleted of sodium. The SIADH patient will be euvolemic, without clinical signs of hypovolemia such as orthostatic hypotension or tachycardia, or signs of hypervolemia such as ascites. The diagnosis of SIADH is made when these features are present and after adrenal, thyroid, renal, and hepatic dysfunction and diuretic use have been excluded. Measurement of a plasma ADH level that is inappropriately elevated relative to plasma osmolality confirms, but is not essential for, the diagnosis. An abnormal water load test can also confirm SIADH. A patient is given a 20 ml/kg water bolus and excretion and urine osmolality are measured. Inability to excrete at least 90% of the water load within 4 hours and/or failure to dilute urine osmolality to 65 year of age. Pediatrics tend to deteriorate rapidly. Women tend to develop more brain swelling and intracranial hypertension after a head injury, that’s why they appear to do worse than men2 . ■ Mechanism of accident, penetrating injuries versus blunt injuries. The projectiles that cause penetrating injuries are classified into high-velocity, such as gunshot and low-velocity, such as knives and arrows. Injuries from high velocity objects produce extensive tissue damage compared to low velocity objects which produce focal damage. Penetrating injuries in general exhibit higher risk of infection and bare a worse outcome. Blunt injuries include, MVA, assaults and falls. In

662 Head Trauma

■

■ ■ ■

patients who are involved in MVA, pedestrians do worse than vehicle occupants2. In pediatrics accidental injuries has to be differentiated from physical abuse. Loss of consciousness, the duration of LOC and wither it was associated with post-traumatic amnesia is important in determining the severity of the trauma and predicting outcome. Nausea, vomiting, headache and visual disturbances might indicate increased ICP. Post traumatic seizures Co-morbidities, such as DM and HTN, have been associated with worse outcome. Tight control of blood glucose proved to improve survival outcome.

The Clinical Examination: The general examination ■

■

■

■ ■

■

Vital signs: a combination of hypertension, bradycardia and irregular respirations is known as the Cushing reflex. It is seen in cases of increased intracranial pressure but it is neither sensitive nor specific. Irregular respirations might be a sign of pons or medulla injury. Pyrexia is seen in medullary lesion. Inspection and palpation of the head for skin: It is absolutely important to look for any lacerations or cut wounds ecchymosis, subgaleal hematoma, and fractures. Palpation for a bony step off (a discontinuation of the shape of the skull) is an indication of a displaced fracture. Signs of basilar skull fracture: CSF otorrhea, CSF rhinorrhea, hemotypanum, periorbital ecchymosis (raccoon’s eyes) and ecchymosis on mastoid process (battle’s sign) Facial fractures Neck rigidity: seen in patients with SAH and may be seen in cases of increased ICP and impending herniation Signs of spine trauma: Stability of cervical spine should be considered and respected

Neurological Examination Mental Status ■

Consciousness and alertness evaluated through the Glasgow Coma Scale (GCS). If patient cooperative, orientation and memory has to be evaluated.

Cranial nerves ■

■

Optic nerve: check patient’s visual acuity through a Snellen chart, if unable to see that, ask him to count fingers. If he fails, ask if he can detect hand motion and in the end if he can appreciate light. If patient uncooperative: swinging flash light from one eye to another will demonstrate optic nerve injury if present. Pupils: size, reactivity and symmetry. An abnormality can be elicited in an

Head Trauma

■

■

■

■

663

injury to the eye, the optic nerve, the oculomotor nerve, and the midbrain or the pons. Yet, an ipsilateral fixed dilated pupil is classically associated with transtentorial herniation. In patients with severe head injury bilateral fixed pupils is seen in 20-30% of patients in which 70-90% will have a poor outcome (dead or vegetative) compared to 30% with bilateral reactive pupils . Fundoscope: papilloedema indicate increased intracranial pressure but might be absent in acute cases Eye movement: these movements are an important index of the functional activity present with in the brain stem reticular formation3. Therefore, they are an important localizing tool. If patient uncooperative and neck fracture has been ruled out oculocepahlic and oculovestibular responses are implicated. Corneal and gag reflex: indicate the integrity of the 5th, 7th, 9th and 10th cranial nerve and the brain stem Facial symmetry: if patient uncooperative a painful stimuli (supraorbital nerve irritation) can elicit any facial asymmetry

Motor examination ■ ■

■

■

Full motor exam is carried out in all 4 limbs If patient uncooperative: apply a painful stimulus to detect any movement, check most importantly to symmetry. Asymmetrical posturing, tone, or reflexes may indicate underlying contralateral mass lesion. Intact deep tendon reflex in the presence of a flaccid limb might indicate a central nervous system lesion not a peripheral nerve lesion Babinski reflex: indicates an upper motor neuron lesion

Sensation examination ■ ■

Sensory examination is carried out in all 4 limbs and major dermatome If patient uncooperative: check for a response upon painful stimuli

Motor and sensory examination along with anal and bulbocavernous reflex is better implicated in cases where a spine injury is suspected.

Scalp Injury: The scalp is composed of 5 layers; skin, subcutenous tissue, apneurosis (galea), loose areolar tissue and skull periosteum. In head trauma a layer or more might be injured, the majority of these injuries fortunately can be managed with simple suturing. The scalp is highly vascular due to the rich anastomosis supply from both the external and internal carotid arteries. Therefore significant bleeding might be associated with scalp injury especially in the pediatric group. Compression dressing is usually applied as a temporary measure to control the bleeding, later on when appropriate the wound is cleaned, the edges shaved and then the scalp is closed layer by layer. The subcutenous and galea is usually closed with Vicryl 2.0-3.0 inverted simple interrupted sutures and the skin

664 Head Trauma is closed with Dermalon 3.0-4.0 simple interrupted sutures. In cases where significant tissue loss is apparent, the defect is closed with galeal scoring, skin grafts or flaps. A potential subgaleal space might predispose the accumulation of a hematoma after a head injury. It can be palpated on examination as a fluctuating soft swelling and might appear in the CT scan. These hematomas are managed conservatively and exhibit spontaneous resolution. In rare cases where the heamtoma is infected, evacuation and drainage is indicated.

Skull Fractures: There are different types of skull fractures such as: 1. linear skull fracture 2. Diastatic fracture 3. Growing fracture 4. Ping-pong fracture 5. Skull Base fracture 6. Depressed fracture 7. Compund communited fractures 8. Crushed fracture Skull base fracture exhibit a unique entity, it was estimated to bare 4% of all head trauma cases. The clinical manifestations includes, bilateral preorbital ecchymosis known as raccoon eyes (black eyes), ecchymosis of the mastoid process known as battle’s sign, cerebrospinal fluid (CSF) rhinorrhea or otorrhea, cranial nerve palsy, bleeding (with or without CSF leak) through the mouth or nose and or ear, and maybe death. CT scan is the most valuable diagnostic process that usually shows the fractured bone, CSF in air sinuses and pressure in the subdural space or different parts of intracranial cavities. Conservative treatment in the form of excellent antibiotics and bed rest are the usual method of treatment. In cases of optic nerve compression, surgery is indicated to decompress the optic nerve. The risk of meningitis is high and therefore it is a must to cover the patients with broad spectrum antibiotics for at least two weeks. In most cases, CSF leakage seize spontaneously in few days. In the case where CSF rhinorrhea persists, lumbar drain and bed rest is an option before considering surgery to repair the dural defect either via bifrontal craniotomy or via nasal neuroendoscopic technique.

Case demonstration: An 18-year-old girl who was a victim of RTA had lost consciousness for few minutes. She was brought to the hospital conscious with GCS of 15. There was bleeding from the lacerated wound in the right temporal area. No neurological deficit. Brain CT scan showed right temporal depressed skull fracture, (Figure 1). She was taken to the operating room, where the right temporal small craniotomy was performed. The penetrating and comminuted pieces of bones were removed and the depressed pieces of bone were elevated. A dura tear was found. The dural tear was extended, and small subural hematoma was removed. The small area of contused brain tissue was removed

Head Trauma

665

as well. The lacerated scalp wound was cleaned and sutured. The patient made an excellent recovery and was put on broad spectrum of antibiotics for 10 days, and was given antiepileptic medication (phenytoin) for 6 months. Post operative CT-Scan was satisfactory.

Fig. 1 Brain CT-Scan shows temprol depressed fracture

Epidural Hematoma: Epidural hematoma (EDH) is defined as a collection of blood between the outer periosteal layer of the dura and the inner table of the skull. EDH is almost always the result of a blunt head trauma and constitutes 1% of head trauma admissions. It commonly affects young adults and older children and the reason for that could be explained by the tight adherence of the dura to the skull in the elderly population and the flexible nature of the skull in infants. Males are more commonly affected than females. Traumatic EDH is typically the result of a skull fracture that subsequently injures the underlying blood vessels. When the bleeding begins; it accumulates and dissects the dura further more limited usually by the suture lines where the periosteal layer of the dura fuses with the periostium of the cranial vault resulting in the classical lens shape hematoma. Because of the thinness and fragility of the temporal squamous bone compared to the rest of the skull, 70-80% of EDHs are seen in the temporal area. The rest are seen in the frontal, occipital and posterior fossae. The MMA is the most common source of EDHs because of its course through the temporal squama and it predisposition to fractures. Dural sinuses and bridging veins are occasionally the source4. The clinical presentation is classically described as a brief period of loss of consciousness followed by a “lucid interval” followed by a sudden neurological deterioration and ipsilateral fixed dilated pupil. Unfortunately this presentation is seen in less than 30% of the cases and it can also be seen in other neurosurgical emergencies such as subdural and intracerebral hematomas. Another confounding clinical finding in EDHs is the Kernohan phenomeneon with focal finding ipsilateral to the side of the EDH due to the rapid shift of the central basal brain structures and compression of the contralateral cerebral peduncle on the tentorial “Kernohan” notch. This is seen in 10-15% of cases of EDH.

666 Head Trauma EDH is one of the neurosurgical emergencies that can be successfully treated. Unfortunately in the mean time according to the last publication by Bullock et al. in 20065, there is insufficient data to establish standards or guidelines but recommendations have been suggested as demonstrated in Figure 2.

Fig. 2 Epidural Hematomas management strategy Cohen et al 6 demonstrated that patients with dilated pupil who underwent surgical evacuation within 70 min from the injury have a good outcome compared to patients who underwent surgery beyond that. All patients in the 2nd group unfortunately died.

In our hospital, all patients with confirmed EDH in plain CT scan are observed in the ER for at least 6 hours, until the result of the follow up CT scans are checked, regardless of their neurological status. The need for admission depends on the patient’s initial presentation and the follow up CT. Initial presentations that necessitates admission include depressed or decreasing level of conscious, and focal neurological deficit. As for the follow up CT; if there is an increase in the size of EDH, patients are admitted wither they are symptomatic or not. Conservative management mandates a regular radiological and clinical follow up. This includes an hourly examination of the pupils and level of consciousness and a follow up CT scan in 4- 6 hours from the injury or a sooner scan done if any neurological deterioration is detected. Another CT scan is obtained the following day. As mentioned previously the majority of hematomas lay in the temporal area, therefore a standard frontotemporal parietal craniotomy is usually performed for better exposure of temporal and frontal areas and better visualization of the vessels. Within

Head Trauma

667

limits of c-spine precautions, the head is rotated to the opposite side with a shoulder roll under the ipsilateral shoulder to aid in rotation, the head is placed on a horse-shoe head rest (3-point rigid fixation could be avoided to avoid extension of fractures). A question mark skin incision is started 1 cm anterior to the tragus and curved above the pinna till it transects the superior temporal line where it is curved superiorly and anteriorley to a an anterior extent transecting or just lateral to the midline. The 1st burr hole is usually positioned in the lower temporal area where a small craniectomy is carried out if needed (depending on papillary status). Then a full frontal craniotomy is carried out and the hematoma is then appropriately evacuated with suction, irrigation, and cup forceps. Once the hematoma is evacuated, the dura should look relaxed and shiny. If the dura is dusky or bluish in color, or it is becoming tense, an underlying lesion has to be ruled out such as subdural hematoma. It is crucial to determine the source of bleeding and coagulate it to maintain hemostasis. Dural tack up sutures are placed all around the craniotomy and 2 are placed centrally tacked up to the bone flap, to prevent reaccumulation of the hematoma7. The most single important prognostic factor in EDH was found to be the level of consciousness on presentation. That explains the variable mortality rates that start from 0% and reach 40% depending on the cases. Immediate diagnosis and intervention are the keys to successful management of EDH8.

Posterior fossa injury: Because of the confined space of the posterior fossa and its proximity to the brain stem, any lesion there exhibits a unique concern and mandates a close observation. The majority of lesions seen in the posterior fossa after a head injury are EDHs, it constitutes 1.2-12.9% of all EDHs. A neurological deterioration or a mass effect demonstrated in the CT scan as obliteration or distortion of the 4th ventricle, effacement of the basal cistern, or obstructive hydrocephalus indicates a surgical intervention. The rest can be managed conservatively with serial CT scans and close observation. This goes for subdural hematomas and intraparenchymal lesions too24. The following cases have been presented in our hospital and are added to demonstrate the rationale behind the diagnosis and management of EDH.

Case demonstration: A 20 year old man, a victim of MVA, is presented to the ER with post-resuscitation GCS of 10/15, and equally reactive pupils. The CT scan showed bilateral extra-axial homogenous hyper-dense biconvex shaped lesions present in the temporal fossa and extending upward measuring around 1.5 cm in thickness with no edema, no midline shifting as the barin looked to be compressed by the epidural hematomas from both sides, Figure 3. Subarachnoid hemorrhage also was seen.

668 Head Trauma

Fig. 3 Brain CT-Scan shows bilateral epidural hematomas and subarachnoid hemorrhage

The patient was rushed to the OR from the CT-Scan room and immediate surgical evacuation of both hematomas was carried out. The dura was opened in both sides, a subdural hematoma was discovered and evacuated. The source of bleeding was determined; it was a branche from the middle meningeal artery and was coagulated. Dural tack up sutures were done circumferentially and centrally. The patient made an excellent recovery and left the hospital walking in 2 weeks time. The timing of surgery which was less than 2 hours from the time of trauma till the skull was opened was determining factor for such good outcome.

Subdural hematoma: SDH is defined as a collection of blood or fluid between the inner meningeal layer of the dura and the arachnoid matter. SDHs are generally divided into three main entities; acute, subacute, and chronic. ASDH is a SDH presenting within 3 days, subacute between 3rd and 2-3 weeks, and chronic after 3 weeks of a head trauma. The incidence of ASDH was found to be 12-29% in patients admitted with severe TBI9. Similar to EDH, the main cause of SDH is TBI, in which MVA is the primary cause in young adults while falls are the primary cause in elderly (> 65) and infants. Males constitute the majority of patients. Traumatic ASDH is usually the result of a severe head trauma of complex mechanisms that subsequently exerts a massive strain on the brain surface causing an injury to occur in the cortical vessels, most commonly cerebral veins. Bleeding from these vessels accumulates in the potential subdural space and the wide spread sever impact causes associated cerebral contusions and varying degrees of surrounding edema and swelling. Less commonly, ASDH is the result of an accelerating-decelerating type of injury, during a head motion, the bridging veins are stretched. Because of the lack of reinforcement in these veins, their fixation point in the dural sinuses, and the relative potential effect of cerebral atrophy and inherent stretching associated with that; these vessels are easily torn producing a pure SDH over an intact cortex. The latter mechanism is associated with a less severe primary brain injury and a better prognosis. ASDHs are commonly found more and less, in the temporal and frontal areas, respectively 4,10. SDH can be manifested clinically with unspecific signs and symptoms including;

Head Trauma

669

altered level of consciousness, dysphasia, hemiparesis, hemiplegia or signs of increased intracranial pressure. It has been noticed that aSDHs are present in severe TBIs, which is why 80% of patients present to the hospital with GCS 10 mm, regardless of GCS ■ ASDH with a midline shift > 5 mm, regardless of GCS ＊ ■ GCS < 8 and ICP > 20mmHg, regardless of thickness or midline shift ＊ ■ GCS < 8 and asymmetric or fixed and dilated pupil ■ GCS < 8 and decrease of 2 or more points on GCS since hospital admission＊ ＊ Regardless of SDH thickness or midline shift. The main purpose of surgical intervention in this group of patients is to relieve the increasing ICP and its sequele. Even a very thin layer of ASDH with a significant midline shift might be a candidate for surgical intervention. This is because the variability in the thickness of ASDH compared to the degree of the midline shift predicts the outcome. The disability and mortality rate was found to be increased as the midline shift exceeds the thickness of the hematoma with a great degree11. For those patients who require surgery, early intervention is recommended as soon as possible. Our experience and the experience of many other centers suggest that timimg of surgery is an important factor for the outcome. We found out that patients who underwent surgery within 2 hours of injury had a favorable outcome and less mortality rate compared to those patients who underwent surgery after 2 hours. A standard fronto-temporal parietal trauma craniotomy is performed as described in the previous section. Once the bone flap is removed, a wide cruciate dural incision is carried out starting from the area of maximum clot thickness. The clot is evacuated with copious of irrigation and suction. Thorough inspection of the subdural space and the cerebral cortex must be preformed to rule out any source of bleeding that needs coagulation or large (> 2cm) unsalvageable cerebral contusions that need resection. After homeostasis is secured, the dura is sealed with a watertight closure. Depending on the status of the brain, the bone flap is either replaced or preserved in situations where significant brain edema is observed; so is the consideration of the insertion of invasive intracranial pressure monitoring device7. ASDHs do not provide the rewarding outcome after surgical intervention that is usually seen in EDH patients. SDH are the worst traumatic injury affecting the brain. This can be attributed to the associated parenchymal brain injury and the subsequent secondary brain injury that is commonly present with ASDH. Mortality rates ranges from 40-60% 8. There are several factors which influence outcome, such like; age, younger patients in general may have favorable outcome than patients older than 65 years, the period of loss of consciousness and GCS, the signs of brain herniation and brain stem injury.

670 Head Trauma

Case demonstration: 35 years old patient, was rushed to our hospital as a victim of RTA. On arrival to our hospital, he was intubated and GCS was 4, the right pupil was dilated, however both pupils were responding positively for light stimuli. The patient was rushed to CT-Scan which showed right fronto-temprol ASDH, SAH and shifting of the midline; (Figure 4). So, the patient was taken from the CT-Scan room to the Operating Room, where large fronto- tempero-parietal craniectomy was performed, dura was opened, and the hematoma was removed, A intraparenchymal ICP sensor was inserted, a large dural patch was used to loosely close the dura . The bone was not returned back. Patient was sent to the ICU. He was kept intubated and ventilated for 3 days. He was put on dehydration methods. The patient made a remarkable recovery and was discharged after 3 weeks.

Fig. 4 Brain CT- Scan shows right fronto-temperol ASDH.

Chronic SDH Chronic SDH is commonly seen in the elderly. Only 50% of patients give a history of head injury, often a mild injury. Other risk factors include alcohol abuse, seizures, coagulopathies, anti-coagulant therapy, any condition predisposes to falls and low ICP12. CSDH may be presented as alteration of level of consciousness, headache, dysphasia, hemi paresis, seizures or it can mimic neurological conditions, such as dementia, TIA, stroke, and tumors. CSDH usually forms after an ASDH, the blood breakdown products with in the hematoma attracts an inflammatory response that cause the formation of two membranes, an outer thicker vascular membrane adjacent to the dura and inner thinner membrane adjacent to the cortex. These membranes confine the hematoma. In most of the cases the hematomas appear like collection of fluid consisting of liquefied blood and CSF, which appear as “motor oil”. Wither the hematoma slowly increases in size due to recurrent bleeding from the fragile neovascular membrane, or liquefied clot attracting CSF into the cavity by osmosis is uncertain 4,10. CSDHs should not be missed in a CT scan; as the hematoma appears usually as

Head Trauma

671

isodense to the brain parenchyma over the 2nd and the 3rd week; Figure 5.

Fig. 5 Brain CT-Scan shows large left fronto tempero-parietal CSDH

Bilateral CSDH are present in more than 30% of the cases, so no midline shifting can be appreciated. After the 3rd week CSDH appears hypodense. It is not rare to see different areas of density inside the hematoma cavities indicating repeated attacks of bleeding; Figure 6.

Fig. 6 Brain CT-Scan shows left fronto – tempro-parietal CSDH. The mixture of high, low and isodense areas inside the hematoma cavity, indicating repeated attacks of bleeding in different events.

Surgical evacuation is indicated in most cases, yet in the mean time there is no agreement regarding the best surgical technique. Burr hole drainage, twist drill craniostomy, and craniotomy are all options. The choice depends on the degree of complexity of the hematoma. We frequently choose the 2 burr holes method as our first line of treatment in most of the cases. Surgical management is associated with possible complications including; seizures, intracerebral hemorrhage due to the rapid decompression, tension pneumocephalus, subdural empyema, and reaccumalation of subdural fluid. In cases of the reaccumalation of CSDH, craniotomy is indicated to allow removal of the outer and inner memberanes.

672 Head Trauma Rarely cSDHs are managed conservatively; this option is left for patients with small hematomas (< 1cm thick) and no neurological deficit. This group of patients should be educated regarding the risk acute bleeding the use of anti-coagulant therapy and any future falls. Patients who undergo surgery have better out come than those who don’t. Mortality and morbidity rates are increased in the elderly, alcoholics and in patients with recurrences.

Traumatic subdural hygroma: Subdural hygroma is a collection of CSF between the meningeal layer of the dura and the arachnoid. It is thought that this may be the result of a tear in the arachnoid memberane. These collections are commonly seen after a head injury, constituting 5-20% of post-traumatic lesions 8. They are usually asymptomatic but they might present clinically as an altered mental status, neurological deficit, seizures or less commonly headaches. They appear in the CT scan as an extra-axial isodense (to the CSF) collection, Figure 7. In most cases it resolves spontaneously. Surgical evacuation is rarely indicated and usually achieved by a burr hole.

Fig. 7 Brain CT-Scan shows bifrontal post traumatic Subdural hygroma.

Injuries involving the brain parenchyma Head injuries involving the brain parenchyma can be classified as focal lesions and diffuse lesions. Focal lesions manifests as cerebral lacerations, contusions, intracerebral hemorrhages and infarctions while diffuse lesions manifests as cerebral edema, hemispheric swelling, concussions and diffuse axonal injury.

Focal Brain Injury Cerebral lacerations: cerebral contusions are called lacerations when the pia and arachnoid mater are torn. Cerebral contusions: is a pathological term for “brain bruises”. Contusions are areas of petechial hemorrhages and necrotic brain tissue resulting from an injury to the small

Head Trauma

673

blood vessels typically in the gyral crest. They can be divided into coup, counter coup, gliding, and intermediary contusions. Coup contusions are those found at the site of impact, counter coup are found opposite the site of impact usually against a bony prominence , gliding occur in the superior parasagittal margin of the cerebral hemisphere which are notorious for post-traumatic epilepsy, and intermediary are found in the deep structures of the brain. In the CT scan these lesions appear as heterogenous hyperdense lesions with surrounding edema, sometimes assuming a wedge shape. The inferior, anterior and lateral surfaces of the frontal and temporal lobes are commonly affected due to the proximity of these cortical areas to the roughened edges of the inner table of the skull along the floor of anterior cranial fossa, the sphenoid wing, and petrous edges 4,13. Intracerebral hemorrhage: differ from contusions by the degree of blood content. In ICH the blood component constitutes at least two third the volume of the lesion which explains the homogenous hyperdense appearance found in the CT scan 3,4, (Figure 8).

Fig. 8 Brain CT-Scan shows bifrontal areas of cerebral contusion.

Any neurological deterioration or increase in ICP mandates a CT scan to rule out expansion of the contusion or pericontusional edema or the progression to ICH. Delayed traumatic intracerebral hemorrhage (DTICH) is a recognized entity of ICH defined as the presence of an ICH in a previously normal appearing area of the brain in an initial abnormal CT scan. This is due to the disruption of autoregulation most commonly seen in severe TBI, failure to regulate cerebral blood flow to the damaged brain vessels subjects these vessels to increased intravascular pressure leading to the hemorrhage 14. In these patients mortality reaches up to 72% 15. Studies have demonstrated worse outcome in patients who develop DTICH with in 48 hours of the initial injury 7. Controversy has risen regarding the management of focal brain injuries, some favored conservative management, and others advocated for surgical intervention. Recent studies have shown that early surgical evacuation of these lesions in a subpopulation of patients decreases mortality rates and improves functional outcome. Surgical indication was found to be related to many factors including clinical, radiological findings and ICP. The location of a lesion, intracranial hypertension, subarachnoid hemorrhage, cistern effacement, lesion volume and hypoxic events were all found to be factors predicting failure of non-operative management 15. We share the recommendations of several authors on surgery for patients with

674 Head Trauma traumatic parenchymal lesions which included the following: ■ Progressive neurological deterioration referable to the lesion ■ Signs of mass effect on CT scan ■ Refractory intracranial hypertension ■ GCS of 6-8 with frontal or temporal contusion > 20 ml in volume with midline shift > 5mm and/or cistern compression on CT scan ■ Any lesion > 50 ml in volume ■ Any hematoma more than 20 ml in the posterior fossa. Surgery is performed through a classic trauma craniotomy that has been described earlier for the same reason it is in EDH and SDH; which offers a good exposure and access to the commonest areas involved, temporal and frontal. The transcortical approach should be preformed in already necrotic or non-eloquent area. Any unsalvagable contused brain should be excised unless present in an eloquent area. Irrigation with hydrogen peroxide is recommended to secure homeostasis. After that, Gelfoam and Surgicel are applied in the hematoma bed followed by the routine closure. Patients who are elected to be managed conservatively should be admitted to ICU with an hourly neurological examination, continues ICP monitoring and serial CT scans. The over all outcome of ICH and cerebral contusions is relatively better than SDH with mortality rate ranging from 11-30% and functional recovery of 72.2% 2.

Diffuse Brain Injury: Concussion: is a clinical definition. It is the post traumatic state that results in an alteration of the level of consciousness. Classically, there is a brief period of loss of consciousness with a variable degree of retrograde or anterograde amnesia. No specific definition of “brief period” has been agreed on yet. It was thought that no anatomical or physiological damages occur in concussion but new evidence proved that concussions are basically a mild form of diffuse axonal injury. The majority of patients will improve eventually with no neurological sequelae but unfortunately some will have persistent neurological deficits. Concussions demonstrate a cumulative affect as seen in boxers which eventually can result in chronic dementia and cerebral atrophy. Concussions are thought of as mild head injury 3,4,16. Diffuse axonal injury: is a primary brain injury resulting from an accelerating-decelerating type of injury. The sudden deceleration produces a shearing force that disrupts axons and small vessels. Axonal injury causes localized transport failures in the axon, leading to swelling and often lysis of the axon with wallerian degeneration 16. DAI is the cause behind loss of consciousness in head trauma patients due to its effect on reticular formation. These lesions are demonstrated as hyperintense lesions in T2W MRI . CT scan usually fails to show any changes and might appear normal in comatosed patients. Pathologically, DAI is classically presented as gross focal hemorrhagic lesions in the corpus callosum and dorsolateral quadrant of the mid brain and pons with microscopic changes showing axonal retraction ball, and degeneration of white matter fiber tract 4.

Head Trauma

675

Cerebral edema: cerebral edema is divided into two types, vasogenic edema and cytotoxic edema. Cytotoxic edema is predominantly responsible for post traumatic brain edema. It is the most important contributing factor in increasing the intracranial pressure which subsequently decreases the cerebral perfusion leading to what is known as secondary brain injury. However new evidence demonstrated that cytotoxic edema cannot raise ICP to lethal levels 17. In CT scan cerebral edema can be appreciated as hypodensity in the white and grey matter. Case Demonstartion: A 22-year-old medical student was thrown out of his car as he was driving at a high speed and crashed to another car. He immediately lost consciousness and was brought to the Emergency Room. At arrival, he was unconscious GCS was 5. Pupils were normal in size and both were normally responding to light. No sign of clear lateralization. Patient was intubated and ventilated. Urgent CT scan was done and showed subarachnoid hemorrhage and brain edema. Intraventricular ICP sensor was inserted and the ICP monitor was connected. The patient was treated by dehydration methods and was given Manittol 20 % and Lasix. Repeated CT-Scan after 2 weeks showed marked brain atrophy that indicated cellular and axonal damage. Brain MRI was performed 3 weeks later, and showed multiple areas of high intense signals and brain atrophy indicating diffuse axonal injury, (Figure 9).

Fig. 9 T2W Brain MRI shows areas of high intense signals indicating diffuse axonal injury and generalized brain atrophy

The patient was extubated after 10 days, but remained disoriented, agitated, unattentive and some memory loss. He suffered attacks of grandmal epilepsy, which was controlled by phenytoin 100 mg three times a day. Intracranial pressure: In the 19th century Professors Monro and Kelly hypothesized that intracranial pressure is determined by the volume of the brain, blood, and CSF. To maintain a constant pressure, a change in the volume of one of these compartments has to be compensated by another. Since these components are confined in a rigid container (closed skull), compensation can be achieved to a degree. Beyond that, compensation is impossible and therefore, ICP rises dramatically. The importance of ICP in TBI patients lies in the fact that, an increased ICP causes a reduction in cerebral perfusion pressure (CPP) and

676 Head Trauma cerebral blood flow (CBF) which may subsequently lead to secondary ischemic cerebral injury 18. Therefore, high ICP in severe TBI is a significant predictor of worse outcome. CPP is a major determinant of CBF; it is defined as the mean arterial pressure minus the intracranial pressure. A concept known as pressure autoregulation maintains the CBF constant in a range of CPP between 40-150mmHg. This is achieved by a dynamic system of arterial vasoconstriction and dilatation. A pressure above 150 mmHg will maximally vasodilate the vessels and increases the CBF and on the other hand, a pressure below 40 mmHg will collapse the vessel wall and decreases the CBF 7. So, out of the normal limits the auto regulation is lost and the CBF is then directly related to the MAP and ICP. For example, a simple cough will elevate the ICP markedly consequently reducing the CBF. It has to be noted that CBF differs from cerebral blood volume (CBV). CBF is defined as the physiological parameter that assures cerebral perfusion and adequate oxygenation while CBV is defined as the total intracranial blood content, which is a major determent of ICP. The importance of that lies in the fact that CBV can be reduced to control ICP while maintaining an adequate degree of CBF 7. ICP normally varies with age, body position and clinical condition. Table 1, shows the range of normal ICP in each population. Table 1 The range of normal ICP in each population.

ICP monitoring: The guideline recommended by The Brain Trauma Foundation joint publication 19, is adopted in our practice. ICP monitoring is indicated in patients with: ■ Severe head injury and an abnormal CT scan ■ Normal CT scan and ≥ 2 of the following risk factor at admission (SBP 40 years, and unilateral or bilateral motor posturing) Severe head injury is defined as a post resuscitation GCS of < 9. Abnormal CT scan is a CT scan that shows hematomas, contusions, edema and basal cistern effacement. Mild and moderate head injuries are not an indication for ICP monitoring; it is generally left to the discretion of the treating physician. In situations for example, where a patient with moderate head injury presents with a contusion in the temporal lobe, ICP monitoring can be implicated to avoid or detect any delayed sequale.

Head Trauma

677

Management of increased ICP The following are general measures that should be implemented in order to normalize the ICP: 1. Head elevation at 30 degrees while the neck maintained at neutral position; it has the beneficial effect of reducing the ICP immediately with out a change in the CBF. 2. Tight control of blood pressure; it is crucial to avoid any drop of systolic BP < 90mmHg. A single drop in the SBP < 90mmHg was associated with doubled risk of morbidity and mortality. 3. Adequate oxygenation; hypoxia defined as PO2 < 60 mm Hg must be avoided. If patient’s GCS drops below 9, intubation is mandatory to insure better oxygenation and eliminate the risk of aspiration. Normocarbia is recommended in patients with severe head injury, defined as PaCO2 = 35-40 mmHg. 4. Avoid anemia; low hemoglobin levels affects negatively brain tissue oxygen delivery and therefore promote secondary brain injury. Most centers recommend transfusion of PRBC in patients with Hgb < 7. Studies defining the optimal hemoglobin concentration in neurocritical patients are lacking, but a restrictive transfusion policy seems to be safe and is often recommended 20. 5. Light sedation; it reduces HTN that is associated with unnecessary movement and agitation. 6. CSF drainage; can be an effective method to decrease an increasing ICP. Hyperosmolar therapy could be used as an adjunct to CSF drainage from the initial phases of the trauma, more so if there is lack of CSF drainage. 7. Osmotherapy (or hyperosmolar therapy); mannitol and hypertonic saline have been used as hyperosmoler agents to decrease post-traumatic cerebral edema and ICP. The latest evidence provided in the literature proved mannitol at doses 0.25mg/kg – 1gm/kg to be superior and more effective not only in decreasing the ICP but also in improving the CBF. Decompressive craniotomy is considered in some cases; for patients with refractory intracranial hypertension and diffuse parenchymal injury with clinical and radiographic evidence of herniation bifrontal or unilateral frontotemproparital decompressive craniotomy within 48h is an option. Anterior temporal or frontal lobectomy could be undertaken if these areas are contused. Systemic management of TBI patients: 1. Nutrition, patients should be fed to attain full caloric replacement by day 7 post-injury. 2. Anti epileptic, post-traumatic seizures are classified into early PTS and late

678 Head Trauma PTS. Early PTS are seizures occurring within 7 days of injury while late PTS are seizures occurring after 7 days. Routine seizure prophylaxis for more than 1 week following a TBI is not recommended. Phenytoin and valporate were found to reduce the incidence of early PTS but unfortunately, valporate was associated with a higher mortality rate. The management of late PTS is similar to the management of any new onset seizures. 3. DVT prophylaxis, there is class 3 evidence that recommends the prophylactic application of intermittent pneumatic stockings or/and the prophylactic administration of low molecular weighted heparin. However, an increased risk of intracranial hematoma expansion was observed in patients who received pharmacological therapy. 4. Stress ulceration prophylaxis should be considered.

REFERENCES 1. Maas AI, Stocchetti N, Bullock R . "Moderate and severe traumatic brain injury in adults". Lancet Neurology 7 (8): 728–41,august 2008. 2. Moppett I. K.: Traumatic brain injury: assessment, resuscitation and early management. British Journal of Anesthesia 99 (1): 18-31 2007. 3. Sumas M. and Narayan R.: Head injury. In Grossman R. and Loftus C.: Principles of neurosurgery. 2nd ed. Lippincott-Raven Publishers, pp. 117-155, 1999. 4. Liau L., Bergsneider M., and Becker D.: Pathology and pathophysiology of head injury. In Youmans J. R.: Neurological surgery: a comprehensive reference guide to the diagnosis and management of neurosurgical problems. 4th ed. W.B. Saunders, pp. 1549-1585, 1996. 5. Bullock M., Chesnut R, Ghajar, et al: Surgical management of acute epidural hematoma. In Guidelines for the surgical management of traumatic brain injury. Neurosurg Supp, 58(3): S2-7-15, 2006. 6. Mathur V. and Jallo J.: Summary and synopsis of the brain trauma foundation head injury guidelines. In Loftus C.M.: Neurosurgical emergencies. 2nd ed. Thieme Medical Publishers, Inc, pp. 172-180, 2008. 7. Dusick J., Kelly D., Vespa P., and Becker D.: Surgical management of severe closed head injury in adults. In Schmidek H. H., and Roberts D. W.: Schmidek & Sweet Operative Neurosurgical Techniques: indications, methods and results. 5th ed. Elsevier Inc, pp. 4952, 2006. 8. Timmons S.D.: Extra-axial hematoma. In Loftus C.M.: Neurosurgical emergencies. 2nd ed. Thieme Medical Publishers, Inc, pp. 54-56, 2008. 9. Bullock M R, Chesnut R, Ghajar J, et al.: Surgical mangemnet of acute subdural hematoma. In Guidelines for the surgical management of traumatic brain injury. Neurosurg Supp, 58(3): S2-16-24, 2006. 10. Jennett B., Galbraith S.: Complications after head injury. In An introduction to neurosurgery. 4th edition. William Heinemann medical books limited, pp. 241, 1983. 11. Zumkeller M, Behrmann R, Heissler H et al.: Computed tomographic criteria and survival rate for patients with acute subdural hematoma. Neurosurgery, 39:708-713, 1996. 12. Adhiyaman V, Asghar M, Ganeshram KN, et al.: Chronic subdural hematoma in the eldery. Postgrad Med J, 78: 71-75, 2002. 13. Grossman R. and Yousem D.: Head Trauma. In Neuroradiology: the requisites. 2nd

Head Trauma

679

edition. Elsevier Inc, pp. 254, 2003. 14. Gudeman S., Kishore P., and Miller J.: The genesis and significance of delayed traumatic intracerebral hematoma. Neurosurgery, vol 5: 309-313, 1979. 15. Bullock M R, Chesnut R, Ghajar J, et al.: Surgical management of traumatic parenchymal lesions. In Guidelines for the surgical management of traumatic brain injury. Neurosurg Supp, 58(3): S2-25-38, 2006. 16. Alexander M.: Mild traumatic brain injury: pathophysiology, natural history, and clinical management. Neurol, 45: 1253-1260, 1995. 17. Rosenblum W.: Cytotoxic edema: Monitoring its magnitude and contribution to brain swelling. J Neuropathol Exp Neurol, vol 66 num.9, 2007 18. Smith M.: Monitoring intracranial pressure in traumatic brain injury. Anesthesia & Analgesia, Vol. 106, No. 1, Jan 2008 19. The Brain Trauma Foundation. The American Association of Neurological Surgeons. The Joint Section on Neurotrauma and Critical Care. Indications for intracranial pressure monitoring. J Neurotrauma , 24:S37-44, 2007. 20. Leal-Noval et al. Optimal hemoglobin concentration in patients with subarachnoid hemorrhage, acute ischemic stroke and traumatic brain injury. Current Opinion in Critical Care , 14:156–162, 2008.

680

Neurotrauma, The ABC’s SHARAD S. RAJAMANI MCh, FICS Consultant Neurosurgeon, ColumbiaAsia Hospitals Key words: Neurotrauma, initial assessment, care algorithms, protocols

Introduction Trauma is the single largest killer of youth. A large number of trauma patients die from head injury. A number of these deaths are preventable by prompt decisive action in the first few minutes to an hour after trauma, the “Golden Hour”. Most cranio-spinal trauma is easily manageable at a centre with facilities for emergency care and access to a CT scan unit in close proximity with the centre.

Statistics and Demographics Trauma is a killer, involving the youth and the middle aged, with a loss of man-hours at work. It has been said “if trauma was to be treated as a disease process, the amount of resources spent on trauma research should exceed all other research put together”. In reality, trauma has never been given its due importance. Most advancement and research in trauma stemmed from the second world wars. During the past few years, the world of medicine has woken up to the “pandemic” called trauma! Most trauma are due to road accidents (RTA) and a much smaller figure from falls, assaults and muggings. Also, the higher speed means a more severe an injury, the amount of force generated is directly proportional to the velocity (E=mc). It is estimated that nearly 6 million road accidents are recorded, and around 150,000 succumb to their injuries at the site (Statistics from 51 member countries of UNECE). Road traffic injuries are the leading cause (60%) of Traumatic Brain Injury (TBI) followed by falls (20-25%) and other violence (10%). Driving Under the Influence is known to be the causative factor among 43-76% of accidents at the time of injury. Amongst road accidents, 70% of the deaths are following traumatic brain injuries. Rehabilitation needs of brain injured persons are significantly high and increases from year to year. This affects man-hours, and resource utilisation , which actually is a large sum. Hence stress on prevention, pre-hospital care and rehabilitation in the rapidly

Neurotrauma, The ABC’s

681

changing environments are being stressed upon to reduce the burden of TBI. The think-first program stresses on the need of planning prior to travel by motor vehicle. It also insists on stress-free driving.

Pre-Hospital Transfer The primary and most important period of any trauma is the first one hour. This is where a sizeable number of lives could be saved. Unfortunately neurosurgeons are not primarily involved in this part of the care, however, the effects of pre-hospital transfer and emergency services affect the outcome. The extrication process is cumbersome, awkward and messy. It might involve the placement of lines in the most awkward setting, and the extrication of individuals in the vertical position. This could easily adversely affect the outcome, specially in those with spinal injuries. A team of emergency medical personnel is best designed for the purpose of extrication and transport consisting of two medical staff, and a driver with or without the presence of a supporting staff. A primary survey is necessary in the pre-hospital transfer, securing of an IV access with a wide bore needle (16G or 18G) is recommended so as to speed up the process of resuscitation is also mandated. A fluid like Lactated Ringers Solution or 0.9% saline is instituted and kept on flow during the transfer, the rate dependant on the blood pressure of the victim.

The steps of evaluation can be divided into two overheads: 1. Assessment of the danger to the medical personnel: The dangers to personnel are Traffic on the road, the leaking fuel, fuel tank explosion, live electrical wires obstructing the evacuation etc. This task is usually assigned to the driver of the vehicle. He also parks the ambulance in a prominent spot on the road, with the lights flashing, where movement of traffic is possible without endangering the evacuation team. At this point in time, it is preassigned to one of the medical staff to evaluate for imminent danger from wires, fuel leaks, instability of the vehicle etc. 2. Assessment of the patient: The patient is assessed using the ABCDE of the ATLS described in the next topic, and the consciousness is assessed using the AVPU technique. An important point to note is that whenever Primary survey is being performed, the treatment is also initiated and maintained. Only once the primary survey and secondary survey is complete, should one note the history from an eye witness, and preferably bring him/her back to the hospital for further questioning by the doctor.

682 Head Trauma Resuscitation is performed as the primary survey or evaluation is being carried out. At no point in time, should the ABC’s be overlooked. While these patients are resuscitated for their vital parameters, the airway, breathing and circulation, with an airway and bag-valve-mask ventilation, or rarely the Bagvalve-tube ventilation. Splinting of fractured limbs is recommended to minimise further blood loss. The EMT team is in contact with the hospital relaying data and condition of the patient. This prepares the Emergency services to plan and receive the patients. In realty two techniques of evacuation are performed by the Emergency team: 1. Snatch and Scoot. 2. Stay and Stabilise. Unless all facilities are available in the ambulance including blood and emergency procedure kits, with adequately trained individuals, most teams do not attempt the “stay and stabilise” method. In fact most centres over the world prefer to use the first technique. However, when the former is used extensively, some degree of stabilisation is performed in the ambulance, vital parameter assessments, IV access, bag-valve-mask ventilation, while the ambulance is rushing off to the hospital.

Emergency Services Once the patient is in the emergency services area the steps followed are: Assessment of the patient: While assessment of the patient begins in the vehicle and where evaluation of his vital parameters and an IV line is inserted. The patient is put on a cervical collar. If this is not available freely as in the case of most peripheral hospitals, two-three newspapers folded over and over again to fit the neck is used, making sure that this does not compromise the airway or the venous return from the neck.

The Adage

“ALL PATIENTS WITH TRAUMA HAVE A CERVICAL SPINE INJURY – UNLESS PROVEN OTHERWISE” Is borne in mind while managing all cranial trauma. The assessment of a traumatised patient is divided into two broad categories as per the ATLS protocol. The Primary Survey and the Secondary Survey. It would be prudent to mention the ATLS hands when dealing with trauma - Open hands, arms flexed at the elbows, adducted at the shoulder.

Neurotrauma, The ABC’s

683

The Primary Survey consists of a. Airway: Airway assessment for obstruction is very important. This could be foreign bodies, tongue falling back, broken teeth etc. For a tongue falling back, the “Jaw-thrust manoeuvre” effective in alleviating the obstruction. While using a finger to clear the airway, it is advisable to be extremely careful lest the examiners finger is a casualty between the teeth of the semiconscious patients, who have a tendency to bite on it. An alternative method is to insert the blade of a laryngoscope, before inserting a finger. An oral airway might help, if the tongue continues to fall back, but only if the patient tolerates it. Most semiconscious or unconscious patients spit it out. In such situations, if there is no bleeding from the nose a no 6 or 6.5 endotracheal tube can be inserted into the nose, to the pharynx as a naso-pharyngeal airway. If the obstruction is below the reach of a finger or suction device, an emergency cricothyroidotomy might be needed. This is done by feeling the cricothyroid membrane at the lower border of the thyroid cartilage, in the midline. The lower margin of this membrane usually has a shallow notch, and stab made into it using a #15 blade. The airway can be kept open by inserting an uncuffed paediatric endotracheal tube of size not exceeding #5. This would help maintaining the airway. The tube can be inserted as far as the carina. One word of caution – the tube can slip into one of the main bronchi and a collapse of the other lung might occur. b. Breathing: Following assessment of the airway, an assessment of whether the patient is breathing or not is performed. If the patient is breathing, is it shallow, adequate, or there is one of the neurological kinds of respiration. If the patient is not breathing adequately, a bag-valve-mask is ideal to obtain temporary ventilatory support, and this can be replaced by intubation, when the patient’s saturation has improved, or the equipment is ready. During the procedure of intubation or ventilation or checking for airway, prime importance is given to the stability of the cervical spine. c. This can be achieved with the help of a trained personnel watching for any flexion during intubation. The rule is “No Movement Is Best”. But that may always not be possible, and small degrees of movement would definitely occur, and flexion is much worse than extension. d. Circulation: The assessment of circulation is initially done by assessing the volume of the pulse the rate of the pulse, and the peripheral circulation capillary refill rates etc. In cold weather, the limbs might be cold, with a normal volume, and in patients with total cervical or dorsal spinal injuries, the periphery might be warm while the patient in shock. A quick guide to assessment is when the dorsalis pedis is felt in adults, the blood pressure is thought to be over 100mmHg, systolic. In any head trauma, a minimum mean pressure of 70mmHg is necessary to perfuse the brain. In the event of a suspicion of a low volume state, an IV access with a wide bore cannula – 16 or 14 gauge needle (Venflon / Insyte

684 Head Trauma / Jelco etc) is preferred, and if needed multiple cannulae. In general, low volume states in the acute setting of trauma are due to fluid or blood loss either externally or internally. This warrants fluid replacement. The fluid of choice is ringer lactate or in extreme situations penta or hexa starch (haesteril). This technique is usually adequate. Once the source of blood loss is identified and controlled, blood can be transfused rapidly. In extreme situations, early blood transfusions would become necessary. It is very tempting to insert a long line or central venous access in the acute setting, especially at the first instance. This does not add to the process of resuscitation as a rule, but should be considered once the blood pressure is stabilised. The presence of tachycardia usually indicates the impending hypotension, and should be aggressively treated. There is hypotension seen occasionally with spinal cord injuries and this manifests as bradycardia with hypotension. Hypotension secondary to decompensation of the brainstem and the autonomic nervous system is seen in the setting of deep coma, pupillary dilatation, and respiratory signs. There is no accompanying tachycardia in these situations. e. Disability: The assessment of disability includes the assessment of: The sensorium: This can be divided into 4 stages or levels. These are • Awake, • Responds to Verbal stimulus • Responds to Painful stimulus • Unconscious The AVPU is a quick assessment, to get a brief idea of the conscious level later a more detailed assessment should be performed. An assessment of the limbs and sites of bleeding is done and all efforts are made to arrest any sources of bleeding. e. Exposure: In the emergency room, exposure of the patient to look for any injuries or lacerations, fractures, to look for active blood loss. Under controlled circumstances a turning of the patient to evaluate the back is permissible, but with adequate help – One person for the head and neck – preferably the doctor, one for the shoulders, and hip, and one for the lower limbs (A minimum of three personnel).

In Summary, the following steps have to be taken in receiving a patient with head trauma: a. Put the patient on a collar and spinal board, b. Assess the airway, c. Assess Breathing, d. Assess Circulation and if with a staff nurse, the pulse rate and volume, blood pressure too. e. Assess Disability

Neurotrauma, The ABC’s

685

f. Expose the patient and assess the injuries, fractures, and bleeding sites. This should continue along with resuscitative measures, in the form of IV access, securing of airway, and securing of respiratory status. At any given point of time, if there is a lapse of the ABC, immediate attention should be paid to it, reverting back. Following the primary survey, a secondary survey is carried out, this is done with the patient as a whole and not system related.

Secondary survey consists of a. General physical examination – including the vital parameters. Look for identification marks. b. Examination of the CNS: Examination of the GCS – score the patient what ever be the situation. c. Examination of the head, for lacerations, and depressed/linear fractures. d. Examination the Head and neck pupils, facial lacerations, and facial fractures. e. Examination for cervical spine tenderness. f. Examination of the chest – respiratory rate, breath sounds, and their equality, tracheal deviation, subcutaneous emphysema. g. Examination of the abdomen – abdominal distention, fullness of the flanks, shifting dullness, loss of liver dullness, bruising on the abdomen, external genitalia, rectal examination. h. Examination of the limbs for hematoma, fractures, undue mobility at joints, for lacerations, and peripheral pulses, weakness of the limbs. i. Log-rolling, and examination for injuries to the back and the anal tone in the partly conscious and unconscious patient. A history record sheet to deal with polytrauma might be useful so as not to miss out any findings. Following this a specific system-oriented management is considered. To simplify the same, we have suggested an algorithm which would cover almost all situations. For the purpose of simplification, we have used only two parameters in the assessment of these patients and further management - the GCS and Pupils The Glasgow coma score, which is a score first described in 1976 by Teasdale and Jennett. They have divided the assessment of a head injured patient into three basic categories, depending on the response of the patient, motor, verbal and eye opening. They have been scored between 1-6 for motor, 1-5 for verbal and 1-4 for eye opening. This scoring system has stood the test of time and the tribulations of a number of other scoring systems as from Adelaide, the APACHE series etc. The mainstay of the scoring system is the simplicity and consistency with which

686 Head Trauma one can assess the patient. It has also been found that the chances of an inter-observer variance are not more than “1” in a given time frame. The scoring system has a series of major drawbacks; however one still continues to use this system. The scoring system uses three parameters, Best Eye Opening Response, Best Motor response, Best Verbal response, also called EMV.

The Glasgow Coma Score The usual doubts while assessing the GCS are: a. How, where and what kind of painful stimulus is used ? The painful stimuli used are Pinch to the anterior axillary fold, supra-orbital pressure, sternal pressure, nail-bed pressure. b. What is an abnormal extensor response ? The abnormal extensor response is described as flexion at the thumb, the fingers, the wrist, extension at the elbow, pronation of the forearm, extension of the shoulder, internal rotation of the shoulder and extension of the neck and back, with extension at the lower limbs (also called the decorticate posturing.) c. What is an abnormal flexor response ? The abnormal flexor response is the same as the extensor response except for flexion at the elbow. The hand usually does not reach cranial to the shoulder joint. d. What is a flexor / withdrawal response ? The flexor response is described as flexion of the upper limb, usually past the shoulder, however, the thumb, fingers and the palm are open, and do not form the classical flexed, closed fist posture. Also the lower limbs tend to flex instead of extension, and painful stimulus to the limb causes the limb to withdraw. The movement is not localizing movement, although the hand might come close to the region of obnoxious stimulus. Withdrawal to pain is noticed in these patients. There are some drawbacks of the Glasgow coma Score and these are a. It does not take into account the general condition of the patient. b. There are no parameters for pupillary size, shape or symmetry.

Neurotrauma, The ABC’s

687

c. Involvement of other organ injuries can adversely affect the management protocols, and are not recorded by the GCS. d. Spinal injuries would change the GCS specially in the disoriented or unconscious patient, where the motor response would be altered as low as M1. There are also some situations where the GCS might be altered or the readings might not be right. a. Patient has hypoxia b. The patient is hypotensive. c. Has had a seizure d. Is febrile e. consumed alcohol/drugs f. Has received a previous sedative. Despite these drawbacks, the scoring system has stood the test of time. Therefore the lacunae is filled by adding the information, specially the positive ones. Along with the GCS, the pupillary size is also mentioned. The most important finding is a dilated and non-reacting pupil, or an asymmetric non-reacting pupil. There may be variations in the absolute size of the pupil from 1mm to 6 mm, provided they are reacting, and equal, they should not arouse alarm. However, a 1mm pupil usually does not react. Dilated pupils may be seen in acute panic states, post-traumatic psychological shock or in patients with severe pain, and also if the pupils are assessed within seconds of assessing the GCS. Around 16% of the population has some pupillary asymmetry however it would advisable to assume that the pupillary asymmetry is secondary to increasing intracranial pressure, and err on the side of evaluating for it. The important point to note is that the pupil dilates first on the side of the lesion. Hence the presence of an ipsilateral papillary dilatation with contralateral hemiparesis would suggest a mass lesion, causing lateral trans-tentorial herniation (coning) on the side of the pupillary dilatation.

Systemic Examination - Neurological: A detailed systemic examination of the central nervous system is mandated. The details of which are dealt with in another chapter.

Management in Emergency Services After an assessment has been made, an initial stabilization of the patient has been performed; the patient is then managed according to a protocol being used at any medical center. An ideal protocol-based treatment covers for most contingencies and leaves no ambiguity in the treatment of head injured patients.

688 Head Trauma While this is difficult to accomplish, a protocol is created to incorporate most scenarios. These protocols help as guidelines, and as time goes by one tends to modify, never breaching the broad outlines.

REFERENCES 1. Country Reports on Road Safety Performance, from 44 member countries; September 2006: International Transport Forum. 2. Neurotrauma; Raj K. Narayan, John T. Povlishock, James E Wilberger 3. National Institute for Health Care and Clinical Excellence - 2007 Guidelines for Head Injury 4. Guidelines for the management of Severe Traumatic Brain Injury, Project for Brain Trauma Foundation;3rd Edition, 2007

689

Management of severe traumatic brain injury (TBI) ALEXANDER POTAPOV; L. LIKHTERMAN Burdenko Neurosurgical Institute, Russia Key words: traumatic brain injury (TBI), scull fracture, epidural haematoma (EDH), subdural haematoma (SDH), cerebral contusion, difuse axonal injury (DAI)

Introduction State of consciousness is the most important integral factor of TBI severity. There is a general agreement that in severe TBI patients have a hospital admission Glasgow Coma Scale (GCS) of 8 or less. The overall incidence of severe forms of TBI is marked in 5-7% of all head-injured patients. According to clinical and morphological characteristics TBI is classified into the following severe forms: traumatic lacerations and contusions, intracranial haematomas and haemorrhages (epidural, subdural, intracerebral, intraventricular, subarachnoid), diffuse axonal injuries and crush of the head. Their biomechanics and pathogenesis is different. Severe focal damages – lacerations and contusions, intracerebral and subdural and epidural haematomas as well as depressed skull fractures are produced by coup-and contre coup mechanism of damage; diffuse brain injury is produced by acceleration of the head without impact, and typical combination of kinetic and static energy forces cause long-term head compression. Primary management of patients with TBI and its sequelae starts with intensive care followed by differentiated treatment. Beside direct surgery there’s been marked a widespread use of methods of minimally invasive and reconstructive neurosurgery.

1. Brief summary of guidelines for the management of severe TBI and experience of Burdenko Neurosurgical Institute Modern neurotraumatology has gained a great experience in diagnosis and management of different types and severity states of TBI summarized in evidencebased International and National Guidelines (Adelson P.D. et al (2003), Bullock R. et al (2006), Bratton S. et al (2007)). In this connection we find it reasonable to briefly summarize the main recommendations for the management of severe TBI and its surgical treatment based on the experience of Burdenko Institute. It is for this reason that we’ll report on recommendations for the management of severe TBI. 1.1. First aid for head-injured patients Priority should be given to the measures aimed at restoring (improving) and preserving vitally important functions: respiration (restoration of respiration, avoidance of hypoventilation disturbances – hypoxia, hyperkapnia) and blood circulation (evoidance

690 Head Trauma of hypovolemia, hypoxia and anemia). In inadequate independent respiration a series of special procedures providing respiratory tract permeability can be followed by intubation and artificial ventilation to ensure normal blood oxygenation and avoid hyperkapnia. Tracheobronchial sanation is possible after intubation procedure. Management of hypovolemia and arterial hypoxia should be started with infusion of colloids and crystalloids. Class I evidence showed that hypertonic NaCl (7,5%) saline, especially in combination with dextrans, proved to be more effective compared to isotonic saline. It was shown that 7,5% NaCl infusion resulted in quick normalization of blood circulation value without raise of intracranial pressure (ICP). Intravenous 4-6 ml/kg dosage for up to 5 minutes is recommended. It should be noted, however, that in patients with penetrating injuries it may cause internal haemorrhage. Emergence of symptoms of transtentorial herniations and neurological deterioration not attributable to extracranial causes should suggest raise of intracranial pressure. Such a situation requires urgent measures to be undertaken, i.e. the patient should be artificially hyperventilated. Mannitol is recommended to control intracranial hypertension with an adequate compensation of the blood circulation value. To provide optimal conditions for patient transportation, especially if psychomotor agitation or seizures are present, it is recommended to use sedatives. Short-term administration of myorelaxants is possible in patients with insufficient sedation. 1.2. Blood Pressure and Oxygenation At all stages of management of TBI (at trauma site, during transportation, in hospital) blood hypotension (systolic blood pressure < 90 mm Hg) and hypoxia (apnoe, cyanosis, PaO2 < 60 mm Hg or O2-saturation < 90%) should be urgently prevented or avoided. Blood pressure and oxygenation should be monitored. Mean blood pressure should be over 90 mm Hg throughout the whole intensive care period in order to preserve cerebral perfusion pressure (CPP) at the level > 60 mm Hg. In persistent hypoxia intubation and artificial ventilation are necessary. 1.3. Hyperosmolar Therapy Mannitol is effective for control of raised intracranial pressure at doses 0, 25 gm/kg to 1 g/kg body weight. In patients with a subdural haematoma (especially temporal lobe haematoma) undergoing surgical evacuation, an early preoperative single, high dose of Mannitol (1,2-1,4 gm/kg) is recommended or in patients in deep coma or diffuse brain swelling on CT scan. Arterial hypotension should be avoided. Mannitol is effective before monitoring of ICP for patients with transtentorial herniations or neurological deterioration not attributable to extracranial causes. To avoid kidney insufficiency it is recommended to hold blood osmolarity level below 320 mosm/l. Normovolemia should be preserved by fluid maintenance; catheterization of the urinary bladder is also recommended. Periodical bolus administration of Mannitol can be more effective than persistent infusion. 1.4. Infection Prophylaxis Periprocedural antibiotics for intubation should be administered to reduce the incidence of pneumonia.

Management of severe traumatic brain injury (TBI)

691

Early tracheostomy should be performed to reduce mechanical ventilation days. 1.5. Deep Vein Thrombosis Prophylaxis Compression stockings or intermittent pneumatic compression stockings are recommended, unless lower extremity injuries prevent their use. Use should be continued until patients are ambulatory. 1.6. Indications for Intracranial Pressure Monitoring Intracranial pressure (ICP) should be monitored in all salvaged patients with a severe TBI (GCS 3-8) and an abnormal CT scan. An abnormal CT scan is the one that reveals haematomas, contusions, swelling, compressed basal cisterns. ICP monitoring is indicated in patients with severe TBI with a normal CT scan if two of the following features are noted at admission: age over 40 years, unilateral or bilateral motor posturing, or systolic blood pressure (BP) < 90 mm Hg. ICP monitoring is not indicated in patients with mild or moderate TBI. 1.7 Intracranial Pressure Monitoring Technology The ventricular catheter connected to an external strain gauge is the most accurate, low cost and reliable method of monitoring intracranial pressure. It also allows to drain CSF for treatment purposes. Subarachnoid, subdural and epidural monitors are less accurate. Parencymal ICP monitors can not be recalibrated during monitoring. 1.8. Intracranial Pressure Thresholds Intracranial pressure thresholds above 20 mm Hg are associated with poor outcomes. Interpretation and treatment of ICP based on any threshold be corroborated by clinical and brain CT findings. 1.9. Cerebral Perfusion Thresholds Cerebral perfusion pressure above 60 mm Hg should be preserved. CPP 30 cm3 for temporal localization; maximal intracerebral haematoma size > 4 cm 4) CT and MRI evidence of lateral dislocation (midline shift > 5 mm and/or axial brain dislocation (the enveloping cistern is roughly deformed) According to recommendations by M. Bullock et al. (2006), surgical treatment is indicated in patients with traumatic parenchymal brain damages, progressing neurological deterioration, intracranial hypertension refractory to medical treatment and with signs of mass-effect on CT. Indications for medical (conservative) treatment of focal contusions and intracerebral haematomas are: 1) state of consciousness: moderate or deep obnubilation (GCS > 10); 2) absence of evident clinical signs of brainstem dislocation 3) CT or MRI signs of contusion < 50 cm3 for frontal localization and < 30 cm3 – for temporal localization; maximal intracerebral haematoma diameter < 4 cm 4) absence of CT or MRI evidence of midline shift < 5 mm and axial brain dislocation (the enveloping cistern is saved or slightly deformed) According to recommendations of M. Bullock et al. (2006) focal parenchymal lesions should be treated conservatively in patients with slight neurological deficit, controlled intracranial pressure and absent signs of mass-effect on CT. On should remember that major part of victims with severe focal traumatic brain damages belongs to the so-called risk group. Intensive therapy, dynamic clinical observations with repeated CT or MRI examinations are indicated in this group of patients. 3.2. Epidural or Subdural Haematomas Epidural or subdural haematoma is the main surgical form of severe traumatic brain injury. According to the experience of Burdenko Neurosurgical Institute, urgent surgical evacuation is indicated in the bulk of patients with acute or subacute extracerebral haematomas if the following clinical signs are noted: 1) expressed brain compression 2) repeated neurological deterioration or aggravated extinction of consciousness after total or erased lucid interval 3) the volume of supratentorial haematomas (by CT and MRI data) > 30 cm3 for

696 Head Trauma temporal localization and > 40 ml for any other localization with the volume of subtentorial haematomas > 20 cm3 or its width > 1,5 cm regardless the clinical phase of TBI, including asymptomatic haematomas 4) Surgery is indicated in patients with extracerebral haematomas if one of the following features is revealed by CT or MRI: lateral midline shifting > 5 mm, marked deformation of the basal cisterns, large compression of the homolateral ventricle, dislocation hydrocephalus regardless localization and volume of haematoma, if caused by the latter and not by associated skull or brain damages 5) open penetrating head injury or associated skull and brain damage (compressed fracture, intracerebral haematomas etc.) requiring surgical treatment despite the haematoma volume 6) low-volume (< 20 ml) epidural haematoma of the posterior fossa causing occlusive hydrocephalus revealed on clinical CT or MRI scans According to recommendations by M.R.Bullock et al.(2006) surgical evacuation is indicated in patients (despite Glasgow Comas Scale) with epidural haematoma volume > 30 cm3, subdural haematoma width > 10 mm and midline shift > 5 mm demonstrated on CT. Surgical evacuation is indicated in comatose patients (GCS < 9) if the following clinical signs are present: - subdural haematoma width < 10 mm; - midline shift < 5 mm; - GCS drop by 2 items at the interval between the moment of trauma and inhospital admission; - anisocoria or fixed pupils; - ICP > 20 mm Hg; Based on methods of neurovisualization there was outlined a group of patients with traumatic extracerebral haematomas (subdural or epidural) who can benefit from conservative treatment and show favourable outcomes: The indications for conservative treatment are: 1) haematoma volume < 30 ml for temporal localization and < 40 ml for frontal or other supratentorial localization on condition minor non-aggravating cerebral and focal symptoms are present, and clinical signs of brain dislocation are absent (and ICP is below 25 mm Hg); a 5-mm midline shift is possible on CT or MRI scans on condition it does not cause dislocation hydrocephalus. 2) asymptomatic haematoma volume < 50 ml 3) small-size epidural or subdural haematomas with clinical decompensation or CT - MRI changes caused by associated focal or diffuse brain damage 4) subtentorial epidural haematoma volume < 20 ml in patients with minimal non-aggravating neurological deterioration and without signs of CSF pathways blockade 5) subdural haematoma width < 10 mm in case of clear consciousness, minor midline shift (up to 3-5 mm) and absence of basal cistern compression According to recommendations developed by M. Bullock et al. (2006), patients with epidural haematomas with diameter of < 30 cm3 , width < 15 mm and midline shift < 5 mm, with GCS score of 8 and without neurological deterioration can be treated

Management of severe traumatic brain injury (TBI)

697

conservatively on condition regular CT control examinations are performed at a neurosurgical clinic. It should be specially stressed that conservative treatment of epidural and subdural haematomas requires dynamic neurological control, repeated CT or MRI examinations. That is why conservative treatment of epidural and subdural haematomas should be performed only in neurosurgical clinics. 3.3 Depressed Skull Fractures Patients with open skull fractures and depressions exceeding the bone width should be surgically treated in order to prevent infectious complications. Depressed fractures can be treated conservatively if there is no clinical or radiological evidence of dura mater damage, intracranial haematoma, frontal sinus involvement, marked cosmetic deformation, wound infection, pneumocephalus with bone compression not exceeding its width. 3.4. Posterior Fossa Damage Surgical treatment is indicated in patients with CT evidence of mass-effect or neurological deterioration caused by posterior fossa damage. Mass-effect on CT scans in these cases is presented by deformation, dislocation or obliteration of the IY ventricle, compressed basal cisterns or their absence on CT and occlusive hydrocephalus. Patients with posterior fossa damage should take conservative treatment with regular CT or MRI examinations, provided there is no signs of mass-effect on CT scans or neurological dysfunction without rough disturbances. 3.5 Diffuse Axonal Damage (DAI) Patients in the acute stage of DAI apparent on CT or MRI should avoid any operative intervention. Surgery is indicated only in patients with DAI accompanied by focal damages (depressed fractures, epidural or subdural haematomas etc) or diffuse brain swelling with a risk of brainstem compression. DAI in these conditions is often accompanied by subdural collections of CSF above the anterior structures of large hemispheres. By mistake they can be taken for large-size hygromas and as such surgically removed. One should avoid surgery because of a non-aggressive character of CSF collections and a tendency to resorp with time. Severity and outcome of DAI depend not only on primary axonal damage but also on secondary brain damage (oedema, swelling, metabolism disturbances) and extracranial complications. Effective management of DAI should be aimed at preventing secondary brain damage and extracranial pathology. Minimally invasive, endovascular or stereotactic surgery is indicated in patients in the late stage of DAI in order to avoid surgical complications like normotensive posttraumatic hydrocephalus, carotid-cavernous fistulas, chronic subdural haematomas etc. Prognosis and outcome in 6 months following DAI depend on duration and depth of coma. According to the experience of Burdenko Neurosurgical Institute, the survived majority of patients in coma lasting 7 days showed moderate disability and even good recovery. In coma lasting 8 days or more the prognosis was rather poor - severe disability or vegetative state.

698 Head Trauma The correlation analysis showed an evidently significant dependence of outcome of DAI on duration and depth of coma. The longer and deeper coma is, the worse prognosis (outcome) is expected. Age factor here plays an important role. The analysis showed a close correlation existing between duration of coma and outcomes in children and adults; this correlation was significantly higher in children. Children in prolonged coma develop severe disability or vegetative state with a relatively low mortality rate. Adults usually show high morality rate and relatively moderate disability. Long-term (1-8 years) follow-up of DAI shows good recovery predominance in children. At the same time, this age group shows the longest duration of vegetative state.

Conclusion Though incidence of TBI is considerably lower compared to mild head injury, it remains the main cause of mortality, long-lasting sequelae and disability among population and is regarded as a serious economic and social burden for the family, society and state. That is why correct organization of neurotraumatological management for patients with traumatic brain injuries is the primary task for Public Health Care in any country. Beside adequate intensive therapy and urgent surgery further steps are necessary in order to prevent secondary brain damage.

REFERENCES 1. Adelson P.D., Bratton S.L., Carney N.A. et al.// Guidelines for the acute medical management of severe traumatic brain injury in infants, children and adolescents//Pediatric Crit Care Med 2003; 4: S417-S491 2. Bullock R., Chestnut R., Ghair J. et al//Guidelines for the surgical management of traumatic brain injury//Neurosurgery, 2006, 58, S2—62 3. Bratton S., Bullock M.R., Carney N. et al//Guidelines for the management of severe traumatic brain injury. 3d Edition/J.Neurotrauma 2007, v.24, S.1 4. Potapov A., Kravchuk A., Zakharova N.//Head trauma, p. 807-919 in Book of Kornienko V., Pronin I. “Diagnostic neuroradiology”, 2009, Springer-Verlag, Berlin - Heidelberg

699

Neuromonitoring for Head Injury Monitoring of intracranial pressure and cerebral blood flow and metabolism -basic and advanced monitoring toolsNOBUYUKI KAWAI, M.D., KENYA KAWAKITA, M.D., TAKASHI TAMIYA, M.D. Department of Neurological Surgery, Kagawa University Faculty of Medicine Key words: brain tissue oxygen saturation, cerebral blood flow and metabolism, cerebral perfusion pressure (CPP), dynamic CT, intracranial pressure (ICP), jugular venous oxygen saturation (SjvO2), laser Doppler flowmetry (LDF), microdialysis, monitoring, near infrared spectroscopy (NIRS), positron emission tomography (PET), single photon emission tomography (SPECT), stable xenon CT, traumatic brain injury (TBI), transcranial Doppler (TCD)

Introduction The most important monitoring in practical neurosurgery is patient observation. Regular assessments of consciousness levels, verbal responses and motor responses should be performed and recorded according to the Glasgow Coma Scale (GCS) in the clinical flow chart. A witnessed deterioration in GCS or the development of new focal signs should be regarded as a life-threatening sign and mandate immediate CT scanning. In an unconscious, sedated patient in the intensive care unit (ICU), an assessment of intracranial pathology made by clinical examination is limited. Standard general monitoring for all such patients is required including oxygen saturation (SaO2), ECG, mean arterial blood pressure (MAP) and urine output. The brain-specific monitoring includes intracranial pressure (ICP) monitoring and cerebral blood flow (CBF) and metabolism monitoring. The primary goal of management for a critically ill patient is the prevention of secondary brain damage due to neuronal hypoxia and hypoperfusion. Ideal monitoring provides a continuous, objective, and readily interpretable measure of intracranial pathology even in an unconscious patient. As with any monitoring system, one would like to detect potentially harmful complications and intervene before they result in permanent morbidity and mortality. This chapter focuses on the applications and limitation of bedside monitoring of ICP, CBF, cerebral oxygenation and metabolism in the brain in patients with traumatic brain injury (TBI).

ICP monitoring: basic and very useful As the cranial vault is essentially a closed, fixed bony box, its volume is constant. This theory is described by the Monro-Kellie doctrine, proposed in the early 19th century:

700 Head Trauma v. intracranial (constant) = v. brain + v. CSF + v. blood + v. mass lesion As all these components are fluids, and non-compressible, once the cranial vault is filled, the pressure raises dramatically. Raised ICP may reduce the cerebral circulation by reducing the cerebral perfusion pressure (CPP) (defined as the difference between mean arterial pressure and ICP). As an intracranial mass lesion or edematous brain expands, some compensation is possible as cerebrospinal fluid (CSF) and blood move to the spinal canal and extracranial vasculature. Once this mechanism is fully exhausted, a rapid and steep rise in ICP is seen, even with only small changes in intracranial volume (Fig. 1).

Fig. 1 Volume-pressure curve. Edema and hematoma associated with head injury reduce compliance and pressure begins to rise earlier and more steeply.

Raised ICP is a common problem in patients with traumatic brain injury (TBI). Frequent causes are intracranial mass lesions, disorders of CSF circulation, brain edema, or more diffuse pathologic processes (e.g. hypercapnea). ICP monitoring provides continuous data regarding the pressure within the cranial vault. ICP monitoring may be required for patients with a GCS of 8 or less and is essential in patients in whom neurological assessment is unattainable (such as barbiturate therapy or neuromuscular blockade) (Fig. 2). Indications for ICP monitoring vary from unit to unit. The Brain Trauma Foundation recommends ICP monitoring in traumatic coma patients (GCS ≤ 8) with an abnormal CT scan (Diffuse Injury II-IV or high or mixed density lesions > 25 ml either). Patients admitted to the ICU with traumatic coma and a normal CT scan over 40 years with abnormal motor posturing or significant extracranial trauma associated with systemic hypotension (BP < 90 mmHg) should be considered for ICP monitoring (Fig. 2). The gold standard for assessing ICP is an intraventricular drain inserted into one of

Neuromonitoring for Head Injury Monitoring of intracranial pressure and cerebral blood flow and metabolism -basic and advanced monitoring tools-

Fig. 2 Indications for ICP monitoring and risk of increased ICP.

Fig. 3 ICP monitoring with an intraparenchymal ICP sensor and transducer (Codman®).

701

702 Head Trauma the lateral ventricles and connected to an external pressure transducer. The external auditory meatus (equivalent to the foramen of Monro) is usually used as the reference point. In addition to monitoring pressure, these catheters allow withdrawal of CFS to treat raised ICP. The main limitation of this method is the risk of infection, which increases over time and is in the range of 6-11 percent. Coagulopathy is the contraindication to ICP monitoring due to high risk of intraparenchymal or intraventricular hemorrhage. The catheter may be difficult to place with increased ICP, since the lateral ventricles change shape under increased pressure and are often quite small because of the brain expanding around them from injury and swelling. The best alternative to the ventricle catheter are intraparenchymal probes (Fig. 3). Alternatively, subarachnoid, subdural and epidural devices can be used. However, the accuracy of these devices, especially epidural devices, is lower than that of intraventricular or intraparenchymal catheters. Pressure measured in the lumbar CSF space is not reliable and may be dangerous (brain herniation) in patients with space occupying lesions. Normal ICP depends on age and body posture. Normal ICP in a supine position ranges between 5 and 15 mmHg in an adult. In an infant, 1.5-6 mmHg are considered normal, whereas in children values between 3 and 7 mmHg are considered normal. There is no defined set point at which interventions for intracranial hypertension should be initiated, but levels above 20 mmHg are usually treated. However, there has been no randomized controlled trial showing an outcome benefit for patients with ICP monitoring when compared with patients without ICP monitoring. It is probably more important to maintain an adequate CPP. Reduced CPP and brain herniation have been considered the principle mechanisms of secondary brain damage following severe head injury2. When CPP is used as a target for therapy there is controversy as to which threshold to be used. CPP should be maintained above the expected lower limit of autoregulation, which is above the level at which CBF is expected to fall. The revised guideline of the Brain Trauma Foundation (BTF Guideline, 2003) suggests a lower limit of 60 mmHg. Clinical studies indicate that a CPP of at least 60 mmHg is sufficient to maintain adequate brain tissue oxygen levels and a CPP > 60 mmHg does not provide further benefit in patients with head injury3,4. A controlled study indicated that aggressive management of CPP above 70 mmHg may increase the incidence of acute respiratory distress syndrome (ARDS)1. A previous study suggests that cerebral perfusion is more sensitive to arterial hypotension, especially hemorrhagic hypotension than to intracranial hypertension. In a hypotensive patient, even a small increase in ICP could be harmful. Alternatively, an elevated mean arterial pressure may protect the brain from ischemia against a raised ICP. ICP monitoring should be continued until the patient can be assessed clinically, ICP has stabilized (< 20 mmHg) and cerebral edema has resolved on CT scan. This occurs in the majority of patients within 7 days of the head injury or surgery. Patients with refractory intracranial hypertension may require monitoring for a longer period, although this may increase the risk of infectious complication and loss of wave form. In this situation, ICP monitors may need to be replaced or removed and patients should be assessed by serial CT scan or clinically.

Neuromonitoring for Head Injury Monitoring of intracranial pressure and cerebral blood flow and metabolism -basic and advanced monitoring tools-

703

Cerebral blood flow and metabolism monitoring The human brain consumes a huge amount of energy. The brain (2% of body mass) receives 15-20% of the cardiac output and utilizes 20% of the total (resting) oxygen consumption and 25% of the total glucose consumption. To maintain adequate brain function, the energy is mostly supplied by glucose oxidation (during aerobic respiration 38 molecules of ATP are produced for every molecule of glucose). When the glucose and oxygen supply is decreased due to reduction of the cerebral blood flow (CBF), the brain is functionally impaired and later results in irreversible neuronal damage. Thresholds for ischemia have been described with neurophysiological (functional) failure occurring at 16-20 mL/100g/min and irreversible metabolic failure occurring at 8-12 mL/100g/min. Reduction in CBF does not necessarily result in ischemia because further reduction in cerebral metabolism is common in severe TBI. The diagnosis of cerebral ischemia requires demonstration that the CBF is insufficient for a given metabolic demand. Therefore, it is essential to simultaneously evaluate the cerebral blood flow and metabolism to make important management decisions in practical neurosurgery. Monitoring of CBF and metabolism is divided into continuous (bedside) monitoring techniques and static (imaging) methods. Continuous monitoring techniques include the middle cerebral artery flow velocity measured with transcranial Doppler (TCD), cortical perfusion with laser Doppler flowmetry, oxygen delivery with jugular venous oxygen saturation (SjvO2) catheters, near infrared spectroscopy (NIRS) and brain tissue oxygen sensors, and metabolism with microdialysis. On the other hand, static imaging using single photon emission tomography (SPECT) and positron emission tomography (PET) can obtain values for CBF, oxygen utilization and glucose metabolism with high topographical resolution, although with the disadvantage of limited accessibility and low frequency of observation. Continuous monitoring techniques and static imaging methods are potentially complementary. This section describes the applications and limitation of neuromonitoring approaches to evaluate the CBF, cerebral oxygenation and metabolism in the brain. Bedside monitoring (a) Transcranial Doppler: basic and useful Transcranial Doppler (TCD) ultrasonography is a non-invasive method of assessing the state of the intracranial circulation. TCD provides a means of measuring relative changes in cerebral perfusion by evaluating blood flow velocity (FV) in the basal cerebral arteries through thin regions of the skull, usually the transtemporal route (above the zygomatic arch) (Fig. 4). The linear relationship between CBF and mean FV is only present if the diameter of the insonated vessel and the angle of insonation during the examination do not change. TCD can be used for measuring FVs from several vessels of the Circle of Willis, but most published data refer to the middle cerebral artery (MCA). MCA has a favorable orientation readily accessible to TCD and the insonation depth is between 45-60 mm through the transtemporal route (Fig. 4). Furthermore, the MCA delivers about 70-80% of the ipsilateral carotid artery blood flow, and can therefore be considered to reflect global cerebral flow to the majority of the

704 Head Trauma

Fig. 4 Measurement of the middle cerebral artery (MCA) flow velocity through transtemporal route with a 2 MHz Doppler probe.

ispilateral cerebral hemisphere. There is an inverse correlation between the severity of head injury and the MCA FV. Low FV in the intracranial circulation after TBI is due to low CBF and high ICP levels. However, the raw admission FV data is not a reliable predictor of outcome for individuals except where extremely low FVs were recorded. In practical neurosurgery, TCD is widely used to detect cerebral vasospasm after subarachnoid hemorrhage (SAH) and determine which patients should be further evaluated by conventional angiography. In TBI, cerebral vasospasm after severe head injury has long been recognized and is usually associated with traumatic subarachnoid blood (Fig. 5). The FVs recorded in such cases are usually between 100 and 150 cm/sec, usually lower than those found after aneurysmal SAH, and the time course is shorter, occurring within the first 2-5 days5. CBF can be occasionally impaired below the ischemic threshold resulting in cerebral infarction. TCD is useful in monitoring the temporal course of cerebral vasospasm and thought to be valuable in the day-to-day evaluation of traumatic SAH patients. However, one must take into account that a variety of factors such as technical issues, anatomical issues, intracranial and extracranial physiological issues including ICP, mean arterial pressure, hematocrit, and arterial CO2 content influence the flow velocities. TCD is also useful in testing autoregulation and cerebrovascular reactivity in TBI patients. When autoregulation is intact, FV should remain unchanged with a changing CPP. Lowering arterial blood pressure (ABP) is not acceptable for ethical reasons in TBI patients. Instead, increase in ABP using various vasopressors is a popular and relatively safe way to evaluate the autoregulatory status. Impaired autoregulation is frequently

Neuromonitoring for Head Injury Monitoring of intracranial pressure and cerebral blood flow and metabolism -basic and advanced monitoring tools-

705

Fig. 5 Traumatic subarachnoid hemorrhage and cerebral vasospasm. CT scan showed traumatic subarachnoid hemorrhage and delayed hematoma formation in the left sylvian fissure. The patient exhibited right hemiparesis on day 6. 3D-CT and conventional angiography revealed vasospasm in the middle cerebral artery.

reported in the most severe TBI patients6. Likewise, measurement of cerebrovascular reactivity to CO2 has been widely applied in clinical practice to evaluate cerebral arterial function. A significant correlation between the changes in MCA FV measured by TCD and arterial CO2 levels has encouraged the use of TCD to measure CO2 cerebrovascular reactivity. In normal individuals, a 1 kPa (7.5 mmHg) increase in CO2 causes a 22% change in MCA FV. Impaired or absent CO2 reactivity indicates the ability of the cerebrovascular bed to vasodilate and loss of the cerebrovascular reserve. CO2 reactivity may provide predictive information in patients with TBI. Elevated levels of FV can either indicate a narrowed MCA (vasospasm or stenosis), of high CBF (hyperemia). Since they require a different therapeutic approach, their distinction is critically important. The ratio of intracranial to extracranial velocities (Lindegaard ratio) might be used to differentiate the two states and vasospasm is likely when this ratio exceeds 3. Concomitant jugular venous bulb oximetry (see below) may also provide valuable information in this setting. Decreased jugular vein oxygen saturation (below 55%) is helpful to consider vasospasm, on the other hand values above 85% are suggestive of hyperemia. (b) Laser Doppler flowmetry: basic but uncommon Laser Doppler flowmetry allows real-time measurements of microcirculation (red blood cell flux) with excellent dynamic resolution without quantification of CBF. The laser beam reflects off moving red blood cells and undergoes Doppler shift. The degree of Doppler shift is proportional to the velocity of the cell. This light randomly reflects back

706 Head Trauma

Fig. 6 Principles of measuring of jugular venous oxygen saturation showing normal SjO2 in the presence of normal blood pressure (blood flow), and reduced cerebral SjO2 with a reduction in blood pressure (blood flow).

out of the tissue and onto a photodetector, which then calculates the average velocity of cells within the tissue. The sample volume is quite small (1-2 mm3) and only relative changes can be assessed. Clinical application of LDF is limited as this method is invasive (exposing the brain surface). (c) Jugular venous oxygen saturation: basic and useful Jugular venous oxygen saturation (SjvO2) measures the oxygen saturation of the venous efflux from the brain as an indicator of the amount of oxygen extracted by the brain (Fig. 6). SjvO2 is measured with a catheter that is placed by retrograde cannulation of the internal jugular vein until the tip is at or near the jugular bulb, usually at the first to second cervical vertebrae. A SjvO2 catheter contains two optical fibers. Light is directed into the blood by one of the fibers, reflected back to the second fiber, and transmitted to a photosensor. The photosensor measures the absorption of the reflected light at the various wavelengths with SjvO2 displayed as a percentage of oxygenated hemoglobin to total hemoglobin. By monitoring the SjvO2 in conjunction with arterial blood gases, the arterio-venous difference in oxygen content can be established as a more specific means of assessing the relationship between blood flow and metabolism. Cerebral oxygen consumption (CMRO2) is described by the following equation (CaO2 = arterial oxygen content, CjvO2 = oxygen content of jugular venous blood): CMRO2 = CBF × [CaO2 - CjvO2] The difference in oxygen content between arterial and jugular venous blood is

Neuromonitoring for Head Injury Monitoring of intracranial pressure and cerebral blood flow and metabolism -basic and advanced monitoring tools-

707

expressed by the term of AVDO2. By rearranging the above equation it is expressed that: AVDO2 = CMRO2 / CBF In practice, the AjvDO2 can be calculated from the following equation: AVDO2 = 1.34 × Hb [SaO2 – SjvO2] + 0.003 [PaO2-PjvO2] One gram of hemoglobin can carry 1.34 mL of oxygen and therefore fully saturated hemoglobin contains about 20 mL of oxygen per 100 mL of blood. In contrast, the dissolved oxygen content of this blood is 0.3 mL oxygen per 100 mL of blood. As dissolved oxygen is negligible and can be ignored and hemoglobin is constant, the AVDO2 can be determined by the difference in SaO2 and SjvO2. The normal range of AVDO2 is 4-9 mL O2 per 100 mL of blood (values 9 indicate ischemia). Normal values of SjvO2 range from 60 to 80% and are relatively constant due to the coupling between CBF and CMRO2. Uncoupling following injury is associated with energy perturbations. A decrease in the SjvO2 represents an increase in cerebral oxygen extraction. This may result from systemic hypoxia, low CBF secondary to hypotension or vasospasm or increased ICP with a subsequent decrease in CPP (Fig. 6). Factors that increase cerebral oxygen demand such as seizures or fever may also play a role (Fig. 7).

Fig. 7 Causes of low SjvO2 and high SjvO2. SjvO2 represents a balance between oxygen supply and consumption in the brain and normal SjvO2 is 60-80%.

The interpretation of increased SjvO2 is potentially more difficult. One possibility is that the patient has abnormally high blood flow (hyperemia) to the brain secondary to the loss of autoregulation. A more common situation is where the brain tissue is not viable for oxygen extraction from the blood (massive infarction) or where ICP is so high that blood

708 Head Trauma is largely shunted past the capillary beds leading to arterial blood in the jugular vein. Several studies have investigated the association between SjvO2 and clinical outcome. Both abnormally high and low SjvO2 levels have been associated with poor clinical outcome in TBI patients. In a study of continuous SjvO2 monitoring in TBI patients, one or more episode of jugular desaturation (< 50%) is strongly associated with poor neurological outcome7. SjvO2 monitoring is also useful in monitoring of therapeutic interventions, for example, in setting the safe degree of hyperventilation used following head injury to reduce ICP. It is now common practice to set the degree of hyperventilation whilst maintaining the SjvO2 within the normal range, but further randomized, prospective studies are necessary to determine the optimal use of SjvO2directed therapy to improve outcome. There are several limitations to SjvO2 monitoring in routine clinical use. Firstly, by monitoring global hemispheric oxygen venous saturation, focal areas of ischemia may not be detected, and a relatively large volume of tissue must be affected before the SjvO2 level drops significantly. Furthermore, posttraumatic alterations in CBF are often heterogeneous. Regional CBF may be simultaneously increased in some areas of the brain and decreased in others. Secondly, only one jugular vein is monitored. Although blood in the jugular bulb is derived from both cerebral hemispheres (approximately 70% ipsilateral and 30% contralateral), it is generally accepted that most patients have a dominant side of venous drainage, usually the right. Thirdly, SjvO2 requires frequent recalibration and a high percentage of readings are erroneous because of catheter movement, displacement, or clot formation.

Fig. 8 Principles of near infrared spectroscopy. This tool detects a relative change of regional tissue oxygenation via photon scattering.

Neuromonitoring for Head Injury Monitoring of intracranial pressure and cerebral blood flow and metabolism -basic and advanced monitoring tools-

709

(d) Near infrared spectroscopy (NIRS): basic but unclear role Near infrared spectroscopy (NIRS) is a non-invasive method of measuring regional cerebral oxygen saturation (rSO2) using a scalp oximeter similar to pulse oximetry (Fig. 9). The technique of NIRS is based on the principle of light attenuation by the chromophores* oxyhemoglobin (HbO2), deoxyhemoglobin (Hb) and cytochrome oxidase. Changes in the detected light levels can therefore represent changes in the concentrations of these chromophores. Clinical use of NIRS in the brain has been well established in neonates where transillumination is possible. The accuracy and reliability of NIRS has been questioned because the sample volume cannot be clearly defined and the extracranial tissue layers may contaminate the readings. Sensitivity and quantification are other limitations of NIRS monitoring in the brain. Several companies have devised algorithms that seek to provide an absolute measure of cerebral oxygen saturation, but the accuracy of these methods remains a concern. In spite of several limitations, the technique has demonstrated some potential in multimodal bedside monitoring of TBI patients8. NIRS has future promise as a bedside tool for cerebral blood flow measurements and as a cerebral imaging modality for mapping structure and function. Much further work is needed before we can identify a clear role for this technique in the setting of head injury. *Chromophore: groups of atoms in an organic compound that absorb light at certain wavelengths. A particular chromophore gives the compound its distinctive color by causing it to absorb light selectively. (e) Brain tissue oxygen sensors: advanced Measurements of SjvO2 provide an index of global oxygen metabolism and may miss the focal area of ischemia. The development of sophisticated probes ( 30 ml, even in the absence of clinical signs - EDH’s volume > 25 ml, in posterior fossa or temporal region location - Midline shift > 4 mm, with worsening of neurological status - Increasing in volume of EDH Surgery consists of evacuation of the hematoma through craniotomy. It is important to perform an initial blood replacement to the shocked child; this should be carried out in 20-30 minutes, before starting operatory procedures. For posterior fossa EDH there is no special surgical technique: suboccipital craniectomy, evacuation of the hematoma, hemostasis, dura mater suspension and wound closure. Conservative treatment is attempted in an alert child, without focal neurological deficits, in which CT-scan showed an EDH having a volume < 25 ml, a thickness < 10 mm and midline shift < 4 mm, under attentive clinical observation and repeating of the CT-scan in a neurosurgical center, where surgery can be performed if needed. 12. Posttraumatic subdural hematoma (SDH) in children occurs with an overall frequency of 5%, less common before 3 years old. In infants and toddlers post-traumatic SHD occurs in shaken baby syndrome, and following head injury caused by accidental falling. In children aged between 5 to 6 years acute posttraumatic SDH is generally produced by falls, motor vehicle accidents. In older children common causes are motor vehicle accidents, falls, playing accidents, etc. Subdural hematomas are acute in the first two days, subacute within the next days until 3-4 weeks, and chronic after 4-6 weeks. Chronic posttraumatic SDH in children is considered to be a consequence of conservative treatment or misdiagnose of an acute posttraumatic SDH. According to the location and volume of the hematoma, clinical signs are alteration of LOC, focal neurological signs, and intracranial hypertension, in various grades of intensity. In acute posttraumatic SHD, clinical signs occur immediately and consist of coma, motor deficits and anisocoria, which requires urgent surgery. In infants and toddlers clinical findings associated with acute posttraumatic SDH may include apathia, vomiting, seizures, tense of anterior fontanelle and coma. A child with a subacute posttraumatic SDH may experiences a variable period of LOC, followed by clinical improvement and then clinical worsening, motor deficit, anisocoria and coma; sometimes loss of consciousness can be absent. Deterioration can be rapid in children, with repeated generalized or jacksonian seizures, hemiplegia, decorticated or decerabrate rigidity, anisocoria and coma. Chronic posttraumatic SDH in children is a consequence of a misdiagnosed posttraumatic SDH. Chronic posttraumatic SDH can have other etiology in toddler: perinatal SAH, prolonged, difficult labor, following meningitis, and coagulophaties. Clinical features are unspecific: more common seizures are found, irritability, delayed psychological and motor development. In infants and toddlers tension of the anterior fontanelle and abnormal increase of the head circumference. Motor deficits and cranial nerves palsy may occur, and during the deterioration phase, lethargy and alteration of level of consciousness. Extremely rare the child is asymptomatic.

Traumatic Brain Injury in Children

743

CT-scan is mandatory for diagnostic and therapeutical management. Acute posttraumatic SHD appears on the noncontrast head CT-scan as a crescent-shaped hyperdense area between the inner table of the skull and the surface of the cerebral hemisphere; in subacute posttraumatic SDH and in the chronic phase posttraumatic SDH is iso-, hypodense to brain tissue. Sometimes, the thickness of the SDH is not directly proportionate to the compressive effect on brain parenchyma. Sometimes small posttraumatic SDH can have important mass effect or large subdural collection can have reduced clinical signs. Treatment of posttraumatic SDH depends on the time of diagnostic, clinical findings, location, child’s age, and it can be conservative or surgical. Conservative treatment in acute posttraumatic SDH is indicated only when the child is alert, without focal neurological signs, without any signs of intracranial hypertension and CT-scan showing a subdural collection less than 3 mm thick, without midline shift or midline shift smaller than 3-4 mm. The child must be attentively clinical observed and CT-scan must be repeated. In cases when CT-scan does not show surgical indications, but the general clinical condition is severe, with a GCS score < 9, but without focal neurological or other intracranial hypertension signs, monitoring of the ICP will indicate the optimal therapy. Acute posttraumatic SDH with focal signs or increased ICP requires urgent surgery. Surgical treatment consists of hematoma evacuation, hemostasis, and treatment of associated lesions. Also in subacute and chronic posttraumatic SDH treatment is always surgical. Many neurosurgical techniques were proposed: drainage of hematoma through burr holes, drainage of the fluid into a closed external system, evacuation of the hematoma and excision of the membranes by wide craniotomy.

Fig. 3 Epidural hematoma on left brain hemisphere (mixed lesions: skull fracture, epidural hematoma, pneumoencephalus)

Fig. 4 Posterior fossa epidural hematoma (on left cerebeller hemisphere )

744 Head Trauma

Selective references 1. Balmer B, Boltshauser E, Altermatt S, Gobet R Conservative management of significant epidural haematomas in children. Childs Nerv Syst , 2006, 22, 363-367. 2. Blumenthal I. Shaken baby syndrome Postgrad Med J, 2002, 78, 732-735. 3. Ciurea AV, Kapsalaki EZ, Coman T et al Supratentorial epidural hematoma of traumatic etiology in infants. Childs Nerv Syst ,2007, 23, 335-341. 4. Drapkin AJ. Growing skull fracture: a posttraumatic neosuture Childs Nerv Syst,2006,22, 394-397. 5. Figaji AA, Fieggen AG, Peter JC Early decompresive craniotomy in children with severe traumatic brain injury. Childs Nerv Syst , 2003, 19, 666-673. 6. Kamerling SN, Lutz N et al Mild traumatic brain injury in children: practice guidelines for emergency department and hospitalized patients. Ped Emerg Care ,2003, 19, 431-440. 7. Kan P, Amini A, Hansen K et al. Outcomes after decompressive craniectomy for severe tramatic brain injury in children. J Neurosurg (5 Suppl Pediatrics) ,2006, 105, 337-342. 8. Raimondi AJ: Trauma, in Raimondi AJ (ed): Pediatric neurosurgery. Springler-Verlag, 1998,pp 343-377. 9. Simpson D, Reilly P. Paediatric Coma Scale. Lancet, 1982, 2, 450. 10. Stein SC, Spettell C The head injury severity scale (HISS): a practical classification of closed-head injury. Brain Inj ,1995, 9, 437-444. 11. Suskauer SJ, Huisman TA. Neuroimaging in pediatric traumatic brain injury: current and future predictors of functional outcome. Dev Disabil Res Rev. 2009;15(2):117-23. 12. Villarejo FJ: Cranioencephalic trauma , Atlas of pediatric neurosurgical techniques.Karger, 1985, pp 85-104.

745

New trends in the pathophysiology, diagnosis and treatment of diffuse axonal injury: A proposal of simple guidelines VISOCCHI MASSIMILIANO, MD Institute of Neurosurgry, Catholic University Medical School, Rome, Italy Key words: Diffuse axonal injury, Transcranial Doppler Sonography, Brain Swelling, Cerebral Hyperaemia, Hyperflow Syndrome, Bilateral Decompressive Craniectomy

SUPPORTED BY THE ITALIAN SOCIETY OF NEUROSONOLOGY AND CEREBRAL HAEMODYNAMICS (SINSEC – Italian Chapter of the European Society of Neurosonology and Cerebral Haemodynamics – ESNCH). THE CEREBRAL HAEMODYNAMICS GROUP OF THE ITALIAN SOCIETY OF NEUROSURGERY (SINCH).

DEFINITION Diffuse cerebral lesions are classified as mild and classic concussion and diffuse axonal injury (DAI). The pathologic pattern of DAI was first described by Strich and then by Adams as "diffuse axonal swelling secondary to tearing-torsion of encephalic nervous fibres". DAI is always a neuropathological diagnosis. Although it is true that radiological findings of DAI were described by Gentry et al., these particular radiological signs are only the hallmarks of the most severe forms of DAI. Associated to this basic pattern, haemorrhagic - necrotic lesions of the brainstem, most frequently of dorsolateral quadrants of rostral pons, of corpus callosum and adjacent structures (fornix, gyrus cinguli, septum pellucidum, nucleus caudatus and thalamus dorsalis) were described as well. According to Gennarelli’s CT criteria the patient’s primary DAI damage can be classified as grade 1 : no macroscopic lesions; grade 2 : focal lesions in the corpus callosum and white matter; grade 3 : focal lesions in the dorsolateral quadrants of the rostral brainstem and same lesions of grade two (Fig 1). Thus diffuse microscopic haemorrhagic lesions of the midline and subcortical grey matter deals with the pathological definition of DAI. Moreover neuropathological studies show that DAI of variable severity is present in any patient that is immediately in a coma after impact where

746 Head Trauma A

B

Fig. 1 A) CT scan study. Brain stem contusion consistent with Gennarelli’s grade III DAI. B) Centrum Semiovalis and corpus callosum contusion in Gennarelli’s grade II DAI

A

B

Fig. 2 A) Severe brain swelling at the admission which did not allow cerebrospinal fluid shunt. B) at discharge after hyperflow correction and restoration of normal ventricular size.

Fig. 3 Intracranial hypertension "masks" hyperflow velocitometric pattern. The TCD recording is of a patient who recovered foilowing freat ment. Phase 1: At admission. Phase 2. Hyperflow pattern Phase 3. Hyperflow syndrome complicated by intracranial hypertension (hypoflow pattern) Phase 4. Unmasking effect of decompressive craniectomy (hyperflow pattern)

Diffuse axonal injury: A challenge to gennarelli theory?

747

TAB 1 Diffuse encephalic lesions are common in severe head trauma patients; they may be present in moderate trauma patients and are rare among mild head trauma patients. Intra cranial lesions are classified based on CT scan findings TAB 1 Diffuse encephalic lesions classification based on CT scan findings* • Type I diffuse lesions (12.5%): no pathological findings on CT scan. • Type II diffuse lesions (42%): basal cisterns are present; midline shift < 5 mm and/or hyper dense focal lesions with a volume smaller than 25 cm3 (including bone fragments or foreign bodies). • Type III diffuse lesions (37%): Diffuse brain swelling with cisternal compression, midline shift < 5 mm, with no hyper dense focal lesions > 25 cm3 • Type IV diffuse lesions (7.8%): Hemispheric brain swelling with midline shift > 5 mm, with no focal lesions bigger than 25 cm3. • Type V and type VI lesions of Marshall CT scan classification are those with focal lesions: lesions treated surgically are type V; non surgical lesions bigger than 25 cm3 are classified as type VI. (*Marshall LF, Marshall SB, Klauber MR. (1991)A new clasification of head injury based on computerized tomography. J Neurosurg; 75:S14-S20)

acceleration/deceleration played a role. Delayed or secondary axotomy is a different concept to “secondary axonal injuries” and refers to delayed lesions in patients with functional DAI that evolve to structural DAI. The prognosis is complex and the pathophysiology of this disease is the subject of much concern. In fact all patients become rapidly comatose and the clinical picture is often unfair. Although some Authors in the past over estimated the severity of the disease concluding that half of them die and the remaining ones are in persistent vegetative state or show severe neurological deficits. The exact knowledge of the pathohysiological mechanisms underlying DAI, brain swelling, hyperflow syndromes and intracranial hypertension is mandatory in facing such intriguing disease.

PATHOPHISIOLOGY DAI Diffuse lesions are due to kinetic forces that cause encephalic rotation inside the skull. That leads to distension or rupture of axons or even vascular structures in different encephalic regions. Understanding these mechanisms is essential to the clinic and intensive management of head trauma. Brain and skull have different responses to the same forces applied during a head trauma due to different densities. These differences in movement may lead to cerebral vein rupture and also to impact of brain against rigid

748 Head Trauma skull structures. Peripheral encephalic regions have higher amplitude of movement than central regions because of the stability given by brainstem. This difference stretches out axons and vessels and may lead to temporary dysfunction or even complete rupture. The complex DAI pattern deals with primary and seconday lesions. Primary lesions occur at the time of trauma. High kinetic energy causes cerebral movement and this is the primary factor in diffuse lesions. A direct impact of skull against an external structure is not necessary when acceleration and deceleration forces are involved. Secondary lesions are due to complications after trauma as hypoglycemia, hypoxia (respiratory and/or anemic), high CO2 levels, and hydro electrolytic disturbances which, virtually, can lead encephalic cells to death. In this complex pattern neurotoxic substances, hydrocephaly, intra cranial hemodynamic alterations and other metabolic and infectious systemic disturbances can further complicate the global patient’s trend- Finally there are also cellular death mechanisms, neuronal, endothelial and glial mechanisms, due to biochemical and ionic disturbances related to both primary and secondary lesions.

BRAIN SWELLING and HYPEREMIA In 1973 Bruce stated that , diffuse cerebral swelling after a closed head injury can be due mainly to cerebral hyperaemia and subsequent increase in cerebral blood volume (CBV) and not to brain oedema. Although it is true that the influence of Bruce’s paper about hyperemia in children was very important in the seventies, this concept has been challenged many times since then. Many Authors have shown that intracellular oedema and not an increase in CBV is the main cause of brain swelling. Actually CBV is frequently reduced and not increased in these patients and cerebral metabolic rate with or without cerebrovascular reactivity can be impaired as well. Otherwise the acute cerebrovascular congestion or hyperaemia, when present, is significantly related to intracranial hypertension and unfavourable outcome. Several methods have been introduced to measure this hyperaemic state, such as measuring Hunsfield Units on CT, lateral ventricular or cisterns sizes or studying CBF. The CT appearance of diffuse swelling may develop more readily in children because of the lack of cerebrospinal fluid available for displacement and may have a relatively benign course unless there is a severe primary injury or a secondary hypotensive insult. Transcranial Doppler sonography (TCD) has provided a rapid and non-invasive assessment of cerebral haemodynamics especially blood velocity and pulsatility in the basal cerebral arteries. There is a proportional relationship between blood velocity and regional CBF when C02, cerebral perfusion pressure (CPP) and brain metabolism are stable. The use of mean flow velocity values to discriminate normal from abnormal flow is recommended, since it is less dependent on systemic cardiac factors, compared to other velocities. It therefore serves as a continuous index of cerebral blood flow in the measured vessels. An increase of mean flow velocity in TCD recording is strongly related to the development of diffuse cerebral swelling. Several studies of serial recordings of TCD velocities following head injury have been reported and increased velocities in the basal arteries have been recognised; increased velocity can be due to increased cerebral blood flow (CBF) as well as narrowing of the intracranial arteries. Therefore, a simultaneous index of CBF is needed

Diffuse axonal injury: A challenge to gennarelli theory?

749

to differentiate the two conditions. The Lindegaard index may be used for this purpose. The Middle Cerebral Artery (MCA) mean flow velocity and the Internal Carotid Artery (ICA) mean flow velocity ratio (Lindegaard index) were evaluated in all patients. According to the literature, the Lindegaard index is the most reliable indicator of vasospasm and vasoparalysis. A Lindegaard index below 3 is the most used cutoff point of vasoparalysis; measurements above this ratio are considered as resulting from vasospasm and secondary hypoflow. The cerebral extraction of oxygen (CE02), ie the difference between the saturation of the arterial 02 (SaO2) and the one of the jugular 02 (SjO2), is of outstanding importance in order to identify an hyperflow syndrome. The combination of the Lindegaard Index < 3, the absence of dicrotic waves, the presence of bilateral TCD pattern and the Jugular O2 saturation >75% is consistent with cerebral hyperflow. Hyperaemia, when associated to severe head injury, can be found along with high intracranial pressure (ICP) as a consequence of an increase of intracranial volume; about 40% of brain swelling deteriorate to coma, develop neurological signs or complicate with an increase in ICP more likely in adults than in children. Such finding may lead to secondary haemorrhages especially after ICP decreasing maneuvers. Impairment of cerebral autoregulation has been demonstrated in brain injured patients. In case of hyperflow due to loss of autoregulation, commonly seen in the so called brain swelling, the treatment of choice consists in a decreasing of the vascular bed as well as the blood volume; hyperventilation and barbiturates accomplish the "etiological therapy" of such a syndrome. Otherwise one must be aware that osmotic therapy may increase CBF in vasoparalysis by decreasing blood viscosity .

DAI and ICP In 1982 Gennarelli and his group have shown that similar clinical and structural changes can be produced experimentally in subhuman primates using non-impact controlled angular acceleration of the head "in the absence of any increase in ICP or hypoxaemia. The increase of ICP, mortality and DAI are strongly related to childhood.

DAI and HYPEREMIA TCD assesses conditions of increased or decreased cerebral blood flow velocity parallel or similar to modifications of CBF. A secondary vascular involvement in severe brain injury is claimed as responsible for the appearance of vascular hyperemia and diffuse brain swelling complicated by an increase in ICP in 75% of the cases. The prevalently median localization of the haemorrhagic lesions represents the radiological evidence of a centroencephalic convergence of shock waves. The hypothalamic and brainstem reticular substance is located in the midline and it is the major site of regulation of cerebral circulation. Consequently DAI macroscopic lesions close to these structures could be involved in TCD hyperflow patterns. According to Monro-Kellie doctrine on the constancy of intracranial blood volume, an increase of intracranial blood volume (i.e. vasomotor paralysis) produces an increase in ICP up to the progressive CBF reduction, resulting in the so-called "brain tamponade".

750 Head Trauma

SUGGESTED GUIDELINES ICP monitoring and haemodynamic assessment are of paramount importance in the management of DAI. ICP monitoring and ventricular drainage, when possible, should be adopted in the next future for all the DAI patients, since DAI can be complicated by intracranial hypertension, as demonstrated in all the patients undergone ventriculostomy in our study. In order to avoid fatal mistakes CEO2 evaluation and TCD monitoring provide a reliable assessment of the time course of CBF changes in brain swelling, being able to identify the right time for the etiologic therapy which can be administered by using barbiturates and hyperventilation in hyperflow phases and osmotics up to extreme and heroic decompressive surgery in hypoflow phases of the same syndrome. In conclusion a speculative viewpoint on how the field will evolve in 5 years time deals with the worldwide diffusion of the use of TCD bedside in brain injury patients and particularly in DAI.

REFERENCES 1. Visocchi M, Meglio M, Procaccini E, Cioni B, Carducci P (1995) [Cerebral vasospasm and intracranial hypertension: transcranial Doppler ultrasonographic findings] Rays 20:467-72. 2. Visocchi M, Chiaretti A, Cabezas D, Meglio M (2002) Hypoflow and hyperflow in diffuse axonal injury. Prognostic and therapeutic implications of transcranial Doppler sonography evaluation. J Neurosurg Sci 46:10-7 3. Visocchi M, Chiaretti A, Genovese O, Di Rocco F: Haemodynamic patterns in children with posttraumatic diffuse brain swelling. A preliminary study in 6 cases with neuroradiological features consistent with diffuse axonal injury . Acta Neuroch (2007) 149: 347–356.

Ⅵ. Spine

752

The importance of neurological examination for Spine Disorders GENE BOLLES M.D., LARS WIDDEL M.D. Department of Neurosurgery; University of Colorado in Denver Key words: spine, neurological examination, history taking, spinal syndromes A young male patient is taken to the ED after a motor vehicle accident. Per standardized imaging protocol for trauma patients no cervical spine fractures are noted and the patient is eventually discharged without cervical precautions, despite the patient having mentioned to nursing staff about neck pain. Physician staff did not examine the patient and seemed more concerned about his rib fractures. The next morning the patient is rushed back to the ER with quadraparesia. This time imaging reveals subluxation of C5-6. An older male presents to the spine surgeon for evaluation of lumbar pain. Imaging of the lumbar spine shows a grade 1 spondylolisthesis at L4-5. The patient claims he has had some difficulty walking but this is attributed to the lumbar lesion. A posterior lumbar interbody fusion with pedicle screws is performed. During the surgery the patient is prone with his neck hyperextended. After the surgery the patient wakes up and is unable to move his legs or hands. He is noted to have a spinal cord infarction at C45 from severe cervical spinal stenosis. Situations like these are becoming more frequent nowadays that with the advent of imaging techniques many physicians are basing their decisions and judgments solely on these and not on history taking and physical examination. Although often correct they do have flaws. Therefore imaging results from rapidly improving technology should be considered an adjunctive examination to confirm the impressions from the neurological examination composed of a complete medical history and physical examination. Components of history taking and neurological examination are presented briefly in this chapter. Further information may be obtained by review of reference materials mentioned at the end of this chapter. It is important to have a full understanding of the physio-anatomy of the spine, including its neural aspects, the anatomy and physiology of joints, the muscles and how the spine relates to the musculoskeletal system. It will be the basis for informed interpretation of information obtained in any spine examination.

History taking: A good history will often suggest a correct diagnosis and the examination can then be tailored to search for corroborating physical signs. Patients with spinal disease may have co-morbidities that make it difficult to elicit accurate information. In that case, the examiner may need to question the patient closely, or obtain information from family or friends. Time spent obtaining an accurate history may bring a rapid and correct

The importance of neurological examination for Spine Disorders

753

diagnosis thereby saving time and reducing unnecessary examination and diagnostic procedures. The history should be recorded in chronological order and in a systematic manner, noting the date of onset of symptoms and developing the story in sequence. Symptoms should be characterized and described in terms of severity, location, temporal profile, as well as aggravating and ameliorating factors. It is important to have the patient describe symptoms in his or her own words, and for this to be reflected in the record. Do not interpret the complaints and record them in a fashion that biases the history to suggest a diagnosis that is suspected and not borne out by the patient’s story. Detailed questioning might be necessary to rule out symptoms such as loss of strength, bowel or bladder dysfunction, or ambulation difficulties. Information should be taken concerning possible symptoms related to areas of the spine not in question by the patient. Patients with complaints of lower back pain may also have significant cervical disease and symptoms. Obtaining an adequate past medical history, family history, social history and evaluation of risk factors may provide additional information for the diagnosis or the etiology or cause of the patient’s condition. It can assist in determination of therapy options and may reveal potential contra-indications for certain treatments.

The neurological examination: The neurological examination should always be included as part of the general physical examination. Begin with evaluation of vital signs and the patient’s body mass index. The psychological state should be noted. Patients may present as depressed, hostile, apprehensive, preoccupied and even uncooperative. Recognizing moods will help the examiner to choose the best approach to maximize the information obtained from the encounter. The information could also aid in choosing treatment options based on the specific patient’s needs and ability to participate. A thorough cardiovascular, respiratory, abdominal and peripheral vascular evaluation should also be performed. From the first moment of contact, the physician should observe the patient speaking and interacting socially, and while sitting and walking. The patient may have difficulty with certain movements due to pain or physical limitation. Facial expressions may demonstrate activity which elicits pain. The trained examiner can often discern abnormalities during this part of the encounter which will aid in diagnosis. Following the initial general physical examination, there should be close visual inspection of the spine. The examination should include evaluation for signs of trauma, blisters, scars, discoloration, redness, contusions, lumps, bumps, hairy patches, café au lait spots, fat pads and other marks. The spinal curvature, both sagital and coronal aspects, should be evaluated in supine position and if possible, in a flexed and sitting position. Any variance from normal should be noted. Evaluation should include shoulder height and the plumb line which extends from the C7 spinous process perpendicular to the floor. The line should pass normally through the inter-gluteal fold. Any variances should be recorded. Palpation of the spine should be performed including the spinous processes, facet joints, the anterior cervical spine, the para spinal musculature, the gluteal folds, the pelvis

754 Spine and associated musculoskeletal joints. Anything that elicits pain or is grossly abnormal should be recorded. In patients complaining of significant posterior cervical pain, the greater occipital nerves should also be palpated. The degree of motion of the spine should be assessed by having the patient perform tasks that fled and extend in anterior, posterior and lateral directions. The patient should attempt rotation of the spine. Any decrease in the expected range of motion or any motion that results in pain should be noted. Any new spinal deformity or any change in a spinal deformity should also be noted. Passive motion should be attempted only if full active range of motion is hindered and so long as the patient does not experience significant pain. Distraction tests and spinal axial weight bearing test can be performed to determine increasing or relief of symptoms. An example is the Spurling’s test for evaluation of cervical radicular symptoms. Active and passive motion of other axial joints such as the gleno-humeral or the pelvic femoral should be performed as disease in these joints can mimic spinal disease.

Motor examination: Following joint assessment, there should be evaluation of tone and strength of distal musculature. Evaluation of tone can provide ample information regarding chronicity of the condition, and whether there is a functional component to the symptoms. Strength should be assessed in all muscle groups and described according to its international grading scale: • Grade 0: (no function): total paralysis • Grade 1 (trace): palpable or visual contraction without joint motion • Grade 2 (poor) complete range of motion of joint with gravity eliminated • Grade 3 (fair): complete range of motion of joint against gravity • Grade 4 (good) complete range of motion of joint against gravity and some resistance • Grade 5 (normal) complete range of motion of joint against gravity and resistance (unbreakable) The following is a table with a more detailed look at the nerve roots and muscles involved with each motion, Motion being evaluated Shoulder abduction

Nerve roots C5

Shoulder flexion

C5, C6

Shoulder adduction

C7

• • • • • • • • • • •

Muscles involved Deltoid Supraspinatus Serratus anterior Deltoid Coracobrachialis Pectoralis major Biceps Pectoralis major Latismus dorsi Teres major Deltoid

The importance of neurological examination for Spine Disorders

External rotation of the shoulder

C5, C6

Internal rotation of the shoulder

C5, C6

Elbow flexion

C5, C6

Elbow extension

C7

Wrist flexion

C7, C8

Wrist extension

C6

Finger flexion

C8

Adduction of thumb Little finger adduction Finger abduction

C8 C8, T1 C8, T1

Hip flexion Hip extension Knee extension Hip adduction Hip abduction Dorsiflexion Great toe extension Plantar flexion

L1, L2, L3 S1 L2, L3, L4 L2, L3, L4 L5 L4, L5 L4, L5 S1

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • •

755

Infraspinatus Teres minor Deltoid Subscapular Pectoralis major Latismus dorsi Teres major Deltoid Brachialis Bicpes Brachioradialis Supinator Triceps Aconeus Flexor Carpi radialis Flexor carpi ulnaris Extensor carpi radialis longus Extensor carpi radialis brevis Extensor carpi ulnaris Flexor digitorum profundus Flexor digitorum superficialis Adductor pollicis Palmar interossei Dorsal interossei Abductor digiti minimi Iliopsoas Gluteus maximus Quadriceps Adductor brevis, magnus, longus Gluteus medius Tibialis anterior Extensor hallucis longus Peroneus longus and brevis Gastronemius Soleus

Sensory testing: Sensory evaluation should include crude touch, pinprick, temperature, proprioception and vibration in the cervical, thoracic, lumbar and sacral innervations. Changes should be noted. The dermatome maps are fairly accurate although at more medial locations, significant overlap may exist.

756 Spine

Fig. 1 Dermatomes.

Reflexes: Reflexes should be evaluated and assessed according to the following Reflex Grading Classification System: • Grade 0: no reflex • Grade 1: slight response • Grade 2: normal reflex • Grade 3: hyperactive • Grade 4: hyperactive with clonus The following reflexes should be assessed: Reflex Biceps Reflex Brachioradialis Reflex Triceps Reflex Abdominal Reflexes Cremaster Reflex Patellar tendon reflex Posterior Tibial Reflex Calcaneal Tendon Reflex Babinski’s Sign Bulbocavernous Reflex Anocutaneous Reflex

Nerve roots C5 C6 C7 T7-L1 T12, L1 L4 L5 S1 S2, S3 S2, S3, S4 S3, S4, S5

The importance of neurological examination for Spine Disorders

757

Ambulation: Always evaluate ambulation unless contra-indicated or otherwise impossible. This will provide both motor and sensory information. Often sensory disturbances are expressed in a wide based gait, while motor dysfunction can be expressed in spasticity or foot drop.

Special maneuvers: Multiple special maneuvers allow further introspection into specific disease patterns: :Cranial nerve examination

Evaluation of all cranial Nerves

Spurling’s maneuver

Application of axial load to cervical spine during rotation of neck Neck flexion to evaluate for shock like feelings or weakness Series of passive head motions to elicit a variety of symptoms Evaluation of radial pulse during several arm movements Flicking of the middle finger eliciting thumb flexion Contralateral reflexive response to reflexes

Lhermitte’s test

Modified Dekleyn and Nieuwenhuyse Test Adson’s Test

Hoffman’s Test

Crossed Radial Reflexes Static / Dynamic Romberg Test Straight leg raise or Lsaegue’s sign Bragard’s Test

Neri’s Test

Hip flexion with extended knee resulting in pain from radicular irritation Similar as straight leg raise but added foot dorsiflexion Similar as straight leg raise but added neck flexion

Cranial Nerve palsies may be present with occipitocervical or high cervical lesions. Allows evaluation for foraminal compression Consistent with high cervical myelopathy For evaluation of vertebro-basilar artery compression To evaluate for Thoracic outlet syndrome. Suggestive of high cervical or cerebral disease Suggestive of high cervical or cerebral disease To evaluate for vestibulocerebellar disease or myelopathy Lumbar radiculopathy or dural irritation Lumbar radiculopathy or dural irritation Lumbar radiculopathy or dural irritation

The physical examination of a spinal patient should be adjusted according to the patient’s condition. For example, mobilization of the spine in the case of a patient with spinal trauma might exacerbate an underlying fracture. Any movement testing

758 Spine should be delayed until a fracture can be ruled out.

Common Spinal Syndromes: The following are short descriptions of common spinal syndromes: 1. Central Cord Syndrome • pain and temperature loss affecting upper extremities greater than lower • sparing of light touch and proprioception • lower motor neuron weakness of the affected cord levels (anterior horn cell involvement) 2. Hemisection (Brown-Sequard Syndrome) • ipsilateral plegia below the lesion • ipsilateral proprioception and light touch loss below the lesion • contralateral pain and temperature loss below the lesion 3. Myelopathy • Spastic wide based gait • Hyper-reflexia with or without clonus • Positive Hoffman’s or Babinski 4. Lumbar stenosis • Pseudo-claudication syndrome – pain after prolonged standing or walking relieved by sitting. • Myelopathy signs 5. C5, C6 Radiculopathy (Figures 2,3) • Weakness of the deltoid, infraspinatus, biceps and brachioradialis. • Diminished biceps and brachioradialis reflexes. • Sensory symptoms or loss in deltoid area or thumb. 6. C7 Radiculopathy (Figure 4) • Weakness of the triceps, pronator teres, wrist and finger extensor muscles. • Diminished triceps reflex. • Sensory symptoms or loss in the middle finger. 7. C8 Radiculopathy (Figure 5) • Weakness of the wrist flexors and intrinsic hand muscles (median and ulnar). • Diminished triceps and finger flexor reflex. • Sensory symptoms or loss in the hand (fifth finger). 8. L3, L4 Radiculopathy (Figure 6) • Weakness of the iliopsoas, quadriceps and adductor muscles. • Sensory symptoms or loss on the anterior thigh. • Diminished or absent knee reflex. 9. L5 Radiculopathy (Figure 7) • Weakness of the anterior tibial, peronei, posterior tibial, and toe extensor muscles. • Sensory symptoms or loss on dorsum of foot and great toe. • Diminished or absent internal hamstring reflex. • Pain on straight leg raising

The importance of neurological examination for Spine Disorders

759

10. S1 Radiculopathy (Figure 8) • Weakness of the gastrocnemius (can’t walk on toes on affected side) and toe flexor muscles. • Sensory symptoms or loss on sole of foot. • Diminished or absent Achilles (ankle) reflex. • Pain on straight leg raising. 11. Cauda equine syndrome • Acute onset of urinary retention or overflow incontinence • Fecal incontinence or loss of anal sphincter tone • Saddle anesthesia • Global or progressive weakness in lower extremities For patients with traumatic spinal disease several classifications have been described, including Frankel’s; Bradford and McBride and the American Spinal Injury Association Impairment Scale (ASIA). Overall the different scales are very similar; however, the ASIA scale seems to be the one that has had greater acceptance and the greatest inter-examiner reliability: • A (complete): No motor or sensory function is preserved in the sacral segments S4- S5. • B (incomplete): Sensory but not motor function is preserved below the neurologic level of injury and extends through the sacral segments S4-S5. • C (incomplete): Motor function is preserved below the neurologic level of injury, and the majority of the key muscles below that level have a muscle grade less than 3 (non-useful function). • D (incomplete): Motor function is preserved below the neurologic level of injury, and the majority of key muscles below the neurologic level have a muscle grade greater than or equal to 3. • E (normal): Motor and sensory function is normal.

Fig. 2 C5 Radiculopathy

Fig. 3 C6 Radiculopathy

760 Spine

Fig. 4 C7 Radiculopathy

Fig. 5 C8 Radiculopathy

Fig. 6 L4 Radiculopathy

Fig. 7 L5 Radiculopathy

Fig. 8 S1 Radiculopathy

The importance of neurological examination for Spine Disorders

761

Importance of a physical exam: Use of available imaging technologies prior to the spine specialist examining the patient may result in a directed diagnosis and treatment recommendations. Although often correct they may be flawed. In our first example in the introduction the indication by the patient o neck pain and a more detailed exam would have likely revealed the underlying on imaging non-apparent lesion. Meanwhile in the second case a detailed physical exam might have hinted towards a myelopathy affecting all 4 extremities that would have led to further evaluation and prevention of the injury from hyper-extension of the neck during lumbar surgery. Neck and lumbar symptoms can be a reflection of adjoining joint disease and not necessarily from the spine. Failure to identify shoulder, hip, sacroiliac or knee disease could have the patient receiving treatment for spinal disease without improvement in symptoms. Therefore it is important for the health care provider to recognize imaging technologies of the spine as a part of the medical method that is adjunctive and complimentary to the more important physical examination. It is the correlation of these which will provide the correct diagnosis and subsequent treatment.

REFERENCES 1. Lynne P. Taylor, MD, Sandi E. Lemming, MD. Family Practice Curriculum in Neurology, American Academy of Neurology, 2001; Chapter 9 - Neck and Back Pain. http://www.aan.com/familypractice/html/chp9.htm (last accessed on June 15th, 2009) 2. Todd J. Albert, Alexander R. Vaccaro. Physical examination of the spine. Thieme, 2005 3. Mark S. Greenberg, Nicolas Arredondo. Handbook of neurosurgery. Thieme, 2006 4. A Goic, G Chamorro, H Reyes. Semiología Médica. Editorial Mediterráneo. 1999

762

Treatment for craniovertebral instability ATUL GOEL M.Ch.1; ABHIDHA SHAH, M.Ch.2 1

Prof. and Head of Department, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai-400012, India 2 Chief Resident, Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai-400012, India Key words: craniovertebral instability, treatment, atlantoaxial dislocation, lateral mass, plate and screw technique, occipitocervical fixation, double insurance fixation, trans-spinous process, trans-spinolaminar, and translaminar

The surgical management of craniovertebral junction instability is complex due to the relative difficulty in accessing the region, critical relationships of neurovascular structures and the intricate biomechanical issues involved. Whilst a successful outcome is gratifying, the complications of surgery, however, are potentially lethal. Atlantoaxial dislocation: The techniques of craniovertebral fixation evolved during the 20th century as the anatomy and biomechanics of the craniovertebral region became clearer. Atlantoaxial dislocation has been treated by various methods of fixation employing autologous bone graft, sublaminar wires, metal loupes and rectangles. Transarticular (27) and inter-articular techniques (5, 9) employing the use of screw implantation in the firm and strong lateral masses of atlas and axis, have been successfully employed for over 20 years. Although midline fixation techniques are still widely used, the technique of Magerl (27), which combines interspinous wiring with transarticular screw fixation, has continued to be a popular technique of fixation. In 1988, we suggested an alternative plate and screw technique of fixation of the lateral masses of the atlas and axis vertebrae and later discussed our 14-year experience with 160 cases with mobile and reducible atlantoaxial dislocation managed by this technique. (5, 9) Lateral mass plate and screw technique (5, 9): Relevant Surgical anatomy The vertebral artery adopts a serpentine course in relationship to the craniovertebral region. The vertebral artery during its entire course is covered with a large plexus of veins. The venous plexuses are the largest in the region lateral to the C1-2 joint. After a relatively linear ascent of the vertebral artery in the foramen transversarium of C6 to C3, the artery makes a loop medially towards an anteriorly placed superior articular facet of the C2 vertebra, making a deep groove on its inferior surface. The extent of medial extension of the loop varies. The distance of the artery from the midline of the vertebral body of C2 as would be observed during a transoral surgical procedure is on an average 12 mm. (1, 29) The vertebral artery loops away from the midline underneath the superior articular facet of the C2.

Treatment for craniovertebral instability

763

The course of the vertebral artery in relationship to the inferior aspect of the superior articular facet of the C2 makes its susceptible to injury during transarticular and interarticular screw implantation techniques. Operative technique (Figures – 1, 2): (5, 9) Cervical traction is set up prior to induction of anesthesia and the weights are progressively increased to approximately 5-8 kilograms or one-sixth of the total body weight. The patient is placed prone with the head end of the table elevated to about 35 degrees. Cervical traction stabilizes the head in an optimally reduced extension position and prevents any rotation. The traction also ensures that the weight of the head is directed superiorly towards the direction of the traction and the pressure over the face or eyeball by the headrest is avoided. Elevation of the head end of the table, which acts as a counter traction, helps in reducing venous engorgement in the operative field. The suboccipital region and the upper cervical spine are exposed through an approximately 8-cm longitudinal midline skin incision centered on the spinous process of the axis. The spinous process of the axis is identified, and the attachment of paraspinal muscles to it is sharply sectioned. The large second cervical ganglion is closely related to the vertebral artery on its lateral aspect. It is first exposed widely and then sectioned sharply. This procedure provides a wide exposure of the lateral masses of the atlas and

Fig. 1a Line drawing shows lateral mass plate and screw fixation technique.

Fig. 1b Line drawing showing occipitocervical fixation. The occipital end of the plate is fixed with screws. The cervical end of the plate is fixed with a screw either in C2 alone or in C1 and C2 lateral mass.

764 Spine

Fig. 2a Lateral plain X-ray with the neck in flexion showing marked atlantoaxial dislocation.

Fig. 2b Lateral X-ray with the head in extension showing complete reduction of the dislocation.

Fig. 2c CT scan showing the reduction of the dislocation. Os-odontoideum can be observed.

Treatment for craniovertebral instability

765

Fig. 2d Postoperative CT scan showing lateral mass plate and screw fixation.

Fig. 2e Coronal view showing the screws in the lateral mass of the atlas and axis.

axis. Bleeding from the large venous sinuses in the region and in the extradural space can be troublesome. Packing of the region with Surgicel and gelfoam can assist in the control of venous bleeding. The joint capsule is cut sharply, and the articular surfaces of the joint are exposed. The adjacent synovial articular surfaces of the atlantoaxial joint are decorticated widely with a microdrill, and pieces of bone harvested from the iliac crest are stuffed into the joint space. The lateral aspect of the lamina and a part of the pars of the axis are drilled to make the posterior surface of the lateral mass of the axis relatively flat so that the metal plate can be placed snugly and parallel to the bone. Drilling also helps in reducing the length of the plate and in placing the screw more superiorly and almost directly into the lateral mass of the axis. Actual vertebral artery exposure is

766 Spine

Fig. 2f Sagittal view CT scan showing reduction and fixation of the dislocation.

unnecessary either lateral to the pars of the axis or superior to the arch of the atlas. Screws are implanted into the previously created guide holes in the lateral mass of the atlas and axis through a two holed (approximately 2 cm in length) metal (stainless steel or titanium) plate. First, a screw is placed into the atlas. It is directed at an angle of approximately 15 degrees medial to the sagittal plane and 15 degrees superior to the axial plane. The preferred site of screw insertion is at the centre of the posterior surface of the facet, 1 to 2 mm above the articular surface. Whenever necessary, careful drilling of the inferior surface of the lateral aspect of the posterior arch of the atlas in relation to its lateral mass can provide additional space for the placement of the plate and screw implantation. The screw may even be implanted by choosing an insertion point on the posterior surface of the posterior arch of the atlas, just superior to the facet or even through the articular surface of the lateral mass of the atlas. Such sites are useful more frequently in children than in adult patients. Screw implantation in the axis is relatively unsafe, because of the intimacy of vertebral artery relationships. The preferred site of screw implantation in the lateral mass of the axis is in the medial and superior third. The direction of screw implantation must be sharply medial and superior and should be toward the superior aspect of the body of the axis vertebra towards the midline. The medial surface of the pars of the axis is identified before the implantation of the screw. The screw is directed at an angle approximately 25 degrees medial to the sagittal plane and 15 degrees superior to the axial plane. The angle of screw insertion varies, depending on the local anatomy and the size of the bones. The quality of cancellous bone in the lateral masses of the atlas and axis in the proposed trajectory of screw implantation is generally good, providing an excellent purchase of the screw, and avoids the vertebral artery. The screws used are 2.9 mm in diameter in the adult patients and 2.7 mm in diameter in the pediatric patients. The length of the required screw is calculated on the basis of the

Treatment for craniovertebral instability

767

size of the lateral masses observed on the preoperative radiological studies. The approximate lengths of the atlas screws are 24 mm in adults and 20 mm in children. The screws in the atlas and axis were almost similar in their length. The lateral masses of the atlas and axis are firm and cortical in nature, and, although preferable, it is not mandatory that the screws engage both the posterior and anterior cortices. Intraoperative fluoroscopic control and neuronavigation was found to be helpful but not essential in determining the state of the screws. Large pieces of cortico-cancellous bone graft from the iliac bone are then placed over the adequately prepared posterior elements of atlas and axis. After the wound is closed, cervical traction is discontinued. The patients are mobilized as soon as possible and advised to wear hard cervical collar for 3 months. Vertebral artery management: The most dreaded complication of the procedure is injury to the vertebral artery. Appropriate anatomical information of the region in general and in the case in question is the only way one can possibly avoid this eventuality. The vertebral artery can be injured during the process of lateral dissection of the C2 ganglion. The other potential site of injury is during the insertion of the screw in the axis. In the later situation, to control the bleeding, one has to pack the bleeding bone hole with bone wax. One can then insert the screw through the same hole, prepare for an alternative site of screw insertion or use an alternative method of atlantoaxial fixation. Respect and care of all neural and vascular tissues and employment of precise technique are critical to success. (26) This technique of lateral mass fixation and opening of the joint provides an opportunity of manipulating atlas and axis independently by obtaining fixation points in their strongest elements and hence has very versatile applications. Occipitocervical fixation: In the year 1988, (5) we described the use of lateral mass of the axis and of atlas for screw implantation for stabilization of the cervical end of the occipitocervical plate. The occipital end of the plate could be fixed with the help of occipital screws or wires. We were amongst the initial authors to describe screw fixation of the occipital end of the occipitocervical implant. Double insurance fixation: This method of atlantoaxial fixation combines transarticular method of fixation and the interarticular fixation technique. (23) The technique combines the biomechanical strengths of both the more commonly used techniques of fixation and provides maximal stability to the implants (Figures 3, 4). Trans-spinous process, trans-spinolaminar and trans-laminar C2 screws: In the year 2004, we discussed the feasibility of direct implantation of screws into the spinous process of the axis for fixation of the cervical end of the plate.(4) The relatively strong and stubby spinous process of the axis, particularly in cases with occipitalization of the atlas facilitated screw implantation. The screw implantation in the spinous process, spinolaminar junction and lamina provides a firm and stable option for

768 Spine

Fig. 3 Line drawing showing ‘double insurance’ plate and screw fixation. The atlas screw is implanted into the lateral mass of the atlas, whilst the C2 screw is trans-articular.

Fig. 4a CT scan showing atlantoaxial dislocation.

Fig. 4b Postoperative CT scan showing reduction of the dislocation and fixation with plate and screws.

Fig. 4c Sagittal scan through the lateral masses, showing the double insurance fixation.

Treatment for craniovertebral instability

769

stabilization of the cervical end of the occipitocervical fixation. Joint jamming technique: The technique of ‘atlantoaxial joint-jamming’ (22) can be a useful method of atlantoaxial fixation. (Figures 5, 6) Spiked Titanium metal spacers were used for the purpose. In the technique the joint was opened and distracted and spiked spacers were impacted into it. Bone graft was additionally placed in the joint cavity. No plate and screws or wires were used in the fixation process. The indication for surgery was subtle atlantoaxial instability that is observed following trauma. Marked or long-standing instability that is seen in cases with congenital atlantoaxial dislocation may not be suitable for joint jamming. However, currently use of joint spacers can be recommended only as an additional stabilizing method that can be used in combination with other fixation techniques. However, direct stabilization of the site of movement of the atlantoaxial joint provides an opportunity for firm and lasting control of abnormal movements in the region.

Fig. 5 Picture showing the inter-articular spacers.

Fig. 6a Lateral X-ray with the head in flexion, showing atlantoaxial dislocation.

770 Spine

Fig. 6b Postoperative X-ray showing reduction of the dislocation. Spacers within the joint can be seen.

Fig. 6c Sagittal CT scan showing the spacer within the atlantoaxial joint.

Fig. 6d Coronal scan showing the spacers within the joint.

Treatment for craniovertebral instability

771

Fixed or irreducible atlantoaxial dislocation: Atlantoaxial dislocation is described as 'fixed' or 'irreducible' when there is no radiographic reduction of the dislocation on full neck extension or after institution of cervical traction. Fixed atlantoaxial dislocation can be congenital in nature or can be secondary to trauma to the region. Congenital os odontoideum and fracture at the base of the odontoid process are frequent accompaniments of fixed atlantoaxial dislocation. Various authors have suggested a transoral decompression followed by a posterior fixation as the safest method of treatment of this complex anomaly. Treatment by posterior decompressive procedures has been reported to be associated with high complication rate. Some authors have reported success with a transoral decompression of the region, without any posterior fixation. Direct facet joint distraction can result in reduction of the fixed dislocation in a significant number of cases. With our experience, it seems that there may be a place for reduction of the 'fixed' atlantoaxial dislocation and a subsequent fixation, without the removal of any bony spinal element. (12) Such a treatment can be adopted even is cases with ‘spondyloptosis’ of atlas over axis (14). As there is no vertebral body of the atlas, spondyloptosis can be labeled as a clinical condition when the facet of atlas was dislocated anterior to the facet of axis. Basilar invagination: Classification into Group A and B Basilar invagination can be divided into two groups. (25) In Group A basilar invagination there was clinical and radiological evidence of instability of the craniovertebral junction. The instability of the region is manifested by distancing of the odontoid process away from the anterior arch of the atlas. The tip of the odontoid process ‘invaginated’ into the foramen magnum and was above the Chamberlain line, (2) McRae line of foramen magnum (33) and Wackenheim’s clival line (30, 35). The definition of basilar invagination of prolapse of the cervical spine into the base of the skull, as suggested by von Torklus, (36) was suitable for this group of patients (Figure 7). Group B basilar invagination was where the odontoid process and clivus remained anatomically aligned despite the presence of basilar invagination and other associated anomalies. In

Fig. 7a Sagittal CT scan showing Group A basilar invagination.

772 Spine

Fig. 7b MRI showing Group A basilar invagination.

Fig. 8a CT scan showing Group B basilar invagination.

Fig. 8b MRI showing Group B basilar invagination.

Treatment for craniovertebral instability

773

Fig. 9 Sagittal image showing the spondylolisthesis of C1 facet over C2 facet as a cause of basilar invagination.

this group, the tip of the odontoid process was above the Chamberlain’s line but below the McRae’s and the Wackenheim’s lines (Figure 8). The radiological findings suggested that the odontoid process in Group A patients resulted in direct compression of the brainstem. In this group, the atlantoaxial joints were ‘active’ and their orientation was oblique as shown in the figure (Figure 9), instead of the normally found horizontal orientation. We have found similarities of such a position of the C1-2 facets with spondylolisthesis seen in the subaxial spine. (32) It appears that the atlantoaxial joint in such cases is in an abnormal position as a result of mechanical instability and progressive worsening of the dislocation is probably secondary to increasing ‘slippage’ of the facets of atlas over the facets of axis. (21, 32) In Group B, the atlantoaxial joints were normally aligned. In some cases the joints were entirely fused. The pathogenesis of basilar invagination appears to be different in the two groups. Whilst it appears that Group A basilar invagination may be related to mechanical instability, Group B basilar invagination appears to be secondary to a congenital abnormality. Group A basilar invagination forms a larger subgroup of patients that are encountered in Indian sub-continent. A number of bone and soft tissue anomalies are associated with basilar invagination. These include short neck, torticollis, platybasia, cervical vertebral body fusion (Klippel - Feil abnormality) (13,28) including assimilation of atlas, spondylotic spinal changes and restriction of neck movements. A number of these abnormalities were seen to be reversible following decompression and stabilization of the region (18). Considering that several physical features associated with this group of basilar invagination are reversible, it appears that the pathogenesis in such cases may be more due to mechanical factors rather than congenital causes or embryological dysgenesis. The common teaching on the subject is that the short neck and torticollis are a result of embryological dysgenesis and effectively result in indentation of the odontoid process into the cervicomedullary cord. However, it appears that it is the cord compression due to indentation by the odontoid process that is the primary event and all the physical alterations and bony abnormalities, including the short neck and torticollis are secondary natural protective

774 Spine responses that aim to reduce the stretch of the cord over the indenting odontoid process. Pain, restriction of neck movements and hyperlordosis of the neck indicate the presence of instability of the craniovertebral junction. Craniovertebral Realignment for Group A Basilar Invagination (Figures 10, 11) The standard and most accepted form of treatment of Group A basilar invagination

Fig. 10a Preoperative MRI scan of a 10-year-old boy showing marked Group A basilar invagination.

Fig. 10b CT scan showing the invagination.

Fig. 10c Postoperative CT scan showing reduction of the basilar invagination surgically treated by the technique of atlantoaxial joint distraction, reduction and fixation.

Treatment for craniovertebral instability

775

Fig. 11a Preoperative CT scan showing Group A basilar invagination.

Fig. 11b Postoperative scan showing reduction of the basilar invagination, without any bone or dural decompression.

is a transoral decompression (6, 7, 25). Majority of authors recommend a posterior occipitocervical fixation following the anterior decompression. Trans-oral odontoidectomy and resection of superior half or third of the C2 body was a gratifying surgical procedure in Group A patients (7,11). However, the long-term clinical outcome following the twin operation of transoral decompression followed by posterior stabilization was seen to be inferior to the clinical outcome following our current operation that involves craniovertebral realignment without any bone, dural or neural decompression. We had earlier attempted to reduce basilar invagination by performing occipitocervical fixation following institution of cervical traction (6, 7). However, all the four cases treated in this manner subsequently needed transoral decompression as the reduction of the basilar invagination and of atlantoaxial dislocation could not be sustained by the

776 Spine implant. The technique of craniovertebral realignment by wide removal of atlantoaxial joint capsule and articular cartilage by drilling and subsequent distraction of the joint by manual manipulation provided a unique opportunity to obtain reduction of the basilar invagination and of atlantoaxial dislocation. Technique of atlantoaxial joint distraction: (12, 19, 25) The facets of the joint on both sides are distracted using a combination of varying sizes of osteotomes and customised distractors. The osteotomes are introduced with the flat end and then turned inside the joint to affect distraction. Bone graft harvested from the iliac crest is packed in titanium metal spacers and used as a strut in the prepared atlantoaxial facet joints. The size of the spacers used depends on the space available within the distracted joint space as well as the amount of distraction required to reduce the basilar invagination. The average sized spacers measured 10 mm in length, 8 mm in breadth and 3 mm in height. Metal spacer has a single large or multiple small holes to assist in bone fusion and is tapered at one end to assist placement in the joint. Bone graft was stuffed in the distracted joint space in multiple pieces on all the sides of the spacer. With our experience in handling the atlantoaxial joints in this group of patients, we have realized that the joint is not 'fixed' or 'fused' but is mobile and in some cases is hypermobile, and is probably the prime cause for the basilar invagination. The history of trauma preceding the clinical events, predominant complaint of pain in the neck and the improvement in neurological symptoms following institution of cervical traction suggests 'vertical' instability of the craniovertebral region. (16) The fixation was seen to be strong enough to sustain the vertical, transverse and rotatory strains of the most mobile region of the spine. Following surgery, the alignment of the odontoid process and the clivus and the entire craniovertebral junction improved towards normalcy. The tip of the odontoid process receded in relationship to the Wackenheim's clival line, Chamberlain's line and McRae' line suggesting reduction in the basilar invagination. The posterior tilt of the odontoid process, as evaluated by modified omega angle, was reduced after the surgery. We could obtain varying degrees of reduction of the basilar invagination and atlantoaxial dislocation. The extent of distraction of the joint and the subsequent reduction in the basilar invagination was more significant in younger than in older patients. (19) Foramen magnum decompression for Group B patients In Group B, on the other hand, the assembly of odontoid process, anterior arch of the atlas and the clivus migrated superiorly in unison resulting in reduction of the posterior cranial fossa volume, which was the primary pathology in these cases. (25) The Chiari malformation or herniation of the cerebellar tonsil was considered to be a result of reduction in the posterior cranial fossa volume. In the year 1997, we first defined the clinical implication of association of small posterior cranial fossa volume and Chiari malformation (7).

Treatment for craniovertebral instability

777

It appears that patient’s in Group B benefited by foramen magnum bony decompression. The procedure resulted in amelioration of symptoms and at least an arrest in the progression of the disability. The suboccipital bone and posterior rim of the foramen magnum and the dura overlying the herniated cerebellar tissue were thin in a significant number of cases (3). This probably was related to the chronic pressure changes secondary to the reduced posterior cranial fossa volume. Various authors have recommended that to achieve maximal decompression, it is necessary to open the dura mater and to cut all constrictive dural and arachnoidal bands. Some authors have recommended leaving the dura open while others have recommended the placement of a graft. Current papers do not recommend resection of the herniating tonsils or even sectioning of adhesions around it. (37) The fact that dural opening was not necessary whilst performing posterior fossa or foramen magnum decompression was first described in 1997 (7). This was based on the understanding that the dura is an expansile structure and can never be a compressive factor (20, 31). Opening of the dura is not only unnecessary but also subjects the patient to an increased risk of cerebrospinal fluid fistula. It makes an otherwise simple surgery into a relatively complex and dangerous surgical maneuver. Our experience suggests that only bony decompression of the foramen magnum is sufficient even in cases with Chiari malformation associated with syringomyelia. Foramen magnotomy, a procedure that involves reversal of the suboccipital bone flap and placement in the region in a manner that the convex posterior surface of the occipital bone faces outwards can be effectively used in such a situation. The flap provides area for bone fusion is necessary and curves away from the neural structures to provide neural decompression (6). Chiari 1 malformation and secondary syringomyelia frequently are not associated with basilar invagination. The exact cause of Chiari malformation in such cases is only speculative.(34) However, the treatment even in such cases is only foramen magnum bone decompression. (10, 24) Treatment of basilar invagination and atlantoaxial dislocation in cases with rheumatoid arthritis: Basilar invagination is commonly associated with atlantoaxial dislocation and the complex results in a significant degree of neck pain and myelopathy adding considerably to the disability secondary to affection of other joints. A number of treatment options are available in the treatment that includes drug therapy and non-operative treatment. We recently reported the feasibility of craniovertebral region bone alignment, distraction of the facets of atlas and axis and direct lateral mass plate and screw atlantoaxial fixation for management of both basilar invagination and atlantoaxial dislocation secondary to rheumatoid arthritis. (15) Our operation of craniovertebral realignment and stabilization without any bone decompression could be successfully employed in cases with atlantoaxial dislocation in the presence or absence of retro-odontoid pannus and in cases with basilar invagination. The patients showed a remarkable and sustained neurological and radiological improvement. It was recently demonstrated that following atlantoaxial joint distraction there was

778 Spine immediate postoperative reversal of retroodontoid pannus, in addition to reduction of the atlantoaxial dislocation and of basilar invagination (8). This finding suggests that retro-odontoid pannus, basilar invagination and atlantoaxial dislocation are all related to atlantoaxial joint arthritis, lateral mass ‘collapse’ and reduction of the joint space. The laxity of the posterior longitudinal ligament results in its posterior bulging. The exact role of inflammation in the formation of the pannus needs to be re-evaluated. Distraction of the facets results in stretching of the posterior longitudinal ligament and reduction of the pannus and reduction of basilar invagination and atlantoaxial dislocation. Treatment of craniovertebral junction tuberculosis: Our analysis and review of literature suggests that tuberculous infection more frequently starts unilaterally by involving the cancellous part of the facet of atlas. (17) Less frequently, the cancellous portion of the facet of axis and of odontoid process is the site of beginning of disease. The joint involvement is a result of extension of the inflammatory reaction. The incompetence of the joint and osseous and the adjoining ligamentous destruction in such a situation has been known to result in subluxation of the atlantoaxial facets. However, due to the presence of normal atlantoaxial joint on the contralateral side, the region is not alarmingly unstable and the patient generally presents with symptoms of pain and torticollis. Neurological deficits are notably delayed and less pronounced despite the aggressive destruction by the disease. Due to the presence of relatively stable craniovertebral region, despite the unilateral facetal destruction and the effectiveness of the modern anti-tuberculous drugs, surgery for fixation is not universally recommended in such cases. The management of tuberculosis involving craniovertebral junction and the need for surgery in such cases, particularly when there is a presence of atlantoaxial dislocation, is a highly debated subject. In the presence of destruction of the facets of atlas and axis on one side, it appeared that the alar and transverse ligament becomes unilaterally incompetent. The contralateral facets are normal for a significant period of time and can be used for stabilization of the region. The shift of balance on the contralateral side and the obliquity of the inclination of the facet of atlas in the atlantoaxial joint can even result in its lateral dislocation over the facet of axis. Under the circumstances, unilateral fixation of the atlantoaxial joint with or without the addition of distraction of the facets can result in stabilization of the region and realignment of the distorted anatomy. It appears that such a unilateral treatment of the joint in cases with tuberculosis of the craniovertebral junction can be a reasonable surgical option in a number of patients having tuberculosis of the craniovertebral junction. It appears that that lateral dislocation of the atlas over axis secondary to osteoligamentous incompetence can be a defined and treatable pathological entity. (17)

REFERENCES 1. Cacciola F, Phalke U, Goel A. Vertebral artery in relationship to C1-C2 vertebrae: An anatomical study. Neurol India. 2004; 52(2):178-84. 2. Chamberlain WE. Basilar impression (platybasia). A bizarre developmental anomaly of

Treatment for craniovertebral instability

3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25.

779

the occipital bone and upper cervical spine with striking and misleading neurologic manifestations. Yale J Biol Med 1939; 11:487-496. Driesen W. [Findings at operation in the central nervous system in basilar impressions and related abnormalities of the atlanto-occipital region]. Acta Neurochir 1960; 9:9-68 (Ger). Goel A, Kulkarni AG: Screw implantation in spinous process for occipitoaxial fixation. Journal of Clinical Neuroscience 2004; 11(7): 735-737 Goel A, Laheri VK. Plate and screw fixation for atlanto-axial dislocation. (Technical report). Acta Neurochir (Wien) 1994; 129:47-53. Goel A, Achawal S. Surgical treatment for Arnold Chiari malformation associated with atlantoaxial dislocation. Br J Neurosurg 1995; 9: 67-72. Goel A, Bhatjiwale M, Desai K: Basilar invagination: a study based on 190 surgically treated cases. J Neurosurg 1998; 88:962-968. Goel A, Dange N. Immediate postoperative regression of retroodontoid pannus after lateral mass reconstruction in a patient with rheumatoid disease of the craniovertebral junction. Case report. J Neurosurg Spine. 2008;9(3):273-6 Goel A, Desai K, Muzumdar D: Atlantoaxial fixation using plate and screw method: A report of 160 treated patients. Neurosurgery 2002; 51:1351-1357 Goel A, Desai KI: Surgery for syringomyelia: An analysis based on 163 surgical cases. Acta Neurochir (Wien) 2000; 142:293-302. Goel A, Karapurkar AP: Transoral plate and screw fixation of the clivus to the cervical body. Br J Neurosurg 1994;8: 743-745. Goel A, Kulkarni AG, Sharma P: Reduction of fixed atlantoaxial dislocation in 24 cases: technical note. J Neurosurg Spine. 2005;2(4): 505-9. Goel A, Kulkarni AG: Mobile and Reducible Atlantoaxial Dislocation in Presence of Occipitalized Atlas: Report on Treatment of Eight Cases by Direct Lateral Mass Plate and Screw Fixation. Spine 2004; 29(22):E520-E523 Goel A, Muzumdar D, Dange N. One stage reduction and fixation for atlantoaxial spondyloptosis: report of four cases. Br J Neurosurg. 2006;20(4):209-13. Goel A, Pareikh S, Sharma P. Atlantoaxial joint distraction for treatment of basilar invagination secondary to rheumatoid arthritis. Neurol India. 2005; 53(2): 238-40. Goel A, Shah A, Rajan S Vertical mobile and reducible atlantoaxial dislocation. Clinical article. J Neurosurg Spine. 2009, 11(1): 9-14. Goel A, Shah A. Lateral atlantoaxial facetal dislocation in craniovertebral region tuberculosis: report of a case and analysis of an alternative treatment. Acta Neurochirurgica (Wein) 2009, July. (In press) Goel A, Shah A. Reversal of longstanding musculoskeletal changes in basilar invagination after surgical decompression and stabilization.J Neurosurg Spine. 2009;10(3):220-7. Goel A, Sharma P. Craniovertebral junction realignment for the treatment of basilar invagination with syringomyelia: preliminary report of 12 cases. Neurol Med Chir (Tokyo). 2005;45(10): 512-8. Goel A, Sharma P. Craniovertebral realignment for basilar invagination and atlantoaxial dislocation secondary to rheumatoid arthritis. Neurol India 2004;52(3):338-41. Goel A: Progressive basilar invagination after transoral odontoidectomy: Treatment by facet distraction and craniovertebral realignment. Spine 2005; 30: E551-555 Goel A: Atlantoaxial joint jamming as a treatment for atlantoaxial dislocation: a preliminary report. Technical note. J Neurosurg Spine. 2007; 7(1):90-4. Goel A: Double insurance atlantoaxial fixation. Surg Neurol. 2007; 67(2):135-9. Goel A: Is syringomyelia pathology or a natural protective phenomenon? J Postgrad Med 2001;47:87-8. Goel A: Treatment of basilar invagination by atlantoaxial joint distraction and direct

780 Spine lateral mass fixation. J Neurosurg Spine. 2004;1(3):281-6. 26. Goel A: Vertebral artery injury with transarticular screws (letter). J Neurosurg 1999; 90:376 27. Grob D, Magerl F. Operative stabilisierung bei fraketuren von C1 und C2. Orthopade 1987; 16:46-54. 28. Gunderson CH, Greenspan RH, Glaser GH, Lubs HA. The Klippel-Feil syndrome: genetic and clinical reevaluation of cervical fusion. Medicine 1967; 46:491-512. 29. Gupta S, Goel A: Quantitative anatomy of lateral masses of the atlas and axis vertebrae. Neurol India 2000; 48: 120-125 30. Klaus E. Rontgendiagnostik der platybasic und basilaren Impression. Fortscher Rontgenstr 1957; 86:460-469. 31. Kothari M, Goel A. Maternalizing the meninges: A pregnant Arabic legacy. Neurol India. 2006; 54(4):345-6. 32. Kothari M, Goel A. Transatlantic odonto-occipital listhesis: the so-called basilar invagination. Neurol India. 2007; 55(1):6-7. 33. McRae DL. Bony abnormalities in the region of foramen magnum: correlation of anatomic and neurologic findings. Acta Radiol 1953; 40:335-354. 34. Menezes AH. Primary craniovertebral anomalies and hindbrain herniation syndrome (Chiari I): data base analysis. Pediatr Neurosurg 1995; 23:260-269. 35. Thiebaut F, Wackenheim A, Vrousos C. New median sagittal pneumostratigraphical findings concering the posterior fossa. J Radiol Electrol 1961; 42:1-7. 36. Von Torklus D, Gehle W. The Upper Cervical Spine: Regional Anatomy, Pathology, and Traumatology. A Systematic Radiological Atlas and Textbook. New York: Grune & Stratton, 1972, pp 1-98. 37. Williams B. A critical appraisal of posterior fossa surgery for communicating syringomyelia. Brain 1978; 101:223-250.

781

Transoral approach to the skull base and the upper cervical spine VISOCCHI MASSIMILIANO Institute of Neurosurgery Catholic University of Rome, Italy Key words: Cranio Cervical Junction, Transoral Approach, Neuroendoscopy, Neuronavigation The transoral approaches have become commonplace in modern neurosurgical practice for treatment of ventral midline lesions of the clivus and upper cervical spine. Although the standard technique of transoral surgery is conceptually simple, anatomic relationships are not so readily appreciated. The anterior surgical approach to the craniovertebral junction (CVJ), is strictly related with the precise knowledge of the local anatomy, i.e. the occipital bone that surrounds the foramen magnum, the atlas and the axis vertebrae with their ligaments and muscles. The medulla oblongata, the cervicomedullary junction and the upper cervical spinal cord, with their meningeal covers, are encompassed by this complex enclosure. Neural compression along the entire circumference, vascular compromise, and abnormal cerebrospinal fluid (CSF) dynamics can occur secondarily to bony abnormalities that affect the CVJ (Fig 1). The knowledge of the anatomy, the biomechanics and the embryology of this region is of a paramount importance to understand its functional problems and to plan a correct surgical strategy in candidates for surgical correction.

782 Spine

ANATOMY OF BONE AND LIGAMENTS OF CVJ The transverse atlantal ligament ( 1 cm thick ) is the thickest, strongest spinal ligament. It is the major restraint for C1, anchoring it to the dens, and allowing C1 to rotate around the dens. The alar ligaments connect the occipital condyles and C1 lateral masses to the odontoid. The alar ligaments primarily function to prohibit excessive axial rotation and lateral bending between the occiput and C2. The transverse ligament is a component of the cruciate ligament; the latter has thin ascending and descending bands.

ANATOMY OF THE VERTEBRAL ARTERY Vertebral Artery (VA) can be divided in 4 segments: I Prevertebral; II Vertebral from C6 to C2 (left segment); III Vertebral from C2 to C1 (S - Kinking sement); IV Extravertebral – intracranial . Left VA ( vertebral artery ) arises off aortic arch in 4%. Collateral arising from VA: Anterior meningeal: arises at the body of C2 ( axis ), may feed chordomas or foramen magnum meningiomas, may also act as collateral in vascular occlusion- Posterior meningeal; Medullary ( bulbar ) aa; Anterior - Posterior spinal; PICA ( largest branch ).

Transoral approach to the skull base and the upper cervical spine

783

CLASSIFICATION OF DISORDERS OF THE CRANIOVERTEBRAL JUNCTION A. CONGENITAL 1. Malformation of occipital bone A. Manifestations of occipital vertebra (e.g., clivus segmentations, remnants around foramen magnum, proatlas remnants) B. Basilar invagination C. Condylar hypoplasia D. Atlas assimilation 2. Malformations of the Atlas A. Atlas assimilation, atlantoaxial fusion, aplasia of the atlas arches 3. Malformations of the axis A. Segmentation failure of C1-C2 or C2-C3; hypoplasia of the dens, ossiculum terminalis B. DEVELOPMENTAL AND ACQUIRED 1. Traumatic A. Acute ligamentous and bony injury to CVJ complex B. Delayed manifestations of CVJ instability. Development of os odontoideum 2. Inflammation leading to instability and granulation masses (e.g., rheumatoid arthritis, regional ileitis, psoriasis, scleroderma, pseudogout, ankylosing spondylitis) 3. Infections (e.g., Grisel’s syndrome) 4. Metabolic (e.g., Morquio’s syndrome, Conradi’s syndrome, fetal warfarin syndrome, renal rickets) 5. Genetic transformations (e.g., Down’s syndrome, osteogenesis imperfecta, achondroplasia, Paget’s disease, neurofibromatosis) 6. Neoplastic A. Benign (e.g., aneurismal bone cyst, osteoblastoma, osteochondroma, chondroma) B. Malignant 1. Primary (e.g., chordoma, chondrosarcoma, plasmocytoma) 2. Secondary (e.g., multiple myeloma, metastatic disease, nasopharingeal malignancy )

SURGICAL-PHYSIOLOGICAL APPROACH TO THE CRANIOCERVICAL JUNCTION The factors considered in developing a physiological approach to the surgical treatment of such lesions are ( 1 ) reducibility; ( 2 ) the direction and manner of encroachment of the lesion in the lesion in the craniovertebral circumference and its affect on the neural structures; ( 3 ) the etiology of the lesion ( whether it is bony, soft tissue, extracranial or intracranial, intramedullary or extramedullary ); ( 4 ) the potential growth attitude of the lesion. The stability of the region after a surgical approach is crucial as well as the indication to radical resection of chemotherapy-and radiotherapy-resistant

784 Spine tumors. Thus, reducible lesions require primary stabilization while irreducible lesions require decompression in the manner in which an encroachment has occurred, whether this be ventral, dorsal, or lateral. In any of the circumstances, if instability is present prior to treatment or after the surgical approach, stabilization is of paramount importance.

MENEZES’ CRITERIA

Menezes AH (1994) Occipito Occipito-cervical fusion: indications, technique and avoidance of complications. In: Hitchon PW (ed): Techniques of spinal fusion and stabilization Thieme New York, pp 82 – 91.

SURGICAL TECHNIQUE Head and Distractor Positioning The patient is placed in the supine position with the head resting on a pad. The patient is orally or nasally intubated. To be put into special consideration is the possibility of awake fiberoptic intubation technique in patients who have marked spinal instability. We exceptionally reserve a tracheostomy for those patients who have pre-existing bulbar or respiratory dysfunction or those who are undergoing a median labiomandibular glossotomy approach. Cervical traction, if applied preoperatively, can be implemented in the operating room for further reduction. We fixed the head with three-point skull fixation (Mayfield headrest) and put the neck slightly extended in order to facilitate a direct line of sight to the CVJ (Fig 1). In case of the use of transoral retractor system rigidly attached to the operating table, no more reduction is needed with three-point skull fixation since this prevents the retractors from moving intraoperatively and stabilize the patient's head (Fig 2). Proper positioning of the transoral retractor maximizes exposure and obviates the need to incise the soft palate or uvula to gain the needed exposure. The protection from the

Transoral approach to the skull base and the upper cervical spine

785

risk of injury or incision of the soft palate is mandatory since it could be difficult to repair and result in dysphagia, dysphonia, and nasal regurgitation of fluids. The patient's tongue is retracted inferiorly using a wide and rigid retractor blade. The endotracheal tube can be placed under the tongue retractor, but we prefer to roue it along the side of the mouth to reduce tongue compression. It exits the corner of the patient's mouth and does not obstruct the surgical exposure. The elevation of the soft palate and uvula superiorly by means of a small retractor blade attached to the transoral retractor, can maximize the exposure of the cephalad posterior pharynx. Finally an adjustable lateral retractors attached to the retractor frame allow to retract the pharyngeal soft tissues laterally. For teeth protection we use teeth guards, which are attached to the retractor frame, around the upper teeth. After the retractor system is in place, carefully inspect the tongue to confirm that it is free from compression between the retractor blade and the teeth. Failure to recognize this compression can result in necrosis or swelling of the tongue. Finally the mouth, oropharynx, and retractors are washed with Betadine solution. We prefer to operate from the head of the patient, using an operating microscope to enhance magnification and illumination. For the standard transoral and transoral-transpalatine dissections, the carotid arteries, abducens nerves, interior petrosal sinuses, hypoglossal nerves, and vertebral arteries would be a greatest risk being 0.76, 1.06, 1.51, 1.34, and 1.52 cm from the midline at specified locations. The measurements and the computed tomography images provide a useful reference for the surgeon. Surgical steps The tubercle of C1 is palpated before incision; however, this anatomic landmark may be absent or distorted in patients who harbor tumors in this location. By using a low cutting power, the incision is performed on the posterior pharyngeal wall longitudinally in the midline over the region that is to be resected. The longus colli and the longus capitis muscles are mobilized laterally and held in place with tooth-bladed lateral pharyngeal retractors to expose the inferior clivus, C1 arch, and C2 vertebral body. Bone removal through the arch of C1 on both sides of the odontoid process is obtained by using a highspeed drill. After bone decompression the removal of the transverse ligament, tectorial membrane, and any residual ligaments may be necessary to remove pannus / tumour or metabolic collection (i.e. mucopolisaccaroids). The aim of surgery is to decompress the underlying craniovertebral junction dura mater adequately; sometime it is necessary to remove the inferior clivus with a high-speed drill and rongeurs. In case of tumor (i.e. Chordoma) it may be adherent or may have infiltrated the dura mater. If the dura mater has been violated by the tumor, it is mandatory to take care not to injure the intradural structures, such as the basilar artery, perforators, and brainstem. In case of intraoperative cerebrospinal fluid leak, the dura mater can be repaired with autologous or allograft fascia lata, fat, and fibrin glue in several layers. Temporary lumbar drainage, which should be performed promptly at the end of the procedure, can help to gain a rapid success. Otherwise in case the dura mater is intact, the intraoperative contrast injection into the epidural space is strongly advised in order to check fluoroscopically the extent of the decompression (Fig 4). Closure is obtained by approximating the mucosal layers

786 Spine with simple interrupted 3-0 Vicryl sutures using the same needle in double fashion. The sutures should not be approximated too tightly because this could strangulate the delicate mucosal tissues. Postoperative Prophylactic antibiotics are administered intraoperatively and postoperatively. Topical corticosteroid cream can be applied to the tongue to minimize postoperative tongue swelling. The patient is fixed in Halo Vest and delivered into the Intensive Care Unit were he will be extubated no earlier than 24 – 36 hours after surgery in order to allow the tongue swelling to subside. Moreover he will be fed with nasogastric tube for one week, in order to protect the pharyngeal wound and to allow a complete healing. A double staged instrumentation and fusion procedure can be performed one week later according to Menzes’ alghorytm unless the surgeon should prepher one staged combined anterior and posterior approach after obtaining the patient’s informed consent. Usually, a complete postoperative radiological set is obtained before discharge and repeated every 3 months up to the complete bone fusion assessment, which requires no more than 6 months. X-rays are suggested monthly in order to check the stability of the construct. Xrays and CT provide information on the ongoing bone fusion and MR confirm the effective decompression of neural structures (Fig 5).

CONSIDERATIONS The transoral-transpharyngeal approach appears to be relatively easy. It is associated with minimal complications and provides excellent exposure of the odontoid and upper cervical vertebrae for a microneurosurgical approach. Modifications of this approach include incision of the soft palate, excision of a portion of the hard palate, and occasionally, transmandibular median labio-mandibuloglossotomy (Trotter's) approach. Although the technique was described initially approximately 38 years ago, this neglected anatomic approach will facilitate cooperative efforts between head and neck surgeons and neurosurgeons. Neuronavigation is a useful tool for planning and performing a transoral approach (Fig 1). It optimizes preoperative planning, clarifies and secures resection limits, and reduces overall surgical morbidity. Transoral endoscopic assisted approach long with pure endoscopic approach deserve consideration but it seems to need more anatomic studies and clinical trials.

Fig. 1 Positioning of the head with the Mayfield headholder and the skin fiducials for neuronavigation in the operating room

Transoral approach to the skull base and the upper cervical spine

787

Fig. 2 The patient is placed in the supine position with the head resting on a pad. The neck is slightly extended to facilitate a direct line of sight to the craniovertebral junction. The patient is nasally intubated. A transoral retractor system can be “stand alone” (Crockard distraction) (left) or rigidly attached to the operating table with crossbars to prevent the retractor and the patient's head from moving intraoperatively (right).

Fig. 3 Preoperative MR imaging of Rheumatoid Artritis (T2 weighted) showing odontoid inflammatory pannus compressing the brain stem and microinstability of the subaxial spine

Fig. 4 Intraoperative fluoroscopy is used throughout the operation. Assessment of transoral distractor positioning (left) and odontoid decompression after local injection of iopamiro (right) is easily performed.

788 Spine

Fig. 5 Postoperative CT (left) and MR ( T2 weighted imaging) (right) showing postoperative decompression of the odontoid and brain stem.

Fig. 6 Postoperative X Rays standard (left) and axial cervical CT TC (right) showing two screws on the occiput crest (Opistion Inion) and 6 screws (4 mm in diameter and 14nn in lenght) in the C2 pedicles (upper right) and lateral masses of C3 and C4 lower right).

REFERENCES 1. Dickman CA, Spetzler RF, Sonntag VHK: Surgery of Craniocervical Jjunction

Thieme (New York, Stuttgard) (1998), pag 828. 2. Visocchi M, Cabezas Cuevas D, Di Rocco C, Meglio M: Craniocervical instability, instrumentation and fusion: personal experience with contoured titanium bar and sublaminar wires. Presented at the 12th World Congress of Neurosurgeon Sidney, Australia, September 16 – 20, 2001. 3. Visocchi M, Di Rocco F, Meglio M: Craniocervical junction instability: instrumentation

Transoral approach to the skull base and the upper cervical spine

4. 5. 6.

7.

789

and fusion with titanium rods and sublaminar wires. Effectiveness and failures in personal experience. Acta Neurochir (2003) 145:265 – 272. Visocchi M, Fernandez E, Ciampini A, Di Rocco C: Reducible and irreducible os odontoideum. Is there still a role for posterior wiring in instrumentation and fusion in childhood? Acta neurochir (Wien – Austria) (2009) 152: 1- 10. Visocchi M, Pietrini D, Tufo T, Fernandez F, Di Rocco C: Preoperative irreducible C1 C2 dislocations: intraoperative reduction and posterior fixation. The “always posterior strategy” Acta neurochir (Wien – Austria) (2009) 151: - 551 – 560. Visocchi M: . Response to Wang et al., re Letter re Visocchi M, Pietrini D, Tufo T, Fernandez E, Di Rocco C Pre-operative irreducible C1-C2 dislocations: intra-operative reduction and posterior fixation. The "always posterior strategy". Acta Neurochir (Wien) (2009) 151(5):551-9; discussion 560. Visocchi M: La cerniera craniocervicale: anatomofisiopatologia e neurochirurgia instrumentata posteriore. Aracne ed (Rome, Italy) (2009), 1 - 192.

790

Cervical posterior approach: Laminoplasty SATOSHI TANI, M.D. Department of Neurosurgery, Jikei University Scool of Medicine, Minatoku, Tokyo, Japan Key words: Cervical laminoplasty, Cervical laminectomy, Cervical spondylosis, Cervical OPLL

Laminoplasty 1. Surgical indication and choice of procedure A cervical posterior decompressive procedure such as laminectomy and laminoplasty is usually chosen for cervical myelopathy in cervical spondylosis and/or ossification of longitudinal ligament and/or cervical disc hernia. The indications for this procedure are based on the condition with multiple level pathology (usually two levels or more) and lordotic or straight spine with developmental narrow spinal canal (12 mm or less in AP diameter) (Table 1). In terms of treating multilevel cervical myelopathy, long term outcome seems to be better compared with multi-level anterior surgery (1). Table 1 Indications for posterior decompression

Even if efficacy of laminoplasty has been controversial for a long time (6), it has been getting more popular than laminectomy since it was introduced in 1983 (3) Some advantages of laminoplasty are as follows; less violation of the cervical posterior bony elements, unilateral laminotomy that may have a chance of root injury, less posterior shift of the decompressed spinal cord, and less chance of postoperative spinal deformity (Table 2). Laminectomy with fusion is another choice to avoid postoperative deformity, however, it may have more chance of complications (2). Laminoplasty is usually classified into two groups; open door and French door (bilateral open door). In both ways, the approach to laminae is identical while preserving posterior elements (5.7), and the concept of maximal reconstruction of the spinal canal including the spinous processes and attaching muscles is not different. Many kinds of spacers made of ceramics or titanium are commercially available to facilitate stabilization of the enlarged laminararch (4.5.7). The author has been using a titanium spacer for the

Cervical posterior approach: Laminoplasty

791

Table 2 Comparaison in laminectomy and laminoplasty

Fig. 1 Photograph of the titanium spacer (L-Basket, Amtec, Japan) Table 3 Comparison in open door procedure and French door procedure

advantages of its plasticity and easier fixation by small screws compared with ceramic spacers (Figure 1). There are some technical difference sbetween open door and French door techniques as indicated in Table 3.

2. Surgical technique of laminoplasty A. open door laminoplasty (C3-C6) (Figure 2) 1 Anesthesia The patient is anesthetized and intubated with endoscopic guidance to avoid hyperextension of the neck.

792 Spine

Fig. 2 hotographs of postoperative CT scans (open door laminoplasty) Excellent bone fusion at the gutter and the gap between lamina and spinous process are well demonstrated 3 months after surgery.

2 Position The patient is placed prone with the neck fixed in neutral position by the Mayfield head clamp. Too much flexion to obtain flattened nuchal area should be avoided to prevent further cord injury. The whole table is adjusted with elevated head and neck for diminishing blood loss. 3 Skin incision Palpating the spinous processes of C2 and C6 or C7, a linear skin incision is made from C2 to C7 in the midline. This incisions is deepened to reach the nuchal ligament that attaches to C7 spinous processes. 4 Muscle dissection The nuchal ligament and its deeper part are dissected along with the spinous processes to expose them unilaterally with laminae, while preserving interspinous muscle and ligament(Figure 3). Sub-perioseteal dissection reduces blood loss and muscle damages of semispinalis, multifidis and rotators. Too much exposure of the facet portion should be avoided, and facet capsule should remain intact. Hemostasis of emissary veins of the laminae is done with bone wax. To maintain the spinal curvature, the semispinalis cervicis muscle attaching to the lower part of the C2 spinous process should not be violated. 5 Amputation of the spinous processes After the full-length exposure of the left sided laminae from lower part of C2 to upper part of C7, horizontal amputation of the spinous processes of C3 to C6 are done by a bone saw (Figure 3). Care should be taken not to cut the spinous processes at their base to avoid laminar split. 6 Laminar exposure Bilateral laminar exposure should be carried out in a sub-periosteal fashion to the medial part of the right side facets (Figure 3). During this procedure, care should be taken

Cervical posterior approach: Laminoplasty

793

Fig. 3 Common approach of laminoplasty a: The spinal cord is compressed from the anterior surgical pathology b: Unilateral opening of the spinous processes and the laminas c: Horizontal amputation of the spinous processes d: Bilatera exposure of the laminae

not to injure the interspinous ligaments, papticularly that between C2 and C3. Connective tissue around laminae should be removed intensely in order to identify anatomical structure. 7 Partial laminectomy Lower part of C2 is removed by an air or electric drill with steel burr. The upper part of C7 laminae should be removed gently, occasionaly using diamond head. On both sites, remnant shell-like laminae are removed by Kerrison rongeur and the decompression should be done wide enough, so that we can identify the lateral surface of the spinal dura. Minor bleeding may occur on the lateral side, but, it is easily controll by some hemostatic material. One point memo The reason why you start partial laminectomy at the lower C2 end is that the procedure is safer because of underlining ligamenta flava. You had better start drilling procedure in the eaier part until you get used to the power tool. 8 Laminotomy When we do not have to make additional partial facetectomy, the laminotomy is usually performed in the left side (Figure 4). A laminotomy should be carried out with a 2-3 mm cutting burr on the estimated lateral laminar border line (lamino-articular line). The lower part of the lamina is drilled out to indentify underlying ligament flava, however, drilling of the upper part of lamina should be done carefully not to damage any

794 Spine

Fig. 4 Schemas of the open door laminoplasty a: Unilateral laminotomy and gutter on the hinge side b: Elevation of the laminae c: Insertion and fixation of the spacers d: Approximation of the divided spinous processes

epidural veins or dura. A diamond bar can be also usuful to avoid such complications. Exposure of the lateral side of thecal sac is accomplished by removing epidural tissues by small Kerrison rongeur under the microscope. 9 Making gutter on the hinge side After confirming the lateral edge of the thecal sac, the outer cortical bone of each lamina is separately drilled out slightly more lateral than on the already opened side (laminotomy side) (Figure 4). The drilling should start from C3 and continue until the corresponding lamina can be slightly moved up. Care should be taken not to remove too much of outer coritcal bone. One point memo The upper part of the lamina is usually the main cause for resistance in smooth elevation of the lamina. Therefore, the most important point of this “gutter” drilling procudre is careful but effective unilateral decortication of the upper part of lamina. It is better to use a diamond burr when you are not used to make “gutter”. 10 Elevation of the laminae Laminae are elevated one by one while any remaining yellow ligament and adhesive fibrous bands between the dura and the inner surface of the lamina are carefully devided(Figure 4). Usullay this procedure is started from the most rostral lamina.

Cervical posterior approach: Laminoplasty

795

11 Fixation of the laminae A titanium spacer (Figure 1) is deformed to fit the shape and angle of the elevated lamina as well as with space between the lamina and facet (figure 4). After small holes are drilled, the titanium spacers are fixed with 3mm length screw to the elevated lamine. The assistant should pay attention to protect against excessive motion around the hinge. Subsequent to fixing all spacers to the laminae, the contralateral side of the spacers are also fixed to the lateral masses by screws. 12 Approximation of the divided spinous processes After making small holes in the divided spinous process and the elevated lamina, a thick suture is introduced from the left side of the spinous process to the other side, and subsequently the suture goes through the two holes made in the elevated lamina. After release of the self-retaining retractor, all spinous processes are reapproximated in the midline (Figure 4). 13 Closure of the wound Absolute hemostasis is ascertained. Following placement of a negative pressure drain system along the open side (left side of the spinous processes), nuchal ligament, subcutaneous fat layer and sub-cutaneous tissue are sutured in layer-to-layer fashion. Approximation of the muscle layers should be avoided to minimize postoperative neck pain. Local anesthetic agent may be applied into the paravertebral muscles for pain control. 14 Postoperative care The patient should ware a cervical soft collar and can ambulate postoperatively. The cervical collar is usually removed 2 to 3 weeks after surgery when cervical alignment in the outpatient office is radiologically confirmed. As the fixation by titanium spacers seems to be firm, bone union around the hinge can be achieved by 3 months postoperatively (Figure 2). B. French door laminoplasty (C3-C6) (Figure 5)

Fig. 5 Postoperative CT scans (open door laminoplasty) Bilateral elevated laminae are well maintained 1 month after surgery.

796 Spine

Fig. 6 Schemas of the French door laminoplasty a: Elevation of the bilateral splitted laminae b: Insertion and fixation of the titanium spacers and approximation of the divided spinous processes

An identical to the open door laminoplasty approach should be done upto the stage of partial laminectomy. Closure of the wound and postoperative care are also identical. 8. Laminotomy The center of the lamina is drilled for laminotomy, however, there is no anatomical protection for the thecal sac such as ligamenta flava. Final separation of the lamina can be achieved by gentle removal of the residual bony layer by a small Kerrison ronguer (Figure 6). 9. Making gutters The outer cortical bone of the each lamina is drilled out separately at the bilateral lamino-articulr lines. The drilling procedure should continue until the corresponding lamina is slightly moved or elevated. Care should be taken not to remove too much outer coritcal bone of the laminae. 10. Elevation of the laminae Two posterior arch halves are separated apart to open the spinal canal. Dissection of the space between dura and the inner surface of lamina is easy. 11. Fixation of the laminae A titanium spacer (Figure 1) is bended to fit with the inclination of elevated laminae. After the small holes are drilled, the titanium spacer is fixed with 3mm screws (Figure 6). The screws can be usually placed at the tip or lateral side of the elevated lamina. In case of trouble with screw fixation (it depends on the inclination of laminae and depth of the surgical wound), a thread can be used for fixation of the spacer. 12. Approximation of the divided spinous processes A devided spinous process and its attaching muslces is approximated at the center of the spacer. To facilitate the bone union around the spinous process, you may insert small local bone chips into the spacer.

Cervical posterior approach: Laminoplasty

797

3. Standard surgical outcome of laminoplasty for the need of preopeartive informed conscents Operation time: approximately 2 hours Blood loss; less than 100 ml Surgical complications related to neural structure; less than 1% Postoperative transient C5 palsy; approximately 5%

Foraminotomy 1. Surgical indications The keyhole foraminotomy has been adopted for the posterior decompression of the nerve roots affected by soft disc protrusions or spondylotic spurs projecting into the foramen. Surgical indications are as follows: persistent symtoms and signs related to root compression such as intractable radicular pain, motor weakness, positive accertaining radiological findings on MRI and CT scan.

2. Surgical technique 1. Anesthesia A patient is anesthetized and intubated in the usual way. 2. Position The patient is placed in prone position with the neck slightly flexed in the Mayfield head clamp to expose sufficient interlaminar space. The head and neck are placed higher wiht the operating table to reduce blood loss. 3. Skin incision Using spinous process landmarks, a 4cm long midline skin incision is made in the midline. 4. Muscle dissection and exposure of the interlaminar space The nuchal ligament and its deeper part are dissected to expose the spinous process of interest unilaterally. After the radiological confirmation, the dissection should extend to the lateral part of facet. Less bleeding is seen if the dissection is kept in the subperiosteal plane along the spinous process, lamina and facet. Hemostasis for an emissary vein of the laminae is done by bone wax. A pronged self-retaining retractor is applied to the paraspinous muscle mass. 5. Foraminotomy Clearing overlying soft tissues makes it posibble to identify the interlaminar space and the medial facet-interlaminar space. A partial laminotomy is initially carried out by the high-speed steel burr under the microscope. The posterolateral portion of the both laminae and the medial facet are then removed (Figure 7). The nerve root is located just

798 Spine

Fig. 7 Schemas of foraminotomy Left: A solid round circle indicated by an arrow sows the area removed. Right: The nerve root is well decompressed through the partial facetectomy. P:pedicle, R: nerve root

Fig. 8 Postoperative CT scans after foraminotomy The medial one-third of facet is removed over the nerve root.

above the pedicle and immediately under the superior facet (Figure 7). The ligaments flava are removed from medial to lateral around the root. The residual posterior foraminal wall is drilled out by using a diamond bar. Further removal of inferior and superior facet parts is done by currete or small Kerrison rongeur utilizing a plane of dissection between the nerve root and the anterior aspect of the superior facet. Care should be taken not to compress the nerve root strongly. A trumpet-shape laminotomyfacetectomy should be kept within the superficial half of the facet portion in order to keep stability (Figure 8). Usually decompression area extends 5mm laterally to the lateral border of the thecal sac and directs a little caudally. Confirming complete decompression over the root is to feel some space dorsal by a microdissctor. In most cases of soft disc hernia, the compressed root is gently retracted upward and the extruded disc fragments can be removed with a small disc ronguer through the axilla of the root.

Cervical posterior approach: Laminoplasty

799

One point memo How deep you should remove the bone component above the nerve root should be preoperatively measured (might be deeper than your assumption). 6. Hemostasis Epidural bleeing frequently occurrs from the venous plexus along with the nerve root. Careful coagulation around the nerve sleeve and subsequent placement of a hemostatic material should be done. 7. Closure Following placement of a negative pressures drain system, the nuchal ligament, fat layer and sub-cutaneous tissue are sutured layer-to-layer. Local anesthetic agent may apply into the paravertebral muscles for pain control. 8. Postoperative care The patient should ware a cervical soft collar and can ambulate postoperatively. The cervical collar is usually removed 2 to 3 weeks after surgery when cervical alignment in the outpatient office is radiologically confirmed.

3. Standard surgical outcome of facetectomy for the need of preopeartive informed conscents Operation time: approximately 1.5 hours Blood loss; less than 30 ml Surgical complications related to neural structure; less than 5%

REFERENCES 1. Edwards CC 2nd, Heller JG, Murakami H: Corpectomy versus laminoplasty for multilevel cervical myelopathy: an independent matched-cohort analysis. Spine 27: 1168-1175, 2002 2. Heller JG, Edwards CC 2nd, Murakami H, et al: Laminoplasty versus laminectomy and fusion for multilevel cervical myelopathy: an independent matched cohort analysis. Spine 26: 1330-1336, 2001 3. Hirabayashi K, Watanabe K, Wakano K, et al: Expansive open-door laminoplasty for cervical spinal stenotic myelopathy. Spine. 1983;8: 693-9 4. Kihara S, Umebayashi T, Hoshimaru M: Technical improvements and results of opendoor expansive laminoplasty with hydroxyapatite implants for cervical myelopathy. Neurosurgery. 2005;57: 348-56 5. Kim P, Murata H, Kurokawa R, et al: Myoarchitectonic spinolaminoplasty: efficacy in reconstituting the cervical musculature and preserving biomechanical function. J Neurosurg Spine. 2007;7: 293-304 6. Ratliff JK, Cooper PR: Cervical laminoplasty: a critical review. J Neurosurg. 2003; 98:230-8. 7. Tani S, Isoshima A, Nagashima H, et al: Laminoplasty with preservation of posterior cervical elements: surgical technique. Neurosurgery 2002; 50: 97-102.

800

Anterior approach to the cervical spine for degenerative spinal disorders IZUMI KOYANAGI, M.D. Department of Neurosurgery, Sapporo Medical University School of Medicine, Sapporo, Japan Key words: Anterior approach, Anterior fusion, Cervical spine, Cervical spondylosis, OPLL Anterior approach is indicated for anterior decompression and fusion of the cervical spine in degenerative cervical spine disorders such as disc hernia, spondylosis and OPLL (ossification of the longitudinal ligament). This approach is one of the most fundamental neurosurgical procedures. However, careful surgical dissection is needed with the anatomical knowledge of the anterior cervical structures (Fig.1).

Fig. 1 The anterior cervical approach (dotted arrow) and anatomical structures.

Patient position The patient is placed in supine position under general anesthesia. It is important to avoid unnecessary or excessive neck manipulation during tracheal intubation. A thin pillow (or a rolled towel) is placed under the shoulder. The neck is slightly or mildly extended and the head is slightly rotated to the left. The main operator stands right to the patient and the assistant surgeon stands at the opposite side (Fig.2).

Anterior approach to the cervical spine After infiltration of the local anesthetic agent, transverse skin incision over the right anterior surface is made for simple one or two level fusion. The approximate level of C5/6

Anterior approach to the cervical spine for degenerative spinal disorders

801

Fig. 2 Position of the operators around the operating table in anterior cervical approach.

Fig. 3 Skin incision for anterior approach to the cervical spine.

is at the lower border of the thyroid cartilage. Oblique skin incision just medial to the right sternocleidomastoid muscle is used for longer fusion or complex cases (Fig.3). In case of transverse incision, the platysma is cut transversely and undermined rostrally and caudally using the dissecting scissors (Fig.4-A). The superficial layer of the cervical fascia is dissected to expose the right omohyoid muscle (Fig.4-B). The space between the sternocleidmastoid and the omohyoid muscles is dissected to the prevertebral space. In the first step, the common carotid artery and internal jugular vein are gently retracted laterally with a surgeon’s finger and palpate the anterior surface of the vertebral body. Then, the thyroid muscles and the trachea are retracted medially with a muscle retractor (Fig.5). The interface between these structures is gently dissected to expose the prevertebral space. The prevertebral fascia is picked up with forceps and is dissected to fully expose the longus colli and the vertebral body. The common carotid artery sometimes runs close to the vertebral body due to arteriosclerosis. Esophagus is situated in front of the vertebral body and should be protected by the retractor (Fig.6). After exposing the prevertebral area, a bended 20G needle is inserted to the disc space and the spinal level is confirmed by the C-arm fluoroscopy. The confirmed disc space is marked with dye. The medial sides of the longus colli muscles are dissected from the vertebral

802 Spine

Fig. 4 Surgical steps of the anterior approach. A: Dissection of the platysma and the superficial cervical fascia. B: Exposure of the omohyoid muscle.

Fig. 5 Surgical approach to the prevertebral space. Gentle dissection between the thyroid and the cartoid sheath. These structures are retracted by the muscle retractor and a surgeon’s finger.

body using bipolar coagulating forceps or a monopolar coagulator. The blades of the Cloward type retractor are placed under the longus colli muscles to avoid injury to the esophagus and carotid artery (Fig.7).

Discectomy and osteophytectomy The anterior longitudinal ligament and the disc surface are incised using a No.15 scalpel. Disc materials are removed with a rongeur and a curette. A Cloward type spreader is used to further decompress the intervertebral space. Uncinate process is the

Anterior approach to the cervical spine for degenerative spinal disorders

803

Fig. 6 Important structures during the anterior approach. The common carotid artery is visible laterally (A) and esophagus medially (B).

Fig. 7 Exposure of the vertebral body. A bended needle is inserted to the disc space and the spinal level is confirmed using fluoroscopy. Blades of the Cloward type retractor are placed under the longus colli.

landmark for lateral exposure (Fig.8). The operative microscope is usually introduced at this point. Osteophytes are removed with drilling and curettage. First, the anterior edge of the vertebral body and posterior spurs are drilled using a diamond bur of 4 or 5 mm diameter. Then, the smaller diameter diamond bur (3 mm) is used for drilling the posterior and posterolateral spurs compressing the spinal cord and the root sleeve (Fig.9). The drilled posterior spurs are carefully removed using the curette (Fig.10). The disc materials often protrude or migrate into the space between the layers (the deep and the superficial layers) of the posterior longitudinal ligament (PLL). The PLL is carefully elevated using a rectangular nerve hook and cut with a No.15 scalpel to inspect the

804 Spine

Fig. 8 Intraoperative photographs of cervical discectomy. The anterior longitudinal ligament and the anterior part of disc are cut wit a No.15 scalpel (A). Disc material is removed using a rongeur and a curette to expose the end plate (B). The disc space is opened with a spreader. The uncinate process is the landmark for lateral exposure (C).

Fig. 9 Illustration (A) and intraoperative photographs (B,C) showing drilling of the bony spur. Note the direction of the microscope (arrows) and drilled regions (shaded areas). Bony spurs at the upper (B) and lower (C) corners of the vertebral bodies are drilled using a high speed drill (diamond bur).

Fig. 10 Illustration (A) and intraoperative photographs (B,C) showing removal of the bony spur with a curette. Rotation of the curette effectively remove the corner of the vertebral body.

Anterior approach to the cervical spine for degenerative spinal disorders

805

Fig. 11 Illustration (A) showing the layers of posterior longitudinal ligament (PLL) and migrated disc hernia. Intraoperative photographs showing steps of PLL removal. The PLL is elevated using a rectangular micro-hook (B) and cut with a No.15 scalpel (C). The central part of PLL is carefully removed (D).

migrated disc materials. The hypertrophied PLL is removed using a Kerrison punch and the curette to obtain enough decompression. Laterally, there is the venous plexus between the deep and the superficial layers of the PLL (Fig.11). The venous plexus is the lateral border of PLL removal.

Fusion procedure Tricortical bone is harvested from the right iliac crest (Smith-Robinson method). Usually, the height of the bone graft is 8 mm. The disc space is opened with a spreader and the graft bone is inserted into the space. A bone graft impactor is used to adjust the position of the graft bone. The graft is firmly fixed between the vertebral bodies by removing the spreader (Fig.12).

Corpectomy and fusion In case of OPLL or extensive bony spur, corpectomy is performed to decompress the spinal cord using a high-speed drill (Fig.13). OPLL is usually thick cortical bone and is drilled with diamond bur (Fig.13-A), then removed using a small curette or a thin-blade Kerrison punch. The ventral dura is sometimes ossified in large OPLL. In such a case, the ossification is carefully thinned using diamond-bur drilling (Fig.13-B), so that the

806 Spine

Fig. 12 Illustration (A) and intraoperative photographs (B-D) showing anterior fusion with tricortical iliac bone graft (Smith-Robinson method). Disc space is opened with a spreader and an iliac bone graft is inserted into the space (B). A bone graft impactor is sometimes used to obtain adequate position (C). The graft bone is fixed between the vertebral bodies after removing the spreader (D).

Fig. 13 Illustrations and intraoperative photograph showing corpectomy and anterior fusion with long bone grafting. OPLL is drilled using a diamond bur (A). Ossified dura mater is carefully drilled to obtain dural decompression (B). Tricortical bone graft is harvested from the iliac crest and inserted into the decompressed segment (C,D). Note the bank of the vertebral bodies (asterisks) for graft placement. Anterior plating is often used to prevent graft dislocation (E).

Anterior approach to the cervical spine for degenerative spinal disorders

807

decompressed dura mater is bulged by the subarachnoid cerebrospinal fluid (CSF) pressure. If the dura mater and arachnoid membrane are torn, the fat tissue or fascia and fibrin glue are used for dural repair. For the patient showing large dural defect, lumbar CSF drainage is performed after surgery for 5 days. Tricortical bone graft is harvested from the iliac crest. The length of the graft bone depends on the number of corpectomy. To prevent graft bone dislocation, the small “bank” is made at the anterior and posterior edge of the vertebral body (Fig.13-D). If the anterior plating is concomitantly used, there is no need to make anterior “bank” (Fig.13-E).

Substitutes of graft bone Several types of titanium cages (Fig.14) or other spacers have been used to avoid complications associated with iliac bone harvesting. The titanium cages are packed with the local bone from the vertebral bodies, the cancerous bone from the iliac crest or artificial bone materials such as tricalcium phosphate and inserted into the disc space or the intervertebral space after corpectomy.

Fig. 14 Titanium cages as the substitute for iliac bone grafting. One or two threaded cages are inserted into the disc space (A) for discetomy and fusion. The mesh cage is used for reconstruction of the vertebral body after corpectomy (B).

Wound closure A wound drainage tube is placed in front of the vertebral body. Platysma and the subcutaneous tissue are stitched using 4-0 absorbable sutures. 5-0 nylon sutures or skin tape is used for skin closure.

Postoperative care Cervical collar is used for external immobilization of the neck. The period of collar fixation is usually 4 weeks for one-level fusion and 5-6 weeks for two-level fusion. Cases of corpectomy or more multilevel fusion needs longer collar fixation period (8 to 12 weeks).

808

Surgical Management of Cervical Disc Herniation PATRICK-ALAIN FAURE, JEAN-JACQUES MOREAU, GILBERT DECHAMBENOIT Department of Neurosurgery – CHU of Limoges - FRANCE Key words: cervical disc, herniation, arthrosis, osteophytes, interbody fusion, foraminotomy, facetectomy Cervical disc herniation is one of the most frequent pathologies of the cervical spine. This usually presents in two types - either smooth form, or hard form. Clinically, there are mainly two types of syndromes associated with cervical disc herniation - either a radicular or a spinal cord compression. These two clinical pictures can be associated, but the most frequent is the cervico-brachial neuralgia. The prevalence of cervical radicular pain is 3.3/1000. The annual incidence is 2.1/1000, and occurs most commonly in the fourth and fifth decade. [40]. The frequency is slightly higher in women [41]. According to an epidemiological study on cervical radiculopathies carried out at the Mayo Clinic (Rochester), physical exercise or trauma prior to the onset of symptoms accounts for only 14.8% of cases [42]

Pathophysiology The cervical region is the most mobile segment of the vertebral column. Although it is not exposed to excessive axial compressing forces compared the lumbar spine, the cervical spine is more likely to undergo premature degeneration due to its physiological hypermobility [38, 24]. This local hypermobility is responsible for disc degeneration, and development of osteoarthritis. Concerning the anatomo-functional subdivision, the cervical spine is made up of two sub-segments opposing each other. The superior segment C1-C2 has no intervertebral disc between C0 (occiput) and C1, and also between C1 and C2; this segment is rarely involved with spinal osteoarthritic degeneration. The inferior cervical spine (from C3 to C7) is the most mobile segment of the whole spine. It is then exposed to an important dynamic loading. The maximal freedom of motion range occur at C5-C6 and C6-C7, which consequently are the most exposed to degenerative changes [34, 43]. The cervical disc is made up of an external annulus fibrosus and a central nucleus pulposus. The latter, while migrating through a fissure of the annulus fibrosus is responsible for the “soft” disc hernia, as it is made up only of disc material. This type of disc herniation can be due to disc degeneration secondary to hypermobility or it could be a result of trauma. The peculiarity of the cervical disc is that it is limited lateraly by the

Surgical Management of Cervical Disc Hernination

809

unco-vertebral joints, preventing its lateral migration and, the development of extraforaminal disc herniations. The thickness of the posterior longitudinal ligament and adhesion to the disc are maximal medialy region which accounts for the rarity of median disc herniation. The smooth cervical discs herniations are thus mainly in the paramedian, the foraminal, or the preforaminal position. So the soft disc herniation represents about 30% of all cervical discs herniations [11, 32] Hard disc herniation and osteophytes, occur secondarily to arthrosis of the cervical spine. Cervical arthrosis is an anatomo-radiological entity extremely frequent after 40 years. It becomes almost physiological with the process of aging. 90% of patients present with cervical osteoarthritis after the age of 80 years [34]. The calcifications of the edges of the discs enlarge, together with arthrosis of the uncus, are responsible for the development of a true osteophytic bar. This could cover theentire width of the disc, or could be found predominantly in the foraminal space. This is often associated with articular osteoarthritis. The physiology of the hard disc hernia is complex, and usually contributes to the diffuse cervical arthrosis. This could either be responsible for a compression of an isolated nerve root, or progressive spinal cord compression. The latter corresponds to myelopathic cervical arthrosis.

Clinical presentation Cervico-brachial neuralgia is a radicular pain of the upper limb, extending from the cervical spine to the hand, in a partial or complete way. It is secondary to irritation of a nerve root, more often by an unco-vertebral arthrosis, or less frequently by smooth lateral disc herniation. Clinically, radiculalgia is a permanent, piercing, increased by movement and maximal at night (the supine position increases venous stasis with accumulation of blood in the intervertebral foramina). This is more often unilateral. The patient can easily describe the trajectory of the pain. The pain originates from the postero-lateral aspect of the neck and descends towards the upper limb following a precise and metameric topography : - C5 : lateral surface of the shoulder and the arm, with sometimes posterior irritations towards the scapula. - C6 : antero-lateral surface of the shoulder, arm, fore-arm, and the thumb. - C7 : posterior surface of the shoulder, arm, and fore-arm, irradiating towards the dorsal face of the wrist and the medius (sometimes the index) - C8 : internal surface of the arm and the fore-arm, extending towards the little and the ring fingers. One should assess the motor deficit due to the nerve root involvement, also hypoesthesia or paresthesia, amyotrophy, absence of myotactic reflexes, and eventual Hoffman Sign associated with spinal cord involvement.

810 Spine

Fig. 1 dermatomes of cervical metameres.

Paraclinical investigations The role of imaging in the diagnosis of cervical disc herniation has been the theme of a general review by the ‘Agence National d’ Accreditation, et d’Evaluation en Sante’ (ANAES), in France [2]. MRI appears as the tool of choice in the investigation of disc and disco-radicular entrapments. Nevertheless, standards X-Rays (face, lateral, ¾ views) are useful in the initial work-up of cervical degenerative diseases. These will assess the level of osteophytosis and articular osteoarthritis. These X-Rays will also precise the curve of the cervical spine and assess the presence of one or more olistheses. Dynamic X-Rays exams are designed to assess the level of stability of the spine, specifically in cases of posttraumatic disc herniations. Because of its excellent bony definition, CT-scan is useful to distinguish between smooth and calcified hard disc herniations, and also for the study of the foraminal region.

Fig. 2 Left disc herniation C5-C6 (Images Dr P.A Faure)

Surgical Management of Cervical Disc Hernination

811

Electomyoneurogram is useful to assess radicular disfunction. The correlation between the electromyoneurogram and imaging are precious for the pre-surgical work-up in case of doubt especially when the discopathies involve many levels.

Therapeutic options 1) Medical treatment : Usually, the medical treatment consists of the use of analgesics, anti-inflammatory drugs, and myorelaxants, for a total period of about 3-4 weeks. The use of a soft cervical collar can significantly decrease the pain.

2) Treatment with interventional radiology : CT scan foraminal guided injections is indicated in case of foraminal disc herniation.

3) Surgical treatment Surgery only undertaken when a well conducted medical treatment is ineffective, though the latter usually shows good results with cervical disc herniation. There are two possible surgical approaches:

The posterior approach : Historically, the cervical spine was exposed initially using the posterior approach. In 1892, Horsley attempted to remove a cervical disc hernia using this method [39]. Mixter and Ayer were the first surgeons, in 1934, to report a study on eight cases of cervical disc hernia operated through the posterior approach using a simple decompressive laminectomy [20]. Later on, Frykholm, Spurling and Scoville will improve this technique to become a simple foraminotomy [33]. Although good results are observed in the resolution of pains [1, 10, 16], this posterior technique is no more than a simple decompression. During the years 1960-1970, many authors, especially Fager, improved this technique by the withdrawal of postero-lateral smooth cervical disc hernias, using this same approach [12, 13, 15]. From 1955, this technique has been progressively abandoned with the description of the antero-lateral approach developed by Robinson, Dereymaker and Cloward [8, 9, 28]. The disadvantage of the posterior approach was its morbidity. The large muscular detachment could be responsible for post-operative cervical pains, spinal cord injuries, cervical instability following facetectomy, potential muscular or epidural bleeding; and finally, the inability to treat all the types of cervical disc herniations contributed to decreasing interest in the use of this technique. The majority of authors therefore reserved the posterior technique in case of predictable operative difficulties through the anterior approach like short necks with dissection difficulties, post-operative or postradiotherapy tissue alterations, an oblique orientation of the last intervertebral spaces

812 Spine preventing their entry, and therefore, the removal of cervical disc. In the last years, the development of microsurgery and mini-invasive approaches of the spine has led to a regain of interest in this technique. The intervention can be performed in a ventral, or a sitting position. Using a tubular muscular retraction system, there is a possibility with a 3cm long incision to reach the spine in a transmuscular approach; hence without muscular detachment on the posterior cervical spine. Bone removal or bone drilling are thus minimised. Only the lateral part of the dural sheet, the peridural groove, and the nerve root in its first millimeters need to be exposed. There is no need to expose the posterior face of the dura mater, therefore preventing an eventual traumatic procedure on its surface. The drilling of the internal 1/3 of the articular process is not associated with post-operative instability. Raynor [25] has shown experimentally that post-operative spinal instability is obtained only after the removal of at least 50% of articular processes on both sides. With the drilling of 1/3 of the articular process, the nerve root is exposed from its armpit up to 5 mm distally. Removal of up to half of the articular process is rarely required. The principal advantage of this technique is the conservation of the intervertebral disc, the mobility of the cervical region without muscular lesion associated with high morbidity. Unfortunately, only the smooth cervical disc herniations in a postero-lateral position can be treated using this technique, the preforaminal variety in a position being the best indication.

A

B

Fig. 3 Illustration of the foraminotomy – facetectomy [15] A) Unilateral bony exposure of the lamina above and below and the internal half of the articular process. Generally approximately less than 1/2 of the inferior articular process and 1/3 of the superior articular process are drilled. B) The nerve root is delicately pushed upwards using a microdissector or a microspatula The herniated disc is removed at the radicular axilla using a disc punches.

Surgical Management of Cervical Disc Hernination

813

The antero-lateral approach : The history of the anterior approach started in 1928 with Stookey [35] who observed that an anterior access to the spine could be of great benefit for lesions localized in front of the spinal cord. Bailey and Badley in 1952 [3], Robinson and Smith in 1955 and Cloward in 1958 [8, 9] published several studies of anterior cervical discectomy with graft, for which the results were similar to those of the posterior approach., The report from the French-speaking neurosurgery society presented in France in 1970 by Verbiest led to the pre-sterno-cleido-mastoïdal antero-lateral pathway being increasingly applied for the entire range of pathologies of the cervical spine [6, 7]. It then became usual to use the antero-lateral pathway for most cervical disc herniations, whatever their consistency and their topography, by a simple discectomy followed with or without insertion of an interbody graft, with or without instrumentation. The results were gradually improved by the development of imaging, and the application of microsurgical techniques. Many published studies show up to 92% of excellent and good results [19, 22, 31]. This is, of course higher than the rate reported for lumbar disc herniation, with 80% of excellent and good results.

SURGICAL PROCEDURE: POSITIONING - Patient in supine position with upper limbs parallel to the body. Patient’s hair is protected with cap and eyes padded with gauze and closed with micro-pore. Hollow ring or doughnut pillow is placed beneath the occiput, rolled towel beneath the top of the shoulders for head and neck extension. Head kept in position with elastoplast. Neck kept straight or slightly rotated (10°) away from the side of the skin incision. Elevate head of the table (20°) to improve venous drainage. Shoulder traction using arm or wrist slings or elastoplast over the shoulders to expose lower vertebra for radiographical visualisation. Donor site for graft may be prepared on the iliac bone, ipsilateral to the neck incision. Radiographic localization of the level to be operated on using C-arm - Incision is marked on the anterior aspect of sternocleidomastoid muscles with coloured marker or needle. Covering of the image intensifier and human protection to radiation including the thyroid gland. Skin cleaned with an antiseptic solution. Towel positioned to expose just a rectangular area.Towel secured to skin with tap or stitches. Surgeon on the side of the incision. Assistant on the opposite side. Instrument nurse at the head of the patient. INFRA HYOID REGION APPROACH - Left sided approach. The side of the approach is determined by the : a) position of recurrent laryngeal nerve, b) location of the vertebral lesion. - Straight skin incision on the medial aspect of sternocleidomastoid muscle if more than two intervertebral discs need to be exposed. - Otherwise 4 to 6 cm transverse skin incision centered on the medial aspect of the sternocleidomastoid if accessing 2 adjacent vertebra - Haemostasis of subcutaneous vessels with bipolar coagulation. - Superficial fascia overlying the platysma muscle is dissected from superficial surface of the

814 Spine muscle avoiding injury to external jugular vein. - Dissection of platysma muscle layers parallel to its fibres. - Self-retaining retractor in place. - Blunt dissection of superficial aponeurosis. - Localization of carotid sheet by palpation of the internal carotid artery pulse under the anterior border of the sternocleidomastoid muscle. - Further blunt dissection with scissors to widen the interfascial plane between the prevertebral fascia overlying the spinal column, the attached musculature and the anteriorly located visceral fascia containing the oesophagus, trachea, and larynx. - A retractor; Farabeuf or Kocher is positioned to protect and keep the carotid in a lateral location. - Haemostasis of transverse veins. - Dissection of medium cervical aponeurosis. - Retractor in place displacing the oesophagus, trachea, and the larynx medially and the carotid and jugular vein laterally. - If necessary transection of omohyoid muscle and the superior thyroid artery (C4). - Dissection of deep cervical aponeurosis and prevertebral fascia (blunt or with scissors). - Exposure of anterior aspect of vertebral bodies between the longus colli muscles. - Superior and inferior aspect of vertebral bodies are dissected and haemostasis of following vessels ensured; a) Middle thyroid vein (C5). b) Inferior thyroid artery (C6 or C7) which can be retracted rostally or caudally (recurrent laryngeal nerve under the inferior thyroïd artery). c) Farabeuf venous trunks and collaterals. - Retraction with Cloward/Caspar retractors avoiding : i) Injury to the oesophagus. ii) Compression of the trachea (with risk of post operative tracheal swelling) or compression of the common carotid artery (with risk of circulatory arrest). - Bipolar haemostasis of pre-vertebral emissary veins. - Longitudinal incision of anterior vertebral ligament. - Dissection of anterior aspect of vertebra. - Haemostasis of vessels penetrating the anterolateral aspects of vertebral bodies with cauterisation or with Horsley bone wax. X-ray confirmation of the level. Positioning of microscope and DISCECTOMY

CLOSURE Drain in situ. Closure of platysma with resorbable separated sutures. Subcutaneous closure of skin.

Complications are rare. Dysphagia, and the recurrent nerve palsy are usually transient. Acute respiratory distress secondary to tracheal compression caused by a hematoma is exceptional, and can require an emergency tracheotomy. The perforation of the oesophagus or the thoracic lymphatic duct, as well as cervical sympathetic trunc trauma are not frequent.

Surgical Management of Cervical Disc Hernination

815

Fig. 4 Antero-lateral approach of the cervical spine. In Dechambenoit G, Kalangu K. Approaches for spinal surgery, Sauramps ed. with permission [44]

Interbody fusion The history of the anterior approach, from the beginning, has focused on the debate on the necessity to perform or not to perform an intervertebral fusion. In 1960, Hirsh [18] published the first study on anterior discectomies without graft, showing equal results compared to those using an intervertebral bone graft. According to many studies, the surgeons defending the technique of non fusion, showed that their results were similar to those using a bone graft. Till now there is no study that clearly demonstrates the superiority of the one technique over the other [4, 5, 22, 31, 37]. It was proven that the application of a bone graft increases the duration of operation, the length of hospitalization, the operative bleeding as well as post-operative pains. On the other hand it is believed that interbody fusion using autologous bone graftis associated with more complications (pains, bleeding, infections) at the level of the donor and the recipient sites. Nowadays these data should be juxtaposed again with the use of artificial bone grafts. Even though autologous bone grafts have been demonstrated to be better than artificial grafts in respect of achieving the fusion, the artificial grafts are demonstrated to reduce the complications associated with the use of iliac bone grafts.

816 Spine Concerning the advantages of the graft, some long term studies have shown the usefulness of the bone grafts in prevention of post-operative kyphosis due to narrowing of the intervertebral intervertebral space, associated with a potentiation of the degeneration process at the adjacent levels [3, 23, 25, 30]. Thus, the graft dimensions should be adequate in respect of compensating the height of the normal cervical intervertebral disc. The role of the “intervertebral spacers” in foraminal stenosis has been studied by Murphey [21]. In a randomized study authors demonstrate the advantage in terms of significant opening of the intervertebral foramens with the use of “intervertebral spacers” if compare to the opening achieved bu the use of intervertebral grafts. Furthermore the discectomy alone without graft interposition is responsible for a foraminal stenosis. However, no significant differences have been observed in the clinical results respecting the degree of foraminal opening demonstrated by the different studies relevant to this problem[21]. Anatomically, the foramen is initially large enough for the nerve root to pass through and consequently could tolerate an important secondary narrowing without clinical signs of root compression. Thus, the only objective advantage of bone grafting would be its role in long term prevention of spinal kyphosis. In general there are two main graft types used to substitute the excised intervertebral disk – either autologous bone graft or artificial graft. The grafts could be used either directly or in combination with different types of arthrodesis devices. The main advantage of the use of these devices is that they prevent the grafts from compaction, fractures and displacement. Another advantage is that it is possible to use an allograft instead of bone autograft, and thus reduce the chance of morbidity that is attributed to the iliac bone graft harvesting process. Because of its shape the arthrodesis devices cause no changes of the physiologic lordosis, as well as the possibility to maintain the adequate intervertebral height until the definitive intervertebral fusion is acheived. Finally, because of its “autostability”, the arthrodesis device does not need a postoperative rigid brace to facilitate the bone fusion of the graft. However, this characteristic needs to be weighted against the development of artificial grafts without arthrodesis device. Osteo-inductive ceramics have the advantage of a satisfactory bone growth toward the artificial graft, without any interposition of inert material like an arthrodesis device. These theoretical advantages however should be assessed on large studies, keeping in mind that these grafts seem to be less “autostable” than arthrodesis devices. In conclusion, regarding the grafting process, the use of an artificial graft enclosed in an autostable arthrodesis device seems to be the best option at present. More recently, cervical discs prosthesis were developed, based on the concept of cervical arthroplasty. This raised the hope that all the advantages of the “spacer” with or without its disavantages will be acheived. However, the physiologic stability and mobility of the normal intervertebral disc are difficult to be reproduced by the artificial disk prostheses at present. Although various implants are now available for use, their conception can be simplified as a double metallic plate articulated by a central mobile segment. This architecture is unable to fully mimic the intrinsic properties of the intervertebral disc. Even though different biomechanic studies show a good reproduction

Surgical Management of Cervical Disc Hernination

817

of the normal intervertebral mobility, the ability to absorb forces is far away from that of the normal disks. Furthermore it is now believed that the capacity of the prostheses to absorb forces in compression, is close to zero. Respecting the ability to support the vertebral body plates is also deficient since, the implant cannot mimic the intervertebral attachment realized by the solid fibers of the annulus fibrosus. Moreover, during the insertion of the prosthesis, the section of the powerful anterior common ligament, often together with the posterior common ligament is inevitable and contributes to a local instability. Respecting the normal physiology, it is important to conserve the spinal mobility at the intervertebral space following the discectomy process [14, 29]. The concept of cervical disc prosthesis is interesting; one can affirm that it has at least the same advantages as the arthrodesis device while preventing, in the short term, the inconvenience of an interbody fusion. Moreover, any surgeon used to cervical arthrodesis can insert cervical disc prosthesis without any additive morbidity from the surgical procedure. It is still difficult to evaluate the long term consequences of this new mobility induced by the prosthesis. Does it really prevents the adjacent level disc degeneration ? In addition, a certain number of cervical discs treated by arthroplasty fuse on short term.

Fig. 5 Dynamic X-rays after 6 months in a patient operated of three cervical discs hernias: double arthroplasty and an arthrodesis; conservation of cervical mobility. (Images Dr P.A Faure).

Conclusion The surgical management of cervical disc herniation should be considered only after a well conducted but ineffective medical treatment. The antero-lateral approach has been

818 Spine proven to be applicable to all the types of cervical disc herniations. However, the posterior approach still could be used in the treatment of postero-lateral soft disc hernia, procedure in which the cervical disc is conserved. Concerning the replacement of intervertebral disc following discectomy, it is still early to affirm that the arthroplasty is really superior to arthrodesis.

Surgical Management of Cervical Disc Hernination

819

Bibliography 1. ALDRICH F. Posterolateral microdiscectomy for cervical monoradiculopathy caused by posterolateral soft cervical disc sequestration. J Neurosurg 1990;72:370-377. 2. ANAES. [Place of Imaging in the diagnoses of Common cervicalgia, cervico-brachial nevralgia and chronic cervical myelopathy]. Rapport de l’ANAES. Decembrer 1998. 3. BAILEY RW, BADGLEY CE. Stabilization of the cervical spine by anterior fusion. J Bone Joint Surg (A) 1960;42:565-594.

820 Spine 4. BERTALANFFY H, EGGERT HR. Clinical long-term result of anterior discectomy without fusion for treatment of cervical radiculopathy and myelopathy : a follow- up of 164 cases. Acta Neurochir 1988;90:127-135. 5. BERTALANFFY H, EGGERT HR. Complications of anterior cervical discectomy without fusion in 450 consecutive patients. Acta Neurochir 1989;99:41-50. 6. BRUNON J, FUENTES JM, AZAN F, BENEZECH J, DUTHEL R, FOTSO MJ, GEORGE B, LAPRAS Ch, LESOIN F, ROBERT G. [Anterior and and antero-lateral surgery of the inferior cervical spine. (Twenty-five years after H.Verbiest). First part : basic technics]. Neurochirurgie 1996; 42:105-122. 7. CHESNUT RM, ABITBOL JJ, GARFIN SR. Surgical management of cervical radiculopathy. Indication, techniques, and results. Orthop Clin North Am, 1992;23:461474. 8. CLOWARD RB. The anterior approach for removal of ruptured cervical discs. J Neurosurgery 1958 ;15 :602-617. 9. CLOWARD RB. The anterior surgical approach to the cervical spine : the Cloward procedures. Past, present and future. Spine 1988 ;1 : 823-827. 10. DAVIS RA. A long-term outcome study of 170 surgically treated patients with compressive cervical radiculopathy. Surg Neurol 1996 ;46: 523-533. 11. DIETEMANN JL, [Imagery of cervicathrosic myelopathies. Degenerative cervical spine]. Cahiers d’enseignement de la SOFCOT n°48, 24-32. Paris, Expansion Scientifique Française, 1994. 12. FAGER CA. Posterolateral approach to ruptured median and paramedian cervical disk. Surg Neurol 1983;20: 443-452. 13. FAGER CA. Atlas of spinal surgery. Philadelphia : Lea & Febiger, 1989. 14. GAY E, PALOMBI O, ASHRAF A, CHIROSSEL JP. [The Bryan cervical prosthesis in the treatment of degenerative cervical affections, the case of a preliminary experience with 9 implants]. Neurochirurgie 2004;50 (6) : 624-629 15. HALLACQ P, MOREAU JJ, LAJOIX M, SAAIDIA K, VIDAL J, ALI BEN ALI M, MOUFID A, LAGARRIGUE JF. [Postero-lateral approach of soft discal hernias]. Neurochirurgie, 1999 ;45 :164-169. 16. HENDERSON CM, HENNESSY RG, SHUEY HM, SHACKELFORD EG. Posterolateral foraminotomy as an exclusive operative technique for cervical radiculopathy : a review of 846 consecutively operated cases. Neurosurgery 1983;13:504-512. 17. HERKOWITZ HN, KURZ LT, OVERHOLT DP. Surgical management of cervical soft disc herniation. A comparison between the anterior and posterior approach. Spine 1990;15:1026-1030. 18. HIRSCH C. Cervical disc rupture : diagnosis and therapy. Acta Orthop Scand 1960;3:172 186. 19. MARTINS AN. Anterior cervical discectomy with and without interbody bone graft. J Neurosurg 1976;44:290-295. 20. MIXTER WJ, BARR JS. Rupture of the intervertebral disc with involvement of the spinal canal. N Engl J Med 1934;211: 210-215. 21. MURPHEY F, SIMMONS JC, BRUNSON B. Surgical treatment of laterally ruptured cervical disc. Review of 648 cases, 1939-1972. J Neurosurg 1973 ; 38 : 679-683. 22. NOHRA G, ABI LAHOUD G, JABBOUR P, SALLOUM C, RIZK T, SAMAHA E, MOUSSA R, OKAIS N. [Anterior cervical discectomy with or without transplant in radicular conflicts. Long term results.] Neurochirurgie, 2003 ;49 °(6) : 571-578 23. PERRIN G, PIERRON D, LAZENNEC J.Y, ROBERT G. [Cervical discal hernia]. Actualités vertébrales. n°2, avril 1994. Edition Edimedica. 24. POINTILLART V. Cervical disc prosthesis in humans: first failure. Spine 2001; 26: E90 E92.

Surgical Management of Cervical Disc Hernination

821

25. POINTILLART V, PEDRAM M, CARLIER Y, VITAL J. Outcome of cervical spinal levels adjacent to anterior fusion: long-term follow-up (communication). Congrès de la Cervical Spine Research Society, Paris, 2002. 26. RAYNOR RB. Anterior or posterior approach to the cervical spine : an anatomical and radiographic evaluation and comparison. Neurosurgery 1983 ; 12 : 7-13. 27. RAYNOR RB, PUGH J, SHAPIRO I. Cervical facetectomy and its effect on spine strength. J Neurosurg 1985;63: 278-282. 28. ROBINSON RA, SMITH GW. Anterolateral cervical disc removal and interbody fusion for cervical disc syndrome. Bull Johns Hopkins Hosp 1955;96: 223-224. 29. ROBERTSON JT, PAPADOPOULOS SM, TRAYNELIS VC. Assessment of adjacentsegment disease in patients treated with cervical fusion or arthroplasty: a prospective 2year study. J Neurosurg Spine 2005: 417-423 30. ROBINSON RA, WALKER AE, FERLIC DC, WIECKLING DK. The results of anterior interbody fusion of the cervical spine. J Bone Joint Surg (A) 1962;44:1569-1587. 31. ROSENORN J, HANSEN EB, ROSENORN MA. Anterior cervical discectomy with and without fusion. A prospective study. J Neurosurg 1983; 59 : 252-255. 32. ROY-CAMILLE R, [Inferior cervical spine]. VIèmes journées d’orthopédie de la Pitié. Paris, Masson, 1988. 33. SCOVILLE WB, DOHRMANN GJ, CORKILL G. Late results of cervical disc surgery. J Neurosurg 1976;45:203-210. 34. SIMON L, BLOTMAN F, CLAUSTRE J, HERISSON C. Abrégé de Rhumatologie. Masson 1989. 5ème édition. 35. STOOKY G. Compression of the spinal cord due to ventral extradural cervical chondroma. Diagnosis and surgical treatment. Arch Neurol Psychiatr 1928;20:275279. 36. WIGFIELD C, GILL S, NELSON R, LANGDON I, METCALF N, ROBERTSON J. Influence of an artificial cervical joint compared with fusion on adjacent-level motion in the treatment of degenerative cervical disc disease. J Neurosurg 2002;96:17-21. 37. YAMAMOTO I, IKEDA A, SHIBUYA N, TSUGANE R, SATO O. Clinical long-term results of anterior discectomy without interbody fusion for cervical disc disease. Spine 1991;16:272-279. 38. YAEGER VL, Cooper MH: Surgical anatomy of the cervical spine and surrounding structures. Young PH editions: Microsurgey of the cervical spine, New York, 1991, 1-17. 39. HORSLEY V. The results of operative treatment of injury or disease of the cervical vertebrae. Lancet 1895;2:437 40. WAINNER RS, GILL H Diagnosis and non-operative management of cervical radiculopathy. J Orthop Sports Phys Ther 2000;30:728–44 41. SALEMI G, SAVETTIERI G, MENEGHINI F, DI BENEDETTO ME, RAGONESE P, MORGANTE L, REGGIO A, PATTI F, GRIGOLETTO F, DI PERRI Prevalence of cervical spondylotic radiculopathy: a door-to-door survey in a Sicilian municipality. Acta Neurol Scand 1996;93:184–8 42. RADHAKRISHNAN K, LITCHY WJ, O’FALLON WM, KURLAND LT Epidemiology of cervical radiculopathy. A population-based study from Rochester, Minnesota, 1976 through 1990. Brain 1994;117(2):325–35 43. KAPANDJI I.A. Physiologie articulaire du tronc et du rachis. Maloine 1999. 44. DECHAMBENOIT G, KALANGU K. Approaches for spinal surgery. 148p, 2007, Sauramps ed.

822

Cervical Spine Injuries BERNARD IRTHUM Professor Head of the Department of Neurosurgery University hospital of Clermont-Ferrand FRANCE Key words: cervical, spine, fracture, spinal cord injury, SCIWORA

INTRODUCTION Spinal fractures occur in various civil activities, predominantly during road traffic accidents in occidental countries; industrial injuries are less frequent due to preventive actions whereas leisure injuries are presently at an increase (mountaineering, skiing, paragliding…). The frequency of severe spinal cord lesions is usually between 14 and 30% of spinal trauma, resulting from various discal and ligamentary lesions, vertebral fractures and also spinal instability. Emergency management of spinal injuries can reduce a secondary displacement of instable lesions capable of increasing the severity of spinal cord lesions and can as well lead to the improvement of spinal deficits if the spinal cord is freed from any compression and the spine reinforced with stable osteosynthesis. Spine injury occurring frequently without any other parenchymal lesion is easily assessed and managed, but its association with other severe traumas (brain, abdomen, thorax, limbs) can lead to misdiagnosis because spinal cord deficits can be masked by other lesions.

EPIDEMIOLOGY Frequency: influence of age, civil practice, and spinal level Children are less frequently injured than adults (2% of all spinal injuries); elderly people are exposed to lots of spinal injuries due to minor falls resulting from loss of one’s balance in common situations (stairs, gliding floors, falling from a stepladder). Acute severe alcoholic ingestion promotes this kind of trauma.

Circumstances of trauma More than 50% of spinal traumas occur during road traffic accidents (cycling, motorcycling, and car driving…) during which falling on the ground and getting thrown out of the mobile in displacement are associated with acute deceleration to create lesions. Industrial injuries consist of falling from a height (building industries) and in agricultural activities falling of high weights on the head and neck (hay and straw bales).

Cervical Spine Injuries

823

Some sports are more frequently concerned like rugby (violent engagement in a scrum and tackle), horse riding (falling when horse is galloping), skiing (high speed falls, impact with an obstacle), hang gliding and paragliding. Diving in shallow water (rivers or swimming pools) is the most frequent leisure spinal trauma. At present, there is an annual incidence of 1000 cases of spinal cord trauma in France, including 45% road traffic accident and 30% industrial injuries. Sex ratio is 70% male to 30% female. Median of age is 30.

TYPE OF SPINAL TRAUMA AND BIOMECHANICAL ASPECTS Different kind of forces Forces occurring in the genesis of these spinal lesions can be oriented along 3 spatial axes: - vertical axis going along the posterior wall of vertebrae, along with compression and distraction forces and around which rotation forces are acting, - horizontal axis in sagittal plane (AP), along with translation or shearing forces and around which tilting forces are acting, - horizontal axis in frontal plane, along with lateral translation forces, and around which flexion-extension forces are acting. There are mainly two mechanisms creating spinal fractures and luxation: the former is compression mechanism injuring vertebral soma and the latter is a shearing or AP translation mechanism creating injuries of mobile segment (vertebral disc, ligaments and facet joints). These two mechanisms can be isolated or associated creating a variety of spinal lesions.

Spinal biomechanics and spinal stability. Constraints observed in a spine during standing posture are shared in two directions: one is through the vertebral body and discal column and receives 82% of the forces, and the other, the two facet joints columns receive 18% of the forces. These facet joints columns can absorb from 0 to 33% of the forces depending on the posture of spine, the maximum of constraints occurring in the lordotic posture. The middle vertebral segment (posterior wall of vertebral body, pedicles and joint facets) is the most resistant part of the vertebra and receives the major part of the constraints whatever the posture of the spine. The anterior part of the column of vertebral bodies and discs is able to endure a kind of deformation because of tolerance of compression forces. This stability of anterior column of the spine (bodies and discs) is reinforced by the posterior longitudinal ligament, and the ligament flavum to a lesser extent in flexion posture of the spine. The intrinsic muscles inserted on the spinous and transverse processes and the extrinsic muscles of thoracic and abdominal parts of the trunk also play a role in the stability of the spine. Stability of the spine is assessed by the integrity of vertical bony columns and horizontal bridges such as pedicles: the integrity of two vertical columns or one vertical

824 Spine column and two horizontal bridges is mandatory to get spinal stability. In a case of spinal trauma the respect of middle vertebral segment secures the stability of the spine.

Vulnerability of vertebral junctions The cranio-cervical junction is stressed by forces consisting of the weight of the head and kinetic energy acquired in the movement of the head during acute deceleration and whiplash injuries.

PATHOLOGY OF ELEMENTARY SPINAL AND SPINAL CORD LESIONS Upper cervical spine. 1-Occipital condyles fractures: frequently unilateral and associated with lesions of atlas and axis; they are classified according to ANDERSON and MONTESANO in 3 types: 1=comminutive fracture, 2= basilar fracture extended to the condyle, 3= avulsion of the condyle. They are noticed in a context of cranial trauma with impairment of consciousness and lesions of lower intra cranial nerves. 2-Occipito atlantal luxation: rare, often fatal, with anterior or posterior or longitudinal along axis of cervical spine; associated with severe medullar and lower cranial nerve impairment. 3-Axoido atlantal luxation : more frequent in childhood (age less than 13 years) than in adulthood , classified by FIELDING and HAWKINS in 4 types. Type 1 is a rotatory luxation around the dens, type 2 is a rotatory luxation around a lateral articular process; these lesions can be observed after benign traumas during sports, constituting the main aetiology of cervical stiff neck in childhood. Type 3 is an anterior bilateral luxation with transverse ligament lesion of C1, type 4 is a posterior luxation associated with dens hypoplasia. These two types are produced by AP translation forces of high energy. 4-C1 fractures: these compression fractures induce burst of C1 ring; they are classified by LANDELLS in type1= isolated fracture of anterior or posterior arch, type 2= both arch fractures (Jefferson), type 3= burst fracture of a lateral process. Anterior displacement of C1 results from the tear of the transverse ligament of C1; these lesions are classified by DICKMANN in two groups according to MRI data, one is a pure ligament lesion, the other is a partial bone detachment of lateral process. AP X rays of C1 can indicate this tear of the transverse ligament if the displacement of the lateral process of C1 in relation to the articular process of C2 is greater than 7 mm (SPENCE rule). 5-Dens fractures: resulting from translation or shearing forces, they are classified according ANDERSON and D’ALONZO as type1= tip fracture of dens, type 2= base fracture of dens, type 2A= base fracture and burst of dens, type 3= dens fracture extended to body of C2. Displacement is produced by obliquity of fracture line and can be explained by ligament and capsular lesions of the articular process joining C1 and C2. Anterior and down oblique fractures lead to anterior displacement, posterior and down fractures lead to posterior displacement.

Cervical Spine Injuries

825

6-Posterior arch of C2 fractures: often resulting from an extreme extension and distraction stress (hangman’s fracture); they can also be produced by an extreme flexion stress. EFFENDI classified these fractures in type1= isolated fracture of posterior arch without disc lesion (mechanism of extreme extension and compression along axis of the spine), type 2= fracture associated with disc lesion and anterior displacement (extreme extension and consecutive flexion stress), type 3= fracture with disc lesion and flexion angulations of C2 body in relation to C3 (extreme flexion and consecutive extension stress). 7-Complex fractures of C2 and associated lesions: body fractures are difficult to be classified; the main line of fracture is most suitable to use for their classification. Burst fracture can be observed in association with C2C3 disc lesion. Association of lesions: C1 fractures are seen in 25 to 50% cases with dens fracture; posterior arch fractures of C2 are seen in 6 to 25% of cases with C1 fracture. In these associated lesions neurological impairment and mortality is increased to 80%.

Sub axial cervical spine C3 C7 1-Benign and severe sprains: a cervical sprain results generally from a whiplash injury producing lesions of ligament and disc; the joint between two cervical vertebrae. Benign sprain is very frequent and usually respects the integrity of posterior longitudinal ligament. The Posterior inter spinous ligament, flavum ligament, articular ligament, and sometimes in extreme extension mechanisms the anterior longitudinal ligament can be torn. These lesions cannot induce instability. Severe sprain induce instability and can lead to luxation. In this case there is also a rupture of posterior part of disc and a tear of posterior longitudinal ligament. One can see on AP X ray an anomaly, sometimes only demonstrated by dynamic flexion extension X rays. Radiological criteria are antelisthesis of more than 3.5 mm between the posterior wall of two adjacent vertebrae and angulation greater than 11° between the vertebral plates in comparison with the adjacent normal discs. 2-Luxation and fracture- luxation of articular process: these uni or bilateral lesions of the posterior articular processes produce a complete loss of union between the articular processes; the superior articular process is displaced in front of the inferior articular process, sometimes fractured on its tip or completely separated by a double pedicular and laminar fracture. A disc lesion, and a longitudinal anterior and posterior ligaments tear is observed and complete the criteria of instability. These lesions result from shearing and rotatory mechanisms and are considered like unstable. 3-Body fractures: compression or burst of vertebral bodies result from compression mechanism; some severe fractures can displace a bony fragment into the spinal canal. 4-Tear drop fracture: they result from a double mechanism of shearing and compression; this kind of fracture induces instability due to severe discal and ligamentous lesions generally under laying the so called tear drop anterior marginal fracture of body. Spinal cord injury without radiographic abnormality(Sciwora): most often seen in paediatric cases, this situation can be explained by severe and acute elongation of spinal cord whose structure could be less flexible than cervical and cervico-thoracic spine. In

826 Spine some cases a complete neurological deficit is observed with a bad long term outcome. In some other cases an initial incomplete deficit may be completed in the subsequent days. NMR study of spine generally doesn’t show any bony lesion, but in some cases one can see discal and cartilaginous lesions. Spinal cord lesions are classified according three increasing grades of gravity: 1-Spinal cord concussion is a functional state in which the cord has a normal aspect macroscopically; microscopic lesions are moderate only consisting of micro haemorrhagic foci or interstitial oedema 2-Spinal cord contusion is an anatomic impairment in which the cord appears oedematous in macroscopic examination, with ecchymotic foci on its surface; microscopically one can see larger foci of micro haemorrhage and ischemic lesions; dura mater is always intact. 3-Spinal cord attrition includes macroscopic pial tears and extrusion of necrotic and oedematous tissue; the most severe aspect is spinal cord section. Dura mater is most often partially opened. 4-Evolution of spinal cord lesions -spinal cord lesions can be impaired in the days following trauma due to extension of micro haemorrhage foci and infarcts by a second biological injury with increase of oedema. -1 month later, gliosis is noticed as a repair mechanism of spinal cord lesions; in some rare cases, a central syringomyelia is observed. -arachnoïditis can increase the risk of evolution to syringomyelia, sometime a long time after trauma (many years) 5-Radicular lesions: spinal root avulsion or incorporation of spinal roots in posterior arch fractures can be encountered with spinal cord lesions.

CLINICAL EXAMINATION Traumatic spinal lesions are often associated with limb lesions, thoracic injury, and brain trauma. An initial clinical examination is necessitated to precise the checking of all lesions to define a strategy for the management of all lesions with the best chance for vital and neurological outcome.

General clinical status and associated lesions (brain, limbs,) It is common to say that all cases of head trauma are suspected to have also a neck injury, because of the amount of kinetic energy of head in acute deceleration trauma. In these cases it is impossible to assess the spine injury signs because the patient is comatose; in these cases the radiological examination is mandatory to check the absence of bony spinal lesion. Ligamentary lesions are to be checked later if clinical signs indicate a spinal cord lesion after the awakening of the patient. Limb lesions can induce a functional impairment due to pain and simulate a neurological deficit; they can also be associated with nerve and plexus injuries which are normally different from a clinical point of view from cord or radicular lesions (only one

Cervical Spine Injuries

827

limb affected with sensitive and motor impairment on the same territory) Thoracic lesions (haemothorax and pneumothorax) and abdominal lesions (intra peritoneal haemorrhage) may induce cardiocirculatory and respiratory severe impairment justifying an emergency reanimation , and sometimes an operation ; in these cases the knowledge of spinal column lesions in this patient needs strict measures for manipulation of the patient preventing a neurological impairment. Generally severe neurological deficit like tetraplegia is associated with vasoplegia and collapse which necessitates usage of vasopressive drugs and vascular filling.

Spine examination Spontaneous localized pain or pain triggered by slight movement are the main symptoms with para spinal muscle cramp. Examination of a patient in the recumbent position permits a gentle palpation of spinous processes, and can localize an elective painful vertebra that can orientate the execution of plain X Rays. In some instances patient consult a long time after trauma and present at this time a static anomaly of the spine such as anterior or lateral bending which is commonly an analgesic attitude, with a para spinal muscle cramp. Cranio cervical joint lesions are frequently associated with a torticollis and flexion rotation attitude of the neck evident in children.

Neurological and sphincters examination. Initial neurological examination must be done precisely and systematically to assess if the spinal cord function is completely loss; it is important to recognize an incomplete lesion which is is capable of recovering, but can also be impaired if an unstable spinal lesion is mobilized. Motor, sensitive, and sphincter functions are analysed according the schematic examination proposed by the ASIA (American spine injury association, electronic address www.asia-spinalinjury.org/publications ). The level of cord injury is defined as the first impaired spinal cord level. 1-complete tetraplegia At the beginning the motor deficit is complete, with flaccidity, hypotonia, and abolition of tendinous reflexes in the paralysed limbs. Later, after an interval of 3 or 4 weeks tendinous reflexes appears again signing the end of spinal shock .Anaesthesia is complete(proprioceptive=posterior bundles and thermalgesia= spinothalamic tract) under the level of cord lesion, fitting with the motor deficit. Anal sphincter is hypo tonic verified by digital rectal examination. Priapism is frequently seen in man; there is urinary retention and bladder catheterism is mandatory. Intestinal transit is stopped resulting in constipation and abdominal distension in the days following paraplegia. 2-incomplete tetraplegia Several clinical presentations may be seen with association of more or less systematized lesions of spinal cord. Brown Sequard syndrome is the most commonly known, resulting from hemisection of the spinal cord, associating motor paralysis and sensitive

828 Spine proprioceptive anesthesia on the side of cord lesion, and contra lateral thermalgesia below the level of the cord lesion. Several incomplete lesions consist of bilateral impairment of motor and sensory function: in anterior lesions of cord one can observe the sparing of proprioceptive sensation, asymmetry of lesions is frequently seen in incomplete lesions of cord. Central spinal cord lesion (Schneider’s syndrome) associate isolated brachial diplegia sometimes worsened with incomplete paraplegia. In these cases sphincter disturbance is less severe.

COMPLEMENTARY INVESTIGATIONS X rays- CT scanner The choice of the initial X-ray examination will be a function of the patient’s clinical state; if comatose, the Plane X-ray or the CT scan of the entire spine will be mandatory and oriented examination done to check for abnormalities. AP and lateral views and sometimes oblique views and specific views (open mouth X ray for dens fractures) can assess osseous and ligamentary lesions; dynamic views with flexion and extension of spine are mandatory to check cervical ligamentary lesions, but they must be delayed for one or two weeks . CT scanner supersedes plain X rays in most of cases at present, permitting an examination of thoracic and abdominal lesions. Axial slices assess the somatic and posterior arch lesions, and also the rare traumatic disc herniation; with this examination the spinal canal is checked in the best way. Sagittal reconstructions are useful to see the posterior wall of vertebral bodies and the piling up of articular processes.

NMR (Nuclear Magnetic Resonance) This examination is rarely performed in emergency, but it is mandatory in case of normal bone examination with X rays or CT scanner, and severe clinical spinal cord impairment. It may reveal an epidural haematoma, or a myelomalacia in case of trauma concerning narrowed cervical canal. In children with SCIWORA (spinal cord injury without radiological abnormality) one can see severe cord lesions with complete section of cord and ligamentary lesions, but in some cases the examination may be normal.

Electro physiology Electromyography is of no interest in emergency case, but it may give information concerning the level and severity of radicular lesions, especially in cervical and lumbar lesions. Sensory and motor evoked potentials may be useful in the period of recovery to check the neurological evolution, preceding the clinical improvement. Signs of retardated spinal cord influx are seen with dissociated waves.

Cervical Spine Injuries

829

TREATMENT Medical care Patients with tetraplegia need very attentive nursing to prevent in the early hours complications of such a severe neurological deficit as paraplegia. Nursing care is fundamental with necessity of mobilizing gently these fragile patients without any risk of aggravation; they also have psychological alterations due to the severity of handicap. Medical therapies have been evaluated at the acute phase of traumatic spinal cord lesions, such as corticosteroids; but results of these trials are non convincing with regards to recovery of autonomy, and more over they induce an increasing risk of iatrogenic infections. So that most of medical personnel have abandoned these treatment. Trials are done to assess the benefit of decompression of spinal cord and spine stabilization in the delay of first six hours following the injury.

Orthopedic and functional treatment Most of spine lesions are stable and don’t threaten the neural component inside the spine. Functional care including analgesic therapy, early standing up, physiotherapy against pain and spasms are indicated in minor cervical ligamentary lesions such as benign sprains or spinous and transverse processes fractures; some compression vertebral fractures which concern a small part of the vertebral plate may be treated in the same way. Orthopedic treatment with immobilization in plastic or plaster surgical corset (cervical brace with support on sternum and chin for cervical lesions, cervical brace descending on thorax reaching umbilicus for cervico-thoracic joint lesions. This kind of immobilization must be worn for three months-the mean delay for consolidation of vertebral fractures .Dens fracture may need a longer immobilization, after checking the fusion with CT scanner or X rays. Physiotherapy with isostatic contractions to reinforce para-spinal muscles is indicated as long as pain has been attenuated.

Surgical treatment Surgical treatment of vertebral fractures is at present well codified and has evolved in its indications as comprehension of mechanisms creating the different lesions has been acquired. Technical improvement concerning the osteosynthesis equipment permits realization of stable assembly at every level of spine. 1-General principles: Reduction of displaced lesions must be done as quickly as possible by cranial traction with a Gardner stirrup for cervical lesions. Operative control with radioscopy is mandatory to verify operative reduction on operating table, and accuracy of osteosynthesis. Anterior approach is performed for most of cervical lesions, except for dens fractures with anterior displacement and oblique anterior line of fracture, and for ligamentary

830 Spine unstable lesions of cranio cervical junction. Double approach is very rarely realized. 2- Operative indications What kind of patients to be operated? General status is certainly the main limiting factor for surgery; in each case temporary contra indications will be discussed (cardio vascular or respiratory deficiencies such as pleural collection, platelet count under 100000 and disturbed prothrombin factor, necessity of emergency operation for intracranial haematoma, hemostasis of intra peritoneal bleeding, embolization of hemorragic lesion…). In some cases there is a definitive contra indication for surgery because the general status is so bad that anesthesia or surgery would threaten life. One must have in mind that preservation of neurological function doesn’t prevail over vital risk; in some cases orthopedic and functional treatment alone are to be considered. When operation must be performed? Spinal lesions without neurological impairment may be scheduled without emergency, provided that the neurological status of the patient is regularly checked and an unstable lesion is immobilized (cranial traction or cervical brace for cervical lesions which are the most mobile); this point is debatable and is a function of the availability of a trained surgical team in every hospital. Spinal fractures with neurological impairment may be operated on within a six hours delay if possible, whatever the neurological deficit is. Spinal lesions with a neurological deficit previously delayed for operation may be operated as soon as the cause of this delay has been corrected (improvement of vital parameter or operation for an emergency with post operative stabilization of general status) Who may operate? Spinal injured patients may preferably be catered for by a multi disciplinary team of trained medical doctors, with availability of all techniques of medical imaging and an intensive care unit. If a vital emergency needs to be cured in a local hospital within the vicinity of accident without availability of a surgical team trained to do spinal surgery, the patient must be secondarily referred as soon as possible in a medical center specialized in spine surgery to perform operation in case of neurological deficit. What kind of operation? The experience of surgeon may authorize some variations of techniques, but the main principles are to perform an early reduction of displaced lesions, a decompression of neural elements in the spinal canal, hemostasis, and then a definitive stabilization of lesions. Superior cervical spine (condyles, C1-C2) A temporary cranial traction may reduce displaced lesions, but a radiological verification is needed before persisting in doing this way.If reduction is not acquired with cranial traction, an operative reduction is mandatory and must be followed immediately by stabilization. In the surgical positioning of the patient (prone or supine position) on the operating table the fixation of head in a skull clamp protects from risk of mobilization or displacement of unstable lesion previously reduced with cranial traction and from

Cervical Spine Injuries

831

ocular compression in prone position. A radioscopy must verify the spine alignment after positioning the patient. An anterior approach is indicated for isthmic fractures of C2 with lesion of C2C3 disc (arthrodesis with autologous bone graft or substitute and anterior plate screwed in C2 and C3) and dens fractures with horizontal or oblique posterior line of fracture (screwing of dens). A posterior approach is indicated for occipito atlantal luxations, C1C2 luxations, dens fractures with oblique anterior line of fracture, posterior arch fractures of C2 with fragments depressed in spinal canal. Different types of posterior metallic fixation are now available, used with or without bone graft, preserving if possible the motility of occipito vertebral junction. Double approach is rarely done, only indicated if a first approach is not sufficient for stabilization of fracture. Complex lesions may be treated by prolonged cranial traction followed by immobilization with cervical brace or halo-vest. Sub axial cervical spine C3-C7 or T1 Anterior approach is mainly used after anatomical reduction with cranial traction or manual reduction in anesthetized patient on operating table with immediate radioscopic control. The fixation of head with head clamp is preferable because it gives an excellent head fixation after reduction. If this is not possible, the use of a horse shoe head rest is desirable. A radioscopy is mandatory to verify the permanence of reduction after installation. Decompression of spinal canal concern one disc or one vertebral body and the two adjacent discs; arthrodesis is performed with bone graft or a bone substitute if the lesion concern only one disc. Stabilization is given with a plate screwed on the anterior part of the normal adjacent vertebral bodies. In some cases posterior approach is better for decompression of posterior arch elements depressed into the spinal canal; the patient is then installed in a prone position and cervical plates are fixed bilaterally in articular processes. Double approach is very rarely done in emergency cases but sometimes may be indicated if a simple approach has not provided a complete decompression of neural elements. 3- Criteria for operation First eliminate a lesion threatening life, which needs an emergency operation such as, laparotomy or thoracotomy for hemostasis, craniotomy for evacuation of an intracranial hematoma, opened limb fracture with large septic contamination. Operative installation of a spine injured patient may need primary fixation or traction for limb or pelvic fracture due to the risk of displacement during turning of the patient. In these cases a biological check may verify that hemoglobin rate and coagulation factors are correct before starting spine operation. Provide a good respiratory function: drainage of intra pleural collections such as pneumothorax and hemothorax, but anterior placement of a thoracic drain is contra

832 Spine indicated if prone position is mandatory for spine operation due to the risk of occlusion of drain when turning the patient. Small intra pleural collections may be tolerated if a close watch over the patient is done. Provide a hemodynamic stability: intravascular filling according to bleeding, and use of vasopressive drugs in case of vasoplegia. Curing biological perturbations, such as anemia , haemostatic factors alteration with the aim of getting an hemoglobin value > 10g/dl, platelet count > 100 000/mm3, and coagulation cofactors>50%. As coagulation is a dynamic phenomenon, the need for blood transfusion during operation must be anticipated. Eliminate an absolute contra indication: there are few lesions that indicate emergency surgery at the acute phase of poly traumatism : brain trauma with CT scanner identified lesions of parenchyma needs intra cranial pressure monitoring ;in case of stable hemodynamic and respiratory condition , if there is no threatening intra cranial hypertension a spine operation for osteosynthesis is possible. 4- Prevention of operative field infection. Common rule of prophylactic antibiotic therapy fit to spine surgery with the following protocol:

Functional rehabilitation of spinal cord injured patients Generally done in rehabilitation centers specialized in para and tetraplegia; the aim is to get the patient recover the best autonomy permitting a normal social life. If walking is not possible the use of a wheel chair is rapidly done, and initiation to transfers from wheel chair to bed and into a car is the main objective. The education of the paraplegic patient concerning the sphincter functioning may

Cervical Spine Injuries

833

allow to start a reflex micturition , otherwise the self catheterization of bladder may be teach . The main problem concern the tetraplegic patient in which the upper level of motility may not allow transfers from wheel chair to bed; in some cases operation for reinnervation of muscles such as neurotization or muscles transfer may be done. The follow up of paraplegic patients is generally assumed by several medical specialists such as neurosurgeon, urologist, orthopedist, physiotherapist, which will act together to prevent the complications of paraplegia or tetraplegia.

EVOLUTION Clinical evolution Neurological recovery depends on the intensity of initial lesions and the level of injury: schematically, incomplete lesions of spinal cord have a better prognosis, but have sometimes a bad recovery when initial lesion concern mainly motor and spinothalamic tract with respect only of the posterior bundles of cord. If there is a persistence of function of spinothalamic tract the motor recovery would be better due to the anatomical vicinity of motor tract and spinothalamic tract with the same blood supply. Incomplete cervical spinal cord lesions have a good prognosis with sometimes near complete recovery of function. The recovery to a motor status below 3 (ability of movement without gravidity) is not sufficient for the patient to stand up, but it permits to protect from cutaneous complications. Recovery of one or two spinal metameric levels may be fundamental for allowing a better quality of life in a tetraplegic patient who can transfer himself from a wheelchair to bed (recovery of triceps brachii function). Complications may be observed in a tetraplegic patient due to the immobility of limbs: -phlebitis of inferior limbs and pulmonary embolism may be prevented with anticoagulant therapy, early passive mobilization, and support stockings. -bedsores concerning the pressure points on skin may be prevented with alternating position of body changed every two hours, confinement on water mattress or other device preventing the chronic pressure on skin . In case of a sitting, position the patient may regularly lift up himself and use of a gelatin cushion is recommended. -urinary tract infection may be prevented with intermittent catheterization of bladder, which after the initial period of permanent catheterization mandatory during the phase of spinal cord shock, will provide a bladder vacuity without urine stagnation. -high calcium level in the urine due to loss of bone calcium may induce urinary tract lithiasis, and may be prevented with high level diuresis. -osteoporosis due to immobilization of patients may rarely lead to spontaneous fractures of limbs; it may be prevented by early mobilization and standing up. -neurogenic para osteo arthropathies may be constituted in the weeks following a spinal cord lesion mainly with complete neurological deficit, affecting the large joints of inferior limbs; these joint appears swollen, warm , and reddish in the acute phase and secondarily they change to the aspect of calcified tough lesions that stiffen the joints. Prevention is made of avoidance of mild trauma concerning these joints during

834 Spine rehabilitation, and gentle physiotherapy for maintaining motility of joints. -Syringomyelia is seldom observed in the evolution of spinal cord trauma; generally it is constituted after many years of evolution, observed in patients who aggravate their neurological status with weakness and spasmodicity, sphincter disturbance, and sometimes a typical suspended sensitive thermal and pain deficit. NMR study shows a central spinal cord cavity in a atrophic spinal cord resulting of the old traumatic lesion. Treatment may need drainage of the central spinal cord cavity to sub arachnoid space or peritoneal cavity.

Orthopedic complications Spinal pain Persistent and retractable pain indicate sometimes the existence of pseudoarthrosis which may be verified on X rays if there is an abnormal mobility of the fracture focus. The occurrence of that complication warrants the maintenance of immobilization in a collar brace or in some cases to operate for bone grafting of the fracture focus, choosing an anterior approach if the patient had been operated previously by a posterior route for osteosynthesis. Abnormal callus Kyphosis is tolerated if there is an angle 50 %): In the posterolateral fusion group:Examining the great displacement, these cases require an extended posterior osteosynthesis (L3-S1) and postero-lateral autogenous arthrodesis. A trans sacrolumbar screwing can be added during the posterior approach (fig 15, 16, 17, 18). In the anterior group the anteroinferior edge of L5 is resected if necessary to obtain better access to the presacral intervertebral disc space (fig 19, 20, 21, 22). Circumferential fusion group can be offer. The two fusions are realized in single session or after an interval of 2 to 3 weeks.

898 Spine

Fig. 15 Spondylolisthesis

Fig. 16 Posterior stabilization

Fig. 17 Anterior approach

Fig. 18 Final Result

Fig. 19 Posterior stabilization

Fig. 20 Anterior screwing

Isthmic Spondylolisthesis in Adults Surgical Treatment

Fig. 21 Posterior screwing

Fig. 22 Double approach

Fig. 23 Spondylolisthesis

Fig. 24 Posterior stabilizatio

899

Fig. 25 Anterior plating Fig. 26 TDM reconstruction

The circumferential fusion provider better clinical (Oswestry Disability Index) and radiographic outcomes (fig 23, 24, 25, 26) than did posterolateral or anterior fusion for high-grade spondylolisthesis, but the differences in MRI analysis are smaller.

900 Spine Degenerative disc changes were most commonly found in the posterolateral fusion group and at the level of the L3-L4 or L4-L5 intervertebral discs in all subgroups. The spinal canal is wide and however 28 % of the patients had a severe narrowing of the neural foramen. Longer fusion and muscle degeneration, but not disc degeneration, were associated with lower performance in spinal mobility and trunk-strength measurement tests.

Grade 4: In these cases many investigators recommended the posterior fusion in-situ, performed from L4 to S1 (19). An other part of authors achieve this goal by combined reduction and stabilization. Some one try to reduce and stabilize the spine by a posterior approach with L4 screwing (Ruf, 17)

Grade 5: A posterior approach with a two or more levels osteosynthesis with a posterolateral arthrodesis and an anterior approach with total removal of L5 can be proposed. Stiff, irreductible spondylolisthesis was treated with L5 resection, as described by Gaines and Nichols and Lehmer et al (6, 12).

CONCLUSION Surgery of the spondylolisthesis is a good exemple of the opportunity of clear indications and good competence.

ALGORITHM

Isthmic Spondylolisthesis in Adults Surgical Treatment

901

REFERENCES 1. Brantigan JW, Steffee AD. A carbon fiber implant to aid interbody lumbar fusion: Two year Clinical results in the first 26 patients. Spine 1993;18:2016-17. 2. Buck JE. Direct repair of the defect in spondylolisthesis. J Bone Joint Surg [Br] 1970;52:432-7. 3. Cloward RB. The treatment of ruptured lumbar intervertebral discs by vertebral body fusion.J. Neurosurg. 1953;10:154-168. 4. Duval-Beaupère G., Schmidt C, Cosson P. A baricentremetric study of the sagittal shape of spine and pelvis: the condition required for an economic standing position. Ann Biomed Eng 1992;20:451-62. 5. Finneson B. Low back pain.JB Lippincott Company Editor1973. 6. Gaines RW, Nichols WK.Treatment of spondylolisthesis by two stage L5 vertebretomy and reduction of L4 onto S1. Spine1985;10:680-6. 7. Gerber M, Crawford N, Chamberlain RH et al. Biomechanical assessment of anterior interbody fusion with an anterior lumbosacral fixation srew-plate. Spine 2006 ;31:76268. 8. Gill GG, Manning JG, White HL. Surgical treatment of spondylolisthesis without fusion. J Bone Joint Surg [Am] 1955;37:493-520. 9. Harms J, Jeszensky D, Stolze D, et al.True spondylolisthesis reduction and monosegmental fusion in spondylolisthesis.In:Bridwell KH, De Wald RI eds. Textbook of spinal surgery, 2nd ed. Philadelphia, PA:Lippincott Raven; 1997: 1337-47. 10. Kimura M.My method of filing the lesion with spongy bone in spondylolysis and spondylolisthesis [in Japanese], Seikei Geka 1968;19:285-96. 11. Labelle H, Roussouly P, Berthonnaud E et al. Spondylolisthesis, pelvic incidence, and spinopelvic balance. Spine 2004;29:2049-54. 12. Lehmer SM, Speffee AD, Gaines RW Jr.Treatment of L5-S1 spondyloptosis by staged L5 resection with reduction and fusion of L4 onto S1.Spine 1994;19:1916-25. 13. Macnab I, Dall D The blood supply of the lumbar spine and its application to the technique of intertransverse lumbar fusion. J bone Joint Surg Br, 1971; 53: 628-38. 14. Morscher E, Gerber B, Fasel J. Surgical treatment of spondylolisthesis by bone grafting and direct stabilization of spondylolisis by mean of a hook screw. Arch Orthop Trauma Surg 1984;103:175-8. 15. Pape D, Adam F, Fritsch E, Müller K, Kohn D. Primary lumbosacral stability after open posterior and endoscopic anterior fusion with interbody implants. Spine 2000;25:2514-18. 16. Ricciardi JE, Pflueger PC, Isaza JE, Whitecloud III TS. Transpedicular fixation for the treatment of isthmic spondylolisthesis in adults. Spine 1995;20:1917-22. 17. Ruf M, Koch H, Melcher R, Harms J. Anatomic reduction and monosegmental fusion in high-grade developmental spondylolisthesis.Spine 2006;31:269-74. 18. Roy-Camille R, Saillant G, Mazel C.Internal fixation of the lumbar spine with pedicle srew plating.Clin Orthop 1986;203:7-17. 19. Stauffer RN, Coventry MB.Posterolateral lumbar spine fusion. J Bone Joint Surg [Am] 1972;54:1195-1204. 20. Ulibarri JA, Anderson PA, Escarega T et al. Biomechanical and clinical evaluation of a novel technique for surgical repair of spondylolysis.Spine, 2006;31:2067-2072. 21. Weinstein J, Rydevick B, RauschningW. Anatomic and technical considerations of pedicle screw fixation.Clin Orthop 1992;284:34-46. 22. Weinstein JN, Spratt KF, Spenegler D, et al. Spinal pedicle fixation : reliability and validity of roentgenogram-based assessment and surgical factors on successful screw placement.Spine 1998;13:1012-18.

902 Spine 23. Wiltse LL, Newman PH, Macnab I. Classification of spondylolysis and spondylolisthesis. Clin. Orthop, 1976;117:23-29. 24. Wiltse LL, Bateman JG, Hutchinson RH, et al. The parasagital sacrospinalis splitting approach to the lumbar spine.J. Bone Joint Surg Am, 1988;50:919-26. 25. Zdeblick TA, David SM. A prospective comparison of surgical approach for L4-L5 fusion. Laparoscopic versus mini anterior lumbar interbody fusion. Spine;2000:25:268287

903

Minimally Invasive Treatments for Spinal Degenerative Pathologies. ALBERTO ALEXANDRE1, ANDREA M. ALEXANDRE2 1

EU.N.I. European Neurosurgical Institute, Treviso , ITALY School of Radiology, Catholic University of Rome, ITALY

2

Key words: spine, low back pain, minimally invasive, lumbar spine, nerve root dysfunction

Introduction Low back pain and lumbar nerve root disfuncions have been show by several statistical analysis to affect 65 to 80% of adults at some time in their lives, and although most cases resolve quickly, 40% recur and 5% result in a residual disability after 1 year. A very ample revision of the pathophysiology and reconsideration of the possible treatments has grown recently because of the observation of the extremely high statistical incidence of the problem, and the not so rare discrepancy between the pathological findings in neuro-imaging and the clinical situation of the patinet, both before and after open surgery,

Pathophysiology of inflammation The wide variety of potential pathogens for the human body requires a defense system that is diversified and adaptable. The immune system is a complex network of cells and tissues that work together to protect the body against foreign invaders. The immune system has been implicated in the pathogenesis of disorders as diverse as atherosclerosis, miocardial infarction, shock, diabetes, and stroke. Therefore an understanding of immune function is foundamental to the study of a variety of diseases, among which spinal degenerative processes. Innate defenses require no previous exposure to mount an effective response against an antigen. Natural killer cells and phagocytic cells such as neutrophils and macrophages are mediators of innate defenses. Indeed specific defenses respond more effectively on second exposure to an antigen (adaptive) . B and T - lynphocytes are the agents of specific immunity. Although separating immune components into specific and innate systems is helpful for studying inflammation and immunity, it is an artificial division, because they function in a highly integrated manner. The complement system consists of about 20 plasma proteins that interact in a cascade fashion to produce important mediators of inflammation and immunity. The cascade can be activated by microbial antigens (alternative pathway) or by antigenantibody complexes (classical pathway). Cytokines are peptide factors released by immune cells, that have many functions, including as inflammatory mediators,

904 Spine chemotaxins, intercellular communication signals, growth factors, and growth inhibitors. Inflammation occurs when cells are injured, regardless of the cause of the injury, it is a protective mechanism that also begins the healing process. The inflammatory response has three purposes: • to neutralize and destroy invading and harmful agents • to limit the spread of harmful agents to other tissue • to prepare any damage tissue for repair. Five cardinal signs of inflammation have been described: redness, swelling, heat, pain and loss of function (rubor, tumor, calor, dolor, functio lesa). Inflammation and infection are commonly confused because they often coexist. Under normal conditions, infection is always accompanied by inflammation, however not all inflammations involve an infectious agent. Inflammation can be categorized as either acute, lasting less than 2 weeks and chronic, that extends over a longer period and tends to be more diffuse. Inflammatory chemical mediators such as histamine, prostaglandins and leukotrienes are released from injured tissues, mast cells, macrophages and neutrophils and increase vascular permeability, vasodilate and attract immune cells to the area (chemotaxis). Phagocytes migrate in the inflamed area, collect at the site of the vessel, and squeeze through into the tissue; migration of neutrophils and macrophages is facilitated by specific adhesion molecules: selectins and integrins present on the surface of endothelial cells and leukocytes. Neutrophils arrive in large number in acute bacterial infections and begin active phagocytosis; neutrophils and macrophages produce proteolytic enzymes and oxidizing agents to destroy and digest antigens. On the other hand in chronic inflammation macrophages and lymphocytes predominate. Healing process is mediated by growth factors released from platelets and immune cells that stimulate fibroblasts; they synthesize connective tissue, are able to migrate divide and manufacture extracellular matrix proteins. Endothelial cells respond to angiogenic growth factors by forming capillary networks. Exudate: Inflammatory exudate functions to transport immune cells, antibodies and nutrients to the tissue and dilute the offending substances. • Serous exudate is watery and low in proteins; • Fibrinous exudate is thick, stick and high in protein; • Purulent exudate contains infective organism, leukocytes and cellular debris; • Hemorrhagic exudate contains mainly red blood cells. Systemic manifestation of inflammation include fever, neutrophilia, lethargy, muscle catabolism, increased acute phase proteins (PCR) and increased erythrocyte sedimentation rate (ESR). All these responses are attributed to the increase of IL-1, IL6 and TNF released from macrophages and inflamed tissues. Regulation of immune function: the mechanisms that promote inflammation and enhance immune function are much better understood than those that negatively regulate these processes. The destructive power of the immune system can cause severe tissue damage unless carefully controlled. Inhibition of immune response occurs in a number of different ways: regulatory T-cell cytokines, complement inhibitors, degradation of inflammatory mediators, circulating antiproteases and antioxidants agents such as superoxide dismutase, glutathione peroxidase and catalase

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

905

These general principles are to be kept in mind while considering the complex problem of spinal degenerative pathologies. The physiopathology of pain and of nervous dysfunction originating from these problems is a challenging theme, and is the basis for the new treatments which are coming into general interest for the management of an enormous number of patients, which can be brought back to a good quality of life without major open surgical spinal procedures. The disc did not become the center of attention until 1933, when W. J. Mixter and J. S. Barr indicated the correct pathogenesis of lumbusciatic pain and nerve disfunction, and, hence, offered an appropriate surgical treatment. The neurogenic nature of sciatica had first been described by Domenico Cotugno (1764). Following him, outstanding French neurologists such as Lasegue, Dejerine, and Sicard enriched our understanding of the basis of sciatica. The work of the German pathologists Schmorl and Andrea (1927-1929) established the modern basis for understanding the intervertebral disc, by providing very clear discussions of herniations as well as degenerations. Low Back Pain secondary to degenerative disk disease is a condition that affects men and women equally, in young to middle-age with peak incidence at approximately 40 years. Disk degeneration increases with age, but degenerated disks are not necessarily painful. Probably bipedal ambulation this is the evolutionary event that made the lumbar spine susceptible to degenerative disease. Degeneration is a common event to structures that compone the functional spinal unit: two adjacent vertebral bodies and the intervertebral disk. The disk and 2 zygapophyseal joints at the same level function as a trijoint complex. As humans age, they endure both macro and microtraumas and undergo changes in body habitus that alter and redistribute biomechanical forces unevenly on the lumbar spine. Natural progression of degeneration of the lumbar segment of motion proceeds with characteristic anatomic, biomechanical, radiologic, and clinical findings in lumbar degenerative disk disease. Posterior elements of the lumbar spinal functional unit bear less weight than anterior elements in all positions. Anterior elements bear over 90% of forces transmitted through the lumbar spine in sitting; during standing, this portion decreases to approximately 80%. The spine functions best within a realm of static and dynamic stability. Bony architecture and associated soft tissue structures, especially the intervertebral disk, provide static stability. Dynamic stability is accomplished through a system of muscular and ligamentous supports acting in concert during various activities. Recently the relevant existing research literature on the problem of intervertebral disc degeneration (Degenerative Disc Disease) has been thoroughly reviewed and summarized by An et al. (1) and by Adams and Roughley (2) specifically in order to understand the characteristics of disc degeneration process, and distinguish it from physiological aging. Intervertebral discs are pads of fibrocartilage that resist spinal compression while permitting limited movements. Individual lamellae of the anulus fibrosus consist primarily of collagen type I fibers passing obliquely between vertebral bodies, with orientation of the fibers being reversed in successive lamellae. The nucleus pulposus consists of a proteoglycan and water gel held together loosely by an irregular network of fine collagen type II and elastin fibers. The major proteoglycan of the disc is aggrecan,

906 Spine (3,4) which, because of its high anionic glycosaminoglycan content (chondroitin sulfate and keratan sulphate), provides the osmotic properties needed to resist compression. A young healthy disc behaves like a water bed, with the high water content of the nucleus and inner anulus enabling the tissue to act like a fluid. The outermost anulus acts as a tensile skin to restrain the nucleus. With increasing age, disc water content decreases, especially in the nucleus, and most of the anulus then acts like a fibrous solid to resist compression directly. In physically disrupted discs, regions of fibrous tissue resist mechanical loading in a haphazard manner, and the hydrostatic nucleus is reduced or absent. Cells in the anulus are elongated parallel to the collagen fibers, rather like fibroblasts. Cells in the nucleus are initially notochordal but are gradually replaced during childhood by rounded cells resembling the chondrocytes of articular cartilage. Anulus cells synthesize mostly collagen type I in response to deformation, whereas nucleus cells respond to hydrostatic pressure by synthesizing mostly proteoglycans and fine collagen type II fibrils. Cell density declines during growth, (5) and in the adult is extremely low, especially in the nucleus.(6,7) Blood vessels are normally restricted to the outmost layers of the annulus, and metabolite transport is by diffusion. As in any living tissue, in vitro experiments have shown that a chronic lack of oxygen causes nucleus cells to become quiescent, since low oxygen tension in the center of a disc leads to anaerobic metabolism, resulting in a high concentration of lactic acid and low pH (6) A chronic lack of glucose can kill them (8). Deficiencies in metabolite transport appear to limit both the density and metabolic activity of disc cells (6). As a result, discs have only a limited ability to recover from any metabolic or mechanical injury. Endplate permeability and, therefore, disc metabolite transport normally decrease during growth and aging, and yet increase in the presence of disc degeneration and following endplate damage (9). This is one essential difference between aging and degeneration. Disc cells synthesize their matrix and break down existing matrix by producing and activating degradative enzymes, such as matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinase (ADAMS). (10-16) Molecular markers of matrix turnover are naturally most plentiful during growth but usually decline thereafter (17) The proteoglycan content of the disc is maximal in the young adult and declines thereafter (17) presumably because of proteolysis. Disc cells appear to adapt the properties of their matrix to suit prevailing mechanical demands, although the low cell density and lack of a blood supply ensure that changes are not as rapid or pronounced as in adjacent vertebrae (18). Adaptive remodeling probably contributes to the large variation in compressive strength of adult discs, which ranges from 2.8 to 13.0 kN when they are tested in a manner that causes failure in the disc rather than the adjacent vertebra (19). Injured discs show increased levels of catabolic cytokines, increased MMP activity, (17,20) and scar formation, (21) especially in the vicinity of anular tears.(21,22) They also show evidence of renewed matrix turnover (17,23) and a more variable range of collagen fibril diameters.(24) However, gross injuries to a disc never fully heal. Scalpel cuts in the outer anulus fill with granulation tissue, with only the outer few millimeters being bridged by scar tissue.(25,26) Anular tears are not remodeled as in bone, presumably

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

907

because the sparse cell population is unable to break down the large collagen fiber bundles of the anulus and replace them with new (27). Collagen turnover time in articular cartilage is approximately 100 years (28) and could be even longer in the disc. Proteoglycan turnover is faster, possibly 20 years, (27) and some regeneration of nucleus pulposus appears to be possible in young animals.(29) Injuries that affect the inner anulus or endplate decompress the nucleus (30), and healing processes are then overtaken by severe degenerative changes (26). A series of biochemical and histologic changes have been described as tipical of disc aging process. The blood supply to the vertebral endplate decreases during early childhood, and microstructural clefts and tears become common by the age of 15 years, especially in the nucleus and endplate (33). Cell density decreases throughout growth (5), and the nucleus pulposus tends to condense into several fibrous lumps, separated from each other and from the cartilage endplate by softer material (34). Proteoglycan fragmentation starts during childhood (31), and with increasing age, the overall proteoglycan and water content of the disc decreases, especially in the nucleus (17) and the collagen content increases. Fine type II collagen fibrils in the inner anulus are replaced by type I fibers as the anulus encroaches on the nucleus, and type I fibers throughout the disc become coarser. As long as the proteoglycan fragments remain entrapped in the disc, they can fulfill a functional role similar to that of the intact proteoglycan. Reduced matrix turnover in older discs enables collagen molecules and fibrils to become increasingly cross-linked with each other, and existing cross-links become more stable (23). In addition, reactions between collagen and glucose lead to nonenzymatic glycation (extra cross-links that give old discs their characteristic yellowbrown appearance) (32). Increased cross-linking inhibits matrix turnover and repair in old discs, encouraging the retention of damaged macromolecules (27) and probably leading to reduced tissue strength. Matrix synthesis decreases steadily throughout life but sometimes increases again in old and severely disrupted discs (17). Reduced synthesis is partly attributable to decreased cell density, although proteoglycan synthesis rates per cell also decrease (35). Anular tears become increasingly common after the age of 10 years, (33) especially in the lower lumbar spine, and reach a peak in middle age.(36) 3 types of tears can be distinguished: circumferential tears or delaminations, peripheral rim tears, and radial fissures. They Circumferential tears may represent the effects of interlaminar shear stresses, (37) possibly occurring from compressive stress concentrations in older discs . Peripheral rim tears are more frequent in the anterior annulus (38) and may be associated with bony outgrowths.(39) Mechanical (40) and histologic (38) considerations suggest that they are related to trauma. Radial fissures progress outward from the nucleus, usually posteriorly or posterolaterally, (38) and this process can be simulated in cadaveric discs by cyclic loading in bending and compression. (40) Radial fissures are associated with nucleus degeneration, (38,41) but it is not clear which comes first. The 3 types of anulus tear probably evolve independently of age and each other. (42) Radial fissures may allow gross migration of nucleus from the annulus. The disc herniation may result in protrusion, extrusion, or sequestration of the nuclear material. On the other side the nucleus increasingly bulges into the vertebral bodies in later life (43): vertebral endplates are the spine’s weak link in compression. Damage of these immediately

908 Spine decompresses the adjacent nucleus and transfers load onto the anulus, causing it to bulge into the nucleus cavity.(30,44) If nucleus pulposus herniates through a damaged endplate, then subsequent calcification can create a Schmorl’s node. Severe changes are accompanied by a marked loss of nucleus pressure (46) and collapse of anulus height . In effect, the disc behaves like a flat tire.(47) It is anulus height that determines the separation of adjacent neural arches, and anulus collapse/bulging in old discs can lead to more than 50% of the compressive force on the lumbar spine being resisted by the neural arch.(48)This effect probably explains why narrowed discs are associated with osteoarthritis in the apophyseal joints and with osteophytes around the margins of the vertebral bodies.(49) The posterior anulus and its adhering longitudinal ligament are supplied by the sinuvertebral nerve, a mixed autonomic and somatic nerve believed capable of nociception, whereas the anterior and lateral regions are supplied by autonomic nerves.(50) Nociceptive nerve fibers normally penetrate only the outermost 1-3 mm of annulus (51,52) but have been reported to progress in toward the nucleus in the anterior regions of painful and severely disrupted discs.(51) The bony vertebral endplate has a similar density of innervation.(53) Pain provocation studies associate severe back pain with relatively innocuous mechanical stimulation of the outer posterior anulus and endplate.(54) Painful discs are always structurally disrupted (51) and show irregular stress concentrations.(55) They appear to become sensitized to mechanical loading, and animal experiments have confirmed that contact with nucleus pulposus can lower nerve stimulation thresholds in adjacent tissues.(56) Pain sensitization is of most functional significance when it occurs in the outer anulus fibrosus because that is where the highest stress concentrations are found in degenerated discs. Features of discs most closely associated with pain include disc prolapse,(41) disc narrowing,(57,58) radial fissures, 57,59) especially when they reach the disc exterior and leak,(60) and internal disc disruption, including inward collapse of the anulus.(61) More variably related to pain are endplate fracture and Schmorl nodes,(62) and disc bulging.(41,57,62,63) Disc signal intensity on magnetic resonance imaging (MRI) has little if any relationship to pain.(57) As underlined by several Authors, thereby many different influences are at work in old and degenerating discs, including genetic inheritance, impaired metabolite transport, altered levels of enzyme activity, cell senescence and death, changes in matrix macromolecules and water content, structural failure, and neurovascular ingrowth. Inadequate metabolite transport appears to be an inevitable consequence of growth and probably has little direct clinical relevance because it mostly affects the nucleus pulposus, which is the region of degenerated discs that is loaded the least and has the fewest nerve endings. The fact that endplate damage leads to disc degeneration, even though it enhances metabolite transport into the disc,(9) suggests that structural damage has the decisive influence on the degenerative process. Inadequate nutrition may predispose to disc degeneration by compromising a disc’s ability to respond to increased loading, or injury. Certain markers of altered cell metabolism, such as increased cytokine and MMP activity,(65,66) could be used as a definition. They are associated with structural defects

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

909

in the disc,(22) but currently available markers are unable to differentiate degeneration from growth, adaptive remodeling, and healing. Logically, to suggest that cytokines or proteinases cause disc degeneration is equivalent to blaming war on soldiers! Cytokines and proteinases are merely agents of change, rather than causes. The very complexity of connective tissue metabolism suggests that degeneration could occur from a failure to regulate specific proteinase activities.(64,67) However, it could equally be argued that the redundancy inherent in such a complex system (cells can achieve a given effect by many different methods) ensures that the system is very robust. M.A. Adams and P.J. Roughley have underlined (2) that aging causes inevitable and progressive changes in disc matrix composition, which resemble changes in other aging collagenous tissues. Biochemical changes influence tissue stiffness and strength, and some degraded matrix molecules can impair disc cell metabolism.(68) In addition, some matrix changes are detectable in vivo using MRI, manifesting as a dark disc.(69) However, age-related changes in matrix composition are inevitable, start soon after birth,(31,33) and are unrelated to pain.(70) Age-related reductions in endplate vascularity and disc cell density (5) could simply reflect necessary adaptations to increased mechanical loading at the onset of ambulation, and reduced metabolite transport in a growing disc. The microstructural clefts and tears that appear increasingly during growth may possibly lead to more extensive disruption in later life, but so long as they remain small, they appear to have little effect on the internal mechanical function of the disc.(45) In addition, they affect all spinal levels to a similar extent, unlike macroscopic changes that occur mostly between L4 and S1. Ingrowth of nerves and blood vessels has been shown to be an important feature of structurally disrupted discs, and appears to be directly, though variably, associated with pain.(51) Ingrowth could be facilitated by the loss of hydrostatic pressure that characterizes internal regions of intact discs, and that would collapse hollow capillaries. Reduced proteoglycan content in old and degenerated discs may also facilitate the ingrowth of nerves and capillaries because aggrecan can inhibit their growth in vitro.(71,72). Ingrowth of nerves has been thought as a possible base for the evolution of acute pain in chronic persistent pain. Physical and biologic mechanisms make structural failure progresses and, therefore, this is a suitable marker for a degenerative process. Damage to one part of a disc increases load-bearing by adjacent tissue, so the damage is likely to spread to adjacent articular structures and to ligaments. Pathologic radial bulging of a disc progresses because compressive forces act to collapse the bulging lamellae. Biologic mechanisms of progression depend on the fact that a healthy intervertebral disc equalizes pressure within it, whereas a disrupted disc shows high concentrations of compressive stress in the anulus, in presence of a decompressed nucleus. Reduced nucleus pressure impairs proteoglycan synthesis (73), so the aggrecan and water content of a decompressed nucleus would progressively decrease, which is the opposite of what is required to restore normal disc function. An extensive review of nomenclature made clear distinctions between pathologic and age-related changes in discs, and included major structural changes such as radial fissures and disc narrowing in the former category (74). Referring to tendon degeneration, Riley et al (67) suggest an active, cell-mediated process that may result from a failure to

910 Spine regulate specific MMP activities in response to repeated injury or mechanical strain. There is a growing consensus that degeneration involves aberrant cell-mediated responses to progressively deteriorating circumstances in their surrounding matrix. The process of disc degeneration is an aberrant, cell-mediated response to progressive structural failure. A degenerate disc is one with structural failure combined with accelerated or advanced signs of aging. The term “Degenerative Disc Disease” should be applied to a degenerated disc, which is also painful. Cell-mediated responses to structural failure can be regarded as the final common pathway of the disease process (75). Although mechanical loading precipitates degeneration, the most important cause of degeneration could be the various processes that weaken a disc before disruption, or that impair its healing response. The combined effects of an unfavorable inheritance, middle age, inadequate metabolite transport, and loading history appear to weaken some discs to such an extent that physical disruption follows some minor incident. In the evaluation of the degenerative processes we have up to here considered, Modic changes nowadays are taken in careful consideration as dynamic markers of the normal age-related degenerative process affecting the lumbar spine. Modic changes, a common sign in MR imaging of the spine, are signal intensity changes in vertebral body marrow adjacent to the endplates of degenerative discs and were firstly described by Modic MT in 1988 (76). The classification include three main forms: type 1 changes with decreased signal intensity on T1-weighted spin-echo images and increased signal intensity on T2-weighted images; type 2 with increased signal intensity on T1-weighted images and isointense or slightly increased signal intensity on T2-weighted images; type 3 with decreased signal intensity on both T1 and T2-weighted images. In fact these lesions can convert from one type to another with time, with mixed-type changes probably representing the intermediate stages in this conversion. Type 1 changes are likely to be inflammatory in origin and seem to be strongly associated with active low back symptoms and segmental instability, type 2 changes are less clearly associated with LBP and seem to indicate a more biomechanically stable state, while, the exact nature and pathogenetic significance of type 3 changes remain largely unknown (77). They appear to be a relatively specific but insensitive sign of a painful lumbar disc in patients with discogenic low back pain (78). It is assumed that people with both degenerative disc disease and Modic changes on MRI would have a more pronounced clinical profile than those with only degenerative disc disease. These last would differ from those with neither of the two MRI findings. Modic change constitutes the crucial element in the degenerative process around the disc in relation to low back pain, history, and clinical findings (79). Furthermore, it seems that a disc herniation is a strong risk factor for developing Modic changes (especially type 1) during the following year (80) and that type 1 signal intensity changes on MR images have a high positive predictive value in the identification of a pain generator (81). A longitudinal follow-up of Modic changes on MRI at 3 years demonstrates that Modic changes are common MRI findings in patients with degenerative lumbar disc disease, and that Modic Type II changes may be less stable than previously assumed (82).

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

911

Finally to evaluate the prevalence of Modic changes in subjects with and without low back pain (LBP) another interesting study delineated by the US National Institutes of Health will come to an end by the end of the year 2009. Subjects with LBP are compared with healthy volunteers (83). The first relevant point to be considered in the clinical evaluation of low back pain is to rule out cancer, infection, or a neurologic or medical emergency. A workup for neoplasm is justified in a patient who is older than 50 years or younger than 20 years, or who has a history of cancer. Neurologic emergency such as cauda equina syndrome consisting in bladder or bowel incontinence, reflex deficits, or weakness in extremities, warrants MRI to establish the need for urgent surgery for nerve decompression. Complaints of fever and chills and a history of i.v. drug abuse, immune suppression, corticosteroid use, or recent urinary tract infection suggest an infectious process. Referred visceral pain, such as from an abdominal aortic aneurysm, also needs to be investigated. Onset, duration, frequency, location, radiation, quality, intensity, and aggravating and alleviating factors of the pain should be evaluated and related to the presence of neurological deficits. Using precision diagnostic blocks in chronic back pain that did not respond to conservative treatment, researchers isolated facet joint pain in 40% of cases, discogenic pain in 26%, segmental dural or nerve root pain in 13%, and sacroiliac joint pain in 2%. After a comprehensive physical examination has ruled out those problems that would require acute intervention or further investigation, treatment directed toward mechanical back pain may be initiated. When conservative treatment fails, other interventions may be appropriate; to implement these, it is important to learn the source of the pain. Briefly, owing to the different sources, pain my be represented as follows: a) Mechanical Low Back Pain is a descriptive term commonly used for non-discogenic origin. This is due to stress to the muscles, tendons, and ligaments. Mechanical Low Back Pain is attributed to strenuous daily activities, heavy lifting, or prolonging postures. It is a chronic, dull, aching pain of varying intensity that affects the lower lumbar area, and might spread to the buttock. Pain can be worsen during the day, better after rest. No associated neurological symptoms are observed, nor a cough or sneeze effect o the lower limbs. Upon Radiological study correction of static or dynamic postural abnormalities can be planned. An exercise program consisting of abdominal and back strengthening exercise is needed. b) Degenerative Disease of Facet Joint engenders a kind of pain which is often episodic, and sometimes will extend to the limb and mimic radicular pain. Pain is tipically increased with activity and relieved by rest. The onset of each attack is usually abrupt. In these situations surgery is rarely recommended. NSAID and manipulation as well as fisical therapy can at times give dramatic relief. Pain that persists despite conservative treatment should be reevaluated. Articular facets provide structural support to the posterior aspects of the spine and contribute to its flexibility. Ligaments around the facet joint combine with the synovium to form the joint capsule. Often the facet joint complex contributes to back pain. Facet arthropathy may be caused by a combination of aging, pressure overload of the joints caused by narrowing disks, and injury. Lumbar facet pain typically presents in a bandlike distribution across the low back, although it can radiate to the

912 Spine posterior or anterior thigh or groin. Pain is typically exacerbated by activity, standing or sitting for long periods of time, and lumbar extension. The patient may find standing in a forward-flexed posture comfortable. Pressure on the involved facet joints during the physical exam will cause discomfort, which will be exacerbated with a hyperextension maneuver. c) The Sacro-iliac joint pain. The Sacro-iliac joint connects the sacrum and the ileum and is covered by both hyaline and fibrocartilage. This joint is not very flexible, moving only 2 to 4 mm. Sacro-iliac joint pain can be caused by injury, inflammation, or excessive motion due to abnormalities in the joint. This type of pain is particularly common in women who have given birth and whose sacro-iliac joint has been disrupted by hormonal changes and mechanical forces. It is also common among patients who participate in ice skating, golf, and bowling because of the repetitive torsional forces involved in those sports. Sacro-iliac joint inflammation can also be caused by rheumatologic disorders such as Reiter’s syndrome, ankylosing spondylosis, and psoriatic arthritis. Common symptoms of a sacro-iliac joint problem are pain in the low back, buttock, or thigh; sciatica-like pain; and difficulty sitting for long periods. To evaluate for SI joint pain on the physical exam, perform Gaenslen’s test and Faber, and observe for Patrick’s sign (pain with external hip rotation). Distraction and compression tests may also be performed. d) Lumbar discogenic pain and internal disc disruption are defined as lumbar pain, with or without referred pain, stemming from an intervertebral disc.(definition by The International Association for the Study of Pain in its classification of spinal and radicular pain syndromes (84).Discogenic pain is caused by internal disruption of the normal structural and biochemical integrity of the symptomatic disc. Discography is necessary to establish and confirm these diagnoses . The primary indication for lumbar discography is chronic low-back pain with or without radicular pain in the absence of MR imaging-documented neural compression (85). Discography can be used for identifying disc lesions and pain generators when MR images are equivocal. Discography is also indicated in the following scenarios: when clinical findings point to one level or one side and myelography or MR imaging indicates a different level, or when the disc protrusion is asymmetrical to the contralateral side of the patient’s symptoms. In some cases, far-lateral disc herniations may be confused with nerve sheath tumors or hematomas. Again, discography is indicated to resolve these diagnostic dilemmas. Discography is also useful in evaluating discs adjacent to previously fused lumbar segments. In cases in which a prior instrumentation-assisted lumbar fusion has produced a good result but in which the patient eventually develops recurrent back pain, these patients are good candidates for discography because MR imaging studies are often too considerably distorted by artifacts to demonstrate properly the discs adjacent to instrumented fusions. Discography may also be indicated to assist in the diagnosis of painful pseudarthrosis. Discography can be performed in patients who have undergone attempted posterolateral lumbar fusion in which posterior lumbar interbody fusion has not been performed. A positive discogram at the “fused” level may

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

913

identify a persistently painful disc, suggesting the need for disc removal and interbody fusion. e) Radicular pain often is the result of nerve root inflammation and irritation. Clinical practice and research demonstrate that mechanical compression on the nerves may cause only motor deficits and altered sensation, but will not cause pain. Inflammation in the epidural space and nerve roots provoked by a herniated disk is a significant factor in causing radicular pain. Chronic compression of a nerve root can induce axon ischemia, impede venous return, promote extravasation of the plasma protein, and cause local inflammation. If dorsal root ganglia are chronically compressed and irritated, this theoretically can lead to their sensitization and resultant radicular pain. Similar mechanisms of radicular pain are postulated to occur in the thoracic and cervical spine as well. In summary, clinical practice and animal research suggest that radicular pain is the result of inflammation of the nerve root in the epidural space provoked by leakage of disk material, compression of the nerve root vasculature, or irritation of dorsal root ganglia from spinal stenosis. f) Failed Back Surgery Syndrome (FBSS) is a not rare complication of open spinal surgery, since 3 to 14 % of patients operated for a prolapsed intervertebral disc suffer from recurrent painful symptoms. FBSS is characterized by severe chronic postoperative pain , which is usually resistant to physiotherapy and pharmacological treatment. The syndrome has various causes which range from demonstrable anatomical causes, to psychological aspects. The most frequent causes are recurrent or residual disc herniation, and epidural fibrosis. Epidural fibrosis is considered to be the specific cause in 8 to14 % of the cases, in the literature, and it occurs in 1 to 2 % after discectomy. Epidural and periradicular fibrosis may develop a fixing effect on neural structures, inducing dynamic neural tension especially during repeated movements, and stenosis on the root and on the ganglion imparing blood flow and maintaining subhyskemia. These situations lead to low back pain and/or recurrent radoculopathy.

Conservative Treatment An anesthetic block or denervation may provide lasting relief. An anesthetic agent, such as bupivacaine, is combined with a corticosteroid and injected directly into the facet or sacro-iliac joint with the aid of fluoroscopy; the local anesthetic interrupts the pain-spasm cycle, and the corticosteroid reduces inflammation. A medial branch block may also be used to treat facet pain. The medial branch of the dorsal primary ramus of the spinal nerve supplies the facet joint, the supraspinal ligament, and the interspinal ligaments. Branches from the adjacent spinal nerve and the spinal nerve above supply each joint. Complete denervation of any facet requires blockade of two levels. A facet or sacro-iliac joint injection is considered successful when a patient’s pain is reduced by half. One study of patients with facet pain found that all who received a series of three medial branch blocks had significant relief for up to 3 months, 82% for up to 6 months, and 21% for up to 12 months. Contraindications to injections include bacterial infection, pregnancy, bleeding diathesis, and anticoagulant therapy. Precautions should be taken in the

914 Spine presence of diabetes or a prosthetic heart valve. A joint injection that provides only short-term relief may be considered diagnostic of either Sacro-iliac or facet joint pain, for which radio-frequency neuroablation or other types of rhizotomy may be applied. Pulsed radio-frequency treatment appears to have very satisfactory and long lasting results, but up to now there are no long-term evaluations of the results.

Epidural steroid injections Although the primary indication for epidural steroid injection is radicular pain associated with a herniated nucleus pulposus, a variety of other indications have been reported in the literature. Lumbar epidural steroid injections may be indicated for lumbar radicular pain associated with any of the different following conditions: lumbosacral disk herniation, spinal stenosis with radicular pain (central canal stenosis, foraminal and lateral recess stenosis), compression fracture of the lumbar spine with radicular pain, facet or nerve root cyst with radicular pain Cervical epidural steroid injections have been used to treat pain associated with acute disk herniation and radiculopathy, postlaminectomy cervical pain, cervical strain syndromes with associated myofascial pain, and postherpetic neuralgia. Thoracic epidural steroid injections have been reported in the medical literature as treatment for pain associated with thoracic radicular pain secondary to disk herniations, postherpetic neuralgia, diabetic neuropathy, degenerative scoliosis, idiopathic thoracic neuralgia, thoracic compression fracture. Clinical improvement after epidural steroid injection coincides with decreased nerve root edema. A possible mechanism of steroid action reflects inhibition of Phospholipase A2 resulting in decreased synthesis of prostaglandine. The steroid preparation most commonly used is methylprednisolone acetate. Other steroid preparations used include triamcinolone diacetate. For lumbar epidural injections the steroid preparation is often diluted with local anesthetic to a 6 ml - 10 ml volume to allow spread to adjacent nerve roots which may be inflamed as well. The use of a dilute local anesthetic is often beneficial in patients with coexisting myofacial pain, and can act as a marker of correct deposition of medication with the onset of sensory blockade. Systemic infection or local infection at the site of a planned injection, bleeding disorder or fully anticoagulated (for example, on a fully “therapeutic” dose of Coumadin, heparin), an history of significant allergic reactions to injected solutions (eg, contrast, anesthetic, corticosteroid), acute spinal cord compression, and pregnancy are to beconsidered contraindications for epidural steroid injecions. Caution should be used when performing injections in patients with poorly controlled diabetes, since the corticosteroid injection may transiently increase blood glucose levels. Patients with a history of immunosuppression may require additional precautions, such as preprocedure laboratory work and/or antibiotics. Caution should be exercised when performing injections in individuals who have a history of congestive heart failure because of the potential for steroid-induced fluid retention. Epidural steroid injections have been endorsed by the North American Spine Society

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

915

and the Agency for Healthcare Research and Quality (formerly, the Agency for Health Care Policy and Research) of the Department of Health and Human Services as an integral part of nonsurgical management of radicular pain from lumbar spine disorders. Epidural steroid injections are indicated in the presence of acute nerve root inflammation. The first epidural injection using the caudal approach was performed in 1901, when cocaine was injected to treat lumbago and sciatica (presumably pain referred from lumbar nerve roots). According to report, epidurals from the 1920s-1940s involved using high volumes of normal saline and local anesthetics. Injection of corticosteroids into the epidural space for the management of lumbar radicular pain was first recorded in 1952. Epidural steroid injections may help to identify the region and spinal column of potential pain generation through pain relief after local anesthetic injection to the site of presumed anatomic pathology. In addition, if the patient receives several weeks or more of pain relief, then it may be reasonable to assume that an element of inflammation was involved in pathophysiology. Since prolonged pain relief is presumed to result from a reduction in an inflammatory process, it is also reasonable to assume that during the prolonged pain relief, the afflicted nerve roots are relatively protected from the deleterious effects of inflammation. In most cases, epidural injections are considered after treatment attempts by physical therapy, manual therapy, or medications have failed to improve patients’ symptoms. We think that epidural steroid injections may be indicated earlier in the treatment algorithm, with a well-designed spinal rehabilitation program. In general, patients who have had symptoms for less than 3 months have response rates of 90%. When patients have had radiculopathy symptoms for longer periods, response decreases to approximately 70%. Response decreases to 50% in patients who have had symptoms for over 1 year. Patients with chronic back pain will have better response if they develop an acute radiculopathy. The response to epidural steroid injection is related to the underlying pathophysiology. In general, acute radicular pain from lumbar disk herniation responds more favorably than does radicular pain from lumbar spinal stenosis. Patients with radicular pain after lumbar spine surgery frequently will benefit from more complex epidural endoscopic treatments, unless the radicular pain is from a recurrent herniated nucleus pulposus. Epidural steroid injections are often helpful for radicular pain from stenosis. Several researches demonstrated the efficacy of lumbar transforaminal epidural injections in patients with persistent sciatica from lumbar disk herniation or spinal stenosis. Lutz (86) and colleagues compared transforaminal lumbar epidural injection with lumbar paraspinal trigger-point injection. The success rate in the transforaminal injection group was 84%, compared with 48% in the saline group. Botwin (87) and colleagues demonstrated the efficacy of the transforaminal epidural injection in their retrospective cohort study in patients with sciatica (caused by lumbar spinal stenosis), with anesthetic and/or corticosteroid. Riew (88) (and colleagues reported results from a prospective, randomized, double-blinded, controlled clinical trial on patients with severe sciatica from spinal stenosis or lumbar disk herniations.3 with bupivacaine and steroid.Resalts speak in favour of steroid injection. Rhee (89) and colleagues found a difference in patients undergoing interlaminar and transforaminal ESI.5 , in favour of

916 Spine these last. Since 5 years we have decided to use caudal epidural injections trans sacral-jatus , since we have observed better results through this way of administration. This is probably due to the fact that this approach will give a wash-out of the large epidural area which is the site of sediment of irritative cathabolic subsances, and which is not normally touched by transforaminal injections. Barre (90) and colleagues reported that in patients with symptomatic lumbar spinal stenosis who received caudal ESIs, a visual numeric score improvement of 50% or greater was seen in 35% of them. 6 Long-term treatment success was seen in 35% of patients after a mean follow-up of 32 months. Anwar (91) and coauthors demonstrated that caudal injections could benefit patients with limited straight leg raise and symptoms of radicular pain or spinal stenosis; in this study, 65% of patients were noted to have some improvement at 3 months.

Minimally invasive surgical treatments Mac-Ewen (1848-1924) described the laminectomy procedure and Ménard (18951934) described a costotransversectomy approach Surgery of the spine started when MacEwen (1848-1924). During the same time period, investigators such as Weber (1827), Rauber (1876), and Messerer (1880) began to perform some research studies of the biomechanics of the spine. Then, in 1895, William Conrad Röntgen (1845-1923) established imaging and the evolution of spinal disorders entered a new path. At first only anteroposterior x-ray views were available until Davis obtained a lateral radiograph in 1925. Another developmental milestone was met around 1930 with the introduction of myelography; this imaging modality later helped Dandy and others to remove intervertebral discs via laminectomies. Surgery for disc herniation was first performed by Oppenheim and Kruse (1909); later Mixter and Barr performed the laminectomy via the transdural approach to remove the disc. The Italian physician Bonomo, suggested a similar procedure in 1902. Love introduced the intralaminal–extradural approach for discectomy between 1937 and 1939. Forty years later microsurgery was introduced by pioneers such as Caspar (92) and Yasargil in 1977. During the same time period, progress was done in anterior, posterior, and other surgical approaches, and in the use of instrumentation.The concept of degenerative disc disease developed.King, in 1944, suggested the use of transpedicular screws, but this form of treatment was not used until 1959 by Boucher. Holdsworth and Hardy reported the use of the first fixateur interne in 1953. Harrington introduced his instrumentation for scoliosis around 1958; it was later used for other conditions. At present Degenerative Disc Disease is considered one of the most common spinal disorders. It is thought to cause pain by the mobility that is created and, hence, the segmental instability that is produced. As a result of this understanding of the pathophysiology of the condition, stabilization and fusions have become a popular modality of treatment. Today stabilization is achieved using posterior instrumentation (segmental or nonsegmental), anterior stabilization (cages, devices, and so forth), or a combination of both techniques like that shown in the combined anterior – posterior stabilization.

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

917

In order to resolve all the problems associated with Degenerative Disc Disease, prosthetic disc designs became a challenge with regard to the mobility and elasticity of intervertebral discs. A disc nucleus replacement device is designed to replace only the inner portion of the disc (the nucleus). A variety of disc nucleus replacement technologies are currently being investigated in the laboratory, and some have been implanted in countries outside the US. Various materials are utilized in these implants, including metals and ceramics, injectable fluids, hydrogels, inflatables, and elastic coils (93). In East Germany around the 1980s, Schellnac and Büttner Jans designed the SB Charité device. It was first implanted by Zippel in 1984 and was later abandoned. The SB Charité III artificial disc was introduced in 1987 and became widely used in Europe. Several manufacturers are currently researching, developing and testing total disc replacement. The Charite has been approved by the FDA for the surgical treatment of single-level disease at the L4-5 or L5-S1 levels. Four other lumbar devices are: ProDisc (Spine Solutions/Synthes) Maverick (Medtronic Sofamor Danek), Flexicore (SpineCore), Kineflex (SpinalMotion). (94) Arthroplasty has several advantages, such as the preservation of function and the decrease of pain. Arthroplasty may avoid the morbidity associated with fusions, but does it solve all the problems of degenerative disc disease. The indications are limited and longterm results have not yet been established.

Lumbar Spine Mirkovic et al., in Spine in 1995 discussed the Triangular Safe Zone, the Kambin triangle, which is the triangular space, within the intervertebral foramen, through which the working cannula can be introduced safely in lumbar posterolateral percutaneous procedures. The limits of the triangle are: - base: superior endplate of the inferior vertebra - height: lateral border of thecal sac - hipotenuse: spinal nerve The initial phase of percutaneous procedures are practically performed blind and the only radiographic references that we have are pedicle, vertebral body and disc space. That’s why, it’s very important to know the exact shape of the triangular safe zone and his relationship with the radiographic references in order to perform safely any percutaneous procedures. The problem of determining the exact shape, and the dimensions of the triangular safe zone and the largest safe working cannula diameter for passing within, has been faced by Pil Sun Choy in his thesis in São Paulo Medicine College in 2000 (95), to better understand the triangular safe zone. The study, has been conducted on fourteen fresh human cadavers of adult males average age: 52, studying one hundred triangular safe zone from L2 to S1. All the cadavers were dissected in same way, starting with the dissection of the posterior soft tissue of the lumbar spine, after this all the posterior osseous elements were removed. Finally the shape and the limits were determined and the triangular safe zones were measured. Choy underlines that the medial limit does not correspond to the medial border of the pedicle of the inferior vertebra.The conclusions of his study are that the limits of the triangle are : medial - lateral border of the dural sac, lateral - the spinal nerve and the inferior - superior end plate of inferior vertebral body. L2-L3 and L3-L4 were delineated

918 Spine approximately right-angled triangle, whereas in L4-L5 and L5-S1, obtuse-angled triangle dimensions of the side of the triangle increase progressively from L2-L3 to L5-S1admits progressively larger external diameter working cannula from L2-L3 to L5-S1.

Chemonucleolysis Chymopapain was discovered and isolated by Jansen and Balls in 1941 from the latex of the fruit of Carica papaya. By depolymerizing the proteoglycan and glycoprotein macromolecules of the nucleus pulposus, chymopapain can reduce the water content of the extracellular matrix of the nucleus pulposus and cause reductions in intervertebral disc height and bulge. In addition to reducing intradisc pressure, chymopapain may also have an antiinflammatory role in the nerve root itself. Watts (96) proposed that chymopapain interacts with the sensory fibers of the anulus to produce a total or partial neurectomy effect. The first clinical treatment of sciatica by using chymopapain was applied by Smith (97) in 1964. In the following three decades, chemonucleolysis was actively used to treat disc disease; however, controversial issues surrounding its safety and efficacy, arose despite the fact that it has the approval of the US Food and Drug Administration. Overall, the efficacy of chemonucleolysis was noted to be between 74 and 77% in several reports (98,99,100). The largest series was reported by Nordby and Javid (101) they published a 14-year study of 3000 patients and noted a success rate ranging between 82 and 87.2%. Other published outcome reports were inconclusive, however, and brought into question the safety and efficacy of chymopapain (100,102,103). Anaphylactic reactions to this substance can result in death. An inadvertent intrathecal chymopapain injection can cause hemiparesis or paraplegia, raised intracranial pressure, meningitis, and hemorrhage. A review of the literature nevertheless does reveal data supporting the continued use of chemonucleolysis for the treatment of lumbar disc herniations (104-108). Proper patient selection is crucial for success. Chemonucleolysis should be reserved for patients with radicular symptoms caused by a soft herniated disc as demonstrated by imaging studies. Patients older than 60 years of age may lack sufficient mucoprotein for hydrolysis and tend to respond poorly to this procedure (109). Absolute contraindications to chemonucleolysis include allergic reactions to papain, history of discitis, cauda equina syndrome, pregnancy, arachnoiditis, migrated discs, and canal stenosis.

Percutaneous Lumbar Discectomy A percutaneous nucleotomy technique involving a partial resection of the disc material via a posterolateral approach was first described in 1975 by Hijikata (110) The procedure was performed using local anesthesia. In 1983, Kambin and Gellman (111) performed a dorsolateral discectomy by inserting a Craig cannula and a small forceps into the disc space. In 1985, Onik and colleagues (112,113) introduced a nucleotome for PLD. In 1986, Kambin and Sampson (114) initiated the use of fluoroscopy for percutaneous discectomy. Instruments similar to those developed for ophthalmologists to remove the vitreous humor of the eye were redesigned for use in percutaneous discectomies; some flexibility was provided in order to approach the L5–S1 and L4–5 levels.

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

919

The procedure of percutaneous discectomy is most ideal for contained disc fragments, with the size of the protrusion being an important factor in obtaining successful outcomes (115). In addition, patients with narrowed disc spaces are also poor candidates for percutaneous discectomy. Automated PLD can be a treatment option for patients with single-level disc disease. It is not indicated for patients with a history of previous chemonucleolysis, surgical discectomy, progressive neurological deficits, sequestered disc fragments, spinal stenosis, or spondylolisthesis. Success rates reported in the literature range from 77.5 to 87% and the complication rate is 1% (116-119).

Percutaneous Laser-Assisted Discectomy The development of laser light amplification by stimulated emission of radiation dates back to 1958 and was accomplished by Arthur L. Schawlow and Charles H. Townes (120). Since then, numerous applications of laser technology in medicine have been reported in different specialties. After percutaneous placement of a single needle in the disc space, laser energy is passed through a fiber, which is introduced through the needle. The laser energy is transmitted in short bursts to avoid excessive heating of adjacent tissue. In 1984, Ascher and Heppner (121) used carbon dioxide and Nd lasers to treat lumbar disc disease. Their method involved measuring intradisc pressure before and after laser discectomy by using a saline manometer. These authors postulated that the removal of even a small volume of tissue from the disc caused a corresponding decrease in intradisc pressure, thus relieving back pain and inflammation. In 1990, Yonezawa, et al. (122) used an Nd–YAG laser to transmit energy through a double-lumen needle with a bare quartz fiber; their tip-type pressure transducer was similarly able to record intradisc pressure. The use of a KTP laser for lumbar disc ablation was introduced in 1992 (123). Recent advances have allowed the development of side-firing probes, which provide better directional control and visualization. The side-firing laser probe reduces the risk of injury to anterior structures such as the vena cava, aorta, and iliac vessels. Yeung (124) recommended injecting discs with indocyanine green to act as a chromophore, thus maximizing delivery and minimizing the chance of injury to adjacent structures. The holmium–YAG system involves a unique pulsed laser that enables the adjustment of pulse width and frequency to cause disc cavitation and reduce intradisc pressure while minimizing injury to adjacent structures. Overall, the combined results of several series demonstrated a 70 to 80% rate of long-lasting pain relief (121,125). The only reported complication was one case of discitis in a series of 333 procedures, which was described by Choy, et al. (126) Other possible complications of laser-assisted discectomy can include perforation of the aorta, vena cava, iliac vessels, or abdominal organs, and cauda equina syndrome. Obviously these are to be ascribed, more logically, to individual malpractice or occasional accidents, than to real complication of this technique. As such, the results of percutaneous laser discectomy for back and leg pain due to disc protrusions are still inconclusive. The largest experience in the literature, reported by Choy, et al. (126), documented a 78.4% success rate with a 26-month period follow up. Yeung (124) reported an 84% rate of good or excellent results with the KTP/532 device. On the other hand, Sherk and associates (127) observed no differences between treated and control groups in an analysis of

920 Spine responses to pain questionnaires or the presence of physical signs. Yeung and colleagues (128) published a retrospective review of 307 consecutive patients with lumbar disc herniation who were treated by posterolateral endoscopic laser discectomy. These authors showed satisfactory results in 89.3% of patients. The rate of response to the questionnaire was 91%. The responses indicated that 90.7% of the respondents were satisfied with their surgical outcomes and would undergo the same endoscopic procedure again if faced with a similar herniation in the future. Poor outcomes occurred in 10.7% of the primary group and in 9.7% of the group responding to the questionnaire. The combined major and minor complication rate was 3.5%.

Arthroscopic Microdiscectomy Kambin and Hijikata and their colleagues independently developed mechanical tools for percutaneous nucleotomy (120). Refinements of the method involved the use of an automated system (118,114,112). The instruments were designed to remove disc material from the center of the disc and to decrease the amount of nucleus pulposus posterolaterally. Subsequent developments led to the design of a 2.7-mm glass arthroscope combined with a videodiscoscope with a single working portal (129,130,131). The introduction of arthroscopic illumination and magnification allowed identification of the triangular working zone (111,112,129-131). Placement of the needle is confirmed with the aid of an intraoperative fluoroscope. Within the triangle, there is generally room for introduction of the coaxial instruments. The initial open procedure in which a tube is introduced posterolaterally was slowly replaced by a completely percutaneous operation in which a modified discoscope, working portals, and special instruments are used (120). The mechanism of pain relief after arthroscopic microdiscectomy and central nucleotomy is controversial, but the theory involves the reduction in intradisc pressure, removal of inflammatory agents, and reduction of tension on the nerve root. Additionally, the arthroscopic approach provides the opportunity to inspect the anulus, spinal nerve, and foramina. All intra-anular, subligamentous, and extraligamentous herniations are accessible via the arthroscopic microdiscectomy procedure. Nevertheless, sequestrated and migrated disc fragments cannot be safely removed using the arthroscopic microdiscectomy method. Kambin (129,130) reported an 87% successful outcome rate with arthroscopic microdiscectomy. Others reported similar successes with this procedure (132). Mayer and Brock, (133) in a paper on a prospective randomized control trial, achieved favorable outcomes with minimal complications. The reported complications in the literature included discitis, instrument breakage, and psoas hematomas; no neurovascular complications arising from posterolateral access to the intervertebral discs of the lumbar spine have been encountered. Proper patient selection makes arthroscopic microdiscectomy an attractive option as a sameday surgical procedure.

Lumbar MED Microsurgical discectomy has the ability to address concomitant pathological bone and

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

921

ligament conditions, and this is probably why it is still considered superior to percutaneos techniques. This is especially true when short term resultws are taken in consideration. The attempt to performe microdiscectomy minimizing muscle splitting, started with the use of a tubular retractor system for microdiscectomy, which was first developed in 1994. The system consists of a series of concentric dilators and thin-walled tubular retractors of variable length. The spine is accessed via serial dilation of the cleavage plane between the muscle fascicles. The midline supporting musculo-ligamentous structures are left intact using this technique. The MED system was introduced in 1997. The steep learning curve associated with the use of the endoscope for MED procedures initially deterred many surgeons. The lack of depth perception and stereoscopic visualization associated with the use of the endoscope compounded the steep learning curve of the procedure. The next generation of the MED system, called the METRx (Medtronic Sofamor Danek, Minneapolis, MN), provided increased working space and better illumination. Surgery can now be performed using the operating microscope, loupes, an endoscope, or a combination of techniques. Essentially, one can follow the same method as the open microdiscectomy. Surgeons can also treat free-fragment disc herniations as well as canal stenosis, conditions that were previously unaddressed by other percutaneous procedures. This procedure is performed also as a routine outpatient procedure without general anesthesia. Overall, indications for the use of the MED system are similar to conventional open procedures. Its applications have also been successfully performed in obese patients and in patients who have undergone previous spinal operations.

Lateral endoscopic surgery The concept that just the invasion of the spinal canal destabilises the spinal segment and creates scarring in and around sensitive spinal nerves, has brought dr Yeung to conceive an endoscopic posterolateral approach. By his system the epidural space is accessible with flexible instruments and special cannulas via the posterolateral port. Yeung Endoscopic Spine System (YESS™) includes a bevelled and slotted cannula which allows visualisation of the disc and epidural space at the same time, facilitating epidural surgery for the removal of subligamentous, extruded and sequestered disc fragments. The foramen can also be enlarged by foraminoplasty to decompress central and lateral recess stenosis. Foraminal osteophytes tethering the spinal nerves can be released. Adjuvant tools and therapies such as radio frequency, chymopapain and laser can be employed for tissue modulation or ablation when the visualised spinal pathology dictates its use. Even mild lateral recess and foraminal spinal stenosis in selected patients respond to foraminoplasty by endoscopic techniques. The technique of decompressing the traversing and exiting nerves is accomplished by resecting the ventral surface of the superior articular process (superior facet of the inferior vertebra). In lateral recess stenosis, a simple ablation of the facet capsule and attachment of the ligamentum flavum by resecting the tip of the superior articular process will decompress the exiting nerve. Decompression is confirmed by visualisation of perineural fat and pulsation of the epidural fat around the nerve. Resection of the bulging dorsal annulus will decompress the traversing nerve

922 Spine in central stenosis.

Electrothermal Therapy Intradiscal electrothermal coagulation is a therapeutic innovation specifically designed to treat discogenic pain since Saal and Saal (134) hypothesized that thermal energy might play a role in the treatment of internal disc disruption and thus chronic low-back pain. The most commonly used electrosurgery unit, the Ellman Surgitron IEC, produces ultrahigh-frequency radio-wave energy, which is delivered through modified monopolar and bipolar tools. The energy is filtered back to the electrosurgery unit without causing adjacent tissue damage (120). Intradiscal electrothermal coagulation requires percutaneously threading a flexible heating electrode into the disc, obtaining that the electrode passes circumferentially around the inner surface of the annulus. In the normal intervertebral disc, sensory nerves do not penetrate beyond the outer one third of the anulus fibrosus; in degenerative disc disease, however, new growing nerve fibers may pentrate deeper in the disc, resulting in new contribution to a painful sensation. The diagnosis of this condition is based largely on the patient’s medical history and on radiological findings. Intradiscal electrothermal therapy delivers targeted thermal energy designed to shrink collagen fibrils, cauterize granulation tissue, and coagulate nerve tissue in the posterior anulus fibrosus. Direct application of thermal energy to the intervertebral disc is thought to reduce discogenic pain either by thermal coagulation of nociceptors or by increasing the stability of the disc via contraction of collagen Type I fibers.

Nucleoplasty by coblation technique Percutaneous plasma radio-frequency-baed discectomy, or the Nucleoplasty procedure (ArthoCare, Sunnyvale, Calif), was initially used to treat symptomatic contained protrusion in the lumbar spine. This procedure was reported to be safe and was associated with acceptable clinical success. It is conducted by using a bipolar radio-frequency-based device, which functions via a plasma-mediated process, to perform precise removal of disk tissue. In this process, bipolar voltage pulses at 100 kHz are applied to the active electrode at the distal end of the device, which produces a strong electric field region around the electrode. The electrolytes in the surrounding conductive medium (eg; sodium ions resident within the nucleus pulposus) respond to the electric fields, and if the voltage is sufficiently large, a localized finely focused plasma field (ionized vapor) is produced between the elec-trode and adjacent tissue. The plasma field comprises a com-plex mixture of gas-phase radical chemically reactive and non--reactive molecules and a very small fraction of ionized particles (predominately positive ions and electrons), some of which can break molecular bonds in the adjacent tissue by energetic particle bombardment and chemical reactions. Usually, visible light emission are observed coincidentally with onset of the plasma formation. The organic molecules in the disk material (particularly long-chain molecules such as colla-gen and the like) are thought to be susceptible to fragmenta-tion by the plasma particles, resulting in their conversion into liquid and gaseous products that subsequently desorb from the targeted site. The net

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

923

result is a reduction of soft-tissue volume and effective excision of the soft tissue within the nu-cleus. The plasma radio-frequency-based process has been reported to have minimal histopathologic effect on tissue im-mediately adiacent to the treated site. Some clinical studies, as well as our large clinical experience, have confirmed that the indications to the procedure are disc protrusions and contained disc herniations both at lumbar and cervical level. (135-140) Integrity of the annulus is the essential point of definition of the indication to the treatment. It is demonstrated from the existing literature that the procedure is safe (141-144) has good clinical results, and can be justified as a means to shorten the painful incapacitating period of a disease that has a favorable longer term natural history for spontaneous resolution.

Ozone discolysis The mixture of oxygen and ozone is employed in medicine since thirties for the treatment of pain and dysfunction in patients affected by trombotic and hischemic diseases. At the beginning the benefit was attributed to an improvement of oxygenation of the area, and to the antiseptic properties of ozone. New and detailed studies have been moved by the empirical observation of the powerful and long lasting effect of the injection of this gas mixture in paravertebral muscles for treating pain and radicular dysfunction due to discal-radicular conflict. Researchers in different fields surprisingly noticed that a brief, calculated, oxidative stress by ozone administration, may correct a persistent imbalance due to excessive, chronic oxidative injury. It is becoming clear that modest, repeated ozone treatment increases the activity of superoxide dismutase, and other enzymes, inducing a state of oxidative stress adaptation, with very important therapeutic implications. (145) The gas mixture is produced by an apparatus (ozone generator) which activates the molecules of biatomic oxygen in a voltaic arch. Ultraviolet spectrophotometry allows a precise quantification of ozone percentages in the obtained mixture. Jacobs in 1982 has reported (146) the absence of side effects in over five million ozone therapy sessions for different pathologies. The paravertebral intramuscular treatment produces pain relief in the majority of patients, together with decongestion, reabsorption of oedema and increased mobility. This has brought to the idea of injecting the oxygen-ozone mixture in the intervertebral disc and in the conjugation foramen in order to obtain a powerful effect directly on the pathological mechanism. Large debate has developed in recent years on the technique which in several very large series (147-151) of patients has been reported to have a very significant clinical results both at the lumbar and cervical level. What is lacking is the understanding of the specific mechanism of action, and a complete long term follow-up of patients with randomized studies. These arguments are used by detractors to put in doubt the efficacy of the procedure, and episodical, exceptionally rare adverse reactions or complications are brought in great evidence. The proportion of these adverse reactions can be estimated about less than 0.1 % if a precise and careful medical procedure is performed. A major criticism is the fact that often the injection is performed by unprepared and low-cultured practicioners, and this fact may increase significantly the percentace of adverse effects.

924 Spine A more refined and univocal procedure, with precise definition and recording of doses, and standardisation of the technique is undoubtly needed, but recently several groups have published detailed analysis of large casuistics with quite positive results.

Endoscopic Lumbar Peridurolysis Epidural fibrosis with or without adhesive arachnoiditis most commonly occurs as a complication of spinal surgery and may be included under the diagnosis of “failed back syndrome”. Both result from manipulation of the supporting structures of the spine. Epidural fibrosis can occur in isolation, but adhesive arachnoiditis is rarely present without associated epidural fibrosis. Arachnoiditis is most frequently seen in patients who have undergone multiple surgical procedures. Both conditions are related to inflammatory reactions that result in the entrapment of nerves within dense scar tissue, increasing the susceptibility of the nerve root to compression or tension. The condition most frequently involves the nerves within the lumbar spine and cauda equina. Signs and symptoms indicate the involvement of multiple nerve roots, and include low back pain, radicular pain, tenderness, sphincter disturbances, limited trunk mobility, muscular spasm or contracture, and motor sensory and reflex changes. Typically, the pain is characterized as constant and burning. In some cases the pain and disability are severe, leading to analgesic dependence and chronic invalidism. Endoscopic Lumbar Peridurolysis is a minimally invasive approach which was conceived for the diagnosis and treatment of chronic low back pain and radiculopathy, due to the relevant problems posed by patients affected by idiopatic lumbalgia and from failed back surgery syndrome. Epidurolysis procedure is used to loosen and dissolve some of the scar tissue from around entrapped nerves in the epidural space of spine, so that medications such as cortisone can reach the affected areas, and so that scar tissue is less painful. Scarring is most commonly caused from bleeding into the Epidural space following back surgery and the subsequent healing process. It is a natural occurrence following surgical intervention. Sometimes scarring can also occur when a disk ruptures and its contents leak out. Endoscopic Lumbar Peridurolysis may be performed both for diagnostic and for therapeutic proposals. The technique was described the first time by Dr. Michael Burman in 1931. Several attempts have been performed through the years, but serious technical obstacles existed to the advancement of Spinal Endoscopy: the endoscopes where too large, where straight, where rigid, had poor lighting. Furthermore there where no means of capturing an image. The possibilities of developing the technique came along when flexible endoscopes have been produced. At present the operation is performed by a flexible fiberoptic scope which is 0.9 mm in diameter. The apparatus employes hjgh resolution optics and has a wide field of view. This flexible scope has the characteristic of steerability, is connected to a fiberoptic light source, is introduced and guided by a single use catheter (Mylotech Epiduroscopy Video Guided Catheter) 3 mm diameter. The system allows image retrieval, and mechanic treatment of fibrosis by side to side movement, and irrigation and operative ports. The access to the spinal canal is the sacral hiatus, through the yellow ligament,

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

925

between sacrum an coccyx. This way of penetration is fairly straight from the insertion site to the pathology, which we know to be located in the lumbar area. The technique allows for multi-segmental examination and treatment. Accessing through a site remote from the pathology will allow scar debridment without producing a new local bleeding, and thereby a new scar.The action is mechanical separation of fibrotic adhesions, and the specific medical treatment of the inflamed area. The therapeutic maneuvers distend the epidural space with normal saline, which may be administered either in continuous flush, or by syringe injection. The distention of the epidural space will open tissue planes to reduce epidural congestion and tethering, disrupt anatomical and pathological formations that may block penetration of medications.The therapeutic agents we have employed are steroids, hyaluronidase, opiates and anesthetics. The pressure of injection through the syringe is very mild, anyway the patient may report pressure, paresthesia, or may complain of headache, ear pressure, neck or shoulder pain. Potential side effects are: pain at insertion site; headache during and following the procedure; small amounts of drainage from insertion site. Possible complications described in the literature are macular hemorrhage; epidural abscess and/or infection; numbness, tingling, dysesthesia. Several Authors , as Richardson, Raffaeli, Alexandre and coworkers, Van Seventer, Fernandez Molina, Reverberi and coworkers, reported good results in pain management of FBSS patients (152). Since these are patients who hardly benefit from other treatments, this technique appears to be an interesting means of clinical management.

Vertebroplasty and Kyphoplasty With the same principle as for treatments of disc pathology, treatments have been conceived for curing vertebral body lesions without open surgery., minimally invasive vertebroplasty involves the percutaneous injection of PMMA into a fractured vertebral body. It was developed in France in the late 1980s (153). Although this does not pretend to reexpand a collapsed vertebra, it reinforces and stabilizes the fracture, which alleviates pain. The procedure was first used to treat aggressive vertebral hemangiomas (153) and was later applied to other lesions that weaken the vertebral body, including osteolytic metastases (154,157), and osteoporotic vertebral collapse. Although the European experience with vertebroplasty in the setting of spinal metastases and myeloma is more extensive, indications for treatment in North America are currently heavily weighted toward osteoporotic bone disease. Percutaneous balloon kyphoplasty is a modification of the vertebroplasty method and involves inflation of a balloon within a collapsed vertebral body, to restore height and reduce kyphotic deformity, followed by stabilization with PMMA. The risk of cement extravasation is theoretically reduced because the balloon creates a void within the vertebral body into which cement can be injected under relatively low pressure. In addition to PMMA and bone mineral cement, several alternative biological materials have been used in attempts to augment compromised vertebral bodies. The efficacy of osteoinductive growth factors (transforming growth factor-β, BMP-2, and BMP-7) in enhancing arthrodesis is currently being studied.

926 Spine

Image-Guided Surgery Since its introduction, transpedicular screw fixation has been extensively used in various spinal disorders to promote fusion and stabilization. Screw misplacement can lead to undesirable neurovascular complications. Pedicle screw placement in patients with deformities carries an even greater risk of serious complications. Weinstein and coworkers (158) reported perforation of the cortex due to pedicle screws in close to 20% of these cases. To increase the accuracy of screw placement, various methods have been used to target the pedicle more effectively with respect to the trajectory and the depth of screw placement. Image-guided systems are widely used in intracranial surgery and have been adapted to assist with screw placement since the mid-1990s. (159,160) The use of image-guided systems for pedicle screw placement has improved the accuracy of the placement. The system relies on precise localization of the pedicles by using CT scanning. Furthermore, by replacing direct visualization with radiographic visualization, it has enabled a reduction in sugical exposure, duration, and blood loss. Foley, et al. (161) described “virtual fluoroscopy” and its successful use in various spinal procedures including pedicle screw insertion, interbody cage placement, odontoid screw insertion, and atlantoaxial transarticular screw fixation. Nolte and associates (160) described the principles of computer-assisted pedicle screw fixation. An infrared camera was used to track specific instruments that were equipped with light-emitting diodes. The dynamic reference was fixed to the spinous process of the vertebra to receive instrumentation. Normal bone landmarks and their correlations with images confirmed the calibration accuracy. Using that computerized system, Nolte, et al., (160) reported a pedicle screw misplacement rate of 4.3% under clinical conditions. In contrast, Choi, et al., (162) reported the use of computer-assisted fluoroscopic targeting for pedicle screw fixation. The authors compared the accuracy of pedicle screw placement accompanied by the fluoroscopy-guided system with the image-guided system and observed no significant differences. Recent development of isocentric C-arm fluoroscopy, in which CT images are generated with the aid of an intraoperative fluoroscope, may offer another means of threedimensional navigation by using a two-dimensional intraoperative imaging source. With increasing familiarity, image-guided surgery will be a very useful adjunct to the further development of minimally invasive surgery.

Lumbar Fusion Laparoscopic Anterior LIF Anterior lumbar fusion was initially described by Burns (163) in 1933 for the treatment of spondylolisthesis. In 1991, Obenchain first described the laparoscopic approach to the lumbar spine for discectomy (120). In 1995, Mathews, et al. (164) and Zucherman et al. (165) described the technique in detail and published preliminary outcome data for laparoscopic anterior lumbar fusion (Fig. 3). In 1999, Regan and associates (166) published a prospective study in which open and laparoscopic methods of anterior lumbar fusion were compared. They demonstrated that patients who

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

927

underwent the laparoscopic procedure had a shorter hospital stay and reduced blood loss, but an increased operative time. Operative time shortened in patients who underwent the laparoscopic procedure as surgeons’ experiences increased. Operative complications were comparable in both groups, with an occurrence of 4.2% in those in whom the open approach was used and 4.9% in those in whom the laparoscopic approach was used. Overall, the device-related rate of repeated surgery was higher in the laparoscopy group (4.7% compared with 2.3%), primarily as a result of intraoperative disc herniation. Conversion to an open procedure in patients who initially were treated laparoscopically was 10%. Authors of a more recent study did not favor the video-assisted laparoscopic approach. Escobar, et al. (167) revealed that the highest incidence of complications occurred in video-assisted laparoscopic approaches. Complications are primarily related to surgical exposure of the anterior spine, which can include damage to important vascular structures, the sympathetic plexus, or the abdominal viscera.

Posterior and Transforaminal LIFs The concept of LIF, as initially described by Cloward in 1951, offers several advantages over traditional posterolateral arthrodesis, including a rich blood supply from the cancellous fusion bed, a load-bearing force occurring through the fusion bed, the ability to distract the disc space and neuroforamina, and the ability to restore segmental lordosis. Traditional open posterior LIF procedures have been reported to yield successful outcomes in approximately 80% of patients with fusion rates near 90%. Since 2000, minimally invasive posterior LIF procedures have been performed to reduce iatrogenic injury, which can be incurred during the exposure process of the open procedure . Longterm follow-up data are lacking, but retrospective reviews of minimally invasive posterior LIF performed with the aid of the microscope, premachined bone graft or cages, a virtual fluoroscope, and a percutaneous pedicle screw system were reported to yield clinical improvement more than 1 year postoperatively, which is comparable to the outcomes of an open procedure (161,168). Transforaminal LIF, a unilateral posterior approach for achieving an interbody arthrodesis, has gained recent popularity. The disc interspace is accessed by performing a unilateral facetectomy. Retraction of the nerve root is kept to a minimum, allowing for safer placement of the interbody graft. Placement of a premachined bone graft or cage supplemented with BMP can obviate the need for local harvesting of an autograft. Supplemental percutaneous pedicle fixation is added for completion of the transforaminal LIF procedure. The unilateral transforaminal LIF approach for interbody fusion offers several advantages over the posterior LIF procedure. Retraction of the nerve root and dura mater is minimized, because of the lateral entry point, and this reduces the risk of neural injury. This lateral entrance into the disc space also makes revision surgeries less difficult, because there is less need to mobilize nerve roots that may be surrounded by epidural scar tissue. A potential disadvantage of unilateral transforaminal LIF is that direct nerve root decompression can only be performed unilaterally. With the increasing use of the tubular retractor system, however, bilateral foraminal decompression can be achieved via a unilateral approach, as previously described.

928 Spine

Interspinous Distraction Devices (Spacers) Surgical decompression with or without fusion is the standard surgical treatment for patients with moderate to severe lumbar spinal stenosis, which is generally associated with degeneration of the intervertebral disc and loss of disc height. The procedure is maintained to be indicated of patients over 65, or affected by very severe stenosis. Lumbar interspinous process decompression (IPD), also known as interspinous distraction or posterior spinal distraction, has been proposed as a minimally invasive alternative to laminectomy and fusion. In IPD an interspinous distraction implant, also called a spacer, is inserted between the spinous processes through a small (4–8 cm) incision. The supraspinous ligament is maintained and assists in holding the implant in place. No laminotomy, laminectomy or foraminotomy is performed. The device is intended to restrict painful motion while enabling otherwise normal motion. The implant theoretically enlarges the neural foramen, decompresses the cauda equina and acts as a spacer between the spinous processes to maintain the flexion of the spinal interspace. Several IPD devices, also called spacers, have been investigated (e.g., X STOP®, Wallis®, Minns, Coflex™ (formerly Intraspinous U), DIAM™, BioFLex System with Nitinol implants). The X STOP® Interspinous Process Decompression System (Kyphon, Inc., St. Francis Medical Technologies, Inc.) is the only IPD system that has received clearance from the U.S. Food and Drug Administration (FDA). The FDA-labeled indication for the device is treatment of patients aged 50 or older suffering from neurogenic intermittent claudication secondary to a confirmed diagnosis of lumbar spinal stenosis with X-Ray, MRI or CT evidence of thickened ligamentum flavum, narrowed lateral recess and/or central canal narrowing. The ligamentum flavum thickening is to be considered a pseudo-hypertrophy (169). The X STOP® is indicated for those patients with moderately impaired physical function who experience relief in flexion from their symptoms of leg/buttock/groin pain with or without back pain and have undergone a regimen of at least six months of nonoperative treatment. The device is approved for implantation at one or two lumbar levels in patients in whom operative treatment is indicated at no more than two levels. The Wallis® System (Abbott Spine) was introduced in Europe in 1986. The first generation Wallis® implant was a titanium block, the second generation device is composed of a plastic-like polymer that is inserted between adjacent processes and held in place with a flat cord that is wrapped around the upper and lower spinous processes. The Wallis® System is currently being tested in a FDA-regulated clinical trial. Also in a FDA-regulated clinical trial is the DIAM™ Spinal Stabilization System (Medtronic Sofamor Danek), which is a soft interspinous spacer with a silicone core. The DIAM™ system does not require removal of the interspinous ligament and is secured with laces around the upper and lower spinous processes. The Coflex™ implant (Paradigm Spine) and the ExtendSure and CoRoent (both from NuVasive) are used in Europe but are not currently FDA approved. Proponents of IPD list the advantages of IPD compared with standard surgical decompression techniques to be the option of local anesthesia, shorter hospital stay and rehabilitation period, preservation of local bone and soft tissue, reduced risk of epidural

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

929

scarring and cerebrospinal fluid leakage and reversibility that does not limit any future treatment options. New devices are now available, which are inserted with a quite reduced incision and muscular disinsertion and retraction. The principle of maintaining the supraspinous ligament integrity seems to be foundamental, and thereby lateral approaches are to be preferred. A quite interesting new option is the Spinex® device, which is inserted through a small lateral working channel, is single-shape and can be expanded once located, apting it to the specific situation of the patient. The potential complications of IPD are implant dislodgement, incorrect positioning of implant, fracture of the spinous process, foreign body reaction (e.g., allergic reaction to titanium alloy) and mechanical failure of the implant. A new kind of intervertebral spacer is the Percudin® system, consisting in bilateral transpedicular screws, with a conic head, wich will lift the overlying articular facet.

Cervical Spine Also in the cervical area intradiscal techniques are used in order to modify the discal morphology and to correct disco-radicular conflict. So several papers have been published on the use of laser, coblation and ozone , by the anterior approach to discs from C3 to C7. Results seem to be attractive, even better than in the lumbar area, and side effects really minimal.

Cervical Microendoscopic Discectomy The anterior approach to the cervical spine has become increasingly popular, but the posterior cervical discectomy technique, as described by Scoville and associates (170) has a place in relieving radicular pain and avoids the need for a fusion. In selected patients with laterally herniated disc fragments, isolated foraminal narrowing, multilevel foraminal narrowing without central stenosis, or continued nerve root symptoms after anterior cervical discectomy and fusion, a posterior cervical approach will be necessary.The disadvantage of the standard posterior approach, however, is significant paraspinous muscle dissection, postoperative axial neck pain, potential instability, and subsequent deformity. Roh, et al. (171) performed posterior cervical foraminotomies by using either the MED system or conventional open techniques in four cadaveric specimens. They were able to demonstrate greater decompression by using the MED procedure and showed the possibility of minimally invasive cervical foraminal decompression and discectomy. Adamson (172) described microendoscopic posterior cervical laminoforaminotomy for unilateral radiculopathy.

Minimally Invasive Cervical Laminoplasty Expansile laminoplasty has been successfully used to treat cervical myelopathy that is attributable to canal stenosis; however, detachment of the posterior cervical muscles is thought to contribute to postoperative axial neck pain and kyphosis. Minimizing the amount of muscular dissection might reduce the likelihood of these sequelae. Wang and

930 Spine associates (173) assessed the feasibility of a minimally invasive laminoplasty technique by applying it to cadaveric spines. A 22-mm tubular dilator port was used to access lamina–facet junctions from C-2 to C-7 through bilateral stab incisions, made at C4-5 and C5-6. Troughs at the lamina–facet junctions were drilled bilaterally and the contiguous laminae were lifted en bloc from one side. Ten-millimeter rib allograft spacers were inserted to maintain a gap on the open side. Exposure of six cervical levels can be accomplished by creating two small incisions on each side. The diameter of the midsagittal spinal canal was increased by a mean of 38% and the area of the spinal canal was increased by an average of 43% at the level of C-5.

Conclusions The rapid technological advancements of the last two decades have made minimal access surgery possible. Virtually, all aspects of the spinal axis can be approached and treated in a minimally invasive approach (174). Core to the concept of minimally invasive surgery is the reduction of iatrogenically induced injury while achieving the goals of the surgery. With the innovation of better optics and video equipment, retractor and instrumentation systems, image guidance systems, and new biological agents, the majority of traditional “open” spinal procedures can now be performed in a minimalistic way. Biochemical aspects of pain generation and nerve dysfunction are not yet completely understood, and neuroradiological investigations compared to clinical data teach us that a precise etiological diagnosis is often very difficult. Many new treatments deal with the functional more than with the morphological aspects of the problem. For most minimally invasive surgical procedures, however, long-term prospective controlled data are still lacking. In addition, the use of new technology will require a new learning curve that may be discomforting for many surgeons. Special skills may be needed that are beyond those of traditional open surgery. And open minded attitudes are needed. Surgeons should also keep in mind that a failure of open surgery constitutes the FBSSyndrome, while a failure of minimally invasive techniques rarely engenders new iatrogenic problems. With the resource of the Internet, patients are becoming increasingly informed. It will be advantageous for practicing surgeons to be knowledgeable of available minimally invasive procedures and their outcomes in the course of their patient consultation. The goals of minimally invasive surgery are quite laudable; and we must face the increasing demand of well informed patients, who are more and more attentive to their quality of life.

LITERATURE 1- An HS, Anderson PA, Haughton VM, et al. Introduction: disc degeneration: Summary. Spine 2004;29:2677-8. 2- Adams M A., Roughley P. J.: What is Intervertebral Disc Degeneration, and What Causes It? Spine. 2006;31(18):2151-2161 3- McDevitt CA.: Ghosh P, ed. Biology of the Intervertebral Disc. Boca Raton, FL: CRC Press; 1988:151-70 4- Watanabe H, Yamada Y, Kimata K. Roles of aggrecan, a large chondroitin sulfate proteoglycan, in cartilage structure and function. J Biochem (Tokyo) 1998;124:687-93.

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

931

5- Nerlich AG, Weiler C, Weissbach S, et al. Age-associated changes in the cell density of the human lumbar intervertebral disc. Presented at: The 51st Annual Meeting of the Orthopaedic Research Society; Feb 20-23, 2005; Washington, DC 6- Urban JP, Smith S, Fairbank JC. Nutrition of the intervertebral disc. Spine 2004;29:27009. 7- Setton LA, Chen J. Cell mechanics and mechanobiology in the intervertebral disc. Spine ‘04;29:2710-23. 8- Horner HA, Urban JP. 2001 Volvo Award Winner in Basic Science Studies: Effect of nutrient supply on the viability of cells from the nucleus pulposus of the intervertebral disc. Spine 2001;26:2543-9. 9- Rajasekaran S, Naresh Babu J, Arun R, et al. ISSLS prize winner. A study of diffusion in human lumbar discs. Spine 2004;29:2654-67. 10- Visse R, Nagase H. Matrix metalloproteinases and tissue inhibitors of metalloproteinases: Structure, function, and biochemistry. Circ Res 2003;92:827-39. 11- Mott JD, Werb Z. Regulation of matrix biology by matrix metalloproteinases. Curr Opin Cell Biol 2004;16:558-64. 12- Duffy MJ, Lynn DJ, Lloyd AT, et al. The ADAMs family of proteins: From basic studies to potential clinical applications. Thromb Haemost 2003;89:622-31. 13- Tang BL. ADAMTS: A novel family of extracellular matrix proteases. Int J Biochem Cell Biol ‘01;33:33-44. 14- Porter S, Clark IM, Kevorkian L, et al. The ADAMTS metalloproteinases. Biochem J 2005;386:15-27. 15- Roberts S, Caterson B, Menage J, et al. Matrix metalloproteinases and aggrecanase: Their role in disorders of the human intervertebral disc. Spine 2000;25:3005 16- Goupille P, Jayson MI, Valat JP, et al. Matrix metalloproteinases: The clue to intervertebral disc degeneration? Spine 1998;23:1612 17- Antoniou J, Steffen T, Nelson F, et al. The human lumbar intervertebral disc: Evidence for changes in the biosynthesis and denaturation of the extracellular matrix with growth, maturation, ageing, and degeneration. J Clin Invest 1996;98:996 18- Adams MA, Dolan P. Could sudden increases in physical activity cause degeneration of intervertebral discs? Lancet 1997;350:734-5 19- Adams MA, Hutton WC. Prolapsed intervertebral disc. A hyperflexion injury 1981 Volvo Award in Basic Science. Spine 1982;7:184-91 20- Kang JD, Georgescu HI, McIntyre-Larkin L, et al. Herniated lumbar intervertebral discs spontaneously produce matrix metalloproteinases, nitric oxide, interleukin-6, and prostaglandin E2. Spine 1996;21:271-7. 21- Nerlich AG, Schleicher ED, Boos N. 1997 Volvo Award winner in basic science studies. Immunohistologic markers for age-related changes of human lumbar intervertebral discs. Spine 1997;22:2781-95. 22- Weiler C, Nerlich AG, Zipperer J, et al. 2002 SSE Award Competition in Basic Science: Expression of major matrix metalloproteinases is associated with intervertebral disc degradation and resorption. Eur Spine J 2002;11:308-20. 23- Duance VC, Crean JK, Sims TJ, et al. Changes in collagen cross-linking in degenerative disc disease and scoliosis. Spine 1998;23:2545-51. 24- Gruber HE, Hanley EN Jr. Ultrastructure of the human intervertebral disc during aging and degeneration: Comparison of surgical and control specimens. Spine 2002;27:798-805. 25- Melrose J, Ghosh P, Taylor TK, et al. A longitudinal study of the matrix changes induced in the intervertebral disc by surgical damage to the annulus fibrosus. J Orthop Res 1992;10:665-76 26- Kaigle AM, Holm SH, Hansson TH. 1997 Volvo Award winner in biomechanical

932 Spine

2728293031323334353637383940 4142434445464748-

studies. Kinematic behavior of the porcine lumbar spine: A chronic lesion model. Spine 1997;22:2796-806. Roughley PJ. Biology of intervertebral disc aging and degeneration: Involvement of the extracellular matrix. Spine 2004;29:2691-9. Verzijl N, DeGroot J, Thorpe SR, et al. Effect of collagen turnover on the accumulation of advanced glycation end products. J Biol Chem 2000;275:39027-31. Bradford DS, Oegema TR Jr, Cooper KM, et al. Chymopapain, chemonucleolysis, and nucleus pulposus regeneration. A biochemical and biomechanical study. Spine 1984;9:135-47. Adams MA, Freeman BJ, Morrison HP, et al. Mechanical initiation of intervertebral disc degeneration. Spine 2000;25:1625-36. Buckwalter JA. Aging and degeneration of the human intervertebral disc. Spine 1995;20:1307-14. DeGroot J, Verzijl N, Wenting-Van Wijk MJ, et al. Accumulation of advanced glycation end products as a molecular mechanism for aging as a risk factor in osteoarthritis. Arthritis Rheum 2004;50:1207-15. Boos N, Weissbach S, Rohrbach H, et al. Classification of age-related changes in lumbar intervertebral discs: 2002 Volvo Award in basic science. Spine 2002;27:2631-44. Adams MA, Dolan P, Hutton WC. The stages of disc degeneration as revealed by discograms. J Bone Joint Surg Br 1986;68:36-41. Maeda S, Kokubun S. Changes with age in proteoglycan synthesis in cells cultured in vitro from the inner and outer rabbit annulus fibrosus. Responses to interleukin-1 and interleukin-1 receptor antagonist protein. Spine 2000;25:166-9. Hirsch C, Schajowicz F. Studies on structural changes in the lumbar annulus fibrosus. Acta Orthop Scand 1953;22:184-231. Goel VK, Monroe BT, Gilbertson LG, et al. Interlaminar shear stresses and laminae separation in a disc. Finite element analysis of the L3-L4 motion segment subjected to axial compressive loads. Spine 1995;20:689-98. Osti OL, Vernon-Roberts B, Moore R, et al. Annular tears and disc degeneration in the lumbar spine. A post-mortem study of 135 discs. J Bone Joint Surg Br 1992;74:678-82. Hilton RC, Ball J. Vertebral rim lesions in the dorsolumbar spine. Ann Rheum Dis 1984;43:302-7. Adams MA, Bogduk N, Burton K, et al. The Biomechanics of Back Pain. Edinburgh, UK: Churchill Livingstone; 2002 Jensen MC, Brant-Zawadzki MN, Obuchowski N, et al. Magnetic resonance imaging of the lumbar spine in people without back pain. N Engl J Med 1994;331:69-73. Vernon-Roberts B, Fazzalari NL, Manthey BA. Pathogenesis of tears of the anulus investigated by multiple-level transaxial analysis of the T12-L1 disc. Spine 1997;22:26416. Twomey L, Taylor J. Age changes in lumbar intervertebral discs. Acta Orthop Scand 1985;56:496-9. Holm S, Holm AK, Ekstrom L, et al. Experimental disc degeneration due to endplate injury. J Spinal Disord Tech 2004;17:64-71. Adams MA, McNally DS, Dolan P. ‘Stress’ distributions inside intervertebral discs. The effects of age and degeneration. J Bone Joint Surg Br 1996;78:965-72. Sato K, Kikuchi S, Yonezawa T. In vivo intradiscal pressure measurement in healthy individuals and in patients with ongoing back problems. Spine 1999;24:2468-74. Brinckmann P, Grootenboer H. Change of disc height, radial disc bulge, and intradiscal pressure from discectomy. An in vitro investigation on human lumbar discs. Spine 1991;16:641-6. Pollintine P, Przybyla AS, Dolan P, et al. Neural arch load-bearing in old and degenerated

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

933

spines. J Biomech 2004;37:197-204. 49- Videman T, Battie MC, Gill K, et al. Magnetic resonance imaging findings and their relationships in the thoracic and lumbar spine. Insights into the etiopathogenesis of spinal degeneration. Spine 1995;20:928-35. 50- Bogduk N. The innervation of the intervertebral discs. In: Boyling JD, Palastanga N, eds. Grieve’s Modern Manual Therapy-The Vertebral Column. Edinburgh, UK: Churchill Livingstone; 1994-. 51- Freemont AJ, Peacock TE, Goupille P, et al. Nerve ingrowth into diseased intervertebral disc in chronic back pain. Lancet 1997;350:178-81. 52- Palmgren T, Gronblad M, Virri J, et al. An immunohistochemical study of nerve structures in the anulus fibrosus of human normal lumbar intervertebral discs. Spine 1999;24:2075-9. 53- Fagan A, Moore R, Vernon Roberts B, et al. ISSLS Prize Winner: The innervation of the intervertebral disc: A quantitative analysis. Spine 2003;28:2570-6. 54- Kuslich SD, Ulstrom CL, Michael CJ. The tissue origin of low back pain and sciatica: A report of pain response to tissue stimulation during operations on the lumbar spine using local anesthesia. Orthop Clin North Am 1991;22:181-7. 55- McNally DS, Shackleford IM, Goodship AE, et al. In vivo stress measurement can predict pain on discography. Spine 1996;21:2580-7. 56- Chen C, Cavanaugh JM, Song Z, et al. Effects of nucleus pulposus on nerve root neural activity, mechanosensitivity, axonal morphology, and sodium channel expression. Spine 2004;29:17-25. 57- Videman T, Battie MC, Gibbons LE, et al. Associations between back pain history and lumbar MRI findings. Spine 2003;28:582-8. 58- Hassett G, Hart DJ, Manek NJ, et al. Risk factors for progression of lumbar spine disc degeneration: The Chingford Study. Arthritis Rheum 2003;48:3112-7. 59- Moneta GB, Videman T, Kaivanto K, et al. Reported pain during lumbar discography as a function of anular ruptures and disc degeneration. A re-analysis of 833 discograms. Spine 1994;19:1968-74. 60- Videman T, Nurminen M. The occurrence of anular tears and their relation to lifetime back pain history: A cadaveric study using barium sulfate discography. Spine 2004;29:2668-76. 61- Schwarzer AC, Aprill CN, Derby R, et al. The prevalence and clinical features of internal disc disruption in patients with chronic low back pain. Spine 1995;20:1878-83. 62- Hamanishi C, Kawabata T, Yosii T, et al. Schmorl’s nodes on magnetic resonance imaging. Their incidence and clinical relevance. Spine 1994;19:450-3. 63- Boos N, Rieder R, Schade V, et al. 1995 Volvo Award in clinical sciences. The diagnostic accuracy of magnetic resonance imaging, work perception, and psychosocial factors in identifying symptomatic disc herniations. Spine 1995;20:2613-25. 64- Takahashi M, Haro H, Wakabayashi Y, et al. The association of degeneration of the intervertebral disc with 5a/6a polymorphism in the promoter of the human matrix metalloproteinase-3 gene. J Bone Joint Surg Br 2001;83:491-5. 65- Le Maitre CL, Freemont AJ, Hoyland JA. Localization of degradative enzymes and their inhibitors in the degenerate human intervertebral disc. J Pathol 2004;204:47-54. 66- Le Maitre CL, Freemont AJ, Hoyland JA. The role of interleukin-1 in the pathogenesis of human intervertebral disc degeneration. Arthritis Res Ther 2005;7:R732-45. 67- Riley GP, Curry V, DeGroot J, et al. Matrix metalloproteinase activities and their relationship with collagen remodelling in tendon pathology. Matrix Biol 2002;21:18595. 68- Anderson DG, Li X, Tannoury T, et al. A fibronectin fragment stimulates intervertebral disc degeneration in vivo. Spine 2003;28:2338-45.

934 Spine 69- Nissi MJ, Toyras J, Laasanen MS, et al. Proteoglycan and collagen sensitive MRI evaluation of normal and degenerated articular cartilage. J Orthop Res 2004;22:557-64. 70- Battie MC, Videman T, Parent E. Lumbar disc degeneration: Epidemiology and genetic influences. Spine 2004;29:2679-90. 71- Johnson WE, Caterson B, Eisenstein SM, et al. Human intervertebral disc aggrecan inhibits nerve growth in vitro. Arthritis Rheum 2002;46:2658-64. 72- Johnson WE, Caterson B, Eisenstein SM, et al. Human intervertebral disc aggrecan inhibits endothelial cell adhesion and cell migration in vitro. Spine 2005;30:1139-47. 73- Ishihara H, McNally DS, Urban JP, et al. Effects of hydrostatic pressure on matrix synthesis in different regions of the intervertebral disk. J Appl Physiol 1996;80:839-46. 74- Fardon DF. Nomenclature and classification of lumbar disc pathology. Spine 2001;26:461-2. 75- Roberts S; Evans H; Trivedi J; Menage J,: Histology and pathology of the human intervertebral disc.J Bone Joint Surg Am. 2006; 88 Suppl 2:10-4 76- Modic MT, Steinberg PM, Ross JS, Masaryk TJ, Carter JR. Degenerative disk disease: assessment of changes in vertebral body marrow with MR imaging. Radiology. 1988 Jan;166(1 Pt 1):193-9. 77- R. Rahme, R. Moussa. The Modic Vertebral Endplate and Marrow Changes: Pathologic Significance and Relation to Low Back Pain and Segmental Instability of the Lumbar Spine. AJNR Am J Neuroradiol. 2008 May;29(5):838-42. 78- Braithwaite I, White J, Saifuddin A, Renton P, Taylor BA. Vertebral end-plate (Modic) changes on lumbar spine MRI: correlation with pain reproduction at lumbar discography. Eur Spine J. 1998;7(5):363-8. 79- Kjaer P, Korsholm L, Bendix T, Sorensen JS, Leboeuf-Yde C. Modic changes and their associations with clinical findings. Eur Spine J. 2006 Sep;15(9):1312-9. Epub 2006 Aug 9. 80- Albert HB, Manniche C. Modic changes following lumbar disc herniation. Eur Spine J. 2007 Jul;16(7):977-82. 81- Thompson KJ, Dagher AP, Eckel TS, Clark M, Reinig JW. Modic changes on MR images as studied with provocative diskography: clinical relevance--a retrospective study of 2457 disks. Radiology. 2009 Mar;250(3):849-55. 82- Kuisma M, Karppinen J, Niinimäki J, Kurunlahti M, Haapea M, Vanharanta H, Tervonen O. A Three-Year Follow-up of Lumbar Spine Endplate (Modic) Changes. Spine. 2006;31(15):1714-1718. 83- Prevalence of MODIC Changes in Subjects With and Without Low Back Pain. This study is currently recruiting participants. www.clinicaltrials.gov. 84- Merskey H, Bogduk N (eds): Classification of Chronic Pain: Descriptions of Chronic Pain Syndromes and Definition of Pain Terms, ed 2. Seattle: IASP Press, 1994, p 178 85- Frank J. Tomecek, M.D., C. Scott Anthony, M.D., Chris Boxell, M.D., and Jennifer Warren, C.N.S Discography Interpretation and Techniques in the Lumbar Spine. Neurosurg Focus 13(2), 2002. 86- Lutz GE, Vad VB, Wisneski RJ. Fluoroscopic transforaminal lumbar epidural steroids: an outcome study. Arch Phys Med Rehabil. Nov 1998;79(11):1362-6 87- Botwin KP, Gruber RD, Bouchlas CG, et al. Complications of fluoroscopically guided caudal epidural injections. Am J Phys Med Rehabil. Jun 2001;80(6):416-24 88- Riew KD, Yin Y, Gilula L. Can nerve root injections obviate the need for operative treatment of lumbar radicular pain? A prospective randomized, controlled, double blind study. Presented at: NASS 14th Annual Meeting Proceedings. 1999;Chicago. 89- Rhee JM, Schaufele M, Abdu WA. Radiculopathy and the herniated lumbar disc. Controversies regarding pathophysiology and management. J Bone Joint Surg Am. Sep 2006;88(9):2070-80

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

935

90- Barre L, Lutz GE, Southern D, et al. Fluoroscopically guided caudal epidural steroid injections for lumbar spinal stenosis: a retrospective evaluation of long term efficacy. Pain Physician. Apr 2004;7(2):187-93 91- Chen B., Foye P.M., Castro C.P., Mehnert M.J: Epidural steroid injections, e-medicine, sept.19, 2007 92- Caspar W: A new surgical procedure for lumbar disc herniation causing less tissue damage through a microsurgical approach. Adv Neurosurg 4:74–80, 1977 93- Vernengo J, Fussell GW, Smith NG, Lowman AM: Evaluation of novel injectable hydrogels for nucleus pulposus replacement. J Biomed Mater Res B Appl Biomater.2008 Jan;84(1):64-9. 94- Geisler FH, Guyer RD, Blumenthal SL, McAfee PC, Cappuccino A, Bitan F, Regan JJ Patient selection for lumbar arthroplasty and arthrodesis: the effect of revision surgery in a controlled, multicenter, randomized study. J Neurosurg Spine. 2008 Jan;8(1):13-6. 95- Pil Sun Choy: Thesis . São Paulo Medicine College. 2000 96- Watts C, Hutchison G, Stern J, et al: Comparison of intervertebral disc disease treatment by chymopapain injection and open surgery. J Neurosurg 42:397–400, 1975 97- Smith L: Enzyme dissolution of the nucleus pulposus in humans. JAMA 187:137–140, 1964 98- Dabezies EJ, Langford K, Morris J, et al: Safety and efficacy of chymopapain (Discase) in the treatment of sciatica due to a herniated nucleus pulposus. Results of a randomized, double-blind study. Spine 13:561–565, 1988 99- Fraser RD: Chymopapain for the treatment of intervertebral disc herniation. A preliminary report of a double-blind study. Spine 7:608–612, 1982 100- Javid MJ, Nordby EJ, Ford LT, et al: Safety and efficacy of chymopapain (Chymodiactin) in herniated nucleus pulposus with sciatica. Results of a randomized, double-blind study. JAMA 249:2489–2494, 1983 101- Nordby EJ, Javid MJ: Continuing experience with chemonucleolysis. Mt Sinai J Med 67:311–313, 2000 102- Nordby EJ, Brown: Present status of chymopapain and chemonucleolysis. Clin Orthop 129:79–83, ‘77 103- Nordby EJ, Lucas GL: A comparative analysis of lumbar disk disease treated by laminectomy or chemonucleolysis. Clin Orthop 90:119–129, 1973 104- Gunzburg R, Fraser RD, Moore R, et al: An experimental study comparing percutaneous discectomy with chemonucleolysis. Spine 18:218–226, 1993 105- Mansfield F, Polivy K, Boyd R, et al: Long-term results of chymopapain injections. Clin Orthop 206:67–69, 1986 106- Maroon JC, Abla A: Microdiscectomy versus chemonucleolysis. Neurosurgery 16:644–649, 1985 107- Tregonning GD, Transfeldt EE, McCulloch JA, et al: Chymopapain versus conventional surgery for lumbar disc herniation. 10-year results of treatment. J Bone Joint Surg Br 73: 481–486, 1991 108- Weill A, Chiras J, Simon JM, et al: Spinal metastases: indications for and results of percutaneous injection of acrylic surgical cement. Radiology 199:241–247, 1996 109- Lorenz M, McCulloch J: Chemonucleolysis for herniated nucleus pulposus in adolescents. J Bone Joint Surg Am 67: 1402–1404, 1985 110- Hijikata S: Percutaneous nucleotomy. A new concept technique and 12 years’ experience. Clin Orthop 238:9–23, 1989 111- Kambin P, Gellman H: Percutaneous lateral discectomy of the lumbar spine: a preliminary report. Clin Orthop 174:127–132, 1983 112- Onik G, Helms CA, Ginsberg L, et al: Percutaneous lumbar diskectomy using a new aspiration probe: porcine and cadaver model. Radiology 155:251–252, 1985

936 Spine 113- Onik G, Helms CA, Ginsburg L, et al: Percutaneous lumbar diskectomy using a new aspiration probe. AJR 144: 1137–1140, 1985 114- Kambin P, Sampson S: Posterolateral percutaneous suctionexcision of herniated lumbar intervertebral discs. Report of interim results. Clin Orthop 207:37–43, 1986 115- Fries JW, Abodeely DA, Vijungco JG, et al: Computed tomography of herniated and extruded nucleus pulposus. J Comput Assist Tomogr 6:874–887, 1982 116- Davis GW, Onik G: Clinical experience with automated percutaneous lumbar discectomy. Clin Orthop 238:98–103, 1989 117- Davis GW, Onik G, Helms C: Automated percutaneous discectomy. Spine 16:359–363, 1991 118- Maroon JC, Onik G, Sternau L: Percutaneous automated discectomy. A new approach to lumbar surgery. Clin Orthop 238: 64–70, 1989 119- Onik G, Mooney V, Maroon JC, et al: Automated percutaneous discectomy: a prospective multi-institutional study. Neurosurgery 26:228–233, 1990 120- Savitz MH, Chiu JC, Yeung AT (eds): The Practice of Minimally Invasive Spinal Technique. Richmond, VA: AAMISMS Education Press, 2000 121- Ascher PW, Heppner F: CO2-laser in neurosurgery. Neurosurg Rev 7:123–133, 1984 122- Zucherman JF, Zdeblick TA, Bailey SA, et al: Instrumented laparoscopic spinal fusion. Preliminary results. Spine 20: 2029–2035, 1995 123- Liebler WA: Percutaneous laser disc decompression: clinical experience with the Nd: YAG and KTP lasers, in Sherk HH (ed): Spine: Laser Discectomy. Philadelphia: Hanley & Belfus, 1993, Vol 7, pp 55–65 124- Yeung AT, Tsou PM: Posterolateral endoscopic excision for lumbar disc herniation: surgical technique, outcome, and complications in 307 consecutive cases. Spine 27:722–731, 2002 125- Choy DS, Case RB, Fielding W, et al: Percutaneous laser nucleolysis of lumbar disks. N Engl J Med 317:771–772, 1987 (Letter) 126- Choy DS, Ascher PW, Saddekni S, et al: Percutaneous laser disc decompression. A new therapeutic modality. Spine 17: 949–956, 1992 127- Sherk HH, Black JD, Prodoehl JA, et al: Laser diskectomy. Orthopedics 16:573–576, 1993 128- Yonezawa T, Onomura T, Kosaka R, et al: The system and procedures of percutaneous intradiscal laser nucleotomy. Spine 15:1175–1185, 1990 129- Kambin P: Arthroscopic microdiscectomy of the lumbar spine. Clin Sports Med 12:143–150, 1993 130- Kambin P: Arthroscopic microdiskectomy. Mt Sinai J Med 58: 159–164, 1991 131- Kambin P, Cohen LF: Arthroscopic microdiscectomy versus nucleotomy techniques. Clin Sports Med 12:587–598, 1993 132- Hermantin FU, Peters T, Quartararo L, et al: A prospective, randomized study comparing the results of open discectomy with those of video-assisted arthroscopic microdiscectomy. J Bone Joint Surg Am 81:958–965, 1999 133- Mayer HM, Brock M: Percutaneous endoscopic discectomy: surgical technique and preliminary results compared to microsurgical discectomy. J Neurosurg 78:216–225, 1993 134- Saal JA, Saal JS: Intradiscal electrothermal treatment for chronic discogenic low back pain: a prospective outcome study with minimum 1-year follow-up. Spine 25:2622–2627, 2000 135- Nardi PV, Cabezaz D, Cesaroni A. Percutaneous cervical nucleoplasty using coblation technology: clinical results, in fifty consecutive cases. ActaNeurochir Suppl 2005;92:7378 136- Slipman C, Bhagia SM, Frey M, et al. Nucleoplasty procedure for cervical radiculopathy: initial case series. Paper presented at the 2nd World Congress of the International Society of Physical and Rehabilitation Medicine; May 18-22, 2003; Prague, Czech Republic

Minimally Invasive Treatments for Spinal Degenerative Pathologies.

937

137- Slipman C, Frey M, Bhargava A, et al. P86. Outcomes and side effects following percutaneous cervical disc decompression using coblation technology : a pilot study. Spine J 2004;4(suppl):71S-72S 138- Woloszko J, Stalder KR, Brown IG. Plasma characteristics of repetitively-pulsed electiocal dischanges in saline solutions used for surgical procedures. IEEE Trans 2002:30:1376-83 139- Stalder KR, Woloszko J, Brown IG, et al. Repetitive plasma dischanges in saline solutions. App Phys Lett 2001;79:4503-05 140- Stalder KR, McMillen DF, Woloszko J. Electrosurgical plasmas. J Phys D: Appl Phys 2005;38:1728-38 141- Chen YC, Lee SH, Saenz Y, et al. Histologic findings of disc, end plate and neural elements after coblation of nucleus pulposus: an experimental ncleoplasty study. Spine J 2003;3:466-70 142- Chen YC, Lee S, Chen D. Intradiscal pressure study of percutaneous disc decompression with the nucleoplasty in human cadavers. Spine 2003;28:661-65 143- Bonaldi G., Baruzzi F.,Facchinetti A.,Fachinetti P.,Lunghi S.: Plasma Radio-Frequencybased diskectomyfor treatment of cervical herniated nusleus pulposus: feasibility, safety, and preliminary clinical results. Am J Neuroradiol 27: 2104-11, 144- A. Alexandre, L. Corò, A. Azuelos, M.Pellone: Percutaneous Nucleoplasty for discoradicular conflict. 12TH European Congress of Neurosurgery - EANS , Lisbon, Monduzzi Ed. , 2003 . 145- Bocci V.: Biological and clinical effects of ozone. Has ozone therapy a future in medicine? Br J Biomed Sci 56: 270-2791, 1999 146- Jacobs M T: Untersuchung uber zwishenfalle und typische komplikationen in der ozon-sauerstoff-therapie. Ozonachrichten 1982: 1-5 147- Alexandre A.: Protocollo al Ministero per l’iniezione intradiscale di Ozono Medicale. Roma, Ottobre 1996: 1° Congresso Italiano sull’applicazione dell’Ozono nel trattamento delle ernie discali. 148- Alexandre A.,Paradiso R.,Salgado H.,Murga M.,Albarreal A., Buric J.,Corò L.,Scopetta S.,Giocoli H.,Marin F.: Intradiscal Ozone injection: a new treatment for lumbar disc herniations. Results at 5 years. 12th World Congress of Neurosurgery, Sidney, 16-20 Sept.2001. 149- Fabris G,Tommasini G, Lavaroni A et Al : Percutaneous treatment of lumbar herniated disk. Riv. Neuroradiol. 1997; 10:523-532 150- Andreula C.F., Simonetti L., de Santis F., Agati R., Ricci R., Leonardi M.: Minimally Invasive Oxygen-Ozone Therapy for Lumbar Disk Herniation . American Journal of Neuroradiology 24:996-1000, May 2003 151- Paradiso.R., Alexandre A.: The different outcomes of patients with disc herniation treated either by microdiscectomy, or intradiscal ozone injection. Acta Neurochir Suppl 92: 118-127, 2005 152- Alexandre A., Corò L. , Azuelos A., Buric J.: Endoscopic Lumbar Peridurolysis. Three years experience. 12TH European Congress of Neurosurgery - EANS, Lisbon, Monduzzi editore 825-825, 2003 . 153- Deramond H, Depriester C, Galibert P, et al: Percutaneous vertebroplasty with polymethylmethacrylate. Technique, indications, and results. Radiol Clin North Am 36:533–546, 1998 154- Barr JD, Barr MS, Lemley TJ, et al: Percutaneous vertebroplasty for pain relief and spinal stabilization. Spine 25:923-928, 2000 155- Cotten A, Dewatre F, Cortet B, et al: Percutaneous vertebroplasty for osteolytic metastases and myeloma: effects of the percentage of lesion filling and the leakage of methyl methacrylate at clinical follow-up. Radiology 200:525-530, 1996 156- Martin JB, Jean B, Sugiu K, et al: Vertebroplasty: clinical experience and follow-up results.

938 Spine Bone 25 (Suppl 2):11S–15S, 1999 157- Weinstein JN, Spratt KF, Spengler D, et al: Spinal pedicle fixation: Reliability and validity of roentgenogram-based assessment and surgical factors on successful screw placement. Spine 13:1012-1018, 1988 158- Yeung AT: Consideration for the use of the KTP laser for disc decompression and ablation, in Sherk HH (ed): Spine: Laser Discectomy. Philadelphia: Hanley & Belfus, 1993, Vol 7, pp 67-93 159- Glossop ND, Hu RW, Randle JA: Computer-aided pedicle screw placement using frameless stereotaxis. Spine 21: 2026–2034, 1996 160- Muramatsu K, Hachiya Y, Morita C: Postoperative magnetic resonance imaging of lumbar disc herniation: comparison of microendoscopic discectomy and Love’s method. Spine 26: 1599-1605, 2001 161- Foley KT, Gupta SK: Percutaneous pedicle screw fixation of the lumbar spine: preliminary clinical results. J Neurosurg (Spine 1) 97:7-12, 2002 162- Choi WW, Green BA, Levi AD: Computer-assisted fluoroscopic targeting system for pedicle screw insertion. Neurosurgery 47:872–878, 2000 163- Burns BH: An operation for spondylolisthesis. Lancet 1:1233, 1933 164- Mathews HH, Evans MT, Molligan HJ, et al: Laparoscopic discectomy with anterior lumbar interbody fusion: A preliminary review. Spine 20:1797-1802, 1995 165- Minimally Invasive Spinal Surgery: A Historical Perspective, Neurosurg Focus 16(1), 2004. 166- Regan JJ, Yuan H, McAfee PC: Laparoscopic fusion of the lumbar spine: minimally invasive spine surgery. A prospective multicenter study evaluating open and laparoscopic lumbar fusion. Spine 24:402-411, 1999 167- Escobar E, Transfeldt E, Garvey T, et al: Video-assisted versus open anterior lumbar spine fusion surgery: a comparison of four techniques and complications in 135 patients. Spine 28: 729–732, 2003 168- Foley KT, Holly LT, Schwender JD: Minimally invasive lumbar fusion. Spine 28:S26-S35, 2003 169- Rabischong personal communication,1996. 170- Scoville WB, Dohrmann GJ, Corkill G: Late results of cervical disc surgery. J Neurosurg 45:203-210, 1976 171- Roh SW, Kim DH, Cardoso AC, et al: Endoscopic foraminotomy using MED system in cadaveric specimens. Spine Spine 25: 260–264, 2000 172- Adamson TE: Microendoscopic posterior cervical laminoforaminotomy for unilateral radiculopathy: results of a new technique in 100 cases. J Neurosurg (Spine 1) 95:51-57, 2001 173- Wang MY, Green BA, Coscarella E, et al: Minimally invasive cervical expansile laminoplasty: an initial cadaveric study. Neurosurgery 52:370-373, 2003 174- Khalil J. Chedid; Mokbel K. Chedid, M.D.: The Tract of History in the Treatment of Lumbar Degenerative Disc Disease. Neurosurg Focus 16(1), 2004

939

Percutaneous Endoscopic Lumbar Discectomy (PELD) -Transforaminal and Interlaminar approachesFUJIO ITO President of Aichi Spine Institute Guest professor of Fujita Health University Key words: percutaneous endoscopic lumbar discectomy, transforaminal, interlaminar, thermal ablation

Introduction PELD requiring smaller dissections, an overnight stay, and little resection of lamina, yellow ligament, muscle, etc. was introduced several year ago. PELD is a new type of MISS that uses a local anaesthetic and was developed from percutaneous nucleotomy.

Subject The selected subjects are those cases with strong sciatica even under conservative treatment for 6 weeks or more and acute cases difficult to move the body due to severe pain, under the condition that MRI has identified moderate or huge herniation. However, those cases where either upward or downward migration in L4/5 or higher is more than about 10 mm, instability from functional X-ray photography, lateral recesses from CT scan are apparent or where osseous proliferation of spondylolysis is assumed to be responsible for pain have to be operated by microscopic discectomy or microendoscopic discectomy as a rule.

Operation Method Surgical equipment Carbon fiber transparent surgical table; C-arm image intensifier and monitor; light source and hi-vision camera and monitor; 20˚ endoscope; 7 mm working cannula; guide-pin, 1.9 - 6.8 mm serial dilator, and 6.5 mm blunt obturator; punch, forceps, and 3 and 5 mm trephines, bipolar radiofrequency electrode, irrigation system etc (Fig. 1). Anesthetic method Use a local anaesthetic and a sedative intravenous anesthetic. When a needle runs through pain-sensitive tissues, add 0.5 - 1% lidocaine solution by 2 - 3 cc. Maintain consciousness with anesthesia of patients during operation with propofol (1 - 4 mg/kg/h) and remifentanyl (0.02 - 0.06 µg/kg/min) or fentanyl (50 - 500 µg). Since perineural cicatrix can exist at unexpected locations and the courses of nerves may have been changed, patients are preferred to be conscious enough to respond easily.

940 Spine

Fig. 1 Percutaneous Endoscopic Lumbar Discectomy 1. Percutaneous endoscopy & serial dilator 2. Half and half position upper half : epidural tissue lower half : nucleus 3. High-vision camera 4. resect superior facet by drill if narrow foramen

Perfusion pressure Use a perfusion pump to wash down a small amount of bleeding with perfusion solution at a low pressure of 50 cc/min, which enables to secure a good field of view. Perfusion also plays a significant role in infection prevention because of its cleansing effect. Transforaminar approach This is a PELD’s standard approach to reach the safety triangle zone (1. caudal side of exiting root, 2. ventral side of dura mater, and 3. upper endplate of lower vertebra) via intervertebral foramina. This is used in from L1/2 to L5/S1 levels (cases of low iliac crest only). In a prone position, 10 - 14 cm from the midline is the needle’s entry point for L4/5. Place the needle once to the superior articular process at an angle of about 20 - 25 degrees to the horizontal surface, from the mid-isthmus of the foramen toward epidural space. When the needle has reached to the safety triangle zone, aim the needlepoint in the image at the medial pedicle line in the anteroposterior view and at the point of penetrating the posterior annulus in the side view. Perform discography using radiopaque dye containing indigo carmine. Insert a 0.8 mm guide wire into an 18 G needle, and after

Percutaneous Endoscopic Lumbar Discectomy (PELD) -Transforaminal and Interlaminar approaches-

941

removing the needle, insert a 6.5 mm dilator along the wire until its end comes immediately beneath the foramen and annulus. Overlap it with a 7 mm oblique cannula and connect to the perfusion system. If a 20˚ endoscope with a diameter of 6 mm is inserted, hi-vision images are displayed on the monitor. Secure the field of view by shrinking epidural fat, soft tissues likely to inflame, etc. with radiofrequency bipolar. The ideal field of view is epidural space in the upper part and intradiscal region in the lower, half-and-half (Fig. 2). The field of view is structured in layers, consisting of superior facet, epidural fat, inflammatory epidural scar, PLL (posterior longitudinal ligament), annulus, and disc mass in order. Denatured lumbar discs colored in blue are easy to identify. First, start cutting the deep layer of the annulus. Extract the herniated mass with forceps from beneath the windowed space of annulus fibrosus. Tilting the cannula horizontally makes it possible to extract even a large mass of hernia that protruded into epidural space. Since forceps can be used in a wide area from the near side to the opposite side for extended hernias, extracting them using space is possible without retracting nerves (Fig. 3).

Fig. 2 Transforaminal approach 1. Insertion of the dilator from safty triangle into the disc 2. fixed of oblique cannule in half and half position 3. Target fragmentectomy by forceps 4. Resection from tear of annulus

942 Spine

Fig. 3 Wide L4/5 central huge herniation – Transforaminal approach 1. pre-operative sagittal view. 2. pre-operative axial view. 3. Immediately 2 hours after operation. 4. Enlarged dura after operation.

End-point checks are required to verify the completion of decompression. 1.fatty tissue flows in as a result of water pressure change in epidural space is a proof of decompression (axillary clearance). 2. identifying respiratory pulsating of PLL and neural mobility is active (epidural clearance). 2. Interlaminar (IL) approach Interlaminar approach is performed when the interlaminar space is wide and the pelvic alata is higher than the transverse process of L5/S1. There are two methods. One is “split method” where you must dialate the yellow ligament by serial dilators from the shoulder of the S1 root. And the other is “resecting method” where you must resect the yellow ligament from the posterior by use of the punch into the axillar portion of the S1 root. The patient is lying in the decubitus position on the operation table with the affected side upward when applying the split method. First, using the A-P view, insert the needle through the center of the L5/S1 interlaminar space toward the lateral wall of the lamina at roughly 20°. Second, adjust the needle so that it is sliding along the medial wall of the

Percutaneous Endoscopic Lumbar Discectomy (PELD) -Transforaminal and Interlaminar approaches-

943

lamina while being inserted until it touches the surface of the yellow ligament. Next, you must recheck the correct needle position by epidurography to see if it is located in the portion of the shoulder of the S1 root after penetrating the yellow ligament. Then, insert the serial dilators which range from 1.9∼6.8 mm. The dilators will gradually separate the yellow ligament and gently retract the S1 root medially. Next, when the dilators reach the posterior of the disc, insert the 7mm “round end” cannula over the dilators. After that, insert the endoscope into the cannula so that you can remove the prolapsed nucleus. The split method will be used on 90% of the procedures (Fig. 4). Applying the split method you will be able to see the natural closing of the yellow ligament and you can therefore avoid cutting the yellow ligament which is needed to protect the adhesion of the nerve. The adhesion rate in applying the split method is lower than that in conventional open surgery (Fig. 5).

Fig. 4 Insertion technique of interlaminar approach 1. Insert needle along medial wall of lamina in interlaminar space 2. Recognize needle path-way on S1 root shoulder by epidurography 3. Put on disc posterior edge 4. Remove nucleus under S1 root

944 Spine

Fig. 5 Interlaminar approach 1. Insert 7mm cannule on S1 root shoulder from interlaminar space 2. Resect upward-migrated mass by forceps 3. Resected mass by target fragmentectomy 4. Splitted Ligamentum flava was closed after pull back of cannule

If the herniation has migrated upward you must shave or carve a partial portion of the inferior L5 lamina edge using a trephine, chisel or diamond burr in order to increase the range of motion of the endoscope. Then you can remove the migrated herniation which has moved upward by more than 1cm (Fig. 6). The resecting method will be used on 10% of the procedures when there is a large herniation at the axillar portion of the S1 root.

Percutaneous Endoscopic Lumbar Discectomy (PELD) -Transforaminal and Interlaminar approaches-

945

Fig. 6 Right L5/S upmigrated herniation – interlaminar approach 1. Upmigrated herniation in saggital View - pre-operative. 2. Right herniation in axial View - pre-operative. 3. Immediately 2 hours after operation. 4. Enlarged dura after operation.

REFERENCES 1. Kambin P, O’Brien E, Zhou L, et al. : Arthroscopic microdiscectomy and selective fragmentectomy. Clin Orthop.1998; 347: 150-167. 2. Hijikata S : Percutaneous nucleotomy . A new concept technique and 12 years’ experience. Clin Orthop. 1989; 238: 9-23. 3. John C. Chiu , Thomas JC, Martin HS, et al : Multicenter study of percutaneous endoscopic discectomy (lumbar, cervical, and thoracic). J Minim Invasive Spinal Tech. 2001; 1: 33-37. 4. John C. Chiu : Endoscopic lumbar foraminoplasty. In: Daniel HK. ed. Endoscopic spine surgery and instrumentation. New York: Thieme Medical Publisher, Inc . 2004; 212-229. 5. Kambin P, Zhou L : History and current status of percutaneous arthroscopic disc surgery. Spine. 1996; 21: 57-61. 6. Knight MT, Vajda A, Jakab GV, et al. : Endoscopic laser foraminoplasty on the lumbar spine – early experience. Minim Invasive Neurosurg. 1998; 41: 5-9.

946 Spine 7. Yeung AT, Tsou PM : Posterolateral selective endoscopic discectomy. Spine. 2002; 27(7): 722-731. 8. Yeung AT, Tsou PM : Posterolateral endoscopic excision for lumbar disc herniation. Surgical technique, outcome, and complications in 307 consecutive cases. Spine. 2002; 27(7): 722-731. 9. Mayer HM : Spine update. Percutaneous lumbar disc surgery. Spine. 1994 ; 19: 27192723. 10. Askar Z, Wardlaw D, Choudhary S, et al. : A ligamentum flavum-preserving approach to the lumbar spinal canal. Spine. 2003; 28: 385-390. 11. Zahiri H, Zahiri CA, Pourmand K, et al. : Percutaneous approach to the fifth lumbar and first sacral disc. Clin Orthop. 2002; 395: 148-153. 12. Onik G, Maroon J, Davis GW. : Automated percutaneous discectomy at the L5-S1 lever. Use of a curved cannula . Clin Orthop. 1989; 238: 71-76. 13. McCulloch, JA: Focus issue on lumbar disc herniation: Macro-and microdiscectomy. Spine 1996; 21: S45-556. 14. Lee SH, Uk Kang B, Ahn Y, Choi G,et al. : Operative failure of percutaneous endoscopic lumbar discectomy: a radiologic analysis of 55 cases. Spine 2006 May 1;31 (10): 285-290. 15. F Ito ,Y Miura, S Nakamura, M Taguchi : Percutaneous Endoscopic Lumbar Discectomy (PELD)—Transforaminal approach and indications— Asian Journal of NeurosurgeryAJNS

947

Persistent and recurrent lumbosciatica after lumbar discectomy. Surgical aspects of Failed Back Surgery Syndrome. SVETOSLAV K. KALEVSKI, MD, PhD, NIKOLAY A. PEEV, MD Department of Neurosurgery, Medical University – Varna, Bulgaria Clinic of Neurosurgery, “St. Anna” Regional Hospital - Bulgaria Key words: lumbar disc surgery, FBSS, reoperation, outcome, chronic pain, fibrosis

INTRODUCTION Dissatisfactory results after lumbar discectomy and the rate of re-interventions vary widely (5%-50%) in different studies. 39 The possibility of severe disability after reoperations justify detailed analysis of the reasons for failure of the primary discectomy, also the reasons for failure of the reoperations and other influencing factors. We will analyze and classify the commonest etiological factors that cause reinterventions (recurrent disc herniation, spinal stenosis, complications, etc.), as well as the early and long term results related to different structural reasons. We will elaborate on the diagnostic and treatment algorithms, also on the indications for reoperation.

Background When in 1934 J. Mixter WJ and Bar JS40 first announced that they operated a patient with lumbar disc herniation, they surely believed that a breakthrough has been achieved in the modern lumbar surgery. Several years later Mixter noted that not all operations performed for the treatment of lumbar disc herniation were after all so successful.1 Despite the rapid development of the diagnostic modalities and the operative techniques during the last decades, the lumbar discectomy (LD) and the postoperative results are a matter of high interest and discussions. Still this is a procedure that may result in a dissatisfactory results and disappointment for the patient and the surgeon. Dissatisfactory results after lumbar discectomy and the rate of reinterventions vary in a wide range (5%-50% dissatisfactory results and 5-19% reiterventions) in various studies.39 The possibility of severe disability after reoperations justifies detailed analysis of the reasons for failure of the initial discectomy, also the reasons for failure of the reoperations and other influencing factors.

Etiology The introduction of the term Failed Back Surgery Syndrome (FBSS) by Wilkinson40,41

948 Spine was meant to integrate heterogeneous group of factors that are at the origin of the persistence of pain symptoms among patients who undergo lumbar surgery. The surgical reasons that are commonly emphasized are inadequate neural decompression, recurrent disc herniation (RDH), underestimated associated lateral or central stenosis, operation at a wrong level, poor patient selection, epidural and epineural fibrosis, arachnoiditis, segmental instability, facet joint disease, nerve root injury, infectious complications, dural tear, etc. Some non-surgical reasons like physiological, occupational physical, also psychological factors, etc. are also emphasized. (Fig 1, 2, 3, 4). In 1981 Burton CV et al. published a series of a few hundred cases with FBSS, pointing the lateral stenosis as a one of the most significant factors causing FBSS, at a rate going as high as 58%.43 After this publication a lot of authors published series of

Fig. 1 T2/T1 MRI demonstrating big retained disc fragment at L4-L5 level.

Fig. 2 T2/T1 MRI demonstrating massive recurrent disc herniation at L5-S1 level

Persistent and recurrent lumbosciatica after lumbar discectomy. Surgical aspects of Failed Back Surgery Syndrome.

949

Fig. 3 Postoperative MRI of a 37 years old patient after LD at L4-L5 and L5-S1. The MRI demonstrates unattended L3-L4 disc herniation that caused postoperative complaints.

Fig. 4 MRI of a 42 years old patient after two surgical interventions at L4-L5 level. The MRI demonstrates marked postoperative fibrosis at the operated level.

reoperated patients with emphasis on recurrent disc herniation and lumbar instability as a reason for FBSS.1,2,3,4,5,6 Based on the series of reoperated patients presented by the authors listed above, also in accordance with our own experience, we could identify the following groups of factors that could be expected to result in dissatisfactory postoperative results and leading to repetitive surgery. 1. In general the wrong initial selection of patients is the first most major reason that predicts unsatisfactory postoperative results. This first stage that include the whole

950 Spine diagnostic process and the evaluation of the indications for operative management is the main determinant for the treatment outcome. It is at this stage in particular that the associated central or foraminal stenosis that could significantly contribute to the compression of the neural structures is being underestimated or missed.11,12,13 2. The unnecessary surgery could also be a reason for a poor outcome. Having unnecessary surgery performed, the problem of the patient is not only addressed in an inappropriate manner, but also this could contribute for a further deterioration. According to Wilkinson41, the unnecessary excision of normal disc increases the risk of a chronic lumbar pain as a result of lumbar segmental instability. Furthermore the patient is unnecessarily put under a risk of nerve root injury, incidental durotomy, arachnoiditis, hemorrhage, infection, etc. The risk of recurring disc herniation due to retained disc fragments is also increased. It is also believed that for the patients who have had a primary lumbar discectomy for lumbar disc protrusion, the chance for a repetitive surgery due to retained disc fragments is three fold as high as for the patients that have had disc extrusion or sequestration by the time of the initial surgery.14 3. The third most common reason for a poor outcome is a bad surgery that include discectomy on a wrong level due to a mistake or due to anatomical variations, retained disc fragment, unattended adjacent level disc herniation, unattended spinal stenosis or spinal tumor.15,16 Disc fragments that are not completely removed during the initial discectomy could cause direct nerve root compression in the immediate postoperative period thus causing continuation of the preoperative complaints. After a period of time the residual disc fragments could contribute to extensive proliferation of fibrous tissue which will naturally result in recurrence of pain syndrome, also neurological and functional deterioration. The anatomical variations could also complicate the localization of the proper level where the LD should be performed. This is valid especially in cases where there is no intraoperative X-ray localization and when the sacrum is not properly identified due to lumbalisation of the sacrum or sacralisation of the lumbar vertebra.17 Underestimation of the lateral stenosis is a considerable reason for the unsatisfactory postoperative results, especially when combined with disc protrusion. The stenosis should be diagnosed before the initial surgery and this should be expected from every surgeon. Removal of a protruded disc without attacking foraminal stenosis, especially in middle-aged and elderly patients most probably will result in poor outcome. The clinical investigation of patients with FBSS, after one or more surgical reinterventions is a matter of paramount importance for the establishment of an appropriate diagnostic and therapeutic algorithm. According to most of the authors13,18,19,20 the diagnostic process is generally directed towards not only the identification of anatomical structure at the origin of the pain and the neurological deterioration, but also towards determining the future development of signs and symptoms with time. Gil and Frymoyer19, in their work propose a system for the classification of the

Persistent and recurrent lumbosciatica after lumbar discectomy. Surgical aspects of Failed Back Surgery Syndrome.

951

complaints of patients with FBSS based on the time elapsed since the initial surgery. Thus they suggested four groups of patients: 1. Complaints in the immediate postoperative period that have the same intensity and characteristic pattern as those prior to the surgery. In that case wrong diagnosis or technical mistake should be considered and actively sought (ex. operated wrong level, unattended adjacent level disc herniation, spinal tumor).21 Bad patient’s selection and psychological factors could also be a reason. 2. Early complaints that emerge within a few days, up to weeks after the discectomy usually relates to infection or incidental unattended durotomy.12,18,22,23,24,25 3. Pain syndrome and neurological deterioration that emerge after several months, up to 1-2 years are usually attributed to recurrent disc herniation, epidural fibrosis, arachnoiditis or psychological factors. According to several authors the above mentioned causes constitute the most common factors for bad outcome after LD.11,13,14,26,27 4. The late postoperative complaints that emerge after more than 1-2 years are usually due to newly-developed spinal stenosis on the same or adjacent level or to segmental instability. Of note is that from all of the published LD series 4 to 15 % of patients will eventually be reoperated.28,29,30,31,32 Even with the best patient selection and appropriate surgical technique the rate of patients with good outcome could never be 100%. There is always a subgroup with postoperative results that are unsatisfactory, thus the patient that is admitted to hospital for elective LD should be informed for this possible outcome.

Treatment There is still no unified approach to the patients with FBSS.15 The majority of authors agree that the treatment should be tailored according to the time elapsed between surgery and the appearance of the first complaints, duration and intensity of the symptoms. It is also particularly important to identify the presumed anatomical reason that is believed to cause the complaints. In general the treatment procedures are classified as follow: A. Anatomical procedures – intended to address the structural cause of pain and are exemplified by spine surgery namely repetitive surgical interventions B. Augmentative procedures – spinal cord stimulation, known also as dorsal column stimulation is a procedure that requires implantable medical device to treat chronic neurological pain in accordance with the Melzack and Wall’s gate control theory of pain. Indeed stimulation causes "closing of the gate" by the antidromic activation of large-diameter afferent fibers. An electric impulse generated by the device produces a tingling sensation that alters the perception of pain. The device is implanted into the epidural space either by percutaneous approach or by surgical laminectomy or laminotomy. The analgesic effect of spinal epidural stimulation in man was first reported in 1971.44 Studies since then have demonstrated efficacy of SCS in relieving selected chronic pain disorders, including failed back surgery syndrome.45,46 C. Ablative procedures – The aim of spinal cord ablative procedures is to interrupt

952 Spine the nociceptive pathways running through specific sectors of the spinal cord itself (ex. dorsal root entry zone lesioning, radiofrequency neurotomy) D. Conservative treatment procedures: – epidural steroid applications, intrathecal medication delivery, rehabilitation, physiotherapy, etc.33 In general all the patients with postoperative complaints after LD are initially put under aggressive medical treatment (pharmacotherapy) and rehabilitation. If the conservative treatment fails, a repetitive surgery may be contemplated. Several authors15, 34,35 usually consider the same indications for the repetitive surgery as for the initial LD: 1. Well defined anatomical structure that cause compression over the neural elements and that could be surgically removed. 2. Progressing neurological deterioration. 3. Prolonged and intractable pain syndrome by conservative management. 4. Cauda equina syndrome. 5. Pain syndrome that significantly interferes with the person's ability to perform the every day activities.

Surgical strategy The chosen surgical techniques vary according to the pathology that need to be addressed. The decision to perform another operation should be based on well established preoperative diagnosis and the intraoperative findings of the previous intervention. In general the repetitive surgical procedure is characterized by further decompression of the inadequately decompressed neural structures by the previous operation. Usually the decompression is achieved by removing retained disc fragment, recurrent disc herniation, epidural fibrosis and by addressing the underestimated and unattended spinal stenosis during the prior surgical intervention. If incidental and unattended durotomy is diagnosed, the integrity of the dural sac should be restored. In general the extent of the repetitive surgery is bigger if compared to the primary LD intervention. This is in general attributed to the fibrous tissue proliferation that is usually encountered over the dural sac and corresponding nerve root at the site where primary LD had been performed. For the patients that are diagnosed with recurrent disc herniation on the same or adjacent level, another microdiscectomy is performed. The intervertebral disc space should be thoroughly revised and the disc fragments should be completely removed. The fibrous tissue that is normally found at the site of the reintervention should be also removed with microdisection of the dura mater and the corresponding nerve root. The ultimate goal should be a root free of fibrous adhesions and easy to mobilize. (Fig 5). If the dural fibrous adhesions are the anatomical factor that is believed to be the generator of the pain syndrome and neurological deterioration (fibrous adhesions may stretch or compress nerve roots), microdisection of the dura mater and the corresponding nerve root is performed. The surgical procedure is carried out respecting the rules of the lumbar repetitive surgery – the upper and lower level laminas should be very well exposed (the muscle tissue should be thoroughly dissected). If necessary the bony decompression could be extended to unilateral hemilaminectomy or bilateral

Persistent and recurrent lumbosciatica after lumbar discectomy. Surgical aspects of Failed Back Surgery Syndrome.

953

Fig. 5 In situ postoperative fibrosis A; dissection and decompression of the nerve root – B; dissection and decompression of dura and the adjacent nerve root - C.

laminectomy. After identification of ligamentum flavum or dura mater a careful microdissection should be performed. The fibrous adhesions should be stripped off from the dura and the adjacent nerve root as much as possible. In order to facilitate the nerve root decompression and mobilization, medial facetectomy and foraminotomy should be performed. Before the closure of the operative wound, the dura and the nerve root could be covered with a free fat graft that could be harvested from the subcutaneous fat tissue. Some of the authors believe that this procedure will reduce the fibrous tissue formation, but there are no strong evidences reported in the literature that this procedure is efficient enough to reduce the postoperative fibrosis. In order to prevent dislocation of the fat graft, it should be fixed with one or two sutures to the adjacent paraspinal muscle tissue. (Fig.6).

954 Spine

Fig. 6 Disected dura and nerve root covered with a Free Fat Graft

In the case when underestimated and unattended spinal stenosis need to be addressed, medial facetectomy and foraminotomy should be performed. If necessary the bony decompression could be extended to unilateral hemilaminectomy or bilateral laminectomy, with the usual caution to prevent segmental instability. In the majority of the cases, the above described decompressive procedures are performed, to remove a combination of different anatomical structures causing compression of the neural elements.

Prognosis In general, the best outcome in terms of reducing the pain syndrome and improving the functional status should be expected among the patients that had had repetitive surgery due to recurrent disc herniation and unattended spinal stenosis during the initial LD. Patients that have extensive epidural fibrous tissue proliferation are anticipated to have limited and short lasting period of improvement of the pain syndrome and functional status after the reoperation. Usually these patients will have recurring pain syndrome and decreased functional status after a period of 1, up to 2 years. This could be considered as an indication for another reoperation. It is noteworthy that with the number of the reinterventions, the pain free interval and the duration of the functional improvement decrease. Thus it is believed that there is no point and it is even dangerous for the patient to be operated again when the number of reoperations go beyond three or in particular four. These patients should be referred for augmentative or ablative procedures.28,36,37,38,45,46

Conclusion (take home) 1. Even with the best patient selection and appropriate surgical technique the rate of the patients with good outcome could never be 100% 2. The wrong primary selection of the patients is the first most important reason that lead to unsatisfactory postoperative results.

Persistent and recurrent lumbosciatica after lumbar discectomy. Surgical aspects of Failed Back Surgery Syndrome.

955

3. The most common reason for prolonged and recurrent complaints after LD are the recurrent disc herniation and underestimated and unattended spinal stenosis. 4. The best outcome in terms of reducing the pain syndrome and improving the functional status should be expected among the patients that had had repetitive surgery due to recurrent disc herniation and unattended spinal stenosis during the initial LD. 5. Patients that have extensive epidural fibrous tissue proliferation are anticipated to have limited and short lasting period of improvement of the pain syndrome and functional status after the reoperation. 6. The rate of complications (incidental durotomies, infections, nerve root injury, etc.) is higher among the patients that had had repetitive surgery by comparison with those have had only one LD. 7. For the patients who have had a primary lumbar discectomy for lumbar disc protrusion, the chance for following repetitive surgery due to retained disc fragments is three fold as higher as for the patients that have had disc extrusion or sequestration by the time of the initial surgery 8. With the number of the reinterventions, the pain free interval and the duration of the functional improvement decrease. 9. The multiple repetitive surgical interventions decrease the functional status of the patient.

REFERENCES 1. Slipman CW, Shin CH, Patel RK, Isaac Z, Huston CW, Lipetz JS, Lenrow DA, Braverman DL, Vresilovic EJ Jr. Etiologies of failed back surgery syndrome.Pain Med. 2002 Sep;3(3):200-14; discussion 214-7. 2. Frymoyer JW, Donaghy RM. The ruptured intervertebral disc. Follow-up report on the first case fifty years after recognition of the syndrome and its surgical significance. J Bone Joint Surg Am. 1985 Sep;67(7):1113-6. 3. Frymoyer JW, Hanley E, Howe J, Kuhlmann D, Matteri R. Disc excision and spine fusion in the management of lumbar disc disease. A minimum ten-year followup. Spine. 1978 Mar;3(1):1-6. 4. Frymoyer JW, Matteri RE, Hanley EN, Kuhlmann D, Howe J. Failed lumbar disc surgery requiring second operation. A long-term follow-up study.Spine. 1978 Mar;3(1):711. 5. Striffeler H, Groger U, Reulen HJ."Standard" microsurgical lumbar discectomy vs. "conservative" microsurgical discectomy. A preliminary study. Acta Neurochir (Wien). 1991;112(1-2):62-4. 6. Waguespack A, Schofferman J, Slosar P, Reynolds J.Etiology of long-term failures of lumbar spine surgery. Pain Med. 2002 Mar;3(1):18-22. 7. Slipman Curtis W, Shin CH. Etiologies of failed back surgery syndrome. Pain Medicine 2002;3:200-214. 8. Burton CV, Kirkaldy-Willis WH, Yong-Hing K, Heithoff KB. Causes of failure of surgery on the lumbar spine. Clin Orthop Relat Res 1981;157:191-9. 9. Herno A, Airaksinen O, Saari T, et al. Surgical results of lumbar spinal stenosis: A comparison of patients with or without previous back surgery. Spine 1995;20:964-9. 10. Morgan-Hough CV, Jones PW, Eisenstein SM. Primary and revision lumbar discectomy. A 16-year review from one centre. J Bone Joint Surg Br 2003 Aug;85(6):871-4.

956 Spine 11. Braverman DL, Slipman CW, Lenrow DA. Using Gabapentin to treat failed back surgery syndrome caused by epidural fibrosis: a report of 2 cases. Arch Phys Med Rehabil 2001;82:691-693. 12. Cammisa FP, Girardi FP, Sangani, PK, Parvataneni HK, Cadag SB, Sandhu, HS. Incidental durotomy in spine surgery. Spine 2000;25 (20):2663-2667. 13. Cinotti G. Failures of surgery in lumbar spinal stenosis. Causes and management. J Bone Joint Surg 1999;81 B (Suppl II): 142. 14. Coskun E, Suzer T, Topuz O, Zencir M, Pakdemirli E, Tahta K. Relationships between epidural fibrosis, pain, disability, and psychological factors after lumbar disc surgery. Eur Spine J 2000;9(3):218-23. 15. Phillips FM, Cunningham B. Managing chronic pain of spinal origin after lumbar surgery: the role of decompressive surgery. Spine 2002; 27 (22): 2547-54. 16. Suk KS, Lee HM, Moon SH, Kim NH. Recurrent lumbar disc herniation: results of operative management. Spine 2001;26:672-6. 17. Miller B, Gatchel RJ, Leland L, Stowell A, Robinson R, Polatin PB. Interdisciplinary Treatment of Failed Back Surgery Syndrome (FBSS): A Comparison of FBSS and NonFBSS Patients. Pain Practice 2005;5(3):190-202 18. Fritsch EW, Heisel J, Rupp S. The failed back surgery syndrome: reasons, intraoperative findings, and long-term results: a report of 182 operative treatments. Spine 1996;21(5):626-33. 19. Gill K, Frymoyer J. Management of treatment failures after docompressive surgery; Surgical alternatives and results. In: Frymoyer J. ed.The adult spine: Principles and Practice. 2nd edition ed. Philadelphia: Lippincott-Raven 1997;2111-2133. 20. Raffo C, Wiesel S, Lauerman W. Determining reasons for Failed Lumbar Spine Surgery. In; Frymoyer. Ed. The Adult spine. Philadelphia: Lippincott – Raven 2003;945-954. 21. Hazard RG. Failed back surgery syndrome. Clin Orth and related research 2006;443:228232 22. Fu Tsai-Sheng, Lai Po-Liang, Tsai Tsung-Ting, Niu Chi-Chieh, Chen Li-Huei, Wen-Jer Chen. Long-term results of disc excision for recurrent lumbar disc herniation with or without posterolateral fusion. Spine 2005;30(24):2830-2834. 23. McCutchen,Thomas M., Cuddy Brian G. Intervertebral disk space infection. Neurosurgery Quarterly 2001;11(3):209-219. 24. McCormack BM, Zide BM, Kalfas IH. Cerebrospinal fluid fistula and pseudomeningocele after spine surgery.In: Benzel E.C., ed. Spine Surgery, Techniques, Complication Avoidance and Management. Philadelphia: Churchill Livingstone, 1999;1465-74. 25. Wang JC, Bohlman HH, Riew KD. Dural tears secondary to operations on the lumbar spine. Management and results after a two-year-minimum follow-up of eighty-eight patients. J Bone Joint Surg Am 1996;78:706-711. 26. Abla A, Kadi M. Recurrent lumbar disc herniation: microsurgical approach Contemporary Spine Surgery 2005;6(10):1-6. 27. Li-Yang Dai, Qing Zhou, Wei-Fang Yao, Lei Shen. Recurrent lumbar disc herniation after discectomy: outcome of repeat discectomy. Surgical Neurology 2005;64:226-231. 28. Fiume D, Sherkat S, Callovini GM, et al. Treatment of the failed back surgery syndrome due to lumbo-sacral epidural fibrosis. Acta Neurochir.Suppl (Wien) 1995;64:116-8. 29. Hirabayashi S, Kumano K, Ogawa Y, Aota Y, Maehiro S. Microdiscectomy and second operation for lumbar disc herniation. Spine 1993;18:2206 -11. 30. Hu RW, Jaglal S, Axcell T, et al. A population-based study of reoperations after back surgery. Spine 1997;22:2265-71. 31. Keskimaki I, Seitsalo S, Osterman H, Rissanen P. Reoperations after lumbar disc surgery: a population-based study of regional and interspecialty variations. Spine 2000;25:1500-8.

Persistent and recurrent lumbosciatica after lumbar discectomy. Surgical aspects of Failed Back Surgery Syndrome.

957

32. Silvers HR, Lewis PJ, Asch HL, Clabeaux DE. Lumbar Discectomy for Recurrent Disc Herniation. J of Spinal Disorders 1994;7:408-419 33. Skaf G, Bouclaous C, Alaraj A, Chamoun R. Clinical outcome of surgical treatment of failed back surgery syndrome. Surgical Neurology 2005;64(6): 483 – 488. 34. Jonsson B, Stromqvist B. Repeat decompression of lumbar nerve roots: a prospective twoyear evaluation. J Bone Joint Surg Br 1993;75:894-7. 35. Hu RW, Jaglal S, Axcell T, et al. A population-based study of reoperations after back surgery. Spine 1997;22:2265-71. 36. Heger S. Psychosomatic aspects of failed surgery syndrome: why low back pain becomes a chronic disorder. Nervenarzt 1999;70:225-32. 37. Pearse JMS. Aspects of the failed back surgery syndrome: role of litignation. Spinal Cord 2000;38:63-70. 38. Schoeggl A, Maier H, Saringer W, Reddy M, Matula C. Outcome after chronic sciatica as the only reason for lumbar microdiscectomy. J Spinal Disord Tech 2002;15(5):4159. 39. Follett KA, Dirks BA. Etiology and evaluation of the failed back surgery syndrome. Neurosurg Q 1993;3:40-59. 40. Mixter WJ, Barr JS. Rupture of the intervertebral disc with involvement of the spinal canal. New Engl J Med 1934;211:210-5. 41. Wilkinson HA. The failed back syndrome. Etiology and therapy. New York: Raven Press, 1991. 42. Wilkinson HA. The failed back syndrome. 2nd edition. New York, NY: SpringerVerlag, 1992. 43. Burton CV, Kirkaldy-Willis WH, Yong-Hing K, Heithoff KB. Causes of failure of surgery on the lumbar spine. Clin Orthop Relat Res 1981;157:191-9. 44. Shimoji K, Higashi H, Kano T, Asai S, Morioka T:Electrical management of intractable pain. Masui 1971;20:444-447. 45. North RD,Kidd DH,Kaburak M,James C,Long DM : Spinal cord stimulation for chronic intractable pain : experiece over two decades Neurosurgery 1993 ; 32: 384-395 46. Law JD : Spinal cord stimilation in « the failed back surgery syndrome » : comparison of technical criteria for palliating pain in the leg vs in the low back. Acta Neurochir (Wien) 1992 ;117:95

958

Spinal tumors SURESH NAIR; GIRISH MENON; RAVI MOHAN RAO; MATHEW ABRAHAM; HARIHAR EASWER; KRISHNAKUMAR Department of Neurosurgery, Sree Chitra Tirunal Institute for Medical Sciences & Technology, Trivandrum, 695011, India Key words: spinal tumor, benign spinal tumors, extramedullary, intramedullary, metastases

Introduction Spinal tumors are a common cause of back pain and sensorimotor deficits in both adult and pediatric patients. The wide range of lesions and the varied clinical profile, make management of spinal tumors a challenging ordeal for any neurosurgeon.

Surgical anatomy The vertebral column is a column of 33 vertebrae which houses the spinal cord in its spinal canal. A typical vertebra consists of two essential parts: an anterior (front) segment, which is the vertebral body; and a posterior part – the vertebral (neural) arch which encloses the vertebral foramen. The vertebral arch is formed by a pair of pedicles and a pair of laminae, and supports seven processes, four articular, two transverse, and one spinous process. Superior and inferior articular facets on each vertebra act to restrict the range of movement possible. These facets are joined by a thin portion of the neural arch called the pars interarticularis. The vertebral canal houses the spinal cord and its meningeal coverings. The spinal cord averages 47 cm in length and 32 gm in weight accounting for about 3% of central nervous system. The spinal cord extends from the foramen magnum where it is continues with the medulla oblongata to the level of the first or second lumbar vertebrae. Below that level, the vertebral canal is occupied by spinal nerve roots and meninges. A fibrous strand, the filum terminale, continues from the spinal cord down to the coccyx . The spinal cord presents a cervical and a lumbar enlargement at the levels of attachment of the nerves to the limbs. The inferior most end of the cord is conical and is termed the conus medullaris. The coccygeal nerves are attached to it. Spinal cord generally occupies less than one-half of the cross sectional area of the spinal canal. It is divided almost into two halves by the anterior median fissure and the posterior median septum. This fissure contains the anterior spinal artery and vein and their penetrating branches and is rarely encountered during surgery. The posterior median septum is composed of fused pia matter from the medial surface of each posterior column. It is the route of entry for removal of most intramedullary pathology and can be identified by a longitudinal array of penetrating vessels. In cross section, the spinal cord is seen to consist of gray matter, which is shaped like the letter “H” surrounded by white matter. The spinal cord contains the descending motor tracts

Spinal tumors

959

and the ascending sensory tracts. The cervical and lumbar enlargements contain the neurons that supply the limbs. The cervical part of the cord conteins motor neurons giving rise to the spinal part of the accessory nerve and contains the neurons that supply the diaphragm. The thoracic and upper lumbar parts of the cord contain preganglionic sympathetic neurons, and the sacral cord contains parasympathetic preganglionic neurons giving rise to pelvic splanchnic nerves. There is a central canal running the length of the spinal cord, which extends from the fourth ventricle of the brain to the upper part of the filum terminale. The segment of the spinal cord to which a given pair of dorsal and ventral roots is attached is called a myelomere. Each dorsal root presents a swelling, the spinal (dorsal root) ganglion, which lies near or within the intervertebral foramen. Distal to the ganglion, each dorsal root combines with the corresponding ventral root to form a spinal nerve . There are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. The first pair of spinal nerves emerges between the atlas and the skull; hence C1 to 7 nerve roots leave the vertebral canal above the correspondingly numbered vertebrae. C8 emerges below the C7 vertebra, and all the remaining spinal nerves leave inferior to the corresponding vertebrae. The nerve roots below L1, and those which occupy the vertebral canal inferior to the cord, resemble a horse’s tail and hence are collectively called the “cauda equina” .Because the adult spinal cord does not extend down as far as the vertebral column does, the lower myelomeres are not opposite their correspondingly numbered vertebrae .and the lower spinal roots become increasingly oblique. The lumbosacral roots are the longest and the thickest. The lumbar nerves increase in size from above downward, whereas the lumbar intervertebral foramina decrease in diameter. Thus the L5 nerve root, the thickest, traverses the narrowest foramen. Therfore, it has an increased chance of compression by pathology compromising the foramen. The spinal cord, like the brain, is surrounded by the three meninges. The dura mater extends from the foramen magnum to the sacrum and coccyx. The dura is attached to the foramen magnum and the periosteium covering the uppemost cervical vertebrae and their ligaments. Through the remainder of the vertebral canal, the dura is not attached to the vertebrae, being separated by the epidural ( peridural or extradural) space, which contains fat and the internal vertebral venous plexus. The spinal dura extends as an oval tube from the foramen magnum to the S2 level. It is a tough fibrous membrane composed of longitudinal bundles of collagen and lined one either side by a single layer of flattened fibroblasts. It demonstrates negligible resistance to compression, but has considerable tensile strength. It is under resting tension and possesses elastic properties that allow for folding and unfolding in response to changes in canal length. Spinal dura is an effective barrier and is rarely transgressed by inflammatory or neoplastic pathology. The pia and arachnoid (leptomeninges) are probably neural crest and mesodermal in origin. Arachnoid is a thin transparent membrane which is closely applied to the dura allowing only a potential subdural space. Fenestrated reflections of arachnoid occur through out the subarachnoid space to become continuous with the outer pia. The spinal vasculature is loosely held to the surface of the spinal cord within this layer. The arachnoid reflections also sheath the individual nerve roots. Spinal pia is a well defined collagenous membrane and is thicker than the intracranial pia and it

960 Spine accounts for the white colour and firm consistency of the spinal cord. Lateral reflections of the pia form the dentate ligaments. The pia matter is tightly applied to the outer glial limiting membrane of the spinal cord and completely encircles the cord except at the root entry zones where it is briefly reflected over the exiting nerve roots. It is here that the pia may be transgressed by benign pathology. Laterally, the pia forms a discontinuous longitudinal septum, the denticulate ligament, which sends about 21 tooth-like processes laterally to fuse with the arachnoid and dura on each side. The ligament is a surgical landmark in that it is attached to the spinal cord about midway between the attachments of dorsal and ventral roots. The spinal cord is supplied by three longitudinal arterial channels, which are reinforced by segmental (e.g. branches from intercostal and lumbar) arteries. The anterior spinal artery (from the vertebral artery) lies in the anterior median fissure. Two posterior spinal arteries (also from the vertebral artery, directly or indirectly) descend lateral to the posterior median sulcus. They are reinforced at intervals by segmental arteries arising from intercostal or lumbar arteries that follow the nerve roots (radicular arteries) to the spinal cord. The segmental reinforcements are very important in reinforcing the longitudinal channels. There is usually at least one large contribution every 4-6 segments and there is often a large vessel in the lower thoracic region that is critical to the supply of the lumbar enlargement (arteria magna of Adamkiewicz). The blood supply to the spinal cord is by way of a single anterior and paired posterior spinal arteries. These vessels are supplemented throughout their course by a variable number of medullary vessels which are well protected on the ventral surface of their respective nerve roots. The intra dural spinal vascular system is well protected and not threatened during intradural surgery.

Classification Spinal tumours can be broadly divided into extradural and intradural tumours on the basis of their relation to the thecal sac. Within the intradural compartment, tumours can be either extramedullary (outside the spinal-cord parenchyma) or intramedullary (within the spinal-cord parenchyma. Extradural tumours, account for almost 60% of spinal tumors, intradural for 30% of tumors and concomitant intradural and extradural components account for 10% of spinal cord tumors. In view of the heterogeneous cell composition within the intradural compartment, the histogenesis of neoplasms located at this site is varied and the various spinal tumours can be grouped as given below.

Extradural tumours Benign tumours ¡ Osteoid osteoma ¡ Osteoblastoma ¡ Osteochondroma ¡ Chondroblastoma ¡ Giant-cell tumour ¡ Vertebral hemangioma

Spinal tumors ¡ Aneurysmal bone cysts Malignant tumours ¡ Osteosarcoma ¡ Ewing’s sarcoma ¡ Soft-tissue sarcoma ¡ Chordoma ¡ Chondrosarcoma ¡ Solitary plasmacytoma ¡ Multiple myeloma

Intradural Extramedullary tumours Tumours of spinal nerves ¡ Nerve sheath schwannomas/neurofibromas Neuroepithelial tumours ¡ Conus myxopapillary ependymomas Other CNS tumours ¡ Meningiomomas ¡ Lipomas ¡ Malignant mesenchymal hemangiopericytomas Local extension of regional tumours ¡ Paragangliomas Tumour-like cysts ¡ Dermoid ¡ Epidermoid Extramedullary metastases ¡ Mass lesions from neoplastic meningitis

Intradural Intramedullary tumours Neuroepithelial tumours ¡ Astrocytomas ¡ Ependymomas ¡ Oligodendrogliomas ¡ Mixed neuronal–glial gangliogliomas ¡ Embryonal neuroblastomas Other CNS tumours ¡ Hemangioblastomas ¡ Lipomas ¡ Germ cell tumours Vascular malformations ¡ Capillary hemangiomas ¡ Cavernous hemangiomas Metastases ¡ Small-cell lung cancer

961

962 Spine ¡ ¡ ¡ ¡

Non-small-cell lung cancer Lymphoma Renal-cell carcinoma Others

Spinal extradural tumours More than 90% of extradural spinal tumours are metastatic. The most common presenting complaint of patients with primary spinal tumours is pain. Although spinal deformity is a striking finding when present, fewer than 10% of patients with spinal tumours present with spinal instability needing surgical treatment. Weinstein, Boriani, and Biagini have developed one of several staging systems for spinal tumours on the basis of the Enneking staging system for primary bone tumours of the extremities 1,2. The Weinstein, Boriani, and Biagini surgical staging system classifies tumours in three ways: by their position in 12 radiating zones in the transverse plane across the vertebral body (like a clock face); by their position in five concentric layers (A–E) extending from the paraspinous soft issues to the dura; and by the longitudinal extent of the tumour based on the vertebral levels involved 1,2. When this staging system is combined with knowledge of the biological behaviour of the tumour, it can aid in the planning of surgical treatment to provide the best chance of complete tumour resection. Patients should have individualised approaches and treatment plans because there are many variations in aggressiveness of the tumour, spinal level, location within the vertebra, involvement of soft tissues and surrounding structures, neurological deficits, and spinal instability 3.

I. Benign tumours A. Osteoid osteoma Osteoid osteomas are benign bone lesions that are less than 2 cm in diameter and arise from spongy bone. They are most commonly located in long bones but occur in the spine in roughly 10% of cases 3. Most affect the posterior elements of the vertebrae. There is a slight male predominance and patient age is usually between 10 years and 20 years. Patients with osteoid osteomas typically present with pain. The pain associated with an osteoid osteoma is usually worse at night and is suppressed by salicylates or nonsteroidal anti-inflammatory medication. The lumbar spine is the most commonly affected portion of the spine, followed by cervical, thoracic, and sacral elements in descending order. Radiographically, osteoid osteomas have osseous sclerosis at the periphery of the lesion with a radiolucent centre. There are occasional matrix calcifications. These lesions tend to be round to oval in shape. CT is the imaging of choice and helps establish the extent of bony involvement. Histopathologically, the nidus of an osteoid osteoma has organised bony trabeculae, with vascular fibrous connective tissue. The treatment of osteoid osteomas include the use of salicylates, surgical resection, ablation with radiofrequency electrodes, laser, or alcohol injections, the gold standard being surgical resection

Spinal tumors

963

B. Osteoblastoma Osteoblastomas present with dull localised pain not relieved with salisylates. There is a male predominance and they generally occur in the younger population (60 years) and have a poorer prognosis than appendicular involvement. Osteosarcoma is a potentially curable disease with surgery and chemotherapy if patients are treated before the development of metastases. Osteosarcoma of the spine accounts for roughly 1–2% of osteosarcomas and for 4–14% of primary malignant tumours affecting the spine. These tumours affect the vertebral body in 90% of patients. Osteosarcoma of the spine has an especially poor prognosis. B. Ewing’s sarcoma Ewing’s sarcoma is a small, round, blue-cell tumour of unknown origin. Ewing’s sarcoma has been suggested to share substantial similarities with primitive neuroectodermal tumours. Patients aged 10–30 years are most commonly affected. Ewing’s sarcoma makes up about 10% of malignant musculoskeletal tumours and frequently affects the spine. The most common site of occurrence is the sacrococcygeal spine followed by the lumbar and thoracic regions. The main clinical presentation is pain, but up to 60% of patients will have neurological symptoms. Lesions can be centred in the vertebral bodies, the posterior elements, or both. MRI is the diagnostic imaging study of choice and is necessary to appropriately stage the lesion. Prognosis has improved substantially with aggressive surgical resection, radiation, and chemotherapy. Local control approaches 100% and long-term survival 86% for patients with non-sacral spinal involvement. Ewing’s sarcoma affecting the sacral region is associated with a 62% local control rate and a 25% long-term survival rate because of the tendency for delayed presentation and large tumour size. C. Soft-tissue sarcoma Soft-tissue sarcomas mainly affect the spine but can affect the vertebral column via direct extension from nearby sites or through metastasis from a distant site. The most common soft-tissue sarcomas are malignant fibrous histiocytoma, liposarcoma, and synovial sarcoma. Neurofibrosarcoma (malignant schwannoma), leiomyosarcoma, clear-cell sarcoma, fibrosarcoma, rhabdomyosarcoma, epithelioid sarcoma, and alveolar soft-part sarcomas are more unusual. Thus, the most favourable results are achieved with en bloc tumour resection followed by adjuvant therapy.

966 Spine D. Chordoma Chordomas are the most common primary malignant tumours of the adult spine, excluding lymphoproliferative tumours and metastases. These tumours arise from remnants of notochord. Most are found in the clivus or sacrococcygeal regions, but when they occur in the spine, second cervical vertebra and the lumbosacral spine are the most common sites. Peak incidence is in the fifth to sixth decades of life, with presentations involving a gradual onset of pain, numbness, motor weakness, and constipation or incontinence .On plain radiography, chordomas appear as destructive lesions and can have an associated soft-tissue mass. Lesions of the spine can show evidence of calcification and might have areas of sclerosis. CT shows both the osseous and soft-tissue components of the tumour and is helpful in assessing neural foraminal involvement. With MRI, chordomas enhance and have low-to-intermediate signal intensity on T1-weighted images and very high signal intensity on T2-weighted images. The histopathology of these lesions reveals long cords of physaliphorous cells. Sarcomatous chondroid, osteoid, or fibroid elements can also be seen within the chordoma. When possible, en bloc resection should be the goal of spine surgeons. If not possible, marginal excision of the tumour along the pseudocapsule combined with adjuvant postoperative radiotherapy, proton-beam treatment, and brachytherapy have been used with varying results. Complete resection is difficult to achieve, but correlates with improved survival. E .Chondrosarcoma Chondrosarcoma is the second most common non-lymphoproliferative malignant tumour in adults after chordoma. The spine has been reported to be the primary site in up to 12% of chondrosarcomas. Presenting symptoms include pain, palpable mass, and neurological symptoms in half of the patients. This tumour most commonly affects middle-aged men, and is most often located in the thoracic spine but can be seen at all levels. Treatment of spinal chondrosarcoma is surgical resection, with cure possible if the lesion is amenable to complete resection. If wide surgical margins are not possible, tumour recurrence is very frequent. Use of radiation and chemotherapy is controversial. F. Solitary plasmacytoma and multiple myeloma Multiple myeloma is a malignancy of plasma cells (B-cell origin) and the spine is the most commonly affected skeletal organ in this population. In about 5% of patients the disease can be diagnosed in the setting of a solitary tumour (plasmacytoma) of bone. Although a solitary plasmacytoma might represent an early stage of multiple myeloma, in some patients long-term disease-free survival or cure can be achieved with local radiotherapy alone. The median survival period of patients with multiple myeloma is 28 months whereas the median survival period of patients harboring a solitary plasmacytoma exceeds 60 months. Pathological fractures are seen in almost 50% of patients with multiple myeloma on plain radiographs alone at the time of diagnosis. A tissue diagnosis can be obtained, especially in the setting of solitary plasmacytoma, with an imageguided core-needle biopsy. The most common vertebral bodies affected by multiple myeloma are the lower-thoracic and upper-lumbar vertebral levels. Although traditional management of vertebral involvement has included conservative treatment, bracing, and

Spinal tumors

967

analgesics, advances, especially with percutaneous procedures, have contributed to progress in the management of patients who have multiple myeloma with symptomatic involvement of the spine. In patients with neurological symptoms or signs resulting from tumour impingement of neurological structures (eg, spinal cord, nerve roots) corticosteroids can improve pain control and neurological deficits. Radiotherapy can be used palliatively or as adjuvant treatment after surgical decompression or stabilisation in the setting of multiple myeloma. In the setting of solitary plasmacytoma, radiotherapy might offer definitive treatment, although surgical decompression might still be necessary in the setting of acute neurological deterioration.In the setting of acute neurological deterioration, surgical decompression might be needed. Complete resection should be attempted, if possible, and the spine should be stabilised when indicated. Surgical stabilisation should also be contemplated in patients with evidence of progressive, symptomatic spinal deformity refractory to conservative treatment. Vertebroplasty and kyphoplasty have received increasing attention in the management of patients with pathological fractures.

Intradural extramedullary (IDEM) tumours The most common primary IDEM tumours are derived from sheath cells covering the spinal-nerve roots (schwannomas and neurofibromas) or meningial cells located along the spinal-cord surface (meningiomas) 4. Myxopapillary ependymomas are extramedullary tumours arising from the conus medullaris and filum terminalis. Other tumour types, such as hemangiopericytomas, lipomas, paragangliomas, epidermoid cysts, and dermoid cysts are less common. These patients most often present with symptoms of spinal-cord compression. Most patients will be symptomatic at the time of diagnosis, and onset of symptoms can precede diagnosis by months to years. Local or radicular pain is the most common presenting symptom especially with tumours located in the lumbar spine. Paresthaesias and numbness are common symptoms, and hypesthesia or anesthesia at and below a level of the spinal cord is often evident on clinical examination. Motor weakness in the form of spastic paraparesis is common too, but findings of monoparesis, hemiparesis, or even paraplegia might be present at diagnosis. Sphincter dysfunction can develop early in the course of the disease, especially with tumours of the cauda equina. Ataxia, torticollis, and skeletal deformities are less common presenting symptoms. A. Nerve-sheath tumours Schwannomas and neurofibromas account for up to a third of intradural spinal-cord tumours in the adult population but are less common in children 3,4. Peak incidence of nerve-sheath tumours is in the fourth to fifth decade of life, and there is equal incidence in both men and women. Schwannomas are more common than neurofibromas and usually present as solitary tumours. Occasionally, multiple spinal schwannomas are seen with neurofibromatosis type II. Neurofibromas often show multiplicity, especially when associated with neurofibromatosis type 1. About 60–80% of nerve-sheath tumours arise from nerve roots before leaving the dural sac 4. A further 10% arise as the nerve root leaves the dural sac and becomes surrounded by the dural-root sleeve. These tumours,

968 Spine therefore, display both intradural and extradural components (dumbbell tumour). Nerve-sheath tumours that are entirely extradural or intramedullary are less common. Intradural nerve-sheath tumours most commonly affect the lumbosacral region, but cervical and thoracic tumours have been reported too. Intradural nerve-sheath tumours might be more common in the lumbosacral region because of the longer intradural segment of the caudal spinal-nerve roots in the neuraxis. Nerve-sheath tumours are generally regarded as benign neoplasms, but can be malignant in a few cases, where they are designated the term malignant peripheral nerve-sheath tumours. Although more than 50% of malignant tumours are associated with neurofibromatosis type 1, only a small percentage of patients with this disease have malignant neoplasms. Anatomically, schwannomas tend to arise from the dorsal-nerve root whereas neurofibromas are more common on the ventral root. Other than this difference, schwannomas and neurofibromas are indistinguishable on MRI. Nervesheath tumours have an isointense signal on T1-weighted images and a hyperintense signal on T2-weighted images. Gadolinium adds variable enhancement ranging from a homogeneous to a peripheral ring-like enhancement. Although an irregular enhancement pattern is associated with malignant tumours, differentiation from benign entities is unreliable with radiographic methods. Histologically, schwannomas display neoplastic Schwann cells without nerve fibres. Neurofibromas more frequently invade the nerve root, and display Schwann cells, nerve fibres, and fibroblasts. The primary treatment of nerve-sheath tumours is directed at total surgical resection, which is obtainable in most cases. Subtotal resection of these tumours might be an option when the tumour is attached to the spinal cord, or when the tumour exhibits an extradural component closely associated with vital structures, such as the vertebral artery in the cervical region. To obtain total resection, the ventral or dorsal roots are commonly sacrificed; however, resection of the nerve root is usually not associated with pronounced postoperative motor or sensory deficit. Because schwannomas arise from dorsal-nerve roots and are less invasive than neurofibromas, surgical resection less often results in pronounced motor deficits than does resection of neurofibromas. Postoperative morbidity can be affected by spinal location of nerve-sheath tumours, with cervical and thoracic lesions predicting worse neurological outcome than more caudal sites. Radiotherapy or chemotherapy is usually reserved for tumours that have malignant histological characteristics. Tumour recurrence is less than 5% and might have a high association with subtotal tumour removal. B.Meningioma Spinal meningiomas account for up to 46% of spinal neoplasms, and are more common intradurally than extradurally 4. A small percentage of spinal meningiomas are located extradurally, and extension of these tumours into the intradural compartment is common. The thoracic level is the most frequent site for spinal meningiomas, and these tumours have a predilection for women in the fifth to seventh decade of life. On MRI, spinal meningiomas have a hypointense to isointense signal on T1-weighted images and a hyperintense signal on T2-weighted images. The addition of gadolinium contrast gives strong homogeneous enhancement. Most intradural meningiomas are noninvasive, benign neoplasms, helping with gross total resection of the tumour. Even

Spinal tumors

969

when considering the technical challenges of anterior locations, total surgical resection of meningiomas is attainable in more than 90% of patients. The tumour recurrence rate with total or subtotal resection is between 3% and 7%. Radiotherapy could be considered after subtotal resection or recurrence of spinal meningiomas by analogy with management of intracranial meningiomas. C. Myxopapillary ependymoma Myxopapillary ependymomas account for roughly 40–50% of spinal ependymomas and are more common in the adult population than in children. Ependymomas of the myxopapillary variant arise in the filum terminalis and account for up to 80% of ependymomas found in the cauda equina. This variant is distinguished from other ependymomas by the mucinous changes undergone by the tumour cells. Patients normally present with a long history of radicular pain, lower extremity sensorimotor deficit, and sphincter dysfunction. Myxopapillary ependymomas are typically benign, well-circumscribed tumours. MRI reveals a circumscribed mass with hypointense signal on T1-weighted images and hyperintense signal on T2-weighted images. Contrast enhancement with gadolinium is usually homogeneous. Histologically, myxopapillary ependymomas display ependymal rosettes or perivascular pseudorosettes, with the characteristic deposition of myxoid material around blood vessels. Total surgical resection of myxopapillary ependymomas is feasible if the nerve roots in the cauda equina are not entrapped within the tumour. In an attempt to keep to a minimum postoperative neurological morbidity, subtotal resection is not uncommon. Focal fractionalised radiotherapy seems to be effective at improving neurological outcome and reducing tumour recurrence rate after subtotal tumour resection or piecemeal total excision. Recurrence of wholly resected tumours is generally rare, but is associated with a poor outcome. These tumours can seed the spinal subarachnoid space, in which case broader field radiation is used, but this is uncommon. Although chemotherapy is sometimes started for recurrent or disseminated myxopapillary ependymomas, results are unconvincing. D. Paraganglioma Paragangliomas are derived from autonomic-nervous-system paraganglion cells and are uncommon in the CNS. Spinal paragangliomas are generally non-secreting, sympathetic neoplasms, which tend to occur in the fourth to fifth decade of life and show a male predominance. The most frequent intradural location for paragangliomas is the cauda equina and lumbar spine regions, apart from intradural thoracic or cervical paragangliomas. On MRI, paragangliomas present as a well circumscribed mass with a hypointense to isointense signal on T1-weighted images and a hyperintense signal on T2weighted images. Paragangliomas are characteristically hypervascular, and gadolinium contrast administration produces a heterogeneous salt and pepper pattern of enhancement. Scanning using radiolabelled metaiodobenzylguanidine (mIBG), a noradrenaline analogue with uptake independent of catecholamine secretion, can allow visualisation of paragangliomas. Histological appearance of paragangliomas displays a highly vascularised tumour bed containing round and polygonal cells grouped in

970 Spine clusters called zellballen. Intradural paragangliomas are mainly benign neoplasms, and gross total surgical resection is the preferred treatment. Although catecholaminesecreting spinal paragangliomas are uncommon, preoperative screening for a hyperadrenergic state is necessary to prevent hypertensive crisis during tumour removal. Recurrence rate after total or subtotal resection of intradural paragangliomas is less than 5% and is not reduced by concomitant radiotherapy or chemotherapy. Although iodine-131 labelled mIBG (131I-mIBG) can slow progression and improve remission rate for metastatic paragangliomas, efficacy in primary intradural paragangliomas is unproven. E. Dermoid and epidermoid cysts Dermoid and epidermoid cysts are usually congenital neoplasms arising from heterotopic ectodermal-cell implantation into the neural tube early in embryonic development. Dermoid and epidermoid cysts represent only 1% of CNS tumours, and are rarely located in the spinal column. These tumours most commonly affect the lumbosacral region, with rare reports of thoracic involvement. Dermoid and epidermoid cysts are usually diagnosed in the first two decades of life, with dermoid cysts presenting earlier than epidermoid cysts On gross appearance, dermoid cysts can be differentiated from epidermoid cysts by the appearance of skin appendages such as hair follicles; however, the distinction between these tumours is often difficult by imaging. Both intradural dermoid and epidermoid cysts have variable MRI appearance, with hypointense to hyperintense signal on T1-weighted images and isointense to hyperintense signal on T2-weighted images. There is usually minimum enhancement with gadolinium. Gross total resection of dermoid and epidermoid cysts is desirable when possible, but adhesion to neural tissue can prevent aggressive techniques. When subtotal resection is done, emptying of the cystic contents and removal of a portion of the capsule is encouraged. Dissemination of the cystic contents spontaneously or during tumour removal might produce a granulomatous meningitis treatable with corticosteroids. Recurrence of resected intradural dermoid and epidermoid cysts is uncommon, and malignant tumours are rare. F. Lipoma Lipomas are congenital, benign tumours uncommon in the intradural compartment are usually associated with spinal dysraphism in about a third of cases. Children are more commonly affected than adults. Intradural extramedullary lipomas are usually located in the lower thoracic and lumbosacral levels.On MRI, intradural lipomas have a hyperintense signal on T1-weighted images and a hypointense signal on T2-weighted images. Microscopically, lipomas consist of mature adipose cells and connective tissue. Decompressive surgical resection is recommended for symptomatic intradural lipomas. When there is widespread involvement of the cord, conus, or nerve roots, subtotal resection is usually undertaken to prevent postoperative morbidity. Intraoperative electrophysiological stimulation with evoked EMG monitoring is often used to allow differentiation between the functional spinal cord and the mass. When unassociated with a tethered cord, prophylactic resection of asymptomatic lipomas of the filum terminalis can prevent subsequent neurological decline.

Spinal tumors

971

G. Extramedullary metastasis Intradural extramedullary spinal-cord metastasis is extremely rare and seen at autopsy in fewer than 5% of patients who have died from cancer. These tumours are commonly the result of drop lesions from intracranial metastasis from adenocarcinoma of the lung, prostate cancer, breast cancer, melanoma, or lymphoma or alternatively, intradural extramedullary metastases represent drop lesions from intracranial neoplasms such as gliomas and medulloblastomas. Intradural extramedullary metastases are most common in the thoracolumbar or thoracic spine. As intradural extramedullary metastasis usually indicates advanced widespread progression of the systemic malignancy, aggressive surgical resection of lesions is usually not done. Treatment is, therefore, directed towards palliative and functional goals. Adjuvant treatment with intravenous or oral corticosteroids can improve neurological function as well and provide symptomatic relief.

Intramedullary spinal cord tumours Intramedullary tumours of the spinal cord account for 2- 4% of CNS neoplasms and about 20 – 25% of all intraspinal tumours 4,5,6. Intramedullary tumours compromise about one third of spinal neoplasms in adults. Astrocytomas and ependymomas account for more than 80% of intramedullary tumours in most series 5,6,7. Despite modern advances intramedullary surgery remains a formidable undertaking. However the earlier pessimistic outlook has paved way to optimism over the years ever since the first successful removal of an intramedullary tumour by Malis 8, Greenwood 9, Rand 10, Yasergill 11, Stein 5 all were strong proponents in favour of surgery .The most vocal proponent for aggressive surgery in recent years has been Epstein 11-16. Management philosophy of intramedullary tumours It has now been established that long term tumour control or cure can be achieved with acceptable morbidity by microsurgical removal alone for nearly all ependymomas, hemangioblastomas and other well circumscribed lesions which include many astrocytomas as well. It is the surgeon’s intraoperative identification of a tumour /cord interface that is the most important determinant of resectability . Aggressive surgery is of no value for malignant intramedullary tumours and frozen section identification of malignancy signals an end to operation. Conversely if histological identification reveals a benign ependymoma , gross total resection should be the goal even if the margins of the tumour are not immediately evident. So as observed by MCCormick and others 7,11-16 it seems reasonable to assume that all patients harbour a benign lesion for which definitive surgical removal is the treatment of choice. Intraoperatively after adequate myletomy, if the surgeon identifies a clear demarcation from the surrounding spinal cord he should attempt total removal. The effect of radiation therapy on intramedullary spinal cord tumours has not been proven and is obscured by the lack of knowledge of the natural course of these tumours and by the lack of follow up findings confirming the reduction of tumour size after radiation therapy. The goal of surgery is to remove the tumour totally with preservation or improvement of neurological function. These objectives cannot be always achieved because some tumours infiltrate adjacent neural tissue and make total removal impossible without

972 Spine incurring an unacceptable loss of function. Even when a tumour is well delineated from the normal spinal cord, removal may result in a permanent increase in neurological deficit. The diagnosis of an intramedullary tumour does not necessarily mandate operative removal. The decision to operate on patients with far advanced neurological deficits must be made with realistic expectations. Recovery from a significant longstanding deficit rarely occurs. Neurological outcome is directly related to patients preoperative status. Neurological improvement from a preoperative major deficit can be modest and seen only in a minority of patients. Usually it is the minor deficits which are likely to improve. Thus the major benefits of intramedullary tumour removal is prophylactic. Most patients experience some degree of neurological morbidity in the immediate postoperative period. This brings the issue of managing a patient who presents with neck or back pain with very little objective deficits. Many such patients with minor symptoms and no significant functional impairment are unwilling to risk neurological deterioration as a result of operation. In this situation, the patient should be followed closely for the appearance of additional symptoms or an objective deficit. Once the symptoms progress, patients frequently are more prepared psychologically to face the risks of surgery. There is no therapeutic role for operation in patients harbouring malignant intramedullary tumours because surgery usually results in significant neurological morbidity and also there is the theoretical risk of secondary cerebrospinal fluid dissemination. But preoperative prediction of histology based on MRI scan characteristics alone should be avoided as they are often incorrect and may unfairly influence the surgical objective. So the surgeon should assume that the majority of intramedullary tumours are benign and are potentially resectable. Because ependymomas cannot be distinguished reliably from astrocytomas by their clinical presentation or currently available imaging techniques, all intramedullary spinal cord tumours must be explored aggressively so that curable lesions are not overlooked. An attempt at radical removal should be made according to the gross rather than histologic tumour characteristics because some low grade astrocytomas are also well circumscribed and amenable to radical resection. Histologic interpretation of tiny biopsy fragments obtained through a limited myelotomy is frequently inaccurate. An inadequate myelotomy may fail to reveal a clear resection plane and histologic interpretation of tumour specimens can result in erroneous tissue diagnosis. It is of paramount importance that surgeon gets a correct tissue diagnosis because under certain circumstances biopsy results define the surgical objective. Frozen section identification of a malignancy signals an end to the operation and no aggressive tumour removal is undertaken. If histological examination clearly demonstrates a benign pathology every attempt should be made for a gross total removal even if the margins of the tumour are not immediately evident to the surgeon. Recurrence and role of radiotherapy : Although ependymomas are considered benign by some their glial derivations , lack of capsulation and friable nature pose a risk of recurrence. These lesions are best managed by total removal. We do not recommend radiotherapy after total removal of ependymomas . No efficacy of radiation therapy following grossly complete removal of a spinal ependymomas has been demonstrated and adjuvant radiotherapy is best

Spinal tumors

973

reserved for patients with malignant ependymomas or a tumour that cannot be resected totally. In an young patients with obvious tumour recurrence who is in good neurological condition , reoperation is the recommended strategy. Contrary to the finding in children , astrocytomas in adults pursue a progressive course. It seems unlikely that radical tumour removal significantly effects survival. Risk of recurrence is high almost all our patients who came for follow up showing progressive neurological deterioration. Reoperation is best deferred until the patent becomes symptomatic because the interval between MRI and clinical evidence of recurrence may extend several years. Well encapsulated benign lesions who were operated in good neurological state fared better. There is no place for radiotherapy without histological diagnosis or any indications for its use in treating intramedullary tumours except in high grade gliomas which are very rare. A. Ependymomas They originate from rests of ependymal cells in the centre of the spinal cord and appear as a soft red or greyish purple mass with a variable number of vessels crossing the tumour surface. As they grow from their point of origin, they push the adjacent spinal cord aside and therefore are distinct from the surrounding spinal cord and can be dissected from it. If the frozen section report is an ependymoma every attempt is made to remove the tumour in toto. The myelotomy is lengthened and deepened to fully expose the entire rostrocaudal extent of the tumour and should actually continue a few millimetres above and below the tumour margins, allowing greater lateral retraction and visibility while minimizing tension on the spinal cord. Although these tumours are somewhat friable, they are sharply circumscribed and gentle blunt manipulation will not violate the tumour surface. The rostral tumour is frequently rounded and often projects into a cyst which aids in dissection. The caudal pole is usually more tapered since inferior cysts are less common, but there is often a tough fibrous connection between the caudal tumour pole and the central canal. In the absence of a rostral or caudal cyst, the tumour resection is initiated in the middle of the neoplasm which is the most voluminous area. In the presence of a polar cyst, the resection is initiated at the cyst-tumour junction where the interface between the tumour and the normal tissue is easily obtained. The dorsal and lateral margins are established by gentle traction on the tumour against the counter traction provided by the pial sutures. Spreading the microforceps parallel to the long axis of the tumour easily develops the dissection plane, owing to the differences in texture and consistency between the tumour surface and the surrounding gliotic margin of the spinal cord. Feeding vessels and more fibrous attachments are cauterised and divided close to the tumour. The decision to debulk the tumour internally is made once the dorsal half of the tumour is exposed. Although smaller lesions may be removed in one piece, generally the bulk of the tumour should be reduced first. The most important technical point is that there is no effort to carry an en bloc resection. The bulk of the tumour will hinder exact visualisation of the dissection plane requiring prohibitive amounts of spinal cord retraction if one attempts en bloc resection. The dorsal tumour surface is incised and internal decompression is performed with an ultrasonic aspirator. Too much internal tumour removal may cause fragmentation of the tumour surface and obscuration of the correct dissection plane resulting in an undesirable piecemeal

974 Spine removal. As the centrum of the tumour is decored the lateral margins gradually fold in establishing the tumour -cord interface. This cleavage may be accomplished by retraction of the remaining tumour tissue into the residual cavity and not by retraction of spinal cord from the tumour. Dissection of the ventral plane is the most difficult aspect of tumour removal. This is because pial traction sutures do not transmit effective counter traction to the ventral interface between cord and tumour. Also tumour margins appear less distinct and requires sharp dissection techniques. The anterior median fissure extends almost to the central canal and the tumour is in close approximation to the anterior spinal artery and branches. With superior traction on the tumour directed perpendicular to the long axis of the spinal cord, the tumour can be separated from anterior spinal vessels, which are identified, cauterised and divided. Dissecting the poles of the tumour is more difficult. If a cyst is present, the end of the tumour is obvious. If there is no cyst, the tumour tapers into a root that blends into the central canal of the cord. Following tumour removal , the resection bed is inspected and any bleeding is controlled with warm saline irrigation and application of surgicel. The pial traction sutures are removed and the cord assumes its normal position. No attempt is made to reapproximate the dorsal hemi cords with pial sutures. A watertight dural closure is generally possible in primary operations. In secondary procedures or if closure of dura would in any way narrow the subarachnoid space a dural graft using fascia lata or lumbodorsal fascia or lyophilised cadaver dura is frequently neseesary. Permanent coloured sutures are used because it will provide a midline orientation in case reoperation is required for recurrent tumours. Special attention is paid to the fascial layer as this is usually the watertight layer. Fascia and muscles should be released from the superficial subcutaneous tissues and deep bony elements to achieve closure with no tension. Finally the skin is closed after putting deep and superficial subcutaneous sutures. B. Astrocytomas The surgical treatment of intramedullary astrocytomas remains a much more formidable problem than ependymomas. Adult spinal cord astrocytomas are infiltrating tumours that are histologically similar to intracranial astrocytomas. Usually they are located several millimeters beneath the dorsal surface of the cord and although they may be distinguished by their yellowish gray glossy appearnce from the surrounding spinal cord, they blend imperceptibly with the spinal cord at the margins. Many have reported that a radical resection of these infiltrative lesion will result in a higher morbidity and advice only a generous, but limited internal decompression. More radical tumour removal until the establishment of the tumour-cord interface will not alter the clinical course in adults with malignant astrocytoma. However there have been reports of radically resected astrocytomas without increased morbidity. In our experience the surgery on this subgroup of patients has not been always associated with higher postoperative morbidity, but the rate of radical resections has been definitely lower than that for other tumours. Because these malignant astrocytomas recur with in a year independent of amount of resection, we agree that a less radical intervention with minimal surgical morbidity is the ideal treatment. The lower grade lesions are avascular and lend themselves to radical resection. In children these tumours behave similarly to low grade posterior fossa astrocytomas which are amenable for total resection. After

Spinal tumors

975

biopsy confirmation of histology an internal decompression is carried out using cavitron. These well circumscribed astrocytomas will often have a well defined dorsal surface plane with white matter but often fade imperceptibly into the gray matter. An ”inside-out” removal is recommended and is dictated by surgeon’s ability to differentiate clearly, on the basis of colour and consistency, tumour from the surrounding spinal cord. While many low grade astrocytomas have discrete cleavage planes and adjacent cystic components and a fibrillary character on histological examination some have extensive areas with poorly defined interface. In these areas the only guidance to tumour removal is progressive change of colour and tissue consistency. Whenever the tumour comes close or reaches the subpial surface, especially the ventral one, no attempt is made to pursue a radical resection. Although approximately two thirds of all spinal cord astrocytomas in adults are not histologically malignant lesions, they behave in a less-than benign fashion. By virtue of their location and tendency to infiltrate, even small tumours can produce severe neurological deficits. Recurrence after incomplete resection and malignant transformation can occur like their cranial counterparts. The surgical techniques for astrocytomas are similar to ependymomas. Under magnification, the tumour which presents subpially, may be distinguished from the normal spinal cord by colour and texture. By first opening the cyst, the dissection plane can be more readily identified than by trying to attack the tumour-cord interface directly. Pial traction microsutures are as useful in this tumour as with ependymomas. In the presence of a cystic holocord astrocytoma, tumour removal is initiated either at the rostral or caudal pole in the region of tumour-cyst junction. Excision of the solid noncystic astrocytoma is initiated in the mid portion rather than at the rostral or caudal pole of the neoplasm because there is no clear rostral or caudal demarcation of the tumour as occurs in caudal and rostral cysts. The last fragments of the rostral and caudal segments of the tumour are removed by working within the myelotomy and distracting the residual neoplasm into the surgical cavity without extending the myelotomy. Intraoperative ultrasound helps to monitor the progress and clearly identify the rostral and caudal extent of the tumour. Ultrasound also gives a very precise image of the cross sectional image of the tumour cavity and its relationship to the anterior subarachnoid space. Because residual tumour is always present dura is closed with a dural patch to avoid constricting the spinal cord. C. Hemangioblastomas Hemanhiobalstomas is a pial based neoplasm and simulates an arteriovenous malformation with respect to vascularity and aretriovenorus shunting. They account for 3 – 8% of intramedullary neoplasms. These tumours which are well encapsulated always have a dorsal or dorsolateral pial attachment thus obviating the need for myelotomy. Patients with von Hippl Lindau syndrome are more likely to have multiple tumours as well as a nerve root origin or purely leptomeningeal location of hemangioblastoma. No attempt should be made to enter this highly vascular tumour until its vascular supply is interrupted totally. These tumours separate easily from the surrounding neural tissue and all dissection and manipulation should be done on the surface of the tumour. Dissection should proceed around the tumour with cauterisation of the tumour capsule and coagulation and cutting of the feeding arteries. Removal of the

976 Spine tumour is facilitated by excision of the pial attachment as part of the tumour mass. Buried portion of the tumour within the spinal cord is easily dissected and delivered with taction on the pial base. This dissection exposes additional vascular supply which should be interrupted progressively allowing total removal .Using this technique , even large tumours will become less turgid and ultimately delivery of the initially non visualised tumour capsule into the operative field will occur. Is is advisable to preserve at least one venous pedicle until all the feeding arteries are divided. Purely intramedullary hemangiobalstomas or those with a ventral pial surface presentation are approached through a standard midline myelotomy. Sometimes intramedullary spinal hemangiobalstomas is associated with spinal cord swelling which may extend a considerable distance above and below the tumour. Although the cysts may be responsible for the cord swelling in some cases, it is more common to encounter an oedematous appearing spinal cord. The cause of this cord swelling remains unclear , but this oedema resolves following removal of the tumour . Hemangiobalstomas may recur a a result of growth of residual tumour or as is more commonly the case , growth of additional tumours that were clinically or radiographically unapparent at the time of first surgery. D. Lipomas These tumours are histologically identical to normal adipose tissue and are locate in the dorsal surface of the spinal cord covered by little or no neural tissue. Lipoma is an example of a subpial tumour and is entirely enclosed within an intact pia layer. It is not a true neoplasm , but probably arising from the disordered embryogenesis with inclusion of mesenchymal tissue. These lesions generally enlarge and produce symptoms in early and middle adult years through increased fat deposition in these metabolically normal fat cells. Although distinct from adjacent spinal cord and non invasive , these lesions adhere densely to normal spinal cord and so total removal is impossible without incurring unacceptable neurological deficits. A longitudinal pial incision and over the entire extent of the lesion and conservative subtototal internal decompression leaving a rim of tumour behind at the interface with the spinal cord is the most effective operative strategy. The laser is an ideal tool for removal of these lesions because the fibrous interstices of the lesion make removal with ultrasonic aspirator difficult.

Other lesions Include metastatic lesions, gangiogliomas. , oligodendrogliomas and epidermoid cysts and the problems they present to the surgeon are similar to those posessed by tumours discussed previously. Surgical techniques for intradural spinal tumours Awake intubation must be considered especially in the cervical lesions. The patient is given prophylactic antibiotics and steroids. For cervical lesions use of bolsters with head pin fixation with the neck in neutral position is preferred. The level is localized on the skin by preoperative imaging or intraoperative fluoroscopy or plain X rays. Electrophysiological monitoring for sensory evoked potentials, direct EMG recordings from appropriate muscle groups as well as motor evoked potential where available

Spinal tumors

977

should be undertaken. The majority of posteriorly situated lesions can be approached through a posterior approach, while those extending out of the neural foramen can be managed through an extension using a posterolateral approach, involving a facetectomy or drilling of the pedicle. For lesions extending into the thoracic or retroperitoneal cavity, a posterolateral transpedicular or costotransversectomy approach or a staged procedure involving a separated transthoracic , thoracoendoscopic or a retroperitoneal approach may have to be utilized. In the cervical lesions extending into the retropharyngeal space a separate anterior approach after decompression of the spinal cord through a posterior approach is recommended. The question of stabilization will be dictated mainly by the extent of bony and ligamentous removal , age of the patient and any other associated risk factors for acute or delayed spinal instability. As a general principle minimal instability should be created during the exposure, but not at the risk of neurological injury due to inadequate exposure. For a younger patient when multiple levels are involved a laminotomy is recommended to prevent long term forward flexion and instability, though its efficacy in reducing the risk of post laminectomy deformity is not proven. In adult spine laminoplasty or osteolaminotomy are rarely used. The laminotomy procedure involves drilling of the lamina at the lateral margin with a high speed drill and the ligament flavum in the rostral and caudal most vertebrae is cut so as to leave enough ligament to be able to stitch closure of the lamina on the side and repair the wires postoperatively. Removal of the facet unilaterally especially in the thoracic spine does not lead to instability, however multiple levels in any region should lead to consideration of stabilization after tumour removal. If after facet removal the medial column or anterior column is destroyed by either the tumour or surgical exposure then fusion is recommended. The type of fusion depend on the anatomical area, with posterior fusions in the lumbar area involving pedicle screw fixation, pedicle screws or spine and laminar hooks for the middle nd upper thoracic area, laminar plates for the cervical spine and transpedicular C1-2 screws or occipito cervical fusion rods for the extreme upper cervical spine. The rare anterior resections require anterior graft plus instrumentation. The bone from the laminectomy should be kept to be used as bone graft. This can be supplemented by demineralised bone matrix and autologous iliac crest bone. Other surgical principle as in any spinal vase includes prepping a long portion of the spinal column just in case additional exposure is required. Sub periosteal exposure of the lamina is undertaken to minimize bleeding. High speed drilling out laterally in the lamina with minimal use of rongeur footplates under the lamina thereby compressing the spinal even further is recommended. For posterolateral procedures drilling of the pedicle with minimal disturbance of the facets is undertaken using the microscope and the high speed drill. After bony removal the tumor is usually visualized readily with rare need for intraoperative ultrasound .The dura is opened in the midline, sparing the arachnoid and extended laterally over the root sleeve for those IDEMs with foraminal extension trying to preserve the arachnoid. Dural tack up stitches to extend the dural opening which should go beyond either pole of the lesion is undertaken followed by opening of the arachnoid and using wet clips to temporarily adhere them to the dural opening . Cottonoid are placed circumferentially along the surgical field with bone wax and gel

978 Spine foam used as required to keep the field dry. Full extent of tumour needs to be exposed with lamniotomy one level above and below the level of the lesion. Intradural schwannomas have a good plane of cleavage and generally deliver out once the arachnid covering is excised. Part of the dorsal root may have to be sacrificed to ensure total excision. Added ventral exposure can be obtained by extra bone drilling, giving side cuts on the dura, cutting the dentate ligamanes and gentle retraction using the denticulate ligaments. Ventrally placed meningiomas pose considerable challenge and excision of the dural attachment is difficult at times. Dural closure is done watertight using a patch if needed. The principles of surgical techniques for an intramedullary tumour 6,7,11-16 used can be summarised as follows: 1. Full extent of tumour to be exposed with lamniotomy one level above and below the level of the lesion 2. Dural opening sparing the arachnoid 3. Cord opened through a midline myleotomy or through the most widened avascular part of the cord. 4. Initially 1 – 2 cm myelotomy done over the greatest enlargement and to be extended over the entire rostrocaudal limit of the tumour. 5. Myeleotomy deepened gently by spreading microforceps in longitudinal axis and tumour surface identified. 6. Both tumour poles identified and polar cysts entered. 7. Apply pial traction sutures for better visualisation and to provide counter traction for development of dorsal and dorsolateral tumour plane. 8. Retraction of the tumour done rather than the cord. 9. Biopsy obtained for histological confirmation. 10. Dissection done from one end. Internal decompression if tumour is bulky and hinders dissection plane. 11. Dissection of the ventral plane done last and supply from anterior spinal vessels are cauterises and divided. 12. Dura closed primarily or using a dural patch graft 13. Useful intraoperative adjuncts include SSEP, intraoperative ultrasonography, CUSA, LASER.

Surgical outcome The early and long term outcome in patients following removal of intradural extramedullary lesions is related to multiple factors including patient age and neurological status , location and histology of the tumour. In case of IDEMs the outcome is generally favourable except in certain exceptional cases mentioned earlier. Young age and a good preoperative neurological grade facilitate good outcome. In case of intramedullary tumors in the immediate post operative period , most patients demonstrate some degree of neurological deficit especially of motor symptoms and posterior column function. These deficits are usually transitory and recover within a few months particularly the motor deficits. Posterior column dysfunction also tends to improve but not to the pre operative level. Sometimes, this dysesthetic syndrome may persist often

Spinal tumors

979

causing causalgia like complaints. Other immediate post operative complications include CSF leak, infection and wound dehiscence especially with dorsal wounds. Late complications include hydrocephalus, post operative spine deformity and anterior subarachnoid CSF loculations.

Conclusions The importance of familiarity with primary tumours of the bony spine and adjacent soft tissues cannot be overemphasized. Radiographic assessment combined with histological examination helps with the identification of the histogenesis of these tumours, which is vital when exploring surgical and adjuvant treatment options and patient management. Depending on the nature of the lesion, patient treatment plans can be further individualised. Treatment by a multidisciplinary team approach will lead to the best possible outcome.

REFERENCES 1. JN Weinstein, Surgical approach to spine tumors, Orthopedics 1989;12:897–905 2. WF Enneking, SS Spanier and MA Goodman, A system for the surgical staging of musculoskeletal sarcoma, Clin Orthop RelatRes 1980;153:106–120. 3. DE Traul, ME Shaffrey, D Schiff Part II: Spinal-cord neoplasms - primary tumours of the bony spine and adjacent soft tissues. The Lancet Oncology, 2007;8(2):135-147 4. DE Traul, ME Shaffrey, David Schiff Part I: Spinal-cord neoplasms - intradural neoplasms. The Lancet Oncology(2007); 8 (1): 35-45 5. BM Stein, PC McCormick. Intramedullary neoplasm and vascular malformations. Clin Neurosurg 1991; 39: 361 –87. 6. S Nair, G Menon, BRM Rao, BJ Rajesh, T Muthuretnam, A Mathew, HV Easwer, RN Bhattacharya. Intramedullary spinal cord glial tumors: management philosophy and surgical outcome In Minimally Invasive Neurosurgery and Multidisciplinary Neurotraumatology. Ed T Kanno & Y Kato, Springer-Verlag, Tokyo, 2006, 36-46. 7. PC McCormick. Anatomic principles of intradural spinal surgery . Clin Neurosurg 1993; 41: 204 –23. 8. L Mallis . Intamedullary spinal cord tumours. Clin Neurosurg 1960; 17:310 – 30. 9. J Greenwood Surgical removal of intramedullary tumours. J Neurosurg 1967;26: 276 – 82. 10. RW Rand Intraspinal removal of IM tumour J Neurosurg 1967;23:276 – 282 11. MG Yasergill Microsurgical removal of intramedullary hemangioblastoma. Surg Neurol 1976;6: 141 – 148. 12. F Epstein, M Lee, AR Rezal. Intramedullary spinal cord lipomas. J Neurosurg 1995; 82 : 390 – 400. 13. FJ Epstein Adult intramedullary astrocytoma of the spinal cord. J Neurosurg ; 1992;77: 355 –59. 14. FJ Epstein. Adult intramedullary spinal cord ependymoma . J Neurosurg 1993;79:205 –09. 15. FJ Epstein, N Epstein. Surgical management of holocord intramedullary spinal cord astrocytoma in children : report of 3 cases. J Neurosurg 1981; 54 : 829 – 32. 16. S Nair, KM Pai, G Menon, R Kachhara, NI Kurien. Management of intramedullary lesions. Progress in Clinical Neurosciences 1997; 12: 331 – 43. 17. S Nair, G Menon, S Parameswaran, RN Bhattacharya: Techniques of removal of intramedullary lesions. Indian Clinical Neurosurgery, Ed: AK Singh; 2001, Vol 1 :17896.

980

Current Management of Intramedullary Spinal Cord Tumors JACQUES BROTCHI MD, PhD, FLORENCE LEFRANC MD, PhD, RYAD DJEDID, MD and MICHAEL BRUNEAU MD Departments of Neurosurgery, Hôpital Erasme, Université Libre de Bruxelles, 808, Route de Lennik, B-1070, Brussels, Belgium Key words: intramedullary spinal cord tumors, gliomas, ependymomas, astrocytomas, hemangioblastomas, cavernomas

Introduction Intraspinal cord tumors are relatively rare and present the neurosurgeon with unique challenges. They account for 2 to 4 percent of central nervous system tumors in adults. In children, the proportion is more or less the same, though it is higher (12%) during the first year of life. Most spinal cord tumors are of glial origin (ependymomas, astrocytomas,) but non-glial lesions are not rare (hemangioblastomas, cavernomas). In this chapter, we shall focus on these four most frequent spinal cord pathologies only putting aside rare lesions like dermoid and epidermoid cysts, metastatic tumors and lipomas, which raise different problems and approaches. The event of Magnetic Resonance Imaging (MRI) has brought revolutionary changes in that area, so as the progress in neurosurgical techniques. Now, the majority of these tumors are curable with good quality of life expectancy when an adequate strategy has been adopted at first surgical procedure. On the other hand a second surgery after unsuccessful surgical approach, usually resulting in damage and scarring, is very difficult and associated with high level of worsening.

Clinical Findings Spinal cord tumors have no typical clinical presentation. The initial presentation may consist of sensory disorders, torticollis, back pain, motor disorders, urinary dysfunction, scoliosis, myoclonus, rarely papilledema, subarachnoid hemorrhage or hydrocephalus mainly in children. Most commonly, adult patients complain of back or radicular pain, or paresthesias. Children present with scoliosis or neurological complain. The clinical course may be insidious (during several years), abrupt in onset, or may progress episodically. The neurological presentation is related to the level of the lesion. However, it is not unusual to see patients with cervical intramedullary tumor who have no sensory or motor deficit in the upper extremities. In patients with tumor involving the conus, the expected sphincter dysfunction may be absent. We found the McCormick classification (table 1) very useful, taking into account both sensory and motor deficits to grade the state of the patients’ clinical functioning at the time and after operation.

Current Management of Intramedullary Spinal Cord Tumors

981

Table 1

Clinical/functional classification scheme (McCormick et al. 1990) Grade I

Neurologically normal; mild focal deficit not significantly affecting function of involved limb; mild spasticity or reflex abnormality ; normal gait.

Grade II Presence of sensorimotor deficit affecting function of involved limbs; mild to moderate gait difficulty; severe pain or dysesthetic syndrome impairing patient’s quality of life; still functions and ambulates independently. Grade III More severe neurological deficit; require cane/brace for ambulation or significant bilateral upper extremity impairment; may or may not function independently. Grade IV Severe deficit; requires wheelchair or cane/brace with bilateral upper extremity impairment; usually not independent.

Pathology Three main groups can be distinguished: tumors of glial origin, tumors of non-glial origin, and pseudotumors.

Tumors of glial origin Ependymomas are the most frequent intramedullary tumor in adult patients. Slowly developing, they may grow to considerable size, sometimes affecting the entire spinal cord (holocord ependymomas) before they become clinically detectable. The majority of the spinal cord ependymomas are grade II in the WHO classification and they are associated with a good prognosis. Grade III anaplastic ependymomas located in the spinal cord are very rare. Unlike ependymomas, spinal cord astrocytomas occur more frequently in children than in adults. Spinal cord astrocytomas often correspond to grade II of the WHO classification. Malignant anaplastic astrocytomas are rare. They correspond to grade III of the WHO classification. Glioblastomas (grade IV) are even less common. Other gliomas like oligodendrogliomas and gangliogliomas are quite rare tumors. Their course is a function of their histological grade, and is in every respect comparable to that of astrocytomas. Tumor grade was consistently reported as the major factor affecting prognosis.

Tumors of non glial origin Hemangioblastomas and cavernomas are the most frequent spinal cord tumors of non-glial origin. They are vascular benign tumors, well delineated and sometimes multifocal. Hemangioblastomas can present either sporadically or in association with von Hippel-Lindau (VHL) syndrome in 20% of cases. All patients with an apparently

982 Spine isolated central nervous system hemangioblastoma should be investigated for evidence of VHL disease. Hemangioblastomas frequently have an associated cyst, and are often attached to the leptomeninges due to their subpial location but they may rarely also be pure intramedullary tumors. The lesions consist of capillaries lying next to each other, separated by foamy cells. The gliosis adjacent to the tumor may be particularly profuse and simulate a glioma.

Pseudotumors The most common lesions are demyelinating disease whose histological features are the same as in the brain. Sarcoidosis has also been described as a primary spinal cord lesion. Spinal cord involvement in sarcoidosis is rare, occurring in 90%). In brachial plexus avulsion or amputation, results are variable but much lower than 60%. MCS in patients with pain in lower limbs (e.g. after central subcortical stroke) show success rate inferior to 50%. The variability of the published results suggests that the success rate depends on the type of lesion underlying NP. Different techniques could improve patient selection by isolating factors predictive of a good response (7,11). Among them, barbiturates and morphine test and the observation that the response to transcranial magnetic coil stimulation of the motor cortex could predict the response to epidural MCS (3,13,16). It is, however, not clear nowadays, whether transcranial magnetic stimulation should be generalized to select the potential good responders. Many functional modifications are observed on fMRI, positron emission tomography (PET) or magnetoencephalography (MEG) in pain syndromes and after MCS. It is unclear however whether they might be directly related to the analgesic efficacy of MCS and whether functional imaging could allow to select potential good-responders. Limitations of the iBM. Although representing the most direct, faithful and precise functional technique for recording neuronal activity in the primary cortical areas, iBM may unfortunately present in NP some limitations that reduce significantly the quality of the targeting method. Indeed, in marked deafferentation, iBM may show wave attenuation, diffused motor response, increased sensitivity to electrical artifacts or lack of reproducibility due to the lesion of the somato-sensory tracts. In a personal series of 18 patients, iBM showed highly accurate to localize the functional target in 50% of the cases; provided an approximative target in 3/18 and provided non reproducible target in 6/18 cases (18). Moreover, even in physiological conditions, the facial area, although largely represented on the pre-central gyrus, is not accurately identified by iBM. Finally, in amputees or in patients with brachial plexus lesions, iBM may be simply unfeasible because the limb is lacking or is degenerated. These limitations may compromise the quality of the targeting and even underestimate the actual analgesic efficacy of MCS. Cortical projection of the lower limb and neuronal plasticity. One limitation of the MCS technique in patients with NP in lower limbs is the cortical projection of the lower limb on the interhemispheric portion of the motor strip. This anatomical disposition increases the distance between the electrode fixed on the convexity and should reduce the efficacy of MCS. On the other hand, implanting the electrode subdurally in the interhemispheric fissure is not feasible on a safe and routine basis. Practically however, the functional target corresponding to the lower limb in iBM (confirmed by fMRI) is projected on the para-sagittal convexity in more than one third of the patients so that this limitation does not affect all patients. In NP, although

1108 Functional Neurosurgery the cortical sulci are not invaded or displaced as they are in brain tumors, the electrode positioning, assisted by iBM, may be functionally inaccurate. Indeed, a certain degree of functional reorganization or functional plasticity may take place as result of a significant deafferentation (10,20). This has not been studied extensively yet. However, some observations of mental movements obtained in amputees for fMRI study have collected interesting data. The neural mechanisms involved in the mental representation of an action and in its execution remain the same and the cortical areas devoted to the missing limb seem to persist for several years after amputation (20). However, some adaptation has occurred. A market reorganization of motor and somato-sensory cortices was shown in upper limb amputees with phantom limb pain in which some fMRIactivated areas were displaced (10).

IMPROVING THE FUNCTIONAL TARGETING The frustrating situations of non-responding patients raise a series of questions in which the accuracy of the electrode positioning take a major place. Other issues related to the patient selection and to the method used to stimulate the cortex need future developments for optimizing the technique’s success rate and reducing the nonresponders rate. Patient selection. The variability of the published results suggests that the success rate depends on the type of lesion underlying NP. Isolating factors predictive of a good response could improve the MCS success rate. Indeed, different techniques were proposed to improve patient selection (7,11). Among them, barbiturates and morphine test and the observation that the response to transcranial magnetic coil stimulation of the motor cortex could predict the response to epidural MCS (3,13,16). It is, however, not clear nowadays, whether transcranial magnetic stimulation should be generalized to select the potential good responders. Furthermore, since many functional modifications observed on fMRI, PET or MEG might not be directly related to the analgesic efficacy of MCS, it is not clear, so far, whether functional imaging could allow to select potential good-responders. Accurate electrode positioning. The variability of the reported success rates of MCS in NP could also be related to an inaccurate electrode positioning method in some patients or in some series. Therefore, it is not impossible that the actual efficacy of MCS might be underestimated. Because appropriate targeting along the CS is a crucial step to obtain pain relief, the accuracy of electrode positioning should be questioned first in nonresponders. The following adjuncts have been proposed in order to optimize the existing targeting method. Awake surgery. Awaking patients during the surgical procedure might significantly improve the quality of iBM by increasing the amplitude of evoked potentials, by improving the reproducibility of electrophysiological data and by reducing the sensitivity of iBM to electrical artifacts described above. This technique represents a valid approach for MCS but requires training and experience for keeping a low complication rate

Motor cortex stimulation in neuropathic pain : Technique and perspectives

1109

(sub-dural hemorrhage, seizures, infection), even for surgeons familiar with the awake technique in brain tumors resection. Moreover, one must keep in mind that awake surgery does not allow to assess the analgesic efficacy of MCS because of the low level of consciousness allowed by the technique. Moreover, contrary to patients operated for brain tumors, chronic NP patients often present a poor level of cooperation, altered by the uncomfortable position, by the chronic pain and by analgesis drugs that reduce their ability to understand and sustain concentration on simple tasks. Definitely, awake surgery might only benefit to the functional targeting method used for electrode positioning. Combining independent functional targeting techniques: PET, fMRI and MEG. Functional PET studies might increase the understanding of the analgesic effect induced by MCS. PET, however, is not useful for improving the functional targeting during the surgical procedure. Functional PET studies have showed abnormal metabolism in the thalamus contra-lateral to the painful segment. One of the first PET studies (using fluorodeoxyglucose as radiotracer) showed a reduced metabolism in the thalamus on the affected side (12). Others studied post-operative PET with 015-labelled water and showed after MCS - compared to non-stimulated status (independently from analgesic effect) a significantly increased regional cerebral blood flow (rCBF) in a restricted set of ipsilateral cortical and sub-cortical regions in which the most significant are the ventral and lateral (VL) thalamus, the orbito-frontal cortex, the anterior cingular gyrus and the upper part of the brainstem,(7,22). Some of the modifications observed might not be directly related to the analgesic efficacy of MCS. However, all rCBF changes occurred far from the somato-sensory areas and no evidence was found on a potential MCS-related activation of the sensory cortex. Moreover, VL and ventral anterior nuclei are the only thalamic nuclei directly connected with the motor and pre-motor cortices. These thalamic regions are not involved in pain integration and cells in the VL thalamus are somatotopically arranged as are their projections to the pre-motor cortex (7). The other regions showing rCBF increase after MCS (medial thalamus, orbito-frontal cortex, anterior cingular gyrus and upper part of the brainstem) are known to be involved in pain processing and control. These areas have strong interconnections and are connected to the medial and anterior thalamus. MCS might be effective on pain by modulating either the intensity of the conscious sensation or at least the distressful reaction to it. fMRI guidance can provide independent and highly accurate targeting information for improving the surgical procedure. Indeed, in a previous work, we have evaluated the accuracy of the BOLD-fMRI-guidance in the operative targeting for MCS (2,19,20). We undertook that study because fMRI guidance was mostly untested in NP. Moreover, it had not been validated in MCS, especially with regards of the potential functional reorganization in cortical areas following chronic NP. Because some technical and methodological issues must be addressed prior to its reliable application, fMRI guidance was combined with iBM in the MCS surgical procedure. iBM-guided MCS were performed under stereotactic image-guidance by using a frameless neuronavigation system and the data obtained by iBM and fMRI were compared intra-operatively. Correspondence between contours of fMRI activation area and iBM in precentral gyrus was found in almost all patients. Moreover, fMRI revealed to be less altered by artefacts

1110 Functional Neurosurgery and to provide data which were more constantly unambiguous than those from iBM. fMRI also offered the great advantage to be performed in amputated patients in which no iBM is feasable. Because fMRI remains a technique under evaluation, the use of fMRIguidance must be kept and validated in combination with iBM to improve the functional targeting of MCS. Since appropriate targeting is crucial to obtain pain relief, this combination might increase the analgesic efficacy of MCS (19). fMRI is however, a time consuming technique requiring training and engineering (statistical parametric mapping, spatial and functional validation) prior to be applied in stereotactic conditions. MR tractography, fMRI and diffusion tensor imaging (DTI) might also be combined for anatomo-functional correlations. It might be a helpful adjunct for localizing the motor activation process (23) and for enhancing the topography and the damage of some thalamo-parietal fibers. Such combination could improve or confirm the targeting data of fMRI and iBM for electrode positioning. Finally, combining different functional methods might lead to reduce the rate of reoperation proposals made to some nonresponders for repositioning the cortical electrode in an attempt to define an alternative target. MEG is also a functional imaging method which might provide tremendous information in NP. The interest of MEG is the temporal resolution (1 second, real time acquisition) which is much higher than that of fMRI (30 min, summation acquisition). Moreover, MEG records directly the magnetic field created by the electrical neuronal activity while fMRI activation signals reflect indirectly transient changes in the rCBF secondary to the neuronal activity (6,23,24,25). We have acquired a MEG in our hospital last year and designed recently a protocol combining MEG and fMRI functional data in the navigation workstation as we did with iBM and fMRI previously. We plan to study whether MEG and fMRI targets are comparable, in the functionally relevant cortex and regarding the possible plasticity. We plan to validate MEG guidance with fMRI guidance for surgery in confirming functional targets from pre-operative rTMS, iBM and analgesic efficacy induced by MCS. Finally, evaluating whether MEG guidance improves MCS targeting, improves MCS success rate and improves the understanding of nonresponders remains to be achieved. Combining independent and complementary functional techniques might increase the accuracy of the functional cortical targeting. For this purpose, the navigation system is a precious tool for integrating intraoperatively different targeting methods such as iBM, fMRI or MEG (19,20).

OPTIMIZING THE CORTICAL STIMULATION Electrode orientation. As mentioned above, the pain relief occurs in some patients when the negative pole of the stimulation electrode is over the premotor rather than the motor area of the pre-central cortex. This observation requires to keep a large portion of the electrode covering both motor and premotor gyri devoted to the somatotopic projection of pain. For that purpose, a single quadripolar electrode should therefore be orientated perpendicular to the CS. When the functional targeting method provides ambiguous data (e.g. for targeting facial areas), we do not recommend to orientate a single electrode vertically along the CS over the motor strip. By experience (19,20), finding the functional target along the CS is crucial to obtain pain relief and should be achieved prior

Motor cortex stimulation in neuropathic pain : Technique and perspectives

1111

to fixing the electrode to the dura. Its orientation perpendicular to the CS allows to stimulate both motor and premotor gyri. Using two electrodes (positioned side by side and orientated perpendicular to the CS) might help to better cover vertically the motor and premotor gyri along the CS. Sub-dural electrode. Opening the dura might present different advantages but represents a more invasive approach. First, sub-dural iBM recordings provide a more precise functional targeting by increasing the iSEP wave amplitude. Secondly, subdural electrode positioning allows to reduce the intensity of cortical stimulation. Thirdly, direct observation of the cortical gyri allows to better control the location of the CS by direct correlation with the navigation images. However, sub-dural MCS remains debated and not recommendable for many reasons: it does not increase the technique’s success rate, it increases significantly the risk of seizures induced by stimulation and might generate scar tissue, cortical lesioning with secondary gliosis, seizures and infectious empyema. Large electrode design. Using double or multiple electrodes (separated or combined in a newly-designed enlarge silicone plate), is a valid alternative that might increase the cortex surface to stimulate and the chances to obtain analgesic effect. However, the use of a large electrode might reduce the homogeneity of the distance between electrode and the cortex because the tight contact to the dura might not be garanteed in the center of the electrode.

SURGICAL COMPLICATIONS AND MANAGEMENT Infection. As classically observed in all surgical disciplines, the infection risk of MCS is increased by the presence of implanted materials. Infection can occur as a primary process, directly related with the electrode implantation and rapidly presents as epidural or sub-dural (if the dura has been opened – see above) empyema. Infection can also start at the cutaneous exit of the electrode. Finally, infection of the electrode may occur secondarily to incomplete healing of the skin at the level of the scar on the vertex. Practically however, the infection rate is not high. On about 50 MCS procedures and patients performed so far, we experienced infection in 3 cases only (Primary epidural empyema 15 days after surgery in 1, sub-dural empyema 10 days after surgery in 1 and epidural empyema with cortical abscess secondary to incomplete healing of the scar 6 weeks after surgery in 1). Although an excellent analgesic response in all of them, these 3 cases required the surgical removal of the entire implanted electrodes, followed by 4 weeks in intravenous antibiotics to have their infection cured. For avoiding primary infection of the electrodes, aseptic measures must be carefully applied all along the procedure, such as during the shunt implantation procedure. Double gloving, avoiding implants manipulations as well as using systematically 24-hourprophylactic intravenous antibiotics should be standardized for MCS implantation. With the experience, we now insert systematically a drain in the epidural or subcutaneous space in order to reduce the risk of hematoma and subsequent inflammation or local infection. If epidural or sub-dural infection occurs, the conservative option with

1112 Functional Neurosurgery intravenous antibiotics can be attempted. Unfortunately, however, the surgical removal of the entire implanted system appears the unique way to cure infection. The local cutaneous infection at the exit of the temporary cables behind the ear is benign and rather unfrequent, although the metallic cables are staying transcutaneously for weeks. Daily application of betadine at the local site is usually sufficient to control the local inflammation so that the infection does not progress to the skull and to the epidural electrode. Secondary infection of the scar due to incomplete healing of the wound at the convexity should not be underestimated. It represents a source of major electrode infection that can lead to removing the entire material implanted. Indeed, an incomplete healing of the wound can contaminate the subcutaneous space where the electrode wires can be involved. We experience one case in which the secondary epidural infection of the electrodes complicated by a cortical abscess, The case we have with an epidural empyema secondary to a healing insufficiency developed a cortical abscess just below the electrode. This abscess was visible on CT and MRI and lasted for 6 months before disappearing. During the 6-week-infection phase, this 30-year-old female made repeated partial motor seizures (motor strip involved), increased transiently her hemiparesis and complained of increased pain sensation although MCS provided analgesia before infection. This case convinced us to modify our policy of skin incision. We took a special care to draw a large skin incision on the convexity in order to avoid the wound to be just above any bone fixation or any wire or material, the skin incision being far away from the edge of the craniotomy. Also, we recommend the senior surgeon closes himself the skin with separated sutures and takes special care to the excellent congruence of skin edges. Induced seizures / unvoluntary movements. Stimulating the patient with bipolar monophasic square wave pulses at a frequency of 40 to 120 Hz, with a duration of 100 to 400 microseconds and an amplitude of 1 to 5 volts and with the negative pole situated over the motor cortex has almost no risk of inducing unvoluntary movements. Stimulating above 8 to 10 volts, however, increases the risk of inducing a motor response or even a seizure. Practically, this occurs very rarely. However, a seizure, even short, can induce neuronal suffering, generalize in a grand mal crisis and even create an epileptic focus. This is the reason why we recommend to avoid any stimulation during one week in case of seizure during the test-period. Also, it is useless to stimulate above 6 volts. In our experience, no patient who did not respond between 1 and 5 volts, responded favourably above 6 to 7 volts. The clinican must keep in mind that the analgesic effect has the highest chance to occur at one third of the motor threshold. The analgesic effect from MCS is generally obtained between 2 and 5 volts in patients in which the motor threshold (the threshold above which stimulation creates a movement) is observed between 7 to 13 volts. If ever a seizure occurred intra-operatively during the iBM, we recommend to flush the cortex with cold serum. Increased pain sensation. During the test-period, we have observed that patients can easily complain that the pain sensation enhance and is associated with an increased sensation of burning or tingling in the painful limb. When analyzing the bipolar

Motor cortex stimulation in neuropathic pain : Technique and perspectives

1113

combinations tested, this observation was constantly correlated with a cathodic stimulation placed above the parietal cortex. Also, it happened in a couple of good or excellent responders in which the stimulator was secondarily implanted, that the analgesic effect observed two months after the implantation seemed to decrease as compared to that obtained initially. In a majority of them, we noticed that this apparent loss of efficacy was due to the fact that MCS stimulation has been programmed in a continuous mode instead of a cycling mode (e.g. 4 hours on followed by 4 hours off). We believe that the cortical stimulation performed in a continuous mode creates electrical fields that recruit cortical areas more extensively around the electrode and that are able to stimulate the parietal cortex or to acts as if the parietal sensory cortex was activated. Changing the continuous mode to a cycling one make the burning sensations usually disappear within 2 hours and make the analgesic effect, previously observed, recur within a few hours. Electrode and cable damage. Special attention and skills are required for the surgical implantation and connection of the different electrodes and cables. As soon as the fixation of the electrode to the dura, the surgeon must avoid to kink the cables with the bone flap fixation or to perforate the tiny metallic contacts and wires into the electrode. Similarly, during the second surgery, the re-opening of the supra-mastoid skin at the connection level, to withdraw the temporary cable left in place and to connect the extension cable to the extremity of the MCS electrode must be performed with great care to not hurt and damage the material and to make the connections watertight by using the cap that is provided to cover the connection. Any kinking, perforation, or suture defect can lead to loss of power and to MCS inefficacy. Indeed, in any patient not responding to MCS after the neurostimulator was implanted, a low of power or an electrical obstacle must be advocated. In all cases, the impedance (electrical resistance) of each electrode contacts and cable must be tested by proper programmation of the neurostimulator. In normal conditions, the impedance ranges around 600-700 Ohms. If any disconnection or loss of power occurred the impedance is recorded as higher or lower than this range. Then, the first step to allow verification is to perform a standard X-ray of the complete implanted system. Cables or stimulator painful. The surgeon should not forget that the normal sensory perception may be disturbed in NP patients, even in places located far from the painful limb or segment. This may cause minor – but chronic and sometimes disabling – complaints centered on the places where electrodes, cables or stimulators and implanted. About 20 % of the patients, report painful sensations either at the scalp – around the bone flap - or at the supra-mastoid region – where the connection is located - or around the neurostimulator. Visual inspection, as well as CT, X-rays or MRI usually do not show anything wrong. Two of our patients reported a painful sensation along the subcutaneous trajectory of the extension cable in the neck as if it was stretched like a rope in rotation movements of the head. Indeed, a fibrous reaction can occur around the extension cable so that we recommend not to tunnelize it too superficially in the neck in order the platysma muscle cover it completely. It may happen that some patients complain of the site the stimulator has been implanted. Indeed, the stimulator is implanted

1114 Functional Neurosurgery subcutaneously at the sub-clavicular or at the para-ombilical level. This issue should be discussed with the patient prior to the surgical procedure. The para-ombilical place can be very convenient in fat persons but sometimes painful in skinny patients because of frictions with the trousers, belt or other clothes. Some young ladies may not accept the stimulator to be placed at the sub-clavicular level, especially for esthetical reasons. We have in some instances placed the stimulator 5 cm lower and 10 cm more laterally with a vertical incision very lateral above the breast, just on the pectoral muscle with great satisfaction and no complaint so far.

CONCLUSION Since the first report in 1991, the surgical MCS procedure has known successive adaptations as attempts to better understand and refine the clinical selection, to improve the accuracy of the technique and to increase the technique’s success rate. Although a definitive protocol of the surgical technique has not been established yet, a certain consensus on some clinical issues conditioning MCS analgesic efficacy has been reached: The patient selection criteria, the electrode positioning and therefore the quality of the functional targeting method related to the surgical technique. The functional neurosurgeon ready to develop MCS in the panel of neuromodulation procedures to treat NP must remember in the diversity and the heterogeneity of the clinical NP syndromes as well as the different sources of imprecision of the MCS technique. The neurosurgeon must also be ready to spend a lot of his time to give the NP patients sufficient technique information and compassionate attendance and follow-up.

REFERENCES 1. Carroll D, Joint C, Maartens N, Shlugman D, Stein J, Aziz TZ (2000) Motor cortex stimulation for chronic neuropathic pain: a preliminary study of 10 cases. Pain 84:431437 2. Casey KL (2000) Concepts of pain mechanisms: the contribution of functional imaging of the human brain. Prog. Brain Res. 129: 277-87 3. Di Lazzaro V, Oliviero A, Profice P, Insola A, Mazzone P, Tonali P, Rothwell JC (1999) Direct demonstration of interhemispheric inhibition of the human motor cortex produced by transcranial magnetic stimulation. Exp. Brain Res. 124:520-524 4. Duffau H (2001) Acute functional reorganisation of the human motor cortex during resection of central lesions: a study using intraoperative brain mapping. J. Neurol. Neurosurg. Psychiatry 70:506-513 5. Ebel H, Rust D, Tronnier V, Boker D, Kunze S (1996) Chronic precentral stimulation in trigeminal neuropathic pain. Acta Neurochir (Wien) 138:1300-1306 6. Ferretti A, Del Gratta C, Babiloni C, Caulo M, Arienzo D, Tartaro A, Rossini PM, Romani GL (2004) Functional topography of the secondary somatosensory cortex for nonpainful and painful stimulation of median and tibial nerve: an fMRI study. Neuroimage 23:1217-1225 7. Garcia-Larrea L, Peyron R, Mertens P, Grégoire MC, Lavenne F, Le Bars D, Convers P, Mauguière F, Sindou M, Laurent B (1999) Electrical stimulation of motor cortex for pain control: a combined PET-scan and electropysiological study. Pain 83;259-273 8. Helmchen C, Lindig M, Petersen D, Tronnier V (2002) Disappearance of central

Motor cortex stimulation in neuropathic pain : Technique and perspectives

9. 10. 11. 12. 13. 14. 15. 16. 17.

18.

19.

20. 21. 22.

23.

1115

thalamic pain syndrome after contralateral parietal lobe lesion: Implications for therapeutic brain stimulation. Pain 98:325-330 Herregodts P, Stadnik T, De Ridder F, D'Haens J (1995) Cortical stimulation for central neuropathic pain: 3-D surface MRI for easy determination of the motor cortex. Acta Neurochir Suppl (Wien) 64:132-135 Karl A, Birbaumer N, Lutzenberger W, Cohen LG, Flor H (2001) Reorganization of motor and somatosensory cortex in upper extremity amputees with phantom limb pain. J. Neurosci. 21: 3609-3618 Katayama Y, Fukaya C, Yamamoto T (1998) Poststroke pain control by chronic motor cortex stimulation: neurological characteristics predicting a favorable response. J. Neurosurg. 89:585-591 Laterre EC, De Volder AG, Goffinet AM (1988) Brain glucose metabolism in thalamic syndrome. J. Neurol. Neurosurg. Psychiatry 51:427-428 Lee L, Siebner HR, Rowe JB, Rizzo V, Rothwell JC, Frackowiak RSJ, Friston KJ (2003) Acute remapping within the motor system induced by low-frequency repetitive transcranial magnetic stimulation. J. Neurosci. 23:5308-5318 McCarthy G, Alisson T, Spencer DD (1993) Localization of the face area of human sensorimotor cortex by intracranial recording of somatosensory evoked potentials. J. Neurosurg. 79:874-884 Meyerson BA, Lindblom U, Linderoth B, Lind G, Herregodts P (1993) Motor cortex stimulation as treatment of trigeminal neuropathic pain. Acta Neurochir Suppl (Wien) 58:150-153 Migita K, Uozumi T, Arita K, Monden S, Lindblom U, Linderoth B (1995) Transcranial magnetic coil stimulation of motor cortex in patients with central pain. Neurosurgery 36:1037-1040 Nguyen JP, Lefaucheur JP, Decq P, Uchiyama T, Carpentier A, Fontaine D, Brugieres P, Pollin B, Feve A, Rostaing S, Cesaro P, Keravel Y (1999) Chronic motor cortex stimulation in the treatment of central and neuropathic pain. Correlations between clinical, electrophysiological and anatomical data. Pain 82:245-251 Pirotte B, Voordecker P, Neugroschl C, Baleriaux D, Wikler D, Metens T, Denolin V, Joffroy A, Massager N, Brotchi J, Levivier M (2005) Combination of Functional MRGuided Neuronavigation and Intraoperative Cortical Brain Mapping Improves Targeting of Motor Cortex Stimulation in Neuropathic Pain. Neurosurgery 56 (2 Suppl):344-359 Pirotte B, Neugroschl C, Metens T, Wikler D, Denolin V, Voordecker P, Joffroy A, Massager N, Brotchi J, Levivier M, Baleriaux D (2005) Comparison of Functional MRI-Guidance to Electrical Cortical Mapping for Targeting Selective Motor Cortex Areas in Neuropathic Pain: A Study Based on Intraoperative Stereotactic Navigation. AJNR Am. J. Neuroradiol. 26:2256-2266. Pirotte B, Voordecker P, Brotchi J, Levivier M. Anatomical and physiological basis, clinical and surgical considerations, mechanisms underlying efficacy and future prospects of cortical stimulation for pain (2007). Acta Neurochir (Wien) 97: 1-9 Roux FE, Ibarrola D, Tremoulet M, Lazorthes Y, Henry P, Sol JC, Berry I (2001) Methodological and technical issues for integrating functional magnetic resonance imaging data in a neuronavigational system. Neurosurgery 49:1145-1156 Saitoh Y, Osaki Y, Nishimura H, Hirano S, Kato A, Hashikawa K, Hatazawa J, Yoshimine T (2004) Increased regional cerebral blood flow in the contrealateral thalamus after successful motor cortex stimulation in a patient with poststroke pain. J. Neurosurg. 100: 935-939 Seghier ML, Lazeyras F, Vuilleumier P, Schnider A, Carota A (2005) Functional magnetic resonance imaging and diffusion tensor imaging in a case of central poststroke pain. J. Pain 6: 208-212

1116 Functional Neurosurgery 24. Torquati K, Pizzella V, Babiloni C, Del Gratta C, Della Penna S, Ferretti A, Franciotti R, Rossini PM, Romani GL (2005) Nociceptive and non-nociceptive sub-regions in the human secondary somatosensory cortex: an MEG study using fMRI constraints. Neuroimage 26:48-56 25. Tran TD, Hoshiyama M, Inui K, Kakigi R (2003) Electrical-induced pain diminishes somatosensory evoked magnetic cortical fields. Clin. Neurophysiol. 114:1704-1714 26. Tsubokawa T, Katayama Y, Yamamoto T, Hirayama T, Koyama S (1993) Chronic motor cortex stimulation in patients with thalamic pain. J. Neurosurg. 78:393-401 27. Wood CC, Spencer DD, Alisson T, McCarthy G, Williamson PD, Goff WR (1988) Localization of human sensorimotor cortex during surgery by cortical surface recording of somatosensory evoked potentials. J. Neurosurg. 68:99-111

1117

Neurosurgical management of Trigeminal Neuralgia MARC SINDOU, MD, D Sc. Department of Neurosurgery, Hopital Pierre Wertheimer, University Claude-Bernard of Lyon, 59 Boulevard Pinel, 69003 Lyon , France Key words: Cranial nerves, trigeminal neuralgia, Gasserian ganglion, rhizotomy, radiosurgery, micro-vascular decompression, Gamma knife, carbamazepine

Introduction The surgical treatment of primary [= idiopathic = essential = classical] Trigeminal Neuralgia (TN) was one of the first successful treatments introduced in the history of neurosurgery. It was early in the nineties that gasserian (9) and retrogasserian (5, 2) trigeminal neurotomy appeared in the therapeuctic armamentarium, long before the use of phenytoin in 1942 and carbamazepine in 1963. Percutaneous approaches to the trigeminal system was popularized by Hartel, who in 1914 detailed a percutaneous technique for needle insertion using external landmarks (8). Percutaneous electrocoagulation of the ganglion was described by Kirschner in 1932 (11). In 1965 Sweet introduced a technique ,which included intermittent anesthesia electrophysiological localization and controlled thermolesion using radiofrequency (18). In 1981 Hakanson discovered that percutaneous glycerol rhizotomy was an effective treatment for TN (7) . Percutaneous balloon compression of the trigeminal ganglion was developed by Mullan and Lichtor in 1983 (13). Radiosurgery was originally developed by Lars Leksell in 1951 (12). With subsequent refinement in the last two decades, Gamma-knife radiosurgery has become a current way of treating TN. Besides those open and percutaneous or radiosurgical lesioning techniques, the (conservative) micro-vascular decompression (MVD) procedure was developed step by step since the first observation in 1934 by Dandy of the occurrence of trigeminal root compression by a neighbouring elongated artery, at the time of performing juxtapontine selective rhizotomies (3). The first decompression of the root from its offending vessel was performed in 1959 by Gardner (6) ; but the method was really promoted in 1967 by Jannetta, who codified the operation using the microsurgical techniques (10).

Diagnosis of Trigeminal Neuralgia Diagnosis of typical primary TN is a clinical one. The criterias in the presentation are : - location on one side of the face - no extension outside the trigeminal territory - paroxysmal pain of the « electric shock » type and no pain between the attacks (i.e.

1118 Functional Neurosurgery refractory periods), at least at the beginning of the disease - pain paroxysms that may occur spontaneously but more are triggered by stimuli - no sensory deficit, no decrease in corneal reflex and no symptoms in other cranial nerve territoires - effectiveness of anticonvulsants, at least initially. Over time the pain becomes more frequent, pain free intervals shorten and an aching/burning background pain appears, sometimes with vasomotor phenomena, giving the neuralgia an atypical presentation. TN can be diagnosed as "primary" only after all specific causes have been eliminated by appropriate investigations, especially standard MRI. A neurovascular compression (NVC) can be evidenced by appropriate MRI sequences (14, 15). The following three are of most usefulness. 1) 3D-T2 – High resolution sequence gives very fine images of neural and vascular structures inside the cerebello-pontine cisterns. But it does not differentiate vessels from nerves. 2) 3D TOF (Time of flight) – Angio sequence visualizes well the vessels (in hypersignal), especially those with fast circulation, i.e., preferentially the arteries. 3) 3D-T1 with Gadolinium sequence provides good vizualisation of the injected vessels, veins as well as arteries. All three sequences have to be performed in association.

Indications for Surgery Indications are summarized in figure 1.

Conclusions Surgery should be considered only after anticonvulsant medications have failed or if medical treatment is not well-tolerated, including asthenia and drowsiness. MVD should be considered as the first surgical option whent patients are in good health, as MVD treats the cause and is a conservative method ( 1,4,16,17). MVD is able to cure (i.e., no pain, no medication) primary TN due to vascular compression in 75% of the patients, 90% when the compression is marked on preoperative MRI. This can be achieved without side-effects in almost all the cases. Recourse to the new fine MR images may demonstrate, although not always reliably, the compressive vessels(s) and root distortions. A keyhole retro-mastoid and infratentorial supracerebellar approach obviates the need for BAEP monitoring for preserving hearing as soon as the learning curve has become "good". Percutaneous lesioning-operations or radiosurgery are preferable in patients with adverse co-morbidity. The choice of the technique depends on the local facilities and on the training of the practicing neursurgeon.

Neurosurgical management of Trigeminal Neuralgia

1119

Fig. 1 Sindou : Neurosurgical Management of Trigeminal Neuralgia

REFERENCES 1. BARKER FG, JANNETTA PJ, BISSONNETTE DJ, LARKINS MV, JHO HD (1996) The long-term outcome of microvascular decompression for trigeminal neuralgia. New engl J Med 334 : 17 : 1077-1083 2. DANDY WE (1925) Section of the sensory root of the trigeminal nerve at the pons. Bull Johns Hopkins Hosp 36:105-106 3. DANDY WE (1934) Concerning the cause of trigeminal neuralgia. Am J Surg 24 : 447-455 4. ELIAS WJ, BURCHIEL KJ (2004) Trigeminal Neuralgia – Microvascular decompression. In : FISHER WS and BURCHIEL KJ (eds) “Pain management for the neurosurgeon : Part 2. Seminars in Neurosurgery”, vol 15, numbers 2/3. Thieme, New-York, pp 143-150. 5. FRAZIER C (1925) Subtotal resection of sensory root for relief of trigeminal neuralgia. AMA Arch Neurol Psychiatry 13:378-384 6. GARDNER WJ, MIKLOS MV (1959) Response of trigeminal neuralgia to decompression of sensory root. Discussion of cause of trigeminal neuralgia. JAMA 170 : 1773-1776

1120 Functional Neurosurgery 7. HAKANSON S (1981) Trigeminal neuralgia treated by the injection of glycerol into the trigeminal cistern. Neurosurgery 9:638-646 8. HARTEL F (1914) Ueber die Intracranielle injections behandlung der Trigeminusneuralgie. Med Klin 10:582-584 9. HORSLEY V, TAYLOR J, COLMAN W (1981) Remarks on the various surgical procedures devised for the relief or cure of trigeminal neuralgia (tic douloureux). Br Med J 2:1249-1252 10. JANNETTA PJ (1967) Arterial compression of the trigeminal nerve at the pons in patients with trigeminal neuralgia. J Neurosurg 26 : 159-162 11. KIRSCHNER M (1931) Zur Elektrochirurgie. Arch Klin Chir 167:761-768 12. LEKSELL L (1971) Stereotactic radiosurgery in trigeminal neuralgia. Acta Chir Scand 37:311-314 13. MULLAN S, LICHTOR T (1983) Percutaneous microcompression of the trigeminal ganglion for trigeminal neuralgia. J Neurosurg 59:1007-1012 14. SINDOU M, HOWEIDY T, ACEVEDO G (2002) Anatomical Observations During Microvascular Decompression for Idiopathic Trigeminal Neuralgia (with Correlations Between Topography of Pain and Site of the Neurovascular Conflict). Prospective study in a Series of 579 Patients. Acta Neurochir 144 : 1-13 15. SINDOU M, KERAVEL Y et coll. Neurochirurgie Fonctionnelle dans les syndromes d’hyperactivité des nerfs crâniens. Rapport devant le 59ème Congrès de la Société de Neurochirurgie de Langue Française, Alger, 15-18 Mai 2009. Neurochirurgie, 2009,vol 55, 75-292 16. SINDOU M, LESTON J, DECULLIERE, CHAPUIS F (2007) Micro-vascular decompression for primary Trigeminal Neuralgia: Long-term effectiveness and prognostic factors in a series of 362 consecutive patients with clearcut neurovascular conflicts who underwent pure decompression. J. Neurosurg 107:1144-1153 17. SINDOU M, LESTON J, DECULLIERE, CHAPUIS F (2007) Microvascular decompression for trigeminal neuralgia: the importance of a non-compressive techniqueKaplan-Meier analysis in a consecutive series of 330 patients. Neurosurgery 63:ONS 341ONS351 18. SWEET WH (1976) Controlled thermocoagulation of trigeminal ganglion and rootlets for differential destruction of pain fibers : facial pain other that trigeminal neuralgia. Clin Neurosurg 23:96-102

1121

Microvascular decompression: Analysis of un-successful cases TETSUO KANNO, KOSTADIN KARAGIOZOV Department of Neurosurgery, Fujita Health University Key words: microvascular decompression (MVD), trigeminal neuralgia, treatment, surgical approach, results

I. Introduction Microvascular decompression(MVD) is a well known surgical procedure with one of the best long term results in the therapy of trigeminal neuralgia and hemifacial spasm. It is a highly accepted and effective method in cases where vascular compression of a nerve is implicated in the pathogenesis of disease. As in any surgical method applied, good outcome depends on proper diagnosis and patient selection. However, the surgical result by any "super-neurosurgeons" in the world have not obtained 100% cure by MVD. (Fig.1)

Fig. 1

Therefore, a new modality such as radiosurgery is now increasing its share, particularly for trigeminal neuralgia. The senior author (TK), analyzed 955 cases of MVD: trigeminal neuralgia (326) and hemifacial spasm (629) he had surgically treated between 1980-2006. (Fig.2) MVD was performed using Janetta's technique and endoscopic assistance was used in some cases. Intra-operative monitoring for facial nerve was done in some cases of HFS. The mean follow up was 10.5 years.

1122 Functional Neurosurgery In this chapter, we focus on the unsuccessful cases and analyze the causes of the failure.

Fig. 2

II. Surgery for Trigeminal Neuralgia 1) Case selection is made based on the clinical symptoms and MRI(SPGR). (Fig.3) After staring the SPGR application, all the cases showed the definite compressing vessels during surgery.

Fig. 3

The surgical position, skin incision and craniectomy are shown on Fig.4,5. The shape of craniectomy is "strawberry shape" which makes better surgical field for

Microvascular decompression: Analysis of un-successful cases

1123

Fig. 4

Fig. 5

lower cranial nerves. Authors do not like the so-called "key-hole" surgery, and we usually expose the sigmoid sinus. (Fig.6) Retraction Authors usually use a retractor at the initial stage of surgery until CSF is removed. After that we rarely use retractor. (Fig.7)

1124 Functional Neurosurgery

Fig. 6

Fig. 7

Microvascular decompression: Analysis of un-successful cases

1125

2) Approach to trigeminal nerve There are two approaches to the trigeminal nerve. The first is from the lower cranial nerves upwards. This approach is rather easy for orientation of the nerves, because the lower cranial nerves locate rather shallow in the surgical field. However, we must be careful not to injure the Acoustic nerve. The second approach is over the cerebellum and reaches directly the trigeminal nerve. In this approach, we must be careful not to injure the superior petrous vein(s). (Fig. 8)

Fig. 8

3) Avoid injury to the superior petrous veins. Avoiding strong retraction of the veins is the most important factor. But, if the surgeon is worried about venous injury, he may place a small surgicel mesh around the venous entrance point to the sinus and reinforce it with glue. (Fig.9) Another point to avoid bleeding from the veins is not to open the arachnoidal membrane widely. It prevents the spreading of bleeding to the prepontine cistern. If the bleeding enters into the prepontine cistern, it may induce acute brain swelling within 5 minutes. (Fig.10) How to avoid the injury to the veins, and how to prevent the spreading of the clot are the most important techniques of this surgery. For the beginner, this accident can be the most frequent cause of the mortality.

1126 Functional Neurosurgery

Fig. 9

Fig. 10

Microvascular decompression: Analysis of un-successful cases

1127

5) Points to consider to obtain complete cure. ① REZ Area of REZ is different between trigeminal nerve and facial nerve. REZ of trigeminal nerve is very wide, so the surgeon must do complete decompression all along the nerve. On the other hand, REZ of facial nerve is just a pinpoint. (Fig. 11)

Fig. 11

Fig. 12

1128 Functional Neurosurgery ② Complete decompression is the most important factor to obtain cure. However, in case of trigeminal neuralgia, the surgeon also must take care for the shape of the trigeminal nerve after decompression. The nerve should be left straight. If not, sometimes complete pain control cannot be obtained. (Fig.12) ③ Granuloma One of causes of recurrence is the compression by a postoperative granuloma. It is not frequent, but sometimes it is really the cause of recurrence. (Fig.13)

Fig. 13

Total removal of granuloma and transposition of vessels is the technique of choice in reoperation. ④ The offending vessel is sometimes running between the motor and sensory branches of trigeminal nerve. Sandwich style of the decompression around the penetrating artery makes good relief of pain. (Fig.14) 6) Non-surgical methods of treatment ① General results of microvascular decompression revealed ① complete cure : 74-94% and ② Arecurrence 16-45%. (Fig.15)

Microvascular decompression: Analysis of un-successful cases

Fig. 14

Fig. 15

1129

1130 Functional Neurosurgery ② The complications are shown on Fig.16. The mortality is between 0.1%~1.0%. (Fig.16)

Fig. 16

③ The protocol of medical treatment at our institute is as shown in Fig.17 and 18. If the pain is still uncontrollable, Tegretol will be increased. (Fig.19)

Fig. 17

Microvascular decompression: Analysis of un-successful cases

1131

Fig. 18

④γ-knife treatment There are two targets on trigeminal nerve, one is REZ targeting and other is Retro gasserian targeting. (Fig.19)

Fig. 19

The result of these targeting is shown in Fig.20. 7) Our strategy of treatment for trigeminal neuralgia is shown on Fig.21.

1132 Functional Neurosurgery

Fig. 20

Fig. 21

III. Surgery for hemifacial spasm 1) Case selection is made according to clinical symptoms and MRI (SPGR) (Fig.22, 23) Surgical position, skin incision and craniectony are shown in Fig. 5 and 6. 2) There are 2 ways to make a decompression. One is the interposition and the other is transposition. Nowadays, transposition is more done particularly in Japan.

Microvascular decompression: Analysis of un-successful cases

Fig. 22

1133

Fig. 23

However, transposition is not always possible, because sometimes a small perforating artery reaching pons may disturbs the transposition. (Fig.24)

Fig. 24

3) There are 2 ways to make an interposition. One is direct decompression just on REZ and the other is indirect decompression, on proximal and distal sites of REZ of facial nerve. Direct decompression on REZ sometimes causes recurrence together with the artery and inserted prosthesis. (Fig.25)

1134 Functional Neurosurgery

Fig. 25

4) Facial spasm develops only with pinpoint compression of the artery on REZ. Vague compression does not cause spasm. (Fig.26)

Fig. 26

Microvascular decompression: Analysis of un-successful cases

1135

5) Reasons for unsuccessful surgery. ① Inserted prosthesis to a non-correct site. This mistake is usually done by beginners. (Fig.27)

Fig. 27

Fig. 28

1136 Functional Neurosurgery ② Misinterpretation of which are true offending vessels. This often occurs in a case which there is vertebral artery near REZ. The beginner thinks that it is the offending vessel and makes transposition of it. However, the true offending vessel is running under the vertebral artery and it is the offender that must be displaced. (Fig.28) ③ Double vertebral arteries. In some cases, bilateral vertebral arteries are observed in the surgical field. Two big vertebral arteries must be transpositioned and a small artery behind them must be treated too. (Fig.29)

Fig. 29

④ In case of vertebral artery compression, too much inserted prosthesis may cause facial nerve palsy after surgery. Its early removal improves the palsy quickly. ⑤ Sometimes, the internal auditory artery which runs between the facial nerve and acoustic nerves looks the offending vessel to the surgeon. (although mostly it is not) The surgeon wants to raise up the artery from the inner side of the facial nerve. The inner side of the facial nerve (on the side facing the acoustic nerve) is weak to be touched. It sometimes causes facial nerve palsy after surgery. (Fig.31) ⑥ Retraction pulling along the acoustic nerve often causes hearing disturbance after surgery. The retraction must be applied at a right angle (perpendicular) to the acoustic nerve. (Fig.32)

Microvascular decompression: Analysis of un-successful cases

Fig. 30

Fig. 31

1137

1138 Functional Neurosurgery

Fig. 32

V. Conclusion Based on our experience with both micro- and endoscopic techniques, MVD can be a good alternative strategy with low complication rates to ablative procedures. It is a safe and effective method of treatment. Proper surgical technique helps in reduction of un-successful cases and it should be proposed as first choice of surgery to all patients affected by trigeminal neuralgia and hemifacial spasm.

1139

Percutaneous Techniques for Treatment of Trigeminal Neuralgia BENAISSA ABDENNEBI Professor Department of Neurosurgery Salim Zemirli teaching Hospital Algiers - Algeria Key words: trigeminal neuralgia, radiofrequency thermocoagulation, balloon compression, glycerol rhyzotomy, radiosurgery

INTRODUCTION Idiopathic trigeminal neuralgia (ITN) also called “tic douloureux” and well described by patients as “forked lightning” is considered as one of the most painful and disabling diseases. According to the International Headache Society, 2004, ITN consists of paroxysmal attacks of pain lasting from a fraction of one second to two minutes, affecting one or more divisions of trigeminal nerve and presenting as: a- intense, sharp, superficial or stabbing b- precipitated from trigger area or by trigger factors c- attacks are stereotyped in the individual patient d- there is no clinically evident neurologic deficit e- not attributable to another disorder. Carbamazepine was first marketed as a drug to treat ITN in 1962 and to date it remains the medical treatment of choice. When to decide the timing of surgery? We should consider surgery when pain is refractory to medical treatment after a long time of good response, or in case of disabling adverse effects. Only 5% to 8% of patients will require neurosurgical treatment. A careful history taking can avoid misdiagnosis including postherpetic neuralgia, common cluster headaches, glossopharyngeal neuralgia and temporo mandibular joint pain. In order to decide the most appropriate surgery, we should take into account the available equipments, the neurosurgeon’s experience and the patient’s preference. We should weigh the advantages and risks of each procedure. Those are “open skull” surgery consisting in microvascular decompression of the trigeminal nerve, radiosurgery wich does not need skin incision and percutaneous approaches (PA) requiring cannulation of the foramen ovale. Since 1985 at Salim Zemirli Hospital in Algiers, 702 patients were operated on using these PA which will be described in detail hereunder.

HISTORICAL DATA AND EVOLUTION OF IDEAS The PA used worldwide nowadays was first reported in 1914 by Hartel (4). During the first half of the last century, alcohol was the most injected substance through this route. In, the same period, in 1931, Kirshner (6) reported and popularized the electrocoagulation. Because of the morbidity, neurosurgeons stopped this technique for

1140 Functional Neurosurgery the benefit of radiofrequency thermocoagulation well focused by Sweet and Wepsic (16) in 1974. Later, balloon compression of the Gasser ganglion well described by Mullan (11) in 1983 originated from operative data of Shelden, in 1955, which have shown that compression with a blunt dissector of this anatomical structure was preferable to its decompression ((13). The beginning of focused radiation was in the 1950’s and widely used since the mid 1990s (7). In 1981, Hakanson (3), Leksell’s collaborator recorded that glycerol used as a vehicle of radioactive tantalum, had also a chemical toxicity. In these techniques performed via this anterior route, the target remains the Gasser ganglion (GG) or more exactly axons in the triangular pars, avoiding the cell bodies located in the GG (14). The ideal goal of the different techniques is to obtain a pain free state without major complications.

CLINICAL ANATOMY The Meckel’s cave is a dural sleeve accompanying the trigeminal nerve, especially the triangular pars and ends over the GG which are medially in close relation with major vessels, the posterior part of the cavernous sinus and the internal carotid artery. The GG has a semi lunar shape, measuring around 15 mm (range: 11-20mm) mediolaterally (5): contains cell bodies of incoming sensory nerve fibres of the first neuron of the trigeminal pathway: from the sensory peripheral receptor in the face to the trigeminal nucleus in the brainstem. The triangular pars represents the anterior portion of the nerve immediately adjoining the GG. To increase the safety of surgery, a good knowledge of three anatomical structures is basic: cheek, pterygomaxillary fossa (PMF) and the foramen oval (FO). 1- Cheek (Fig. 1): Its relative simplistic anatomy contrasts with the complex structure on both sides of the foramen oval. Lateral to the angle lip, buccinator or Bugler’s muscle has a horizontal arrangement; risorius and zygomatic muscles compose the wall of the cheek. More posterior, vertically outside the mandible, the masseter muscle has a quadrilateral shape. 2- PMF (Fig. 2): is well visualized when the zygomatic arch and the coronoid process of the mandible are removed. Located deeper and posterior behind the face and under the skull base, it encloses lateral and medial pterygoid muscles, respectively conical and quadrilateral in shape in close vascular relation with: - internal maxillary artery which is the terminal ending of the external carotid artery, and its branches : deep auricular artery, anterior tympanic artery, accessory meningeal artery, middle meningeal artery, mental artery, inferior alveolar artery - Pterygoid venous plexus connected to the cavernous sinus via emissary veins which cross the foramen oval. The other contents are: a/ the mandibular division of the trigeminal nerve, b/ the otic ganglion with its parasympathic fibers dedicated to the parotid gland and c/ the chorda tympani which contains parasympathic and sensorial fibres arising from the facial nerve.

Percutaneous Techniques for Treatment of Trigeminal Neuralgia

Fig. 1 Illustration showing muscles (M) of the cheek: 1: Zygomatic M., 2: Risorius M., 3: Buccinator M., 4: Masseter M., 5: Depressor anguli oris M.

1141

Fig. 2 Illustration showing lateral (1) and medial (2) pterygoid muscles in the pterygo maxillary fossa after removing the zygomatic arch and the coronoid process of the mandible.

Fig. 3 Three-dimensional volume Computerized Tomography depicting the pterygo maxillary fossa, especially the internal maxillary artery (white arrow), the foramen oval (yellow arrow) after resection of the zygomatic arch and the coronoid process of the mandible (black arrows).

3- Foramen oval (Fig. 3): is located in the greater wing of the sphenoid bone, has a length comprised between 4.5 mm and 7.5mm and a width of 3,5 mm. Studies on the cadaver showed that in 4,5% of individuals, it is divided to 2 or 3 components. It is crossed by: the mandibular nerve with its motor branch, the accessory meningeal artery, emissary veins, lesser superficial petrosal nerve. We should have in mind the possible bad steering

1142 Functional Neurosurgery of the introducer during surgery towards neighbouring foramina which are: anterior: the optic foramen, superior orbital fissure, foramen rotundum, foramen Vesalii, posterior: innominate canal of Arnold, foramen spinosum, foramen magnum and more medial: foramen lacerum. As soon as we enter the skull, the most important structures are the temporal lobe, anterior and medial: cavernous sinus, optic chiasm, internal carotid artery and posterior and medial: the brainstem.

SURGICAL METHODS Lesion of sensory trigeminal fibers can be induced thermically by heating the electrode tip, chemically by injecting pure sterile anhydrous glycerol, mechanically by inflating balloon of embolectomy catheter or finally by ionizing radiation. Magnetic Resonance Imaging or enhanced Computerized Tomography Scans are a routine examination and mandatory to exclude a cerebellopontine angle mass lesion. Blood test and biological examination are similar to those required for any surgical procedure. 1- Type of anesthesia: As in all neurosurgical procedures, monitoring of oxygen saturation, blood pressure, pulse and electro-cardiogram are essential to prevent any alteration in the vital functions. For percutaneous balloon compression (PBC) the surgical procedure is performed under general anesthesia with intratracheal intubation. In case of percutaneous retrogasserian glycerol (PRG), the operation can be practised also under general anesthesia or local anesthesia with sedation. In these two techniques, no patient cooperation is needed. Opposing this, radiofrequency coagulation (RFC) requires mild sedation during the puncture procedure, after that the patient is awakened and can complain of discomfort. Radiosurgery is realized in local anesthesia nevertheless the presence of a multidisciplinary team involving the neuroradiologist, the radiation physician and the neurosurgeon is essential to achieve this procedure. 2- Patient’s position: He is placed in the supine position, with the neck and thorax slightly flexed. Then, the hemi face is surgically cleaned. 3- Cannulation of the foramen oval: The classical Hartel percutaneous approach is defined by three landmarks on the affected side (Fig. 4): the first (1) corresponds to the location of the skin puncture: 2.5 cm lateral to the labial commissure. The second is on the inferior side of the zygomatic arch (2), 3 cm anterior to the external acoustic meatus. The third (3) is on the line joining the midpupillary point to the first point on the inferior orbitary rim. A freehand cannulation of the foramen oval via the Hartel’s route is performed. Skin puncture is made at the point “1” with the help of sharp tip of cannula towards the pterygo maxillary fossa. At one and the same time, steering of the introducer should be the intersection of two planes, one sagittal including the points 1 and 3 and the other lateral including the points 1 and 2. The index in contact with the internal side of the cheek guides the introducer in order not to cross it and penetrate the oral cavity (Fig. 5). Several attempts, under fluoroscopic guidance, are sometimes necessary to obtain the definitive trajectory. Crossing the FO can be impossible. Hardly any mention of this obstacle has been reported in the literature. Possible explanations of this difficulty refer to the narrowness

Percutaneous Techniques for Treatment of Trigeminal Neuralgia

1143

Fig. 4 Endocranial view of the skull base: 1: optic foramen, 2: superior orbital fissure, 3: foramen rotundum, 4: foramen lacerum, 5: foramen oval, 6: foramen spinosum, 7: internal auditory meatus, 8: jugular foramen, GG: Gasser ganglion

Fig. 5 Landmarks of the percutaneous approach via the Hartel’s route: 1: 2,5cm lateral to the labial commissure, 2: 3 cm anterior to the external acoustic meatus on the inferior side of the zygomatic arch, 3: on the line joining the midpupillary point to the first landmark on the inferior obituary rim.

or unusual anatomy of the FO. Inadvertent crossing also of other surrounding holes, as consequence of bad steering, may happen. The possibility of injury of vessels as middle meningeal artery or internal carotid artery and nerves as the optic nerve or the oculomotor nerves should be considered when planning the procedure. In order to reduce bad steering, some authors recommend the use of neuronavigation or frameless stereotactic CT scan for targeting the FO. Blood flow through the stylet and a hematoma in the cheek mean the interruption of the procedure which will be reperformed one to 2 weeks later. Crossing successfully the foramen oval is recognized by the neurosurgeon by seeing and feeling the masseter muscles shrinking. We can observe leak of CSF at the skin orifice. Its absence, at this moment of the procedure or later, excepted for glycerol injection, does not mean a wrong target or an unsuccessful operation.

1144 Functional Neurosurgery 4- X rays check: A C arm fluoroscope confirms the optimal location of the tip of the introducer which does not pass beyond the clivus on a sagittal view (Fig. 8). The correct trajectory is confirmed by the projection of the introducer at the posterior extremity of the osseous palate and its direction as bisectrix of the angle: superior edge of the petrous bone and clivus.

Fig. 6 Balloon compression: Landmarks of the Hartel’s route and skin puncture for balloon compression in a patient under general anesthesia and intubation

I – PBC A 14 gauge silicone catheter (9) with its introducer was positioned at the foramen oval without traversing it, so as not to introduce metallic material inside the skull (1). Then, the introducer was taken out while the plastic catheter was pushed 3 to 4 mm into the skull. 1- Embolectomy catheter: After removing the air from the balloon and verifying its imperviousness, a number 4 Fogarty catheter was threaded through the first catheter. To avoid its rupture, we ensure that its tip carrying the deflated balloon is located ahead. 2- Finally, the inflation of the balloon was achieved above the triangular pars with 0.7cc of contrast medium for 6 minutes. On X-ray sagittal view, this structure projects on both sides of the clivus knowing that GG projects below the sella floor. A pear shape balloon corresponds by the body to the exact outline of the GG and by the neck to triangular pars (Fig. 9). This cone shape has always been sought and is synonymous with post operative pain relief. With regard to literature data, these two values vary respectively from 0,4 to 0,9 cc and from one to 9 minutes. Some authors (8) use a computerized pressure system for pressure monitoring. The balloon opening pressure is around 2956 ± 185 mm Hg in Meckel's cave. On the opposite, all the authors emphasize and agree upon the location and the shape of the balloon above mentioned. After that, the balloon was deflated and all the material removed. Cheek is compressed for a short moment to avoid haematoma. During the lesionotomy, hypotension and bradycardia can be observed.

Percutaneous Techniques for Treatment of Trigeminal Neuralgia

1145

Fig. 7 Radiofrequency coagulation: Awakened patient without intubation: The stylet with its electrode inserted at the landmark located 2,5cm lateral to the labial commissure

II – RFC An insulated 19 gauge cannula with with its stylet is inserted. After crossing the foramen oval, the stylet is removed and replaced by the electrode (Fig. 7). Two types of electrode are available: straight tip for the V2 and V3 divisions and curved tip adapted for the V1 division. This lesionning electrode does not pass beyond the clivus (Fig. 8). Then, it is connected to the generator. For accuracy of the lesion, an electropysiological step is added to the fluoroscopic checking. Multiple parameters as the impedance, the stimulation, the frequency and the intensity of the current are monitored and displayed. Switch time allows setting of the lesion duration. 1- Stimulation: an electrical stimulation is realized at a low voltage (5c/s) in a conscious patient to confirm the good location of the electrode. Tingling and paresthesias are felt in the part of the face corresponding to the area of the preoperative pain. Clinically observable evoked motor responses can be induced and are a helpful indicator for an accurate location of the electrode in the trigeminal root (15). If not, the steering and the target will change till to obtain these sensations in the appropriate area of the face. 2- Test lesion: It is made by heating the uninsulated electrode tip at 45 degrees in a sedated patient, using intravenous propofol. Sensorial check in an awakened patient with pinprick and cotton should confirm the analgesia and the hypoesthesia in the required territory. 3- Definitive lesions: Usually, 2 to 3 lesions produced between 60 to 75 degrees are necessary. Each one has duration of one minute. During this lesion step, corneal reflex is monitored. The procedure will be stopped if it is reduced because in case of its disappearance, the consequence can be a keratitis.

1146 Functional Neurosurgery

Fig. 8 Radiofrequency coagulation: Sagittal skull Xrays showing a good location of the electrode. In dotted lines: the clivus and the superior edge of the petrous bone. The bisectrix of this angle is a continuation of the electrode.

Fig. 9 Balloon compression : Sagittal skull Xrays depicting the Fogarty catheter and the inflated balloon in a pear shape projecting on both sides of the clivus

III – PRG For this technique, the FO is punctured with a number 18 or 20 spinal needle (3). 1- Cysternography: After taking out the stylet, CSF leak is obtained. The needle should be repositioned in the Meckel’s cave if CSF does not drain. Immediately after, the needle is obturated. Then, the patient is placed in a sitting position. Under fluoroscopic check, injection of contrast medium into the trigeminal cistern is made until it is filled,. The aim is to measure the volume of the cistern which is about 0,4cc. To allow the escape of the contrast medium, patient is again returned to the supine position. 2- Injection of pure sterile anhydrous glycerol: the volume depends on the affected nerve branches (one or two or three). Glycerol is injected in sitting position in order to avoid its dissemination in the posterior fossa. The procedure is completed; however, the patient should keep a semi sitting position for 2 hours, necessary time for the effect of glycerol on the nociceptive fibres.

IV – STEREOTACTIC RADIOSURGERY Two essential modalities, Gammaknife (10) and Cyberknife (20) are possible with the same goal: to lesion the wanted target leaving unaffected the surrounding anatomical structures. The gamma knife and the cyberknife deliver a single isocenter plan via a 4-mm collimator with respectively 201 separate gamma-ray beams of radioactive cobalt-60 those intersect on the target or with seven noncoplanar arcs. For gamma knife, the head is attached in a stereotactic frame. In case of cyberknife, the patient does not need frame

Percutaneous Techniques for Treatment of Trigeminal Neuralgia

1147

fixation. Contrast enhanced T1 and T2 axial and coronal MR imaging is realized for accurate localisation of the trigeminal nerve and for the planning treatment. Stereotactic coordinates of the the target can be also based on an image fusion based on a MRI and a stereotactic CT scan. One of two parts of this nerve can be irradiated in one single exposure: the first is posterior corresponding to the entry zone of the trigeminal nerve or its exit from the pons, the second is more anterior on the proximal nerve root, close to the triangular pars portion. High dose irradiation, between 60 to 85 grays, is administrated with no more than 20 % of this dose at the surface of the brainstem. According to the literature data, a length of around 6 mm on the anterior portion of the nerve is currently the preferred target.

RESULTS Results are classified in 4 categories: Excellent results consist in pain free without side effects and off medication. Satisfactory results are characterized by complete pain relief but coexisting with a minor complication or requiring small posology of medication. They are observed in 95% of patients the day after surgery, in 80% one year after surgery, and in 70% of patients 20 years after the procedure (1, 3, 9, 14, 16, 17). The remaining patients complain of poor results dominated by moderate or severe dysesthesias or failure in case of misdiagnosis or impossibility to cross the FO. After an average follow up period equal or superior to 20 years, 30% to 35% of patients experience recurrences. This rate increases to 50% after a shorter follow up time in patients who underwent PRG. A second recurrence is rare whereas a third is exceptional. In case of radiosurgery, the initial pain relief rate varies from 77 to 96%. At a mean follow up time of 2 to five years, it decreases to 50%. Longer follow up period is essential to evaluate long term results.

MORBIDITY 1- Following PA Peroperative bleeding through the puncture site and haematoma of the cheek happen in the beginning of experience. Post operative vascular complications (12) as subarachnoid haemorrhage, arteriovenous fistula or intracerebral haematoma were exceptionally reported. The other complications are transient or permanent related to the ablative character of the PA. Among the first, we mention hypoesthesia of the painful area, masticatory weakness, cranial nerve deficits common to the three techniques. The multiple attempts to puncture the foramen oval can lead to injury of motor branch of the trigeminal nerve which results in mandibular movement limitation or masticatory weakness. This transient discomfort progressively improved within one year. Oculomotor nerve palsies were possible and reversible due to an excessive penetration of the balloon involving or compressing the posterior part of the cavernous sinus or the cisternal segment of these nerves. Blindness (2) explained by malpositioning of the introducer through the superior orbital fissure, and rhinorrhea (18) due probably to puncturing both the membranus portion of the Eustachian tube and Meckel’s cave were also reported.

1148 Functional Neurosurgery Distinctive morbidity according to each technique is as following: a- For BC: hypoacousia and buzzing (19), consequences of paresis of the tensor tympani and significant impairment of motor root. b- For RFC: anesthesia dolorosa and keratitis c- For PRG: high rates of hypesthesia and recurrences. 2- Following radiosurgery: Includes essentially facial numbness with a rate comprised between 0 and 16, 7% and exceptional symptoms of corneal keratitis.

point memo How to choose and to decide in the large armamentarium composed of three neurosurgical modalities (14, 17): microvascular decompression, radiosurgery and PA? That represents until today a matter of debate. It is obvious that the most suitable will depend on the patient’s opinion after explaining the different possibilities and secondly, the level of our experience and expertise. The first technique, requiring a rigorous learning curve, lead to a definitive treatment of the incriminated cause but should be considered carefully in patients with poor systemic condition. At present, it represents the treatment of choice. Recently, stereotactic radiosurgery is regarded as another useful promising option. It is a painless procedure in an outpatient visit when general anesthesia or surgery is not recommended. It provides delayed pain relief, from few days to few months after surgery. To date, this tool remains costly and not available everywhere. The PA are the most practiced despite their destructive aspect and consequently possible morbidity. Patients can enjoy pain free life immediately after surgery. They represent the best indication for a patient aged more than 60 years who requires an immediate pain relief for refractory trigeminal neuralgia. There is no consensus concerning the PA which will be performed. RFC requires an alert patient on the opposite of PBC and PRG techniques which do not need peroperative cooperation. PBC is indicated when the ophthalmic division is involved. We must weigh anesthesia dolorosa against recurrences in carrying out the surgical procedure. The first complication is due to a pronounced lesion whereas the second is the consequence of a mild or moderate lesion. Knowing the repeatable character of these procedures, the greatest care must be taken in lesioning: better to have a small controlled lesion than an uncontrolled one in this blind surgery. The PA described above has proved useful in achieving pain. Our results and data literature confirm that PA are simple, safe and effective procedures in patients who suffered from refractory trigeminal neuralgia. On the whole, their big advantages are: - From the surgical point of view: minimally invasive surgery easy to perform - Immediate post operative success equal at 95% - Short mean total procedure time: 40 minutes - Short hospital stay: 2 days, the patient is discharged the next morning. - Low cost of treatment

Percutaneous Techniques for Treatment of Trigeminal Neuralgia

1149

REFERENCES 1. Abdennebi B, Mahfouf L, Nedjahi T: Long-Term Results of Percutaneous Compression of the Gasserian Ganglion in Trigeminal Neuralgia (Series of 200 patients). Stereotact Funct Neurosurg 1997; 68:190-195 2. Egan R, Pless M, Shults WT: Monocular blindness as a complication of trigeminal radiofrequency rhizotomy. American Journal of Ophtalmology 2001; 131, 2, 237 – 240 3. Hakanson S: Trigeminal neuralgia treated by the injection of glycerol into the trigeminal cistern. Neurosurgery1981; 9, 638-646 4. Hartel F: Die Leitungsans thesie und injektions behandlung des ganglion Gasseri und der Trigem inusstmme langenbecks. Langenbecks Arch Klin Chir Ver Dtsch Z Chir 1911; 100: 193. 5. Janjua R M, Al Mefty O, Densler DW, et al: Dural relationships of Meckel cave and lateral wall of the cavernous sinus. Neurosurg. Focus 2008: 25 (6):E2, 1-12 6. Kirshner M: Electrokoaguation des ganglion Gasseri. Zentralbl Chir 1932; 47:2841 7. Kondziolka D, Lunsford LD, Flickinger JC, et al: Stereotactic radiosurgery for trigeminal neuralgia: a multiinstitutionalstudy using the gamma unit. J Neurosurg 1996, 84: 940-945 8. Lee S T, Chen J F, Dan N G, et al: Percutaneous trigeminal ganglion balloon compression for treatment of trigeminal neuralgia-Part I: Pressure recordings. Commentaries. Surgical neurology 2003, 59, 1, 63-67 9. Lichtor T, Mullan S: A 10 – year follow up review of percutaneous microcompression of the trigeminal ganglion. J Neurosurg 1990; 72: 49-54 10. Matsuda S, Serizawa T, Nagano O, et al: Comparison of 2 targeting methods in Gamma Knife surgery for trigeminal neuralgia. J Neurosurg 2008:109: 185-189 11. Mullan S, Lichtor T: Percutaneous microcompression of the trigeminal ganglion for trigeminal neuralgia. J Neurosurg 1983: 39: 1007-1012 12. Revuelta, R., Nathal, E., Balderrama, J., Tello, A., Zenteno, M.: External carotid artery fistula due to micro-compression of the gasserian ganglion for relief of trigeminal neuralgia. J Neurosurg 1993: 78: 499-500. 13. Shelden C, Pudenz R, Freshwater D, Crue B: Compression rather decompression for trigeminal neuralgia. J Neurosurg 1955: 12:123-126 14. Sindou M, Keravel Y, Abdennebi B, et al: Traitement neurochirurgical de la nevralgie trigeminale: Abord direct ou methode percutanee? Neurochirurgie 1987: 33, 2, 89111 15. Sindou M, Fobe JL, Berthier E, et al: Facial motor responses evoked by direct electrical stimulation of the trigeminal root. Localizing value for radiofrequency thermorhizotomy. Acta Neurochir 1994: 128, 1-4 16. Sweet WH, Wepsic JG: Controlled thermocoagulation of trigeminal ganglion and rootlets for differential destruction of pain fibers. J Neurosurg 1974: 40:143–156 17. Tatli M, Satici O, Kanpolat Y, Sindou M: Various surgical modalities for trigeminal neuralgia: literature study of respective long-term outcomes. Acta Neurochirurgica 2008: 150(3): 243-255 18. Ugur HC, Savas A, Elhan A, Kanpolat Y: Unanticipated complication of percutaneous radiofrequency trigeminal rhizotomy: rhinorrhea: report of three cases and a cadaver study: Neurosurgery 2004: 54(6): 1522-6 19. Urculo E, Alfaro R, Arrazola M,et al : Trochlear nerve palsy after repeated percutaneous balloon compression for recurrent trigeminal neuralgia: Case report and pathogenic considerations. Neurosurgery 2004: 54: 505-509. 20. Villavicencio AT, Lim M, Burneikiene S, et al: Cyberknife Radiosurgery for trigeminal neuralgia treatment: A preliminary multicenter experience. Neurosurgery2008: 62, 647-655

1150

The Management of Spasticity SASHA BURN1, JAMES DRAKE2 1

Consultant Paediatric Neurosurgeon, Royal Liverpool Children’s Hospital Alder Hey, Liverpool L12 2AP, UK 2 Department of Neurosurgery, Frenchay Hospital, Bristol, ROYAUME-UNI Key words: spasticity, botulinum toxin, chemical neurolysis, selective peripheral neurotomy, selective dorsal rhizotomy, intrathecal baclofen

INTRODUCTION Definition Spasticity has been traditionally defined as a motor disorder characterized by a velocity dependent increase in tonic stretch reflexes ie there is an increase in muscle tone in response to the stretch of a relaxed muscle. Spasticity develops when cerebral or spinal lesions involve the long descending tracts that control or influence the excitability of the lower motor neurone. Whilst spasticity forms part of the upper motor neurone (UMN) syndrome the above mentioned definition does not in fact include all parts of that syndrome. Therefore in 2005 a new the definition was suggested by the European working group EU-SPASM as follows: spasticity is disordered sensorimotor control, resulting from an upper motor neurone lesion, presenting as intermittent or sustained involuntary activation of muscles12.

The Management of Spasticity

1151

The clinical features of UMN syndrome are broadly divided into two groups, the negative and the positive phenomenon (table1). Table 1 Features of the UMN Syndrome

The clinical outcome from the UMN syndrome positive phenomena has 3 basic consequences: restriction of movement excessive or inappropriate movement pain

1152 Functional Neurosurgery These can produce a number of clinical consequences as detailed on table 2: Table 2 Basic and clinical consequences of UMN syndrome positive phenomena

Causes of spasticity are either spinal or cerebral. In the spinal origin group the most common causes are spinal cord injury which may be traumatic or non-traumatic and multiple sclerosis (MS). The prevalence of spasticity in spinal cord injury is 60-65% 9. In MS 1/3 of patients have moderate to severe spasticity 6. To add to the burden of management of these patients approximately 30% are not effectively treated with oral medication4. Spasticity of cerebral origin is commonly as a result of cerebral palsy, traumatic brain injury and stroke. At least 2/3 of CP patients suffer from spasticity to some degree3. The figures for brain injury vary according to the age at the time of the insult. 15% of adults with severe brain injury in the US suffer from spasticity5, the figure in

The Management of Spasticity

1153

children is much higher at 65%2. Spasticity following stroke has been reported to occur at anywhere between 40-65%10,14.

Humanistic and economic burden of severe spasticity. Severe intractable spasticity has a tremendous impact on many dimensions of the life of patients and their carers. Basic functions are impaired and serious consequences follow. The following areas are most affected: bowel and bladder function, sexual dysfunction, toileting, impaired mobility, contractures, pressure sores, pain, sleep and mood disturbances. The economic burden faced by the patient who has either never been able earn a living or who can no longer provide is large enough but when coupled with the increasing caring demands and therefore decreasing income of a carer the situation often becomes untenable. Therefore it is in our interest to reduce the damaging effects of spasticity in the most economical way possible.

ASSESSMENT Treatment should be tailored towards the needs of each individual patient therefore an accurate initial assessment is a key part of treatment. Ideally assessment takes place in a multidisciplinary team (MDT) setting and team members should include a physician, dietician, physiotherapist, occupational therapist and orthotist wherever possible. The history should be taken followed by the examination which falls into 3 sections: observation, active movement and resistance to passive movement. A suggested structured method of history taking would include running through a 24 hour period for the patient: how do they get up in the morning; completion of tasks; posture and positioning throughout the day; bladder, bowel, skin hygiene and general health and finally sleep. Assessment of active movement should be done using the Medical Research Council (MRC) grading of muscle strength (table 3) and assessment of resistance to Table 3 MRC Grading of Muscle Strength

1154 Functional Neurosurgery passive movement is best measured using the modified Ashworth scale (table 4). Useful tips for assessing a patient using the Modified Ashworth Scale include moving the limbs into the best alignment possible recording this position for future assessments. Perform 3 passive movements only and recording the score felt on the third movement and regulate the speed of movement by counting 1001, 1002, 1003. Various tools are available for recording assessments known as quantitative outcome measures and these give a valuable baseline against which the effectiveness of any intervention can be measured (table 5). Table 4 Modified Ashworth Scale

At the end of the assessment goals should be discussed and set thus giving a target for therapy. These may include: sitting in wheel chair more comfortable, sleeping through the night, easier intermittent catheterisation for the carer, being able to clean hands better or being able to walk more easily.

The Management of Spasticity Table 5 Outcome measures13

1155

1156 Functional Neurosurgery

EDUCATION AND PROMOTING SELF MANAGEMENT It is now recognised that improved quality of care and outcomes comes from a partnership between the patient and the health care provider. Education and self management forms an integral part of improved care. Information can be passed on to patients and their carers in verbal or written format (including diagrams) and should include advice on maintaining movement and adequate positioning and recognising and preventing factors that may exacerbate spasticity and spasms. These can be divided into cutaneous stimuli and visceral stimuli. Cutaneous stimuli include skin that is red or inflamed, broken, infected; pressure sores; ingrown toenails; tight fitting clothes or urinary bag straps or uncomfortable orthotics or seating systems. Visceral stimuli include any systemic or localised infection; bowel dysfunction such as constipation or diarrhoea; bladder dysfunction such as infection, retention or incomplete emptying or deep vein thrombosis.

PHYSICAL MANAGEMENT TECHNIQUES Physical management strategies include: 1) Prevention of contractures by active and passive movement, standing, stretching, using splints. 2) Change in dominant posture ie flexing predominantly straight legs 3) Fitness regime for strength and cardiovascular fitness The types that activity that may be carried out include standing, active exercise, passive movement, stretches, splinting, casting and the use of orthotics, wheelchair posture and seating and functional electrical stimulation (FES).

ORAL MEDICATION Drug treatment in spasticity includes oral medication to target generalised spasticity, treatment of focal problems with botulinum toxin or chemical neurolysis and treatment with a regional approach such as with intrathecal baclofen or phenol. The common oral medications used in spasticity are detailed in table 6. As with all medication prescriptions a detailed drug history is essential and care should be taken over combining drugs.

The Management of Spasticity

Fig. 1 Algorithm for spasticity management13

1157

1158 Functional Neurosurgery Table 6 Oral medication for spasticity

The Management of Spasticity

1159

FOCAL TREATMENT If a patient’s spasticity has a particularly focal element and other management strategies have not been effective then there are focal therapies available. These include: reversible therapies such as botulinum toxin (BTX) and irreversible therapies such as chemical neurolysis and selective peripheral neurotomy. The aim is to re-equilibrate the tonic balance between agonist and antagonist muscles by reducing excess spasticity. Botulinum toxin A is the most commonly used treatment as it is widely available and reversible. The toxin is a naturally occurring neurotoxin produced by Clostridium botulinum and it works by inhibiting the release of acetylcholine at the neuromuscular junction7. BTX should be given in a setting which will also provide stretching exercises and splinting post injection to maximise the effect. Whilst this effective itself is permanent the clinical effect in fact is not as the nerve sprouts and re-innervates the muscle leading to recovery in a couple of months. BTX injections are given intramuscularly and are therefore painful which may necessitate administration under general anaesthetic in children. The main side effect of BTX is in fact its therapeutic effect of causing weakness which may make functions such as grip strength or walking more difficult. Improvement in accuracy of injection may be obtained by using electromyographic (EMG) guidance. Rare side effects such as generalised weakness, fatigue, anaphylaxis and cardiovascular effects have also been reported. Table 7 Common focal areas of spasticity and responsible muscle groups

1160 Functional Neurosurgery Chemical neurolysis is a non-reversible local injection of either phenol or ethanol which acts by destruction of neural tissue by protein denaturation in both myelinated and unmyelinated fibres. Injections are into either peripheral nerves or muscles (see table 8) and side effects include loss of sensation of dysaesthesia as a mixed nerve is being injected and loss of power as with BTX injections. The effect usually lasts for about 6 months after which time muscles are re-innervated therefore the treatment is most beneficial in patients with transient neurological problems7. Table 8 Targets for neurolysis

If BTX and chemical neurolysis have both run their course then selective peripheral neurotomy (SPN) may have a role. In order to select appropriate patients preoperative motor blocks using long lasting anaesthetics such as bupivicaine (targets as in table 10) which mimick the affect of surgery are essential to establish the objectives of neurotomy8. The operation consists of partial sectioning of one or more motor branches of the nerves innervating the target muscles. The operation is done under general anaesthetic but without long lasting muscle paralysis. Once the nerve is dissected free the branches should be tested with a nerve stimulator in order to identify the correct roots for section. The branches thought to be responsible for the spasticity are then sectioned close to the muscle mass in order to ensure only motor branches are cut and the proximal end is diathermied to help prevent nerve regrowth. The effectiveness of the section can then be tested by stimulating the nerve proximal to the section and distal to it. If the response from the muscle is still prominent then further sectioning of the nerve can take place.

The Management of Spasticity

1161

In patients with a more global spasticity ie spastic diplegia and some patients with spastic quadriplegia selective dorsal rhizotomy (SDR) may the treatment of choice. Reduction of input to the spinal interneurons following sectioning of afferents in the dorsal roots reduces the excitation of the alpha neurons and consequent spasticity. The operation is carried out either at the level of the conus or at the level of the exit foramina of the lumbosacral roots. The most common procedure used is a combination of the techniques described by Fasano and Peacock11. Following a L1-S1 laminectomy or laminoplasty the dorsal roots are identified and separated from the ventral roots. The rootlets are then stimulated with electromyography (EMG) to identify those that are innervating the most dysfunctional muscle. 20-70% (most commonly 50-70%) of the posterior root is sectioned. As more limited section may be made in L4 in order to preserve quadriceps function and if ankle plantar flexor spasticity is a problem then partial rhizotomy of S2 may be performed. Postoperatively patients require careful analgesia as muscle dissection is extensive. Once mobilising patients require intensive physiotherapy and use of orthotics to maximise outcome. Complications include intraoperative bronchospasm, urinary incontinence, dysaesthesia, hip subluxation and possible spinal deformity.

INTRATHECAL BACLOFEN The effectiveness of intrathecal baclofen (ITB) in treating spasticity has been recognised since 19851. Its use is dependent on several restrictive variables such as the availability of funding not only for the pump but for the regular refills as well. The patient needs to be able to access a centre where the pump rate can be altered as necessary and any complications associated with having an implant can be dealt with. Thus selection of patients for this mode of therapy should be done with these factors in mind. IT baclofen is thought to act in the superficial layers of the spinal cord, Rexed layers I-II, it has a pre-synaptic inhibitory effect and reduces the release of the excitatory neurotransmitter glutamate. It has a post-synaptic effect of reducing the firing of motor neurones. Intrathecal delivery results in direct delivery of baclofen to the GABA receptors thus maximising the antispasmodic effect and reducing the side effects associated with oral administration. Serious effects of intrathecal baclofen overdose can lead to loss of consciousness and include depressed respiration, drowsiness, rostral progression of hypotonia, dizziness, diplopia, nausea and vomiting. Other side effects include headache, confusion, seizures, hypotension, dysphagia, dysarthria, nystagmus, urinary incontinence or retention, ileus, constipation or diarrhoea, sexual dysfunction, parasthesia, bradycardia, allergic reactions, peripheral oedema, deep vein thrombosis. Symptoms of baclofen underdose include pruritus, hypotension, parasthesias, fever and altered mental state. Acute withdrawal of baclofen can cause pyrexia, altered mental state, exaggerated rebound spasticity and muscle rigidity that may progress to rhabdomyolysis, multiple organ system failure and death. Selection criteria for a baclofen pump should include: severe spasticity (Modified

1162 Functional Neurosurgery Ashworth Grade 2 or more) and /or severe dystonia; failure of physical adjuncts, oral medication, nursing, physio and occupational therapy to adequately control spasticity; awareness of the patient and carers of the long-term commitment involved with ITB therapy. Once selected, patients undergo an ITB test dose of 25mcg given via lumbar puncture. The patient should be observed carefully for symptoms or signs of overdose and assessed by a physiotherapist using repeat outcome measures. If the patient responds to the assessment then they are put forward for pump placement. Prior to surgery the optimal site for the pump is marked out avoiding the potential for rubbing on waist bands. The patient is positioned on the operating table once anaesthetised in the lateral position. The intrathecal catheter is introduced following a laminotomy using a Tuohy needle. The catheter is passed in the intrathecal space to the midthoracic region to treat lower limb spasticity and to the cervical region to treat spastic paraplegia. Once the abdominal pocket has been made, which may be subfascial if the patient is very thin or in a child, the intrathecal catheter is passed anteriorly to the abdominal pocket and connected to the pump which has been filled with baclofen. Once the wounds are closed the intrathecal tubing is primed with baclofen and the pump is switched on. Post operatively the abdominal wound may be bound with a pressure bandage to help reduce incidence of seroma. The patient should then be assessed daily with repeatable assessment measures and the dose of baclofen slowly increased against clinical response. Any oral medication is continued until a satisfactory response has been achieved by the pump. It is helpful if patients are managed in a rehabilitation centre to maximise physiotherapy following the implantation. Complications specific to baclofen pump insertion include catheter disconnection and micro-fracture, CSF leak and infection. The battery life is currently 7 years and the pump will need to be refilled on a regular basis. IT baclofen is supplied typically at concentrations of 500mcg per ml and 2 000mcg per ml. The concentration used depends on dose required. In a patient with high dose requirement (in the region of 1000mcg per 24hrs) or in patient who lives far away from the neurosurgical centre then the higher concentration would be preferable. ITB is a very effective treatment in spasticity and dystonia and is favoured because of the ability to control the degree of tone reduction and the reversibility of the pump. However disadvantages include complications and on-going costs.

The Management of Spasticity

1163

Fig. 2 Example of algorithm for decision making for neurosurgical treatment in children with spasticity of lower limbs8

1164 Functional Neurosurgery

REFERENCES 1. Albright AL. ‘Intrathecal baclofen for childhood hypertonia’ Childs Nerv Syst (2007) 23:971-979 2. Dumas H M, Haley S M, Carey T M, Ludlow L H, Rabin J P. Lower extremity spasticity as an early marker of ambulatory recovery following traumatic brain injury. Childs Nerv Syst 2003; 19: 114-118. 3. Gerszten P C, Albright A L, Johnstone G F. Intrathecal baclofen infusion and subsequent orthopaedic surgery in patients with spastic cerebral palsy. J Neurosurg 1998; 88: 10091013. 4. Gianino J M, York M M, Paice J A, Shott S. Quality of life: effect of reduced spasticity from intrathecal baclofen. J Neurosci Nurs 1998; 30: 47-54. 5. Nuttin B, Ivanhoe C, Albright L, Dimtrijevic M, Saltuari L. Intrathecal baclofen therapy for spasticity of cerebral origin: Cerebral Palsy and Brain Injury. Neuromodulation 1999; 2: 120-132. 6. Rizzo M A, Hadjimichael O C, Preiningerova J, Vollmer T L. Prevalence and treatment of spasticity reported by multiple sclerosis patients. Multiple Sclerosis 2004; 10: 589-95. 7. Ronan S, Gold JT ‘Nonoperative management of spasticity in children’ Childs Nerv System (2007) 23:943-956 8. Sindou MP, Simon F, Mertens P, Decq P. ‘Selective peripheral neurotomy (SPN) for spasticity in childhood’ Childs Nerv System (2007) 23:957-970 9. Skold C, Levi R, Seiger A. Spasticity after traumatic spinal cord injury: nature, severity and location. Arch Phys Med Rehabil 1999; 80: 1548-57 10. Sommerfield D K, Eek E U B, Svensson A K, Holmqvist, Von Arbin M H. Spasticity after stroke: its occurrence and association with motor impairments and activity limitations. Stroke 2004; 35; 134-140. 11. Steinbok P. ‘Selective dorsal rhizotomy for spastic cerebral palsy: a review’ Childs Nerv Syst (2007) 23:981-990 12. Stevenson VL, Marsden JF (2006) ‘What is spasticity?’ In Stevenson VL, Jarrett (eds) ‘Spasticity Management A Practical Multidisciplinary Guide’ Informa Healthcare, UK 1:3-14. 13. Stevenson VL, Lockley LJ, Jarrett (2006) ‘Assessment of the individual with spasticity’. Ed:Stevenson VL, Jarrett L ‘Spasticity Management A Practical Multidisciplinary Guide’ Informa Healthcare, UK 2:15-26 14. Watkins C L, Leathley M J, Gregson J M, Moore A P, Smith T L, Sharama A K. Prevalence of spasticity post stroke. Clin Rehabil 2002; 16(5): 15-22.

1165

Neurosurgical Management of Spasticity PATRICK MERTENS M.D., Ph.D. and MARC SINDOU M.D., D Sc. Department of Neurosurgery, Hopital Pierre Wertheimer, University Claude-Bernard of Lyon, 59 Boulevard Pinel, 69003 Lyon , France Key words: spasticity, neurosurgical management, Intra-Thecal Baclofen therapy (ITB), Selective peripheral neurotomies (SPN), Dorsal Root Entry Zone (DREZ)

Introduction Spasticity should only be treated when excess of muscular tone leads to further functional losses, impairs locomotion or induces deformities. As for most procedures in functional neurosurgery, surgery for spasticity has to be considered in second line after failure of physical therapy, medications and Botulinum toxin injections. The various surgical methods are classified according to whether their impacts are large or focal and whether the effects are temporary or permanent. They include IntraThecal Baclofen Therapy (ITB) and selective lesions in the peripheral nerves, dorsal roots, dorsal root entry zone in the spinal cord and the spinal cord itself (Fig 1).

Fig. 1 Managing spasticity, based on effects of techniques : whether focal or general and whether permanent or temporary.

When dealing with surgery for spasticity, the first step is to define the objective(s) of the treatment, improvement in function, prevention of deformities, or alleviation of discomfort and pain in very disabled patients; in other words, define what can be gained and what will not be obtained with surgery. Whatever the procedure may be, it must be performed so that excess of tone is reduced without suppressing useful muscular tone or impairing any residual

1166 Functional Neurosurgery motor/sensory functions. In patients who retain some masked voluntary motility, the goal is to reequilibrate the articular balance between paretic agonist muscles and spastic antagonist muscles, resulting in improvement in [or reappearance of] voluntary motility. In patients with poor residual or no motor function preoperatively, the aim is to stop the progressive orthopaedic deformities and improve comfort. Complementary orthopedic operations are required in patients with irreducible contractures, tendon retractions and/or joint deformities. It seems logical to control first the spasticity itself, and only secondarily try to correct its neuro-orthopedic consequences.

Intra-Thecal Baclofen therapy (ITB) ITB was developed and reported by PENN and KROIN in 1985 (10), The method consists of delivering Baclofen (a GABA-B agonist) in the CSF close to an area of high concentrations of gamma amonobutyric acid-B binding sites : the spinal dorsal horn. This gabaergic molecule is able to decrease the transmission of sensory inputs and thus to decrease reflex hyperactivity. Pharmacokinetic of the baclofen infused intrathecally reduces significatively its side-effects compared to the oral route (namely weakness, drowsiness, nausea, confusion, seizures…). This way of delivering baclofen allows to decrease dramatically its dosage from an average of 10-90mg per day orally to an average of 20-800 mg per day intrathecally. ITB is delivered by a device implanted subcutaneously (under the abdominal skin), including a reservoir containing the drug that is refilled percutaneously every 3 to 6 months on average and a programmable pump that provides the desired flow through a catheter directed to the intrathecal space. The tip of the catheter is placed through a lumbar puncture at the level of the conus medullaris (T12-L1 vertebral levels) for paraplegic patients. Only one model of programmable pump is available (Synchromed IIÑ from Medtronic company, US). A trial of ITB is required before performing the surgical implantation of the pump. The test allows to define the appropriate dosage of intrathecal baclofen suppressing the excess of spasticity without impairing the useful muscular tone necessary to stand and for ambulatory patients to walk. The test can be performed via bolus injections of baclofen through a lumbar puncture when just a « on-off » effect is checked. In the absence of a positive response, indicated by a two-point reduction in Ashworth score 4 to 8 hours following drug administration, the bolus dose is increased by 25µg increments up to a maximum bolus of 100 – 150 µg. Once a positive response is observed without unacceptable loss of function, the patient is considered to be a candidate for pump implantation. The “bolus method” can produce a brutal or exaggerated loss of motor power and muscle tone, which might be interpretated by the patient as a decrease in functional status. In patients with abilities to walk, the bolus-test should be replaced by a “continuous-infusion-test”, using an external automatic injection pump connected to a temporary intrathecal catheter. The test should last a few days to an entire week so that functional capabilities can be reliably evaluated. Best indication for ITB is spasticity in relation with spinal lesion, due to vertebral

Neurosurgical Management of Spasticity

1167

trauma or advanced multiple sclerosis. ITB can also be proposed for hyperspastic states due to brain stem or brain lesion and also for severely affected cerebral palsy patients

Selective peripheral neurotomies (SPN) Peripheral Neurotomies were introduced for the treatment of localized spastic deformities in the foot by Stoffel (14). More recently Gros and associates (5), Sindou and Mertens (7, 12) have made PN more selective by using microsurgery for fine dissection of fascicles and mapping with intraoperative electrical stimulation to identify the respective function of the individual nerve fascicles. Selective PN consist of a partial sectioning of one or several motor branches of the nerve(s) innervating the targeted muscle(s) in which spasticity is considered to be excessive. It interrupts the segmental reflex arc by acting on both the afferent and the efferent pathways. Neurotomy must never involve the sensory fascicles of a mixed nerve trunk, as even partial section of the later could be responsible for deafferentation pain. There is no scientific basis for defining the extent of the section. However all surgeons agree that to be effective a partial neurotomy must section in the order of 5080% of the motor fibers of a targeted muscle.

Technical principles ■ Pre-operative - Motor blocks - : Before considering SPN, a test using motor blocks innervating the targeted muscle(s) is of prime importance. These blocks, using local anesthetics such as long-lasting bupivacaine, enable the surgeon to evaluate the motor strength of antagonist muscles and determine whether limitations in articular amplitude result from spasticity or from musculotendinous contractures / articular ankyloses. Botulinum toxin injections can be used as a "prolonged" test for several weeks or months, as their effects mimic the outcome of selective neurotomies on the injected muscles. ■ Anesthesia : Neurotomy is performed under general anesthesia. Muscle relaxant drugs must be avoided as much as possible and nitrogen monoxide and propofol are contraindicated because they would modify reflex excitability and might impair intraoperative testing. Further, the general anesthesia has to be performed without long-lasting curarization so that the motor responses elicited by bipolar electrical stimulation of motor branches can be detected to identify the nerve. ■ Mapping : Nerve identification is based on the descriptive anatomy but needs to be checked by study of the muscular responses to electrical stimulation. Parameters of stimulation are : 2Hz frequency, low intensity – usually at 1 mA- to avoid electrical diffusion and incorrect interpretation. Bipolar (or even a triple stimulation hook that limits current diffusion, composed of an anode between two cathodes), is used to grasp the nerve branch to be stimulated. Finally, the muscular responses to stimulation are appreciated clinically by the surgeon himself or by EMG recordings. ■ Sectioning : After identification of the fascicles considered responsible for harmful spasticity), variable proportions (50-80% depending on the degree of preoperative spasticity) of the selected fascicles are resected under the operating microscope, near the

1168 Functional Neurosurgery muscle to ensure that only the motor fascicles are cut. The resection is 5mm long; the proximal stump is coagulated with a fine bipolar forceps to prevent regrowth of fibers. The effect of each nerve resection on spasticity is then evaluated by comparing muscle responses to electrical stimulation, proximally and then distally to the resected portion of the nerve. If the response after proximal stimulation is still intense, further resection can be performed. Aim is to decrease muscle innervation enough to avoid further recurrence of spasticity by "take-over" (reinnervation or "adoption" of muscular fibers denervated as a result of the neurotomy, by the surrounding motor fibers). ■ Postoperative care : Immobilisation and casts are not necessary after SPN. Patients are encouraged to mobilize the limb as soon as possible. As early as cicatrisation is obtained, a tailored program of rehabilitation begins for several months to progressively stretch the previous spastic muscles and facilitate new functional capacities.

PNS for the upper limb (2,6,7) Pectoralis major muscle neurotomy for spastic shoulder in adduction Neurotomy of collateral branches of the brachial plexus innervating the pectoralis major are indicated for spasticity of the shoulder with internal rotation and adduction. The skin incision is made at the innermost part of the deltopectoral sulcus and curves along the clavicular axis. First, the clavipectoralis fascia is opened. Then the upper border of the pectoralis major muscle is reflected downward. Close to the thoracoacromialis artery, the ansa of the pectoralis muscle is identified with the aid of a nerve stimulator. Teres major muscle neurotomy for spastic shoulder Neurotomy of collateral branches of the brachial plexus innervating the teres major are also indicated for spasticity of the shoulder with internal rotation and adduction. The skin incision follows the inner border of teres major, from the lower border of the deltoid muscle's posterior head to the lower extremity of the scapula. The lower border of the long portion of brachii triceps constitutes the upper limit of the approach. The dissection continues deeply between teres minor and major muscles. In the vicinity of the subscapularis artery, the nerve ending on teres major is identified. The nerve is surrounded by thick fat when approaching the anterior facet of the muscle body. Musculo-cutaneous neurotomy for spastic elbow in flexion Neurotomy of the musculo-cutaneous nerve is indicated for spasticity of the elbow with flexion, depending on the biceps brachii and the brachialis muscles. The skin incision is performed longitudinally. It extends from the inferior edge of pectoralis major, medial to the biceps brachii, down to 5 cm. The superficial fascia is opened between the biceps laterally and the brachialis medially. The brachial artery and median nerve exit medially. The dissection proceeds in this space, where the musculocutaneous nerve lies anterior to the brachialis muscle. Opening the epinerium allows the fascicles of the nerve to be dissected under high magnification of the operating microscope. The motor fascicles are distinguished from the sensitive ones by using the nerve stimulator. Median neurotomy spastic wrist and fingers Neurotomy of the median nerve is indicated for spasticity of the forearm with pronation depending on the pronator teres and quadratus muscle and spasticity of

Neurosurgical Management of Spasticity

1169

the wrist with flexion depending on the flexor carpi radialis and palmaris longus muscles. For the hand, median neurotomy is indicated for spasticity of the fingers with flexion depending on the flexor digitorum superficialis (flexion of proximal interphalangeal joint and metacarpophalangeal joint) and on the flexor digitorum profondus muscle (flexion of distal interphalangeal, proximal interphalangeal, and metacarpophalangeal joint), partly innervated by the median nerve. Swan neck deformation of the fingers depending on the lumbrical and interosseous muscles can be limited by neurotomy, these muscles being innervated by the median and ulnar nerves. Concerning the thumb, neurotomy of the median nerve is indicated for spasticity with flexion and adduction/flexion (thumb-in-palm deformity) depending on the flexor pollicis longus. The skin incision begins 2 to 3 cm above the flexion line of the elbow, medial to the biceps brachii tendon, passes through the elbow, and curves toward the junction of the upper and middle thirds of the anterior forearm. Thereafter, the median nerve is searched medially to the brachial artery and recognized at the elbow, deeply under the lacertus fibrosus, which is cut. Sharp dissection is used to separate all the muscular branches of the median nerve. The pronators teres belly with its two heads is retracted medially and distally so that its muscular branches can be inspected. This muscle is retracted up and laterally while the flexor carpi radialis is pulled down and medially. The muscular branches to the flexor carpi radialis and to the flexor digitorum superficialis can then be seen. Finally, the latter is retracted medially uncovering the branches to the flexor digitorum profondus, the flexor pollicis longus, and the pronator quadratus. These latter muscular branches may be individualized as separate branches or remain together in the distal trunk of the anterior interosseous nerve. Sometimes, it may be useful to divide the fibrous arch of the flexor digitorum superficialis muscle to make the dissection easier. This wide approach with a large dissection along the anterior compartment of the forearm is necessary as there is no alternative allowing a safe control of all the muscular branches of the median nerve. An attempt to dissect the motor fascicles proximally in the trunk of the median nerve expose to risk of sensory complications, especially of developing a complex regional pain syndrome as motor, sensitive and vegetative fibers are mixed in the fascicles composing median nerve at this level. Ulnar neurotomy for wrist and fingers Neurotomy of the ulnar nerve is also indicated for spastic wrist in flexion and ulnar deviation both depending on the flexor carpi ulnaris. In the hand, ulnar neurotomy is indicated for spasticity of the fingers with flexion depending on the flexor digitorum profondus muscle (flexion of distal interphalangeal, proximal interphalangeal, and metacarpophalangeal joint), partly innervated by the ulnar nerve. A separate arched skin incision is performed to expose the ulnar nerve at the medial part of the elbow. After subcutaneous dissection, the ulnar nerve is identified medially to the medial epicondyle, then distally it enters between the two heads of the flexor carpi ulnaris. There, the motor branches to this latter muscle are identified. More distally, the branches to the medial half of the flexor digitorum profondus are found. Ulnar neurotomy is also indicated for spasticity with a “thumb in palm” deformity (adducted and flexed thumb). For this indication, it is preferable to control the ulnar nerve at the level of the wrist by a short skin incision just lateral to the insertion of the ulnar carpi flexor muscle on the pisiform bone. After section of the expansion of the

1170 Functional Neurosurgery flexor retinaculum, the division of the nerve between a superficial sensory branch and a motor deep branch is identified. Under magnification and stimulation, the motor fascicles for the adductor pollicis muscle and the deep part of the flexor pollicis brevis are identified and partially sectionned.

PNS for the lower limb (2,7,12) Obturator neurotomy for spastic hip Obturator nerve SPN reduce spasticity in adductor muscles. It is often proposed to diplegic children with cerebral palsy when their walking is hampered by scissoring posture of the lower limbs. It can also be proposed to facilitate perineal toilet and selfcatheterization. To isolated the anterior branch of the obturator nerve a transverse skin incision is performed in the hip flexion fold, centred on the prominence of the adductor longus tendon. This incision facilitates adductor longus tenotomy when considered in the same surgical procedure. The dissection is conducted laterally to the adductor longus muscle body just below the subpubic canal. The posterior branch is situated more deeply and should be spared to preserve the muscles useful for the stabilization of the hip. Hamstring muscles neurotomy for spastic knee in flexion Hamstring neurotomy counters the flexion deformity of the knees. The transverse incision is performed in the gluteal fold, centred on the groove between the ischium and the trochanter major. After retraction of the fibers of the gluteus maximus, the sciatic nerve is identified in the depth of the incision. The branches to the hamstring muscles are isolated at the lateral border of the nerve and identified by the responses of the semitendinosus and semimembranosus muscles. Tibial neurotomy for the spastic foot Tibial neurotomy is indicated for the treatment of equino-varus spastic foot with or without claw toes. All motor branches of the tibial nerve at the popliteal fossa (i.e., the nerves to gastrocnemius and soleus, tibialis posterioris, popliteus, flexor hallucis longus, and flexor digitorum longus) are identified and isolated. The skin incision can be vertical, on either side of the popliteal fossa. Over recent years, a transverse incision in the popliteal fossa, which gives a much better long-term aesthetic result, has been adopted. The first nerve been identified is the sensory medial cutaneous nerve of the leg. Situated immediately anteriorly to the saphenous vein, it must be spared. More deeply, the tibial nerve trunk, from which the nerves to the lateral and medial gastrocnemius come into view, is easily identified. The superior soleus nerve is situated in the midline, just posterior to the tibial nerve (often via a common branch with the lateral gastrocnemius). The effect of a soleus neurotomy is assessed by the immediate intraoperative disappearance of ankle clonus. By retracting the tibial nerve trunk medially, the other branches can be identified by electrical stimulation as they emerge from the lateral edge of the tibial nerve trunk. The most lateral branch is often the popliteal nerve, followed by the tibialis posterior nerve and finally by the inferior soleus nerve. To avoid a large dissection of the posterior compartment of the leg to control all the branches for flexor muscles of the toes, it is possible to open the tibial nerve trunk in the distal part of the popliteal fossa. After dissection of the epineurium, the motor

Neurosurgical Management of Spasticity

1171

fascicles for flexor digitorum and hallux longus muscles can be identified by tripolar stimulation in the anterior and lateral compartments of the nerve trunk. Care has to be taken to avoid any sensory fascicles lesion and to reserve section to fascicles with a clear muscular responses at the lowest intensity of stimulation. Some fascicles, often larger, can give a toe flexion response via intrinsic toe flexors. However, neurotomy of these fascicles is not recommended, if they cannot be clearly individualized at this level as they be mixed with sensory fibers. Anterior Tibial neurotomy for Extensor Hallucis This neurotomy (rarely performed) is indicated to treat permanent extension of the hallux (permanent Babinski reflex) making difficult to wear shoes and after botulinum toxin injections fail. In practice, this neurotomy may be indicated after unjustified section of the flexor hallucis tendon, responsible for a disequilibrium that favours the extensor. A vertical incision is centered on the junction between the tibialis anterior and the extensor hallucis, at the middle third of the anterior side of the leg. The tibial nerve is situated deeply between these two muscle heads and the neurotomy is performed on the motor branch to the extensor hallucis. Femoral neurotomy for spastic quadriceps Femoral neurotomy is indicated to treat excessive spasticity of the quadriceps muscle. This muscle is very often spastic and can interfere with gait by limiting knee flexion during the swing phase. Given its "strategic" importance in maintaining upright posture, a motor block is an essential part of the preoperative evaluation. The neurotomy mainly concerns the motor branch to the rectus femoris and vastus intermedius muscles. The incision is horizontal in the hip flexion fold. The dissection passes medial to the sartorius muscle body and exposes the branches of the femoral nerve. First the nerve to the rectus femoris and then, more deeply, the nerve to the vastus intermedius are identified by electrical stimulations taking care to save the large number of sensory branches of this nerve.

Surgery on dorsal spinal roots In 1898, using the animal model of mesencephalic trans-sectioning, Sherrington described that decerebration rigidity could be abolished by sectioning dorsal roots. From these experimental data, Foerster in 1908 performed the first dorsal rhizotomies from L1 to S2 (not L4, root of quadriceps) for the treatment of lower limb spasticity in cerebral palsy (4). Then the dorsal rhizotomy procedure was refined by a number of eminent neurosurgeons (5,3,9,1). Surgical techniques : Dorsal rhizotomies are most frequently used for children with cerebral palsy. Surgical approaches for dorsal rhizotomies may be significantly different from one team to another. The most classical technique – described by Peacock and Arens and Abbott et al. (1) is as follows. The L1 through S1 laminae are removed using a power saw, which allows replacement of the lamina at the end of the procedure. Bipolar stimulation of the sensory roots (or rootlets), usually of L2 through S1 bilaterally, is carried out using a multichannel EMG recorder to allow electrical monitoring outside the myotome of the

1172 Functional Neurosurgery root being stimulated. In addition, it is important to palpate the leg muscles for evidence of contraction. Roots which, when stimulated, cause either muscle activity outside of its myotome or activity lasting after cessation of the stimulus current are deemed abnormal and they are separated into their rootlets. The rootlets are in turn stimulated and the same criteria are used to judge their normality. Abnormally responsive rootlets are the best candidates to be cut. To reduce furthermore the invasiveness of the approach, in 2001 Sindou designed the “staged interlaminar (IL) approach” (11). The level(s) depends on the roots to be targeted according to the preoperative chart (= i.e., the program elaborated with the rehabilitation team). The lumbo-sacral spine is approached posteriorly on the midline, so that the preselected interlaminar spaces can be reached. After resecting the flavum ligament, the interlaminar space has to be enlarged by resecting (in the order of) the lower half of the sus-jacent and the upper half of the sub-jacent laminae. Then dural sheath is opened on the midline over two centimenters. L2 and L3 roots can be reached through L1-L2 opening, L4 and L5 roots through L3-L4 IL opening, S1-S2 roots through L5-S1 IL opening. Generally, the dorsal rootlets (five on average) are easily identified, as they are grouped posteriorly to the ventral root, separated from the latter by an arachnoid fold. Evoked motor responses to stimulation (with a bipolar electrical stimulator) are tested for ventral and then dorsal root (rootlets). Threshold for obtaining motor responses by stimulating dorsal root (rootlets) is at least three times the one of the corresponding ventral root (rootlets). After identification of the dorsal rootlets, the appropriate number of them is divided, between one-third and two-thirds of the overall dorsal rootlets, according to the preoperative chart. Then, the dural incision is tightly sutured and the dural suture line covered with fat tissue harvested from the subcutaneous layer. Whatever the modality of the dorsal rhizotomy may be, surgery is tailored according to preoperative status. The results of posterior rhizotomies in children with cerebral palsy have been recently reported in several publications. Briefly, these publications show that about 75% of the patients had nearly normal muscle tone at one year or more after surgery, that no longer limited the residual voluntary movements of limbs. After physical therapy and rehabilitation program, most children demonstrated improved stability in sitting and/or increased efficiency in walking. But installed deformities were not retrocessive and could needed complementary orthopeadic surgery.

Surgery in the spinal Dorsal Root Entry Zone (DREZ) Surgery in the Dorsal Root Entry Zone (DREZ) of the spinal cord was introduced in 1972 by Sindou for the treatment of chronic pain. This technique also induced important hypotonia and was therefore used by the author for cases of severe focalized spasticity, not only for lower limbs but also for upper limbs hyperspasticity (11). The purpose of the microsurgical DREZotomy (MDT)technique is to preferentially interrupt both small (nociceptive) and large (myotatic) caliber, which are the tonigenic fibers of the dorsal roots, respectively situated laterally and in the middle of the entry zone. This surgical lesion is partially able, if not totally, to spare the medial large caliber fibers that project

Neurosurgical Management of Spasticity

1173

to the dorsal column of the cord. MDT technique is presented in more details in a separate chapter of this book, in the chapter “Neurosurgical Management of Neurosurgery for neuropathic pain”. Briefly, for patients with spastic paraplegia, the L2-S1 spinal segments are approached through a T11L2 laminectomy, whereas for a spastic upper limb, a C4-C7 hemilaminectomy with conservation of the spinous processes is sufficient to reach the C5-T1 segments. Identification of the cord levels related to the undesirable spastic mechanisms is achieved by studying the muscle responses to bipolar electrical stimulation of the anterior and/or posterior roots. The motor threshold for stimulation of anterior roots is one-third that of the threshold for posterior roots. Then, the lateral aspect of the DREZ is exposed so that the microsurgical lesions can be performed, 3mm in depth and at 35 to 45 degree angles in the ventro-lateral aspect of the sulcus. Bipolar coagulation is performed ventrolaterally at the entrance of the dorsal rootlets into the dorsolateral sulcus, along all the spinal cord segments selected for surgery and corresponding to the metameric levels of innervation of the disabled spastic muscles targeted. Each coagulation is performed under direct vision for 1 to 3 seconds at low intensity with the bipolar generator (11,13). MDT is indicated 1) in paraplegic patients, especially when they are bedridden as a result of disabling flexion spasms and 2) in hemiplegic patients with irreducible and/or painful hyperspasticity in the upper limb. MDT can also be applied at the S2-S3 levels to treat neurogenic bladder with uninhibited detrusor contractions resulting in voiding around a vesical catheter. Permanent neurological complications due to long-tract impairments may be observed after MDT. Ataxia with tactile and arthrokinesthetic hypoesthesia in the ipsilateral lower limb can be observed when the DREZ-lesion is performed too medially and impairs the dorsal column tract. Motor disturbances in the ipsilateral lower limb may happen in case of lesion of the pyramidal tract by a too lateral lesion.

Surgery in the spinal cord In 1951, Bischof described the longitudinal myelotomy technique for spasticity treatment. His aim was to interrupt the spinal reflex arc between the ventral and dorsal horns by a vertical coronal incision performed laterally from one side of the spinal cord to the other side from L1 to S1 metameric levels for cases with total paraplegia. Pourpre modified Bischof’s myelotomy technique to avoid complete interruption of cortico-spinal fibres. Through a T9 to L1 laminectomy, the procedure was performed via a posterior longitudinal sagital incision of the spinal cord prior to performing a cruciform myelotomy by transversal incision on either side using a stylet with a right angled extremity. The purpose of this surgical lesion was to interrupt the spinal reflex arc between the ventral and dorsal horns without sectioning the fibers connecting the pyramidal tract to the motoneurones of the ventral horn. Longitudinal myelotomy is indicated (only) for spastic paraplegias with flexion spasms, when the patient has no residual useful motor function and no bladder or sexual controls (8,11,13).

1174 Functional Neurosurgery

Conclusions A neurosurgical program for treating disabling spasticity resistant to physical and medical therapy has to be tailored according to the individual problems of each patient (Fig2). Intrathecal Baclofen infusion is indicated for para- or tetraplegic patients with severe and diffuse spasticity in the lower limbs. Because of its reversivility, this method has to be considered prior to considering an ablative procedure. Neuro-ablative techniques are indicated for severe focalized spasticity in the limbs of paraplegic, tetraplegic or hemiplegic patients. Neurotomies are considered when spasticity is localized to a group of muscles innervated by a small number of peripheral nerves. When spasticity affects an entire limb, DREZotomy is preferred. Several types of neuroablative procedures can be combined for the treatment of one patient. Whatever the situation and the etiology may be, orthopedic surgery must be considered only after spasticity has been reduced by physical and pharmacological treatments first and, when necessary, by neurosurgical procedures. When dealing with surgery for spasticity, the surgeon needs to work within the frame of a multidisciplinary team (13).

Neurosurgical Management of Spasticity

1175

Fig. 2 Guidelines for treating disabling hyperspasticity, in paraplegic (top), and hemiplegic (middle and bottom) patients.

REFERENCES 1. Abbott R, Forem SL, Johann M (1989) Selective posterior rhizotomy for the treatment of spasticity. Child's Nerv. Syst 5:337-346. 2. Decq P, Mertens P and coll.(2003) Neurosurgery for spasticity Masson, Paris, vol 2-3 : 133-146 (in french) 3. Fasano VA, Barolat-Romana G, Ivaldi A, Squazzi A (1976) La radicotomie postérieure fonctionnelle dans le traitement de la spasticité cérébrale. Neurochirurgie 22 :23-34 4. Foerster O (1913) On the indications and results of the excision of posterior spinal nerve roots in men. Surg. Gynecol. Obset. 16 :463-474 5. Gros C (1979) Spasticity - Clinical classification and surgical treatment. In: Krayenbühl (ed): « Advances and Technical Standards in Neurosurgery », 1979, vol 6, Springer, Wien, New York, pp 55-97. 6. Maarrawi J, Mertens P, Luaute J, Vial C, Chardonnet N, Cosson M, Sindou M (2006) .Long-term functional results of selective peripheral neurotomy for the treatment of spastic upper limb: prospective study in 31 patients. J Neurosurg 104:215-25 7. Mertens P, Sindou M (1991) Selective peripheral neurotomies for the treatment of spasticity. In : Sindou M, Abbott R and Keravel Y (eds) « Neurosurgery for Spasticity : a multidisciplinary approach ». Springer-Verlag, Wien-New York, pp 119-132. 8. Mertens P, Sindou M (2008) Surgical management of spasticity. In: Barnes MP, Johnson GR (eds) Clinical Management of Spasticity. Cambridge University Press, Cambridge, pp 239-265 9. Peacock WJ, Arens LJ (1982) Selective posterior rhizotomy for the relief of spasticity in cerebral palsy. S. Afr. Med. J. 62 :119-124 10. Penn RD, Kroin JS (1985) Continuous intrathecal baclofen for severe spasticity. Lancet 20 125-127. 11. Sindou M. Neurosurgical Management of Disabling Spasticity. In: Spetzler RF (ed.) Operative Techniques in Neurosurgery. Elsevier, Philadelphia, vol 7, pp95-174. 12. Sindou M, Mertens P (1988) Selective neurotomy of the tibial nerve for treatment of the spastic foot. Neurosurgery 23:738-744. 13. Sindou M, Abbott R, Keravel Y (1991) « Neurosurgery for Spasticity: A multidisciplinary approach », Springer-Verlag, Wien, New York. 320 pp. 14. Stoffel A (1912) The treatment of spastic contractures Am. J. Orthop. Surg. 10 :611-644

1176

Surgical Management of Epilepsy PRAVEEN R. BAIMEEDI, U˘GUR TÜ R E Department of Neurosurgery, Yeditepe University School of Medicine, Istanbul, Turkey Key words: complex intracranial aneurysm, “multiclip” method, intraoperative doppler, inrtraoperative neuro endoscopy

INTRODUCTION Epilepsy has a bimodal age distribution, with peaks at both extremes of age. The median incidence of epilepsy in general population studies was noticed to be around 47.4 per 100,000 populations. Developing countries have a slightly higher incidence (68.7 per 100,000) than industrialized countries (43.4 per 100,000) (14). Surgical management of epilepsy is considered in refractory epilepsy and approximately 30-40% of patients with epilepsy have refractory epilepsy (24). The philosophy and approach towards patients with epilepsy has changed significantly in recent times. There is a trend towards more early noninvasive diagnostic workup and early surgery with consequent better outcomes (4, 13, 27, 28). Most studies, though non randomized show that about nearly 2/3rds of properly selected patients have their seizures controlled with surgery. With better seizure control, patients have a better quality of life and can integrate better in the society (13, 16). Hence, epilepsy should be investigated in a logical fashion, and those candidates considered ideal for surgery, should be operated early in the course of the disease for better long term outcomes (8, 13, 16, 28, 30). Different definitions are used for medically intractable epilepsy by various centers, but the common theme among them is failure of antiepileptic drugs (AED's) to control epilepsy both in terms of number of seizures and also the duration. The most commonly used definitions are listed in the Table 1. There is lack of uniform consensus among epileptologists, as is evident by so many different definitions (4, 15). The goal should be to identify the surgical candidates early, for better long term results.

PREOPERATIVE WORKUP Epilepsy should be managed by a multidisciplinary team, consisting of epileptologist, neurosurgeon, neuroradiologist, neuroanesthesiologist, nuclear medicine specialist, neuropsychologists, speech therapist and social workers. Ideal management consists of a proper understanding of seizure semiology and sequential investigation starting at basic non-invasive testing and proceeding to invasive testing in only those situations, where the noninvasive testing is inconclusive (23). The summary of the appropriate diagnostic workup is shown in Table 2.

Surgical Management of Epilepsy

1177

Table 1 Published criteria used for determining intractable epilepsy

Table 2 Diagnostic Workup

SURGICAL MANAGEMENT After extensive diagnostic workup, most cases can be categorized into either temporal or extra-temporal epilepsy. Various surgical managements are presented in Table 3.

I. Temporal Lobe Epilepsy: It is a wide spectrum of disease. As more experience with surgical management of epilepsy was gained it was observed that there are three different varieties of temporal lobe epilepsy (24, 45). These are mediobasal temporal lobe epilepsy (MTLE), neocortical temporal lobe epilepsy and lesional temporal lobe epilepsy. Sometimes, the same patient may have mediobasal temporal epilepsy in concordance with either lesional epilepsy or temporal neocortical epilepsy. Sometimes all three

1178 Functional Neurosurgery Table 3 Surgical management options

situations are seen in the same patient. In these cases, preoperative studies aimed at understanding the situation well leads to reduced failure rates. With neocortical epilepsy and lesional epilepsy without hippocampal sclerosis, resection of the lesion and or the epileptogenic zone leads to good outcomes.

A. Mediobasal Temporal Lobe Epilepsy (MTLE): It is a spectrum of disease which often leads to refractory seizures. Investigations done appropriately as discussed earlier in the chapter will make it possible to diagnose MTLE. In MR imaging technique, it is important to remember to acquire imaging in temporal angulation (Figure 1) (36, 35). Also FLAIR and T2W sequences can pick up early signal changes in the hippocampus. Sometimes the situation is complicated by bilateral disease and also other neocortical lesions. In these cases more invasive testing is done, to determine the side of the lesion and also, if neocortical resection is necessary along with amygdalohippocampectomy for control of seizures in this situation (44). There are several techniques described to manage MTLE. One common theme to all of them is

Fig. 1 Pre operative MRI T1W axial (left) and T2W coronal (right) images showing classic features of left hippocampal sclerosis (arrows).

Surgical Management of Epilepsy

1179

amygdalohippocampectomy. The most commonly practiced technique is anterior temporal lobectomy, where the lateral temporal neocortex is resected to reach the mediobasal structures. In the dominant hemisphere the most anterior 3.5 cm are resected and in the nondominant hemisphere anterior 4-5 cm are resected (5, 19). We are going to discuss transsylvian selective amygdalohippocampectomy technique, which was initially developed by Yas¸ argil (41, 46, 47). The other techniques of doing amygdalohippocampectomy include subtemporal approaches (5, 16, 12, 19), and through the middle temporal gyrus approach (18, 20).

Transsylvian Selective Amygdalohippocampectomy: Patient is positioned supine with the head turned to the opposite side by 30 degrees. Patients head is fixed in a Mayfield skull clamp and vertex down, so that the malar eminence is the highest point. This allows for gravity aided opening of the basal areas. A pterional skin incision is given behind the hairline. Interfacial dissection is done to save the frontal branch of the facial nerve. Next the temporal muscle is reflected anteroinferiorly towards the sphenoid ridge. A burr hole is placed below the superior temporal line, at the posterior aspect of the exposed bone. The dura is then separated from the inner table by using a flexible dural dissector. Then using a craniotome a pterional free bone flap is elevated, which is flush with the floor of the anterior cranial fossa. The lateral sphenoid wing and the projections on the orbital roof are flattened using a high speed drill prior to dural opening. Dura is then opened in semicircular fashion around the sylvian fissure. Care should be taken while opening over the fissure to look for draining sylvian veins. The dura is then tented snugly over the sphenoid wing. At this point attention is aimed at achieving cerebral relaxation by draining CSF. Initially march down subfrontally and with suction shaft gently retract the lateral frontoorbital gyrus and open the arachnoid over the chiasmatic and carotid cisterns. This maneuver achieves significant brain relaxation. Then divert attention towards opening the sylvian fissure. The proximal part of the sylvian fissure is opened medially or laterally to the superficial sylvian veins, depending on the variations in the venous anatomy. Dissection continues to expose the M2 segment and the bifurcation of the middle cerebral artery, then following the M1 segment down to the ICA bifurcation. The lateral branches of the ICA (PCoA, AChA and striocapsular arteries), the cortical branches of the M1 segment (temporopolar, anterior, and middle temporal arteries) and lenticulostriate arteries and their variations are identified. The limen insula and the inferior trunk of the M2 segment are observed. At this stage, intraoperative EEG is done with both surface grids over the temporal surface and also depth electrodes in the hippocampus (Figure 2). The resection of the piriform cortex just anterolateral to the M1 segment and anteroinferior to the limen insula enables the surgeon to reach the amygdala (Figure 3). The superior part of the amygdala is identified a few millimeters under the incision line by its grayish color. The amygdala must first be removed piecemeal with both a tumor forceps to gain histopathological examination and gentle suction. During the removal of amygdala, the temporal horn of the lateral ventricle must be entered, allowing a clearer orientation of the hippocampus, choroidal fissure and the extent of the amygdala. At this

1180 Functional Neurosurgery

Fig. 2 Lateral (left) and inferior (right) views of the left cerebral hemisphere model depicting the location of placement of intra operative monitoring strips after craniotomy. cs = collateral sulcus, fg = fusiform gyrus, i = insula, phg = parahippocampal gyrus, sf = sylvian fissure, tp = temporal pole, T1 = superior temporal gyrus, T2 = middle temporal gyrus, T3 = inferior temporal gyrus t1 = superior temporal sulcus, t2 = inferior temporal sulcus, u = uncus.

Fig. 3 Mediobasal structures in a left cerebral hemisphere specimen, arrow showing the site of entry into the amygdala. ahg = anterior Heschl gyrus, fi = fimbria, h = hippocampus, ips = inferior peri insular sulcus, li = limen insula, pc = piriform cortex, phg = posterior Heschl gyrus, ppl = polar planum, s = subiculum, tp = temporal pole, tpl = temporal planum.

stage of the operation, it is of utmost importance that the optic tract is clearly identified. Care must be taken not to resect the most medial parts of the amygdala lying superolateral

Surgical Management of Epilepsy

1181

to the optic tract and projecting to the claustrum, putamen, and globus pallidus. After these sections of the amygdala are taken out, the rest of the piriform cortex and the anterior part of the parahippocampal gyrus are removed subpially. The transparent curtain of pial and arachnoidal membranes near the lateral part of the carotid cistern and the anterior part of the crural and ambient cisterns may be identified readily anteroinferiorly, after subpial resection. After the pia is opened, important anatomical details can be identified, such as the entrance of the AChA to the choroidal fissure along the crural cistern and the optic tract and the basal vein of Rosenthal, which lie medial to the AChA, the cerebral peduncle, the P2 segment of the posterior cerebral artery, and the oculomotor nerve. The tela choroidea can be isolated by displacing the choroid plexus medially over the choroidal fissure. Fine forceps are used to reflect the choroid plexus medially and open the tela choroidea between the choroid plexus and the tenia fimbria. At this point, the hippocampal and uncal branches of the AChA must be coagulated and divided. However, great care must be taken not to injure the main stem of the AChA. As the choroidal fissure along the tenia fimbria is opened, the medial part of the parahippocampal gyrus (subiculum) within the lateral wing of the transverse fissure can be identified. They should be isolated from the arachnoidal membranes and meticulously preserved. The hippocampus is supplied by the hippocampal arteries, which lie beneath the veins described above and enter the hippocampus most often by penetrating the hippocampal sulcus. They usually originate from the P2 segment just proximal to the P2-P3 junction, or from the P3 segment itself, or from branches of the P3 segment and occasionally from the AChA. At this stage of the operation, the hippocampal arteries are coagulated and divided. The head of the hippocampus-parahippocampal gyrus is transected at the level of the proximal portion of the fimbria and en bloc resection is done. The more posterior portions of the hippocampus and parahippocampal gyrus are removed with suction or the ultrasonic aspirator. We prefer this technique instead of en bloc resection of the whole hippocampus, parahippocampal gyrus because it preserves the anterior temporal stem. The posterior limit of the resection of the hippocampal tail is just at the level of the posterior rim of the cerebral peduncle. The resection is carried out inferolaterally through the posterior part of the hippocampus-parahippocampal gyrus, in the direction of the collateral sulcus and tentorial edge. After careful hemostasis is achieved in the resection cavity post resection surface EEG is repeated to confirm no neo-cortical activity. Most studies point to failure of the surgery, to incompleteness of hippocampal resection (24, 43). Hence, use techniques such as intraoperative ultrasound and intraoperative EEG to help with successful outcomes. The dura is closed with a running suture and the bone flap is replaced in the normal fashion (Figure 4). Apart from complications of craniotomy, important complications which are possible to selective amygdalohippocampectomy are visual field defects and cognitive impairment, the latter more common in dominant hemisphere. To avoid these injuries, we open the sylvian fissure and enter directly to the amygdala without cutting the limen insula region and hence, we are able to preserve white matter tracts of the anterior temporal stem (Figure 5).

1182 Functional Neurosurgery

Fig. 4 Post operative images, MRI T2W axial (left), T1W coronal (middle) and sagittal (right) images depicting the extent of resection of left mediobasal structures.

Fig. 5 Post operative DTI images showing intact white fibers of the anterior temporal stem. Uncinate fasciculus (green), anterior commissure (yellow), posterior thalamic peduncle (blue), frontooccipital fasciculus (pink).

II. Other Surgical Strategies for Refractory Extra-temporal epilepsy: A. Epilepsy surgery in focal malformations of cortical development. B. Refractory epilepsy in the setting of MRI confirmed lesions. C. Non lesional refractory epilepsy. D. Hemispherectomy. E. Multiple subpial transsection. F. Miscellaneous procedures.

A. Epilepsy Surgery in Focal Malformations of Cortical development This is a distinct cohort of patient population, characterized by abnormalities in the cortical development, with associated abnormalities of cortical organization, dysmorphic neurons, large neurons and also balloon cells. This entity is more often seen in children (24, 17). Previously, included under "Cryptogenic" epilepsy, but with newer imaging modalities the subtle alterations are detected with greater frequency (17). This entity if leads to refractory epilepsy respond to surgery, but not as well as the MTLE group. This

Surgical Management of Epilepsy

1183

is a subset population, where invasive monitoring in the form of subdural grids and strips, and implanted electrodes are more often needed. The basic aim of surgery is complete excision of the abnormal area along with surrounding electrically active tissue, with a goal to disconnect the epileptogenic zone completely. After appropriate preoperative localization, a wide craniotomy around the MRI identified lesion is preferred. It has been the experience of most epilepsy centers that the area of abnormality extends well beyond the area seen in preoperative imaging (24, 17). Also, it is important to perform intraoperative recording and resect the surrounding electrically active tissue. In situations where the malformation is over the eloquent cortex, it is important to perform surgery with intraoperative stimulation or awake craniotomy or both. Identifying true distinct margin is difficult in these cases; hence, intraoperative ECoG is needed in these cases for improving outcomes.

B. Refractory epilepsy in the setting of MRI confirmed lesions: These subset patients may have varied pathology. The common variants are shown in the Table 4. Because of the large variation in the possible etiology, it is imperative that in refractory epilepsy in this subset, investigations should start with noninvasive tests which are shown in Table 2, and if there is concordance in findings of imaging and the noninvasive tests, then surgery may be performed (38). But if the tests are inconclusive, then invasive testing is done. Patients with a MRI lesion with concordant EEG findings have almost 95% probability of seizure control (30, 24, 45). The aim of surgery is complete resection of abnormal lesion and occasionally surrounding area if electrically found to be active during surgery and after resection of the obvious lesion. If prior invasive testing is needed, then a wide craniotomy should be done, so that not only the Table 4 Various causes of lesional epilepsy.

1184 Functional Neurosurgery lesion, but also the surrounding cortical areas connected by association fibers to the area of the lesion need to be exposed. After resection of the lesion, intraoperative ECoG is done, if indicated by preoperative invasive and noninvasive testing, to confirm electrical silence in the surrounding area this is usually not needed in vascular and neoplastic conditions, but is a useful technique in gliosis and encephalomalacia group. There is a linear relationship in most situations for completeness of resection and good outcome (24, 45), hence, use additional techniques like intraoperative ultrasound and maybe intra operative imaging if available.

C. Non lesional Refractory epilepsy: Surgical outcomes in this category of patients in terms of seizure control are poor. Before a case of refractory epilepsy is considered as non lesional, we need to confirm that appropriate imaging technique has been used. The criteria for epilepsy surgery imaging are shown in Table 5. If after appropriately performed imaging, the situation is considered non lesional, then these patients are usually subject to more invasive techniques (44, 45). The goal in these investigations is to proceed from least invasive to more invasive tests. Initially every effort should be made from history and EEG to lateralize. Subsequently inter ictal PET and MEG may help to identify area of EEG abnormality and functional abnormality (2, 42). If there is a concordance then surgery aims at resecting this area. If there is discordance, current evidence points to resecting both area of EEG abnormality and also functional abnormality where feasible (7). If lateralization is not feasible with noninvasive tests, then subdural strips are an ideal start to lateralize and then place subdural grids to identify epileptogenic zone, and then proceed with surgical removal of identified epileptogenic zone. These situations are better handled in high volume epilepsy centers. Outcome in this cohort of patients is usually not as good as the other surgical groups. Table 5 MRI Protocols for Epilepsy (35, 36, 38, 40)

D. Hemispherectomy or Hemispherotomy: There is a small subset of patients in whom there is a hemispheric syndrome, with patients having significant neurological deficits. These patients if appropriately investigated maybe ideal candidates for hemispherectomy or hemispherotomy. Common syndromes associated with hemispheric syndromes that might benefit from hemispherectomy or hemispherotomy are porencephaly, hemimegalencephaly, extensive unilateral cortical dysplasia, Sturge-Weber syndrome and Rasmussen syndrome (22, 24, 25, 31). The patients who need this procedure are very young people. In children less than

Surgical Management of Epilepsy

1185

2 years of age, clinical semiology does not help lateralize or localize (23, 24, 45). Hence, imaging techniques aimed at studying structural anatomy and functional imaging with neuropsychological development, help in these candidates. The aim of surgery is hemispheric disconnection, either anatomic or physiologic. Conventional techniques relied on extensive removal of cortical, subcortical structures and white matter pathways. Novel techniques aim at doing physiologic disconnection with equally good results and reduced complications. Since, this age group does not tolerate blood loss well specific consideration to coagulation parameters should be given. Any coagulopathy should be ideally corrected before surgery. Also fresh blood products should be standby during procedure and for post procedure resuscitation. Basic aim of the novel procedures is via a craniotomy, the sylvian fissure is opened and dissection is done to expose the insula. After the anterior, superior and inferior periinsular sulci have been well delineated, amygdalohippocampectomy is done first. Next dissection is done along the periinsular sulcus to expose the lateral ventricle completely. Initially the atrium, then the body and finally the frontal horn is exposed. Callosal disconnection is then done from within the ventricles (24, 25, 22, 31). This procedure leaves the hemispheric anatomic structures, basically intact but functionally disconnects the hemisphere. This has less chance of delayed hemorrhage, superficial hemosiderosis and hydrocephalus, all possible complications in anatomic hemispherectomy.

E. Multiple Subpial Transsection (MST): MST is a surgical procedure which is reserved in those desperate situations where there is a refractory epilepsy situation, but structural and functional localization of the epileptic zone is in eloquent cortex, hence, the surgical techniques discussed earlier in this chapter cannot be used to treat this situation (22, 26). MST is based on the understanding of anatomy and physiology of cortical organization and mechanism of epileptic spread. The basic rationale of the procedure is based on firstly, the vertical columnar organization of the cortex, thalamocortical fibers and the projection fibers from the cortex are oriented vertically, secondly, synchrony of seizures is based on side to side interactions among dendrites in superficial cortical laminae, thirdly, the critical mass of cortical tissue with side to side interactions necessary to generate a epileptiform discharge is noted in experimental studies to be about 5 mm, fourthly, the most common pattern of spread of epileptiform activity is locally and laterally, and lastly the blood supply to the cortex is also oriented vertically. Based on the aforementioned logic, MST procedure involves causing multiple transsections with a goal of achieving lateral disconnection preventing horizontal transmission of electrical activity, but still preserving the functional vertical fibers.

F. Miscellaneous Procedures: Two other surgical procedures deserve mention. Corpus callosotomy is used a surgical procedure in refractory Lennox-Gastaut syndrome, with drop attacks (48). This procedure aims at callosal fiber disconnection. Vagus nerve stimulation (37) is now being used with increasing frequency in failed surgical candidates, when their disease has been refractory to conventional surgical treatment options. This procedure involves in placement of a bipolar lead, around the left vagus nerve, and this bipolar lead is stimulated using a pulse generator implanted below the clavicle. The proposed

1186 Functional Neurosurgery mechanism as to how it works is that vagal stimulation causes polysynaptic activation, causing its anti-seizure effect. The median reduction is seizure frequency with this procedure is around 45%. Gamma knife radiosurgery is being recently explored in the management of both lesional and nonlesional epilepsy in some selected situations (21). It is still in its nascent phase, at this current time, studies are underway to determine indications, appropriate dose, and appropriate targets.

OUTCOMES Surgical management of epilepsy, in well selected cases has good outcomes, in terms of seizure control and improvement in quality of life, and these candidates are able to better integrate in Society (8, 16, 13, 28, 30, 41). Results are much better when there is a concordance in the findings on studies aimed at structural evaluation, with studies aimed at functional evaluation. Outcomes are measured using the criteria recommended by International League against epilepsy (Table 6). Long term seizure control rates are shown in Table 7. Table 6 Outcome criteria based on recommendations by International League Against Epilepsy

Table 7 Outcomes in Epilepsy (16, 20, 24, 28)

REFERENCES 1. Arts WF, Geerts AT, Brouwer OF, Boudewyn Peters AC, Stroink H, van Donselaar CA: The early prognosis of epilepsy in childhood: the prediction of a poor outcome. The Dutch study of epilepsy in childhood. Epilepsia 40: 726-734, 1999. 2. Assaf BA, Karkar KM, Laxer KD, Garcia PA, Austin EJ, Barbaro NM, Aminoff MJ: Magnetoencephalography source localization and surgical outcome in temporal lobe epilepsy. Clin Neurophysiol 115: 2066–2076, 2004. 3. Berg A, Kelly M. Defining Intractability: Comparisons among Published Definitions. Epilepsia 47: 431-436, 2006. 4. Berg AT, Shinnar S, Levy SR, Testa FM, Smith-Rapaport S, Beckerman B: Early development of intractable epilepsy in children: a prospective study, Neurology 56: 1445-

Surgical Management of Epilepsy

1187

1452, 2001. 5. Burchiel C, Christiano JA: Review of selective amygdalohippocampectomy techniques, in Miller J, Silbergeld D (eds): Epilepsy Surgery: Principles and Controversies. New York: Taylor & Francis Group, 2006, pp 451–464. 6. Camfield P, Camfield C. Nova Scotia pediatric epilepsy study. In: Jallon P, Berg A, Dulac O, et al., eds. Prognosis of Epilepsies. Montrouge, France: John Libbey, Eurotext, 2003, pp 113–126. 7. Carne RP, O'Brien TJ, Kilpatrick CJ, MacGregor LR, Hicks RJ, Murphy MA, Bowden SC, Kaye AH, Cook MJ: MRI-negative PET-positive temporal lobe epilepsy: A distinct surgically remediable syndrome. Brain 127: 2276–2285, 2004. 8. Dlugos DJ, Sammel MD, Strom BL, Farrar JT: Response to first drug trial predicts outcome in childhood temporal lobe epilepsy, Neurology 57: 2259-2264, 2001. 9. Duvernoy H: The Human Hippocampus, 3rd Ed. Berlin, Springer-Verlag, 2005. 10. Erdem A, Yas¸argil MG, Roth P. Microsurgical anatomy of the hippocampal arteries. J Neurosurg 79: 256-265, 1993. 11. Gloor P. The Temporal Lobe and Limbic System. New York, Oxford University Press, 1997. 12. Hori T, Tabuchi S, Kurosaki M, Kondo S, Takenobu A, Watanabe T: Subtemporal amygdalohippocampectomy for treating medically intractable temporal lobe epilepsy. Neurosurgery 33: 50-57, 1993. 13. Khan N, Wieser HG. Psychosocial outcome of patients with amygdalohippocampectomy. J Epilepsy 5: 128-134, 1992. 14. Kotsopoulos IA, van Merode T, Kessels FG, de Krom MC, Knottnerus JA. Systematic Review and Meta-analysis of Incidence Studies of Epilepsy and Unprovoked Seizures, Epilepsia 43 (11): 1402-1409. 15. Kwan P, Brody M. Drug treatment of epilepsy: when does it fail and how to optimize its use. CNS Spectrums 9: 110–119, 2004. 16. Lindsay J, Ounsted C, Richards P. Long term outcome in children with temporal lobe seizures. I: Social outcome and childhood factors. Dev Med Child Neurol 21: 285298, 1979. 17. Lüders H, Schuele SU: Epilepsy surgery in patients with malformations of cortical development. Curr Opin Neurol 19: 169–174, 2006. 18. Niemeyer P, Bello H: Amygdalo-hippocampectomy for temporal lobe epilepsy— microsurgical technique. Excerpta Medica 293: 20, 1973. 19. Olivier A: Transcortical selective amygdalohippocampectomy in temporal lobe epilepsy. Can J Neurol Sci 27 (1 Suppl): S68–S76, 2000. 20. Paglioli E, Palmini A, Portuguez M, Paglioli E, Azambuja N, da Costa JC, da Silva Filho HF, Martinez JV, Hoeffel JR. Seizure and memory outcome following temporal lobe surgery: Selective compared with nonselective approaches for hippocampal sclerosis. J Neurosurg 104: 70-78, 2006. 21. Quigg M, Barbaro NM. Stereotactic radiosurgery for treatment of epilepsy. Arch Neurol 65: 177-183, 2008. 22. Roper SN: Surgical treatment of extratemporal epilepsies. Epilepsia 50 (Suppl.8): 69-74, 2009. 23. Rosenow F, Lüders H: Presurgical evaluation of epilepsy. Brain 124: 1683–1700, 2001. 24. Schramm J, Kral T, Clusmann H: The Surgery of Epilepsy. Neurosurgery 62 (SHC Suppl 2): SHC 463-SHC 481, 2008. 25. Schramm J, Kral T, Clusmann H: Transsylvian keyhole functional hemispherectomy. Neurosurgery 49: 891–901, 2001. 26. Spencer SS, Schramm J, Wyler A, O'Connor M, Orbach D, Krauss G, Sperling M, Devinsky O, Elger C, Lesser R, Mulligan L, Westerveld M: Multiple subpial transection

1188 Functional Neurosurgery

27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37.

38. 39. 40. 41. 42. 43. 44. 45. 46.

for intractable partial epilepsy: An international meta-analysis. Epilepsia 43: 141–145, 2002. Spencer SS: When should temporal lobe epilepsy be treated surgically? Lancet Neurol 1: 375-382, 2002 Stavem K, Bjørnaes H, Langmoen IA: Long-term seizures and quality of life after epilepsy surgery compared with matched controls. Neurosurgery 62: 326-335, 2008. Sveinbjornsdottir S, Duncan JS: Parietal and occipital lobe epilepsy: A review. Epilepsia 34: 493–521, 1993. Téllez-Zenteno JF, Dhar R, Wiebe S: Long-term seizure outcomes following epilepsy surgery: a systematic review and meta-analysis. Brain 128: 1188-1198, 2005. Tinuper P, Andermann F, Villemure JG, Rasmussen TB, Quesney LF: Functional hemispherectomy for treatment of epilepsy associated with hemiplegia: Rationale, indications, results, and comparison with callosotomy. Ann Neurol 24: 27–34, 1988. Türe U, Kaya AH, Bingöl CA: Transsylvian Selective Amygdalohippocampectomy, Pediatric Epilepsy Surgery, Cataltepe O, Jallo GI (eds). Thieme , 2010-In Press. Türe U, Yas¸argil DCH, Al-Mefty O, Yas¸argil MG: Topographic anatomy of the insular region. J Neurosurg 90:720-733, 1999. Türe U, Yas¸argil MG, Friedman A, Al-Mefty O. Fiber dissection technique. Neurosurgery 47: 417-427, 2000. Urbach H, Hattingen J, von Oertzen J, Luyken C, Clusmann H, Kral T, Kurthen M, Schramm J, Blümcke I, Schild HH: MR imaging in the presurgical workup of patients with drug-resistant epilepsy. AJNR 25: 919–926, 2004 Von Oertzen J, Urbach H, Jungbluth S, Kurthen M, Reuber M, Fernández G, Elger CE: Standard magnetic resonance imaging is inadequate for patients with refractory focal epilepsy. J Neurol Neurosurg Psychiatry 73: 643–647, 2002. Vonck K, Thadani V, Gilbert K, Dedeurwaerdere S, De Groote L, De Herdt V, Goossens L, Gossiaux F, Achten E, Thiery E, Vingerhoets G, Van Roost D, Caemaert J, De Reuck J, Roberts D, Williamson P, Boon P: Vagus nerve stimulation for refractory epilepsy: A transatlantic experience. J Clin Neurophysiol 21: 283–289, 2004. Wellmer J, von Oertzen J, Schaller C, Urbach H, König R, Widman G, Van Roost D, Elger CE: Digital photography and 3D MRI-based multimodal imaging for individualized planning of resective neocortical epilepsy surgery. Epilepsia 43: 1543–1550, 2002. Wen HT, Rhoton AL Jr, Marino R Jr. Gray matter overlying anterior basal temporal sulci as an intraoperative landmark for locating the temporal horn in amygdalohippocampectomies. Neurosurgery 59 (Suppl 2): ONS221-7, 2006. Widjaja E, Raybaud C. Advances in neuroimaging in patients with epilepsy. Neurosurg Focus 25: E3, 2008. Wieser HG, Yasargil MG: Selective amygdalohippocampectomy as a surgical treatment of mesiobasal limbic epilepsy. Surg Neurol 17: 445–457, 1982. Willmann O, Wennberg R, May T, Woermann FG, Pohlmann-Eden B: The contribution of 18F-FDG PET in preoperative epilepsy surgery evaluation for patients with temporal lobe epilepsy. A meta-analysis. Seizure 16: 509–520, 2007 Wyler AR, Hermann BP, Somes G: Extent of medial temporal resection on outcome from anterior temporal lobectomy: A randomized prospective study. Neurosurgery 37: 982–991, 1995. Wyler AR, Ojemann GA, Lettich E, Ward AA Jr: Subdural strip electrodes for localizing epileptogenic foci. J Neurosurg 60: 1195–1200, 1984. Wyllie E. Surgical treatment of epilepsy in pediatric patients. Can J Neurol Sci 27: 106-110, 2000. Yas¸argil MG, Krayenbühl N, Roth P, Hsu SPC, Yas¸argil DCH: The selective amygdalohippocampectomy for intractable temporal limbic seizures, Historical vignette.

Surgical Management of Epilepsy

1189

J Neurosurg 2009 Jul 3. [Epub ahead of print]. 47. Yas¸ argil MG, Teddy PJ, Roth P. Selective amygdalohippocampectomy: Operative anatomy and Surgical technique. In: Symon L, Brihaye J, Guidetti B, et al, eds. Advances and Technical Standards in Neurosurgery. Vienna, Springer, 1985:93-123. 48. You SJ, Lee JK, Ko TS: Epilepsy surgery in a patient with Lennox-Gastaut syndrome and cortical dysplasia. Brain Dev 29: 167–170, 2007.

1190

Surgical Treatment of Epilepsy BADIH ADADA, MD. Department of Neurosurgery, Cleveland Clinic Florida 2950 Cleveland Clinic Blvd, Weston Florida 33331 USA Key words: Epilepsy, surgery, Amygdalohippocampectomy

1. Introduction: Epilepsy is a common neurological condition affecting 0.5-1% of the population. Despite the advances in the medical management of epilepsy 25-35% of patients have poor control of their seizures or have unacceptable side effects from the medication. Poor seizure control in patients suffering from epilepsy not only causes physical injuries and social disability but also leads to gradual cognitive decline. If left uncontrolled, recurrent seizures have a deleterious effect on cognitive development, and in an animal model it has been proven that chronic recurrent seizures are associated with neuronal death. An increased incidence of sudden death in patients suffering from recurrent seizures has also been shown. More over a third of patients suffering from recurrent seizures from a temporal focus will eventually develop a second epileptic focus if the seizures are not well controlled through a phenomenon known as kindling. Surgical treatment of epilepsy is to be considered in patients with intractable seizures. The definition of intractable seizures is somewhat variable from author to author. Intractability is most commonly defined as inadequate seizure control after one year of trial of two first line anti-epileptic drugs (AED) as monotherapy at maximally tolerated doses, or adequate seizure control with unacceptable drug-related side effects.

2. Preoperative workup: The preoperative workup of patients suffering from epilepsy has two main objectives: First to determine the origin of the seizures and second to map the surrounding era and determine its function. Several tools are available for these purposes: • History: Obtaining a good history of the seizures, including the age of their onset the medications that have been tried, the aura preceding them, the detailed description and progression of the seizures and the post-ictal state of the patient is a very important part of the patient’s work up. • Interictal EEG: Depending on the type of epilepsy some studies have shown that interictal EEG is abnormal in 35-40% of patients. Interictal EEG abnormalities were more frequent in patients with partial seizures. The diagnostic yield of interictal EEG increased to 60% if the studies were multiple. • MRI imaging is a cornerstone during the investigation of patients with intractable

Surgical Treatment of Epilepsy

1191

Fig. 1 Coronal MRI in FLAIR sequence showing a left mesial temporal sclerosis.

seizures. Several pathologies responsible for seizures can be visualized: Mesial temporal sclerosis is the most common lesion associated with complex partial seizures. What is primarily seen on MRI in these patients is a small atrophic hippocampus, that is hyper intense on T2 or FLAIR images, with loss of the internal architecture of the hippocampus (Figure 1). The secondary signs associated with mesial temporal sclerosis are atrophy of the amygdala, fornix and mamillary body on the affected side; dilatation of the temporal horn on the ipsilateral side, increased T2 signal changes in the white mater of the temporal pole with loss of grey-white mater differentiation. Developmental abnormalities are another group of pathologies identified on MRI imaging of patients with seizures. Focal cortical dysplasia, presenting as an expanded gyrus with abnormally oriented sulci and thickened cortex is most often seen in the temporal lobe. Grey mater heterotopias can be either subependymal, sub-cortical (any location from the periventricular white mater to the grey-white junction) or take the form of band heterotopia where a white mater zone separates a thin band of cortex from a broad band of sub-cortical grey mater. Other anomalies include lissensephaly, polymicrogyria and schizencephaly. Neurocutaneous syndromes including Sturge- Weber and Tuberous sclerosis can also be diagnosed on MRI imaging. Last but not least, neoplasms, vascular malformations, infections and posttraumatic changes can be identified on imaging studies. • Functional MRI (f-MRI): Since f-MRI is a non-invasive modality it is relied upon more frequently to identify eloquent areas of the brain and their proximity to the epileptic focus. It can be used to map motor, sensory and language areas. • Positron emission tomography (PET): PET utilizes an injection of radiolabeled glucose (18-FDG) to measure brain metabolism. Interictal PET usually shows hypo metabolism in the seizure focus. Ictal PET is not practical due to the extremely short half-life of the radiotracers used. PET is most useful in MRI-negative temporal lobe epilepsy, though it may be helpful in extra-temporal epilepsy as well. • Single photon emission computed tomography (SPECT) utilizes an injectable radiolabeled tracer (99m Tc-HPAO) to measure cerebral blood flow. Pre-surgical evaluation consists in performing an ictal SPECT, in which the injection is performed as early as possible during a seizure, and then the patient is scanned within a few hours. Ictal studies usually reveal increased blood flow at the site of seizure onset. Interictal studies often show relative hypo perfusion at the site of seizure onset.

1192 Functional Neurosurgery Comparing ictal and interictal studies, can add additional information. • Video EEG is performed on all patients being considered for epilepsy surgery. Usually patients are admitted to the hospital to an epilepsy-monitoring unit. If the patient’s seizures are not frequent the medication can be withheld, however this should be done judicially as it can cause status epilepticus or can trigger seizures that are not representative of the patient’s usual attacks. Typically 3 to 5 episodes are recorded and analyzed. • Magnetoencepalography (MEG) is a relatively new diagnostic technique, it is similar to EEG, but instead of detecting electric signals it detects magnetic signals originating from the brain. MEG can sometimes detect epiletpiform discharges in patients with normal scalp EEGs and can be considered as a test complementary to EEG. • Neuropsychological testing is performed as a pre-operative baseline. It can also be a predictor of possible cognitive decline with surgery. Additionally it can aid in localizing the epileptic focus. For example, patients with temporal lobe epilepsy tend to have memory deficits. Those with dominant TLE (usually left sided) have more prominent deficits in verbal memory compared with visual memory. Patients with average or above average memory function prior to temporal lobectomy have a higher risk of memory decline, especially with left (dominant) temporal lobectomy. • Wada test: this test helps determine the risk of postoperative memory and language deficits, and aids in seizure localization in patients being considered for temporal lobectomy. Amobarbital is a short-acting barbiturate that is injected into the internal carotid artery, resulting in unilateral hemispheric anesthesia for approximately 10 minutes. During this time, memory items are given to the patient and language is tested. After recovery, recall of the memory items is tested, and then the test is repeated on the other side. A patient with unilateral temporal lobe epilepsy will usually have a significant memory asymmetry with this test, as the epileptogenic hippocampus is already dysfunctional. If the hippocampus to be resected is functioning normally on this test, the chance of a postoperative memory deficit is greater, especially in the dominant hemisphere. Most centers require demonstration of intact function of the contra lateral hippocampus on this test prior to offering temporal lobectomy in order to prevent a severe postoperative amnestic syndrome. • Invasive EEG monitoring consists in the surgical implantation of strips, grids or depth electrodes. Such monitoring is usually performed in three main scenarios: the epileptic lesion is near eloquent cortex, the lesion might be cortical dysplasia or there is a definite discrepancy between the results of the presurgical evaluations. Its goal is not only to record seizure activity helping to pinpoint its origin, but also to map the surrounding brain by stimulating it and assessing the patient’s different functions.

3. Resective surgery for focal epilepsy: The criteria used for focal surgical resections are usually the presence of a discrete lesion on MRI with compatible video-EEG monitoring or an ictal onset zone confirmed by

Surgical Treatment of Epilepsy

1193

intracranial EEG recordings.

Temporal lobe epilepsy: Temporal lobe epilepsy is by far the most common type of epilepsy treated surgically. Surgery for pharmaco-resistant temporal lobe epilepsy has now been clearly shown to be superior to medical treatment. In a prospective randomized controlled trial comparing anterior temporal lobectomy to the best medical treatment, 64% of patients that did undergo surgery were free of disabling seizures while this number was only 8% in the medical group. In that same study patients that underwent surgery had a better quality of life when compared to patients treated medically. A significant number of case series of patients that had a temporal lobectomy for epilepsy confirmed those results. Most of these series reported a freedom from disabling seizures rate of around two thirds. The presence of unilateral hippocampal sclerosis on the side responsible for seizures and the absence of tonic clonic seizures preoperatively were predictive of remission from seizures postoperatively. Remission from seizures is usually defined as complete absence of seizures for two years. The rate of seizure relapse after achieving remission in patients that underwent a temporal lobectomy varied from 20% to 40%. Predictors of relapse included a delay in achieving remission, normal hippocampus on pathological examination and a high number of monthly seizures preoperatively. Temporal lobe resections can be tailored to involve neocortical structures and mesial temporal structures depending on the extent of the pathology. If the pathology is purely mesial temporal we favor selective resection of the amygdala and hippocampus through the transsylvian approach (Figure 2). A significant misconception about the transsylvian selective amygdalohippocampectomy is its description as transinsular. In reality the resection of the mesial temporal structures is transamygdala and proceeds through an anteriorposterior axis. Classically, a pterional craniotomy is fashioned. Care should be taken to elevate the temporalis muscle in a way that will allow exposing the temporal pole. Once the craniotomy is performed the orbital roof is flattened and both the lesser and greater wings of the sphenoid are drilled down to the superior orbital fissure. After the dural opening, the arachnoid over the sylvian fissure is incised anterior to the venous sylvian confluence. The interopercular sulci between the lateral fronto-orbital gyrus and the superior temporal gyrus are opened using sharp dissection. The use of a rigid selfretaining retractor is strictly avoided. The entrance into the surgical field is maintained

Fig. 2 Intra-operative photograph obtained after completion of the resection of the right mesial temporal structures via a trans-sylvian approach.

1194 Functional Neurosurgery using cotonoids that are wedged at each end of the sylvian fissure opening. Once the interopercular sulcus is opened down to the sylvian fossa and the middle cerebral artery bifurcation is seen, the M1 segment is followed proximally to the carotid bifurcation and the proximal sylvian fossa is opened from inside to outside. At this point several structures need to be inspected. The lateral aspect of the supraclinoid internal carotid artery is visualized and its branches including the posterior communicating artery and the anterior coroidal artery complex are identified. A special attention is given to the lateral branches of the M1 segment of the middle cerebral artery, specifically to the temporopolar and anterior temporal arteries. Sometimes the temporopolar or the anterior temporal arteries will need to be mobilized to allow enough working room to start the exploration of the amygdala. The position of the uncus is noted, as it is very common for it to be herniated through the tentorial incisura. The resection of the amygdala proceeds first in an anterobasal direction down to the crural and ambient cistern. The inferior resection of the amygdala follows, however its relation to the optic tract needs to be well visualized and understood before doing so. The medial part of the amygdaloid nucleus, under the M1 segment and in continuity with the basal forebrain is left unresected. As the resection of the amygadla is completed the temporal horn is entered and the pes hippocampus is identified; anteriorly the crural cistern is now well exposed and the anterior choroidal artery with its branches, the posterior communicating artery, the posterior cerebral artery and the third nerve are all within sight. The resection of the hippocampus and parahippocampal gyrus is followed posteriorly in the direction of the atrium. The choroid plexus covering its body is reflected medially and the taenia fimbriae is exposed gradually and opened anteriorly and posteriorly with the help of bipolar forceps. As this is done the crural cistern is further exposed. The anterior choroidal artery the basilar vein and the optic tract are now well visualized. The lateral branch of the anterior choroidal artery as well as branches of the posterior cerebral artery going to the hippocampus are coagulated and divided. The extent of the hippocampal resection is continued posteriorly to the bifurcation of P2 as it divides into the superomedial and inferolateral trunks, which is at the level of the lateral geniculate body, for a total resection of 25 to 30 mm (Fig.3). At this level the optic track is merging into the lateral geniculate body and the lateral posterior choroidal artery can be seen originating either proximal or distal to the P2 bifurcation. The resection is now continued laterally with its limit at the level of the eminencia collateralis. Care is taken not to injure the inferior temporal trunk and its branches; only those vessels going from it to the parahippocampal gyrus are sacrificed. The inferior ventricular vein that collects the hippocampal veins and drains into the basilar vein is identified, coagulated and divided to complete the resection. The seizure control after selective resections of the mesial temporal structures has been well studied. In 1992 the Second Palm Desert Survey reported the outcomes of several centers with regards to seizure control after surgery for temporal lobe epilepsy. It showed that selective limbic resections achieved a seizure free rate of 68.8% comparable to the 67.9% rate reported for temporal lobectomies. Since that survey several centers have published the results of their selective resections of the amygdala and the hippocampus. Different approaches were used in different centers, including transcortical, sub temporal and transsylvian

Surgical Treatment of Epilepsy

1195

Fig. 3 Immediately postoperative coronal, axial, and sagittal MR images obtained after a right transsylvian amygdalohippocampectomy, showing selective resection of the hippocampus and preservation of the neocortex of the temporal lobe.

amygdalohippocampectomies. In all these series, around 70% of patients were free of disabling seizures (Engel class 1) post operatively. Those results come to refute the argument that a more extensive neocortical resection might be necessary to obtain a good seizure control. Another concern brought against the selective resections of the mesial temporal structures is long-term seizure control. When Wieser looked into that issue in the Zurich series of SAH, 88% of patients that were Engel class 1 the first year after surgery remained so over the next five years, which is comparable or even superior to results reported with temporal lobectomies. In the same series of transsylvian amygdalohippocampectomies, 70% of patients had reduced their anti epileptic medication intake postoperatively. At the time of the last available outcome 49.4% of patients had reduced their antiepileptic medication intake compared to pre-operatively and 27% were without any antiepileptic medication.

Frontal lobe epilepsy (FLE): Surgery for frontal lobe epilepsy accounts for 6–30% of all epilepsy surgeries. It represents the second most common procedure performed to treat pharmacoresistant epilepsy after temporal lobe surgery. A wide variety of seizures, including supplementary motor area seizures, frontal lobe complex partial seizures, and focal motor seizures, can occur from a frontal origin. However, it is not clear that the seizure types are specific to the region of seizure origin. The finding best correlated to the surgical outcome is the presence of a lesion detected on MRI. The reported success rates for seizure control are around 50%.

Parietal and occipital lobe epilepsy: Resective surgery for parietal and occipital lobe epilepsy is even less frequent then frontal lobe epilepsy. Compared with results of surgical treatment for temporal lobe epilepsy, success rates after epilepsy surgery in the parietal or occipital region have been less promising. Many authors have grouped parietal, occipital, and occipitotemporal epilepsies together as posterior cortex epilepsies, whereas others have separately analyzed parietal and occipital

1196 Functional Neurosurgery lobe lesional epilepsies. No matter the grouping, seizure freedom has been reported in ~ 40–60% of patients; however, the diversity of pathological findings, inclusion criteria, and outcome classification scales makes comparison difficult. Postoperative parietal neurological deficits occur in a significant proportion of patients, although most of these are transient. Visual field deficits when they occur are usually more permanent.

4. Disconnective surgery for generalized epilepsy: Corpus callosotomy: Patients with intractable epilepsy frequently run the risk of personal injury from falls caused by sudden loss of consciousness. The latter is particularly common in Patients with atonic seizures also known as drop-attacks. In these patients, surgical treatment in the form of corpus callosotomy may be considered. Callosotomy, although not curative, may prevent harmful drop attacks from occurring. Several reports have attested to the value of corpus callosotomy as a palliative procedure to improve the quality of life of patients with intractable, generalized epilepsy, especially if the seizures are of the atonic type. Most series report an elimination of the drop attacks in 80% of patients. Early approaches to callosotomy consisted in sectioning the entire corpus callosum. However several consequences of such a procedure, known as disconnection syndromes have been reported. They can be attenuated if some of the corpus callosum, particularly the splenium, is preserved, or if the complete callosotomy is performed in 2 stages, especially in older children with normal to moderately impaired intelligence. The introduction of partial callosotomy was an attempt to obtain the surgical benefits of seizure control without the complication of disconnection syndromes. Since then there has been controversy as to which procedure is most effective. Patients with at least 2 seizure types, a verbal IQ lower then__80 and diffuse ictal EEG patterns had poor outcomes with anterior callosotomies alone, suggesting more diffuse cerebral involvement of both anterior and posterior cortical regions. In these cases a total callosotomy might be indicated.

Functional hemispherectomy: Functional hemispherectomy has been used since the 1980s to treat disabling, medically refractory epilepsy resulting from diffuse unilateral hemispheric disease. The underlying pathologies causing seizures requiring functional hemispherectomy include infarcts, encephalomalacia, hemimegalencephaly, cortical dysplasia, Sturge Weber syndrome and Rasmussen encephalitis. Other less common causes include developmental abnormalities such as polymicrogyria and porencephalic cysts. Those patients usually have a neurological dysfunction associated with the hemispheric pathology and the hemispherectomy does not add any significant neurologic morbidity. Over the years, the procedure has evolved and different technical variations have been described. Regardless of the specific technique, the operation generally includes the disruption of the internal capsule/corona radiata, a transventricular callosotomy,

Surgical Treatment of Epilepsy

1197

resection of mesial temporal structures, and a frontobasal disconnection. Multiple studies have shown functional hemispherectomy to be of significant benefit in these patients, with long-term rates of postoperative seizure freedom of around 43 to 90%.

5. Vagal nerve stimulation (VNS): VNS was initially approved to treat partial epilepsy. However there is increasing evidence that VNS is effective in treating symptomatic generalized epilepsy, refractory idiopathic generalized epilepsy, Lennox_Gastaut syndrome and other seizure disorders. There is no consensus regarding the mechanism of action of VNS, but it likely acts at multiple sites. It was initially hypothesized that VNS works by desynchronizing electroencephalography activity, and this hypothesis as well as VNS’s anti-seizure effects has been proven in animal models. Placement of a vagal nerve stimulator is generally safe, with few complications or side effects. The most common problem is infection, which occurs in up to 5–7% of patients. The most common neurological problem following implantation is vocal cord paralysis, occurring in ~1% of patients. Patients have also reported some transient effects, which do not usually require ceasing therapy. These symptoms include hoarseness, cough, dyspnea, nausea, and obstructive sleep apnea. In virtually all studies published since the advent of VNS, 35–45% of patients have demonstrated a decreased frequency of seizures exceeding 50% of their baseline level and ~ 2% have become seizure free. There appears to be no subset of epilepsy for which the results are substantially different.

REFERENCES 1. Wiebe S, Blume WT, Girvin JP, Eliasziw M: Effectiveness and Efficiency of Surgery for Temporal Lobe Epilepsy Study Group: Arandomized, controlled trial of surgery for temporal lobe epilepsy. NEngl J Med 345:311–318, 2001 2. Tanriverdi T, Olivier A, Poulin N, Andermann F, Dubeau F: Long-term seizure outcome after mesial temporal lobe epilepsy surgery: corticalamygdalohippocampectomy versus selective amygdalohippocampectomy JNeurosurg 108:517–524, 2008 3. Yasargil MG, Teddy PJ, Roth P: Selective amygdalo-hippocampectomy. Operative anatomy and surgical technique. Adv Tech Stand Neurosurg 12:93–123, 1985 4. Weiser HG, Yasargil NG: Selective amygdalohippocampectomy as a surgical treatment of mesiobasal limbic epilepsy. Surg Neurol 17:445–457, 1982 5. Weiser HG, Ortega M, Friedman A, Yonekawa A: Long-term seizure outcomes following amygdalohippocampectomy. JNeurosurg 98:751-763, 2003 6. Ferrier CH, Engelsman J, Alarcon G, Binnie CD, Polkey CE. Prognostic factors in presurgical assessment of frontal lobe epilepsy. J Neurol Neurosurg Psychiatry 1999; 66: 350–6. 7. Jeha L, Najm I, Bingaman W. Surgical outcome and prognostic factors of frontal lobe epilepsy surgery. Brain (2007), 130, 574–584. 8. BinDer D, Podlogar M, Clusmann H, Bien C, Urbach H, Schramm J, Kral T. Surgical treatment of parietal lobe epilepsy J Neurosurg 110:1170–1178, 2009. 9. Aykut-Bingol C, Bronen RA, Kim JH, Spencer D, Spencer SS. Surgical outcome in occipital lobe epilepsy: implications for pathophysiology. Ann Neurol 1998 vol. 44 (1) pp. 60-69.

1198 Functional Neurosurgery 10. Jenssen S, Sperling MR, Tracy JI, Nei M, Joyce L, David G, et al: Corpus callosotomy in refractory idiopathic generalized epilepsy. Seizure 15:621–629, 2006. 11. Jea A, Vachhrajani S, Widjaja E, Nilsson D, Raybaud C, Shroff M, et al: Corpus callosotomy in children and the disconnection Syndromes : a review. Childs Nerv Syst 24:685–692, 2008. 12. Villemure JG, Mascott CR: Peri-insular hemispherotomy: surgical principles and anatomy. Neurosurgery 37:975–981, 1995. 13. Cats EA, Kho KH, Van Nieuwenhuizen O, Van Veelen CW, Gosselaar PH, Van Rijen PC: Seizure freedom after functional hemispherectomy and a possible role for the insular cortex: the Dutch experience. J Neurosurg 107:275–280, 2007. 14. Ng M, Devinsky O: Vagus nerve stimulation for refractory idio- pathic generalized epilepsy. Seizure 13:176–178, 2004. 15. Schachter S: Vagus nerve stimulation therapy summary: five years after FDA approval. Neurology 59: S15–S20, 2002.

1199

Epilepsy Surgery in Children RYAN ALKINS MD, and JAMES T RUTKA MD PhD FRCSC Division of Neurosurgery, The Hospital for Sick Children, University of Toronto Key words: Epilepsy surgery, magnetoencephalography, cortical resection, lobectomy

1 Introduction Epilepsy affects 3-5% of the world’s population.33,56,77 It is associated with significant social and economic52 burden as well as effects on cognition, memory20 and an increased mortality.26 In the pediatric population epilepsy occurs in 1-2% of children and has the highest incidence in the first year of life.13, 32 Despite optimized medical therapy, 10-40% of children with epilepsy will continue to have seizures.7, 12, 24, 57 With continuing advances in imaging, diagnostics, monitoring and neuronavigation surgery for those patients with medically refractory epilepsy is a promising option. Patients with localizable epilepsy may have a significant reduction in the frequency of seizures or even be cured of epilepsy with a resection. In those with non-localizable epilepsies, palliative procedures such as corpus callosotomy or vagal nerve stimulator implantation have demonstrated benefit. The goals are not only reduction in seizure frequency but also improved quality of life.

2 Surgical Candidates Epilepsy patients with lesional or with medically refractory seizures are those who are most likely to come to the attention of a neurosurgeon. Medically intractable epilepsy is generally considered the failure of two anti-epileptic medications appropriate to the seizure type and in the maximum tolerable dose for a period of 18-24 months.28 Failure may be due to inadequate seizure control or intolerable medication side effects. Consideration should be given to the age of the patient; seizure onset prior the age of one may confer a higher risk of intractable seizures,25 while younger children may be more suited to surgical treatment because of the increased plasticity of the developing brain.14, 20, 78 Certain childhood epilepsy syndromes (Table 1) or etiologies (Table 2) may also confer a higher risk of medical intractability.3, 48, 74

3 Workup Thorough clinical, electrophysiological, and imaging investigations should all be undertaken. Patient selection should ideally take place within the setting of a multidisciplinary epilepsy team. The goal of the workup is to delineate the epileptogenic zone, which may be considered the tissue that needs to be resected surgically, and to assess the cortex in and around this area to determine the risks of surgery.10

1200 Functional Neurosurgery Table 1 Etiologies of epilepsy associated with medical intractability

Table 2 Epilepsy types and syndromes associated with medical intractability

3.1 History and Physical The history should establish seizure onset, type(s) and frequency, anti-epileptic medications used and compliance, as well as any family history of seizures. A complete neurological examination should be performed.

3.2 Scalp Electroencephalography EEG can be useful to assess both ictal and inter-ictal activity. It can help lateralize and localize the electrical onset of seizures as well as confirm and document epileptic events. Video-EEG in the setting of an inpatient monitoring unit is optimal. Titration of new or existing medications can also be facilitated in this setting.

3.3 Structural Magnetic Resonance Imaging MRI is the structural imaging modality of choice as per the International League Against Epilepsy.35 Imaging sequences should include T1- and T2-weighted, FLAIR, and proton density sequences, interpreted by an experienced neuroradiologist in the context

Fig. 1 Coronal FLAIR MR showing left mesial temporal lobe sclerosis in 7 year old female. She underwent left temporal lobectomy, and has been seizure free now for 5 years.

Epilepsy Surgery in Children

1201

of the seizure semiology and EEG results (Figure 1).76 A 3D T1-weighted volumetric sequence should also be included; post-processing, such as curvilinear reformats, or quantitative analysis may reveal subtle abnormalities that would have otherwise been missed.76

3.4 Magnetic Resonance Spectroscopy MRS can quantify metabolites in the brain, including N-acetyl aspartate (NAA) and choline. Simplistically, NAA is a component of neurons while choline is a component of cell membranes. In cases with neuronal dropout and gliosis such as temporal lobe epilepsy, the ratio of NAA to choline is decreased.26 There is good correlation between EEG abnormalities in non-lesional temporal lobe epilepsy and focal decreases in NAA, including cases where the hippocampal volumes on MRI are normal.16, 19, 42 In extratemporal cases this ability is reduced; in a study of frontal lobe epilepsy lateralization with MRS was possible in only half of the cases.26

3.5 Magnetoencephalography MEG measures extracranial magnetic fields generated by intracellular currents, and in combination with MRI can be used for localization, in cases identifying foci structural MRI alone would miss.47 Localization with MEG is better suited to neo-cortical epileptogenic foci rather than deep foci such as the mesial temporal lobe structures76, 59; MEG is therefore particularly useful in the pediatric population where neo-cortical epilepsy is more common than mesial temporal lobe epilepsy (Figure 2). It can also be used for pre-surgical mapping of eloquent cortex and is 89-95% concordant with WADA for language determination.51

Fig. 2 MEG in 5 year old femal in status epilepticus showing spike wave disturbance in right peri-insular region. This patient required hemispherectomy to stop her seizures. She is now seizure free.

3.6 Diffusion Tensor Imaging DTI exploits the anisotropic diffusion of water molecules in the brain as a result of the microstructural environmental. This can help in identifying subtle changes in white matter near malformations of cortical development not seen on structural MRI.75 In those

1202 Functional Neurosurgery

Fig. 3 Diffusion tensor imaging analysis of 5 year old male with intractable Rolandic epilepsy. Yellow indicates corticospinal tracts bilaterally. Green indicates site of primary epileptogenesis. This patient required Rolandic resection of the seizure focus to become seizure free.

cases where an abnormality is identified on structural MRI, diffusion abnormalities, taken together with EEG results, may correspond to epileptogenic areas outside the boundaries of the structural lesion.76 Another application of DTI is tractography. The fibres of the optic radiations may be visualized in order to tailor the extent of an anterior temporal lobectomy.66,76 Other white matter tracts, such as the corticospinal as well as those associated with the limbic system and hippocampus, can be used in presurgical planning (Figure 3). In the future tractography may be used to tailor the extent of corpus callosotomy and other disconnective procedures.36

3.7 Functional MRI Functional MRI is primarily used to map language, memory, sensory and motor function pre-operatively. For language, fMRI has greater than 90% concordance with the intracarotid amobarbital test and in those patients with disparate results it is more likely to show bilaterally represented language dominance.76 Compared with cortical stimulation, fMRI is 90% sensitive and 67% specific.11 Functional MRI is best at mapping sensorimotor areas (Figure 4). With regards to memory testing for anterior temporal resections, fMRI is in agreement with intracarotid amybarbitol testing in 50-60% of cases.8

Fig. 4 fMRI in 16 year female with left occipital seizures. Here, the fMRI clearly shows left frontal opercular activation of language in this right handed female.

Epilepsy Surgery in Children

1203

3.8 Positron Emission Tomography The main role of FDG-PET in intractable epilepsy is lateralization, whereby regions of inter-ictal glucose hypo-metabolism are identified (Figure 5). However, in some childhood neocortical epilepsies focal hyper-metabolism may be seen.17 FDG-PET can also be used to guide subdural electrode placement in non-lesional neocortical epilepsies. Other PET ligands such as 11C-flumazenil (FMZ), a reversible inhibitor at the benzodiazepine binding site of the GABA receptor, has decreased uptake in the epileptogenic focus and may be more confined than the hypo-metabolism with FDGPET.76 In patients with extra-temporal epilepsy it may show focal restricted uptake in the face of normal MR imaging53, and may identify a larger region, or distant abnormalities, in those with malformations of cortical development than is seen on MRI.54 In those with unilateral hippocampal sclerosis it may reveal contralateral abnormalities.41

Fig. 5 PET scan in 12 year female depicting right parieto-occipital hypmetabolism. This patient underwent right occipital lobectomy with good outcome.

3.9 Single-Photon Emission Computed Tomography SPECT is used to localize and lateralize the epileptogenic zone when other noninvasive investigations have failed. It is a measure of cerebral blood flow using radiolabeled compounds and has less spatial resolution that PET; there is decreased CBF in the epileptogenic zone in the inter-ictal period and increased CBF during a seizure.76 When ictal and inter-ictal examinations are digitally subtracted and co-registered with structural MRI, the epileptogenic zone can be reliably located.49

3.10 Neuropsychological Evaluation Neuropsychological assessment establishes a baseline to which postoperative comparisons can be made and can be used in determining the impact of surgery. It can also be helpful in determining the dominant hemisphere for verbal and non-verbal functions in older children.64 In younger children a neurodevelopmental assessment can be done.

1204 Functional Neurosurgery

3.11 Intracarotid Amybarbitol Injection (WADA) Functional MRI, MEG and neuropsychological testing are generally done first. If the patient cannot undergo MRI or the results are inconclusive, intracarotid amybarbitol injection can help in determining speech dominance, as well as the possible memory dysfunction from anterior temporal lobectomy.

4 Surgery An algorithm for decision making is shown in Figure 6. If a lesion has been identified the patient may proceed to surgery so long as the investigations are concordant. Conversely, in cases where the epilepsy is generalized vagal nerve stimulation or corpus callosotomy are options. If the seizures are lateralizable to a single hemisphere, and particularly if the patient has a structural hemispheric abnormality and a significant neurological deficit on the contralateral side, hemispherectomy may be entertained. Epilepsies which are localizable but non-lesional or where investigations are discordant or inconclusive often require invasive monitoring.

Fig. 6 Algorithm for treatment decision making in medically refractory epilepsy. Adapted from Go and Snead 2008.28

Epilepsy Surgery in Children

1205

4.1 Intracranial Monitoring Intracranial EEG remains the gold standard for delineating the epileptogenic zone, which is frequently a larger area than the structural abnormality seen in pre-surgical imaging.9 There is evidence in cases of lesional epilepsy that resecting not only the lesion itself but also any spike-positive tissue yields improved seizure control.67 Examples of cases where intracranial EEG is helpful include temporal lobe epilepsy where the EEG suggests unilateral onset but the MRI shows contralateral lesions, or cases where the MRI shows a unilateral structural lesion but the EEG localizes poorly. It is frequently used for neocortical resections especially when near or involving eloquent cortex. Intracranial EEG can be done at the time of the planned resection or as the initial step in a two-part procedure (Figure 7); performing the latter allows more comprehensive ictal and inter-ictal recordings. In either case cortical stimulation may be done via the electrodes to map language, somatosensory areas. The type and placement of electrodes should be done taking into account noninvasive test results. For example, in non-lesional cases, if neuropsychological testing shows a large disparity between verbal and non-verbal memory, mesial temporal structures may be involved and depth electrodes should be considered, whereas relatively spared verbal memory may point to the temporal neocortex and the placement of subdural electrodes may help avoid resection of the mesial structures.9

Fig. 7 Large left subdural grid in child with intractable epilepsy without obvious lesion on MRI. Note depth electrodes placed into temporal lobe, and right posterio frontal area.

4.2 Surgical Adjuncts Neuronavigation assists in accurate placement of depth electrodes,21 tailoring of the craniotomy size and locating the lesion or cortical region of interest. It may be linked to functional imaging to allow identification of previously mapped eloquent areas and to guide the extent of resection (Figure 8). Direct cortical stimulation can be used in awake patients or in combination with somatosensory evoked or motor evoked potentials in anesthetized patients to identify the central sulcus and somatosensory cortex. Focal stimulation with a bipolar electrode using a train of 5 high frequency pulses has been shown to have a lower risk of causing seizures (Figure 9).68

1206 Functional Neurosurgery

Fig. 8 Neuronavigation used in 16 year female with spike cluster in somatosensory cortex (green triangles). This patient underwent excision of the spike cluster without subdural grid monitoring, and is now seizure free off medications.

Fig. 9 Train of 5 recordings shown using 2 contact electrode on the motor strip prior to resection of primary zone of epileptogenesis (electrodes 24-26, 36-37). Using train of 5 recordings, the corticospinal tract can be preserved while operating in the adjacent cortex.

4.3 Neurosurgical Procedures 1.1.1 Vagal Nerve Stimulator Indications: Not first-line therapy. For patients who are not suitable for resection or unwilling to undergo surgery.

Epilepsy Surgery in Children

1207

Fig. 10 Vagal nerve stimulator coiled shown here applied to left vagus nerve. Dissection is carried out in the carotid sheath with separation of the vagus nerve from the carotid artery and the jugular vein.

Description: The approach is similar to that performed for an anterior discectomy or carotid endarterectomy. Preoperative antibiotics are given. The carotid sheath is exposed and opened; the vagus, which is exposed for a length of 3-4cm, is usually found between the jugular vein and carotid artery although can be deep and lateral to the carotid.45 An incision is fashioned inferior to the clavicle and a pocket for the pulse generator developed superficial to the pectoralis fascia. A lead is then passed from the neck to the pocket and an electrode placed around the vagus nerve (Figure 10). The anesthesia team should be made aware prior to testing of the device, as although the left vagus has fewer cardiac efferents than the right, bradycardia, complete AV block and asystole have been reported.45 Complications: Most frequently, infection in 5-7%.45 This may be reduced by washing the chest pocket with a dilute antibiotic solution. Infection requires removal of the device and may make re-implantation more complicated; when doing so exposing the vagus above the previous site is suggested.45 Neurological complications include vocal cord paralysis in 1%, and transient effects such as hoarseness, cough, dyspnea, nausea, and obstructive sleep apnea. 2, 5,31, 63 Outcome: Approximately 45-55% of patients have a greater than 50% reduction in seizure frequency, and many patients show significant improvements in quality of life measures.2, 5, 73

1.1.1 Corpus Callosotomy Indications: Generalized, non-localizable epilepsies with atonic seizures as one of the predominant types. This may include patients with Lennox-Gastaut or West syndrome, and complications from ischemic, infectious or metabolic insults. In pre-pubescent or severely disabled children total callosotomy may be performed with few clinical sideeffects.44 In older children with atonic, or non-lesional absence, myoclonic and tonic-

1208 Functional Neurosurgery

Fig. 11 Corpus callosotomy being performed with image guidance. The rostrum of the corpus callosum is being identified at this time.

clonic seizures there may be benefit to begin with an anterior callosotomy,37 leaving the splenium intact; if seizure control is inadequate the callosotomy may subsequently be completed.65 Procedure: A right sided approach is preferred for right-hand dominant children; however, the venous anatomy visualized on MRI is taken into account. Neuronavigation is particularly useful in determining the extent of resection of the corpus callosum (Figure 11).36 Caution not to stray off the midline must be taken otherwise injury to the fornices may occur. Complications: In the senior author’s series, there were no operative mortalities. 36 Generally, complications include infection, CSF leak, cerebral edema from retraction, congestion and/or infarction from venous injury, and anterior cerebral artery territory infarction. Disconnection syndromes appear to be transient prior to puberty and these children tend to experience improved cognitive and social outcomes.43, 58 In older children, with normal to moderately impaired intelligence, the complications of disconnection syndromes may be reduced by preserving the splenium or, on rare occasion, completing the callosotomy in two steps.39, 50 Outcomes: 80-100% of patients are seizure free or have greater than 75% improvement in atonic seizures.36, 65 Complete callosotomy appears to have greater control of the secondary seizure type.

Epilepsy Surgery in Children

1209

1.1.1 Hemispherotomy Indications: Widespread unilateral pathology. Suitable conditions include hemiplegia from a prenatal vascular event, Sturge-Weber, hemimegencephaly, diffuse cortical dysplasia, hemiconvulsion-hemiplegia-epilepsy syndrome, Rasmussen encephalitis, and seizures from previous infection or traumatic brain injury (Figure 12).22 In patients with pre-existing hemiplegia and hemianopia, new neurological deficits will largely be avoided and the decision to proceed to surgery may be easier. The non-affected hemisphere should be unaffected both on MRI imaging and electroencephalography. Rare exceptions can be made when seizures always originate in one hemisphere to affect the other but bilateral independent spikes on EEG are a poor prognostic factor.15, 62 Description: The goal of surgery is the disconnection of the corpus callosum, internal capsule and corona radiata, anterior commissure, hippocampal commissure and mesial temporal structures. All dissections are subpial and the vessels are preserved. One such new technique is the vertical parasagittal hemispherotomy as described by Delalande et al.23 A small craniotomy 1-2 cm off the midline and 2/3 posterior and 1/3 anterior to the coronal suture is fashioned. A 3 × 2 cm corridor through the frontal lobe is resected to reach the lateral ventricle, where the thalamus and foramen of Munro are then identified. The body and splenium of the corpus callosum are resected to the roof of the third ventricle; the corpus callosum is found by following the roof of the lateral ventricle medially. Midline is identified by the pericallosal arteries anteriorly and the falx. The hippocampus is disconnected by cutting the posterior column of the fornix at the level of the trigone. This vertical incision is made lateral to the thalamus and in the plane of the choroid plexus of the temporal horn and extending to the most anterior part of the ventricle, while staying in the white matter. The callosotomy is completed by resecting the rostrum and genu to the anterior commissure. Finally the posterior part of the gyrus rectus is resected to allow visualization of the optic nerve and anterior cerebral artery while making an anterolateral incision through the caudate nucleus from the gyrus rectus to the anterior temporal horn. Complications: Mortality 2-5%, hydrocephalus 2-16%, infection 5%, hemorrhage 5% based on several recent series.22 Immediately post-operatively patients may have lethargy, low-grade fever, decreased appetite and irritability attributed to blood in the CSF.23, 71

Fig. 12 Left hemimegalencephaly shown here in 2 year old male with intractable epilepsy requiring hemispherectomy. A left peri-insular hemisherotomy was performed, and the child is now seizure free off medications.

1210 Functional Neurosurgery Outcome: Engel class I in 40-90%; Rasmussen syndrome, Sturge-Weber syndrome and infantile hemiplegias have seizure free rates of 73-90% while multilobar cortical dysplasias or hemimegencephaly have a lower percentage with 63-80%.22 In one series all children who could walk pre-operatively preserved this ability and overall, 84% of children were able to walk alone or with assistance.23 Also, half of the children regained some use of the hemiparetic hand. Assessments of global outcomes were inversely correlated to the delay to surgery; several authors recommend performing the procedure no later than 2-3 years after the onset of seizures.39, 55 Communication scores were higher following right hemisphere resection.

1.1.1 Temporal Procedures: Indications: Temporal neocortical lesions, tumours, mesial temporal sclerosis. Procedure: The exact procedure will depend upon the pathology. In those patients with epileptogenic zones localizable to the neocortex, a resection of the latter may be performed while sparing the mesial structures. Where a discrete lesion is identified, such as a tumour, a resection is performed in the usual fashion (Figure 13). Patients with mesial temporal sclerosis may undergo anterior temporal lobectomy or selective amygdalohippocampectomy. Conventionally the posterior extent of resection should not exceed 5cm from the temporal pole on the dominant side and 6cm on the left.72 Complications: Mortality is low; several recent series report no fatalities.32, 40, 69 Morbidity includes homonymous superior quandrantanopsia, language deficits, hemiplegia (either due to spasm of Sylvian vessels or injury to perforating vessels of the internal capsule), hydrocephalus, and infection. Outcome: Temporal focal cortical dysplasias had an 87% seizure free rate in one series.1 Clusmann et al. found that in a pediatric population, of those undergoing anterior temporal lobectomy, 94% had Engel class I or II versus only 74% of those undergoing selective amygdalohippocampectomy.18 The experience at The Hospital for Sick Children in Toronto revealed an Engel class I outcome in 67% at ≥10 years of follow-up overall for temporal lobe surgeries for medically intractable epilepsy.6 Children with a tumour or cavernoma had a higher seizure free rate of 79%.

Fig. 13 Left mesial temporal lobe tumor in 5 year old male with intractable epilepsy. Following left temporal tumor removal, the child is seizure free of medications. The lesion proved to be a ganglioglioma.

Epilepsy Surgery in Children

1211

1.1.1 Extratemporal Procedures: Indications: Various etiologies including vascular or post-infectious insults, tumours, tuberous sclerosis complex and focal cortical dysplasias. Procedure: The surgical technique will depend on numerous factors including the etiology, anatomical location and proximity to or involvement of eloquent cortex. Neocortical resections almost always require electrocorticography either as an initial procedure with subdural and/or depth electrodes or with mapping and stimulation at the time of surgery. If the epileptogenic zone encompasses eloquent cortex then multiple subpial transections may be performed; this is thought to reduce the horizontal spread of the ictal activity but preserve the vertically oriented functional connections. Disconnection rather than resection may be an option in, for example, hypothalamic hamartomas.22 Complications: Mortality is very low.4, 30, 61 Complications occur in approximately 5%.61 The most common neurological complication in neocortical resection is transient hemiparesis. Others include infection, bleeding, hydrocephalus, permanent deficits as well as recurrent seizures. The risks of multiple subpial transections include intraparenchymal hemorrhage, cerebral edema, and fine motor abnormalities; transient deficits including hemiparesis, dysphasia, dysnomia, and/or memory disturbance are common but are rarely permanent. Outcome: In Tuberous Sclerosis Complex, roughly two-thirds are seizure-free.10 Multiple subpial transections result in 33-46% of children having an Engel class I or II outcome.4 While some centres report less than 50% long-term seizure-free status in cases of focal cortical dysplasia, other centres have shown aggressive resection may result in 78% of children being seizure-free with 94% showing greater than 80% reduction in seizure frequency.30 Overall Engel I or II outcomes for various pathologies are in the range of 80%.29, 30, 61

2 Conclusion Surgery is a valuable tool in the management of epilepsy in children. Ongoing technological advancements are allowing more detailed preoperative non-invasive testing to take place, leading to more exact delination of the epileptogenic zone for resection. In combination with neuronavigation, and intra-operative and intracranial monitoring, epilepsy surgery is a safe and effective option for epileptic children, often offering a cure for a debilitating illness.

REFERENCES 1. Alexandre V Jr, Walz R, Bianchin MM, Velasco TR, Terra- Bustamante VC, Wichert-Ana L, et al: Seizure outcome after surgery for epilepsy due to focal cortical dysplastic lesions. Seizure 15:420–427, 2006 2. Alexopoulos A, Kotagal P, Loddenkemper T, Hammel J, Bingaman WE: Long-term results with vagus nerve stimulation in children with pharmacoresistant epilepsy. Seizure 15:491–503, 2006 3. Barkovich AJ, Kuzniecky RI, Jackson GD, Guerrini R, Dobyns WB: Classification

1212 Functional Neurosurgery

4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

17. 18. 19. 20. 21.

system for malformations of cortical development: update 2001. Neurology 57:2168–2178, 2001 Benifla M, Otsubo H, Ochi A, Snead OC III, Rutka JT: Multiple subpial transections in pediatric epilepsy: indications and outcomes. Childs Nerv Syst 22:992–998, 2006 Benifla M, Rutka JT, Logan W, Donner E: Vagal nerve stimulation for refractory epilepsy in children: indications and experience at The Hospital for Sick Children. Childs Nerv Syst 22:1018–1026, 2006 Benifla M, Rutka JT, Otsubo H, Lamberti-Pasculli M, Elliot I, Sell E, et al. Long-term seizure and social outcomes following temporal lobe surgery for intractable epilepsy during childhood. Epilepsy Research 82:133-138, 2008 Berg AT, Shinnar S, Levy SR, Testa FM, Smith Rapaport S, Beckerman B: Early development of intractable epilepsy in children: a prospective study. Neurology 56:1445–1452, 2001 Binder JR, Detre JA, Jones-Gotman M, Swanson SJ: Functional MRI of episodic memory in temporal lobe epilepsy. Epilepsia 43 (7 Suppl):2, 2002 Blount JP, Cormier J, Kim H, Kankirawatana P, Riley KO, Knowlton RC. Advances in intracranial monitoring. Neurosurg Focus 25 (3):E18, 2008 Bollo RJ, Kalhorn SP, Carlson C, Haegeli V, Devinsky O, Weiner H. Epilepsy surgery and tuberous sclerosis complex: special considerations. Neurosurg Focus 25 (3):E13, 2008 Bookheimer SY, Zeffiro TA, Blaxton T, Malow BA, Gaillard WD, Sato S, et al: A direct comparison of PET activation and electrocortical stimulation mapping for language localization. Neurology 48:1056–1065, 1997 Camfield C, Camfield P, Gordon K, Smith B, Dooley J: Outcome of childhood epilepsy: a population-based study with a simple predictive scoring system for those treated with medication. J Pediatr 122:861–868, 1993 Camfield CS, Camfield PR, Gordon K, Wirrell E, Dooley JM: Incidence of epilepsy in childhood and adolescence: a population-based study in Nova Scotia from 1977 to 1985. Epilepsia 37:19–23, 1996 Caplan R: Epilepsy in early development: the lesson from surgery for early intractable seizures. Semin Pediatr Neurol 2:238–245, 1995 Carmant L, Kramer U, Riviello JJ, Helmers SL, Mikati MA, Madsen JR, et al: EEG prior to hemispherectomy: correlation with outcome and pathology. Electroencephalogr Clin Neurophysiol 94:265–270, 1995 Cendes F, Caramanos Z, Andermann F, Dubeau F, Arnold DL: Proton magnetic resonance spectroscopic imaging and magnetic resonance imaging volumetry in the lateralization of temporal lobe epilepsy: a series of 100 patients. Ann Neurol 42:737–746, 1997 Chugani HT, Shewmon DA, Khanna S, Phelps ME: Interictal and postictal focal hypermetabolism on positron emission tomography. Pediatr Neurol 9:10–15, 1993 Clusmann H, Kral T, Gleissner U, Sassen R, Urbach H, Blumcke I, et al: Analysis of different types of resection for pediatric patients with temporal lobe epilepsy. Neurosurgery 54:847–860, 2004 Connelly A, Van Paesschen W, Porter DA, Johnson CL, Duncan JS, Gadian DG: Proton magnetic resonance spectroscopy in MRI-negative temporal lobe epilepsy. Neurology 51:61–66, 1998 Cross JH, Jayakar P, Nordli D, Delalande O, Duchowny M, Wieser HG, et al: Proposed criteria for referral and evaluation of children for epilepsy surgery: recommendations of the Subcommission for Pediatric Epilepsy Surgery. Epilepsia 47:952–959, 2006 De Almeida AN, Olivier A, Quesney F, Dubeau F, Savard G, Andermann F: Efficacy of and morbidity associated with stereoelectroencephalography using computerized tomography- or magnet- ic resonance imaging-guided electrode implantation. J

Epilepsy Surgery in Children

1213

Neurosurg 104:483–487, 2006 22. De Ribaupierre S, Delalande O. Hemispherotomy and other disconnective techniques. Neurosurg Focus 25 (3):E14, 2008 23. Delalande O, Bulteau C, Dellatolas G, Fohlen M, Jalin C, Buret V, et al: Vertical parasagittal hemispherotomy: surgical procedures and clinical long-term outcomes in a population of 83 children. Neurosurgery 60 (2 Suppl): ONS19–ONS32, 2007 24. Dlugos DJ, Samuel MD, Strom BL, Farrar JT: Response to first drug trial predicts outcome in childhood temporal lobe epilepsy. Neurology 57:2259–2264, 2001 25. Farrell K, Wirrell E, Whiting S: The definition and prediction of intractable epilepsy in children. Adv Neurol 97:435–442, 2006 26. Gaitatzis A, Johnson AL, Chadwick DW, Shorvon SD, Sander JW: Life expectancy in people with newly diagnosed epilepsy. Brain 127:2427–2432, 2004 27. Garcia PA, Laxer KD, van der Grond J, Hugg JW, Matson GB, Weiner MW: Proton magnetic resonance spectroscopic imaging in patients with frontal lobe epilepsy. Ann Neurol 37:279–281, 1995 28. Go C and Snead OC III. Pharmacologically intractable epilepsy in children: diagnosis and preoperative evaluation. Neurosurg Focus 25 (3):E2, 2008 29. Goyal M, Robinson S. Expanding the role of surgery in intractable extratemporal pediatric epilepsy. Neurosurg Focus 25 (3):E15, 2008 30. Handler M, Laoprasert P: Outcome after aggressive surgery for pediatric neocortical epilepsy. J Neurosurg Pediatrics 1: A351, 2008 (Abstract) 31. Hatton K, McLarney J, Pittman T, Fahy B: Vagal nerve stimulation: overview and implications for anesthesiologists. Anesth Analg:1241–1249, 2006 32. Hauser WA, Annegers JF, Kurland LT: Incidence of epilepsy and unprovoked seizures in Rochester, Minnesota: 1935–1984. Epilepsia 34:453–468, 1993 33. Hauser WA, Hesdorffer DC: Epilepsy: frequency, causes and Consequences. New York: Demos, 1990 34. Henry TR, Votaw JR: The role of positron emission tomography with [18F]fluorodeoxyglucose in the evaluation of the epilepsies. Neuroimaging Clin N Am 14:517–535, ix, 2004 35. ILAE Commission on Neuroimaging: Guidelines for neuroimaging evaluation of patients with uncontrolled epilepsy considered for surgery. Commission on Neuroimaging of the International League Against Epilepsy. Epilepsia 39:1375–1376, 1998 36. Jea A, Vachrajani S, Johnson KK, Rutka JT. Corpus callosotomy in children with intractable epilepsy using frameless stereotactic neuronavigation: 12-year experience at The Hospital for Sick Children in Toronto. Neurosurg Focus 25 (3):E7, 2008 37. Jenssen S, Sperling MR, Tracy JI, Nei M, Joyce L, David G, et al: Corpus callosotomy in refractory idiopathic generalized epilepsy. Seizure 15:621–629, 2006 38. Jonas R, Nguyen S, Hu B, Asarnow RF, LoPresti C, Curtiss S, et al: Cerebral hemispherectomy: hospital course, seizure, developmental, language, and motor outcomes. Neurology 62:1712–1721, 2004 39. Kawai K, Shimizu H, Yagishita A, Maehara T, Tamagawa K: Clinical outcomes after corpus callosotomy in patients with bihemispheric malformations of cortical development. J Neurosurg 101:7–15, 2004 40. Kim S, Wang K, Hwang Y, Kim JK, Chae JH, Kim I, Cho B. Epilepsy surgery in children: outcomes and complications. J Neurosurg Pediatrics 1:277–283, 2008 41. Koepp MJ, Labbé C, Richardson MP, Brooks DJ, Van Paesschen W, Cunningham VJ, et al: Regional hippocampal [11C]flumazenil PET in temporal lobe epilepsy with unilateral and bilateral hippocampal sclerosis. Brain 120:1865–1876, 1997 42. Kuzniecky R, Hugg JW, Hetherington H, Butterworth E, Bilir E, Faught E, et al: Relative

1214 Functional Neurosurgery

43. 44. 45. 46. 47.

48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62.

utility of 1H spectroscopic imaging and hippocampal volumetry in the lateralization of mesial temporal lobe epilepsy. Neurology 51:66–71, 1998 Lassonde M, Sauerwein C: Neuropsychological outcome of corpus callosotomy in children and adolescents. J Neurosurg Sci 41:67–73, 1997 Maehara T, Shimizu H: Surgical outcome of corpus callosotomy in patients with drop attacks. Epilepsia 42:67–71, 2001 Mapstone TB. Vagus nerve stimulation: current concepts. Neurosurg Focus 25 (3):E9, 2008 Maton BM, Kuzniecky RI: Proton MRS: N-acetyl aspartate, creatine, and choline. Adv Neurol 83:253–259, 2000 Moore KR, Funke ME, Constantino T, Katzman GL, Lewine JD: Magnetoencephalographically directed review of high spatial-resolution surface-coil MR images improves lesion detection in patients with extratemporal epilepsy. Radiology 225:880 887, 2002 Nolan MA, Sakuta R, Chuang N, Otsubo H, Rutka JT, Snead OC III, et al: Dysembryoplastic neuroepithelial tumors in childhood: long-term outcome and prognostic features. Neurology 62:2270–2276, 2004 O’Brien TJ, So EL, Mullan BP, Hauser MF, Brinkmann BH, Jack CR Jr, et al: Subtraction SPECT co-registered to MRI improves postictal SPECT localization of seizure foci. Neurology 52: 137–146, 1999 Oguni H, Olivier A, Andermann F, Comair J: Anterior callosotomy in the treatment of medically intractable epilepsies: a study of 43 patients with a mean follow-up of 39 months. Ann Neurol 30:357–364, 1991 Papanicolaou AC, Simos PG, Breier JI, Zouridakis G, Willmore LJ, Wheless JW, et al: Magnetoencephalographic mapping of the language-specific cortex. J Neurosurg 90:85–93, 1999 Pugliatti M, Beghi E, Forsgren L, Ekman M, Sobocki P: Estimating the cost of epilepsy in Europe: a review with economic modeling. Epilepsia 48:2224–2233, 2007 Richardson MP, Koepp MJ, Brooks DJ, Duncan JS: 11Cflumazenil PET in neocortical epilepsy. Neurology 51:485–492, 1998 Richardson MP, Koepp MJ, Brooks DJ, Fish DR, Duncan JS: Benzodiazepine receptors in focal epilepsy with cortical dysgenesis: an 11C-flumazenil PET study. Ann Neurol 40:188–198, 1996 Rosenblatt B, Vernet O, Montes JL, Andermann F, Schwartz S, Taylor, LB, et al: Continuous unilateral epileptiform discharge and language delay: effect of functional hemispherectomy on language acquisition. Epilepsia 39:787–792, 1998 Sander JW: The epidemiology of epilepsy revisited. Curr Opin Neurol 16:165–170, 2003 Sillanpää M, Jalava M, Kaleva O, Shinnar S: Long-term prognosis of seizures with onset in childhood. N Engl J Med 338:1715–1722, 1998 Seymour SE, Reuter-Lorenz PA, Gazzaniga MS: The disconnection syndrome. Basic findings reaffirmed. Brain 117:105–115, 1994 Shigeto H, Morioka T, Hisada K, Nishio S, Ishibashi H, Kira D, et al: Feasibility and limitations of magnetoencephalographic detection of epileptic discharges: simultaneous recording of magnetic fields and electrocorticography. Neurol Res 24:531–536, 2002 Sinclair DB, Aronyk K, Snyder T, McKean JDS, Wheatley M, Bhargava R, et al. Pediatric Temporal Lobectomy for Epilepsy Pediatric Neurosurgery 38:195-205, 2003 Sinclair DB, Aronyk K, Snyder T, McKean JDS, Wheatley M, Gross D, et al. Extratemporal resection for childhood epilepsy Pediatric Neurology 30:177-185, 2003 Smith SJ, Andermann F, Villemure JG, Rasmussen TB, Quesney LF: Functional hemispherectomy: EEG findings, spiking from isolated brain postoperatively, and prediction of outcome. Neurology 41:1790–1794, 1991

Epilepsy Surgery in Children

1215

63. Smyth MD, Tubbs RS, Bebin EM, Grabb PA, Blount JP: Complications of chronic vagus nerve stimulation for epilepsy in children. J Neurosurg 99:500–503, 2003 64. Snead OC III: Surgical treatment of medically refractory epilepsy in childhood. Brain Dev 23:199–207, 2001 65. Spencer SS, Spencer DD, Sass K, Westerveld M, Katz A, Mattson R: Anterior, total, and two-stage corpus callosum section: differential and incremental seizure responses. Epilepsia 34:561–567, 1993 66. Stone SD, Rutka JT. Utility of neuronavigation and neuromonitoring in epilepsy surgery. Neurosurg Focus 25 (3):E17, 2008 67. Sugano H, Shimizu H, Sunaga S: Efficacy of intraoperative elec- trocorticography for assessing seizure outcomes in intractable epilepsy patients with temporal-lobe-mass lesions. Seizure 16:120–127, 2007 68. Szelényi A, Joksimovic B, Seifert V: Intraoperative risk of seizures associated with transient direct cortical stimulation in patients with symptomatic epilepsy. J Clin Neurophysiol 24:39–43, 2007 69. Terra-Bustamante VC, Inuzuca LM, Fernandes R, Funayama S, Escorsi-Rosset S, Wichert-Ana L, et al. Temporal lobe epilepsy surgery in children and adolescents: Clinical characteristics and post-surgical outcome. Seizure 14: 274-281, 2005 70. Villemure JG, Mascott CR: Peri-insular hemispherotomy: surgical principles and anatomy. Neurosurgery 37:975–981, 1995 71. Villemure JG, Rasmussen T: Functional hemispherectomy in children. Neuropediatrics 24:53–55, 1993 72. Wheatley BM. Selective amygdalohippocampectomy: the trans-middle temporal gyrus approach. Neurosurg Focus 25 (3):E4, 2008 73. Wheless JW, Maggio V: Vagus nerve stimulation therapy in patients younger than 18 years. Neurology 59 (6 Suppl):S21–S25, 2002 74. Whiting S, Farrell K, Wirrell E: Diseases and syndromes associated with intractable epilepsy. Adv Neurol 97:443–462, 2006 75. Widjaja E, Blaser S, Miller E, Kassner A, Shannon P, Chuang SH, et al: Evaluation of subcortical white matter and deep white matter tracts in malformations of cortical development. Epilepsia 48:1460–1469, 2007 76. Widjaja E, Raybaud C. Advances in neuroimaging in patients with epilepsy. Neurosurg Focus 25 (3):E3, 2008 77. World Health Organization: WHO Revised Global Burden of Disease: 2004 update. 2004 (http://www.who.int/healthinfo/global_burden_disease/GBD_report_2004update_full. pdf) [AccessedOct 2009] 78. Wyllie E: Surgery for catastrophic localization-related epilepsy in infants. Epilepsia 37 (1 Suppl):S22–S25, 1996

Ⅸ. Pediatric Neurosurgery

1218

Past, Present, and Future of Pediatric Neurosurgery MAURICE CHOUX Department of Pediatric Neurosurgery, Hopital La Timone Marseille, France Key words: neurosurgery, pediatric, world, history, future

A BRIEF HISTORY Pediatric Neurosurgery is relatively a recent entity even though any neurosurgeon in the past performed operations in children. Before the 70ths Pediatric Neurosurgery (PN) was performed only by some individuals, in few centres. The very first textbook dealing exclusively with pediatric neurosurgery topics “Brain tumours in infancy and childhood” was published in 1936, by Dandy. The second key textbook dedicated to pediatric neurosurgery was written by Ingraham and Matson, “The Neurosurgery of Infancy and Childhood”, in 1954. Kenneth Till, who died at the age of 88 years, was the first fulltime paediatric neurosurgeon in Great Britain. He published in 1974 a famous book on “Paediatric Neurosurgery”. Between 1960 to 2000 we witnessed the founding of several PN centres or departments, as well as local, regional, national or international paediatric neurosurgical societies. In 1956, Raul Carrea was the director of a pediatric neurosurgical unit in Buenos Aires. We may say; that was the beginning of the concept of pediatric neurosurgery in the world. Bruce Hendrick, followed by Harold Hoffman, created the first independent pediatric neurosurgical department in Toronto in 1964. As mentionned earlier, Kenneth Till was the first full-time paediatric neurosurgeon in Great Britain. After that pediatric neurosurgical units were created all over the world especially in United States and Europe. For instance, currently there are in Europe 4 centres in France, 5 centres in Italy and 5 in United Kingdom. In the last ten years we have observed, in South America, an increased interest for pediatric neurosurgery and the birth of new centres mainly in Argentina and Brazil. In Asia there are pediatric neurosurgical centres in Japan, Korea and in the near future there will be PN centres too in China. But the real problem in developing specialised departments is to be related geographically to a population of appropiate size. This is essential for maintenance of pediatric neurosurgical expertise, for appropriate training in pediatric neurosurgery, for adequate volume and diversity of work in a PN department. This aspect was stressed when we created the International Society for Pediatric Neurosurgery (ISPN) in 1972 with, as one of the recommendation, the necessity to perform a minimum of 250 pediatric neurosurgical operations a year for a proper pediatric neurosurgical department. Adequate hygienic conditions, proper sanitation, fourth generation antibiotics, improved

Past, Present, and Future of Pediatric Neurosurgery

1219

prenatal care, oral contraceptives, amniocentesis and amnioscopy, intrauterine ultrasonography, chemotherapy, intravascular approaches began to change dramatically the flow of CNS pathology. Another aspect is the danger for a pediatric neurosurgeon to be isolated from general neurosurgeons, from other pediatric neurological specialities or from other surgical specialities. The lack of collaboration and absence of instruments and technology represent a major danger. The ideal situation would be; to have a pediatric neurosurgical department in a pediatric hospital, close to a general neurosurgical unit (with functional neurosurgical expertise and technology like neuronavigation), with at least 15 to 30 beds, a staff of 3 people, performing more than 250 operations a year, and with the collaboration of other pediatric specialities (neonatology, neurology, radiology, anesthesiology, intensive care unit, spine surgery, oncology, ophthalmology, endocrinology, ENT surgery ...). We remember the sentence of Kenneth Till in 1996 which said “A contribution to the flowering of pediatric neurosurgery that is often overlooked and underestimated has come to the anesthesiologist. Anesthesiology and Intensice Care Monitoring appear to me one of many examples of the advantages of practising neurosurgery within a children’s hospital where all aspects of care and geared to the special needs of the child”. As a result training in pediatric neurosurgery has become a real challenge in most of the neurosurgical societies. As pointed out by the European Society, it is recognised that for foreseeable future the majority of neurosurgeons involved in pediatric neurosurgery will also undertake significant amounts of adult neurosurgery. Also it is essential that all trainee neurosurgeons must have a minimum of 6 months exposure to pediatric neurosurgical practice. The first International Society was the European Society for Pediatric Neurosurgery (ESPN) created in Vienna in 1967. The ESPN has a congress every two years and the next one will be held in Antalya, Turkey in 2010. Initially the ESPN had an official Journal : “Child’s Nervous System”. It organised regular Post-Graduate Courses, with three annual courses representing a cycle. The first cycle was organised in Marseille by Maurice Choux (1986), the second in Rome by C. Di Rocco (1987), the third in Oslo by K. Hovind (1988). A certificate of attendance is given to trainees who attend the all cycle. The Post-Graduate Courses have carried on since 1986 and the next one, the 7th cycle, will take place in Berlin, in 2010. Another international society is the International Society for Pediatric Neurosurgery (ISPN), founded in 1972, in Chicago by A. Raimondi, R. Carrea, S. Matsumoto, K.Till and M. Choux. It organises an annual meeting, since the first one which took place in 1973, in Tokyo. The 36th meeting will be organized in Korea in 2010.

PN IN THE WORLD Situation of PN in North America. There are 2 Societies including USA and Canada: the Joint Section on PN of AANS and CNS, created in 1970, and the American Society of PN created in 1978. The first Chairman was Anthony Raimondi, one of the most prestigious and pioneer in pediatric neurosurgery. ASPN have meetings twice a year. They

1220 Pediatric Neurosurgery have two Journals: “Pediatric Neurosurgery” and “Journal of Neurosurgery (Pediatrics)”. Situation of PN in South America. The first Department of PN was created in 1956 in Buenos Aires, Argentina, by R. Carrea, a pioneer in PN. There are 2 national societies in Latin-America, in Brazil (1993) and in Mexico (2006). Now PN is well developed mainly in Brazil, Argentina, Chili and Mexico, with pediatric neurosurgeons worldwide recognised such as P. Rueda Franco, Chico Ponce de Leon (Mexico), S. Cavalheiro, H. Machado, F. Salomao, H. Azevedo (Brazil), R. Carrea, J. Monges, G. Zuccaro (Argentina), L. Basauri, S. Valenzuela (Chili). The Federacion Latino Americana de Sociedades de Neurocirugia (FLANC) has since 2000 a PN section with the representation of 19 countries, from South America and Central America. Following the model of the ESPN and since 2004, we organised in South America with C. Sainte-Rose and C. Di Rocco, regular Post-Graduate Courses. In 2009 this course was held in Cordoba (Argentina) and in 2010 it will be organised in Sao Paulo (Brazil). Situation of PN in Europe. Just to remember that the first international PN society was the European Society for Pediatric Neurosurgery created in 1967, in Vienna. The last Congress was organised in Montreux (Switzerland). In Europe there are six national societies: Spain (1984), France (1991), UK, Turkey, Netherlands, and more recently in Russia. Pediatric Neurosurgery groups or parts of National Neurosurgical Societies exist also in Italy, Scandinavia, Switzerland, and Rumania. In France we have an annual PN Society meeting, with 5 pediatric neurosurgical centres in PN and 20 full time paediatric neurosurgeons. The latest was organised in 2009 in Calvi. Next year, the French and Spanish PN Societies will meet together in Las Palma, Canarias Island. Situation of PN in Africa. There is only one exclusive PN department in Africa at the present time (Cape Town), because the number of neurosurgeons is still very low in comparison with other continents. Among 53 African countries, 10 have no neurosurgeon. For a population of 676 millions there are only 500 neurosurgeons: 1: 1.352.000, ( for comparison ; in North America: 1: 81.000, in Europe: 1: 121.000). However, since 95% of growing population will occur in developing countries, there is no doubt that 50% of the population will be below the age of 18 years and inevitably African neurosurgeons will practice Pediatric Neurosurgery daily. The WFNS has been organising regular courses in Africa for the last 5 years. In 2009 two courses were organised, one in Sudan and a second one in Gabon. In 2010, there will be Two WFNS Courses, one in Kenya and the second one in Algeria. The scientific program includes several basic pediatric topics, as hydrocephalus, malformations, infection, trauma. Situation of PN in Asia. The first PN Society in Asia was held in Japan in 1987, it was organised by S. Matsumoto and S. Oi. There is also a Korean PN Society. In India, S. Bhagwati founded a PN Society in 1989, in Mumbay. All pediatric neurosurgeons in India are general neurosurgeons with an interest in PN. In most public institutions there is now a trend towards sub-specialization. In China, the 1st China Pediatric Neurosurgery Forum was organised in september 2008

Past, Present, and Future of Pediatric Neurosurgery

1221

in Shanghai. A Chinese national PN society will be created in a near future. Following the model of the ESPN, since 2004, we organised in Asia with C. Sainte Rose and C. Di Rocco, regular Post-Graduate Courses. The first cycle was organised in Cairns, Australia (2004),and thereafter in Kyoto (2005), in Seoul (2006). The second cycle started in Singapore in 2007, and afterwards in Taipei (2008). What is the future of PN ? Is it desirable for PN to exist worldwide as an independent speciality ? The answer is “yes” but in selected places where neurosurgery is already well established, probably not in most of developing countries. I think that in developing countries, we still need general neurosurgeons interested in PN instead of exclusive pediatric neurosurgeons. In many places we need to train general surgeons and/or pediatric surgeons more than neurosurgeons. Moreover in most of developing countries there is not at present time a crucial necessity to have independent pediatric neurosurgical departments. Centres of excellence in paediatric neurosurgery may be suitable in some places, particularly in some developing countries, where diseases, such as craniopharyngiomas, pineal tumours or craniofacial surgery may be safely investigated, managed, and followed up. The question of the training of pediatric neurosurgeons remains crucial and has become a real challenge in most of the neurosurgical societies. All neurosurgeons in training programs should have experience of key pediatric neurosurgical problems particularly those that may present as an emergency. All neurosurgeons in training will need a minimum of 6 months exposure to pediatric neurosurgical practice. We have always emphasized the necessity in having a wide neurosurgical experience before taking the decision to practice only pediatric neurosurgery. There is a real danger to have an exclusive pediatric training. The relationships between pediatric and adult neurosurgery is clearer than before. We need interaction and cooperation between both, since there is a danger for a pediatric neurosurgeon to be isolated from general neurosurgeons as well as from other pediatric specialities. We need to exchange ideas, opinions but also equipments with general neurosurgeons. If we consider for example Epilepsy Surgery it is reasonable to have in a general hospital a unique neuroscience centre exploring both adult and paediatric epileptic patients. After that pediatric patients candidates for surgery will be operated by the pediatric neurosurgeon. As Di Rocco wrote in 2002:” In substance, we have to educate young neurosurgeons to be Technicians able to deal with all kind of sophisticated surgical procedures and exploit the most modern surgical tools”. The WFNS and PN. Pediatric Neurosurgery has been officially recognized by the WFNS for many years, especially during the presidency of Lindsay Symon. Personally, I was Secretary of the organisation from 1997 to 2001, being full time pediatric neurosurgeon. Moreover, there is a Pediatric Neurosurgery Committee into the WFNS which was chaired by C. Di Rocco for eight years and currently by Tai Ton Wong from Taiwan. Pediatric neurosurgery is part of the Education program and largely incuded in the scientific program of the WFNS Congresses. Pediatric Neurosurgical topics represent 30 to 35% of the program of the WFNS Training courses.

1222 Pediatric Neurosurgery Today’s debate to consider whether PN is a speciality or a subspecialty seems for us over. Paediatric neurosurgery, as C. Di Rocco pointed out in 1993, is after all, neurosurgery applied to children; thus it is substantially different from the other subspecialties as vascular surgery, skull base surgery or stereotactic surgery. Pediatric Neurosurgery has its own criterias and specificities since we know very well that children are not just young adults. It is more convenient and safe to have pediatric patients in a pediatric environment, with pediatric nurses, a pediatric operating theatre, pediatric anesthetists and a pediatric intensive unit.

SOME TOPICS OF PN In order to illustrate the radical changes which occured in the last decades we have selected four main pediatric neurosurgical diseases as hydrocephalus, spinal dysraphic lesions, craniopharyngiomas, and craniosynostosis. Ⅰ) The management of HYDROCEPHALUS has seen significant changes since the first

implanted shunt in 1949. I remember the period in the sixties when an hydrocephalic child was considered as potentially and inevitably disabled patient, not capable to attend a normal school or even to have a proper social or family life. Though, he was having an internal shunt with plenty of mechanical or infectious complications. The families of this hydrocephalic patient were told and they knew that these complications were expected and these associated complications of shunts were considered as a fatality. Fortunately, since 1980 we observed significant progresses in the management of hydrocephalus not only in the decreasing rate of shunts complications but also with the occurrence of alternatives to shunts, mainly endoscopic procedures. In our department as in most of the others departments over the world mechanical complications have diminished dramatically to near zero. Because of the material and especially even the techniques of implantation, complications such as disconnection of catheters, subcutaneous effusion of fluid, exteriorisation of the shunt, misplacement of the ventricular catheter are more and more rarely seen. During our 40 years of shunts experience, we have demonstrated that the main factor to prevent shunt complications was certainly the surgical technique and all the future of the implanted shunt is exclusively related to what happens during the 20 to 30 minutes of shunt procedure. The choice of the material and the etiology are for us of less importance. We tried to demonstrate this fact when we published in 1992 in the Journal of Neurosurgery our protocol for shunt implantation in order to approach a zero infection rate. The reason of changing the rules of shunt implantation in 1983 was when our infection rate was at this time around 9% independently of the age or the etiology. The new protocol started in January 1983 and included the following items:

Past, Present, and Future of Pediatric Neurosurgery

1223

We demonstrated the importance of technical details in shunt procedures, as minimal cranial and abdominal incisions of no more 3 to 4 cm, a minimal bone trepanation, a careful pre-operative selection of the material, a simplest right angle ventricular catheter, without reservoir or connector, a correct ventricular catheter orientation from the occiput to the frontal horn, a single ligature between the ventricular catheter and the valve most of the peritoneal catheters being attached to the valve, an introduction of a long peritoneal catheter (30 to 40 cm) in order to avoid a secondary lengthening the catheter, and a careful skin closure. The length of operation remains an important factor and we think that a shunt may be implanted correctly in 20 to 30 minutes. The number of people in theatre should be limited to four.

1224 Pediatric Neurosurgery In this protocol we do not administer pre or postoperative antibiotics. Only a peroperative intravenous injection of cefamandole (Kefandol) is administed. The choice of the valve remains always controversial since at the present time more than 13O different types of material are available in the market. What are the most important criteria for choosing one valve than another? I remember the conclusion of the “Shunt Book” written by two experts in hydrocephalus; my friends J. Drake and C. Sainte Rose in 1995: “At this time, there is no shunt system or device which has been scientifically proven to be superior to any other”. I Approve totally their conclusion, for me the most important criteria in the selection of a shunt remains its cost, not only for developing countries. In this aspect the Foundation of the WFNS has sponsored since 2007 an economical shunt, the Chhabra Shunt manufactured by an Indian Company for a cost of 35 USD. A recent paper by B.C. Warf published in JN (Pediatrics) in 2005, concluded that there was no stastically significant differences in the outcome for patients treated with the Chhabra or a Codman-Hakim shunt system, in 195 children, in Uganda. Moreover we have been interested for many years in the management of hydrocephalus in developing world because the incidence of hydrocephalus is decreasing in developed countries due to prenatal diagnosis, while it has been increasing in developing countries. This is to demographical factors in favour of high pediatric population and the lack of prenatal diagnosis. Once I discussed with my friend Adeloye in Africa, in 2001, about how to improve the management of hydrocephalus in Sub-Saharan Africa; he made few interesting suggestions: 1) Early diagnosis and prompt treatment, 2) Improvement in the quality of local shunts, 3) Increase number of “hydrocephalus surgeons”, 4) Development of endoscopic third ventriculostomy. Unquestionable progresses have been made in the last 20 years in the management of hydrocephalus with shunts when we look at our series of 1400 cases with a follow-up of more than 10 years: there were no revision in 34,8 % of the cases, only one revision in 30,2 % and several revisions in 35 %. That means that 65 % of the patients had no more than 1 revision in the 10 years following a shunt implantation. In this aspect a shunt implantation must be considered as a major intervention and not a secondary or small procedure done by the youngest resident, when major operations have been achieved at the end of the day. We should not forget that a patient with hydrocephalus is initially neurologically and intellectually intact, in most of the cases. A correct treatment of his hydrocephalus without complications will preserve his normal condition. Alternatives to shunts represent other crucial changes in the approach of the management of hydrocephalus. We know now that a definitive internal shunt may be avoided in more than 30 to 35 % of the cases. By treating the cause of hydrocephalus a shunt is no longer necessary in case of brain tumour or cyst. In case of a posterior fosse tumour with symptomatic hydrocephalus an endoscopic third ventriculostomy is performed as first step, and by doing that we avoid an internal shunt routinely. Even more in case of a shunt inserted before the tumour removal we try to remove it thereafter, few weeks later.

Past, Present, and Future of Pediatric Neurosurgery

1225

Another alternative to shunt is external drainage, mostly in case of tumours, haemorrhage or infection. By following the same protocol, we found that the infection rate is not higher for external drainage than for an internal shunt. Endoscopic approaches represent the main progress we have observed in the treatment of hydrocephalus, not only as an initial procedure but also in case of revision. We know now that this technique may be used in patients younger than one year and that it can be repeated. The complications rate is less and less encountered due to a better technique and better indications. A special training for endoscopic procedures is of paramount importance for everyone. Ⅱ) The second category of lesion that represents one of the main controversial diseases

in pediatric neurosurgery is the OCCULT SPINAL DYSRAPHIC LESIONS. With the progress of antenatal diagnosis we have observed in the last two decades, especially in developed countries, a significant shift in the distribution of dysraphic lesions; the frequency of myelomeningoceles has decreased significantly to zero in several countries. Anomalies as spinal lymphomas or malformations of the spinal cord or roots are now of a major interest for a pediatric neurosurgeons. In the Pediatric Neurosurgical Department in Marseille the distribution is as follow: 1) Lipomas : 208 cases 2) Anomalies of Spinal cord and roots : 59 - Thick filum, adhesions and bands : 36 - Split cord malformations : 23 3) Malformations of meninges : 33 - Intrasacral meningoceles : 9 - Posterior meningoceles : 20 - Intradural-Extradural cysts : 5 4) Myelocystoceles : 6 5) Dermal Sinus – Dermoid cysts: 29 6) Neuroenteric cysts : 9 1) Lipomas represent near 60 % of occult dysraphic lesions. Age distribution shows that now a significant proportion of lipomas may be detected at birth, on the presence of a minor cutaneous stigmata and despite an absence of clinical manifestations. The majority were diagnosed under the age of 2. Clinical presentation is a cutaneous sign in 94 % of the cases, an orthopaedic problem in 34 %, a urological manifestation in 70 % and neurological sign in only 20 %. In neonates and infants the diagnosis is normally made on skin anomalies, some of them very minimal, and in toddler or adults on urological, orthopaedic or neurological manifestations. For the indications for surgery, there are four possibilities: 1) In neonates and infants presenting exclusively with skin anomalies, with no or mild orthopaedic, neurological or sphincter anomalies, a « prophylactic surgery » remains controversial for some authors. We are in favour of an early surgery to

1226 Pediatric Neurosurgery prevent secondary or late clinical deterioration. Other authors are clearly against surgery in asymptomatic patients and they prefer to wait looking for a possible clinical deterioration. 2) In infants or children with urinary or neurological anomalies, surgery is mandatory, even if we know that urinary or orthopaedic signs rarely regress after surgery. Currently the main reason for unfettering the spinal cord is essentially to stabilize the clinical condition of the patient, than to improve the symptoms. 3) In adolescents or adults, with a cutaneous anomaly alone, we prefer to wait since surgical procedures may be more hazardous. New symptoms may occur after surgery. 4) In adolescents or in adults presenting new clinical symptoms, surgery will be advocated in relation to the severity of the symptoms and clinical signs. There are, according to our experience, three types of Spinal Lipomas : 1) Extradural Lipoma. 2) Intradural Lipoma : a) Lipoma of the filum b) Intramedullary lipoma 3) Extra and Intradural Lipoma : a) Dorsal lipoma b) Caudal Lipoma A) In case of Lipoma of the filum terminale (fibrolipoma, filar lipoma) surgery is easy and consists, after a one or two level laminotomy, of cutting and removing the lipomatous filum for about two cm. In young children, at the end of the procedure, the conus may ascend for a few mm. B) In Caudal lipoma (caudal variant,caudal type) the lipomatous mass is attached to the caudal part of the conus medullaris. Surgical technique is relatively simple and untethering is achieved by dividing the lipoma below the transitional zone, avoiding the neural elements. After the division of the lipoma the cord may shows a remarkable ascent. C) In Lipomyelomeningocele the interface between the lipoma and the conus is not always easily visible. There is always a defect of the dura in the dorsal midline which corresponds to the external aspect of the lipoma-cord interface. In this type, surgery is more difficult and complex. Removal of the lipoma may be achieved using scissors, ultrasonic aspiration or CO2 laser. It is not necessary to pursue the residual lipoma into the cord. The goal is to separate the spinal cord from the more superficial lipomatous mass. The late postoperative outcome shows an improvement in more than 70 % of the cases and a secondary worsening in 5 to 6 %. Finally, the purpose of surgery is to prevent or to stabilize the symptoms. 2) Anomalies of Spinal Cord and Roots (59 cases). A tethered cord with a thick filum may be easily treated by a surgical section. A split cord malformation raise more complicated questions, related with surgical indications and technical problems. Removal of the bony spur and reconstruction of a dural sac are mandatory but surgery may be complicated in extensive malformations.

Past, Present, and Future of Pediatric Neurosurgery

1227

3) Malformations of meninges (33 cases). Intrasacral meningoceles may be diagnosed late in the life and symptoms are often progressive. Some of them are very large with an anterior development (anterior sacral meningoceles), needing a surgical cooperation with a pediatric surgeon. 4) Myelocystoceles (6 cases) are rare lesions and must be distinguished from posterior meningocele, since surgery may be more risky in myelocystoceles. 5) Dermal sinus and Dermoid cysts (29 cases). The first manifestation may be meningitis and a large surgical removal of the dermoid cyst and the tract until the vertebral canal is indispensable in all the cases. Sometimes the diagnosis may be late since the cutaneous fistula remains unapparent. 6) Neuroenteric cysts (9 cases). In this complex malformation there is a communication between the spinal cord and a cyst lined by gastrointestinal mucosa. Spinal neurenteric cysts must be excised radically including the intraspinal connections (rectum, vagina…) Ⅲ) The third example which demonstrates the changes in our philosophy is the initial

management of CRANIOPHARYNGIOMA in children. It still remains controversial, since more than a century. It must be carefully considered and discussed since a wrong initial decision may have definitive and irreversible consequences. The 1980s represents the decade of enthusiasm for craniopharyngioma surgery and we were, with H. Hoffman, F.Epstein, JF Hirsch or C. Di Rocco, prone for radical removal. In 1991, we published a monograph where we collected 474 pediatric cases studied by members of the ISPN. We presented our personal experience of 108 cases of craniopharyngiomas in patients under the age of 16, managed since the MR era and with a minimal follow-up of 8 years. After this “gross total resection” period, we saw a change in the acceptance of postoperative consequences of surgery, mainly endocrine disorders. What was considered for many years as acceptable and inevitable complications can no longer be accepted now. Following the recent opinion of C. Sainte-Rose, as a swinging pendulum we moved from aggressive to conservative treatment. The initial management of craniopharyngioma depends on the age of the patient, the clinical manifestations, and the anatomical type of the tumour and the personal expertise of the neurosurgeon. There are peculiarities of pediatric craniopharyngiomas, which are of adamantinomatous type, their huge size, a frequent obstructive hydrocephalus and a higher recurrence rate. The initial decision must be adapted to the initial clinical manifestations. The management must cure the ICP symptoms and the ophthalmological signs. But also it must avoid a worsening of minimal endocrine symptoms or creation of new endocrine deficits. The majority (55%) of craniopharyngiomas are of mixed type and 36 % are cystic, allowing sometimes an initial endoscopic approach, allowing to empty a cyst and preparing the surgical resection. Craniopharyngiomas are rare tumours. Therefore one needs expertise in this field, with an adequate number of cases annually, an

1228 Pediatric Neurosurgery interdisciplinary cooperation and a good knowledge of the different treatment options. 1) A surgical approach of the craniopharyngioma, either total or subtotal, remains the first step in most of the cases. We must consider carefully the anatomical relationships of the tumour with the hypothalamus, the optic pathways, the pituitary stalk, the brain stem, the vessels or the dura. The consequences of a large removal of the tumour are well known, mainly severe post-operative endocrine disorders, at time associated with hypothalamic dysfunction. Obesity, gross mental retardation and diabete insipidus remain major endocrinal problems after surgery. Moreover all the preoperative endocrine symptoms are aggravated after surgery. In our experience a total removal may be possible in 70 % of the cases, even if the recurrence rate remains as high as 20 %.But after a so-called radical removal the recurrence rate is between 15% to 38% in the recent literature. We agree with Tomita conclusion who in 2005 wrote that “because of the often unacceptably high complications rates and the lack of 100% prevention of recurrence following radical tumour resection, there has been a growing advocacy for less invasive tumour resection with adjuvant therapy”. 1) Endoscopic approach represents now an interesting way in the management of this tumor. 2) There is no indication for conventional radiation at the pediatric age. Only Three Dimensional Conformal radiation may be delivered, after an incomplete removal or in case of recurrence. Recently, Proton therapy has been promoted with promising results. 3) An other interesting alternative treatment is stereotactic anthracitic injection of radioactive agents, as Phosphorus 32, Rhenium 186, Yttrium 90, or Interferon. 4) Chemotherapy with intracystic injection of Bleomycin through a catheter was used in our department since 1991. Positive results in near 40 % of the cases have been published by one of our resident from Brazil in 2005. 5) A Stereotactic Radiosurgery, rarely indicated as initial option, may be useful for recurrent lesions or in case of residual tumour. In a cooperative study achieved in the radiosurgical department by J. Régis, 49 cases of craniopharyngiomas were treated by radiosurgery. The results were considered as a success in 21, a tumour controlled in 16 and a failure in 7. These different options may be used as isolated or in combination. Whatever the option, the main and the major risk in children remains a Recurrence. Therefore the selection of treatment options must be put in balance between the clinical consequences of each option and the risk of recurrence. A child without or with minimal significant ophthalmological deterioration, or without or with minimal endocrinological deficit, will be managed in a different way than a child with more severe visual or endocrine symptoms. Each craniopharyngioma must be considered individually, especially in children. The initial clinical symptomatology remains the key point which will determine the choice

Past, Present, and Future of Pediatric Neurosurgery

1229

of the best initial management. It seems for us a great progress to have different treatment options in the management of a craniopharyngioma since quality of life must remain the goal of our decision. Finally the danger in case of craniopharyngioma at the time of the initial decision is to be dogmatic. Ⅳ) The Surgical management of CRANIO-FACIAL anomalies is also an example of the extraordinary changes which have occurred in the recent years. The first surgical approaches of craniosynostosis were described at the beginning of the last century and at this time near all the cases were mentioned as oxycephaly. A revolution came in 1967 when Paul Tessier, a plastic surgeon, published his famous article on “Total facial osteotomy: Crouzon’s syndrome, Apert’s Syndrome, oxycephaly, scaphocephaly, turricephaly” in Annales de Chirurgie Plastique. He was the first who mentioned the necessity to consider the skull and the face as an entity, in case of surgical treatment. He clearly described the criteria for selecting craniofacial surgery: the type of malformation, its degree of monstrosity, the existence of mental retardation and whether the child will enter to school, the family situation, the risks of vital function, the functional risks, the severity of operation, the resources of bone grafts and lastly the experience acquired by a team working together. These criteria remain still valid today. The craniofacial team includes a neurosurgeon, a plastic surgeon, a neuroanesthetist, an intensive care unit, a pediatric neuroradiologist, an orthodontist and dentist, a ENT surgeon, an ophthalmologist, a geneticist, a pediatrician and a speech therapist. Only in few centres such a group of specialists may be concentrated in the same place. The British Society of Neurosurgery pointed out in 1998 that the minimum population required for a major Crania-Facial Unit should be around 8 million. The solution could be to have Centres of excellence where all types of craniofacial diseases would be safely managed. Expertise in craniofacial surgery implies not only a team but also to perform a sufficient number of cases a year, we may say a minimum of 30 cases of different types and ages. For craniofacial anomalies, investigations include standard X-rays, Bi-dimensional CT, MRI and 3D reconstruction (Shaded Surface Display and Volume Rendering). A surgical planning may be done with the aid of a three-dimensional computer. We cannot ignore that an increased Intracranial Pressure may exist in some types of craniosynostosis for example Brachycephaly, Oxycephaly, Crouzon disease or Apert Syndrome, but ICP monitoring remains indicated in very few cases. Genetic studies are indispensable in the initial investigations and they became part of the routine investigation. Reasons for surgery are mainly cosmetic factors, psychological and social factors, and functionnal factors: symptoms of raised intracranial pressure , ophthalmological manifestations, and malocclusion of the mouth or nasopharyngeal obstruction. Do we need to operate all craniosynostosis ? The answer is certainly not. In our series 63% of scaphocephalies, 85 % of plagiocephalies, 64 % of trigonocephalies and 64 % of oxycephalies were operated on. We know that in case of occipital asymmetrical deformation the cause is a positional molding in more than 80 % of the cases. Consequently surgical indications are exceptional and the correction can be obtained in few months by an helmet. The timing for surgery is essential. We have seen an interesting historical evolution with

1230 Pediatric Neurosurgery a surgical correction done generally after one year of age before 1965, an earlier surgery, before 6 months and sometimes during the first year, from 1970 until 1980, while now we are waiting until 6 to 8 months. Anesthesiological problems are well known and better controlled, such as positioning, blood loss, hypothermia, hypotension, air embolism, and brain edema. The reasons of possible complications are the duration of surgery and the low weight of most of the patients. Again, we have to mention the importance of having anaesthetists and intensivists familiar with this type of surgery. Technically, we have witnessed important improvements in the recent years, on the skin incisions, less blood loss, different material for osteosynthesis : from silk, nylon or metallic ligatures to absorbable plates and screws or abssorbable material with ultrasonic rivet. Minimally invasive endoscopic techniques have been introduced since 1995, especially for scaphocephaly. Two or four short incisions allow the removal a sagittal piece of bone from the coronal level to the lambdoid level. The advantages are a possible shorter and safer operation, a low cost, less blood loss and a less hospital stay. We use this technique now quite routinely in case of scaphocephaly. In Crouzon disease the fronto-orbital advancement must be done in the first months after life. The facial advancement (Lefort II or III) must be done ideally at the age of 10 to 12. Now with Distraction techniques introduced by Renier and Marchac in 1995 an earlier correction of the face is possible in the first years of life. This Distraction may be external or better internal. The danger or risk of complications of facial advancement with a distractor is much less important than it was at the time of complex surgical advancement type Lefort III. I have no doubt that we will see in a near future the development of distraction techniques for other types of craniosynostosis. Ⅴ) The management of POSTERIOR FOSSA TUMORS,

These are the most frequent and typical tumors at the pediatric age, and they remains very challenging. They represent 55 to 60 % of intracranial tumors in children. Most of the complications occurring during the first steps of the treatment are related to the surgical approach itself. It represents the first and initial step in the management of a posterior fossa tumor, and not only for histological purpose. This is valid for the following lesions : Cerebellar Astrocytoma, Medulloblastoma or Ependymoma. That is also true in 30 to 40 % of the Brain Stem lesions. The quality and the extent of the surgical resection remain the significant prognostic factor, equally in benign cerebellar astrocytoma as in medulloblastoma or ependymoma. A minimal morbidity after the surgical approach is essential prior a post-operative oncological treatment. We present our experience in a series of 810 cases of Posterior Fossa Tumors in patients under the age of 16 Years. 1) In case of an associated Hydrocephalus, which occur in 82 % of the case, one must decide the real need for a preoperative shunt and what drainage may be implanted. A routine preoperative shunting must be avoided as much as possible, especially an internal one. The presence of Increased intracranial pressure can be well controlled with steroids. Nevertheless, in rare cases,

Past, Present, and Future of Pediatric Neurosurgery

1231

especially in very young patients or in severe and acute hydrocephalus, a preoperative shunting procedure may be necessary, either by an external drainage which will be kept for few days after the posterior fossa surgery, or a ventriculo-peritoneal shunt which will be removed few weeks later. It is desirable to avoid as much as possible to keep a drainage for life when the tumor has actually ben removed. Currently, a Preoperative Endoscopic Third Ventriculostomy remains for us the best choice to control hydrocephalus. It is effective in 82 % of the cases and reduces the frequency of secondary hydrocephalus. 2) Considering the Posterior Fossa approach itself, some surgical principles are important to keep in mind : a) Positionning of the child : we use routinely a prone position, at any age and despite the upwards extension of the lesion. For an anesthesiological point of view the prone position, especially in neonates or infants, remains less problematic. b) Suboccipital Craniotomy versus craniectomy : the craniotomy is preferable and avoids the usual suboccipital bulging observed in patients operated upon for posterior fossa lesion. A craniotomy allows to gain time and is bloodless. c) Resection of the posterior arch of C1 : there is no need to resect it routinely. d) Opening of the dura : it will be adapted to the localisation of the tumor and to the presence or absence of intracranial hypertension. If no shunt has been inserted previously we recommend to start the dura opening at the cervical level, where some CSF may be drained out first. e) Preservation of the arachnoid layers : the cisterna magna will be preserved intact as much as possible. f) Retraction of the cerebellum : retractors may be the cause of cerebellar infarction and must be avoided as much as possible, particularly the self retaining ones. g) A total removal must be the goal of surgery. Surgical Microscope, Ultrasonic aspiration, and if available per-operative Evoked Potentials are useful tools to achieve this target. Cerebellar astrocytomas, which are of benign pilocytic types, are curable lesions following a complete excision (possible in 86 % of the cases), including the solid portion of the lesion (mural tumor) and the removal of the cystic tumoral capsule when a contrast enhancement has been demonstrated on CTScan or MRI. With a radical excision a secondary radiation therapy is never necessary in this category of tumor. In case of residual after a perceived total removal, we can wait and follow the evolution which may be very slow. Excellent results have been achieved in 84 % of the cases. In Medulloblastoma surgery is mandatory too.The removal must be as large as possible, without injuring the floor of the IVth ventricle. A radical excision is possible in more than 80 % of the cases. Adhesions or infiltration to the brain stem (present in 33 % of medulloblastomas) must be left behind and not dissected, to prevent severe morbidity. A 10 years survival rate remains the same whether you perform a 90 or a 100 % excision. It appears clearly in most of the protocols that the quality of the surgery is one

1232 Pediatric Neurosurgery of the main prognostic factor. An incomplete excision or a biopsy has no place in this type of tumours. Surgical mortality (the first 30 days) is 3,5% in our series. Oncological treatment must commence immediately after surgery with Chemotherapy. Many protocols are available ( Carboplatin + VP 16, 8/1 protocol, Vincristin-CCNUPrednisone, Vincristine-CCNU-Cisplatin ....), but we recommend to insert chemotherapy between surgery and radiation therapy (Sandwich therapy). Post-operative radiation is mandatory (tumour field : 55 GY, cranial field : 25 GY, spinal field : 23-25 GY). We do not give radiation in children under the age of 5 years. We have done significant progresses in the management of medulloblastoma in the recent years and the 8 years survival is now 66 % in most of the centres. Local recurrences may be treated with radiosurgery while supratentorial or spinal recurrences will be managed with chemotherapy/radiotherapy. In case of ependymoma, which represents 11 to 12 % of posterior fossa, radical removal is the best prognostic factor. There are three anatomical types of ependymomas (Ikezaki, 1993) : 1) Mid-floor Ependymoma located in the midline with a possible extension in the cervical canal. 2) Lateral type with a tumour extending into the IV ventricle, the lateral recess and the pontine angle. 3) The Roof type with a tumour located in the roof of the IV ventricle. The possibilities of surgical removal and the survival rates are significantly different for each type. The 5 yr and 10 yr survival rates are respectively: 66,7 %- 66,7 %, 20,8%-0%, 100%-100%. That means that at 10 years no patient with a lateral type ependymoma will survive. In the contrary all the patients with a roof type ependymoma will be alive. Chemotherapy is not effective and radiation therapy is indicated in malignant forms. Recurrences must be treated by repeated surgery. We have had the case of a 4 years old boy who survived after 8 repeated surgical procedures. In Brain Stem tumors (214 cases), the extent of surgery will be tailored to MRI aspects,operative considerations and the histology. There are mainly four types of tumors : Type I : Intrinsic tumor, diffuse, hypodense on CT, low intensity in T1, with no or minor significant enhancement. Surgery is not indicated, only radiation and Chemotherapy may be indicated. The 5 years survival remains very poor. We do not recommend stereotactic biopsy since the management will not change whatever the histology. Type II : Intrinsic and focal tumor, which may be solid or cystic. Surgery is indicated in all cases since most of these lesions are benign. 8 years survival is around 72 %. Type III : Exophytic tumor, either dorsally or laterally. They are benign lesions which can be surgically removed; 8 years survival is 75 %. Type IV : Bulbo-medullary tumor. They are mostly benign and may be cured by surgery alone, with a 8 years survival of 77%. The management and the prognosis are drastically different for each category of tumours. With modern surgical techniques and a better preoperative evaluation, a more

Past, Present, and Future of Pediatric Neurosurgery

1233

aggressive approach in localised or benign brain stem lesions must be advocated. h) The closure remains an important step of the procedure : absence of local complication improve significantly the quality of the results and diminish the delay between surgery and a possible oncological treatment In the majority of Posterior Fossa Tumors, Surgery is the first, the indispensable step of the management, as well as an important prognostic Factor. With modern techniques in anesthesiology and surgery the postoperative mortality rate tends towards zero and the morbidity has decreased significantly in the last decades.

CONCLUSION In conclusion, we want to emphasize one point. Confronted with a neurosurgical disease in a child, the pediatric neurosurgeon is part of a trilogy, the two others being the patient and the parents. These cannot be ignored at the time of the discussion preceding a surgical decision. The discussion with the parents must be done in the presence of the patient when he/she has an acceptable age. We need to spend time with them in order to explain step by step what can be proposed in order to be understood correctly. We have to keep in mind that parents are not doctors and did not know the exact significance of medical terminology. Sometimes they know what they have read through the internet a day before and the informations they have at their disposal are basic and incomplete. This discussion must be done in an isolated room, the parents seated, without being interrupted by a mobile phone or other people. Showing the radiological investigations or a simple drawing may be very useful. The parents have the impression to be involved in the discussion and to actively participate to the decision. A correct preparation of the parents is generally followed by a better follow-up, especially in cases of severe or complex case. We do not hesitate to meet again the parents if necessary. There are peculiar circumstances which needs special explanations, such as a child presenting with a craniosynostosis at birth. In this case we have to explain to the parents that an operation is indicated only for cosmetic reasons, in absence of clinical signs. The parents will argue that surgery is not mandatory since there are no clinical risks and that cosmetic indications are not essential in a small child. We have to explain that the craniofacial deformation if not corrected will affect the psychological and behavioural development of their child at school or in the family life. This complicity between the patient, the parents and the pediatric neurosurgeon is one of the most the fascinating part of our job. A pediatric neurosurgeon is finally a general neurosurgeon with a specific interest and expertise in pediatric neurosurgery. In some places he will be dedicated exclusively to this type of surgery and in other places he will be dedicated only partially. For the young neurosurgeons who want to embrace exclusively or partially pediatric neurosurgery, here is the list of books dedicated to pediatric neurosurgery : “Pediatric Neurosurgery : Surgery of the Developing Nervous System”, R. Mc Laurin (1982), “Pediatric Neurosurgery”, A. Raimondi (1987), “Atlas of Pediatric Neurosurgery”, W. Cheek (1996), “Pediatric Neurosurgery”, M. Choux, C. Di Rocco, A. Hockley, M. Walker (1999), “Operative Techniques in Pediatric Neurosurgery” , L. Albright (2000),

1234 Pediatric Neurosurgery “Pediatric Neurosurgery”, D. Mc Lone (2000), “Paediatric Neurosurgery : a Handbook for the Multidisciplinary Team”, L. May (2001), “Principles and Practice of Pediatric Neurosurgery”, L. Albright (2008), “Pediatric Neurosurgery (Neurosurgical Operative Atlas”, J. Goodrich (2008), Some books are more dedicated on specific pediatric diseases as : “Cranial haemorrhage in the Full-term”, Govaert, (1993), “Vascular Diseases in Neonates, Infants and Children”, P. Lasjaunias (1997), “The Shunt Book”, J. Drake, C. Sainte-Rose (1995), “Pediatric hydrocephalus” G. Cinalli, V. Maixner, C. Sainte-Rose (2004), “Surgery of the Pediatric Spine”, D. Kim (2008), “Pediatric Epilepsy Surgery”, O. Cataltepe, G. Jallo (2010), “Pediatric CNS Tumors”, N. Gupta (2004), “Atlas of Pediatric Brain Tumors”, A. Adesina, T. Tihar, T. Y. Poussaint (2010), “Fetal and Neonatal Neurology and Neurosurgery”, The role and the importance of nursing care in pediatric neurosurgery are emphasized in the following volumes : “Paediatric Neurosurgery for Nurses : Evidence-Bases care for children families”, Joanna Smith –Catherine Martin, (2008), “Nursing care of the Pediatric Neurosurgery patient”, C. Wallace (2007).

1235

Arachnoid cysts CONCEZIO DI ROCCO, LUCA D’ANGELO, LUCA MASSIMI Pediatric Neurosurgery – A. Gemelli Hospital, Rome, Italy Key words: arachnoid cyst, Galassi classification, false arachnoid cyst, interhemispheric cyst, intraventricular arachnoid cyst

Arachnoid cysts (ACs) are congenital fluid-filled compartments that do not communicate with the normal subarachnoid spaces and develop within the arachnoid membrane. They are believed to depend on a splitting or duplication of this structure. These cysts should be differentiated by “secondary” or “false” arachnoid cysts that are acquired accumulation of cerebrospinal fluid characterized by the presence of inflammatory cells and hemosiderin deposits within the delimiting membranes, which result from the inflammatory loculation of the subarachnoid space after head injury, infection or hemorrhage. Moreover, ACs differ from other cysts communicating with the natural pathways of the CSF circulation, such as dilated cisterns, arachnoid pouches and poroencephalic cavities. ACs represent 0.1-0.5 % of all nontraumatic intracranial mass lesions. The mean age of presentation is during the first two decades of life. A male prevalence is reported. ACs involve the Sylvian fissure/middle fossa in nearly a half of cases, while the CP angle, the quadrigeminal cistern, the retrocerebellar area, and the sellar/suprasellar region are affected in 10% of cases, respectively. Less commonly, ACs are located within the interhemispheric fissure, the cerebral convexity, the prepontine cistern, the cervicomedullary junction. Even more rare are the ACs which develop within the cerebral ventricles or in the spinal compartment. Arachnoid cyst of intracranial compartment varies from a few centimeters in diameter to huge sacs causing significant distortion and displacement of the nervous structures. They may remain stable along many years or progressively enlarge exerting mass effect on adjacent neural structures. Although very rarely, their spontaneous decrease in size and even their disappearance have been described, probably following spontaneous or traumatic rupture. In other instances, such an event may result in subdural hygromas or hematomas. Clinical manifestations depend on the location; consequently they may be quite specific but also non-specific. The middle cranial fossa is the most commonly affected supratentorial region. In such a region, ACs frequently increase in size up to open the fissure and to expose the insula and middle cerebral artery. Though clinical manifestations can occur at any age, Sylvian fissure ACs become symptomatic mainly during childhood and adolescence. Headache is the most common presenting symptom, followed by proptosis, controlateral motor weakness, epilepsy and signs of increased intracranial pressure. Cognitive impairment and developmental delay are common in children with large lesions. Asymmetrical macrocrania is frequently found in neonates while a focal bulging of the skull in the temporal region can be detected by standard X-rays in

1236 Pediatric Neurosurgery children. On CT-scan, these cysts appear as non-contrast-enhancing CSF-density fluid collections; the bone-scan easily reveals the possible associated bulging and thinning of temporal squama as well the anterior displacement of the sphenoid bone wings. According to Galassi and collegues, Sylvian ACs can be classified into three subgroups: Type 1 cysts (Fig. 56.1a,b) are small, biconvex, or semicircular, and are confined to the anterior aspect of the temporal fossa (temporal pole), without mass effect; Type 2 cysts (Fig. 56.1c,d) are medium-sized, triangular or quadrangular lesions with frequent but moderate mass effect, involving the anterior and middle portions of the temporal fossa and causing the opening of the Sylvian fissure; Type 3 cysts (Fig. 56.1e,f) are large, roundish or oval-shaped; they occupy the middle cranial fossa entirely, and determine severe mass effect on the surrounding structures with controlateral ventricular displacement and shift of the midline.

Fig. 56.1 T2-weighted axial (a) and coronal (b) MR images showing a Silvian fissure arachnoid cyst confined to the anterior aspect of the temporal fossa (Galassi type I); T1-weighted axial (c) and sagittal (d), revealing a type II Silvian fissure arachnoid cyst with quadrangularshaped opening of the Silvian fissure; T1weighted axial (e) and T2-weighted coronal (f) MR images showing a type III arachnoid cyst occupying the middle cranial fossa entirely and extending over the entire cerebral hemisphere.

Arachnoid cysts

1237

MR imaging provides details about the three-dimensional relationships of the cysts that appear as non-enhancing CSF-isointense collections. Angio-MRI reveals the position of the branches of middle cerebral artery and cortical veins, that may be relevant when planning the surgical treatment. PET and SPECT are useful in evaluating the cerebral metabolism and blood flow in the brain tissue surrounding the cyst. EEG points out the presence of seizure foci or areas of focal slowing. These functional studies, together with ICP monitoring, are important for the surgical indication, when these cysts are incidentally demonstrated in subjects who had undergone neuroimaging examination for other reasons (e.g. head injury, psychomotor retardation). Cysto-peritoneal and less frequently, cysto-venous shunting have been the commonly utilized surgical option for this type of cysts. Such option has proved to be effective in reducing the cyst volume and allowing the optimal brain expansion. However, the relatively frequent occurrence of shunt-dependancy, pseudotumor-like episodes and the development of Chiari type I malformation have progressively decreased the neurosurgeons’ enthusiasm. Furthermore, shunting procedures are weighted by a high rate of complications (early: intracyst or subdural hemorrhage due to injuring of bridging veins during the catheter insertion; late: infections, malfunctions, cyst reaccumulation and low-pressure headache). Nowadays, open and endoscopic fenestration of the cyst lining into the basal cisterns are considered the procedure of choice. The craniotomic approach is usually realized through a minicraniotomy centered on the cyst that allows the resection of the lateral cyst wall and fenestration into the basal cisterns of the mesial and basal membranes (Fig. 56.2). The risks of open fenestrations are mainly post-operative subdural hygromas ( 5% of the cases) and the occurrence of hydrocephalus due to the possible associate impairment of CSF dynamics. Endoscopic fenestration currently offers the advantages of poorly invasiveness and short operative time even though it’s burdened by the same risk of postoperative subdural fluid collection than open microscopic fenestration as well as by a higher risk of massive intraoperative bleeding and postoperative subdural hygroma.

Fig. 56.2 Intra-operative images (open surgery) of a middle fossa arachnoid cyst: after the resection of the lateral wall of the cyst (a), the carotid artery and the optic nerve become evident (b,c). The fenestrations (arrows) of the medial wall into the basal cisterns allows to visualize the oculomotor nerve and the main arterial trunks (d).

1238 Pediatric Neurosurgery ACs of the chiasmatic region are generally divided in intrasellar and suprasellar cysts. Typical of adulthood, intrasellar ACs are different from the so-called “empty sella” or intrasellar diverticula. Generally, the diagnosis is incidental; headache is the most common complaint. Treatment consists of transphenoidal drainage followed by reconstruction of the floor of the sella turcica. Suprasellar cysts (Fig. 56.3) are common in the pediatric population, 50% of them being diagnosed in children younger than 5 years. The most common signs and/or symptoms are hydrocephalus, vision impairment and endocrinologic dysfunction. Gait ataxia and Ophischotonus are associated to very large cysts displacing the midbrain posteriorly. The “bobble-head doll” syndrome is a rare but typical maninfestation due to compression on the third ventricle and on the dorsomedial nucleus of the thalamus. Ultrasonography and CT scan identify a cystic, smooth, oval or round lesion in the suprasellar region; MRI better define the lesion and its relationships with the surrounding structures, thus allowing the differential diagnosis with other cystic lesion such as Rathke’s cleft cysts, cystic craniopharingiomas and epidermoid cysts. Surgical treatment of suprasellar ACs should consider the frequently associated hydrocephalus although it generally disappears following the reduction in size of the cyst. Open excision/fenestration has been practically abandoned in favor of endoscopic treatment. The direct shunting of the cyst, though safe and effective surgical procedure, has been also abandoned because its high percentage of failure due to a improper placement of the cranial catheter, when stereotactic techniques and ultrasonography were not available. Endoscopic fenestration of suprasellar arachnoid cyst into ventricular system (ventriculocystostomy) and basal cisterns (cystocisternostomy) or both is the treatment of choice. When performing the endoscopic treatment it is mandatory to open both the superior and inferior cyst walls and to explore and eventually perforate the arachnoid membrane which can impair CSF flow with the prepontine cystern, namely the Lilliquist membrane.

Fig. 56.3 T1-weighted axial (a) and sagittal (b) MR images showing a large suprasellar arachnoid cyst pushing the mesencephalon posteriorly and superiorly and elevating the corpus callosum. The lateral cerebral ventricles are only moderately dilated.

Arachnoid cysts

1239

ACs of cerebral convexity are classified in two main variants: hemispherical cysts, which are huge fluid collection extending over most or all of the surface of one cerebral hemisphere, compressing the brain parenchyma and dislocating the lateral ventricle; and focal cysts (Fig. 56.4), which usually produce a localized bulging of the skull. Clinical manifestations differ between pediatric and adult population. In the pediatric patients, focal bulging of the skull or cranial asymmetry without neurological deficits are the most frequent presenting signs. In adults, ACs are often revealed by signs of intracranial hypertension, epilepsy and neurological deficits. Craniotomy that exposes the lesion widely in order to perform an extensive excision of the outer membrane and to make an additional opening into other arachnoid spaces has demonstrated scarcely effective and weighted by a high rate of complication. Currently, cysto-peritoneal shunt is the mostly utilized surgical option, often adopting externally pressure-regulated valve, in order to achieve a progressive detention of the cystic cavity and, hopefully, cerebral parenchyma expansion.

Fig. 56.4 T2-weighted coronal (a) and axial (b,c) MR images of a focal arachnoid cyst of the frontal cerebral convexity producing a localized bulging of the skull.

Interemispheric cysts (Fig. 56.5) represent about 5-8 % of all ACs; they can be distinguished in interhemispherical and parasagittal cysts according to the presence or absence of a normal falx and the partial or complete agenesis of the corpus callosum. Macrocrania is the most common presenting sign; however, clinical manifestations of increased intracranial pressure are present in only about two thirds of cases. Hydrocephalus is relatively common in association to interhemispherical cysts. The surgical treatment included open surgical fenestration and shunt placement. Nowadays, also for this type of cyst, endoscopy represents the most effective and safe surgical option. Due to their location, ACs of the quadrigeminal plate (Fig. 56.6) region frequently cause hydrocephalus (occlusion of the acqueduct), paresis of up-gaze and pupillary dysfunction (compression of the tectal plate), visual field changes (compression of the genicolate body), limb weakness and gait ataxia (brainstem-cerebellar impairment), bilateral deafness (damage of the inferior colliculus), and seizures (compression on the temporal lobe). The differential diagnosis between arachnoid cysts and other congenital or acquired cystic malformation can be hard to obtain. MRI is the diagnostic gold-

1240 Pediatric Neurosurgery standard, being able to reveal the relationships with the posterior recess of the third ventricle, the brainstem and the Galen’s vein system. The treatment include CP shunt placement or, more commonly, endoscopic fenestration.

Fig. 56.5 T1-weighted axial MR images revealing a parasagittal (a) and an interhemispherical (b) arachnoid cyst.

Fig. 56.6 Radiological picture of arachnoid cyst of the quadrigeminal plate: a,b: T1-weighted axial MRI; c,d: T2weighted coronal and T1-weighted sagittal MRI.

Arachnoid cysts

1241

Intraventricular ACs (Fig. 56.7) are rare, but increasingly recognized in early age cysts, which develop within the ventricular system, probably from ectopic arachnoid remnants. These cysts cause ventricular distortion and enlargement as well as hydrocephalus, in several instances. They are easily treated by endoscopic fenestration into the ventricular cavity.

Fig. 56.7 T1-weighted sagittal (a), and axial (b) and T2-weighted axial view (c) of an intraventricular arachnoid cyst.

Infratentorial ACs are much less common than supratentorial cysts. Posterior cranial fossa ACs (Fig. 56.8) are classified in two main variants: the midline cysts, which push the vermis anteriorly separating the two cerebellar hemispheres, and the laterally located cysts, overlying and compressing only one cerebellar hemisphere. Macrocrania and other signs of raised intracranial pressure are the most common clinical manifestation because of the compression and distortion of the neural structures of the posterior fossa and the following hydrocephalus. Even though MR images and CT scan make the diagnosis of cerebellar cysts relatively easy, the differential diagnosis with other cystic malformations is often difficult. The absence of a communication with the subarachnoid spaces is the main characteristic that distinguish an arachnoyd cyst from Dandy-Walker malformation, mega cisterna magna and Blake’s pouch. The surgical options include craniotomy with excision of the cyst membrane and shunt device placement. Despite the good results of open surgery in terms of disappearance of the lesion and cerebellar re-expansion, the recurrence of the lesion or the appearance of postoperative hydrocephalus are not exceptional events. Postoperative hydrocephalus is probably due to an underlying impairment of cerebrospinal fluid dynamics which can be further enhanced by the scarring process following the posterior fossa craniotomy. Nowadays, most surgeons prefer to use an endoscopic procedure for opening the cyst in the cisterna magna or within the ventricular system.

1242 Pediatric Neurosurgery

Fig. 56.8 T1-weighted axial (a) and sagittal (b) MR images of a left posterior fossa arachnoid cyst dislocating and compressing the cerebellum and causing a supratentorial hydrocephalus.

Fig. 56.9 MR images showing an arachnoid cyst of the right cerebellopontine angle (a: T2- weighted axial view; b: T1-weighted axial view; c: T1-weighted sagittal view; d: T2-weighted coronal view).

Arachnoid cysts

1243

Cerebellopontine angle ACs (Fig. 56.9) are very rare lesions generally found in adulthood. The clinical manifestations include cochlea-vestibular dysfunction, cerebellar signs, fifth and seventh cranial nerve deficits. The papillary edema observed even in absence of hydrocephalus is probably due to the impairment of CSF flow within the basal cisterns. The best surgical treatment is the excision of the lesion. Spinal ACs (Fig. 56.10) are relatively uncommon lesions which originate from the arachnoid of the spinal cord extending to the sheaths of the spinal nerve roots. They cause symptoms and signs of spinal cord compression. The treatment of choice is the surgical fenestration into the subarachnoid spaces at the superior and inferior pole of the cyst.

Fig. 56.10 T2-weighted sagittal (a), axial (b) cuts and T1-weighted axial cut (c) showing a cervico-thoracic arachnoid cyst compressing the spinal cord anteriorly (arrows).

REFERENCES 1. Di Rocco C (1996) Arachnoid cysts. In Youmans JR (eds) Neurological surgery, Ed 4., Philadelfia: WB Saunders, pp 967-994. 2. Galassi E, Piazza G (1980) Arachnoid cysts of the middle cranial fossa: A clinical and radiological study of 25 cases treated surgically. Surg Neurol. 14:211-2119. 3. Oberbauer RW, Haase J, Pucher R (1992) Arachnoid cysts in children: A European cooperative study. Childs Nerv Syst. 8: 940-944.

1244

Developmental Anomalies of the Central Nervous system CHENG KIANG LEE and WAN TEW SEOW National Neuroscience Institute and KK Women’s & Children’s Hospital, SINGAPORE Key words: embryology, arachnoid cyst, CNS development, dysrathism

CRANIAL LESIONS ARACHNOID CYSTS Arachnoid cysts are fluid filled collections lined by arachnoid membrane within the cerebrospinal fluid cisterns. The fluid is similar in appearance and density to cerebrospinal fluid. It is believed to arise from splitting of the arachnoid membrane as it delaminates from the overlying dura during development. Arachnoid cysts may be classified according to location. 75% are supratentorial in location while the remainder are infratentorial. Sylvian fissure arachnoid cysts, on the whole, make up the majority of cysts accounting for up to 50%, the rest are located in the quadrigeminal or suprasellar regions. Convexity and interhemispheric arachnoid cysts occur less commonly accounting for 10% or less of intracranial cysts. Infratentorial cysts may be located in the cerebellopontine angle, vermian or retroclival region.

Fig. 1 Left Sylvian fissure arachnoid cyst (T2 MRI)

Developmental Anomalies of the Central Nervous system

1245

The wall of the cyst is arachnoid membrane and the fluid compartment is believed to be largely static. Some cysts however enlarge with time and it is believed that this due to CSF secretion from choroids plexus cells or neuroepithelium within the cyst wall. Alternatively, a ball valve mechanism may be responsible provided the cysts communicate with the surrounding subarachnoid space. Overall the incidence of arachnoid cysts is believed to be less than 1%. Some cysts are associated with agenesis of the corpus callosum. The majority of arachnoid cysts are asymptomatic and stay dormant with minimal or no increase in size with time. When they do become symptomatic, the clinical presentation is usually in the form of raised intracranial pressure with resultant headache, nausea and vomiting, seizures or local mass effect depending on the location. Trauma may cause haemorrhage into the cyst resulting in sudden neurological deterioration. They are sometimes associated with psychomotor retardation with delayed milestones. On imaging, these cysts have smooth margins which do not enhance with contrast. The fluid density is similar to that of cerebrospinal fluid. No surgical management is required for asymptomatic arachnoid cysts which are not causing significant mass effect. They should be observed with regular follow up. Regular imaging is not necessary unless symptoms occur. Symptomatic arachnoid cysts may be treated with either one of three ways: 1. Open craniotomy and cyst aspiration, cyst wall excision and/or fenestration into subarachnoid space. 2. Endoscopic cyst aspiration and fenestration into subarachnoid space 3. Cyst-peritoneal shunt The method would depend on surgeon preference as well as on the location of the cyst.

DANDY WALKER MALFORMATION The Dandy Walker malformation is recognized when the following 3 features are present 1. Cystic dilatation of the 4th ventricle 2. Partial or complete absence of the cerebellar vermis 3. Hydrocephalus Hydrocephalus may not be present at the time of initial diagnosis. Other pathological features commonly seen in the Dandy-Walker malformation include enlargement of the posterior fossa with elevation of the transverse sinus, and obstruction of the foramina of Luschka and Magendie.

1246 Pediatric Neurosurgery

Fig. 2 Axial CT of Dandy-Walker malformation (left) and saggital T1 MRI of Dandy-Walker malformation (right). Note the enlarged posterior fossa on the saggital view.

The pathological basis of this condition is not fully understood, though it is generally believed to involve mal-development of cerebrospinal fluid outlets within the 4th ventricle. The overall incidence is approximately one in 30,000 live births. A number of congenital anomalies involving the central nervous system are associated with this syndrome, namely, agenesis of the corpus callosum, occipital encephalocele, aqueductal stenosis and cerebral or cerebellar heterotopias. Systemic anomalies involving the skin (hemangioma), musculoskeletal (hypoplastic limbs), and cardiovascular system (septal defects), are also frequently observed. Clinical presentation of these patients comprise the following 1. Macrosomia 2. Psychomotor developmental delay/Mental retardation 3. Ataxia 4. Spasticity 5. Cranial nerve and ocular abnormalities MRI is the imaging modality of choice. Treatment would involve shunting the cyst. If hydrocephalus persists, then a ventriculo-peritoneal shunt is also inserted.

ENCEPHALOCELES An encephalocele is formed when intracranial contents herniate out from its normal

Developmental Anomalies of the Central Nervous system

1247

confines of the skull, usually through a defect in the skull. The actual pathological basis is not known. In general, premature growth arrest of surrounding confining tissue or early herniation of intracranial contents preventing closure of skull tissue have been proposed. Encephaloceles are not neural tube closure defects (the neural tube defect equivalent of spinal bifida is anenecephaly). Encephaloceles are classified based on location. In general there are 6 main categories - occipital, occipital-cervical, parietal, temporal, sincipital (fronto-ethmoidal) and basal. For simplicity, the first 4 categories may be classified as posterior encephaloceles and the last 2 categories as anterior encephaloceles. Posterior encephaloceles appear as lumps or swellings arising from the cranial vault whereas the anterior encephaloceles present as swellings arising from the facial region in particular, para-orbital region for the fronto-ethmoidal encephaloceles or in the nasal cavity for basal encephaloceles.

Fig. 3 Occipital encephalocele (left) and fronto-ethmoidal encephalocele (right).

Diagnosis may be made prenatally on routine ultrasound. Amniocentesis if performed will demonstrate raised alpha-fetoprotein. MR imaging is the imaging study of choice as it details the contents of the encephalocele, its relationship to surrounding structures and presence of other structural abnormalities such as hydrocephalus or arachnoid cysts. Distinction between a sincipital or fronto-ethmoidal encephalocele (where the defect lies anterior to the cribriform plate) and basal encephalocele (where defect is through the cribriform plate or sphenoid bone) is important as the basal encephalocele by virtue of its location may contain or lie in close proximity to vital structures of the suprasellar or sellar region. The aims of surgery are to excise the sac along with any dysplastic neural tissue, to preserve any remaining normal neural tissue and to achieve water-tight dural closure and skin cover. Large skull defects may be covered with split calvarial bone grafts. Surgery is done urgently if there are signs of cerebrospinal fluid leak, skin ulceration or impending breakdown or hemorrhage. In the case of fronto-ethmoidal or basal encephaloceles, the

1248 Pediatric Neurosurgery threat to visual development (encephalocele covering the eyes) or the airway respectively, are important considerations and any potential compromise would warrant urgent surgical correction. With fronto-ethmoidal encephaloceles, a combined approach involving a frontal craniotomy and local repair of the lesion is preferred because of the high risk of recurrence when only local repair is performed.

CHIARI MALFORMATION The term is named after Hans Chiari, an Austrian pathologist who classified hindbrain malformations into 4 types based on his autopsy study of 40 patients in the late 1800’s. The malformations are described as followsType 1 Caudal descent of the cerebellar tonsils below the foramen magnum (generally taken as more than 5mm). There is an association with syringomyelia.

Fig. 4 Saggital T1 MRI showing a Chiari Type 1 malformation and syringomyelia

Type 2 Caudal descent of the cerebellar vermis, brainstem and 4th ventricle below the foramen magnum. Type 2 Chiari malformations are associated with myelomeningocele and hydrocephalus. Type 3 Occipital cervical encephalocele Type 4 Cerebellar hyoplasia or aplasia Pathogenesis The pathogenesis of Chiari malformations is not well understood. It remains to be proven whether Type 1 to 4 Chiari malformations represent a continuous spectrum of disease or whether they are distinct separate entities. Theories were initially put forth by Gardner and further elaborated by Williams and a unified theory relating the development of Chiari 2 malformation and myelomeningocele has been suggested. The latter essentially attributes the hindbrain abnormality to a lack of cranial

Developmental Anomalies of the Central Nervous system

1249

cerebrospinal fluid pressure caused by leakage from the open central neurocanal in the myelomeningocele, thereby resulting in a lack of distension and caudal herniation of the hindbrain. Type 1 Chiari malformation can occur secondarily following lumboperitoneal shunting and are sometimes seen in association with low grade tumours of the cerebellum. Chiari Type 1 and 2 malformations will be discussed as they are of greater clinical importance. Type 3 and 4 malformations are rare and surgical intervention often not feasible.

Chiari Type 1 malformation Findings Patients tend to present in older children and in adulthood. Symptoms and signs are due any one of the following - hydrocephalus, syringomyelia, brain stem compression. Headache aggravated by valsalva maneouvre is a characteristic finding, such as that seen in cough headache. Sensory changes from associated syringomyelia typically occur in a cape distribution and is dissociated in nature (i.e. loss of pain and temperature sensation with preservation of light touch, vibration and proprioception). Motor signs include atrophy of the small muscles of the hand, weakness and spasticity of the upper and lower limbs. Down beat nystagmus is a classic finding. Cerebellar signs may also be present. In children, a Chiari Type 1 may be found during MR imaging when investigating scoliosis. They can also be found incidentally on MRI done for headaches which are not necessarily related to the Chiari 1 malformation. The imaging modality of choice is MRI. The posterior fossa will appear shallow and tight. In addition to noting caudal descent of the cerebellar tonsil, look out for hydrocephalus and basilar impression. Syringomyelia and less so, syringobulbia, are frequent findings. Management Surgery is indicated in patients who are symptomatic. If there is concurrent hydrocephalus, the patient should be shunted first and observed for any improvement in symptoms. If symptoms remain, then surgery of the Chiari malformation is indicated. The aim of surgery is to achieve decompression at the foramen magnum. This is done via an occipital craniectomy down to the level of the foramen magnum. An expansion duroplasty is also performed after inspecting and surgical lysis of any dural arachnoid adhesions at the skull base. The decision whether or not to remove the posterior arch of C1 lies with the inferior limit of tonsillar descent. Should the tonsils descend to or below the level of C1, then its posterior arch should be removed as well. If there is a syrinx present at time of presentation then this should be followed up after surgery with the expectation that it should resolve after a few months. Persistence of the syrinx would require a thorough re-evaluation of the patient to exclude secondary causes as well as a consideration to re-explore the posterior fossa. Shunting of the syrinx would be an option should all else fail.

1250 Pediatric Neurosurgery

Chiari Type 2 malformation Findings TheType 2 Chiari malformation usually presents in infancy and is associated with myelomeningocele and hydrocephalus. Symptoms and signs relate to compression of the herniated medulla by the herniated cerebellar tonsils in the upper cervical canal. Apnoea, poor gag reflex, dysphagia, weak cry, nystagmus, inspiratory stridor and opisthotonic posturing are some of the signs to look out for. MR imaging will show a variety of features, including a small and shallow posterior fossa, hydrocephalus, prominent massa intermedia, agenesis of corpus callosum, agenesis of septum pellucidum, polygyria, interdigitation of occipital and parietal lobes, fusion of the midbrain colliculi to form a single peak (tectal beaking) and cervico-medullary kinking. Skull x-rays and CT will show presence of craniolacunia (copper beaten skull). Management Surgery is indicated for symptomatic patients. One important point is to ensure that the shunt is functioning before attributing symptoms to the Chiari II malformation. In infants, only cervical laminectomy down to the inferior limit of the tonsils is sufficient as the medullary compression occurs in the upper cervical canal and there are usually venous lakes present in the dura of the posterior fossa, making duroplasty of the posterior cranial fossa hazardous.

SPINAL LESIONS SPINAL DYSRAPHISM In essence, spinal dysraphic states arise from a failure of fusion of dorsal midline structures of the back during embryological development. Development of the spinal cord occurs between day 18 to day 48 of gestation. Primary neurulation (between day 18 and day 28) consists of separation of the neuroectoderm from the neural plate and lateral infolding of the neuroectoderm, resulting in formation of the spinal cord. Following this, the cutaneous portion of the neuroectoderm also separates and fuses in the midline to form the overlying skin. Mesoderm migrates between the cutaneous ectoderm and neuroectoderm to form the posterior vertebral arch, back musculature and subcutaneous tissue. Secondary neurulation (canalisation) occurs from day 28 and involves the formation of the caudal cell mass at the caudal end of the spinal cord. This mass ultimately differentiates into neural, genitourinary and notochordal structures. The last phase occurs from day 41 and is termed retrogressive differentiation. The caudal spinal cord regresses to form a filum terminale with the conus ending at L2. There is an association between antenatal folate deficiency and spinal dysraphism. As such, women who are planning a pregnancy should consume 0.4 mg a day of folate, before they become pregnant. This should be increased to 0.6mg per day once they become pregnant. Women at high risk for spinal dysraphism should consume 4mg per

Developmental Anomalies of the Central Nervous system

1251

day before and during pregnancy. High risk factors are that of a positive family history i.e. history of previous pregnancy with spinal dysraphism or a partner who has the condition, obesity, use of anti-convulsants (valproate or carbamazepine) and Diabetes type 1. The following are a list of spinal dysraphic statesMyelomeningocele Lipoma of the conus medullaris (lipomyelomeningocele) Occult spinal dysraphism Split cord malformation (diastematomyelia and diplomyelia) Dermoid sinus tract Lipoma of the filum terminale Meningocele Limited dorsal myeloschisis Myelocystocele Terminal syringomyelia Neurenteric cyst

Myelomeningocele Myelomeningocele is the commonest form of spinal dysraphism with an incidence of about 1 per 1000 live births. It is a herniation of a meningeal lined sac containing neural structures through a defect in the posterior elements of the vertebrae. This condition typically presents during routine antenatal ultrasound. Upon delivery, it is important to assess the child’s neurological status, paying particular attention to lower limb function. The sac and its covering should also be inspected. A full systems examination to look for associated genitourinary or gastrointestinal abnormalities is warranted. This condition is frequently associated with hydrocephalus and Chiari Type 2 malformation. An MRI of the affected spinal region along with the brain to look for hydrocephalus is carried out and early surgical excision of the sac and closure of the defect (within 72 hours) is then planned. The operation is done early so as to reduce the chance of

Fig. 5 Typical myelomeningocele with neural placode seen in the middle, surrounded by arachnoid membrane and skin.

1252 Pediatric Neurosurgery central nervous system infection. When hydrocephalus is present, repair should be carried out first and a ventriculo-peritoneal shunt is inserted at the same sitting or a few days later. Subsequent care involves a multidisciplinary approach involving the orthopaedic and urological subspecialities, as well as the paediatrician and medical social worker.

Lipoma of the conus medullaris (lipomyelomeningocele) A lumbosacral spinal lipoma or lipoma of the conus medullaris is less common compared to myelomeningocele. This condition is often evident at birth. A soft subcutaneous mass is seen and felt in the lumbosacral region. Overlying cutaneous stigmata may also be present such as cutaneous hemangiomas, hypertrichosis, skin tags or dermal dimples. The underlying problem in this condition is tethering of the cord as it is attached to a fibrofatty lipoma which may be situated dorsally, at its caudal end or both dorsally and caudally. As a result of cord tethering, neurological deficits affecting the lower limb function, bladder and bowel continence develop with time, especially during growth spurts. Some children have foot deformities such as pes cavus and/or neurogenic bladder at birth. Pain is also a feature in the growing child. A scoliosis may also become evident as the child grows. Initial ultrasound examination may reveal a low lying conus medullaris associated with a soft tissue mass. MRI is confirmatory and it typically shows a low lying conus medullaris associated with a fatty mass (high signal intensity on T1 weighted imaging). MRI is useful as it provides further detail as to the position of the lipoma cord interface in relation to the cauda equina nerve roots. This is helpful when planning for surgery.

Fig. 6 Subcutaneous lipoma with skin tag in a patient with a lipoma (left) whose saggital T1 MRI of the lumbar spine shows a lipoma of the conus medullaris (right)

Developmental Anomalies of the Central Nervous system

1253

Patients who are symptomatic and show signs require surgery. Asymptomatic infants upon confirmation of diagnosis are also surgical candidates. Surgery for asymptomatic patients should be done as early as possible, before onset of symptoms. Surgery involves microsurgical dissection of the lipoma from the lipoma-cord interface, detethering the cord from the usually thickened and short filum terminale, preservation of functioning uninvolved nerve roots, use of a dural graft to replace the deficient dura and enlarge the thecal sac with water-tight dural reconstruction and skin closure. In the event that a scoliosis is present, surgical detethering is accomplished before and spinal surgery for scoliosis correction

Other lesions causing tethering of the spinal cord The occult spinal dysraphisms are so called because they have a layer of intact skin overlying the spinal defect. Cutaneous stigmata will raise our index of suspicion when these patients present. The important thing is to obtain a full history and examine these patients with a focus on the neurological, urinary and orthopedic systems. The most common occult dysraphic lesion seen in the tethered spinal cord is the lipoma of the filum terminale.

Fig. 7 Cutaneous stigmata heralding occult spinal bifida: trichosis (left), dimple with skin tag (middle) and dystrophic skin patch (right)

When presenting shortly after delivery a lumbosacral ultrasound would be useful as a screening procedure. Further confirmation is achieved through MRI. The lesion may then be defined and appropriate surgical action planned with the aim of detethering the spinal cord and relief of any mass effect.

Lipoma of the filum terminale Typically this lesion is seen on MRI as a bright linear structure and especially on T1 axial views, where it is seen as a bright round dot. There is a strong association with anorectal malformations, presumably because they share the same embryologic origin - the caudal cell mass. A low lying cord is seen on the screening ultrasound of the lumbar spine and confirmed on MRI. Surgical detethering of the spinal cord is easily performed via a midline laminotomy, performed by partially removing the adjacent superior and inferior laminae at a segment below the conus. The

1254 Pediatric Neurosurgery

Fig. 8 Saggital and axial T1 images of the lumbar spine. The bright dot on the T1 axial scan is diagnostic of a lipoma of the filum terminale.

dura is then opened and the lipomatous filum is visualised as a round, translucent light yellowish fatty structure, different in colour and texture from adjacent the nerves of the cauda equina. It is then divided after small nerve roots are dissected off the fatty filum and bipolar diathermy is applied to cauterize any blood vessel present in the filum.

REFERENCES 1. Atlas of Neurosurgical Techniques: Spine and Peripheral Nerves. Richard G Fessler and Laligam Sekhar. Thieme 2006. 2. Operative Techniques in Pediatric Neurosurgery. Leland Albright, Ian F. Pollack, P. David Adelson. Thieme 2000. 3. Principles and Practice of Pediatric Neurosurgery. Leland Albright, Ian Pollack, and P. Adelson. Thieme 2007. 4. Youman’s Neurological Surgery. H. Richard Winn. Saunders. 5th edition 2004.

1255

Pediatric Neurosurgery TAKAYUKI INAGAKI Kansai Medical university, Osaka, Japan Key words: pediatric neurosurgery, hydrocephalus, CSF shunt, endoscopic third ventriculostomy

Pediatric neurosurgery is now considered to be one of the well established subspecialties of neurosurgery. The children should not be considered as a small adults. Anything that affects one member of the family affects the whole family, especially if the affected member is the child. So that multidisciplinary team approach would be required to treat children. Fortunately children suffer from fewer neurosurgical diseases than adults. This is one reason why there are fewer pediatric neurosurgical departments throughout the world. Thus it is important to communicate and share the knowledge worldwide. In this chapter, the basic knowledge, a young neurosurgeons needs to know will be discussed.

1. Hydrocephalus Introduction Pediatric hydrocephalus occurs at a rate of approximately 0.9/1000 children [1]. Data from population-based study in Sweden suggest that the incidence of infantile hydrocephalus ranges from 0.48 to 0.63 per 1000 live births. [2] The cerebrospinal fluid (CSF) is mainly secreted from the choroid plexus. Brain itself is also believed to be responsible for a small fraction of total CSF production. CSF reabsorption is a purely passive process driven by the pressure difference between the CSF and the venous compartment. The hydrocephalus is a disturbance of this CSF physiology. Hydrocephalus could also be a result of intracranial infection, intraventricular hemorrhage or brain tumor. Hydrocephalus is in general caused by a disturbance in CSF (cerebrospinal fluid) circulation, or due to a problem with the absorption. The classic concept of hydrocephalus is characterized by increased intracranial pressure, dilatation of the CSF pathways, increased CSF volume. There are two main factors that determine the outcome of a child with hydrocephalus. First, hydrocephalus affects the brain functionally and morphologically. Neuronal development and myelination of the brain are disturbed in varying degrees, depending on the time of onset of hydrocephalus – particularly in the fetal and infantile states of development. The better outcomes will be obtained by shortening the time after the disease onset and the time from the onset to the surgical treatment. Second,

1256 Pediatric Neurosurgery hydrocephalus may be present concomitantly with primary brain damage, or it may actually be caused by primary brain damage. It is apparent that progressive or prolonged enlargement of the ventricles concurrent with only mild increases in intracranial pressure could damage the brain [3]. The periventricular white matter in patients with hydrocephalus is edematous and usually sustains axonal damage and demyelination, which may be irreversible. The grey matter exhibits disorientation and dendritic deterioration, although most of these cells do not die until the late stages of hydrocephalus. Cortical connectivity is impaired. Also diminished metabolism and membrane turnover has been suggested during the acute stage of hydrocephalus [4]. Early intervention and treatment of hydrocephalus is therefore expected to be more beneficial, but in some of the cases even early treatment might not be possible to reverse the discussed above pathophysilogical changes.

Clinical evaluation Diagnostication may start during the intrauterine development, but more commonly it begins on the first assessment and examination of the child. The typical appearance of a baby with hydrocephalus includes increasing head circumference and bulging fontanelle, poor feedings or vomiting is also common. Sunsetting eyes, dilated scalp viens and drowsiness will follow. The older children will display symptoms of headache and vomiting, along with papilloedema. Clinically, those children show lethargy, poor school performance and developmental delay.

Legend: sunsetting phenomenon observed in the patient with hydranencephaly.

Neuroimaging Diagnosis may be established with ultrasonography before the parturition. The premature baby may have an ultrasonography performed through the anterior fontanelle, providing information for the ratio of ventricular size/cerebral cortex, and thus the diagnosis of hydrocephalus may be established. Ultrasonography is very useful tool for evaluation of the changes of the size of ventricle in small children. Either CT and/or MRI are also useful tools. Fetus hydrocephalus is examined with MRI as well as ultorasonography. With the advent of MRI itself and software, one sequence can be done within a few seconds.

Pediatric Neurosurgery

1257

Legend: T1 weighted sagittal and axial MRI images showed congenital hydrocephalus. In this case, ventricular dilation was treated with V-P shunt.

Classification Pathophysiology of hydrocephalus is not well understood, yet, because of the lack of knowledge of CSF production and absorption. There are well accepted classifications. 1. Overproduction of CSF: choroid plexus papilloma and choroid plexus carcinomas are included in this group. These are rare form of hydrocephalus. 2. Disorders of CSF circulation: this is a group of disorder in which the path of CSF circulation is obstructed. The obstruction may be inside the ventricles or in the subarachnoid space. Tumors, hemorrhage, congenital malformation such as aqueductal stenosis, and infections could cause the obstruction. 3. Disorders that cause CSF mallabsorption into the venous system. Hydrocephalus can also be divided in two group based on the patency of CSF pathways. Respecting this we could define two types: one is obstructive (noncommunicationg) hydrocephalus; the other is non-obstructive (communicating) hydrocephalus. Hydrocephalus is also classified into acute and chronic hydrocephalus based on the period between the occurrence of the symptoms and the onset of the disease.

Treatment Children that present with ventricular dilatation and clinically evident elevated intracranial pressure require a CSF diversion procedure. While the conventional CSF shunting have been the main treatment for a long period of time, with the advent of modern endoscopic instruments, the endoscopic management of CSF diversion is another option of treatment.

1258 Pediatric Neurosurgery

Shunt system SCF shunts regulate flow by means of one-way valves. The standard valves that have been in use for decades simply open or close depending on the pressure across them. They can be grouped into four general design categories; silicon rubber slit valves, silicon rubber diaphragm valves, silicon rubber mitre valves, and metallic spring and ball valves. The pressure at which they open is termed the opening pressure, and typically there are low, medium, and high designations that generally correspond to 5,10,15mm of Hg pressure; but there are not universal standards. Once open standard differential pressure valves will let large quantities of CSF through the shunt. The peritoneal catheter is at approximately atmospheric pressure, whereas the negative pressure inside the head equals the height of the column of CSF minus the valve opening pressure. When the patient is standing, the height of the column of CSF will greatly exceed the valve opening pressure leading to siphoning of CSF

This scheme shows the siphoning effect in shunted patients. Theoretically, valve dynamics predominate in the lying position, on the other hand hydrostatic effect predominate in the upright position. The siphoning effect is strong, in other words, if the CSF is flowing through the shunt system more quickly than the ability of the brain to expand, the subdural fluid collection, secondary synostosis and slit ventricle syndromes may occur.

Pediatric Neurosurgery

1259

into the abdomen. Complications such as low pressure headaches and subdural hematomas are sometimes the result of this negative intracraniasl pressure. Other valve designs have tried to limit this siphoning effect. Siphon-reducing deveices have a mobile membrane that moves to narrow an orifice in response to a negative pressure inside the shunt system. Examples include separate components that can be added to exisiting shunt systems. Flow-limiting valves incorporate a flexible diaphragm that moves along a piston of increasing diameter. Resistance to flow is dramatically increased by the reduced orifice, resulting in minimal flow increases despite raising the pressure differential-essentially a flow limit. Programmable shunt devices can be used in many countries now.

Shunt selection There is no sufficient data to recommend one particular shunt over another. Randamaized trial on CSF shunt design that compared a standard differential pressure valve with both siphon-limiting and flow limiting valves failed to show any difference in terms of overall shunt failure. [5] However, there are important consideratons to be taken into account when considering the individual patient. These include age, wight , skin thickness, head size, size of the ventricles, pahthogenesis of hydrocephalus, the stage of the disease, the presence of concomitant diseases or presence of gastrostomy, tracheostomy, status of the distal drainage site, and plans for further surgery. Metallic shunt components, or magnetic programmable valves should be avoided in patients expected to require multiple MRI studies, to avoid degradation of the images and unnecessary reprogramming of the valve.

Shunt operation The aim of the shunt is to drain CSF for reabsorbtion from the ventricles to an extracranial part of the body . Among the all neurosurgical procedures shunt surgery has the highest failure rate. It is well known that shunts frequently fail because of tissue occluding the proximal or distal catheter. However, avoidable complications such as intraparenchymal ventricular catheters, expraperitoneal distal catheters, and spontaneously disconnected or migrated shunts have occurred on virtually every neurosurgical institute. Shunt surgery should command great respect, require meticulous attentions to detail, and be carried out in a skilled and expeditious fashion. Body wash and shampoo the night before and before surgery with antiseptic solution is recommended. A number of meta-analysis have shown that prophylactic antibiotics are effective. [6] The ventricle to peritoneal shunt remains the optimal choice as peritoneal membrane is highly permeable and possible to easily absorb the CSF. A ventricular-atrial shunt is used when the abdominal cavity is not appropriate because of previous abdominal surgery or infection.

1260 Pediatric Neurosurgery

Legend: Position of the patient and incisions for ventriculo-peritoneal shunt Patient is positioned supine on the table with the head rotated to the opposite side. The head is extended with putting rolled towel under the neck to ensure as straight a line of passage as possible from the abdomen to the occipital area.

Lumbar-peritoneal shunt for small children is not recommended because of the increased chance of acquired Chiari malformation. The patient should be positioned so there is a flat plane between the upper and lower incision sites, facilitating subcutaneous passage, with rotating the head to the opposite side and extending the neck, usually with a rolled towel. The issue of frontal versus occipital burr hole controversy has never been resolved. [7] Occipital burr holes are usually on the flat part of the occiput 3 to 4 cm from the midline along the course of the lambdoid suture. In patients with Dnady-walker mafmormation or large arachnoid cysts of the posterior fossa, the transverse sinus can be placed much higher than in normal subjects. In these patients the position of the transverse sinus should be identified preoperatively by MRI and the placement of the burr holoe modified accordingly. Frontal burr holes are generally placed along the coronal suture 2 to 3 cm from the midline. Anterior burr hole placement may be preferable when endoscopic catheter placement or other procedures. The skin is meticulously prepped with a iodine solution. Disposable drapes are used to cover entirely the patient and the operating table, except for a small band of skin from the burr hole site to the abdomen. Small skin incisions are adequate and generally preferable. They are carefully planned to avoid placement over subsequent underlying hardware. The burr hole need not be a standard size, and a twist drill is adequate unless using a burr hole reservoir or intraoperative ultrasonography in infants, particularly if they are premature, an opening between the splayed coronal or lambdoid sutures is all that is required. The dura should not be opened widely, particularly in patients with thinned cortical mantles, where a wide dural opening may allow CSF to escape around the ventricular catheter into the subcutaneous tissues, promoting a CSF leak and subsequent infection. Low –power monopolar coagulation applied to a small brain needles or bayoneted forceps will create a dural opening sufficient for the typical ventricular catheter. The pia matter is carefully cauterized and cut with a fine-tipped bipolar forceps or small tipped knife.

Pediatric Neurosurgery

1261

The abdominal incision could be simultaneously performed. The method and site of insertion are not a matter of a great importance. Even though we prefer paraumbilical incision, upper midline sites are also oftenly used. When performing an open laparotomy, the peritoneum is elevated and sharply incised to avoid abdominal organs injury. To verify that the peritoneum has been truly opened, and not just the pre-peritoneal space, a blunt instrument is passed deeply into the abdominal cavity. A purse-string suture around the peritoneum tends to prevent omentum from herniating but is not absolutely necessary. Care must be taken when tunneling. If the metal tube is too deep, the chest or even the posterior fossa can be entered. If the tunneling is too superficial, then a skin laceration can occur. A gentle curve to the tunneling instrument allows one to direct the tip posteriorly when coming over the anterior chest into the neck. Significant resistance is usually felt at the posterior nuchal line. In some cases, a separate incision in the neck is necessary. Likewise, passing to a frontal burr hole usually requires an additional incision over the occiput. The peritoneal catheter, with or without the attached valve, is then passed through the tunneling device. Care is taken to avoid contact between the shunt and the patients’s skin as well as the surgeon’s gloves by using instruments and clean gauze to handle components and covering incision with additional sterile towels. The valve should then be attached and irrigated to fill it with fluid. Care must be taken to ensure that the valve is inserted in the proper orientation and lies flat beneath the scalp. The ventricular catheter trajectory is then determined according to external landmarks. From a frontal burr hole, traditional landmarks for the foramen of Monro or the intersection of the planes through the pupuil and the external auditory meatus, are used. From the occipital location, a target at the midpoint of the forehead just at the normal hair line will ensure the catheter proceeds into the frontal horn instead of the temporal horn. There is, however, no proven ideal location for the ventricular catheter. Very recent evidence from a pediatric shunt design trial suggests that frontal or occipital locations are better than in the body of the ventricle or in the third ventricle. [8] Cannulating small ventricle is easier from a frontal location. In these patients either ultrasonograhy, neuroendoscopy or even stereotaxis may assist with successful ventricular cannulation. The ventricular catheter could usually be felt to pop once the ependyma is passed, followed with a concomitant gush of CSF. Withdrawing vigorously will simply draw brain tissue into the catheter and obstruct an intraparenchymal shunt. A small amount of fresh blood that clears is not unusual. Extensive hemorrhage should irrigate copiously until the CSF clears. When attaching burr hole reservoirs (usually with contained valves), the ventricular catheter must be withdrawn, then driven in again. The attachment site is usually below the cortical surface, it becomes adherent, and the catheter loss at a subsequent revision is quite possible. When using a flat-bottomed valve, a pocket must be created along the distal path. This pocket must be exactly along the course of the catheter or the valve will bend when attempting to slide it along. When attaching the ventricular catheter to the valve, one should avoid using metal instruments directly on the tubing forcefully, because they can

1262 Pediatric Neurosurgery lacerate it, causing subsequent leakage or disconnection. The forceps or hemostats fitted with Silastic sleeves is useful to grasp the hardware. When tying the catheter over the connector, having the tie directly over the neck of the connector, tight enough not to allow spontaneous disconnection, and not too tight to lacerate the tubing. The valve system is then placed into the pocket by gently pulling on the peritoneal cathetr from below. The shunt system can then be secured to the pericranium to prevent subsequent migration. Posterior fossa catheters are particularly prone to migration and difficult to secure. Once in place, the system should be checked that is flowing, either spontaneously or with gentle pumping of the reservoir. If there is any doubt, the system should be disconnected to verify that both ends are patent. The distal catheter is then inserted into the peritoneal cavity. If resistance is encountered or the catheter is spontaneously backing out of the abdomen, it may be coiling in the pre-peritoneal space. Once intraperitoneal placement is ensured, the purse-string suture is secured and the abdominal layers are reapproximated. Skin closure is critical. Any CSF leak predisposes to wound breakdown or infection. Normally, the skin is closed in two layers, with careful apposition of the skin edges. The fragile skin of premature infants may fray and permit CSF leakage through large needle holes. An occlusive dressing, which will also resist attempts by small children to remove them, is also recommended for 48 hours. Positioning in the postoperative period is also important. In patients with large ventricles, early mobilization may risk a subdural hemorrhage. In patients with high-resinstance valves, deliberately placing them in an upright posture may promote CSF drainage and prevent acuumulation of CSF under the skin. The postoperative hospital stay is typically 2 or 3 days. Prophylactic antibiotics are normally given intravenously preoperatively and sometimes of a few doses postoperatively only. Prolonged antibiotic treatment in the postoperative period in and uncomplicated shunt patient is unwarranted. Shunted patients typically have immediate resolution of acute symptoms. In infants, a sunken fontanelle with standard valves is typical. Lowpressure headache can occur in older patients, particularly if the hydrocephalus is of longstanding. In the absence of some particular problem intraoperatovely, an initial postoperative CT or MRI is unlikely to be very helpful. Normally, the patients are seen in follow up at approximately 3 months postoperatively with a CT or MR at this time and at 1 year with repeat imaging, becauses the ventricles do not reach their final size on average until 1 year, at lease in children. Other shunts: ventriculopleural shunts, ventriculoatrial shunts and lumboperitoneal shunts. Ventriculoatrial (ventriculocardiac) shunt is usually the second possible option after the ventriculopleural shunt. The most serious conditions that could complicate this procedure are cor pulmonale and shunt nephritis.[9][10] The shunt tip should be placed in the right atrium just above triscuspid valve. With growth the tip of the atrial tube tend to pull out of the right atrium, malfunction of the shunt may occur. So that a small child might need a couple of revision for growth-related shunt failure. Surgical technique; Though usually a common facial artery is used for entering the venous

Pediatric Neurosurgery

1263

system, indirect method through the jugular or subclavian vein are previously described. Position of the tip can be defined either fluoroscopy, ultrasonography and EEG monitoring.

Ventriculpleural shunts. Pleural shunts are also an alternative to peritoneal shunts. Surgical technique; the preural space can be entered at any site. Usually the used entry point is located along the anterior axillary line where it crosses the fouth, fifth or sixth rib interspace. Upper border of the rib muscle is split to avoid the neurovascular bundle. The pleura is opened, as the peritoneum. The care should be taken to close the pleura to avoid excess air entry to the cavity. Because of the possible severe complication such as respiratory failure caused by effusion, personally I do not prefer this shunt procedure.

Lumboperitoneal shunts; Since the cause of the hydrocephalus in children are usually non-communicating hydrocephalus, this procedure are infrequently used in this population. The most advantage of this procedure is not damage cerebral parenchyma itself. The other possible advantage is reduce the chance of intraparechymal or intraventricular hemorrhage. The reduce the chance of epilepsy related to the procedure and less infection rate. [11][12] Since there is no choroid plexus, ependyma or glial tissue, the chance of the proximal shunt obstruction is theoretically low. [13] The most serious complication is acquired tonsillar herniation. Though most of the patient shows radiological evidence with out symptom, few patients have symptoms such as neck pain, lower cranial nerve dysfunction and apnea. [14][15] Surgical technique; The surgeons positions to the both side of the patients. The patients positioned in lateral decubitus position with rolled blankets or pillows. Placement of the lumbar catheter is done by either percutaneous or open procedures. Usually 14-gauge Touhey needle through the L4-5 interlaminar spce is used. After removing inner cannula, the catheter is inseted through the needle. Intraoperative fluoroscopy may be used to confirm appropriate catheter position.

2. Neuroendoscopy With a significant evolution of neuroendoscopy and the application to the management of hydrocephalus in children, the management of the children hydrocephalus are dramatically altered. Although many children hydrocephalus were well controlled with the shunt incersion, some patients still have the devastating complication of the shunt. The neurosurgeon can fenestrate cysts and obstructing membranes, thereby converting complicated forms of hydrocephalus in to more easily managed conditions and in many instances diversion of CSF can be accomplished with or without shunt systems. Therapeutic procedures aimed at treating hydrocephalus may be divided into shunt catheter placement, memebrane fenestration, and tumor biopsy.

1264 Pediatric Neurosurgery

Third ventriculostomy With the advent of the high quality endoscope, light sources, camera and instrument, now this procedure can be done safely. Many patients may remain shunt free with this procerure. [16]

Surgery Successful third ventriculostomy depends on familiality with normal endoscopic anatomy of the ventricular system and the variation in hydrocephalus. The surgical procedure is normally performed with the patient supine and the head elevated approximately 30 degrees to eliminate the excessive CSF loss and air collection to the subdural and intraventricular spaces during the procedure. Preoperative coronal and sagittal MR images allows a straight trajectory from the site of burr hole, foramen of Monro and the floor of the third ventricle. Semi-circular skin incision is usually used to prevent the post-operative CSF leackage. Small burr hole adequate size to the instrument used is made with the twisted drill. A site is chosen 2 to 3 cm lateral to the midline just

The endoscopic view of the right foramen of Monro from a right frontal burr hole approach to the lateral ventricle. The choroid plexus usually extend into the posterior margin of the faramen inferiorly. The septal and thalamostriate veins join to form the internal cerebral vein beneath the choroid plexus. The fornix forms the anterior margin of the foramen.

The picture is the floor of the third ventricle. The infundibular recess is located anteriorly, multitude of small blood vessels, red in color. The target point for endoscopic third ventriculostomy is the center of the triangle formed by indibular recess and a pair of mamillary bodies.

Pediatric Neurosurgery

1265

anterior to the coronal suture. The dura is coagulated and incised to allow entry of the instrument. After dural opening, the lateral ventricle is cannulated. One can use a rigid endoscope itself to perform cannulation, I personally prefer to use a peel away sheath larger than the outer diameter of the endoscope. The sheath is placed to just beyond the roof of the lateral ventricle. As the endoscope is moved into the foramen of Monro, the floor of the third vntricle can be visualized. Depending on the degree of hydrocephalus and duration, the floor could be either severely stretched and thinned causing translucence or opaque and thick. The floor depth from the cortical mantle vary from case to case but average is approximatelin 7.7 cm. [17] The neurosurgeon must take great care to plan the fenestration to pass the instrument anterior to the basilar artery. Usually, the best site for fenestration is halfway between the cleavage of mamilary bodies and the hypophyseal recess. The tip of the endoscope, blunt instruments or Fogaty balloon is then used to create a fenestration into the subarachnoid space. This is followed by passage of uninflated 2 to 4 French Fogarty balloon catheter. Gently enlarging the fenestration by inflation of the balloon with saline allows satisfactory opening. The endoscope then should move beyond the fenestration to ensure that effective communication between the intraventricular and the subarachnoid space has been achieved. If there is thickened arachnoid or remaining Liliequist’s memabrane beneth, similar techniques may be necessary to make the communication to the prepontine cistern. During the procedure miner bleeding occurs. It is almost always controlled by continuous irrigation of lactate Ringer’s solution. During irrigation one should make sure the volume of the fluid drain out is not much less volume than the volume used for irrigation, otherwise severe intracranial pressure can ensue. At completion of the fenestration, the sheath is removed. With removing the sheath, Gelfoam is placed to prevent the CSF leak. The scalp is sutured. If any bleeding has occurred during the procedure, a ventricular darin is left in place for a few days.

Surgical indication Endoscopic membrane fenestration is the most significant advancement in the management of neurosurgery since the introduction of the shunt surgery. The surgical indications for endoscopic surgery in hydrocephalus are classified in four categories: obstructive hydrocephalus, malticompartmental hydrocephalus, unilateral hydrocephalus, and focal ventricular cystic lesions. It is usually thought that the success rate in the children younger than 2 years are much lower than the older group. [18] [1] Bondurant C, Jimenez D. Epidemiology of cerebrospinal fluid shunting. Pediatr Neurosurg 23: 254-8, 1995 [2] Fernell E, Hagberg B, Hagberg G, von Wendt L. Epidemiology of infantile hydrocephalus in Sweden. I. Birth preverence and general data. Acta Paediatr Scand 75:975-981,1986 [3] Del Bigio MR. Neuropathological changes caused by hydrocephalus Acta Neuropathol. 85: 573-585, 1993 [4] Del bigio MR and McAllister JP. Hydrocephalus pathology. In Choux M, Di Rocco C. Hockley A, Walker M (eds) Pediatric Neurosurgery. London: Churchill Livingstone, pp

1266 Pediatric Neurosurgery

CT showed severe hydrocephalus with periventricular low dentisy zone. MRI revealed the aqueductal stenosis. The case like these findings is good candidate for ETV

229-230. 1999 [5] Drake JM, Kestle JR, Milner R, Cinalli G, Boop F, Piatt J Jr, Haines S, Shiff SJ, Cochrane DD, Steinbok P, MacNeil N. Randomized trial of cerebrospinal fluid shunt valve design in pediatric hydrocephalus. Neurosurgery 1998: 43: 294-305 [6] Langley JM, LeBlanc JC, Drake J, Milner R. efficacy of antimicrobial prophylaxis in placement of cerebrospinal fluid shunts: meta analysis. Clin infect Dis. 1993, 17:98-103 [7] Bierbrauer KS, Storrs BB, McLone DG, Tomita T, Dauser R. a prospective, randomized study of shunt function and infections as afunction of shunt placement. Pediatr Neurosurg. 16:287-291, 1990 [8] Tuli S, O'Hayon B, Drake J, Clarke M, Kestle J. Change in ventricular size and effect of ventricular catheter placement in pediatric patients with shunted hydrocephalus. Neurosurgery 45:1329-1335, 1999 [9] Lundar T, Langmoen IA, Hovind KH. Fatal cardiopulmonary conpllications in children treated with ventriculoatrial shunts. Childs Nerv Syst. 7:215-217, 1991 [10] Lam CH, Villemure JG: Comparison between ventriculoatrial and ventriculoperitoneal shunting in the adult population. Br J Neurosurg 11: 43-48,1997 [11] Chuman PD, Kulkarni AV, Drake JM, Hoffman HJ, Jumphreys RP, Rutka JT. Lumboperitoneal shunting: a retrospective study in the pediatric population. Neurosurgery 32: 376-383, 1993 [12] Aoki N. Lumboperitoneal shunts: Clinical spplications, complications and comparison with ventriculoperitoneal shunts. Neurosurgery 26:998-1004, 1990 [13] Hoffman HJ, Hendrick EB, Humphreys RP: New lumboperitoneal shunt for communicating hydrocephalus. J Neurosurg 44: 258-261. 1976. [14] Chuman PD, Drake JM, Del Bigio MR; Death from chronic tonsillar herniation in a patient with lumboperitoneal shunt and Crouzon’s disease. Br J Neurosurg 6: 595-599, 1992 [15] Chumas PD, Armstrong DC, Drake JM, Kulkarni AV, Hoffman HJ, Humphreys RP, Rutka JT, Hendrick EB. Tonsillar herniation: the rule rather than the exception after lumboperitoneal shunting in the pediatric population. J Neurosurg 78: 568-573, 1993 [16] Sainte-Rose C: Third ventriculostomy: I. In Manwaring KH, Crone KR (eds): Neuroendoscopy. Vol 1. New York, Mary Ann Liebert, 1992. Pp47-62 [17] Riegel T, Hellwig D, Bauer BL, Mennel HD: Endoscopic anatomy of the third ventricle. In Bauer BL, Hellwig D (eds): Minimally Invasive Neurosurgery. Vol II. New York,

Spina bifida

1267

Springer-Verlag, 1994, pp 54-56 [18] Baldauf J, Oertel J, Gaab MR, Schroeder HW. Endoscopic third ventriculostomy in children younger than 2 years of age. Childs Nerv Syst 23: 623-626, 2007

3. Spina bifida A. open spina bifida Myelomeningocele Associated malformation; Chiari II anomaly and hydrocephalus. Pathophysiology; Spina bifida is caused by a failure of the neural tube to close during the first month of the embryogenesis. Normally the closure of the neural tube occurs

The picture showed the sacral myelomeningocele. The cystic bulging was seen rostrally and placode was observed caudally in this case.

Preoperative picture showed flat neural placode. Picture also showed the immediate after primary closure of the lesion.

1268 Pediatric Neurosurgery around 28 days after fertilization. A localized failure of neural tube to close results in a neural tube defects; involvement of the cranial neural tube produces anencephaly, whereas involvement of the caudal end produces myelomeningocele. The cause of neural tube defect has been debated long time. Generally the nonclosure theory is now widely accepted, whereas the overdistension theory has largely been discarded. However, the conclusion has not been reached, yet. Myeloschisis has been thought to be a different entitiy of disease from myelomeningocele. However, now it is thought to be the same disease but with different morophology. [11]

Epidemiology of myelomeninogcele Myelomeningocele currently occurs with approximately 1 to 2 per 1000 live birth. However, there is marked variations from region to region. The cause is not determined but it is considered to be multifactorial. The recurrence risk for parents with one previously affected child rises to about 1-2%. [12] The risk for those having two affected children may be as high as 10%. Treatment: usually the open neural placode should be closed within 48 hours after birth. The closure of the neural placode should be done in a layer by layer fashion. Sometimes it is not easy to perform skin closure. The difficulty of the repair is not depending on the size of the lesion but the digree of mobilization of the surrounding skin. A significant kyphotic deformity may also complicate the closure of the lesion. The placode should be protected after birth since it often contains at least partially functioning neural tissue. More than one-third of infants have sensorimotor functions after closure that were not initially observed at birth. [13]. The placode also can subserve localized spinal reflexes which are important in bladder and bowel function. [14] The lesion is initially covered with gauze dressings soaked in sterile saline solution. Iodinecontaining solutions are harmfull to live tissues and should be avoided. Plastic wrap is placed above the gauze to keep the dressings moist. Systemic antibiotics are usually provided for the first postnatal days to prevent both CSF and urinary tract infections. The placode should be closed usually within 48 hours after birth to avoid further neurological deterioration and infection. [15] The neural placode is sharply dissected from the surrounding skin . Care must be taken to avoid cutting dorsal nerve roots that arise along the ventral side of the placode near its border with the skin. All cutaneous tissue must be gently removed from the edges of the neural placode to avoid an inflammatory arachnoiditis and an inclusion dermoid. [16]. [17]. Then the both pial edge are brought together to reconstruct the neural tube. It is not for decrease the incidence of retethering but for less difficulty for unthetherig surgery if necessary, in future. After closing the placode, the surrounding dura is mobilized as possibly as wide from the underlying fascia and reapproximated to prevent the CSF leakage and retethering. If the cutaneous defect is large enough and simple primary closure is not feasible, then a plastic surgical procedures should be chosen. [18] Hydrocephalus and Chiari II malformation are the most common associated problem in the patients with myelomeningocele.

Spina bifida

1269

Hydrocephalus; approximately 15% of patients with a myelomeningocele are born with severe hydrocephalus and require immediate shunt placement. If the patient shows any signs of hydrocephalus at birth, then we usually perform V-P shunting procedure at the same time of the myelomeningocele repair. It is estimated that approximately 70 to 80% of the myelomeningocele patients will also have hydrocephalus. Chiari II malformation; the Chiari II malformation is a complex disorder encompasses anomalies of virtually the entire neuroaxis. Most prominent among these are caudal displacement of the cerebellar vermis and tonsils into the cervical canal. Elongation, kinking, and caudal displacement of the lower brain stem below the foramen magnum; and upward displacement of the suprerior cerebellum through a dysplastic, low-lying tentorial incisura. A small posterior fossa and Luckenschadel of the skull, as well as many associated telencephalic and diencephalic anomalies suggest a pancerebral disorde involoving much of the cranial neuraxis and chondrocranium. The most popular theories regarding the pathogenesis of Chiari II malformation are dysgenesis/developmental arrest theory [19][20][21], hydrocephalus/ hydrodynamic theories [22], traction theories [23][24] and small posterior fossa/ overgrowth theories [25][26][27]. The Unified theory proposed by McLone and Knepper is accepted widely to explain multiple anomaly seen in the patient with myelomeningocele [28]. For surgical correction of the Chiari II malformation, the patient is positioned prone with the head flexed. Venous access that allows rapid blood volume replacement is required. A skin incision is made from approximately the inion to one or two vertebral bodies level below the lower part of the herniated cerebellum. With the combination of rongeurs and drills, a laminectomy is performed wide enough to expose the spinal cord and Chiari malformation (facet should not be touched). Rarely one should remove occipital bone since the patient with Chiari II malformation usually have wide opening at the foramen magnum. Be note that the position of transverse sinus might be much lower compare to normal counterpart. After adequate bone has been removed, two dural tacking suteres to move up the dura mater are placed just off the midline below the end of malformation. With a dissector, protecting underline neural tissue, the dura is opened. Then the thickened arachnoid over the foramen of Magendie is identified. There are two surgical techniques; one is after identifying the arachnoid and confirming the space behind the malformation close the dura with fascia or substitute dura. The other is open the fourth ventricle with or without tonsillectomy. There is no data of which is superior to the other.

Latex sensitivity Approximately 60% of the patient with spina bifida have a positive reaction to skin test for latex. The high prevalence is thought to be secondary to repeated exposure and unknown disease associated factors. This problem may account for some of the unexplained sudden death in the patients with previous myelomeningocele repair. The operative room and ward for the myelomeningocle patients should be prepared for latex free. Eliminating exposure to the antigen can prevent cutaneous and respiratory symptoms.

1270 Pediatric Neurosurgery Folate is a coenzyme required for hematopoiesis and metabolism and for normal funtion of the gastrtrointestinal neurologic systems. Some studies showed the effect of the folic acid supplementation to reduce the risk of open NTD [29]. The current recommendation is that women at high risk for the development of NTD consume 4 mg/day of folic acid from 1 month before pregnancy through the first trimester [30]. For women who could possibly become pregnant should consume 0.4mg/day of folic acid [31]. [11] McLone DG and Dias MS. Normal and abnormal early development of the nervous system. In : Check WR, ed. Pediatric Neurosurgery. Surgery of the Developing Nervous System. Philadelphia: WB Saunders, 1994: 3-39 [12] Chatkupt S, Johnson WG. Waardenburg syndrome and myelomeningocele in a family. J Med Genet 1993; 30:83-84. [13] McLone DG. Results of treatment of children born with a myelominingocele. Clin Neurosurg. 30:407-412, 1983 [14] McGlaughlin TP, Banta JV, Gahm NH, Raycroft JF. Intraspinal rhizotomy and distal cordectomy in patients with myelomeningocele. J Bone Joint Surg 68A; 88-94, 1986 [15] Charney EB, Weller SC, Sutton LN, Bruce DA, Schut LB. Management of the newborn with myelomeningocele; time for a decision-making process. Pediatrics; 75: 58-63, 1985 [16] McLone DG, Dias MS. Complications of myelomeningocele closure. Pediatr Neurosurg 17:267-273, 1991-92. [17] Reigel DH. Tethered spinal cord. Concepts Pediatr Neurosurg 4; 142-164, 1983 [18] Ramasastry S, Cohen M. Soft tissue closure and plastic surgical aspects of large open myelomeningoceles . Neurosurg Clin North Am 6;279-291, 1995 [19] Cleland J; Contribution to the study of spina bifida, encephalocele, and anencephalus. J Anat Physiol 17: 257, 1883 [20] Daniel PM, Strich SJ: Some observations of the congenital deformity of the central nervous system known as the Arnold-Chiari malformation . J Neuropathol Exp Neurol 17:255,1958 [21] Peach B: The Arnold-Chiari malformation: MorphogenesisL Arch Neurolo 12:527, 1965 [22] [23] Penfield W, Coburn DF: Arnodl-Ciari malformation and its operative treatment. Arch Neurol Psychiatry 40;328,1938 [24] Lchitenstein BW: Distant neuroanatomic complications of spina bifida (spinal dysraphism): Hydrocephalus, Arnold-Chiari deformity, stenosis of the aqueduct of Sylvius, etc., pathogenesis and pathology. Arch Neurol Psychiatry 47: 195,1942 [25] Marin-Padilla M, Marin-Padila TM. Morophogenesis of experimentally induced Arnold-Chiari malformation. J Neurol Sci 50:29, 1981 [26] Padget DH: Development of so-called dysraphism: wWith embryologic evidence of clinical Arnold-Chiari and Dandy-Walker malformations. Johns Hopkins Med J 130: 127, 1972 [27] Padget DH, Lindenberg R: Inverse cerebellum morophogenetically related to DandyWalker and Arnold-Chiari syndromes: Bizarre malformed brain with occipital encephalocele. Johns Hopkins Med J 131: 228,1972 [28] McLone DG, Knepper PA: The cause of Chiari II malformation: A unified theory. Pediatri Neurosurg 15:1, 1989 [29] Centers for Disease Control and Prevention: Use of folic acid for prevention of spina bifida and other neural tube defects. MMWR Morbid Mortal Wkly Rep 40: 513-

Spina bifida

1271

516,1991 [30] Committee on Genetics, American Academy of Pediatrics: Folic acid for the prevention of neural tube defects. Pediatrics 104: 325-327, 1999 [31] Centers for Disease Control and Prevention: Recommendations of the use of folic acid in reduce the number of cases of spina bifida and other neural tube defects. MMWR Morbid Mortal Wkly Rep 41: 1-8,1992

Lipomas of the spine Spinal lipomas represent the most common of the lesions embraced by the term occult spinal dysraphism. Spinal lipoma are a developmental malformation, occurring in approximately 1 in 4000 births. [41] There are several well accepted classifications. Chapman and colleague have proposed the classification in which dorsal, caudal and transitional type. [42] [43] Mclone divided spinal lipomas in three groups in which intra dural lipomas, lipomas of the conus medullaris and lipomas in the filum. Lipomas of the conus have a separate subgroups like lipomyelocele, lipomyelomeningoceles and lipomyelocystocele based on the neuroimaging studies. [44] Neurosurgeons should be familiar with the those system well and possible variation within each type. The cause of these entities were not well understood yet. The best explanation for lipomas have been reported by McLone and Naidich. [45] The Currrent undestanding of myelomeningocele implicates a failure of the neural tube closure. In contrast, lipoma of the conus arise when early disjunction between cutaneous ectoderm and neuroectoderm occurs. Then the cutaneous ectoderm has sealed, but the still open neural tube is exposed for the in-growth of paraxial mesoderm derived tissues. Unlike the lipoma of the conus, the lipomas of the filum are thought to be developing as a result of the secondary neurulation disorder

Left; MRI T1-weighted sagittal image showed the spinal lipoma which extend from subcutaneous to spinal cord itself. Right; There is a huge subcutaneous mass in the back of the patient.

1272 Pediatric Neurosurgery

Legend; MRI T1-weighted sagittal and axial showed the filum lipoma.

Cutanelus anomalies Despite the term occult spina bifida, the most common cutaneous signs suggesting occult disraphism are subcutaneous lipoma, angioma, hairy patch, dermal sinus, dimple and appendage.

Associate anomalies To addition to the cutaneous anomalies, perineal region anomalies such as imperforate anus, abnormal genitalia and exstrophy may present. [46][47][48]

Surgical management The aim of surgery for spinal lipomas is to untether the spinal cord to prevent progressive orthopedic deformity and neurologic damage and to preserve sphincter function. Patient is positioned prone on a parathoracic rolls under the heating blanket. The area of the back to be operated on is washed with soap and water. After prepared with iodine, patient is covered with drapes except the operative site. The incision site is infiltrated with local anesthetic containing epinephrine. Skin is incised with scalpel. The lipoma tissue is then removed from covered skin. A midsagittal incision is made over the posterior spinous processes for two to three levels superiorly to the lipoma. The paraspinous muscles are then dissected off the posterior spinous process and lamina bilaterally. If the lamina is not separated, one or two lamina superior to the lipoma are removed to expose dura. The dura mater over normal cord is then opened with a

Craniosynostosis

1273

scalpel. The dural incision is carried inferiorly toward the lipoma. The care must be taken not to injure the normal neural tissue, because there may be the dorsal roots where the lipoma enter to the subdural space at the dural defect. If the lipoma is large and the neural tissue is laterally displaced, the decompression of the lipoma should be carried out before entering the subdural space. The retention suture to the dura is useful to identify the normal dorsal roots. The goal of this surgery is circumscribe the lipoma in the subdural space. With the removing of the lipoma itself and resect the abnormal adhesion between the normal neural structures and lipoma, the relation of lipoma and surrounding structure become visible. The goal of the surgery is near-total resection of the lipoma. If resection of the lipoma is likely to result in new or increased neurological deficit, then the pocedure should be terminated. Many neurosurgeons tend to use intraooperative monitoring, but the indications are still controversial. After the removal of the large portion of the lipomatous mass, it is also important to verify if there is a thickened filum terminale. If there is, it must be cut to prevent later retethering. With this, spinal cord should be freely movable. If possible, pia to pia sutures are used to close the midline defect in the spinal cord where the lipoma was removed. It may also reduce the chance of retethering caused by tissue to adhere to the overlying dura. Dural closure should be carried out in a water tight fashion to reduce the chance of CSF leak with dura or dural substitute. The muscle and fascia is closed tight in two layers, if possible, to prevent CSF leak. The skin is sutured in the midline and apply the skin tapes. The child is maintained in the horizontal position for 3 to 4 days. If possible I personally prefer to position the child prone during the rest. [41] Bruce DA, Schut L. Spinal lipomas in infancy and childhood. Childs Brain 5: 192203. 1979 [42] Chapman PH. Congenital intraspinal lipomas: anatomic considerations and surgical treatment. Childs Brain 9: 144-148, 1982 [43] Chapman PH, Davis KR: Surgical treatment of spinal lipomas in childhood. Pediatr Neurosurg 19: 167-275, 1993 [44] McLone DG, Thompson DCP. Lipomas of the spine. In pediatric Neurosurgery. McLone D (ed) Philadelphia: WB Saunders, 2001, pp289-301 [45] McLone DG, Naidich T: Terminal myelocystocele. Neurosurgery 16: 35-41, 1985 [46] Long FR, Hunter JV, Mahboubi S, Kalmus A, Templeton JM Jr. Tetherd cord and associated vertebral anomalies in children and infants with imperforate anus: evaluation with MR imaging and plain radiography. Radiology 200:377-382, 1996 [47] Warf BC, Scott RM, Barnes PD, Hendren WH 3rd. Tethered spinal cord in patients with anorectal and urogenital malformations. Pediatr Neurosurg. 19:25-30, 1993 [48] Greene WB, Dias LS, Lindseth RE, Torch MA. Musculoskeletal problems in association with cloacal exstropy. J Bone Joint Srug Am 73: 551-560, 1991

4. Craniosynostosis Introduction Craniosynostosis, the premature closure of cranial sutures, produces an abnormal shaped skull and face. While many of the cases have purely cosmetic problem, the

1274 Pediatric Neurosurgery other patients also have the problem related to the increased intracranial pressure. [1] The size of the infant brain doubles in the first 6months of life and doubles again by 2 years and the skull must enlarge to accommodate this growth. [2] When cranial suture fuses prematurely, the growth of the skull in the direction perpendicular to the suture will be reduced. [3] In addition to the direct effect of the suture involved, there are further factors that contribute to the overall picture; one is compensatory growth of the normal sutures, another is the presence of raised ICP, the other is the abnormal bone activity at cellular level in selected patients. The most of the cases occur as a primary anomaly but a small portion of craniosynosotosis cases could be a result of the natural history of another disease.

Prevalence The prevalence is approximately 0.4 to 1.6 per 1,000 birth. [4] [5] The gender predisposition depend on the particular suture involved.

Pathogenesis The pathophysiology for craniosynostosis remains prooly understood. The Most popular theory suggests that the abnormal cranial base induces premature stenosis secondary to the forces in the dura. [6] Another theory state that the basal sutures respond to the premature fusion of the vault sutures. [7] The theories proposed do not explain the compensatory changes in cranial shape that occur throughout the cranial vault. Craniosynostosis most likely results from many different pathologic processes. [8]

Legend; craniogram and 3DCT showed early closure of all sutures. Craniogram also showed severe thumb printing.

Craniosynostosis

1275

Simple craniosynostosis Sagittal Synostosis Clinical feature Sagittal synostosis is the most common form of simple craniosynostosis. The prevalence ranges from 2 to 10 per 10,000 live births. [9][10] There is male predominance, comprising 70% to 85% of the patients. [9][10] Familial cases were also reported in approximately 10%. The shape of the skull is long and with narrowed biparietal diameter. It is often called as boat-shaped head. The fused suture is usually palpable as a ridge. Patients often have prominent bossing in both frontal and occipital, because of the compensatory growth of the adjacent suture. Early diagnosis and treatment is associated with much more favorable cosmetic outcome. Furthermore, the operation is more simple and less morbidity expected than in the older child population.

Surtical treatment The simple strip craniectomies and pi procedures are commonly used but a variety of operative procedures have been proposed to correct sagittal synostosis. [11][12] For these operations, the patients are placed in a modified prone position with the head extended and supported with soft materials. [13]

Legend; 3D reconstructed CT lateral view showed so called elongated skull deformity with frontal and occipital bossing. Top view showed early closed sagittal suture especially in anterior part.

1276 Pediatric Neurosurgery

Bicoronal synostosis Bicoronal craniosynostosis leads to brachycephaly in which the head shape become more spherical. Although sometimes occurring as an isolated form, the most children with bicoronal craniosynostosis are syndromic craniosynostosis.

Unilateral coronal synostosis Clinical feature The reported prevalence ranges from 0.7 to 4.8 per 10,000 live births. [14][15] Female predominance is observed in unilateral coronal synostosis. [15] Familial cases are also reported. [15] Premature unicoronal fusion affect not only the coronal suture itself but also the adjacent sutures. The craniofacial deformities seen in unicoronal synostosis is somewhat difficult to understand. [16] The shape of the head is flattening of the supraorbital ridge of the affected side, sometimes with a compensatory bossing on the normal side. The anterior cranial fossa is shortened on the affected side and the orbit is shallow. Not only the deformity of the head, but also the facial scoliosis centered around the nasion and concave to the side of the affected suture.

Surgical treatment Early surgery is advocated because of the associated facial deformities. Unilateral coronal synostosis usually not corrected with simple suturectomy of the affected coronal suture. The surgical techniques must be individualized, depending on the degree and type of abnormality in each patient. [17][18][19]

Metopic craniosynostosis Clinical features Prevalence is approximately 1 in 15,000 birth. But his may be an underestimate because many mild cases may not be referred for evaluation. [20] A male predominance exists as in sagittal synostosis. [21] The familial cases are reported but the number is small.[22] Premature fusion of the metopic suture results trigonocephaly in which keel shaped prominence of the forehead with deficiency of the lateral supraorbital rim. Orbital hypotelorism and epicanthus are also observed. It is usually thought to be a simple craniosynostosis, may occur as part of certain genetic syndromes such as Optiz C syndrome and trisomy 11. The anterior cranial fossa is very small because of shortened interpterional distance and frontal height. The severity may vary because of the difference in the involved basal sutures in each cases. [23] Patients with metopic synostosis have the highest prevalence of associated brain abnormalityis, including agenesis of the corpus callosum, holoprosencephaly. A substantial portion of patients also exhibits developmental delay

Craniosynostosis

1277

Legend; 3D reconstructed CT top view revealed early closed metopic suture and triagle shape deformed skull.

and learning difficulties. [22][24]

Surgical treatment The optimal age of surgery is 3 to 6 months. Most widely employed procedure involves bilateral fronto-orbital advancement with or without frontal remodeling. [22][23]

Syndromic craniosynostosis Crouzon syndrome The incidence is approximately 1 in 25,000 birth. Crouzon syndrome shows an autosomal dominant inheritance with approximately 50% incidence of familial cases. [25][26] The symptoms includes craniosynostosis, maxillary hypoplasia and proptosis. The coronal sutures are most commonly affected initially. The skull shape tend to be brachycephalic. With the child grow, multisuture also become fused, producing a pansynostosis. [27][28] Thus it is often seen the patients with increased intracranial pressure and with tonsillar herniation. [29][27] Mutations of the FGFR2 gene, involved in the fibroblast growth, have been found in more than half of the patients. [30]

The acrocephalosyndactylies In some of craniosynostosis, abnormalities of the hands and feet are part of the syndrome. Those are called as acrocephalosyndactylies and include Apert, SaethreChotzen, Pfeiffer, Vogt’s cephalodactyly and Waardenburg’s syndromes.

1278 Pediatric Neurosurgery

Apert syndrome The incidence had been thought approximately 1 in 160,000 birth. [31] Recent study showed it to be approximatery 1 in 55,000 birth. [32] Most cases of Apert syndrome are sporadic, however cases of cases of dominant transmission with complete penetrance is also described. [33] Advanced paternal age has been proposed as a risk factor. [31] The specific mutations appear to involve adjacent aminoacids of FGFR2 gene. [34] The head tends to be tall and foreshortend in the anteroposterior dimension. The occipital region is flattened. Maxillary hypoplasia is also present with high arched occasionally cleft palate. The ethomoidal labyrinth is expanded with secondary orbital hypertelorism. The ears are usually low set. Hearing loss is also observed as a complication of the cleft palate, Eustachian tube disfunction. Respiratory complications are also common, possibly because of reduced nasopharyngeal volume. Hydrocephalus both communicating and non-communicating are reported. Abnormalities of brain development are also described. Mental retardation has been also described. The most distinguishing feature of the child with Apert syndrome is the characteristic symmetrical syndactyly of the hands and feet. The bony fusion of cervical vertebra is also observed.

Legend; Preoperative 3DCT revealed premature closure of bilateral coronal suture with wide open anterior fontanelle.

Pfeiffer’s syndrome There is turribrachycephaly, masillary hypoplasia and antimongolid slant of the orbits. [35] Pfeiffer syndrome is characterized by the presence of unusually broad thumbs and big toes. There are subtypes according to the Cohen. Type I corresponds to the classic form described by Pfeiffer and is associated with a good outcome. Type II and type III are severe central nervous system disorders identified by the presence or absence

Craniosynostosis

1279

of cloverleaf skull deformity. [36] The estimated incedence is 1 in 200,000 birth. Abnormalities of the FGFR1 and FGFR2 genes are reported. [37]

Saethre-Chotzen syndrome Saethre-Chotzen syndrome refers to a variable pattern of malformations, including craniosynostosis, low-set hairline, facial asymmetry, ptosis, ear anomalies. Brachydactyly, and partial soft tissue syndactyly. The incidence of the syndrome is around 0.5 to 1 in 50,000 births. The genetic locus of the syndrome has been mapped to the chromosome 7p21-p22 region. [38]

Surgical management The surgical management of syndromic craniofaciostenosis have two main objectives: (1) to correct the craniocerebral disproportion and (2) to normalize the impaired CSF circulation and absorption, before irreversible brain damage is established. Hydrocephalus; Classically, preoperative CSF shunting is indicated only in cases of obviously severe and progressive hydrocephalus. Mild hydrocephalus tend to progress after the surgical correction of the craniosynostosis. It is also possible that even the ventricle size is moderate, some of the syndromic craniosynostosis patients may have severely increased ICP. [39] About one in nine patients with syndromic craniosinostosis patients needs to be shunted for progressive hydrocephalus.

Cranial expansion According to the site of early closure of the cranium, either frontal cranial expansion, posterior cranial expansion or total calvarial remodeling need to be selected for each individual. Since repeated operations will be required in future in the cases with syndromic craniosynostosis, well advanced operative planning is mandatory to obtain good operative results. [1] Renier D, Sainte-Rose C, Marchac D, Hirsch JF: Intracranial pressure in carniostenosis. J Neurosurg 57: 370-377, 1982. [2] Gordon IR. Measurement of cranial capacity in children. Br J Radiol 39:377-381, 1966 [3] Virchow R. Uver den Cretinismus, namentlich in Franken, und pathologische Schadelformen. Vor Pys Med Geselish Wurzburg 2: 230-271, 1851 [4] Keating RF. Craniosynostosis: Diagnosis and management in the new millennium. Pdeatr Ann 26: 600-612, 1997 [5] Gorlin RJ, Cohen MMJ, Levin LS. Syndromes of the head and neck. Monogr Med Genet 19. 1990 [6] Moss ML. Functional anatomy of cranial synostosis. Childs Brain 1: 22-23, 1975 [7] Jane JA, Park TS, Zide BM, Lambruschi P, Persing JA, Edgerton MT. Alternative techniques in the treatment of unilateral coronal synostosis. J Neurosurg 61: 550-556, 1984 [8] Cohen MMJ. Etiopathogenesis of craniosynostosis. Neurosurg Clin North AM 2: 507513,1991

1280 Pediatric Neurosurgery [9] Lajeunie E, Le Merrer M, Bonaiti-Pellie C, Marchac D, Renier D. Genetic study of scaphocephaly. Am J Med Genet 62:282-285, 1996 [10] Boop FA, Chadduck WM, Shewmake K, Teo C. Outcome analysis of 85 patients undergoin the pi procedure for correction of sagittal synostosis. J Neurosurg 85:50-55, 1996 [11] Venes JL, Sayers MP. Sagittal synostectomy: Technical note. J Neurosurg 44:390-392, 1976 [12] Epstein N, Epstein F, Newman G. Total vertex craniectomy for the treatment of scaphocephaly. Childs Brain 9: 309-316, 1982 [13] Park TS, Haworth CS, Jane JA Bedford RB, Persing JA. Modified prone position for cranial remodeling procedures in children with craniofacial dysmorphism: A technical note. Neurosurgery 16: 212-214, 1985 [14] Gripp KW, McDonald-McGinn DM, Gaudenz K, Whitaker LA, Bartlett SP, Glat PM, Cassilet LB, Mayro R, Zackai EH, Muenke M. Identigication of a genetic cause for isolated unilateral coronal synostosis: A unique mutation in the fibroblast growth factor receptor 3. J Pediatr 132: 714-716, 1998 [15] Lajeunie E, Le Merrer M, Bonaiti-Pellie C, Marchac D, Renier D. Genetic study of nonsyndromic coronal craniosynostosis. Am J Med Genet 55:500-504, 1995 [16] Bertelson TI. The premature synostosis of the cranial sutures. Acta Ophthalmol Suppl 51:24-174, 1958 [17] Hoffman HJ, Mohr G. Lateral canthal advancement of the supraorbital margin: A new corrective technique in the treatment of coronal synostosis. J Neurosurg 45: 376-381, 1976 [18] Epstein F, McCarthy JG, Coccaro PJ. Prophylactic craniofacial surgery. Child Brain 5: 204-215, 1979 [19] Marchac D. Radical forehead remodeling for craniostenosis. Plast Reconstr Surg 61: 823835, 1978 [20] van der Meulen J, van der Hulst R, van Adrichem L, Arnaud E, Chin-Shong D, Habets E, Hinojosa J, Mathijissen I, May P, Morritt D, Nishikawa H, Noons P, Richardson D, Wall S, van der Vlugt J, Renier D. The increase of metopic synostosis: a pan-Europiean observation. J Craniofac Surg. 20: 283-286, 2009 [21] Anderson FM. Treatment of coronal and metopic synostosis: 107 cases. Neurosurgery 8: 143-149, 1981 [22] Collmann H, Sorensen N, Krauss J. Consensus: Trigonocephaly. Childs Nerv Syst 12: 664-668, 1996 [23] Di Rocco C, Velaardi F, Ferrario A, Marchese E. Metopic synostosis: in favour of a ‘simlified’ surgical treatment. Childs Nerv Syst 12:654-663, 1996 [24] Sidoti EJJ, March JL, Marty-Grammes L, Noetzel MJ. Long-term studies of metopic synostosis: Frequency of cognitive impairment and behavioral disturbances. Plast Reconstr Surg 97:276-281,1996 [25] Kreiborg S. Crouzon sndrome. J Plast Reconstr Surg 18: 1-198, 1981 [26] Atkinson FRB. Hereditary craniofacial dysostosis, or Crouzon’s disease. Med Press Circular 195: 118-124, 1937 [27] Cinalli G, Renier D, Sebag G, Sainte Rose C, Arnauld E, Pierr Kahn A. Chronic tonsillar herniation in Crouzon’s and Apert’s syndromes: the role of premature synostosis of the lambdoid suture. J Neurosurg 83:575-582, 1995 [28] Kreiborg S, Marsh JL, Cohen MM, Liversage M, Pedersen H, Skovby F, Borgesen SE, Vannier MW. Comparative three-dimensional analysis of CT scans of the calvaria and skull base in Apert and Crouzon syndromes. J Craniomaxillofac Surg 21:181-188,1993 [29] Renier D, Sainte Rose C, Marchac D, Hirsch JF. Intracranial pressure in craniostenosis. J Neurosurg 57:370-377, 1982

Craniosynostosis

1281

[30] Reardon W, Winter R, Rutland P, Pulleyn LJ, Jones BM, Malcolm S. Mutations in the fibroblast growth factor receptor 2 gene cause Crouzon syndrome. Nat Genet 8:98102,1994 [31] Blank CE. Apert’s syndrome (a type of acrocephalosyndactyly) – observations on a British series of thirty-nine cases. Ann Hum Genet 24:151-163, 1960 [32] Renier D, Arnaud E, Cinalli G, Sebag G, Zerah M, Marchac D. Prognosis for mental function in Apert’s syndrome. J Neurosurg 85:66-72, 1996 [33] Roberts KB, Hall JG. Apert’s acrocephalosyndactyly in mother and daughter: Cleft patate in the mother. Birth Defects 7:262-263, 1971 [34] Moloney DM, Slaney SF, Oldridge M, Wall SA, Sahlin P, Stenman G, Wilkie AO. Exclusive paternal origin of new mutations in Apert syndrome. Nat Genet 13: 48-53, 1996 [35] Moore MH, Lodge ML, Clark BE. Spinal anomalies in Pfeiffer sndrome. Cleft Palate Craniofac J 32:251-254, 1995 [36] Cohen MM Jr. Pfeiffer syndrome update: Clinical subtypes and guidelines for differential diagnosis. Am J Med Genet 45:300-307, 1993 [37] Schell U, Hehr A, Feldman G, Robin NH, Zackai EH, de Die-Smulders C, Viskochii DH, Stewart JM, Wolff G, Ohashi H. Mutations in FGFR1 and FGFR2 case familial and sporadic Pfeiffer syndrome. Hum Mol Genet 4:323-328, 1995 [38] Howard TD, Paznekas WA, Green ED. Mutations in TWIST, a basic helix-loop-helix transcription factor, in Saethre-Chotzen syndrome. Nat Gent 15:36-41,1997 [39] Collman H, Soerensen N, Krauss J, Muhling J. Hydrocephalus in craniosynostosis. Childs Nerv Syst 4: 279-285,1988

1282

Encephaloceles SEYDOU BADIANE1 and KAZADI K.N.KALANGU2 1

Department of Neurosurgery, University Cheik Antha Diop, Dakar, SENEGAL Department of Neurosurgery, University of Zimbabwe, College of Health Sciences. Harare, ZIMBABWE

2

Key words: encephalocele, meningiocele, encephalocele, meningioencephalocele, vetriculocele

Definition and Classification Cephalocele is a herniation, through a skull defect, of intracranial contents (3,7,8,19,20,29 ) that may be meninges (meningoceles), brain (encephalocele) , both meninges and brain (meningoencephalocele). The name Ventriculocele will be given to the herniated brain which contents include a portion of the ventricle. Cephaloceles are also classified according to their site (19,39), they are located most of the time on the occipital (70 to 75%) and Frontoethmoidal (15%) areas. The overall incidence of cephaloceles is about 0.8 to 3.0 per 10 000 live births with encephaloceles being the most common form (15,18,26,28). Frontal encephaloceles are being more and more described in Africans (20,42) but they remain most common in Asia and Far Eastern countries (19,39). Indeed, in Thailand, Burma and Malaysia, this ration is reversed, and frontoethmoidal lesions predominate. Those lesions that extend from the area of the orbit, nose or forehead are also called sincipital encephaloceles (Table.1), while those in the occipital region are termed Table 1 CLASSIFICATION OF ENCEPHALOCELES BASED ON THE LOCATION OF THE SKULL DEFECT (39)

Encephaloceles

1283

notencephaloceles. Transphenoidal and basal encephaloceles are rare. The atretic lesion is more innocent on its appearance. Its “alopecic” form occurs in the midline on the parietal area, has dorsal cyst malformations, and is not associated with normal development (6,30). The “nodular” type is found in the midline and on the occipital area. It is not associated with other cerebral abnormalities and the child usually develops normally (6,30). The pathogenesis is not well known (2,5,8,11,12,29,40,41), however, current theories tend to favor the fact that it is a primary disturbance in the separation of neural and surface ectoderm during the final part of neural tube formation (17,19,26,40).

Clinical features Prenatal diagnosis is made around 16 weeks of gestational age particularly for large lesions (25,26). Most of the time however, the diagnosis is made at birth. The lesion consists of a fluctuant, round or oval, translucent or opaque mass that protrudes from the skull. The bone defect may extend into the foramen magnum and involve the posterior arch of the atlas. The skull base can be deformed with small anterior and middle cranial fossa and a large or small posterior fossa. The falx and tentorium are often abnormal in layout (11,12,30,33). The mass, which size may vary from an acorn to lesion larger than the skull, may be covered completely or partially by normal skin and may also pulsate. The sac may be sessile or pedunculated and contains brain tissue ( Fig. 1) . In severe cases, the sac contains parts of cerebellum, brainstem, occipital lobes, vascular structures, or only cerebrospinal fluid and glial remnants (16,25,26).

Fig. 1 Occipital encephalocele in a child

Neurologic examination is most of the time normal at birth except in cases of severe developmental abnormalities of the brain. The amount of abnormal and deformed neural tissue will determine the extent of cerebral dysfunction. For instance, intellectual impairment is more prevalent in patients with posterior encephaloceles than those

1284 Pediatric Neurosurgery with the anterior one. Pronounced motor delays are observed in patients with microcephaly. Particular attention should be paid to visual function in cases of occipital encephaloceles (6,26,30). Another type of encephalocele deserves particular attention namely the frontoethmoidal encephalocele (Fig.2) which presents as a facial mass. It is divided into a) Nasofrontal when it protrudes at the root of the nose above the level of the nasal bones, b) Nasoethmoidal when protrusion is below the nasal bones uni- or bilaterally, and c) Naso-orbital when the proptosis causes the displacement of the eye. Diagnosis may be delayed and made when child is examined for a nasal or glabellar mass, nasal congestion or snoring, hyperthelorism, or craniofacial abnormality (14,20,39). Other lesions such as basal and transsphenoidal encephaloceles are mostly not clinically visible. The first may cause upper-airway obstruction and the second may cause dysfunction of herniated optic pathways or endocrine malfunctions. These lesions need to be distinguished from nasal glioma, nasal polyp and dermoid cyst. Several other congenital abnormalities may be associated with encephaloceles and these are dextrocardia, pulmonary hypoplasia and laryngomalacia, renal agenesis, DandyWalker syndrome, Klippel-Feil syndrome, Arnold-Chiari 5 30 malformation, porencephaly, agenesis of corpus callosum, myelodysplasia, optic nerve dysplasia, cleft palate, and myelomeningocele (3,8,12,15,30,33, 36). Anterior encephaloceles are sometimes associated with arhinencephaly and anophthalmia (30,33).

Fig. 2 Frontoethmoidal encephalocele in a child

Neuroradiological Investigations Standard skull x-ray is usefull in providing a broad idea about the limits of the bony skull defect that is associated with the encephalocele. Magnetic Resonnance Imaging (MRI) is the investigation of choice when available and affordable (fig.3) . It outlines the herniated cerebral tissues, and especially their relationship with each other(12, 33). The herniated tissue can be traced back to the intracranial compartment and its union with anatomic structures therein. In addition, other associated cerebral abnormalities may

Encephaloceles

1285

be seen (19). 2D or 3D CT Scan is the best second choice (12, 33) (Fig. 4) though Ultrasound Scan may be useful for occipital encephaloceles (29,36). In cases of frontoethmoidal encephaloceles, further bone study with a CT Scan (bone window) may be required to better demonstrate the bony defects(12,20,25,33 ). MRI, Ctscan or conventional angiography is at times necessary to exclude major blood vessels which may supply the brain contained into the sac.

Fig. 3 MRI: Frontoethmoidal encephalocele

Fig. 4 Ct Scan in an Occipital Encephalocele

Treatment Surgery of encephalocele obeys first to basic principles of an operation performed on the newborn. Positioning must permit easy approach for the surgeon but also easy placement of monitoring lines and control of body temperature even in tropical countries. Blood loss must be kept as minimal as possible and monitored carefully. The basic principles are the same for both types of encephaloceles: removal of unnecessary herniated contents into the sac, watertight closure of the dura, repair of bone

1286 Pediatric Neurosurgery defect, closure of skin in order to achieve good cover and acceptable cosmetic result. This is necessary to avoid damage to the sac with possible infection and to prevent further herniation of the intracranial contents. Most of our children are operated a week or two after birth following stabilization of the child. Repair of occipital encephalocele is performed with the child in prone or lateral position, skin incision is made over the lateral aspect of the dome of the sac in order certain that there will be enough skin to approximate the scalp edges. The CSF must be allowed to come out for the sac to collapse. This is very important step to inspect the intradural space and determine the dura required for closure over the encephalocele remnant and then circumscribe the entire encephalocele with a dissecting scissors. The herniated brain must dealt with conservatively. Usually, most of the herniated brain tissue is not functional. However, the viability of the herniated brain tissue may be examined preoperatively with neurophysiological studies such as visual evoked potentials (13,19,20). Particular attention must be paid to the blood loss from major sinuses around the torcula, to vital brain structures like brain stem and air embolism. The marginal skin edges can then be trimmed appropriately and the scalp closed most easily in the traverse plane whenever possible. Post operative monitoring is of paramount importance as 60 to 70% of children develop hydrocephalus. In some babies in whom ventricules were already large have had hydrocephalus treated first before excision of encephaloceles (16,19,20,27,28,31,43). Frontoethmoidal encephaloceles can be operated electively and in the presence of hydrocephalus, the later will be treated first. Basic principles apply here too with more emphasis on reconstruction of the external bony deformities leading to hyperthelorism. The contents into the dural sac consist of glial tissue and can be resected. Usually one stage reconstructive procedure is performed (24,25). Patient is in supine position with the head in a neutral position but elevated by 30°. The skin is infiltrated with 0.5% lidocaine with 1/200,000 parts epinephrine. A standerd bicoronal incision is used for the intracranial part of the operation. Bifrontal craniotomy is performed for exposure of the floor of the frontal fossa. The approach to the lesion is always extradural. After resection of the fibrotic and gliotic tissue in the encephalocele, the defect is repaired with bone harvested from the bone flap (14,22,25) , and dura is repaired using or galeal graft. The extracranial part of the operation begins with the incision over the facial mass (Vertical “S” type incision in small masses and “λ” incision in larger ones) (20,24,25,42). careful dissection is performed under the skin and the periorbita followed by total removal of the extracranial part of the encephalocele, the redundant skin is excised. If there is associated nasal bone deformity, treatment is performed with cranial bone graft harvested in the early stage of the operation. Wire and screw fixation is performed after giving an appropriate shape to the graft. The bone flap is replaced and the scalp is closed in a routine manner (Fig. 5 ). Antibiotherapy is prescribed for a minimum of 48 hours (20,26,42). In patients with no true hypertelorism (telecanthus due to lateral displacement of the medial orbital walls), the medial orbital walls are excised with an osteotome and placed in normal place with the concave side facing now the orbit and the convex facing the nasal

Encephaloceles

1287

bone. Transnasal fixation is achieved during the same operation with a pair of buttons to remain in place for 3 weeks. In patients with true hyperthelorism, excision of herniated mass, dural defect repair, and standard hypertelorism correction (frontal osteotomy, periorbital and infraorbital osteotomies to free the orbits, then orbits are drawn together to the median to reconstruct the new nose) are performed at the same operation (24,25,33).

Fig. 5 Picture taken 5days after the operation

CONCLUSIONS Children with anterior defects and encepahloceles have a much better prognosis because of minimal amount of herniated brain. The majority of these patients will have a normal life if no other congenital defects are present (19,20,26). Posterior encephaloceles have a much poorer outcome. Only 20-30% of children will have a normal intellect, while a 50% of them will also have hydrocephalus and associated complications (8,19,23,26,36).

REFERENCES 1. Agthong S, Wiwanitkit V. Encephalomeningocele cases aver 10 years in Thailand : a case series. BMC Neurol. 2002; 2:3. 2. Aydin MD. Atretic cephalocele communicating with lateral ventricle. Child’s Nerv Syst. 2001 ; 17:679-680. 3. Bannister CM, Russel SA, Rimmer S, Thornej A, Hellings S. Can prognostic indicators be identified in a fetus with an encephalocele? Eur.J Pediatr Surg. 200; 10 (1): 20-23. 4. Bartels RH, Merx JL, Van Overbeeke JJ. Falcine sinus and occipital encephalocele: a magnetic resonance venography study. J Neurosurg. 1998; 89:738-741. 5. Bassuk AG, McLone D, Bowman R, Kessler JA. Autosomal dominant occipital cephalocele. Neurology. 2004 ; 62 : 1888-1890. 6. Bhagwati SN, Mahapatra AK. Encephaloceles and anomalies of the scalp In : Choux M, Di Rocco C, Hockley AD, Walker ML, eds. Pediatric Neurosurgery. London : Churchill Livingtone. 1999: 101-120. 7 .Bozinov O, Tirakotai W, Sure U, Bertalanffy H. Surgical closure and reconstruction of large occipital encephalocele without parenchymal excision. Child’s Nerv Syst. 2005; 21:

1288 Pediatric Neurosurgery 144-147. 8. Brown MS, Sheridan-Preira M. Outlook for the child with a cephalocele. Pediatrics. 1992 Dec; 90 (6): 914-9. 9. Date I, Yagyu Y, Asari S, Ohmoto T. Long-term outcome in surgically treated encephalocele. Surg Neurol. 1992 Aug: 40 (2): 125-30. 10. David DJ, Simpson DA. Fronto-ethmoïdal meningoencephaloceles. Clin. Plast . surg. 1987; 14:83. 11. David DJ, Timothy WP. Cephaloceles: classification, pathology and management. Word J. Surg. 1989; 13: 349-357. 12. Diebler C, Dulac O. Cephaloceles: clinical and neuroradiological appearance, associated with cerebral malformations. Neuroradiology. 1983; 25 (4): 199-216. 13. Engel R, Buchan GC. Occipital encephaloceles with and without visual evoked potentials. Arch Neurol. 1974; 30: 314. 14. Eppley BL, Hathaway RR, Kalsbeck JE, Rosenthal M. Craniofacial correction of giant ethmoidal encephalomeningocele. J Craniofac Surg; 1999; 10 (2): 111 – 116. 15. Ertunc D, Tok EC, Kaplanoglu M, Polat A, Aras N, Evruke C. Concordant occipital encephalocele in monoamniotic twins.J. Perinat. Med. 2005; 33: 357-359. 16. Gallo AE Jr. repair of giant occipital encephaloceles with microcephaly secondary to massive brain herniation. Child’s Nerv Syst. 1992; 8 (4): 229-30. 17. Habal MB. Cranio-facial correction of the occipital encephalocele. The Journal of cranio-facial surgery. 1993; 4:4. 18. Holm C, Thu M, Hans A, Martina M, Silvia GS, Moritz S, Wolfgang M. Extracranial correction of frontoethmoidal meningoencephaloceles: feasibility and outcome in 52 consecutive cases. Plast Reconstruc Surg. 2008; 121 (6): 386e – 395e. 19. Hoving EW. Nasal encephaloceles. Childs Nerv Syst. 2000; 16 (10 – 11): 702 – 706. 20. Kalangu K, Levy LF, Makarawo S, Nkrumah FK. Anterior encephalocele – our experience in Harare, Zimbabwe, after the introduction of Ct Scanning. Centr Afr J Med 1990; 36 (9): 213 – 218. 21. Kaur I, Mishra J. Occipital encephalocele. J. India M.A. 1995; 53 : 4. 22. Komolafe EO, Shokunbi MT, Malomo AO, Oluwastosin OM, Adeolu AA, Tahir C. Encephalocele and associated sklull defects. WAJM.. 2003; 22 (1): 35-37. 23. Lorber J, Schofield JK. The prognosis of occipital encephalocele. Z Kinderchir. 1979; 28: 347-351. 24. Lello GE, Sparrow OC, Gopal R. Management of fronto ethmoidal (sincipital) encephalocele. J Craniofac Surg 1999; 10 (2): 135 – 139. 25. Lello GE, Sparrow OC, Gopal R. The surgical correction of fronto-ethmoidal meningo encephaloceles. J Cranio Maxillofac Surg. 1989; 17 (7): 293 – 298. 26. Lo BW, Kulkami AV, Rutka JT, Jea A, Drake JM, et al. Cllinical predictors of developmental outcome in patients with cephaloceles. J neurosurg Pediatrics. 2008; 2 (4): 254 – 257. 27. Mahapatra AK, Gupta PK, Dev EJ. Posterior fontanelle giant encephalocele. Pediatr Neurosurg 2002; 36: 40-44. 28. Martinez-Lage JF, Piqueras C, Poza M. Atretic cephalocele in the adult. Acta Neurochir (Wien). 1997; 139: 585-586. 29. Martinez-Lage JF, Poza M, Sola J, Soler CL, Montalvo CG. The child with a cephalocele : ethiology, neuroimaging and outcome. Child’s Nerv Syst. 1996; 12:540-550. 30. Martinez-Lage JF, Sola J, Casas C, Poza M, Almagro MJ, Girona DG. Atretic cephalocele : the tip of the iceberg. J Neurosurg. 1992; 77: 230-235. 31. Moorthy RK, Rajshekhar V. Management of hydrocephalus associated with occipital encephalocele using endoscopic third ventriculostomy: report of two cases. Surg Neurol. 2002; 57: 351-355.

Encephaloceles

1289

32. Nager GT. Cephaloceles. Laryngoscope. 1987; 97: 77-84. 33. Naidich TP, Altman NR, Braffman BH, Mc Lone DG, Zimmerman RA. Cephaloceles and related malformations. Am J Neuroradiol . 1992; 13: 655-690. 34. Otsubo Y, Sato H, Ito H. Cephaloceles and abnormal venous drainage. Child’s Nerv Syst. 1999; 15: 329-332. 35. Shokunbi T, Adeloye A, Olumide A. Occipital encephaloceles in 57 Nigerian children : a retrospective analysis. Child’s Nerv Syst. 1990; 6: 99-102. 36. Simpson DA, David JD, With J. Cephaloceles: treatment, outcome, and antenatal diagnosis. Neurosurgery. 1984; 15: 14-21. 37. Smith OD, Neumann AM Jr, Sirimana KS. Occipital meningocele and Mondini deformity of the cochlea. The Journal of Laryngology-Otology 2001; 115: 71-73. 38. Suwanwela C, Suwanwela N. A morphological classification of sincipal encephaloceles. J. Neurosurg. 1972; 36 (2) : 201-210. 39. Suwanwela C. Geographical distribution of frontoethmoidal encephalomeningocele. Br J Prev Soc Med 1972; 26: 193 – 198. 40. Tekkök IH. Triple neural tube defect – cranium bifideum with rostral and caudal spina bifida – live evidence of multi-site closure of the neural tube in humans. Child’s Nerv Syst. 2005; 21: 331-335. 41. Thu A, Kyu H. Epidemiology of fronto-ethmoïdal encephalomeningocele in Burma. Journal of Epidemiology ang Community Health. 1984; 38: 89-98. 42. Wolf B, Kalangu K. Early repair of frontoethmoidal meningoencephalocele in Bulawayo, Zimbabwe. Trop Geogr Med. 1993; 45 (4): 182 – 183. 43. Yamada K, Miura M, Matsuumoto J, Uchino T, Kondo Y, Ushio Y. An occipital encephalocytocele involving both sides of the lateral ventricules. Pediatr Neurosurg. 2000; 33: 279-283.

1290

Spinal Dysraphism PATRICK DHELLEMMES, MD, MATTHIEU VINCHON MD, PhD Department of Pediatric Neurosurgery, CHRU Lille Key words: spinal disraphism, neural tube closure, myelomeningocele, hydrocephalus, tethered cord, spina bifida, myelolipoma

INTRODUCTION Spinal dysraphism results from a closure abnormality of the distal part of the neural tube. We will focus on the lumbo-sacral lesions. There are two main types of spinal dysraphism: open dysraphism, comprising myelomeningocele which represents the most severe form, and closed dysraphism made up of certain malformations on which we will have a short overview, as they result from a different embryologic mechanism and carry a better prognosis. Improvements in terms of antenatal diagnosis and maternal diet represent a recent useful tool in the prevention of myelomeningocele. Although malformative diseases, spinal dysraphisms are potentially progressive, thus requiring a permanent follow-up throughout life.

EMBRYOLOGICAL BACKGROUND The nervous system develops from the differentiation of the ectoderm, the external superficial and dorsal layer of the embryo. This thickening later transforms into the neural groove (primary neurulation); and later run to the neural tube, which closes gradually from the central part to the extremities. Secondary neurulation then leads to the development of the neural tube into the tail bud; this part of the neural tube then regresses, while the spinal cord and filum terminale differentiate and the conus medullaris ascends to its final position (retrogressive differentiation). Spinal dysraphisms that will be discussed in this presentation result from a closure failure of the distal part of the neural tube, known as caudal neuropore. Dysraphic lesions are caused by abnormal separation of the different layers of the embryo during this long and complex process. The most frequent and severe form is the non-closure of the caudal neuropore (27th day), responsible for myelomeningocele. This is associated with a posterior herniation of the nervous tissue, surrounded by remnants of meninges (this corresponds to spina bifida aperta). Other types of spinal dysraphisms occur later between the 29th and the 48th day; these lesions are completely covered by the skin (this form is described as spina bifida occulta), which often presents some skin abnormalities guiding the diagnosis. We will describe in this chapter the meningocele, myelolipoma, diastematomyelia, and the dermal sinuses, which are the most frequent.

Spinal Dysraphism

1291

MYELOMENINGOCELE Myelomeningocele (MM) is the most severe form of dysraphism. It involves a lumbosacral wound of variable length where the abnormal spinal cord is exposed (Fig1). This segment of the spinal cord and corresponding roots are as a whole non-functional. The prognosis depends on the level of the lesion on the spinal cord. As the lesion extends upward, the functional prognosis worsens and may include at least sphincter dysfunctions (S2, S3 roots) often associated with paraplegia of various severity (distal form S1, L5 roots). The most severe forms (L4 to D10) are incompatible with ambulation. MM is a disease of the whole cerebrospinal axis (Fig. 2) as it is often associated with a type II Chiari malformation (80%), a downward herniation of the cerebellar tonsils and medulla oblongata through the foramen magnum responsible for a hydrocephalus. Hydrocephalus is a major problem in patients with MM, affecting roughly 80% of patients. Other associated malformations involve the brain stem, the parietal lobes (polymicrogyria), hypoplasia of the corpus callosum, and cerebellar dysplasia. The latter is considered responsible for cognitive impairment, which affects more or less severely the majority of patients with MM. The skeleton is often affected: cranial

Fig. 1 schematic drawing of the myelomeningocele in the sagittal (left) and axial (right) views. The spinal cord (placode) is immediately apparent at the center of the defect of skin and meninges.

Fig. 2 brain lesions associated with myelomeningocele: type II Chiari malformation with hydrocephalus.

1292 Pediatric Neurosurgery lacunae (a specific pattern distinct from fingerprinting associated with hydrocephalus) and vertebral malformations (severe kyphosis in upper lumbar MM). In older children and adults, evolving symptoms may occur either due to the scarred spinal cord attached to the lumbo-sacral region (tethered cord syndrome), shunt malfunction, or the development of a syringomyelia.

Genetics of myelomeningocele It has been demonstrated that folic acid was implicated in the neural tube closure. Development of myelomeningocele could be favored by folic acid deficiency. However MM also occurs in women with a normal diet, and it is unclear whether failure of the mother to take folic acid up, or of her fetus to use it to build its nervous system, is responsible for the development of MM. Inherited deficiency in folic acid metabolism might explain the familial occurrence of MM. Whatsoever, experiences in Ontario have shown that supplementation of the diet with folic acid can halve the incidence of MM. MM can also be associated with other environmental factors, like antiepileptic drugs (Carbamazepine, Valproic acid) or fetal alcohol syndrome. There is also a possibility, of an unconfirmed genetic predisposition. This is probably of a polyallelic type: the incidence of myelomeningocele is high among some ethnic groups (populations of Celtic descent) and among children from couples with a previous child with myelomeningocele (about 3%). In practice, this means that a woman who has conceived a child with MM requires monitoring for the next pregnancy, which must be planned, and prophylaxis with folic acid is mandatory. In France, the incidence is 0.5‰ and this is twofold in the western region. Incidence can vary with time; for instance in Britain, it ranged from 1.2 – 4.5 ‰ before1980 and it is presently between 0.7 – 2.5‰. Prevention of myelomeningocele Folic acid intake reduces the risk of developing myelomeningocele by half to twothirds. In France, it is prescribed to couples at risk (past history of myelomeningocele or epilepsy). It should be administered at least one month prior to conception and should continue two months after, at the dose of 5mg/day. It is advised that Folic acid be systematically prescribed to all pregnant women at the dose of 0.4mg/day.

Antenatal Diagnosis In France, most cases of myelomeningocele are diagnosed prior to birth using obstetrical ultrasonography. During this exam the cephalic region (where the general aspect of the skull is generally modified with resulting lemon-like aspect) must be carefully examined as well as the posterior fossa where the cerebellum is crushed against the skull with a non-visible 4th ventricle as the result of Chiari malformation (banana sign). Lateral ventricles are often dilated. In the presence of these characteristic findings, a careful analysis of the spine (which may be difficult because of the position of the fetus) must be performed. It is through this analysis that the opening of the lumbo-sacral canal and inconstantly a meningeal pouch will be identified (Fig. 3).

Spinal Dysraphism

A

1293

B

Fig. 3 prenatal ultrasound: A) Skull deformity with frontal the "lemon-shaped" forehead. B) Spina bifida with lumbar cyst. (By courtesy of Dr AS Valat, with permission)

Maternal blood or amniotic fluid dosage of alphafetoprotein (an increase is not specific of myelomeningocele) and amniotic fluid dosage of acetylcholinesterase may help in the screening. Amniotic fluid dosage of acetylcholinesterase is more specific of an opened neural tube. Once antenatal diagnosis has been made, the pregnant woman is often sent to the neurosurgeon where she will receive education and counseling on neural tube defects including its exact nature, its implication on the child daily activities and available treatments. In fact, the treatments are mostly palliative, since no one can prevent the heavy burden of disability in these children. The future parents are also informed that the MM is not always operable and that the overall mortality rate is around 20% even in the best hands and with all the means of modern medicine. The decision whether to continue or interrupt the pregnancy is taken by the parents (who have been informed) and will take into consideration the age of the pregnancy, parents’ beliefs and the country legislation. The neurosurgeon's role at that stage is thus mostly of information.

Neonatal assessment When the diagnosis is borne, with or without an antenatal diagnosis, the dorsolumbar wound is covered with sterile and wet dressing and the neonate is referred to the service of neurosurgery where an initial work-up is done and a therapeutic decision taken with the parents’ participation. The myelomeningocele (Fig. 4) Its upward extension: The neurologic level corresponds to the first opened vertebra, estimated by careful palpation of the newborn's back. Its covering: It is either a ruptured meningocele (with CSF dripping from the wound) or an absence of meninges associated with an outflow of cerebrospinal fluid; in this case, there is a short-term risk of infection. It may also be a closed envelope; in this case there

1294 Pediatric Neurosurgery

A

B

C

Fig. 4 Myelomeningocele at birth: A) Distal variant with only sphincter disturbance. B) lumbo-sacral level with sphincter disturbance and L5-S1 level palsy. C) Large ruptured malformation up to the level L1 with complete paraplegia

is always a risk of secondary leakage of cerebrospinal fluid. If left untreated, the wound may heal spontaneously, especially when the lesion is already partially skin-covered. Paraplegia Its level is estimated by observing spontaneous and induced movements of the neonate. The neurological level corresponds grossly to the location of the lesion on the spinal cord but some discrepancy is often found (upward as well as downward). For a spinal lesion involving L3 and L4, it must be anticipated that the affected child will be wheelchair-bound, whatever the quality of surgery and physical therapy. Sphincters Sphincter dysfunction is always present even in MM affecting the lowest spinal levels. A spontaneous dribbling of urine and emission of meconium are present at birth with an opened anal sphincter (Urinary retention is rare). Bladder and sphincters functions will be evaluated in detail later in life. Orthopedic assessment Equinism, hip dislocation and spinal abnormalities must be looked for using standard radiologic procedures. Chiari Malformation Although present in a majority of patients, it is clinically apparent in a small number of cases. It usually manifests early after birth by breathing problem (Stridor) or swallowing difficulties, which indicate a poor vital prognosis, as these, are signs of either a compression of the medulla oblongata or a malformation of cranial nerve nuclei originating from this structure. It can become clinically overt later in life as a manifestation of shunt obstruction, and explains the high mortality of shunt failure in this group of patients.

Spinal Dysraphism

1295

Hydrocephalus It may be present prenatally, at birth, or develop a few days or weeks after birth requiring in 85% of cases CSF diversion (most often through a ventriculo-peritoneal valve). Recently, the interest of endoscopic ventriculocisternostomy with plexectomy has been put forward by Warf et al. (22), which avoids shunting. Confirmation of these interesting data by other teams is necessary. The child follow-up is clinical (palpation of the fontanel, measuring of the head perimeter) and more important, by repeated transfontanellar ultrasonography. Associated cerebral malformations and mental retardation These are inconstant findings. Except for some specific severe cases of microcephaly (associated with fetal alcohol syndrome), large antenatal hydrocephalus or high spinal lesions (2), these abnormalities will be assessed later. The prognosis and the decision to close the myelomeningocele are taken at the end of this assessment. This surgical procedure will nevertheless not improve the neurological prognosis, only prevent worsening, and will engage into a lifelong process of care requiring the active participation of the parents. The management is then discussed with the parents who will choose between two possibilities: Either an immediate closure of the myelomeningocele (ideally before 24 hours) followed by a complete management including the treatment of hydrocephalus, daily physiotherapy, bladder and sphincter functional evaluation, etc…. Or a palliative treatment, which will not entail medical or surgical procedures except analgesics. The decision for a palliative treatment can be taken by the parents in cases of severe neurological deficits (upper of motor deficit at L3), large hydrocephalus, or associated malformations. It so happens that a child expected to die soon, unexpectedly survives, prompting a revision of the attitude defined initially. Treatment of the hydrocephalus followed by closure of the myelomeningocele after complete spontaneous epidermization therefore needs to be done.

Closure of the myelomeningocele After birth, a protective dressing has to be applied on the myelomeningocele. The surgery must be done (Fig. 5) within 24 hours and will consist of a dissection, under optical microscope (7), of the spinal cord, removal of all residual epithelium and tubulization of the spinal cord by 7/0 stitches. The dura mater is separated from superficial layers and closed with a running suture using 7/0 prolene; the available dura mater is usually large enough to allow a "paletot" type (double layer") closure. The following layer will bring the paravertebral muscles fascia or the residual meningeal pouch which attaches to the skin as close as possible. The subcutaneous layer is approximated as much as possible, using the fibrous ring (which corresponds to the reflection of the

1296 Pediatric Neurosurgery

A

C

B

D

Fig. 5 closure of the myelomeningocele: A) Preoperative view B) Dissection of the spinal cord and section of abnormal (dorsal) nerve roots, excision of redundant skin and of epidermis which was adherent to the placode, circumferential incision of the dura mater. C) Closure of the dura mater D) Skin closure using a "Y-shaped" suture in order to preserve skin vitality and avoid tension.

dural pouch) to anchor tension stitches, allowing skin closure without tension. The skin is closed with 4 or 5/0 separated stitches. The procedure is more or less delicate depending on the importance of the skin defect. In case of large skin defects, it may be necessary to fashion bipediculated grafts by making vertical skin incisions in the flanks, the donor site being left to heal under vaseline-impregnated gauze. In case of delayed surgery, the surgical procedure will be done after complete wound healing in order to avoid infection. The scarred skin can be partially conserved in order to obtain a closure of good quality when skin defect is foreseen; the skin cover can be enlarged using an inflating prosthesis. Dissection of the dural sheet and the spinal cord proceeds from the cranial to caudal end, starting in the healthy tissue, often after a laminectomy on the last healthy vertebral level above the lesion. The aim is to dissect and free the spinal cord and its roots from the scar, then rebuild the dural sheet and close the wound as aesthetically as possible. Dissection of the epidermis from the neural placode is necessary in order to avoid the inclusion of epidermis, leading to the constitution of epidermal cyst.

Spinal Dysraphism

1297

Treatment of hydrocephalus The decision on the timing to place a ventriculoperitoneal shunt will depend on the clinical status and ventricular volume monitored by trans-fontanellar ultrasound; of course infection must be ruled out before performing the procedure. Usual midline abnormalities and more specifically of the third ventricle make ventriculocisternostomy difficult and often inefficient during the neonatal period, and we do not use this technique routinely for patients with MM. Indications can however be considered secondarily in the case of an obstructed shunt in an older child, in order to obtain shunt-independency after an anatomical work-up with MRI. Role of orthopedics and physical therapists To do a follow-up from the first days of the lower limbs motor deficiencies and various joints abnormalities (talipes, hip dislocation, genu flessum). A regular monitoring of the spine will also be done, due to the high risk of scoliosis development. An almost daily physical therapy is started right from birth and will last during the entire growth of the child. Role of urologists The clinical follow-up of bladder and sphincter dysfunction is done through regular uro-dynamic tests. Children with an incontinent bladder require a permanent protection; those with urinary retention will benefit from intermittent bladder catheterization 4 to 6 times per day (technique of aseptic catheterization by the parents and secondarily by the child himself). Treatment is not recommended for lower urinary tract infections without fever; On the contrary, any upper urinary tract infection requires adapted intravenous antibiotics. Regular screenings for a possible lithiasis or a vesico-ureteral reflux are also mandatory, as well as monitoring of fecal evacuations since these children are usually constipated and/or incontinent. Neuropsychological evaluation and eventually adjusted education Regular neuropsychological evaluations are necessary for education adjustment. Many studies have attempted to establish the intellectual prognosis from birth: Beeker (2) showed a close relationship between lesion’s site, the head circumference and the ventricular volumes on one hand and subsequent intellectual level on the other hand. Cognitive deficits are caused by the cause of MM ((like fetal alcohol or Valproate), the associated brain malformations, and the initial severity of hydrocephalus and its complications (shunt obstruction and infection). In all cases, the management should take consideration all the medical, intellectual, and socio-economic parameters. Every child will thus needs a personalized management coordinated by a referring physician who can be a pediatrician, a physiotherapist, etc. Negligence is a major aggravating factor especially in sphincter disturbances, which will lead to renal failure (through repeated urinary tract infections) with arterial hypertension

1298 Pediatric Neurosurgery and possible need for renal replacement therapy (dialysis and renal transplantation). In addition to perinatal mortality, renal complications and ventriculo-peritoneal valve obstruction are the main causes of early death in these patients.

Neurosurgical aggravating factors in a child with spina bifida The poor control of hydrocephalus The parents should know the signs of intra-cranial hypertension in relation with a dysfunction of the cerebro-spinal fluid shunt. They must be aware that early reintervention is the key factor conditioning outcome in case of VPS malfunction. The mortality associated with valve obstruction in cases of myelomeningocele is higher as compared with hydrocephalus of other origins (5, 20) probably because of the decompensation of the Chiari malformation. Chiari malformation It is the type II malformation, which includes downward herniation of the cerebellar tonsils and medulla oblongata through the foramen magnum. This malformation is present in 80% of myelomeningoceles. It is clinically evident in 20 to 30% of cases, and surgery for Chiari II malformation will be done in 15% of children with myelomeningoceles. Clinical signs are often severe before the second year, with bulbar dysfunctions (apnea, stridor, cyanosis, aspiration with inhalation pneumonia). Peri-operative mortality is high at this age and sequelae are important because of frequent association with brain stem malformations. In children of age more than 2 years, symptoms are either a re-occurrence of bulbar signs, of which the most severe is a cardiac arrest complicating a neglected obstructed valve and the most insidious is the sleep apnea syndrome or pyramidal signs involving the four limbs. If the Chiari malformation becomes symptomatic, the first step is to verify that the cerebrospinal fluid shunting device is functioning well. If the symptoms persist after surgical verification of the drain, a decompression of the occipito-cervical junction with upper cervical laminectomy associated with an enlargement plasty of the dura mater is to be done. Concerning the surgical technique, note should be taken of the fact that the lateral sinus is in an extremely low situation, sometimes one centimeter below the level of the foramen Magnum. Hence, it is not advisable to dissect the cerebellar tonsils, which are fused, hypervascularized, and adherent to the brain stem. Also, attention should be pain to craniocervical immobilization in a brace because of the risk of severe swan-neck deformation after laminectomy. Tethered cord syndrome It is a group of clinical slowly progressing symptoms (21), due to traction on the distal spinal cord which is adherent to the surgical scar of the myelomeningocele operated at birth.

Spinal Dysraphism

1299

This clinical entity may have several presentations: Deterioration of motor functions of the lower limbs, which sometimes leads to loss of ambulation. This deterioration can occur under the mask of orthopedic problems in multi-operated patients. Worsening of sphincter dysfunction (occurrence of urine leaking between catheterization procedures) Progressing scoliosis, which should raise suspicion of tethered cord, especially when associated with back pain. Pain is often the main presenting symptom: it may be unspecific but tenacious lumbar pain, pain at the site of spina bifida scar, or pain projected to the lower limbs. There may also be Lhermitte’s sign. This worsening can occur at any age, even in adults. It can be triggered by trauma of variable mechanisms (5). Once the diagnosis is suspected a neuroimaging study using craniospinal MRI must be done to rule out other evolving abnormalities: shunt malfunction, Chiari malformation, syringomyelia. A neurophysiologic evaluation must also be performed (ESSP, EMG). A micro-neurosurgical intervention will subsequently follow to free the spinal cord from the scar. In our series (5), 60 cases of myelomeningocele had to be re-operated (representing 13.7% of all patients). Clinical signs were variable, motor: 37, sensitive: 10, sphincter: 17, pain: 8, scoliosis: 37. Post-operative aggravations are rare after untethering. Surgery improves more than half of the symptoms and stabilizes others; it is especially efficient for pain and motor signs, and scoliosis becomes painless and more manageable by physiotherapy and, when necessary, by surgery. Syringomyelia It is a cavitation of the spinal cord by the cerebrospinal fluid occurring most often in young adults. It manifests by motor and sensitive abnormalities mainly of the upper limbs, at times intense neuropathic pains or scoliosis in the young child. The treatment is that of the associated Chiari malformation. Dissection of the outlet of the fourth ventricle is more extensive and may require stenting in order to correct the hydrodynamic problem in syringomyelia. At times, the treatment may consist of freeing the spinal cord and less often syrinx cavity drainage to the arachnoid space or peritoneal cavity. Other problems. Allergy to Latex affects 32% of patients for Bowman (3). It must be systematically identified due to per-operative severe complications such as anaphylactic shock. Because of this possibility, preventive strategies should accompany all procedures (urinary catheter placement, surgical intervention….), and these patients should be managed in a latex-free environment from birth. The frequency of epilepsy is twofold higher in patients with a valve (8).

1300 Pediatric Neurosurgery

Cerebral lesions Origin of cerebral lesions They are related either to constitutional malformations of the two parietal lobes or hypoplasia of the posterior corpus callosum. In these cases, brain stem and cerebellar malformations are also associated (Chiari malformation). They can also result from hydrocephalus, which affects the parietal lobes due to the distention of the ventricles. The severity of these lesions reflects that of the motor deficits. Infectious complications of the valve significantly alter the intellectual performances (3, 20). Consequences of cerebral lesions Cerebral lesions determine cognitive impairment that involves lateralization, spatial and temporal orientation, body schemes and praxis. These impairments will more or less severely alter primary school acquisitions. They will also increase the difference between the verbal intellectual quotient (VIQ) and the performance intellectual quotient (PIQ), the latter often lagging 20 points behind the first. Cognitive impairment increases with difficulties in school due to the handicap or to hospital admissions. About 40% require adapted schooling or suffer from school retardation (17). Various studies report that between 25 and 35% of adults with myelomeningocele will have a job (8, 5), which may be an overestimate since jobs in a competitive environment are indeed very few. Mortality Mortality was in excess of 50% in the years 60’s (6). It has dropped to 14% in recent western studies (3).

Conclusion on myelomeningocele Myelomeningocele is responsible for severe evolving multiple handicaps, which require a regular and close follow-up at all ages, by a motivated multidisciplinary medical team. The success of the management of myelomeningocele will depend on the full participation of the parents and will be more effective if it is maintain throughout the child development with no interruption during the transition towards the adult life (5). This malformation is so severe that, in some countries, the legislation in place gives the right to the parents, after the diagnosis has been done, to request for a medically assisted abortion.

OCCULT DYSRAPHIC LESIONS Main characteristics of occult dysraphisms Unlike myelomeningocele, these dysraphisms in general do not have associated cerebral malformation (normal intellectual development, no Chiari, no hydrocephalus),

Spinal Dysraphism

1301

and have few or no initial neurological impairments. However, these abnormalities may worsen with time because of the attachment of the spinal cord realizing the tethered spinal cord syndrome. The tethered cord syndrome is a clinical syndrome in which traction on the spinal cord results in both motor and sensitive deficits associated to sphincter dysfunction, often pain and sometimes spinal deformation (21). This syndrome is the consequence of the spinal cord traction between two points, a fixation of the distal end of the spinal cord by an attached structure (lipoma, bony spur or dural bands…) and the spinal fixation by the lower pairs of dentate ligaments. In general, neurological deficits appear at a stage when spinal cord lesions are not recoverable, and surgery at this stage mostly stabilizes the patients. By contrast, when deficits occur in the postoperative period, recovery is generally good. These considerations justify the proposition of prophylactic “neurosurgical freeing of the spinal cord” even in asymptomatic patients, with the risk of creating one in which there are good chances of recovery.

Meningocele and meningocele manqué These lesions are herniations of the meninges through a posterior spinal defect. The herniated sack is variable in size, filled with cerebrospinal fluid but can also be limited to a simple meningeal tube. The skin covering the midline spinal defect (located in the majority of cases between L5-S1) is modified. This modification often helps to make the diagnosis at birth. MRI shows the location of the spinal cord, which is usually pulled downward by a short thickened filum terminale, attached at the bottom of the meningocele under the skin (fig 6 and 7). The problem of antenatal diagnosis is to differentiate the meningocele from myelomeningocele. The diagnosis of meningocele is based on the notion of a normal brain with an anechogenous meningocele content. In addition, neither alphafetoprotein nor acetylcholinesterase is detected in the amniotic fluid. These data are thus of

A

B

C

Fig. 6 schematic drawing of the meningocele: A, sagittal view, B axial view: large meningeal pouch with an accessory filum attached to the pouch underneath the cutaneous dimple and causing spinal cord tethering. C) Meningocele manqué, sagittal view, without meningeal pouch, with only skin anomalies and a short filum with tethered cord.

1302 Pediatric Neurosurgery

Fig. 7 large meningocele without neurological deficit

paramount importance for antenatal counseling. The treatment, which is usually performed at the age of 6 months involves a microneurosurgical dissection of the meningocele neck, the opening of the dural sack, the section of the filum terminale, the resection of redundant skin and dura mater, and finally the closure in layers.

Myelolipoma In its most common form, myelolipoma presents as a fatty mass attached to the lower extremity of the spinal cord, which is fixed and protrudes through a spinal defect (generally at the level of L5S1) and extends without limits into the subcutaneous tissues (fig 8). It is made up of connective tissue and adipocytes, which are histologically normal. Embryologically, the origin is still debated: it may arise either from multipotent cell migration during the cartilaginous and meningeal development or may also arise from a persistent caudal mass of multipotent cells resulting from a defective secondary neurulation. There are also two groups: - With normal number of sacral vertebrae - With sacral agenesis which is part of the Currarino syndrome which also includes perineal malformations (anal imperforation) and is due to a mutation of the gene HLXB9. Clinical presentation Lipoma is rarely diagnosed before birth. At birth, it is suspected because of specific cutaneous signs at the same level: lipomatous mass, dermal sinus, cutaneous angioma, tubercle, dermal appendage, etc. (fig 9).

Fig. 8 schematic drawing of a myelolipoma, lateral and axial views

Spinal Dysraphism

A

B

1303

C

Fig. 9 various skin lesions associated with a myelolipoma. A) Swelling cause by a subcutaneous lipomatous mass. B) Midline appendage at the lumbo-sacral level. C) MRI showing a low-lying conus with the cord tethered and compressed by a large lipoma, the latter being in continuity with the subcutaneous mass.

If the diagnosis is not made from cutaneous signs, it is made later when neurological symptoms develop because of tethered cord syndrome, with sphincter dysfunction, pain, and/or motor deficits in the lower limbs. At that point, the postoperative outcome of these deficits is uncertain. The lipoma may be asymmetrical (generally developed on the left), in association with asymmetrical development of the lower limbs, generally the left leg being shorter and slimmer (robin's leg).

Work up of a myelolipoma MRI It is the gold standard for the diagnosis of myelolipoma (T1 and T2 weighted sequences in he three planes). This imaging technique may help in the differentiation of the various anatomico-clinical types (4, 11, 13). Lipoma of the filum, which is an enlarged and thickened filum terminale, without involvement of the nerve roots, and thus the most favorable form regarding surgical resection and clinical outcome. Lipoma of the conus medullaris Dorsal lipoma: ideally, lipoma is purely dorsal and the nerves roots arise anterior to it allowing atraumatic dissection of the lipoma from the spinal cord. Chapman describes a transitional form in which the lipoma is asymmetric and some roots cross the lipoma before they enter into the foramina, making dissection more difficult since these roots may be difficult to spare. Caudal lipoma: fixating the spinal cord at its lower extremity and sometimes

1304 Pediatric Neurosurgery embedding the last sacro-coccygeal roots within it. Complex forms In cases of lipomyelomeningocele and lipomyelocystocele, the nervous tissues (and a fluid pouch) are herniated out of the spinal canal. Theses malformations present generally with neurological deficits. Evaluation of bladder and sphincters is first of all clinical: • Urinary tract infections, sometimes upper urinary infection with life-threatening pyelonephritis • Dribbling • Effort incontinence • Short intervals between evacuations • Looking for post-micturitional residue (with catheterization and/or ultrasound) • Study of the anal sphincter Then, urodynamic work-up with cystomanometry and EMG of the urethral sphincter. In case of abnormalities of the previous tests, bladder and kidney ultrasound, cystography and renal scintigraphy are necessary. Natural history of myelolipoma It is characterized by the risk of tethered cord syndrome with delayed neurological deficit (sphincter, sensitive and motor dysfunction) most often asymmetrical, neuroorthopedic disturbances with asymmetric growth of lower limbs (to be differentiated from congenital asymmetry) and sometimes scoliosis; the latter being generally related to radicular involvement in transitional lipoma. Treatment of lipoma It is a micro-neurosurgical treatment. When the lipoma is located at the filum terminale, the treatment is usually simple and is limited to the resection of the lipomatous filum. The surgical indication is straightforward and postoperative follow up is uneventful. In the other forms, the treatment consists of the reduction of subcutaneous and intraspinal lypoma, aiming at decompressing and untethering the spinal cord. Dissection starts by exposition of the upper level of the spinal defect, then subperiosteal laminectomy or laminotomy of the last normal vertebrae in order to open the dura mater at a point where it is normal, then move downward while identifying the roots and the dura mater (which should be spared for closure); The resection of the lipoma should be as close as possible to the placode, sparing the spinal cord (4). This procedure may be difficult due to the cauda equina roots embedded in the lipoma. In most cases, the spinal cord can be separated from the lipoma and the limits of the neural placode can be approximated by a few stitches in order to reduce the risk of refixation. In rare cases, the dural defect may be so important as to necessitate dural plasty with a substitute. This surgical procedure is performed under microscope approximately at the age of six months but it does not shield totally from a delayed aggravation; therefore some authors (23) advocate to operate only symptomatic patients. This approach implies a close follow-up of all screened children for many years.

Spinal Dysraphism

1305

Post-operative follow-up The rare resolution of pre-operatory deficits argue in favor of early surgery approximately between the ages of 6 to 9 months. When surgery is carefully conducted, early post-operative complications are rare. Delayed aggravations are still possible (19,23), either of neurotrophic type due to radicular dystrophy or secondary to spinal cord refixation. This gradual neurological worsening after prophylactic surgery advocates the proposition of these authors to closely follow up all asymptomatic patients who must only be operated when becoming symptomatic.

Diastematomyelia and diplomyelia Diplomyelia originally means « doubled spinal cord ». The vocable diastematomyelia depicts more correctly this malformation, in which the spinal cord is transfixed by an opening ("stoma"), generally associated with a fibrous band or bony spur. In half of cases, this malformation is secondary to a bony spur transfixing the dural sack anteroposteriorly (sometimes obliquely) almost on the midline. The spinal cord is therefore divided into a left and a right cord, each giving rise to two groups of left and right nerve roots. Split cord malformations result from early defect of the midline during gastrulation (Hansen's node migration and notochord formation). The bone spur is present early in the intra-uterine life and the spinal cord is then split into 2 parts by this spur during antenatal growth of the spine which is faster than that of the spinal cord. The lower part of the split spinal cord is attached to the spur and this may be symptomatic (fig 10). In some cases, the spinal cord is split without any bone spur, which is replaced by a fibrous band. Pang 10 , 11) in 1992 proposed a unifying embryogenetic theory describing the two aspects of diastematomyelia: The type I with a bone spur embedded in a dural sheet and the type II with a unique dural envelop; the splitting of the spinal cord occurring either on a fibrous band or even spontaneously. These two types may be derived from the same ontogenic error, which is the development of an accessory neurenteric tube (during the gastrulation), connecting the yolk sack to the amnion leading to the splitting of both the notochord and the neural plate. To the available literature, we will join our experience on 35 cases of patients we treated from 1977 to 2006. Epidemiology Diastematomyelia affects girls in 66 to 94% of cases (24 girls for 11 boys in our series). Antenatal diagnosis is possible (3 personal cases), suspected during ultrasonography exam, it will be confirmed either with MRI or antenatal tomodensitometry. Clinical picture The diagnosis is suspected on the basis of neuroorthopedic, sphincter or cutaneous signs, of which the most typical is the presence of a faun-like tail at the same level as the bone spur (tuft of thick dark hair implanted on the back, 15 cases out of 35).

1306 Pediatric Neurosurgery

A

B

C

Fig. 10 diastematomyelia A) Schematic drawing of diastematomyelia, lateral and axial views, with a bony spur transfixing the spinal cord; the latter is split in two over several centimeters above the level of the spur. B) 3D CT-scan, axial view, showing the bony spur C) Split cord and bony spur evidenced on MRI, frontal view.

Vertebral malformations are often present, which will be responsible for scoliosis, vertebral block, cuneiform or butterfly-like vertebras, and progressive deformation with growth. Diastematomyelia is diagnosed with MRI, which must be studied in the three planes. Bone malformations, including the spur, are best diagnosed using thin slides CT scanner and tridimensional reconstructions. Treatment The treatment is micro-neurosurgical and aims at untethering the spinal cord and reestablishing a unique meningeal tube. In Type I (18 cases): A limited laminectomy is performed as close as possible to the bone spur. Performing laminectomy should be performed with consideration for vertebral malformations, which include partial agenesis or fusion, and for the direction of the bone spur, which may be asymmetric and oblique. The dural sack is opened around the bone spur and on the median line; the fibrous band attaching the spinal cord is cut; the dura mater is incised along the superior edge of the bone spur; this region is the site of a dense arterial and venous network, and careful hemostasis of the epidural veins is done before the complete excision of the spur which should be as complete as possible most often done using a narrow rongeur or a sharp drill. The dural sheath of the spur can then be resected and the dura mater closed on his anterior then posterior aspect. In type II diastematomyelia (17 patients of which 14 operated), prophylactic surgery is proposed when the spinal cord is attached, when there are other associated dysraphisms or when motor/sphincter deficiencies are present. One should remember that there may be congenital asymmetry of lower limbs growth secondary to an asymmetry of spinal cord

Spinal Dysraphism

1307

diameters, which spinal cord untethering cannot improve. Surgery will be done to resect the fibrous bands and the filum. In addition to vertebral malformations, other malformations can be associated as we have observed in our practice: meningocele (8), short filum terminale (19), myelomeningocele (3), lipoma (5), dermoid cyst (2)… which should be treated simultaneously. A short filum will nevertheless be resected only if it is accessible or otherwise when it is symptomatic.

Prognosis The prognosis of this malformation is theoretically excellent (14): in our study: 29/35 patients have a normal life, 7 have a scoliosis of which 3 were operated, 3 patients have paraplegia and urinary incontinence, but these patients also had a myelomeningocele. Regrowth of the bony spur can occur if the dural sheath has not been resected completely.

Lumbo-sacral dermal sinus This malformation consists of a cutaneous tube penetretating the skin (usually at the level of L5-S1) and ending either in sub-cutaneous tissues or at the level the dura mater or penetrating the dura mater to end on the medullary conus. This tube is covered by a malpighian epithelium that sheds keratinocytes, producing sebum, which accumulates, forming cysts along the dermal sinus or in the neuraxis. When these cysts enlarge, they may compress the nerve roots of the cauda equina (Fig 11). The conus medullaris can be attached to the extremity of the fistula and pulled downwards. The tube can channel germs from the skin (often of intestinal origin) leading to either severe recurrent meningitis or intra-spinal or intra-medullary abscess (9). The diagnosis must be made before infection occurs and relies on a small skin opening of 1 to a few millimeters of diameter centered with hair, and sometime the site

A

B

C

D

Fig. 11 Schematic drawing of the main types of dermal sinuses and complications: A) Dermal sinus with intra-spinal dermoid cyst: causing cauda equina syndrome and meningitis. B) Dermal sinus abutting the dura mater, causing repeated bouts of meningitis. C) Extradural fistula causing recurrent pus discharge D) Cutaneous anomalies composed of an angioma with a tiny dimple centered by some dark and thick hair. Skin lesions may be much less obvious, and diagnosed only at the time of meningeal complications.

1308 Pediatric Neurosurgery of a small discharge of sebum or pus. When infected, the cyst may evolve towards paraplegia with sphincter disturbance in a context of severe meningitis. Owing to the small diameter of the fistula itself, the diagnosis is mostly clinical: tomodensitometry is disappointing and MRI is difficult to interpret, showing more easily complications (cyst and intraspinal suppurations) (1). Surgery should therefore take place before complications occur (around the age of 6 months); it includes a microsurgical exploration of the entire fistula (up to the conus). In case of infection, the dissection becomes difficult (18) and sequelae are frequent in the form of a permanent cauda equina syndrome. Acknowledgment: Dr Vincent DP DIENTCHEU for his availability and translation Conclusion Occult dysraphisms are far less common than myelomeningoceles. The lesions can often be cured. Their antenatal diagnosis is possible but delicate. Unlike myelomeningoceles, there is no indication to interrupt the pregnancy.

REFERENCES 1. Barkovich A, Edwards M, Cogen P. (1991) MR evaluation of spinal dermal sinus tracts in children. AJNR. 12:123-129. 2. Beeker T, Scheers M, Faber J et al (2006) Prediction of independence and intelligence at birth in meningomyelocele. Child’s Nerv Syst. 22:33-37 3. Bowman R, McLone D, Grant J et al (2001) Spina bifida outcome: a 25-year prospective.Pediatr Neurosurg. 34:114-120. 4. Chapman P, Davis K. (1993) Surgical treatment of spinal lipomas in childhood. Pediatr Neurosurg. 19:267-275. 5. Guarnieri J, Vinchon M. (2008) Suivi à l’âge adulte des patients porteurs de myéloméningocéle [Follow-up of adult patients with myelomeningocele]. Neurochirurgie 54:604-614. 6. Hunt G. (1999) Non-selective intervention in newborn babies with open spina bifida: the outcome 30 years on for the complete cohort (Casey Holter lecture). J Neurol Neurosurg Psychiatr. 67:591-595. 7. McCullogh D, Johnson D. (1994) Myelomeningocele repair: Technical considerations and complications. Pediatr Neurosurg. 21:83-90. 8. McDonnell G, McCann J. (2000) Issues of medical management in adults with spina bifida. Child’s Nerv Syst. 16:222-227. 9. Morandi X, Mercier P, Fournier HD et al (1999) Dermal sinus and intramedullary spinal cord abscess. Child’s Nerv Syst. 15:202-208. 10. Pang D, Dias MS, Ahab-Barmada M. (1992) Split cord malformation: Part I: A unified theory of embryogenesis for double spinal cord malformations. Neurosurgery. 31:451480. 11. Pang D. (1992) Split cord malformation: Part II: Clinical syndrome. Neurosurgery. 31:481-500. 12. Pierre-Kahn A, Zerah M, Renier D. (1995) Lipomes malformatifs intra-rachidiens. [Malformative intraspinal lipomas] Neurochirurgie. 41(suppl.1) 13. Pierre-Kahn A, Zerah M, Renier D et al (1997) Congenital lumbosacral lipomas. Child’s Nerv Syst 13:298-335

Spinal Dysraphism

1309

14. Proctor MR, Bauer SB, Scott RM. (2000) The effect of surgery for split spinal cord malformation on neurologic and urologic function. Pediatr. Neurosurg. 32:13-19 15. Rendeli C, Nucera E, Ausili E et al (2006) Latex sensitization and allergy in children with myelomeningocele. Child’s Nerv Syst. 22:28-32. 16. Shurtleff DB, Lemire RJ. (1995) Epidemiology, etiologic factors, and prenatal diagnosis of open spinal dysraphism. Neurosurg Clin North Am. 6:183-193. 17. Steinbok P, Irvine B, Cochrane D et al (1992) Long-term outcome and complications of children with myelomeningocele. Child’s Nerv Syst. 8:92-96. 18. Van Aalst J, Beuls E, Cornips E et al (2006) Anatomy and surgery of the infected dermal sinus of the lower spine. Child’s Nerv Syst. 22:1307-1315. 19. Van Calenbergh F, Vanvolsem S, Verpoorten C et al (1999) Results after surgery for lumbosacral lipoma: the significance of early and late worsening. Child’s Nerv Syst. 15:439-443 20. Vinchon M, Dhellemmes P. (2008) The treatment of hydrocephalus in spina bifida: shunts and problems with shunts. In: Ozek M, Cinalli G, Maixner W. (Eds), The spina bifida: management and outcome. Springer, Berlin, pp. 215-224. 21. Yamada S, Zinke DE, Sanders D. (1981) Pathophysiologiy of “tethered cord syndrome”. J Neurosurg. 54:494-503. 22. Warf BC, Campbell JW (2008) Combined endoscopic third ventriculostomy and choroid plexus cauterization as primary treatment of hydrocephalus for infants with myelomeningocele: long-term results of a prospective intent-to-treat study in 115 East African infants.J Neurosurg Pediatr, 2: 310-316 23. Zerah M, Roujeau T, Catala M et al (2008) Spinal lipomas. In : Ozek, Cinalli, Maixner. (Eds.), Spina Bifida: Management and Outcome. Springer, New York, pp. 445-474.

1310

Traumatic Spine injury in Childhood MATTHIEU VINCHON MD, PhD; PATRICK DHELLEMMES MD Department of Pediatric Neurosurgery, CHRU de Lille Key words: spine injury -- childhood, SCIWORA, shaken baby syndrome (SBS), mild cervical injury, obstetrical spinal trauma

Introduction Spinal traumas are uncommon in children. The management of these rare and often complex lesions is difficult because even in large centers the experience is limited. Each patient represents a new problem, and techniques evolve fast. Some spinal lesions are almost specific of children, like SCIWORA (Spinal Cord Injury WithOut Radiological Anomalies), while others are unique entities, like shaken baby syndrome (SBS) and obstetrical trauma; in other cases, spinal lesions in children may look similar to lesions found in adults, but always with a pediatric twist. In particular, spinal lesions in children show a remarkable potential for healing under orthopedic treatment, but also for complications due to the interference with growth. Overall, application to children of the knowledge of general neurosurgeons on spinal trauma is delicate, tricky, and may require external advice and academic resources. We wrote the present chapter with this aim in view. Basically, any lesion found in adults can also be found in children, but with peculiarities related with the patient's age. Pediatric specificities are summarized in table 1. Because age makes a large difference, each type of lesion, at each anatomical level, in each age group can be viewed as a separate entity. In the present chapter, we shall not deal on all Table 1 Pediatric specificity, consequences in spinal trauma, and implications of treatment.

SPECIFICITY

CONSEQUENCE

THERAPEUTIC IMPLICATION

Skeletal elasticity

SCIWORA Muti-level fractures

Spinal instability is rare fusion has to be extended

Subchondral bone fragility

False-negative X-Rays

Unstable but heals well under orthotic treatment

Growth

Progressive, delayed deformation

Prolonged immobilization

Resilience

No pain, stiffness only

Opposition to treatment: be assertive

Short stature

No adapted implants designed for children

Keep it simple (thread, graft) adapt existing implants

Traumatic Spine injury in Childhood

1311

of these different lesions, but rather try to bring general information, on key features regarding anatomy, pathology, and the natural history of the lesions before and after treatment, in order to give a general idea on the management of these patients. For that purpose, we reviewed the literature and studied 158 cases treated in our institution for spinal trauma since 1974 and age less than 16 years at the time of diagnosis.

Pathophysiology The pediatric spine has some unique properties compared with adults, first of all its growth potential. The spine develops as a differentiation of the paraxial mesoderm, with segmentation of the notochord. Somites appear after the 22nd postconceptional day. Ossification centers appear in the mesenchyme of the vertebral body, then the posterior arch, and fuse in a timely fashion. Disruption of synchondrosis leads to epiphyseal fractures (typically of the dens, which fuses between 5 and 8 years), equivalent to Salter type 1 epiphyseal fracture. The last synchondroses to fuse are the tip of the odontoid and the ring apophysis of vertebral endplates; the latter can be avulsed, leading to a peculiar type of sub-ligamental disc herniation. The curvature of the spine develops postnatally with the acquisition of posture. At birth, a single kyphosis is present, cervical and then the lumbar lordoses develops with the erect position and head control. The spine is the last part of the skeleton to stop growing, around the age of 18-19 years. This means that even in late teenagers, growth can cause progressive deformity after trauma or surgery, and that immobilization and controls need to be more prolonged in children and adolescents than in adults. After segmental fusion of either the posterior or anterior elements, residual growth of the unfused elements can lead to the so-called "crankshaft effect", with progressive deformity; in small children, this threat may lead to propose circumferential (anterior plus posterior) fusion. The pediatric spine presents distinctive anatomical features. The cervical vertebral bodies are wedge-shaped, uncinate processes are absent, occipital condyles and articular facets of the atlas are flat, and zygo-apopyseal joints are horizontal. All these features concur in the bony skeleton having very little inherent stability. In addition, muscles are less efficient in small children because of the shortness of the spinal and transverse processes, and because of the heavy weight of the head, which is not controlled until the fourth month. Because of these features, the fulcrum for cervical flexion is higher in children than in adults, explaining why suboccipital lesions are more common in children, and subaxial cervical trauma affects more often C3 C4 in children than in adults. Stability thus depends mostly on ligaments and muscles, that is to say that muscle tonus and posture reflexes are essential elements of spinal stability, and that their failure can lead to severe compromise of the neural structures. This occurs after SCIWORA, and even with an intact spine, in case of coma or anesthesia [17] On a longer time scale, damage to the erector musculature causes progressive kyphosis; at some point, the vector of erector muscles may become anterior to the axis of motion of the spinal segment, and the muscles act in the opposite direction, aggravating the kyphosis. Progressive kyphosis is a classical complication of posterior spinal approach in children [22].

1312 Pediatric Neurosurgery The pediatric spine has some remarkable mechanical properties. The cancellous bone of the cervical vertebral bodies is elastic, making screw insertion sometimes challenging. By contrast, the discs are highly resilient, almost never torn by trauma, and very difficult to resect surgically. The subchondral bone underlying the disc plate is highly vascularized, and a weakness point of the vertebra (figure 1); fractures of the subchondral bone are highly unstable and may be underestimated on X-ray [20]. On the other hand, the fertile bone in this region accounts for a high potential for healing, and makes these fractures good candidates for orthopedic treatments [1]. Being largely made of soft tissues, pediatric spine has a high resistance to trauma; However, the energy thus absorbed by the spine can be restituted by a movement named "buckling", which is a sudden reverse movement causing a whiplash trauma to the spinal cord. Elasticity of the pediatric spine also explains the frequency of multilevel fractures in children, especially at the thoracolumbar level: the energy accumulated in one vertebra and suddenly released when it fails may be sufficient to fracture the next one, resulting in the typical "staircase fractures". Another typical pediatric feature resulting from spinal elasticity is add inverted commas, which is misleading because these highly unstable lesions may be overlooked (figure 2). Anteroposterior and lateral shear stress can result in impressive sliding of one vertebra relative to the next, without any ligament disruption (figure 3); physiological anteroposterior translation has been measured as much as 3 mm [9]. Under axial distraction load, the pediatric spine can stretch up to 5 cm; however the spinal cord is almost inelastic, which is the biomechanical basis of SCIWORA [20].

Fig. 1 Thirteen-year old male, victim of a traffic accident, found unresponsive by the mobile medical unit. MRI showed spinal cord section and diffuse axonal injuries of the brain. He died two weeks later without having regained consciousness. The fracture of C2 illustrated here is typical of subchondral bone disruption, which is highly unstable.

Traumatic Spine injury in Childhood

1313

Fig. 2 Fifteen-year-old male, victim of high-energy accident (trapped under a bus which capsized), with total paraplegia and acute hypotension. He had major thoracic damage with dissection of the brachiocephalic artery and avulsion of the thoracic duct, along with amputation of right thigh. Imaging showed spinal cord hematoma and lesions of the ligaments (arrows), but without spinal desaxation. During surgery, total disruption of the ligaments and anatomical trans-section of the spinal cord were noted. This aspect is typical of highly unstable, spontaneously reduced lesions.

Fig. 3 29-month female, presenting with torticollis, no notable history of trauma but a recent history of ENT infection. A: plain X-rays, lateral view, shows important anteroposterior shift. The child is immobilized in a rigid collar. B: CT-scan performed after the collar is set in place shows ad integrum correction of the deformation. This example shows the physiological laxity of pediatric spine.

1314 Pediatric Neurosurgery

Epidemiology Children represent 5-7% of cases of spinal trauma, with an incidence of 20 cases per million per year under the age of 19 [9]. The real incidence may be higher since spinal injury is a common feature in victims of fatal injuries who do not reach the hospital [1]. Adelson reckoned that 1,100 children were victims of spinal cord trauma each year in the USA, which is more than poliomyelitis at the peak of its epidemic. Although a male preponderance has been reported in spinal trauma, it appears much less overwhelming for spinal than for head injuries, and sex-ratio appears to fluctuate according to age [10]. In our series, the girls were slightly less affected than boys, contrary to our experience with head trauma [28]. The age distribution in our series shows differences relating to the processes of childhood, with a first spike during the years of learning, after the acquisition of the erect posture; a pause corresponding to the "age of reason"; and a marked increase with adolescence and the practice of brutal sports, motor vehicles and ordalic behaviors (figure 4).

Fig. 4 Number of cases of spinal trauma with gender distribution in our series. After a high number during the first year of life, accounted for by obstetrical trauma and child abuse, a first spike is related with the learning of ambulation and sports, followed by a pause corresponding to the "age of reason", finally a steady increase with adolescence on account of risky behavior. Note that girls are roughly as affected as boys, contrary to the large male preponderance found in intracranial head injuries.

The causes of spina trauma in children are roughly similar in children and in adults, except for two causes which are age-specific: birth trauma and child abuse. In the USA, traffic accidents come first, followed by falls, then gunshot wounds [1]. The importance of sports, especially motor and contact sports, diving and horse riding, accounts for the preponderance of these trauma during the summer months [1, 20]. Household accidents,

Traumatic Spine injury in Childhood

1315

Fig. 5 Etiology of the spinal trauma in our experience. The "mild trauma" trauma category regroups patients for which minimal energy was involved, and concerns patients with a predisposing disease like Down syndrome, osteopenia, and torticollis triggered by mild injury.

including play and falls from stairs or through open windows, occur all year long. The causes of spinal trauma in our series are shown on figure 5. Spinal trauma in children shows a remarkable propensity to affect the cervical level, especially the upper cervical spine [9]; this prevalence is even more marked in infants [20]. Spinal cord lesions are also found mostly (76%) at the cervical level [20] and in infants [1]. Figure 6 clearly shows the correlation between patient's age and level of the lesion, our youngest patient with a lower thoracic fracture being 9.7 years old. This means that in case of lower spine fractures in the young, one should suspect an underlying bone disease.

Fig. 6 Correlation between level of the spinal lesion and age of the patient in our series, showing the high prevalence of upper cervical lesions in infants.

Diagnosis The clinical evaluation on the spot by the mobile medical unit or in the emergency room is the first time of spinal trauma management. Vital functions should be

1316 Pediatric Neurosurgery immediately and repeatedly assessed: the presence of abdominal respiration or diaphragmatic paresis may lead to rapid intubation, which may require fiberoptic endoscopic control. The diagnostic value of hemodynamic instability cannot be overemphasized. The absence of tachycardia in spite of low tension figures may indicate dysautonomia caused by upper cervical spinal cord lesion. Even when they are conscious, children often do not voice spinal complaints, either because they are non-verbal, or opposing, or simply not aware of spinal pain; in such case, spinal stiffness is the only sign, and has the same diagnostic value as pain in adults. Deficits can be underestimated as well, because of immaturity of the central nervous system: the Babinski sign is physiological until one year of age, and mass withdrawal associated with spinal cord section can look very similar to normal motility in infants. The initial presence of a neurological deficit should be pursued thoroughly by interrogating every possible witness, because it has a huge impact on management. Indirect clues such as bleeding in the posterior fossa cisterns, paralysis of the abducens nerve, bruises on the chin (which may all indicate craniocervical dislocation), brain ischemia due to apnea in higher cervical spinal cord trauma, the mechanism of the trauma (child ejected from a car), the presence of spinal trauma in another victim in the same crash, can also lead to the diagnosis. X-Ray imaging is the basis of the diagnosis of spinal trauma because it shows the bone better than MRI does, it is cheap and easily available, fast and requires no or minimal sedation in small children. X-rays detect 79% of lesions in children under 12 years [26]. A consensus has been reached on the X-ray requirements for cervical spine trauma in children [4]; no X-ray is needed if the child is awake, responsive, neurologically intact and has normal, painless motility. The open-mouth anteroposterior incidence for odontoid fractures is useless in children under nine years if the lateral view is normal. Plain X-rays are more and more replaced by total body-CT scan. Whole body X-rays are still useful however to assess the over all state of the entire spine. The drawback of plain X-rays is that the upper thoracic spine, especially the cervico-thoracic junction, is poorly evaluated. CT-scan brings invaluable information on bone lesions, studied in three planes, and is the main diagnostic tool, allowing pre-therapeutic planning as well as treatment follow-up. The indications for imaging are based on clinical evaluation. If the child is comatose, spinal CT is performed during the same session as head CT; if he is awake, a spinal CT scan will be performed whenever he reports pain, shows neurological deficits, spine stiffness, or if his spine cannot be evaluated because of other lesions (e.g. pelvis, lower limbs). Magnetic resonance (MR) is among the major advances of the last decades for the evaluation of spinal trauma, being able to detect lesions of the spinal cord, nerve roots, meninges, spinal soft tissues and even inflammation in the bone (figure 7). It often shows that the skeletal damage is more widespread than suspected, allowing the diagnosis of multilevel fractures. In emergency, MR should however be performed after the CT scan, and in selected patients only because the management of an unstable patient under sedation during the examination may be complicated. MR is indicated in emergency when a deficit is not explained by the CT, and for the diagnosis of lesions of the longitudinal ligaments and of the disc. A number of differential diagnoses should be considered. Torticollis can be caused by ENT infection (Grisel's syndrome) or cerebellar tonsilar herniation. Wedge fractures,

Traumatic Spine injury in Childhood

1317

Fig. 7 Sixteen-year old male, victim of a diving accident, without neurological deficit. T2-weighted MRI, sagittal view, shows edema of the nuchal ligament posteriorly (arrows), and hematoma of the retrophayngeal space and destruction of the C4-C5 disc anteriorly (arrowhead). The patient underwent anterior approach for discectomy, graft and plate with good outcome.

when caused by mild trauma, should raise the suspicion of an underlying disease, medical (spondylitis, osteopenia) or tumoral (histiocytosis of other bone tumor). In our experience, lumbar and lower thoracic fractures under 9 years were always caused by an underlying bone disease. Finally, in case of a deficit not explained by imaging and neurophysiological studies, it should be remembered that hysteria occurs before puberty in females as well as in males.

Spinal traumatic lesions in children: clinico-pathological entities Mild cervical injury Traumatic torticollis is defined by the absence of structural damage, in spite of a sometimes impressive deformation of the spine (figure 3). The regularity of the spacing of the discs and spinous processes, the absence of uncovering of the zygo-apophyseal processes, and the centered position of the odontoid in the atlantal ring allow us to reassure the child and parents. When treated rapidly with pain killers, antispastic drugs, a soft collar and early physiotherapy, the prognosis is however excellent. This problem should not be neglected though, because muscle spasm and ligament retraction can develop rapidly, leading to growth problems and structural deformation. Upper cervical trauma Condyle fractures are commonly diagnosed on head CT, and have generally little impact on the management of the patient. These are wedge fractures with a large

1318 Pediatric Neurosurgery surface of cancellous bone allowing good and rapid healing. Only a soft collar is generally required. When the fracture involves the insertion of the alar ligament, a more rigid and prolonged contention is required. Craniocervical dislocation is a clinico-pathological entity which has changed much since MRI is used regularly. This lesion appears more common and less severe than previously thought, MRI being able to detect subtle bleeding and edema previously undetected by CT. As a consequence, these lesions are not always highly unstable and no longer absolute indications for surgical stabilization, which has a high cost in terms of mobility. Unstable and displaced occipito-axial dislocations (defined by an articular interval greater than 4 mm, carry a poor vital outcome, being often diagnosed at autopsy [20] or in moribund patients [19]. Survivors should undergo occipito-cervical fixation, at a cost of reduced motility. C1-C2 dislocation is generally associated with fracture of the axis because the bone is more fragile than the ligaments [15]. Fracture of the base of the odontoid in children is generally a disruption of the neurocentral synchondrosis. Its prognosis for healing is good but the importance of the dislocation often requires reduction and fusion (figure 8). Neglected fractures of the body or tip of the odontoid can lead to os odontoideum and ossiculum terminale respectively [15]. Isthmic fracture of the axis (the so-called "hangman" fracture) is rare in children, and has been reported in child abuse [8, 13]; if the C2-C3 disc is intact, only orthopedic treatment is indicated. Lesions of the subaxial cervical spine The fulcrum for cervical flexion is higher in children, explaining why cervical spine trauma affects more often the C3 and C4 levels in children than in adults [9]. Because of the fragility of the subchondral bone, subaxial lesions often take the form of Salter type 1 physeal plate injuries. These lesions are highly unstable because of the disruption of all the ligaments, and easily overlooked on imaging. In adolescents, fractures or fracture-luxations are typical complications of diving accidents, caused by axial loading and facilitated by wedged cervical vertebral bodies. The treatment is anterior approach

Fig. 8 Five-year old male, victim of a traffic accident, passenger with seatbelt, presenting with pain and stiffness, no deficit. Plain X-rays, lateral view, show fracture of the base of the odontoid with marked displacement in flexion. Note that the posterior arch of the atlas is thrust against the opisthion and that the C1-C2 interval (arrow) is abnormally wide. The child underwent reduction and posterior fusion (Gallié technique) with good result.

Traumatic Spine injury in Childhood

1319

with corpectomy, graft and plate, not different from adults. Luxation of the zygoapophyseal joints does not occur until late adolescence [15]. In these patients, posterior dislocation may occur without disruption of the anterior elements, which makes it very difficult to reduce, requiring a combined anterior and posterior approach. Lesions of the thoracic and lumbar spine The thoracic cage is relatively rigid, so thoracic fractures are generally found after very violent accidents, often with direct impact. These lacerate the dural sac, damage the spinal cord, and often cause life-threatening lesions of the lungs, and sometimes of the large vessels (figure 2). Because of the fragility of the thoracic spinal cord, neurological deficits, when present, are generally total and do not recover. Thoracolumbar trauma is often caused by flexion and axial loading, often causing multilevel, "staircase" fractures. Even when the CT scan shows a single-level fracture, MRI may reveal undisclosed bone lesions in adjacent vertebrae. For this reason, long arthrodesis (two levels above and two below the fracture) should be preferred to short, adult-type arthrodesis. Other thoracolumbar fractures are caused by axial distraction and flexion of the torso, typically caused by traffic accident with lap-belt [21]. Associated visceral lesions can be severe, and the main factor threatening the patient's life. SCIWORA In a broad sense, the term SCIWORA (spinal cord injury without radiological anomalies) covers several clinicopathological entities, including spinal contusion associated with spondylosis, which occurs in adults; spinal cord concussion (often in teenagers, associated with cervical spine stenosis); true SCIWORA (often in juveniles, with normal spine); and spinal cord trauma in SBS and obstetrical trauma which are agespecific entities. The incidence of true SCIWORA depends on how strictly it is defined; if the absence of spinal lesion has been proved by MRI and late dynamic studies, the incidence is quite low [20]. With advances of MRI, imaging is rarely totally negative, so the meaning of the acronym has shifted in recent years, from absence of radiological anomalies to absence of skeletal damage evidenced by CT (SCI without Osseous radiological anomalies). The cervical spinal cord is the main site, although 15% of SCIWORA may be found at the thoraco-lumbar junction. The causal trauma is typically a whiplash injury with flexion (stretching the spinal cord, which is less elastic than the spine) and extension (thickening the ligamentum flavum, thus narrowing the spinal canal). Apart from spinal cord trauma, stretching of the spinal ligaments also leads to loss of proprioceptive reflexes ("punch-drunk spine"), which could explain the occurrence of delayed deficits, as well as devastating and lasting recurrence of an initially transient deficit [20]. This is to insist on the importance of assertiveness in immobilization after SCIWORA. As a rule, the younger the child, the more complete the neurological deficit, and the poorer the prognosis [10]. Two pitfalls should be avoided in the management of SCIWORA: diagnosis by excess, which means missing a radiologically elusive, unstable spine lesion like subchondral plate disruption; and underestimation of the gravity of the situation by the patient and his family, sometimes by physicians, with absence of compliance to treatment. Our best persuasion skills will be tested by the need to enforce three months

1320 Pediatric Neurosurgery of immobilization in a rambunctious teenager who had transient deficit and does not realize how lucky he is to have recovered. Spinal cord concussion is an entity related to SCIWORA, caused by axial compression loading, typically in contact sports like American football [29]. It occurs when players ram each other, especially defensives doing the "spear tackle"; adolescents with spinal stenosis are predisposed to this complication [21]. Axial loading results in thickening of the ligamentum flavum, which squeezes the spinal cord. Although symptoms resolve rapidly, the main risk is recurrence with poor outcome, and a narrow spinal canal should be considered a definitive exclusion criterion for contact sports. Spinal lesions in child abuse Child abuse is more often caused by forceful shaking (SBS) than beating (Silverman syndrome). In SBS, the repeated flexion-extension trauma, compounded with the heavy weight of the head, the weakness of the spinal muscles and spinal laxity, aggravated by hypotonia when the child loses consciousness or seizes, results in lesion of the upper cervical spinal cord (figure 9). The latter may cause respiratory arrest with resulting cerebral anoxia [12]. As a result, spinal lesions are found in the most severe cases of SBS [28] MRI underestimates the real incidence of these lesions, which are common autopsy findings [6]. Spinal lesions, with or without neurological deficit, are found in Silverman

Fig. 9 Two-month female, shaken baby syndrome, deep coma initially, dead on the third day after her admission. A: spinal MRI, T2-weighted, sagittal view, shows severe edema and swelling in the spinal cord and medulla (white arrow), without evidence of spinal damage. B: autopsy (HE staining) shows disruption of the bulbo-medullary junction (black arrow).

Traumatic Spine injury in Childhood

1321

syndrome, and attest of very violent beating. Isthmic fracture of the axis [8, 13], subchondral bone disruption of C5 with C4/C5 subluxation [25], dislocation of L1-L2 with retrolisthesis and paraplegia [7] have all been described in this context. The management of these lesions in very small infants is a challenge. A combination of surgical, both low-tech (threads and graft) and high-tech (topical use of bone morphogenic protein), and orthopedic techniques will be needed and adapted to each individual case. Obstetrical spinal trauma Spinal lesions caused by birth trauma are rare, and their prognosis is poor [27]. Lesions at the thoraco-lumbar level are more often seen after breech presentation, whereas cervical lesions are more often seen after cephalic presentation. Secondary degradation after recovery can herald syringomyelia [21]. Bone healing requires adequate immobilization for several weeks [11], but posterior surgical fusion may be required. The neurological prognosis is grim; the crucial element of the vital prognosis is respiratory autonomy: if the child can breathe autonomously, survival is possible; if not, limitation of care can be discussed. Antenatal spinal cord lesion can be diagnosed at birth, or during late pregnancy because of a decrease in fetal movements. These lesions can result from in-utero malposition [14], and are thought to result from positional ischemia affecting the spinal cord [16]. Among their differential diagnoses is Werdnig-Hoffman ("floppy baby") disease [21].

Principles of treatment Medical management Spinal lesions must be suspected systematically in severe trauma, and the head should be maintained straight, with the thorax elevated in order to avoid cervical flexion [15], until the spine has been adequately evaluated. The value of antiedematous drugs for spinal cord trauma is debated; generally, these drugs have failed to demonstrate their utility, and some, especially high-dose steroids, have shown serious side-effects. The medical management includes treatment of pain with standard pain-killers and opioids, antiinflammatory and antispastic drugs, the prevention of vein thrombosis, retractions and pressure sores, bladder catheterization and treatment of constipation. This is to say that physical therapy is an essential part of the medical management. Brace Orthopedic treatment is more often successful in children than in adults, however its duration generally needs to be more protracted because of the risk of growth-related deformity. The cast for the custom-made orthosis is molded on the patient, in the upright position whenever possible. Resting points should avoid the incision lines, including the site of bone graft harvesting; follow-up includes inspection of the wound and the search for pressure sores. Braces that immobilize the neck rest on the chin, inducing problems for feeding, sores, and sometimes deformation of the mandible and teeth when immobilization is prolonged. In infants, other problems result of the

1322 Pediatric Neurosurgery deformability of the skull, the strength of the axial musculature, and the need for suckling and napkin care. Semi-rigid solutions with strapping on the forehead, "papoose like clamshell orthosis" [21], are preferred in these patients (figure 10). The problem of tolerance of orthoses is paramount in children and even more in teenagers, especially since spinal trauma often occurs at the start of the hot season. Even in mildly unstable lesions, we forbid standing up with provisional orthoses, until the definitive, custommade orthosis is ready, so it is perceived as liberation.

Fig. 10 Ten-month baby, immobilized in a rigid brace with frontal strap, in addition to occipito-cervical fusion with nylon thread and autologous graft. This orthosis allows cradling, suckling, and diaper care.

Halo The halo is often viewed as more invasive than orthoses, and it require anesthesia, however, several patients who experienced both voiced their preference for the halo, because the jaw is free and the jacket is cooler than a brace. Whereas in adults, the general recommendations are 4 pins with a torque of 10 pound.feet (using the dynamometric screw-driver), in children, constraints should be more shared over the crown; generally, the smaller the child, the higher the number of pins (6 to 8), and the smaller the torque (4 to 2 pound.feet). In small infants, the pins can be tightened with bare fingers in order to avoid penetrating the thin skull cap. Halos pose technical challenges in very small infants, like the length of the screws and the growth of the head circumference during treatment. Like orthoses, halos require education of the patient and his parents and periodical control of the wounds.

Traumatic Spine injury in Childhood

1323

Surgery The surgical indications for spinal trauma are generally considered more restricted in children than in adults, however, with the introduction of new techniques, surgery is proving more and more useful for children. In two studies published in1988 and 2000 respectively, the Phoenix team showed that indications had risen from 16% to 30% of children [5, 10]. The latter figure is in keeping with our own experience (31.6%). The indications are: highly unstable lesions, irreducible dislocation, progressing deficit [5], penetrating wounds, post-traumatic deformations and meningoceles [18]. The decision to operate or treat with orthosis only is based on the age of the patient, level and type of the fracture, and a number of other considerations, so that no general rule can be drawn; only arguments in favor of one treatment or the other can be listed (table 2). Laminectomy should be avoided in children because of the risk of progressive deformation with growth; for arthrodesis, laminar hooks are more often used than pedicular screws, making preservation of the posterior arches all the more important. Laminar hooks minimize the risk of neural damage, and have the advantage of taking hold on the most compact part of the vertebra and the one which is most resilient to compression. Pedicular screws can be used mostly in the lumbar and lower thoracic spine in adolescents; other levels and age groups generally require laminar hooks. Screws and hooks can be combined, especially in thoraco-lumbar fractures; the lower levels, in lordosis, are a good site for screws, whereas the upper levels, in kyphosis and with smaller pedicles, are more easily managed with hook clamps, which also have the advantage of averting pull-out. As already mentioned, thoraco-lumbar fractures are often not limited to one level, even when the CT scans shows only one fractured vertebra, long arthrodesis (two levels above, two levels below the fracture) should therefore be Table 2 Decision-making in pediatric spinal trauma. Because the decision depends on many factors, among which the level of the lesion, its type, the patient's age, the surgeon's own experience, the material he can rely on, and the follow-up which is available, each case should be discussed and treated individually as a separate disease. We listed in this table the factors which are in favor of orthotic, or surgical (plus orthotic) treatment.

ORTHOTIC TREATMENT ONLY

SURGERY + ORTHOSIS

No neurological signs

Spinal cord compression open wound

No deformity

Severe deformity/luxation

Young age

Near-adult

Wedge fracture

Highly mobile fracture

Multiple levels

Single, highly mobile level

Thoracic level (rib cage)

Thoraco-lumbar, cervical

Awake and standing

Comatose

Pure spinal trauma

Polytrauma

1324 Pediatric Neurosurgery preferred. Anterior fusion is preferred in subaxial cervical lesions in adolescents. For the thoracic and lumbar spine, anterior approach is generally used in addition to posterior arthrodesis. Ancillary arthrodesis is not a definitive solution and bone grafting is necessary, especially in case of disruption of the ligaments and discs. Since posterior arches are not available for graft material, the operative site should be prepared for graft harvesting. Autologous bone graft is always available, mostly from the iliac crest, but help from an orthopedic colleague may be required for the fibula, or from a general surgeon for ribs; in craniocervical fusion, the occipital squamma can be harvested and split. The screws, hooks and rods are left in place definitively, in order to avoid additional damage to the spinal muscles, unless the material fails, and/or the patient has pain complaints. The field of spinal surgery evolves fast, and many new techniques will be tested in the future. The concept of percutaneous pedicular screw arthrodesis (Sextant ®), avoiding muscular and periosteal damage, appears appealing for adolescents. However the lesions which benefit most from this technique in adults (wedge fractures without compromise of the spinal canal) are better indications for orthopedic treatment in children. Pedicular screws have also been proposed for children with isthmic fracture of C2, for C1-C2 fusion, even C0-C1 fusion [3]; these techniques have limitations due to the small size of the pedicles, and we think these require a large experience on adult patients before being applied to children. Image-guided placement of pedicular screws under fluoronavigation may be a solution for such techniques [2]. Topical use of bone morphogenic protein (BMP) has been proposed to promote bone formation in addition to arthrodesis [19, 24]; effective control of the efficacy of this technique, and avoidance of creeping osteogenesis, will be a crucial factor, and its superiority over traditional bone grafting will need to be confirmed.

Outcome The overall mortality of spinal trauma is high, mostly related to the violence of the trauma and associated lesions, but also to neurological deficits when the lesion is high [1]. The mortality rate has been evaluated at 10% for lower cervical spine lesions, versus 20% for upper cervical spine lesions, death being generally caused by the associated brain lesions [5]. Neurological outcome depends on whether the deficit is complete or partial: in case of subtotal deficit, 83% of patients experience complete recovery [5]. The general neurological outcome is generally better than for adults, with a Frankel score improving postoperatively by two grades in 8 cases, of one grade in 26 cases and being unchanged in 38 [10]. The orthopedic outcome is an important element of prognosis; the static and growth of the spine can be compromised, even by benign trauma. Growth is generally stumped at the level of the fracture; after surgery, all the levels at which the periosteum has been elevated eventually fuse ("creeping fusion") [9]. Partial fusion may result in the "crankshaft effect", which is asymmetric growth with progressive deformity due to continued growth from the unfused synchondroses. Post-traumatic syringomyelia is exceptional in children [10], but meningeal cysts and thoracic CSF fistulas may also develop.

Traumatic Spine injury in Childhood

1325

In a nutshell The child with spinal trauma should be viewed in a holistic approach, that is, in his four dimensions (growth is an essential feature), in his complexity (no treatment can be efficient against his will) and in his environment (family and school). The lesions are varied and complex, and modern imaging can depict precisely the anatomical damage. Each type of fracture at each anatomical level, in each age group represents a distinct disease, making therapeutic decision difficult. The management of pediatric spine trauma requires basic knowledge on the development, anatomy, and biomechanics of the pediatric spine, as well as mastering a large scope of surgical and non-surgical techniques. The constant advance of spinal surgical techniques is a boon for the patients, but also a challenge for pediatric neurosurgeons. Close collaboration between pediatric and spine neurosurgeons, and with physical therapists is mandatory to provide adequate and up-to-date treatment to these patients.

REFERENCES 1. Adelson PD, Resnick DK: Spinal cord injury in children. In: Albright AL, Pollack IF, Adelson PD (Eds): Principles and practice of pediatric neurosurgery. 1999 New York, Thieme pp. 955-969 2. Assaker R, Reyns N, Vinchon M, Demondion X, Louis E (2001) Transpedicular screw placement: image-guided versus lateral-view fluoroscopy: in vitro simulation. Spine 26: 2160-2164 3. Brockmeyer DL: Advanced pediatric craniocervical surgery. 2006, New York, Thieme 4. Consensus group on cervical spinal trauma (2002) Management of pediatric cervical spine and spinal cord injuries. Neurosurgery 50 (Suppl) 85-99 5. Eleraky MA, Theodore N, Adams M, Rekate H, Sonntag VKH (2000) Pediatric cervical spine injuries: report of 102 cases and review of the literature. J Neurosurg (Spine) 92 (suppl 1): 12-17 6. Feldman KW, Weinberger E, Milstein JM, Fligner CL (1997) Cervical spine MRI in abused infants. Child abuse Neglect 21: 199-205 7. Gabos PG, Tutten HR, Leet A, Stanton RP (1998) Isolated spinal cord injury as a presentation of child abuse. Pediatrics 101: 473-477 8. Gille P, Bonneville JF, François JY, Aubert D, Canal JP (1980) Fracture des pédicules de l'axis chez un nourrisson battu [Fractures of axis pedicles in battered infant]. Chir Pédiatr 21: 343-344 9. Grabb PA, Hadley MN: Spinal column trauma in children. In: Albright AL, Pollack IF, Adelson PD (eds) Principles and practice of pediatric neurosurgery. 1999, New York, Thieme pp.935-953 10. Hadley MN, Zabramski JM, Browner CM, Rekate H, Sonntag VKH (1988) Pediatric spinal trauma: review of 122 cases of spinal cord and vertebral column injuries. J Neurosurg 68: 18-24 11. Harpold TL, McComb JG, Levy ML (1998) Neonatal neurosurgical trauma. Neurosurg Clin North Am, 9:141-154 12. Johnson DL, Boal D, Baule R (1995) Role of apnea in nonacccidental head injury. Pediatr Neurosurg 23: 305-310 13. Kleinman PK, Shelton YA (1997) Hangman's fracture in an abused infant: imaging features. Pediatr Radiol 27: 776-777 14. Kobayashi S, Kanda K, Yokoshi K, Ohki S (2006) A case of spinal cord Injury that

1326 Pediatric Neurosurgery occurred in utero. Pediatr Neurol 35: 367-369 15. Lebwohl NH, Eismont FJ: Cervical spine injuries in children. In: Weinstein SL (ed): The pediatric spine. 1994, New York, Raven pp.725-741 16. Levene MI: Disorders of the spinal cord and cranial and peripheral nerves. In: Levene MI, Lilford RJ, Bennett MJ, Punt J (eds): Fetal and neonatal neurology and neurosurgery, second edition. 1995, Edinburgh, Churchill Livingstone pp. 613-621 17. Morandi X, Riffaud L, Amlashi SFA, Brassier G (1994) Extensive spinal cord infarction after posterior fossa surgery in the sitting position: case report. Neurosurgery, 54: 1512-1516 18. Naso WB, Cure J, Cuddy BG (1997) Retropharyngeal pseudomeningocele after atlantoaxial dislocation: report of two cases. Neurosurgery 40: 1288-1291 19. Oluigbo CO, Gan YC, Sgouros S, Chapman S, Kay A, Solanki G, Walsh AR, Hockley A (2008) Pattern, management and outcome of cervical spine injuries associated with head injuries in paediatric patients. Child's Nerv Syst 24: 87-92 20. Pang D: Spinal cord injuries. In: McLone DG (ed): Pediatric neurosurgery, 4th Ed, 2001, Philadelphia, Saunders, pp. 660-694 21. Piatt JH, Steinberg M (1995) Isolated spinal cord injury as a presentation of child abuse. Pediatrics 96: 780-782 22. Rekate H, Theodore N, Sonntag VKH, Dickman CA (1999) Pediatric spine and spinal cord trauma: state of the art for the third millennium. Child's Nerv Syst, 15: 743-750 23. Renshaw TSJ: Spinal cord injury and posttraumatic deformities. In: Weinstein SL (ed): The pediatric spine. 1994, New York, Raven, pp. 767-780 24. Robinson Y, Heyde CE, Tschöke SK, Mont MA, Seyler TM, Ulrich SD (2008) Evidence supporting the use of bone morphogenetic proteins for spinal fusion surgery. Expert Rev Med Devices, 5: 75-84 25. Rooks V, Sisler C, Burton B (1998) Cervical spine injury in child abuse: report of two cases. Pediatr Radiol, 28: 193-195 26. Ruge JR, Sinson GP, McLone DG, Cerullo LJ (1988) Pediatric spinal injury: the very young. J Neurosurg 68: 25-30 27. Vialle R, Piétin-Vialle C, Vinchon M, Dauger S, Ilharreborde B, Glorion C (2007) Birth-related spinal cord injuries: a multicentric review of nine cases. Child's Nerv Syst 24: 79-85 28. Vinchon M, Defoort-Dhellemmes S, Desurmont M, Dhellemmes P (2005) Accidental and non-accidental head injuries in infants: a prospective study. J Neurosurg Pediatr 102 (suppl 4): 380-384 29. Zwimpfer TJ, Bernstein M (1990) Spinal cord concussion. J Neurosurg, 72: 894-900

1327

The Craniovertebral Junction in Children: Normal Development and Management of Developmental Anomalies SHOBHAN VACHHRAJANI, MD and JAMES T. RUTKA, MD, PhD, FRCSC Division of Neurosurgery, Hospital for Sick Children Toronto, Ontario, Canada Key words: craniovertebral junction, atlanto-axial instability, os odontoideum, craniovertebral fixation

Introduction The craniocervical junction, interchangeably referred to by many as the craniovertebral junction (CVJ), represents the transition point between the cranium and the spine, and consequently the brain and the spinal cord. It is a complex anatomical structure comprising the distal third of the clivus, the occipital bone, atlas (C1), axis (C2), and the occipital bone.1 It is also the most mobile segment of the upper cervical spine, and the unique bony structure, their numerous articulations, and the complicated nature of ligamentous attachments serve to promote maximal mobility while protecting the neurovascular structures that are present nearby.2 Its development occurs in a wellcoordinated fashion however it is this complexity that renders the CVJ susceptible to a variety of developmental anomalies, both osseous and ligamentous. Some of these can render the upper cervical spine unstable, and neurosurgeons must be well versed in these conditions in order to adequately assess and manage these patients. This chapter focuses on developmental anomalies of the CVJ and modern management strategies for these conditions. It is impossible, however, to fully appreciate their anatomical, clinical, and treatment nuances without a detailed understanding of normal embryological development. This chapter begins with a discussion of the embryology of the CVJ, followed by selected developmental anomalies and their clinical presentation. It will conclude with an overview of non-surgical and surgical techniques for the management of these conditions.

Normal Development of the CVJ Early Embryological Precursors The development of the CVJ is exceedingly complex and is tied closely to the process of neurulation. By the third week of gestation, a trilaminar embryo has formed that consists of ectodermal, mesodermal, and endodermal layers. The notochord, the formation of which is induced by noggin, chordin, and follistatin proteins, promotes thickening of the ectoderm into the neural plate.3 These cells subsequently form the

1328 Pediatric Neurosurgery neuroectoderm and their further differentiation comprises the process of neurulation. Cells of the neural plate begin to migrate towards the primitive streak, and the lateral edges of the neural plate become progressively elevated to form the neural folds. These folds eventually fuse in the midline, initially at the level of the future neck, and further fusion proceeds both cranially and caudally from there. This fusion forms the neural tube, however both cranial and caudal ends of this structure remain open. These cranial and caudal neuropores ultimately close at day 25 and 27 of gestation respectively, and this closure completes the process of neurulation. (Figure 1) In parallel to this process, proliferation and differentiation of the mesodermal layers occur. By day 17 of gestation, mesodermal cells near the midline coalesce to form paraxial mesoderm that surrounds the notochord. By the beginning of the third week, this paraxial mesoderm has become organized into segments called somitomeres. Their formation proceeds in a craniocaudal direction starting at the occipital region. Further organization of these units results in the formation of somites. The first somite appears at approximately day 20, and further somites form at roughly 3 pairs per day until the end of the 5th gestational week, at which point 42 pairs of somites are present. These are divided into 4 occipital, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 8-10 sacrococcygeal pairs.4 By the beginning of the 4th week, these somites further differentiate into sclerotomes, myotomes, and dermatomes. The sclerotomes are ultimately responsible for cartilage and skeletal development. Somite differentiation is induced by expression of the Sonic hedgehog (Shh) gene pathway, and expression of PAX1 transcription factor from sclerotomal cells is responsible for inducing cartilage and bone formation.3 Excluding the

Fig. 1 Formation of the neural tube occurs through a process called neurulation. The ectodermal layer of the trilaminar embryo is responsible for this process, and the neural tube is closely associated with formation of the axial skeleton. Figure used with permission from Nature Publishing Group (Nature Reviews Neuroscience 2003; 4: 795-805).

The Craniovertebral Junction in Children: Normal Development and Management of Developmental Anomalies

1329

CVJ, the cranial half of each sclerotome fuses with the caudal half of the one above to form the vertebral body. Cells from the fissure of Ebner that demarcate the cranial and caudal halves proceed to form the precursors of the intervertebral disc. Craniocaudal differentiation, or axial patterning of the somites, is controlled by the Homeobox (Hox) group of genes.5

Formation of the CVJ The precursor of the skull, the neurocranium, is divided into membranous and cartilaginous parts. This latter part, also known as chondrocranium, is responsible for formation of the skull base. This occurs by fusion and subsequent endochondral ossification of the prechordal and chordal chondrocranium which lie anterior and posterior to the cranial limits of the notochord respectively. The base of the occipital bone, or basiocciput, is formed by the parachordal cartilage and the first 2 occipital sclerotomes. The 3rd sclerotome forms the exoccipital base which ultimately develops into the jugular tubercles. The 4th occipital sclerotome is key to the development of the CVJ. Also known as the proatlas, it consists of 3 parts: the hypocentrum, centrum, and neural arch. Each part contributes to portions of the occiput, atlas, and axis. The hypocentrum forms the anterior tubercle of the clivus, while the centrum forms the apex of the dens and the apical ligament. Division of the neural arch creates rostral and caudal segments. The former becomes the anterior margin of the foramen magnum and the ipsilateral occipital condyle. The caudal division differentiates into the lateral masses of the atlas and the superior portion of the posterior arch of C1. The most lateral portions of the proatlas condense into the cruciate and alar ligaments.4 The axis originates from the 1st and 2nd spinal sclerotomes. The centrum of the 1st sclerotome separates to fuse with the body of the axis and creates the odontoid process. The posterior and inferior portions the atlantal arch are formed from the neural arch portion of this sclerotome. Its hypocentrum goes on to form the anterior arch of the atlas. Axis development is further contributed by the 2nd spinal sclerotome. Its hypocentrum disappears, while the centrum forms the body of the axis. The neural arch of the 2nd spinal sclerotome divides to form the facets and the posterior arch of the axis. (Table 1) This multiplicity of origins of both the atlas and axis yield a group of ossification centres for each of these levels. The atlas forms from 3 ossification centres consisting of the body and 2 neural arches. The body, also known as the anterior arch, becomes visible as an ossification centre by approximately 1 year of age. The neural arches appear in the 7th gestational week and fuse with the anterior arch by 7 years of age. Posterior fusion of the neural arches occurs by approximately 3 years of age. Non-fusion of these synchondroses is often mistaken by unfamiliar clinicians for fractures. By contrast, the ossification pattern of the axis is much more complex. There are 4 primary ossification centres consisting of the odontoid process, body, and 2 neural arches. The odontoid process forms in utero from the midline fusion of 2 ossification centres that fuse by the 7th month of gestation. A secondary ossification centre, the os terminale, appears at the apex of the odontoid process between 3-6 years of age and fuses with the odontoid process by age 12.6, 7 The body of C2 forms from a single ossification centre appearing by

1330 Pediatric Neurosurgery Table 1 Embryological precursors of CVJ elements.4

the 5th month in utero. A cartilaginous band separates the odontoid process from the axis body; this is referred to as the neural central synchondrosis.4 This structure is important in understanding the pathogenesis of os odontoideum. Fusion occurs between 3-6 years of age, however this fusion line is often visible until age 8-11 years.4, 6 This fusion line will persist for life in up to 1/3rd of individuals. Finally, the neural arches of C2 appear by the 7th month of gestation. Posterior fusion of these occurs by 2-3 years of age, while fusion of the synchondrosis between the neural arches and the body and odontoid process takes place between ages 3-6 years.

Formed Anatomy of the CVJ The complex process of development described thus far results in an intricate osseoligamentous structure that provides physical support for the cranium on the rest of the erect axial skeleton, mobility of the head, and protection of neural conduits from the brain to peripheral and visceral body structures. A detailed discussion of the vascular anatomy of the CVJ is beyond the scope of this chapter. It is important, however, to understand the bony articulations and ligamentous support structures of the CVJ. The occipital bone forms the top of the CVJ and the foramen magnum is the most important part of this structure. There are 3 parts to this bone of which the condylar part is the most important with regards to the CVJ. As its name would suggest, it contains the occipital condyle which articulates on either side with the lateral masses of the atlas. This part also includes the hypoglossal canal and jugular foramen, both important structures to note in surgical approaches to this region. This condylar part also connects the squamosal portion of the occipital bone posteriorly to the clival portion anteriorly. The sagittal diameter of the foramen magnum is said to be 35 ± 4mm.2

The Craniovertebral Junction in Children: Normal Development and Management of Developmental Anomalies

1331

The atlas or C1 is unique in structure. It does not have a vertebral body nor a spinous process. Two thickened lateral masses, which receive the occipital condyles from above, sit at the anterolateral aspect of the C1 ring. A short anterior arch connects the lateral masses in the front, and the longer posterior arch in the back. The odontoid process of the axis sits where the vertebral body would be situated at other spinal levels. A groove for the vertebral artery is located at the base of the superior facet at its junction with the neural arch; the vertebral arch emanates from the transverse foramen at this level. The inferior aspects of the lateral masses are slightly convex in shape and articulate with the superior facets of the axis. The axis, also called the epistropheus, acts as the pivot for the atlas and head upon which to rotate. The odontoid process projects rostrally, and the oval shaped facet on its ventral surface articulates with the dorsal surface of the anterior atlantal arch. The transverse atlantal ligament passes dorsally over the dens. Thick primitive laminae are located posteriorly, and modern surgical fixation techniques take advantage of this anatomical feature. The spinous process of the axis is large and bifid. Motion and stability of this bony apparatus is provided by the intricate arrangements of the occipitoatlantoaxial ligaments. Little stability is provided by the occipitoatlantal joint and its lax capsule. Atlantoaxial ligaments strengthen the atlantoaxial joints and their surrounding capsules; there is contribution to this structure from the lateral fibres of the tectorial membrane. The transverse atlantal ligament, which anatomically is composed of the transverse fibres of the cruciate ligament, secures the dens in place against the anterior arch of the atlas, and is attached to specific tubercles on the inner aspect of the anterior atlantal arch. Accessory atlantoaxial ligaments further strengthen this structure. (Figure 2) The cruciate ligament connects the foramen magnum in the midline to the midpoint of the axis body; the apical ligament connects the tip of the odontoid process to the rim of the foramen magnum and runs ventrally and parallel to the vertical portion of the cruciate ligament. The alar ligament connects the lateral aspect of the foramen magnum to the dens. Finally, the tectorial membrane is a cephalad extension of the posterior longitudinal ligament and runs posteriorly to the transverse atlantal ligament. It attaches to the posterior aspect of the body of C3, the body of the axis, the dens, and then fans out to attach to the base of the occiput. The posterior atlanto-occipital

Fig. 2 Axial view of the atlas, odontoid process, and associated ligaments involved in preserving stability of the atlantoaxial complex. Figure used with permission from Springer (Child’s Nervous System 2008; 24: 1091-1100).

1332 Pediatric Neurosurgery

Fig. 3 Midsagittal view of the craniovertebral junction. The complex ligamentous arrangement is crucial in ensuring stability of the craniovertebral junction. Figure used with permission from Springer (Child’s Nervous System 2008; 24: 1091-1100).

membrane provides further support between the posterior arch of the atlas and the basal occiput. (Figure 3)

Normal Biomechanics of the CVJ The CVJ is referred to by many as the occipitoatlantoaxial complex and this structure is the most mobile part of the axial skeleton.2 The CVJ is thought to function as a single unit while the axis serves as a washer between the skull and the subaxial cervical spine. Several directions of movement are facilitated by its osseoligamentous structure. A quarter of the flexion and extension movement of the cervical spine is accounted for by the occipitoatlantal (O-C1) and atlantoaxial (C1-C2) joints. Approximately 15° of motion occurs at the O-C1 joint, and 10° is seen at the C1-C2 joint.8 Such motion results in anterioposterior translation of the odontoid process relative to the anterior arch of the atlas, and an excursion of up to 5mm is permissible in children up to 8 years of age, with 3mm of predental space normal in older children and adults. Competency of the cruciate ligament is essential in preserving this relationship, and clinically this is reflected in the measurement of the atlanto-dental interval (ADI). The neck can also be rotated up to 90° in each direction. No motion in this respect occurs at the O-C1 joint. Most believe that the C1-C2 joint can provide between 25-30° of rotation, and that the middle and lower levels of the cervical spine provide additional rotational distance beyond this.2 Others have suggested that up to 50° may be afforded by this joint.8 Differential tolerance between individuals becomes important when assessing patients with specific developmental anomalies. Finally, the O-C1 joint provides approximately 10° of range in lateral bending, whereas there is negligible motion at the C1-C2 joint in this regard.

The Craniovertebral Junction in Children: Normal Development and Management of Developmental Anomalies

1333

Ongoing ossification and ligamentous strengthening, the chronology of which has been previously discussed, clearly renders the pediatric cervical spine structurally and biomechanically different from the adult cervical spine. The spines of children 9 years of age and younger are thought to represent immature spines, and those between 12-14 years are thought to comprise the intermediate age group. The adult spine is believed to have formed by 14-16 years of age. This age dependent transition owes likely to the changing composition of the spine from the infantile version composed largely of elastic cartilages and connective tissue, to the bony and ligamentous structure in place by 8-9 years of age.2 Laxity of the ligaments still make the spine more mobile at this age compared to adults and this phenomenon, in addition to changes in body to head proportions, is responsible for changes in the spine’s fulcrum with age. In infants it rests at C2-3, migrates caudally to C3-4 by age 5-6 years, and finds itself at C5-6 by adolescence.2 Developmental anomalies and syndromic associations superimpose themselves on these age dependent phenomena and patient management must be individualized to account for this.

Developmental Anomalies of the CVJ Initial reports of CVJ anomalies date back over 50 years. In 1953, McRae was the first to publish on this group of problems and more importantly, described their association with neurologic sequelae.9 That series comprised 60 adult patients with a variety of CVJ anomalies, and patients presented with cranial nerve, long tract, and various motor and sensory deficits. Ten years after this initial report, Bharucha and Dastur reported a mixed series of 40 adult and pediatric patients with similar neurologic findings.10 Many CVJ anomalies are associated with skeletal dysplasias, genetic syndromes, and metabolic disorders, with many patients presenting with synchronous systemic abnormalities.11 This section discusses important CVJ anomalies, their origins, and management principles.

Proatlas Segmentation Failures As previously discussed, the 4th occipital sclerotome, or proatlas, comprises 3 distinct parts. Failure of separation into these components results in malformations that usually surround the foramen magnum and involve the posterior arch of C1.12-17 Should the hypocentrum and centrum not separate properly, the anterior arch of the atlas comes to sit above the body of the axis. Severe ventral distortion of the cervicomedullary canal can occur if this becomes fused with the clivus. Diagnosis is usually delayed with approximately 90% of patients presenting between 10-20 years of age although in a recent series reported by Menezes, patients presented as young as 3 years of age and as old as 23.4 Approximately 80% of patients presented with spastic quadriparesis and 1/3rd presented with palsies of cranial nerves 8-12. Much of this is likely due to associated hindbrain herniation.18 In 60% of cases, the diagnosis became apparent after presentation in a trauma setting. Three dimensional CT complemented by MRI scanning are the imaging modalities of choice as they allow for complete evaluation of bony structures as well as ligamentous and neural elements.

1334 Pediatric Neurosurgery

Atlas Assimilation Failure of segmentation between the proatlas and the first spinal sclerotome results in assimilation of the atlas into the basiocciput. (Figure 4) Classifications based on germ layers involved in the assimilation and based on regions of C1 involved have been proposed.19 In most cases, it is associated with Klippel-Feil syndrome, and the secondary basilar invagination with hindbrain herniation that occurs is only worsened by fusion of other subaxial spinal levels.4, 20, 21 (Figure 5) This constellation of bony abnormalities leads to atlantoaxial instability due to abnormal load shifting on to that level. Initially, the instability is reducible however with age, it progresses to a reducible basilar invagination that beyond 15 years of age becomes irreducible.22 Early in this process, granulation tissue develops at the odontoid apex in an attempt to naturally reduce the defect; this process tends only to worsen neural compression.4 The end result is a horizontally oriented clivus and abnormal grooving behind the occipital condyle that pushes the skull base upwards

Fig. 4 Sagittal CT scan reconstruction of the cervical spine in a patient with Goldenhar syndrome displaying assimilation of the atlas anteriorly.

a

b

Fig. 5 a) Sagittal CT scan reconstruction of the cervical spine in a patient with Klippel Feil Syndrome. Note the severe basilar invagination and fusion of the subaxial cervical spine. b) Sagittal T2 weighted MRI of the cervical spine in the same patient showing basilar invagination and an extensive associated syrinx.

The Craniovertebral Junction in Children: Normal Development and Management of Developmental Anomalies

1335

resulting in platybasia. This migration of the skull base coupled with the reduction in posterior fossa height subjects patients to a hindbrain herniation syndrome; consequent management strategies must be targeted towards decompression of hindbrain structures and a consideration of potential spinal instability. Unilateral atlas assimilation presents with torticollis, and care must be taken during any manipulation of the neck, particularly in those patients with Klippel-Feil syndrome due to the resulting abnormal biomechanics as previously described. A recent study in mice has elegantly shown that mutations in the gene for MEOX1, a protein that is responsible for sclerotomal differentiation and somite proliferation, lead to CVJ remodeling and specifically assimilation of the atlas into the basiocciput.23

Atlantal Arch Defects Developmental defects of the arch of C1 can be divided into those of the anterior arch and those of the posterior arch. The former are exceedingly rare with reported incidence of 0.1% in multiple radiographic and cadaveric studies.24-28 Posterior arch defects are slightly more common and are categorized into 5 groups according to a system developed by Currarino.29 Over 90% are type A (median cleft), where as types B-E (unilateral cleft, bilateral clefts with preservation of the most dorsal aspect of the arch, complete absence of the posterior arch with a preserved dorsal tubercle, and complete absence of the posterior arch respectively) have a reported incidence of 0.6-0.7% collectively.24 It is believed that such defects are due to failure of local chondrogenesis early in development rather than a failure of subsequent ossification.30 This theory is further supported by autopsy and intraoperative findings.31 Five modes of presentation have been described. Patients may be asymptomatic with their anomaly discovered on imaging for unrelated reasons (group 1), may present with neck pain after trauma (group 2), may develop sudden neurologic symptoms after head or neck trauma (group 3), may have various chronic neurologic symptoms prior to diagnosis (group 4), or have their diagnosis made when investigated for chronic neck pain (group 5).29 Most believe these arch defects to represent benign anatomical variants and present asymptomatically. Combined defects of the anterior and posterior arches are rare although have been reported.32 It is strongly believed that the atlas should form a ring by the age of 3 years. In some cases, incompletely formed anterior or posterior arches may act functionally like a complex Jefferson fracture and should this persist beyond 3 years of age then operative intervention is recommended prior to the onset of neurological symptoms.4 Three dimensional CT scan and MRI are the imaging modality of choice.

Odontoid Anomalies: Dens Aplasia/Hypoplasia Aplasia and hypoplasia of the dens lies on a spectrum such that a rudimentary hypoplastic dens may be present, or the dens may be entirely absent. Clinicians must be careful in making the diagnosis of a hypoplastic dens as several factors can lead to an erroneous diagnosis. First, a normal dens may appear hypoplastic in young children; second, an immature odontoid process may be recognized as hypoplastic as the dens may ossify distally for up to 9 years after the proximal parts; and third, an os odontoideum

1336 Pediatric Neurosurgery may be present but overlooked.33 Hypoplasia of the dens is also seen in patients with atlas assimilation and congenital fusions of the C2 and C3 vertebrae. In this group of patients, the axis body is abnormal and the cruciate ligament is incompetent contributing to atlantoaxial instability. Vascular compromise secondary to distortion of the vertebral artery can be seen in association with this complex.4

Os Odontoideum Ossiculum odontoideum was first described by Giacomini in 1886 and represents an anomaly in which the normal odontoid process is replaced by an ossicle that has smooth circumferential cortical margins with no osseous continuity with the body of the axis.34 (Figure 6) There remains debate as to the etiology of this entity. Authors who favour the post-traumatic theory of development suggest that an unrecognized fracture of the dens is followed by contraction of the alar ligaments and subsequent distraction the fracture fragment from its natural site. Consequent interruption of the blood supply leads to ossicle formation. Proponents of this theory cite the location of the ossicle, situated cranial to the axis body, and longitudinal radiographic studies in which imaging performed immediately after trauma is normal.4, 35-38 Those in support of the congenital theory of development cite the association of os odontoideum with other syndromes, cadaveric studies supporting osseous and ligamentous changes of congenital etiology, and twin studies corroborating this theory.39 Recent radiographic studies appear to favour a congenital cause due to the presence of dysplastic features in the atlantoaxial joint.40 Other literature seems to suggest that each postulated cause may be responsible for the development of os odontoideum in selected patients.39 Ultimately, the development of os odontoideum portends atlantoaxial instability through incompetence of the cruciate ligament. The biomechanics of this condition are unique to each patient based on bony, ossicle, and ligamentous anatomy and in the worst case scenario, can cause compression of the cervicomedullary junction. Children with atlantoaxial instability and an associated os odontoideum should undergo surgical stabilization.4

Fig. 6 Sagittal CT scan reconstruction of the cervical spine in a patient with Down syndrome. The os odontoideum is apparent.

The Craniovertebral Junction in Children: Normal Development and Management of Developmental Anomalies

1337

Syndromic Associations Recent advances in molecular biological techniques, aided by the Human Genome Project, have greatly contributed to our understanding of a number of syndromes that affect the CVJ. A review of 6000 pediatric cases assessed by Menezes over a 30 year period revealed several genetic syndromes that present with an element of CVJ anomaly.41 A list of common syndromes, their specific features, and genetic loci are listed in Table 2. The common end pathway of many of these syndromes is atlantoaxial instability that progresses to the point of requiring surgical fixation; in the case of Goldenhar and Klippel-Feil syndromes, segmentation failure and fusion of cervical vertebral levels alters mechanical loads on adjacent levels and leads to instability through this mechanism.41, 42 Numerous CVJ defects are seen in patients with the 22q11.2 deletion syndrome, and rare connective tissue disorders including the Shprintzen-Goldberg syndrome can manifest with neurologic compromise due to CVJ abnormalities.43, 44 Careful consideration to the many associated systemic malformations must be given to avoid complications during management. Special consideration should be given to Down syndrome, the most common chromosomal abnormality in humans. Its incidence is now 1 in 700 live births.45 The syndrome manifests itself in essentially every organ system, and ligamentous laxity is a hallmark of this condition. Spitzer et al first reported 9 cases of atlanto-occipital dislocation in the context of Down syndrome in 1961.46 It is now understood that 14-24% of patients with this syndrome suffer from atlantoaxial instability, although only 1% are thought to be symptomatic. Patients present in a variety of ways, including pain referable to the CVJ, torticollis, and with signs occurring secondary to neurological Table 2 Genetic syndromes associated with anomalies of the craniovertebral junction.41, 43

1338 Pediatric Neurosurgery compromise including upper respiratory infections, hyperreflexia, quadriparesis, gait ataxia, and peripheral limb atrophy. Numerous bony abnormalities are seen in this population including os odontoideum, which is believed to be of post-traumatic nature, bifid posterior and anterior arches of the atlas, assimilation of the atlas, hypoplasia of the occipital condyle, and ossiculum terminale.45, 47 The vast majority of these patients present with instability at the O-C1 joint, C1-C2 joint, or both. Surgical stabilization is recommended for Down syndrome patients who present with neurologic compromise. (Figure 7)

a

b

Fig. 7 a) Sagittal CT scan reconstruction of the cervical spine in a patient with severe ligamentous laxity in the setting of Down syndrome. The patient was myelopathic due to significant atlantoaxial subluxation. b) The patient underwent halo traction, reduction, and a posterior atlantoaxial fusion. Spinal alignment was restored and the patient experienced transient neurological relief. Subluxation recurred months later and the patient required

Management of CVJ Anomalies As previously mentioned, the CVJ functions as a unit that bridges the gap between the cranium and the axial skeleton, and supports the transmission of neural impulses from brain to spinal cord and beyond. Preservation of this support, or preservation of stability truly, is the premier consideration when managing patients with developmental CVJ anomalies. Initial definitions of spinal stability have been well established by White and Panjabi, who defined it as the ability of the supporting elements of the spine to resist physiological loads so as to prevent neurological injury, deformity, and pain.48 Checklists of spinal stability that they developed are widely used worldwide. Cleary many of the conditions outlined in this chapter lead to the development of varying degrees of CVJ instability. An appreciation of the nuances involved is paramount before embarking on any surgical fixation strategy. There are specific aspects of pediatric CVJ instability that that add a dimension of

The Craniovertebral Junction in Children: Normal Development and Management of Developmental Anomalies

1339

complexity to its management. Smaller and more fragile bony and ligamentous structures, all of which undergo age related changes, pose unique challenges to executing surgical approaches to this region. Anatomical aberrances inherent in the CVJ anomalies already described add to the difficulty, and the majority of data regarding equipment and techniques, complications, and outcomes have been reported from adult populations. There remains the unique pediatric problem of limiting growth potential after any surgical procedure, which counterintuitively one could consider a fortuitous complication of increased fusion rates in children.49 As such, patients must be carefully chosen for surgery upon the CVJ. In most cases, purely bony lesions will heal with reduction and realignment, however complicated bony lesions with any element of ligamentous disruption require an operative management approach. Menezes has devised a list of criteria that suggest the presence of CVJ instability in children. They comprise the following:50 1. Predental space or atlantodental interval (ADI) > 5mm in children less than 8 years old, or >3mm over the age of 8-10 years. 2. Lateral mass separation >6mm. This suggests cruciate ligament disruption. 3. Vertical translation of >2mm between clivus and odontoid process. 4. O-C1 joint space is easily visible on lateral radiographs of the cervical spine. 5. Abnormal relationship between the foramen magnum and spinal canal. 6. Abnormal motion dynamics at the CVJ. 7. Visualization of disrupted transverse atlantal ligament, alar ligaments, tectorial membrane, and consequent bony malalignment. Should instability be suspected and intervention contemplated, one should consider the following factors when making treatment decisions: first, reducibility of the bony lesion and the ability to restore normal bony alignment with relief of neural element compression; second, the direction and mechanics of neural compression; third, the presence of abnormal ossification centres and epiphyseal growth plates; fourth, the etiology of the pathology and the presence of any secondary neural abnormalities such as hindbrain herniation.50, 51 Above all else, the goal of treatment is to attain neural decompression with subsequent stabilization to maintain this decompression.

Non-Operative Approaches The difficulties in stabilizing the pediatric CVJ are readily apparent from the preceding discussion. These are intensified in the young infant who suffers from CVJ instability in the setting of a number of developmental syndromes including SED, Goldenhar syndrome, and osteogenesis imperfect as examples. In these cases, non-operative approaches are favoured following careful examination of the bony abnormalities on three dimensional CT scan. Use of a custom built orthosis, crafted to support the occipitocervical junction and changed periodically to accommodate growth, is the best option in this group of children.52-54 Serial radiographic examination is carried out to monitor bony development and neural element compromise. External immobilization can be gradually removed if sufficient bone growth has occurred; this usually takes place around 3-4 years of age. If bony instability is recognized due to lack of bony growth then surgical fusion is strongly advised beyond age 4 years. Basilar invagination

1340 Pediatric Neurosurgery may be present in skeletal diseases where the bone is constitutionally softened. Modified Minerva casting may prop up the skull sufficiently to prevent further compression; results of this treatment should be confirmed by MRI.50 In older children with atlantoaxial dislocation or basilar invagination, or in those who require reduction prior to surgical fixation, halo traction may be a useful adjunct. In cases of developmental anomaly, traction and external immobilization is usually insufficient due to accompanying ligamentous insufficiency. Surgical bony fixation is recommended in these cases. The use of a halo vest may provide additional post-operative immobilization, and a minimum of 3 months are recommended for atlantoaxial fusions and 5-6 months if the occiput is incorporated into the fusion construct. Inadequate immobilization may result in failure of fusion in up to 50% of cases.50

Operative Fixation Techniques It is well appreciated that after neural decompression either by ventral or dorsal means, the spine must be fixed to prevent recurrence of instability and neural compromise. Traditionally, fixation has been achieved through a combination of posterior wiring techniques and external immobilization. Gallie described a construct in which sublaminar wires were placed between C1 and C2 to hold in place a midline interlaminar bone graft.55 (Figure 8) Brooks modified this technique to include 2 interlaminar grafts placed on either side of the midline.56 (Figure 9) Magerl described transarticular screws placed across the C1-C2 joint followed by a midline bone graft and interspinous process wiring. 57 (Figure 10) As previously mentioned, external immobilization can result in significant failure of fusion and result in significant morbidity to patients.58, 59 Recent literature has proven beyond doubt that rigid internal fixation using screws and polyaxial rod techniques provides superior biomechanical stability and removes the need for external halo orthosis.60-65 There is also increasing evidence for safety in very young patients as demonstrated by both Anderson et al. and Jea et al.66, 67 CT morphometric analysis has allowed for improved patient selection and technical efficiency in choosing the most appropriate construct for surgical fusion.68, 69 Certainly this should help to

Fig. 8 Artist’s rendition of a Gallie fusion. Used with permission from Journal of Neurosurgery Publishing Group (Neurosurg Focus 2004; 16: 1).

The Craniovertebral Junction in Children: Normal Development and Management of Developmental Anomalies

1341

Fig. 9 Artist’s rendition of a Brooks fusion. Used with permission from Journal of Neurosurgery Publishing Group (Neurosurg Focus 2004; 16: 1).

a

b

Fig. 10 a) Sagittal illustration displaying the technique of transarticular screw placement. Retraction of the greater occipital nerve is often necessary in order to obtain the appropriate trajectory. Used with permission from Lippincott Williams and Wilkins (Journal of Spinal Disorders 1992; 5 (4): 464-475). b) Sagittal illustration displaying the trajectory of transarticular screw placement. Used with permission from Lippincott Williams and Wilkins (Journal of Spinal Disorders 1992; 5 (4): 464-475).

mitigate concerns about feasibility of placing instrumentation for fixation purposes. It should be noted that the long-term outcomes of surgical CVJ fusions in children remains to be seen. The choice of which instrumentation construct to use remains highly debated. Many authors have advocated the use of the C1-C2 transarticular screw, either in isolation or as an anchor for loop or rod constructs extending to the occiput. This tends to provide immediate stability in all planes and can be used in patients with hypoplastic or absent posterior atlantal arches.49 Fusion rates have been reported near 100%, with the vast majority of patients not being immobilized in a halo device post-operatively.58, 60 There is, however, a significant learning curve associated with this procedure and the risk of injury to the vertebral artery, quoted at 4% in most studies, has led many to pursue other means of atlantoaxial fixation.49

1342 Pediatric Neurosurgery

a

b

Fig. 11 a) Lateral view of Harms fusion construct. A polyaxial screw and rod system is used to provide atlantoaxial fixation. Note the proximity of the vertebral artery. Used with permission from Lippincott Williams and Wilkins (Spine 2001; 26 (22): 24672475). b) Anteroposterior view of Harms fusion construct. A polyaxial screw and rod system is used to provide atlantoaxial fixation. Note the proximity of the vertebral artery. Used with permission from Lippincott Williams and Wilkins (Spine 2001; 26 (22): 2467-2475).

Fig. 12 Schematic illustration of crossed laminar screw placement at C2. Its primary advantage is avoidance of injury to the vertebral artery.

Several techniques have now been described that incorporate the C1 lateral mass into the fusion construct. Atlantoaxial fusion is obtained by connecting these anchors placed into the C1 lateral masses with instrumentation placed into the pars interarticularis, pedicle, or laminae of C2. Goel and Laheri initially described C1 lateral mass fixation using screws placed through a plate.70, 71 Harms et al. later described an approach in which C1 lateral mass screws are connected to C2 pedicle screws using polyaxial rods.72 (Figure 11) Many have since modified this technique to incorporate C2 pars interarticularis screws. In 2004, Wright described the use of crossing translaminar screws at C2 in an attempt to reduce the risk of vertebral artery injury seen with transarticular screw and C2 pedicle and pars interarticularis fusion constructs.73 (Figure 12)

The Craniovertebral Junction in Children: Normal Development and Management of Developmental Anomalies

1343

Despite their initial descriptions in adults, these techniques have been extended to children with good technical and fusion results. Jea et al. described the use of C1 lateral mass screws in 4 children under 8 years of age; one of these suffered an asymptomatic vertebral artery injury as a result of screw misplacement.67 Fusion rates near 100% were reported by Anderson et al. for pediatric patients receiving Harms fusion constructs.74 Similar findings have been reported by other groups.75 Finally, Wright and Leonard extended their technique of C2 crossed laminar screw placement to 3 pediatric patients.76 They reported good postoperative stability and no technical complications. These results have been further confirmed by Chamoun et al. in a recent publication.77 The recent literature supports the use of rigid internal fixation constructs in children; the specific approach taken must be individualized to each patient. Extension of these constructs to the occiput to provide occipitocervical fusion can be achieved using a combination of rod-plate or rod-screw constructs attached to the atlantoaxial instrumentation.49 This can be performed without difficulty in children.

Conclusions The craniovertebral junction is a complex anatomical structure that serves multiple purposes: to provide stability and mobility of the head on the remainder of the axial skeleton, and to provide protection for the upper cervical spinal cord. Its development is intricate and consists of multiple coordinated steps between many structures. The basis of many developmental anomalies of the CVJ are now readily apparent, and advanced neuroimaging now permits accurate diagnosis and understanding of the resulting neural element compromise and biomechanics. Neurosurgeons must be familiar with the normal anatomy of the CVJ in children, its developmental anomalies, and subsequent operative and non-operative management techniques.

REFERENCES 1. Kotil K, Kalayci M, Bilge T. Management of cervicomedullary compression in patients with congenital and acquired osseous-ligamentous pathologies. J Clin Neurosci 2007;14(6):540-9. 2. Menezes AH, Traynelis VC. Anatomy and biomechanics of normal craniovertebral junction (a) and biomechanics of stabilization (b). Childs Nerv Syst 2008;24(10):1091100. 3. Sadler TW. Langman's Medical Embryology. 8th ed. Philadelphia, PA: Lippincott Williams and Wilkins; 2000. 4. Menezes AH. Craniocervical developmental anatomy and its implications. Childs Nerv Syst 2008;24(10):1109-22. 5. Wellik DM. Hox genes and vertebrate axial pattern. Curr Top Dev Biol 2009;88:257-78. 6. Fesmire FM, Luten RC. The pediatric cervical spine: developmental anatomy and clinical aspects. J Emerg Med 1989;7(2):133-42. 7. Lustrin ES, Karakas SP, Ortiz AO, et al. Pediatric cervical spine: normal anatomy, variants, and trauma. Radiographics 2003;23(3):539-60. 8. Wills BP, Dormans JP. Nontraumatic upper cervical spine instability in children. J Am Acad Orthop Surg 2006;14(4):233-45. 9. McRae DL, Barnum AS. Occipitalization of the atlas. The American journal of

1344 Pediatric Neurosurgery roentgenology, radium therapy, and nuclear medicine 1953;70(1):23-46. 10. Bharucha EP, Dastur HM. Craniovertebral Anomalies (a Report on 40 Cases). Brain 1964;87:469-80. 11. Hosalkar HS, Sankar WN, Wills BP, Goebel J, Dormans JP, Drummond DS. Congenital osseous anomalies of the upper cervical spine. J Bone Joint Surg Am 2008;90(2):337-48. 12. Ganguly DN, Roy KKS. A study on the craniovertebral junction in man. Anat Anz Bd 1964;114:433-52. 13. Gladstone RJ, Wakeley CPG. Variations of the occipito-atlantal joint in relation to the metameric structure of the craniovertebral region. J Anat 1924;59:195-216. 14. Kotil K, Kalayci M. Ventral cervicomedullary junction compression secondary to condylus occipitalis (median occipital condyle), a rare entity. J Spinal Disord Tech 2005;18(4):382-4. 15. Menezes AH. Embyrology, development, and classification of disorders of the craniovertebral junction. In: Dickman CA, Sonntag VKH, Spetzler RF, eds. Surgery of the craniovertebral junction. New York: Thieme Medical Publishers; 1998:3-12. 16. Rao PV. Median (third) occipital condyle. Clin Anat 2002;15(2):148-51. 17. Tominaga T, Takahashi T, Shimizu H, Yoshimoto T. Rotational vertebral artery occlusion from occipital bone anomaly: a rare cause of embolic stroke. Case report. J Neurosurg 2002;97(6):1456-9. 18. Menezes AH. Honored guest presentation: craniocervical developmental anatomy and its implications. Clinical neurosurgery 2005;52:53-64. 19. Gholve PA, Hosalkar HS, Ricchetti ET, Pollock AN, Dormans JP, Drummond DS. Occipitalization of the atlas in children. Morphologic classification, associations, and clinical relevance. J Bone Joint Surg Am 2007;89(3):571-8. 20. Kagawa M, Jinnai T, Matsumoto Y, et al. Chiari I malformation accompanied by assimilation of the atlas, Klippel-Feil syndrome, and syringomyelia: case report. Surg Neurol 2006;65(5):497-502; discussion 21. Komatsu Y, Shibata T, Yasuda S, Ono Y, Nose T. Atlas hypoplasia as a cause of high cervical myelopathy. Case report. J Neurosurg 1993;79(6):917-9. 22. Menezes AH. Primary craniovertebral anomalies and the hindbrain herniation syndrome (Chiari I): data base analysis. Pediatr Neurosurg 1995;23(5):260-9. 23. Skuntz S, Mankoo B, Nguyen MT, et al. Lack of the mesodermal homeodomain protein MEOX1 disrupts sclerotome polarity and leads to a remodeling of the cranio-cervical joints of the axial skeleton. Dev Biol 2009;332(2):383-95. 24. Senoglu M, Safavi-Abbasi S, Theodore N, Bambakidis NC, Crawford NR, Sonntag VK. The frequency and clinical significance of congenital defects of the posterior and anterior arch of the atlas. J Neurosurg Spine 2007;7(4):399-402. 25. Garg A, Gaikwad SB, Gupta V, Mishra NK, Kale SS, Singh J. Bipartite atlas with os odontoideum: case report. Spine (Phila Pa 1976) 2004;29(2):E35-8. 26. Hodak JA, Mamourian A, Dean BL. Radiologic evaluation of the craniovertebral junction. In: Dickman CA, Spetzler RF, Sonntag VKH, eds. Surgery of the Craniovertbral Junction. New York: Thieme Medical Publishers; 1998:81-102. 27. Martich V, Ben-Ami T, Yousefzadeh DK, Roizen NJ. Hypoplastic posterior arch of C1 in children with Down syndrome: a double jeopardy. Radiology 1992;183(1):125-8. 28. Torriani M, Lourenco JL. Agenesis of the posterior arch of the atlas. Revista do Hospital das Clinicas 2002;57(2):73-6. 29. Currarino G, Rollins N, Diehl JT. Congenital defects of the posterior arch of the atlas: a report of seven cases including an affected mother and son. AJNR Am J Neuroradiol 1994;15(2):249-54. 30. Logan WW, Stuard ID. Absent posterior arch of the atlas. The American journal of roentgenology, radium therapy, and nuclear medicine 1973;118(2):431-4.

The Craniovertebral Junction in Children: Normal Development and Management of Developmental Anomalies

1345

31. Klimo P, Jr., Blumenthal DT, Couldwell WT. Congenital partial aplasia of the posterior arch of the atlas causing myelopathy: case report and review of the literature. Spine (Phila Pa 1976) 2003;28(12):E224-8. 32. Hosalkar HS, Gerardi JA, Shaw BA. Combined asymptomatic congenital anterior and posterior deficiency of the atlas. Pediatr Radiol 2001;31(11):810-3. 33. Stevens JM, Chong WK, Barber C, Kendall BE, Crockard HA. A new appraisal of abnormalities of the odontoid process associated with atlanto-axial subluxation and neurological disability. Brain 1994;117 ( Pt 1):133-48. 34. Giacomini C. Sull' estisenza dell 'os odontoideum' nell' vomo. Gior Acad Med Torino 1886;49:24-8. 35. Fielding JW, Hensinger RN, Hawkins RJ. Os Odontoideum. J Bone Joint Surg Am 1980;62(3):376-83. 36. Ricciardi JE, Kaufer H, Louis DS. Acquired os odontoideum following acute ligament injury. Report of a case. J Bone Joint Surg Am 1976;58(3):410-2. 37. Schuler TC, Kurz L, Thompson DE, Zemenick G, Hensinger RN, Herkowitz HN. Natural history of os odontoideum. Journal of pediatric orthopedics 1991;11(2):222-5. 38. Stillwell WT, Fielding JW. Acquired os odontoideum. A case report. Clinical orthopaedics and related research 1978(135):71-3. 39. Sankar WN, Wills BP, Dormans JP, Drummond DS. Os odontoideum revisited: the case for a multifactorial etiology. Spine (Phila Pa 1976) 2006;31(9):979-84. 40. Fagan AB, Askin GN, Earwaker JW. The jigsaw sign. A reliable indicator of congenital aetiology in os odontoideum. Eur Spine J 2004;13(4):295-300. 41. Menezes AH, Vogel TW. Specific entities affecting the craniocervical region: syndromes affecting the craniocervical junction. Childs Nerv Syst 2008;24(10):1155-63. 42. Tsirikos AI, McMaster MJ. Goldenhar-associated conditions (hemifacial microsomia) and congenital deformities of the spine. Spine (Phila Pa 1976) 2006;31(13):E400-7. 43. Konen O, Armstrong D, Clarke H, Padfield N, Weksberg R, Blaser S. C1-2 vertebral anomalies in 22q11.2 microdeletion syndrome. Pediatr Radiol 2008;38(7):766-71. 44. Jodicke A, Hahn A, Berthold LD, Scharbrodt W, Boker DK. Dysplasia of C-1 and craniocervical instability in patients with Shprintzen-Goldberg syndrome. Case report and review of the literature. J Neurosurg 2006;105(3 Suppl):238-41. 45. Menezes AH. Specific entities affecting the craniocervical region: Down's syndrome. Childs Nerv Syst 2008;24(10):1165-8. 46. Spitzer R, Rainovitch JY, Wybar KC. A study of the abnormalities of the skull, teeth, and lenses in mongolism. Can Med Assoc J 1961;84:567-72. 47. Nader-Sepahi A, Casey AT, Hayward R, Crockard HA, Thompson D. Symptomatic atlantoaxial instability in Down syndrome. J Neurosurg 2005;103(3 Suppl):231-7. 48. White AW, Panjabi MM. Clinical biomechanics of the spine. Philadelphia, PA: Lippincott, Williams and Wilkins; 1990. 49. Ahmed R, Traynelis VC, Menezes AH. Fusions at the craniovertebral junction. Childs Nerv Syst 2008;24(10):1209-24. 50. Menezes AH. Decision making. Childs Nerv Syst 2008;24(10):1147-53. 51. White AA, 3rd, Panjabi MM. The clinical biomechanics of the occipitoatlantoaxial complex. Orthop Clin North Am 1978;9(4):867-78. 52. Hughes TB, Jr., Richman JD, Rothfus WE. Diagnosis of Os odontoideum using kinematic magnetic resonance imaging. A case report. Spine (Phila Pa 1976) 1999;24(7):715-8. 53. Pappas CT, Rekate HL. Role of magnetic resonance imaging and three-dimensional computerized tomography in craniovertebral junction anomalies. Pediatric neuroscience 1988;14(1):18-22. 54. Smoker WR, Keyes WD, Dunn VD, Menezes AH. MRI versus conventional radiologic

1346 Pediatric Neurosurgery

55. 56. 57. 58. 59. 60. 61. 62.

63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73.

examinations in the evaluation of the craniovertebral and cervicomedullary junction. Radiographics 1986;6(6):953-94. Gallie WE. Fractures and dislocations of the cervical spine. Am J Surg 1939;46:495-9. Brooks AL, Jenkins EB. Atlanto-axial arthrodesis by the wedge compression method. J Bone Joint Surg Am 1978;60(3):279-84. Jeanneret B, Magerl F. Primary posterior fusion C1/2 in odontoid fractures: indications, technique, and results of transarticular screw fixation. Journal of spinal disorders 1992;5(4):464-75. Lowry DW, Pollack IF, Clyde B, Albright AL, Adelson PD. Upper cervical spine fusion in the pediatric population. J Neurosurg 1997;87(5):671-6. Tashjian RZ, Majercik S, Biffl WL, Palumbo MA, Cioffi WG. Halo-vest immobilization increases early morbidity and mortality in elderly odontoid fractures. The Journal of trauma 2006;60(1):199-203. Gluf WM, Brockmeyer DL. Atlantoaxial transarticular screw fixation: a review of surgical indications, fusion rate, complications, and lessons learned in 67 pediatric patients. J Neurosurg Spine 2005;2(2):164-9. Gluf WM, Schmidt MH, Apfelbaum RI. Atlantoaxial transarticular screw fixation: a review of surgical indications, fusion rate, complications, and lessons learned in 191 adult patients. J Neurosurg Spine 2005;2(2):155-63. Kuroki H, Rengachary SS, Goel VK, Holekamp SA, Pitkanen V, Ebraheim NA. Biomechanical comparison of two stabilization techniques of the atlantoaxial joints: transarticular screw fixation versus screw and rod fixation. Neurosurgery 2005;56(1 Suppl):151-9; discussion -9. Lapsiwala SB, Anderson PA, Oza A, Resnick DK. Biomechanical comparison of four C1 to C2 rigid fixative techniques: anterior transarticular, posterior transarticular, C1 to C2 pedicle, and C1 to C2 intralaminar screws. Neurosurgery 2006;58(3):516-21; discussion -21. Melcher RP, Puttlitz CM, Kleinstueck FS, Lotz JC, Harms J, Bradford DS. Biomechanical testing of posterior atlantoaxial fixation techniques. Spine (Phila Pa 1976) 2002;27(22):2435-40. Nichols LA, Mukherjee DP, Ogden AL, Sadasivan KK, Albright JA. A biomechanical study of unilateral posterior atlantoaxial transarticular screw fixation. Journal of longterm effects of medical implants 2005;15(1):33-8. Anderson RC, Kan P, Gluf WM, Brockmeyer DL. Long-term maintenance of cervical alignment after occipitocervical and atlantoaxial screw fixation in young children. J Neurosurg 2006;105(1 Suppl):55-61. Jea A, Taylor MD, Dirks PB, Kulkarni AV, Rutka JT, Drake JM. Incorporation of C-1 lateral mass screws in occipitocervical and atlantoaxial fusions for children 8 years of age or younger. Technical note. J Neurosurg 2007;107(2 Suppl):178-83. Chamoun RB, Whitehead WE, Curry DJ, Luerssen TG, Jea A. Computed tomography morphometric analysis for C-1 lateral mass screw placement in children. Clinical article. J Neurosurg Pediatr 2009;3(1):20-3. Chern JJ, Chamoun RB, Whitehead WE, Curry DJ, Luerssen TG, Jea A. Computed tomography morphometric analysis for axial and subaxial translaminar screw placement in the pediatric cervical spine. J Neurosurg Pediatr 2009;3(2):121-8. Goel A, Desai KI, Muzumdar DP. Atlantoaxial fixation using plate and screw method: a report of 160 treated patients. Neurosurgery 2002;51(6):1351-6; discussion 6-7. Goel A, Laheri V. Plate and screw fixation for atlanto-axial subluxation. Acta neurochirurgica 1994;129(1-2):47-53. Harms J, Melcher RP. Posterior C1-C2 fusion with polyaxial screw and rod fixation. Spine (Phila Pa 1976) 2001;26(22):2467-71. Wright NM. Posterior C2 fixation using bilateral, crossing C2 laminar screws: case

The Craniovertebral Junction in Children: Normal Development and Management of Developmental Anomalies

1347

series and technical note. J Spinal Disord Tech 2004;17(2):158-62. 74. Anderson RC, Ragel BT, Mocco J, Bohman LE, Brockmeyer DL. Selection of a rigid internal fixation construct for stabilization at the craniovertebral junction in pediatric patients. J Neurosurg 2007;107(1 Suppl):36-42. 75. Haque A, Price AV, Sklar FH, Swift DM, Weprin BE, Sacco DJ. Screw fixation of the upper cervical spine in the pediatric population. Clinical article. J Neurosurg Pediatr 2009;3(6):529-33. 76. Leonard JR, Wright NM. Pediatric atlantoaxial fixation with bilateral, crossing C-2 translaminar screws. Technical note. J Neurosurg 2006;104(1 Suppl):59-63. 77. Chamoun RB, Relyea KM, Johnson KK, et al. Use of axial and subaxial translaminar screw fixation in the management of upper cervical spinal instability in a series of 7 children. Neurosurgery 2009;64(4):734-9; discussion 9.

Ⅹ. Parasitosis and infections

1350

Brain Abscess ÁPIO CLÁUDIO MARTINS ANTUNES, M.D., Ph. D1 ANDRÉ CERUTTI FRANCISCATTO, M.D.2 RAFAEL MODKOVSKI, M.D.2 THIAGO TORRES DE ÁVILA, M.D.2 1

Head of Neurosurgical Unit, Hospital de Clinicas de Porto Alegre Professor of Neurosurgery, Porto Alegre Medical School Rio Grande do Sul Federal University. 2 Resident of Neurosurgery, Hospital de Clínicas de Porto Alegre. Key words: brain, abscess, infection, pyogenic, bacterial, sinuitis, otitis

INTRODUCTION By definition, brain abscess is a focal suppurative infection within the brain parenchyma. The infection results from invasion of the parenchyma by infectious microorganisms as the result of hematogenous spread from remote sources, direct invasion from contiguous infection, or from implantation of pathogens following penetrating wounds or surgery. (32) The first successful operation for the treatment of a brain abscess, other than surgical treatment reported from the Hippocratic era (460–377 BC), is said to have been performed in 1752, when the French surgeon S. F. Morand (4) operated on a temporoethmoidal abscess. In 1893, Sir William Macewen reported the surgical treatment of 19 patients (4). Aspiration was introduced by Dandy (9) in 1926. Vincent (35) demonstrated the efficacy of complete excision in 1936. In 1971, Heineman and colleagues (20) were the first to report the successful medical management of a brain abscess. The routine use of CT scanning has facilitated the diagnosis and follow-up of the patients with brain abscess. Despite modern surgical techniques, imaging technology and medical therapies, brain abscess remains a potentially fatal central nervous system infection (28)

EPIDEMIOLOGY In the United States, approximately 1500–2500 cases per year are reported, with a higher incidence in developing countries. (16) Brain abscesses represent 1–2% of all intracranial space-occupying lesions in the developed countries (14), but this percentage rises to 8% in developing countries (14). The reported male/ female ratio ranges from 1.3:1 to 5.0:1 (6, 33). The increased incidence of intracranial abscesses in the developed world can be attributed to the exponentially increasing number of immunocompromised patients

Brain Abscess

1351

(AIDS, cancer chemotherapy, immunosuppressive therapy). Brain abscesses in children are rare: when present in the pediatric population, they are most often seen in children between 4 and 7 years-old (22). At the University of Virginia Children’s Hospital, in the 2000-2007 period, an incidence of 1.5 children per year with brain abscess was reported (16).

ETIOLOGY Cerebral abscess commonly occurs in patients with the following predisposing states: 1) contiguous purulent spread (for example, frontal sinus infection leading to frontal lobe abscess, sphenoid sinus infection leading to cavernous sinus extension, and middle ear/mastoid air cell infection leading to temporal lobe and cerebellar abscess) 2) hematogenous or metastatic spread (for example, pulmonary infections and arteriovenous shunts, congenital heart disease and endocarditis, dental infections, and gastrointestinal infections) 3) head injury 4) neurosurgical procedure and 5) immunosuppression. (Table 1) The annual risk of a patient with chronic otitis media to develop a brain abscess is about 1 in 10,000. The likely mechanism is the occurrence of retrograde phlebitis from petrous bone, via superior or inferior petrosal sinus, causing abscess formation in the temporal or cerebellar region. Frontal sinusitis may be complicated by epidural or subdural empyema or frontal lobe abscess. In children and adolescents, it may follow acute sinusitis, whereas in adults usually follows chronic ones. The peak incidence occurs in late childhood and young adults, and it results from the venous spread of bacteria through the anterior sagital sinus or direct extension as result of osteomyelitis of the posterior sinus wall. Meningitis that is not due to a contiguous infection rarely leads to a brain abscess, except in infants and neonates. The most common organisms that cause brain abscess are typically bacterial in origin. Peptostreptococcus and Streptococcus spp (especially S. viridans and microaerophilic organisms) are mostly identified in patients with cardiac disorders (cyanotic heart disease and right-to-left shunt bypasses that exclude the normal filtration mechanisms of the pulmonary vascular tree). Bacteroides, Peptostreptococcus, and Streptococcus spp are most commonly identified in brain abscesses caused by contiguous spread. Streptococcus, S. aureus, Pseudomonas, and Bacteroides spp are mostly identified in pulmonary infections (pulmonary abscess, empyema, and bronchiectasis). They are located mostly in the middle cerebral artery (MCA) distribution and present often a multiple lesions pattern. Staphylococcus, Streptococcus, Clostridium, and Enterobacter spp are mostly identified in patients with open head trauma. Staphylococcus and Streptococcus spp should be considered in patients with prior neurosurgical procedures. Fungal infections, Toxoplasma, Staphylococcus, Streptococcus, and Pseudomonas spp are identified in immunocompromised patients with HIV infections, organ transplantation, chemotherapy, or steroid use (38). Atypical bacteria such as Nocardia and Actinomyces spp may occur in immunocompromised patients. Careful culturing of abscess material obtained at the time of surgery certainly is the best effort to make a microbiological diagnosis. Although positive culture rates have

1352 Parasitosis and infections approached 100% in studies with meticulous handling of clinical specimens (28), the incidence of negative cultures remains as high as 15–30% in most series (8).

PATHOGENESIS Brain abscesses develop in response to a parenchymal infection with pyogenic bacteria, which begins as a localized area of cerebritis and evolves into a suppurative lesion surrounded by a well-vascularized fibrotic capsule. The early stage or early cerebritis occurs from Days 1 to 3 and is typified by neutrophil accumulation, tissue necrosis, and edema (figure 1). Microglial and astrocyte activation is also evident at this stage and persists throughout abscess development. The intermediate, or late cerebritis stage, occurs from Days 4 to 9 and is associated with a predominant macrophage and lymphocyte infiltrate (figure 2). The final or capsule stage occurs from Day 10 onward and is associated with the formation of a well-vascularized

Fig. 1 Autopsy specimen of early abscess (Cerebritis) characterized by a poorly localized area of discoloration and softening.(By courtesy of Professor Ligia Coutinho)

Fig. 2 Autopsy specimen of late cerebritic / early abscess stage characterized by increasing central necrosis and beginning of encapsulation. (By courtesy of Professor Ligia Coutinho)

Brain Abscess

1353

abscess wall, sequestering the lesion and protecting the surrounding normal brain parenchyma from additional damage (figure 3). Early capsule formation develops from Days 10 to 13 and tends to be thinner on the medial or ventricular side of the abscess and prone to rupture in this direction. After Day 14, late capsule formation develops, with gliotic, collagenous, and granulation layers. (3)(figure 4).

Fig. 3 Autopsy specimen of mature abscess (Late stage) characterized by dense fibro-gliotic capsular wall and purulent center. (By courtesy of Professor Ligia Coutinho)

Fig. 4 Abscess wall – inner portion formed by a layer of neutrophils and fibrin, middle portion mainly fibrin (Blue on trichrome stain) and outer portion reactive gliosis. (By courtesy of Professor Ligia Coutinho).

1354 Parasitosis and infections

CLINICAL PRESENTATION There are no pathognomonic clinical signs. The symptomatic presentation depends on the location or mass effect of the lesion: headache, nausea, vomiting, fever, alteration in consciousness, seizures, and motor weakness are the most common symptoms. (5) Meningismus may be present (20 %) and papilledema identified in less than 50%. These symptoms are more rapidly progressive, however, compared to neoplasic lesions. Fever is not uniformly seen and only 30–55% of patients have a fever above 38.5ºC. (19)

DIAGNOSIS Laboratory tests such as leukocyte count, serum C-reactive protein level and erythrocyte sedimentation rate are not specific but are valuable in the evaluation of the patient’s response to treatment. (19) Culture of pus from the abscess, cultures of blood, (21) sputum, drainage from the ear or sinus, (26) and cerebrospinal fluid (if available without a danger of herniation) may be helpful, especially when the results of cultures of the abscess material are negative. Brain abscess development, as cited above, can be divided into 4 stages characterized on diagnostic exams: 1) early cerebritis (1–4 days); 2) late cerebritis (4–10 days); 3) early capsule formation (11–14 days); and 4) late capsule formation (after 14 days).(17) The CT appearance depends on the stage: • Cerebritic stage – thick diffuse ring of enhancement, further diffusion on contrast into central lumen or lack of decay of contrast on delayed scan 30-60 minutes later. • Capsular stage – faint rim present on pre contrast CT. (Necrotic center with edematous surrounding brain makes the collagen capsule easier to see.). Thin ring on enhancement and there is decay of enhancement on delayed scans. The majority of abscesses demonstrate considerable surrounding edema, which generally presents during the late cerebritis or early capsule formation stage, secondary to mass effect (figure 6). Hematogenous abscesses, which can be seen in the setting of endocarditis, cardiac shunts, or pulmonary vascular malformations, are usually multiple, identified at the gray–white junction, and located in the MCA territory (figure 5). Monitoring of therapy is performed biweekly: reduction in size, and not the enhancement, reflects the success of therapy. CT signs of maturation of the abscess are thinning out of the capsule, lack of contrast enhancement and reduction of brain edema. The diagnostic accuracy, sensitivity, specificity, and the positive and negative predictive values of conventional MR images are 61.4, 61.9, 60.9, 59.1, and 63.3%, respectively, while the respective rates for proton MR spectroscopy are 93.2, 85.1, 100, 100, and 88.5%. The addition of DW imaging increases the diagnostic accuracy further to 97.7%, the sensitivity to 95.2%, the specificity to 100%, the positive predictive value to 100%, and the negative predictive value to 95.8%. (24) The MR imaging findings in the early phase are lesions with a low signal on T1weighted and a high signal on T2-weighted images, with patchy enhancement. In later phases, the low signal on T1-weighted images becomes better demarcated, with a high signal on T2-weighted images, both in the cavity and surrounding parenchyma. The

Brain Abscess

1355

Fig. 5

Fig. 5, 6 CT image from multiple abscesses in a six-year-old child. Note a hypodense area surrounded by capsule, with contrast enhancement and intense vasogenic peripheral edema. Fig. 6

abscess cavity shows a hyperintense rim on T1-weighted images obtained without contrast and a hypointense rim on T2-weighted images (18). (figures 7, 8) MRI detects cerebritis earlier than CT. It may also differentiate abscess from other lesions, especially when using diffusion-weighted MR imaging (DWI - low in abscess and high in cystic tumors) and spectroscopy. (25, 11) The differential diagnosis includes other ring-enhancing lesions like high grade gliomas, a cystic/necrotic metastatic lesion, granuloma and a primary central nervous system lymphoma. Proton MR spectroscopy of intracranial abscesses usually demonstrates: absence of n-acetyl-aspartate (NAA), absence of choline; absence of phosphocreatine/creatine (PCr/Cr), presence of cytosolic amino acids such as leucine, isoleucine, and valine; presence of lactate, acetate, succinate, and alanine; and occasionally lipids. No peaks of NAA, choline or PCr/Cr should be detected. (23)

1356 Parasitosis and infections

Fig. 7 Cerebellar abscess due to open skull fracture.

Fig. 8 MRI (Sagital T2 and Axial T1 with contrast) of a frontal fungal abscess. The necrotic center and the peripheral contrast enhancement suggest a mature abscess.

The spectrum of cysticercosis is overall quite different, with characteristic concomitant increased concentrations of choline and PCr/Cr. (1) To differentiate abscesses from high-grade gliomas (anaplastic astrocytoma or glioblastoma multiforme), the detection of PCr/Cr in the later is of paramount importance. This metabolite is always detectable in gliomas but is not detected in abscesses. (23) Lipids and lactate may be detected in both lesions. (12) Likewise, increased concentration of choline can be helpful in differentiating between abscesses and lymphomas because this metabolite is always increased in lymphomas and absent in abscesses. (7) The occurrence of lipid peaks in a tumor spectrum suggests the presence of tissue necroses or metastasis. (30)

Brain Abscess

1357

TREATMENT MEDICAL MANAGEMENT In situations where the abscess is smaller than 1.5 cm or if the clinical condition precludes operative intervention (bleeding diathesis), medical treatment alone could be considered. In all other cases, it is recommended to obtain material for culture if possible, and then, to start antibiotics, treating the identified predisposing condition and performing surgical procedures when indicated. Antibiotics To choose the appropriate antibiotic, the microorganism or underlying illness must be identified. (15) If the patient is not in sepsis or critical condition, antibiotic therapy should be started after culture material is obtained. Systemic antibiotics should be given for 6 weeks, although some centers prescribe 2 weeks of intravenously administered antibiotics followed by up to 4 weeks of oral antimicrobial therapy. (27) The antibiotic regimen should be guided by the predisposing condition. (Table 1) When the source of the infection is obscure, a third-generation cephalosporin can be used in combination with both metronidazole and vancomycin. Seizure prophylaxis The preventive prescription and continuation of anticonvulsive therapy for an extended period are recommended for patients with brain abscesses (26). It must be initiated immediately and continued for at least 1 year due to the high risk of subsequent seizures in patients with brain abscesses. Glucocorticoids They should be used only when substantial mass effect can be demonstrated on imaging. Dexamethasone is administered at a loading dose 10 mg IV followed by 4 mg every six hours, and it should be discontinued as soon as possible. The addition of glucocorticoids has a number of disadvantages including: (31) decrease in contrast enhancement on CT scan, slowing of capsule formation, increased risk of ventricular rupture, diminished penetration of antibiotics into the abscess.

SURGICAL MANAGEMENT The patients presenting with rapidly progressive neurological deficits that are attributable to the mass effect of the neuroradiologically verified brain abscess must be considered for urgent surgical decompression. Aspiration is the gold standard for treatment of brain abscess. (29) Other possible indications of operative treatment beyond the cases in which there is evidence of increased intracranial pressure due to significant mass, should be if there are difficulties in diagnosis; if the abscess is the result of a traumatic injury that has introduced foreign materials; if the lesion is located in the posterior fossa; and if there is

1358 Parasitosis and infections

Fig. 9 Craniotomy for brain abscess: duramater is open and normal brain is seen on the right side, while abscess cavity is on the left.

any presumption of fungal infection (10). Excision of the abscess is indicated when there is a large subcortical abscess causing brain herniation, failure to repeated aspiration, retained foreign body, communication with infected extracerebral spaces or a diagnosis of fungal abscess. In epidural or subdural abscesses, treatment is also via craniotomy (Figure 9). Stereotactic aspiration is appropriate for small, deep-seated abscesses or those located in eloquent regions of the brain: it is ideal for management of abscesses in the thalamus, basal ganglia, or brainstem. (13) In the case of rupture into the ventricle, external ventricular drainage must be done immediately and intraventricular antibiotics should be considered. Because a diagnosis based only on clinical and neuroradiological findings can be erroneous, nonsurgical therapeutic decisions should not be made without a positive diagnosis of the pathogen. Stereotactic management of brain abscess, which allows both confirmation of the diagnosis and institution of therapy by aspiration of lesion contents and identification of the offending organism, has become widespread since the introduction of CT-guided stereotaxy. (2)

PROGNOSIS After 2000, the mortality rate was reported to be between 17 and 32%. (21) Xiao et al. (37) reported 2.8-fold risk of poor outcome in immunocompromised patients. Other clinical comorbidities like diabetes mellitus or cirrhosis are also factors negatively influencing the outcome. The pretreatment neurological status of the patient is the most influential independent factor related with the outcome. (33) Extremes of age, immunity, hematogenous source

Brain Abscess

1359

and localization (brain stem or basal nuclei) are associated with a high incidence of complications. The morbidity in survivors includes hemiparesis, seizures, and cognitive dysfunction. (5) Seizure is a long-term risk in 30–50% of patients suffering from brain abscesses. Rates of recurrence are estimated to be 10–50%. Thus, a period of surveillance should be continued for at least 1 year. The resolution of the surrounding edema and loss of the enhancing rim must be documented with CT scan in this period, which can take up to 6 months. (34) Clinicians should have a high index of suspicion for brain abscess because early diagnosis and treatment may importantly reduce morbidity and mortality.

IN A NUTSHELL Symptoms are non-specific and normally due to increased intracranial pressure / mass effect: headache, nausea/vomiting, or lethargy. Occasionally seizures. In the suspicion of brain abscess, a CT scan must be done for diagnosis, treatment decision and follow-up. In all patients the primary condition must be treated. A culture of the abscess should be obtained prior to the antibiotic treatment. Aspiration with or without stereotactic guidance is the preferable surgical treatment.

QUESTIONS 1) Consider a male patient, 36 years-old, with a metallic cardiac valve, who developed a brain abscess in the middle cerebral artery territory. Mark the alternative that includes the most probable causing organisms: a) S. Viridans, enterococci, Haemophilus spp, Staphylococcus spp. b) S. Viridans, enterococci, Haemophilus spp, S. aureaus c) S. aureus, Enterobacteriaceae, Pseudomonas spp. d) S. Viridans, enterococci, Pseudomonas spp, Staphylococcus spp. e) S. aureus, Pseudomonas spp, Staphylococcus spp. 2) About brain abscess location and the probable etiology, match the columns: 1 – Hematogenous dissemination 2 – Sinusitis 3 – Mastoiditis ( 2 ) Frontal lobe ( 3 ) Temporal lobe ( 3 ) Cerebellum ( 1 ) Basal ganglia ( 1 ) Middle cerebral artery territory

1360 Parasitosis and infections The order of numbers that better complete the empty spaces, from top to down, is: a) 1 – 3 – 3 – 1 – 2 b) 2 – 3 – 3 – 2 – 1 c) 2 – 3 – 3 – 1 – 1 d) 3 – 2 – 3 – 1 – 1 e) 2 – 3 – 1 – 1 – 1 For the next three questions, consider the case: A 27 years-old female presents with left hemiparesis and disorientation in time and space. She opens her eyes on verbal stimulation, obeys well to commands and can properly say her name. Family tells she is presenting with fever and chills for 6 days. Mouth examination shows dental infection . 3) Considering the following alternatives : I – CT scan. II – Start antibiotics immediately. III – Hemogram, C-reactive protein and hemoculture. IV – Lumbar puncture as soon as possible. The alternative that contains only the correct answers is: a) I, II and III. b) I and III. c) II and III. d) I, III and IV e) All are correct. 4) The patient went for a contrast CT scan, and the image shows an encapsulated and well organized subcortical brain abscess, measuring 2x2x2,5cm, in the right frontal lobe, with an extensive surrounding vasogenic brain edema. Her neurological state has worsened rapidly. She is now opening eyes only on pain stimulation, emitting incomprehensible sounds and localizing pain. Choose the alternative that contains the best procedures. a) perform lumbar puncture immediately for intracranial pressure reduction, start steroids and phenitoin, proceed for surgical drainage of the abscess and then start antibiotics. b) start steroids and phenitoin, proceed for surgical drainage of the abscess and then start antibiotics. c) start steroids and phenitoin, proceed for surgical drainage of the abscess, make lumbar puncture after surgery for identification of the causative organism. d) start steroids and phenitoin, start antibiotics, wait for better neurological conditions to proceed with surgery. e) perform lumbar puncture immediately for intracranial pressure reduction and identification of the causative organism, start steroids and phenitoin, and then start antibiotics.

Brain Abscess

5) a) b) c) d) e)

1361

The best choice for antibiotic treatment is the combination of: Vancomycin plus ceftazidine Penicillin plus oxacilin Vancomycin plus cephepime Cefotaxime plus ampicillin Penicillin plus metronidazole

REFERENCES 1. Agarwal M, Chawla S, Husain N, Jaggi RS, Husain M, Gupta RK: Higher succinate than acetate levels differentiate cerebral degenerating cysticerci from anaerobic abscesses on in-vivo proton MR spectroscopy. Neuroradiology 46:211–215, 2004. 2. Barlas O, Sencer A, Erkan K, Eraksoy H, Sencer S, Bayindir C: Stereotactic surgery in the management of brain abscess. Surg Neurol 52:404–411, 1999. 3. Britt RH, Enzmann DR, Placone RC Jr, Obana WG, Yeager AS: Experimental anaerobic brain abscess. Computerized tomographic and neuropathological correlations. J Neurosurg 60:1148–1159, 1984. 4. Canale DJ: William Macewen and the treatment of brain abscesses: revisited after one hundred years. J Neurosurg 84:133–142, 1996. 5. Cansever T, Izgi N, Civelek E, Aydoseli A, Kiris T, Sencer A:Retrospective analysis of changes in diagnosis, treatment and prognosis of brain abscess for a period of thirtythree-years, in 13th World Congress of Neurological Surgery, Marrakesh, June 19–24, 2005. Nyon Vaud, Switzerland: World Federation of Neurosurgical Societies, 2005. 6. Carpenter J, Stapleton S, Holliman R: Retrospective analysis of 49 cases of brain abscess and review of the literature. Eur J Clin Microbiol Infect Dis 26:1–11, 2007 7. Chinn RJ, Wilkinson ID, Hall-Craggs MA, Paley MN, Miller RF, Kendall BE, et al: Toxoplasmosis and primary central nervous system lymphoma in HIV infection: diagnosis with MR spectroscopy. Radiology 197:649–654, 1995. 8. Chun CH, Johnson JD, Hofstetter M, Raff MJ: Brain abscess. A study of 45 consecutive cases. Medicine (Baltimore) 65:415–431, 1986. 9. Dandy WE: Treatment of chronic abscesses of the brain by tapping. Preliminary note. JAMA 87:1477–1478, 1926. 10. Erdogan E, Canserver T. Pyogenic brain abscess. Neurosurg Focus 24 (6):E2, 2008. 11. Fichten A, Toussaint P, Bourgeois P, Gosset JF, Lejeune JP. Diagnostic problems in brain abscess: 45 cases. Neurochirurgie. 2001 Sep;47(4):413-22. 12. Fountas KN, Kapsalaki EZ, Gotsis SD, Kapsalakis JZ, Smisson HF III, Johnston KW, et al: In vivo proton magnetic resonance spectroscopy of brain tumors. Stereotact Funct Neurosurg 74:83–94, 2000. 13. Fuentes S, Bouillot P, Regis J, Lena G, Choux M: Management of brain stem abscess. Br J Neurosurg 15:57–62, 2001. 14. Garg M, Gupta RK, Husain M, Chawla S, Chawla J, Kumar R, et al: Brain abscesses: etiologic categorization with in vivo proton MR spectroscopy. Radiology 230:519–527, 2004. 15. Gortvai P, De Louvois J, Hurley R: The bacteriology and chemotherapy of acute pyogenic brain abscess. Br J Neurosurg 1:189–203, 1987. 16. Greenberg MS: Handbook of Neurosurgery, ed 5. New York:Thieme, 2001, pp 217–223. 17. Guzman R, Barth A, Lövblad KO, El-Koussy M, Weis J, Schroth G, et al: Use of diffusion-weighted magnetic resonance imaging in differentiating purulent brain processes from cystic brain tumors. J Neurosurg 97:1101–1107, 2002. 18. Haimes AB, Zimmerman RD, Morgello S, Weingarten K, Becker RD, Jennis R, et al: MR

1362 Parasitosis and infections imaging of brain abscesses. AJR Am J Roentgenol 152:1073–1085, 1989. 19. Hakan T, Ceran N, Erdem I, Berkman MZ, Göktas ¸ P: Bacterial brain abscesses: an evaluation of 96 cases. J Infect 52:359–366, 200612. Hegde AS, Venkataramana NK, Das BS: Brain abscess in children. Childs Nerv Syst 2:90–92, 1986. 20. Heineman HS, Braude AI, Osterholm JL: Intracranial suppurative disease. Early presumptive diagnosis and successful treatment without surgery. JAMA 218:1542–1547, 1971. 21. Kao PT, Tseng HK, Liu CP, Su SC, Lee CM: Brain abscess: clinical analysis of 53 cases. J Microbiol Immunol Infect 36:129–136, 2003. 22. Kaplan D: Brain abscess. Med Clin North Am 69:345–360, 1985. 23. Kapsalaki EZ, Gotsis ED, Fountas KN. The role of proton magnetic resonance spectroscopy in the diagnosis and categorization of cerebral abscesses. Neurosurg Focus 24 (6):E7, 2008. 24. Lai PH, Hsu SS, Ding SW, Ko CW, Fu JH, Weng MJ, et al: Proton magnetic resonance spectroscopy and diffusion-weighted imaging in intracranial cystic mass lesions. Surg Neurol 68 (Suppl):25–36, 2007. 25. Leuthardt, EC, Wippold FJ, 2nd, Oswood, MC, Rich, KM. Diffusion-weighted MR imaging in the preoperative assessment of brain abscesses. Surg Neurol 2002; 58:395. 26. Lu CH, Chang WN, Lui CC: Strategies for the management of bacterial brain abscess. J Clin Neurosci 13:979–985, 2006. 27. Mampalam TJ, Rosenblum ML: Trends in the management of bacterial brain abscesses: a review of 102 cases over 17 years. Neurosurgery 23:451–458, 1988. 28. Mathisen GE, Johnson JP: Brain abscess. Clin Infect Dis 25:763–781, 1997. 29. Osenbach RK, Loftus CM: Diagnosis and management of brain abscess. Neurosurg Clin N Am 3:403–420, 1992. 30. Papanagiotou P, Backens M, Grunwald IQ, Farmakis G, Politi M, Roth C, Reith W. MR spectroscopy in brain tumors. Radiologe. 2007 Jun;47(6):520-9. 31. Quartey, GR, Johnston, JA, Rozdilskyy, B. Decadron in the treatment of cerebral abscess: An experimental study. J Neurosurg 45:301, 1976. 32. Sheehan JP, Jane JA, Ray DK, Goodkin HP. Brain Abscess in Children. Neurosurg Focus 24 (6):E6, 2008. 33. Sichizya K, Fieggen G, Taylor A, Peter J. Brain abscesses--the Groote Schuur experience, 1993-2003. S Afr J Surg. 2005 Aug;43(3):79-82. 34. Tseng JH, Tseng MY: Brain abscess in 142 patients: factors influencing outcome and mortality. Surg Neurol 65:557–562, 2006. 35. Vincent C: Sur une méthode de traitement des abcès subaigus des hémisphères cérébraux: large décompression, puis ablation en masse sans drainage. Gaz Méd de Fr 43:93–96, 1936. 36. Whelan MA, Hilal SK: Computed tomography as a guide in the diagnosis and follow-up of brain abscesses. Radiology 135:663–671, 1980. 37. Xiao F, Tseng MY, Teng LJ, Tseng HM, Tsai JC: Brain abscess: clinical experience and analysis of prognostic factors. Surg Neurol 63:442–450, 2005. 38. Young JD, McGwire BS: Infliximab and reactivation of cerebral toxoplasmosis. N Engl J Med 353:1530–1531, 2005.

1363

Intracranial Supuration KAZADI K.N. KALANGU University of Zimbabwe College of Health Sciences Harare – ZIMBABWE Key words: Intracerebral abscess, Epidural empyema, Subdural empyema, Spinal Epidural Abscess, Epidemiology, Symptoms, Neuroradiological Findings, Management

BRAIN (CEREBRAL) ABSCESS Cerebral abscesses have proven to be one of the disease that can be treated successfully. This good outcome has been facilitated by a number of technological advancements in particular the imaging techniques (CTScan and MRI), better personal hygiene, better isolation techniques for identification of microorganisms, imaging-assisted stereotaxy and real time ultrasound imaging for the drainage of the suppuration. However, brain abscesses still remain a serious condition which should be prevented rather that treated.

EPIDEMIOLOGY There is a great variation in the incidence of cerebral abscess from one geographical area to another. For instance, Bhatia in India (7)reported an incidence of 8 per cent and this contrasts dramatically with the rates from more developed countries where cerebral abscesses constitute between 2 and 5 per cent of intracranial lesions (1 ,17, 49, 60) However, despite the widespread use of modern antibiotics in the treatment of the predisposing causes of cerebral abscesses and improved living standards in developed countries , the incidence has changed little (58,49,60). The age group which is mostly affected is the first four decades of life and mostly in male patients for unclear reasons (1,19,37,58,73). We presume this is due to better hygienic behavior and personal care of females in any given society. Of note is the fact that brain abscess before the age of 2 years is rare and when present, it is due to Citrobacter Diversus or Proteus infections (15,17,43,60).

ETIOLOGY Focal suppuration occurs when microorganisms are introduced into the cerebral tissue following a penetrating trauma, contiguous infection, hematogenous dissemination and neurosurgical procedures (13, 19, 24, 36, 39). Further more, some conditions which are compromising the body’s immunity such as Acquired Immune Deficiency Syndrome (AIDS), malignancy, organ transplantation, and chronic corticosteroid therapy may predispose more some patients than others in the development of brain

1364 Parasitosis and infections abscess (1, 7 12, 52, 67). In general, the source of the suppuration can be identified in up to 80 % of patients but it will remain obscure in 10 to 37 percents of them (67,73). Penetrating trauma due mostly to head injury is a well known cause of Brain abscess which will develop from retained bone fragments, retained foreign bodies or by delayed contamination of the initially clean site from an overlying infection. Retained bullet or missile fragments, especially those with high velocity injuries, are less likely going to cause a brain abscess because the high temperature and friction generated by the projectile will sterilize the adjacent tissues. These abscesses are rather rare and when they do occur, they tend to present many years after the initial injury (7, 13 73). Other causes in this category include open depressed, basilar skull fracture with associated cerebrospinal fluid (CSF) fistulas, animal bites, and, especially in children, injuries from lawn darts or pencil tips. Traumatic abscesses may be prevented by thorough debridement of devitalized tissue, removal of accessible foreign material, and achievement of a water-tight dural closure (7, 13, 39, 67, 73). Contiguous focus of Infections from paranasal sinuses, middle ear, mastoid , and dental area is the major cause of most abscesses. The lesions tend to be solitary and superficial. The incidence of contiguous spread of infection into the cerebral parenchyma is decreasing in most part of the world because of prompt treatment of the primary causes. Paranasal and ethmoidal sinuses infection as well as the dental infection spread to the brain to the frontal or temporal lobe via retrograde thrombophlebitis of the diploic veins. Osteomyelitis and dehiscence of the posterior table of the frontal sinus can also result in direct extension of infection to the anterior and basal regions of the frontal lobe. Infection initiating from sphenoidal sinus tends to spread to the temporal lobe. Middle ear infections and mastoidis most often lead to temporal or cerebellar abscess (67, 73). Another mechanism of cerebral abscess formation is through hematogenous dissemination of microorganisms from distant infections. The incidence of this type of abscess is increasing (39, 73) as opposed to the one caused by contiguous infection. Most of the time, theses abscess are multiple, deep seated, and poorly encapsulated (11, 17, 19). They occur at the corticomedullary junction, where the blood flow is slow and they have a less favorable prognosis. The mortality and morbidity are very high. They tend to be distributed proportionately to regional blood flow and most commonly occur in the frontal and parietal lobes (13, 14, 29). However other sites such as the brainstem and the cerebellum may be involved as well. The initial source of infection is found within the chest in chronic pyogenic lung diseases such as pneumonia, lung abscesses, bronchiectasis, and empyema. Other causes are skin pustules, osteomyelitis, pelvic and intra-abdominal infections, congenital cyanotic heart disease, right -to-left vascular shunts, and pulmonary arteriovenous malformations. Tetralogy of Fallot and transposition of the great vessels are the most common culprits (11, 19, 39, 73). Cerebral abscess may also occur as a complication of a neurosurgical procedure and the incidence is increasing. The mechanism is a direct contamination during the procedure or secondary to an infection of the bone flap. These complications require debridement, removal of the infected bone flap, and meticulous dural repair to prevent cerebral abscess (24, 67, 73). More and more patients are presenting with an immunocompromised state as the only

Intracranial Supuration

1365

predisposing condition. There are several reasons for immune suppression, including AIDS, chronic debilitating diseases such as diabetes, cancer chemotherapy, immunosuppression following organ transplantation and chronic corticosteroids for various inflammatory and autoimmune conditions. These patients present not only with bacterial abscesses but also with abscesses caused by atypical bacteria, fungi , and parasites (52, 67, 73).

HISTOGENESIS AND MICROBIOLOGY There are four stages in the development of a brain abscess (8, 11, 13, 14, 29). Early cerebritis (days 1-3) shows a necrotic center accompanied by a local inflammatory response surrounding the adventitia of blood vessels. These findings are associated with the development of edema. In the late cerebritis stage (days 4-9), edema is at its maximum and the necrotic center increases while pus starts to accumulate. On the periphery of this inflammatory zone, fibroblasts accumulate and they will serve as the precursor to the collagen capsule. Early capsule formation (days 10-13) occurs when the collagen network is consolidated and the necrotic center is isolated from the adjacent parenchyma. The late capsule formation (day 14 and later ), the abscess has five distinct regions namely, the necrotic center, a peripheral zone of inflammatory cells and fibroblasts, a collagen capsule, an area of neovascularity, and an area of reactive edema (8, 11, 29).The evolution of a well formed capsule takes about 2 weeks. Microorganisms found in the abscess are mostly gram-negative bacteria as opposed to staphylococcal infections which have declined because of widespread use of antibiotics. The improvements of isolation techniques have also contributed to better identification of anaerobic species (1, 13, 15, 19, 31, 48, 60, 73 ).

CLINICAL PRESENTATION Most patients present with signs of raised intracranial pressure (ICP) associated or no with focal neurological signs. The later will depend upon the location ,the size, the number of lesions, the virulence of the organisms, the host response , and the severity of the cerebral edema (60,73). The predominant sign found in 70 to 97% of patients is headache (63, 67, 73). which is constant, progressive, and refractory to treatment. Vomiting may be present as well in 25-50% of patients. Low- grade fever (fig.1) is observed in more than 50% of patients (17, 19, 39, 67, 73) and fever exceeding 38.6°C is associated with concomitant systemic infection or meningitis. 75% of patients have impaired level of consciousness varying from mild drowsiness and confusion to various degree of coma (1, 17, 19, 39, 67, 73). Focal signs are present in more than 60% of patients in relation to the location of the abscess and include hemiparesis, aphasia, visual fields defect, and when located into the cerebellum, nystagmus , dysmetria and ataxia (71, 73). Seizures present in 30 to 50 % of patients before any operation (1, 39, 67, 73). Brainstem lesions present with facial weakness, dysphasia, and hemiparesis. Children present with a combination of enlarging head, bulging fontanelle, separation of cranial sutures, vomiting, irritability, seizures, and poor feeding (1, 15, 20, 73).

1366 Parasitosis and infections

Fig. 1 Typical low grade fever in Brain Abscess.

Laboratory analysis have little value. Cerebro Spinal Fluid (CSF) findings are nonspecific. The opening pressure is usually high, confirming raise ICP. There is mild pleiocytosis, with white cell counts less than 100 per cm3 unless there is coexisting meningitis. Protein is less than 100mg per dL and infrequently reduced glucose particularly when there is concomitant meningitis. Lumbar puncture should be avoided because of the presence of raised ICP and given the fact that the CSF findings are nonspecific (56). In the blood analysis, there is mild leukocytosis (less than 15 000/cm3) in 60-70% of patients. White blood cell counts above 20 000/ cm3 suggests concomitant meningitis or other systemic infection. The erythrocyte sedimentation rate (ESR) is elevated in up to 90% of patients and remain non- specific particularly in patients with polycythemia in case of cyanotic congenital heart disease (39, 41, 49, 63, 67, 73).

NEURORADIOLOGY OF CEREBRAL ABSCESS The advent of CTscan and MRI have helped significantly in terms of speed and diagnostic accuracy. Moreover, the once high morbidity and mortality has improved remarkably. CTscan shows a smoothly countoured on the inner surface , thin, regular contrast medium-enhanced wall with a central region of hypodensity (fig.2). During the

Fig. 2 Ctscan. Brain abscess with regular contrast medium-enhanced wall. Note signs of cerebritis around the absess.

Intracranial Supuration

1367

Fig. 3 CtScan of Brain Abscess with smoothly countoured on the inner surface. There is a thin regular contrast medium-enhanced wall with a central region of hypodensity.

early cerebritis stage, Ctscan reveals an irregular area of low density with minimal enhacement (13, 14, 20, 27, 29) Magnetic resonance imaging is more sensitive than CTscan in detecting the early changes of cerebritis, and the extend of cerebral edema. On T1-weighted images, brain abscess appears with a central zone of marked signal hypointensity corresponding to the necrotic center surrounded by a peripheral region of mild hypointensity.The capsule appears as a discrete rim that is isodense to mildly hyperintense. On T2-weighted images, the lesion shows a hyperintense center, a hypointense capsule, and a surrounding area of hyperintense edema (fig.3). Administration of gadolinium shows enhancement of the capsule with clear separation from the surrounding brain (20, 34, 39, 67, 73)). The CTscan and MRI findings are not pathognomonic and differential diagnosis should include malignant glioma, metastatic tumors, infarction, resolving hematoma, and radiation necrosis (27, 34, 39, 44).

MANAGEMENT OF BRAIN ABSCESS Management of brain abscess is both medical and surgical except in situations where there is widespread small abscesses (less than 1.5 cm of diameter) non surgically accessible (10, 17, 28). Moreover, medical treatment only is preferred when surgical morbidity is too high, and in the early stages of abscess formation (cerebritis). In this case, Antibiotics should be administered for at least 6 -8 weeks and much longer in immunecompromised patients. Follow up should include weekly CT-scan or MRI up to the end of the treatment or when clinical picture deteriorates. Thereafter monthly or two monthly should be done until the abscess is completely absorbed. Corticosteroids may be added only when there is marked edema and mass effect until clinical condition stabilizes (5, 9, 17, 65, 73). Antibiotic therapy should be specific to the responsible organism following culture and sensitivity possibly from the abscess itself. Most of the time however, the organism has yet to be indentified and antibiotherapy should target the most likely organism according to the etiology , the origin of the infection and the previously commonly isolated organisms (13, 17, 20, 31, 36, 67, 73). If the etiology is unknown, empiric

1368 Parasitosis and infections therapy should be commenced with penicillin or third generation cephalosporin if abscess originates from the sinus and therefore due to carboxyphilic streptococci. Metronidazole must also be included against anaerobes (17, 19, 20, 36, 67, 73). Abscesses of otogenic origin have mixed flora of anerobic and aerobic bacteria which will be better treated with multiple broad-spectrum antibiotics covering anaerobes, Gramnegative aerobes and Streptococci. Penicillin, metronidazole, and a third-generation cephalosporin may be adequate. Metastatic abscesses tend to respond to the same treatment. Post traumatic abscesses are due to Staphylococcus aureus and respond better to semi-synthetic penicillinase-resistant penicillin or vancomycin. If Pseudomonas aeruginosa is suspected, third generation cephalosporin would be appropriate. Where the microorganism is completely unknown, a combination of third generation cephalosporin, metronidazole and vancomycin would be the best selection (13, 15, 17, 19, 20, 26, 31, 36, 39, 67, 73). Surgical management has a number of advantages namely to decompress the neural tissues, to remove dead tissues which acts as nidus for microorganisms and allows to culture the responsible organism. Various surgical procedures have been advocated and the most common include aspiration, continuous drainage, and complete excision (7, 13, 17, 24, 36,39, 49, 53, 60, 61, 73). In our experience, we prefer aspiration through a burr hole only and good results have also been reported by other authors as well (39,49, ,61, 73). The procedure is simple, minimally traumatic and efficient particularly in this type of patients who are most of the time very ill. More precision may be obtained by using imaging-guided stereotaxy or real time ultrasound scan. Multiple lesions may be aspirated through a single burr hole if abscesses are in the same hemisphere. Deepseated abscesses are better managed by CT-guided stereotactic aspiration (7, 13, 17, 24, 36, 39, 49, 53, 60, 61, 67, 73). In some situations, excision is preferred namely in posterior fossa abscess where recurrence must be avoided at any cost. Traumatic abscesses which may contain foreign bodies, like bone fragments or sands should benefit from excision to avoid recurrence. Fungal abscesses require excision because of poor sensitivity of fungi to conventional antimicrobial agents and also these organisms tend to be located into the capsule (71, 73).

PROGNOSIS Prognosis has improved significantly because of early diagnosis, appropriate antibiotherapy and minimally traumatic surgical techniques. Excellent results depend also upon the neurological state of patient before the operation, patients with no neurological impairment having the best response. We should remember that brain abscess remain a serious disease which may still cause death if treatment is delayed causing sudden raised ICP due to rupture into the ventricular system (17, 67, 73). Morbidity in successfully treated patients is mostly due to seizures, cognitive dysfunction, and focal neurological deficits. Epilepsy is the commonest and is found in about 30-50% of patients, more in patients treated with excision than aspiration (50, 67, 73) , and is usually well controlled with anticonvulsants. Patients who had at least two seizures should be treated for a least 12 months until EEG is normal. Recurrence occur in about 5-10% of patient and mostly within 6 weeks after even adequate treatment.

Intracranial Supuration

1369

However the commonest causes are , wrong antibiotic choice, inadequate aspiration, presence of foreign bodies, presence of fistula, and failure to eradicate the source of infection (1, 19, 36, 39, 67, 73).

INTRACRANIAL SUBDURAL ABSCESS Subdural abscess or subdural empyema (SDE) is a collection of pus into the subdural space which is not confined like brain hence the tendency of this entity to spread easily. It accounts for approximately 20-33% of all intracranial infections (63, 68, 73). Frequencies may vary between developed and developing countries (58, 73). Male:female ratio is 3:1. They are mostly localized in 70-80% over the convexity and in 10-20% on the parafalcine area (62, 73). The etiology is most of the time a direct extension of a local infection from sinusitis, middle ear infection, compound skull fractures, postoperative infection of a craniotomy cavity (62, 68, 69) In infants, infection of meningitis-induced sterile effusion is the most common cause of subdural empyema. The majority of cases however in the setting of sinusitis, have a fulminant clinical course, and require prompt diagnosis and emergent neurosurgical intervention (49, 58, 68, 73). Bacterial organisms gain access to the subdural space from paranasal sinus and otitic infections by way of retrograde thrombophlebitis of bridging emissary veins (58, 62, 73). Though the arachnoid acts initially as a barrier to the deeper spread of infection, unrestricted access in the supratentorial subdural space allows a thin layer of purulent material to be deposited diffusely over the cerebral convexity and /or in the parafalcine and paratentorial regions. An epidural empyema may occur in association with osteomyelitis of the posterior paranasal sinus wall. Progression of thrombophlebitis to involve the cortical veins and major dural sinuses ensues, with edema and ischemia of the subjacent cortex. Without prompt and aggressive therapy, irreversible dural sinus and venous thrombosis and secondary parenchymal infection and infarction occur (58, 73). Clinical presentation includes high fever in 96% of patients, altered mental status 6070%, focal neurological deficit mostly hemiparesis (80-90%), nuchal rigidity (80%), headache (77%), seizures (50-60%), periorbital swelling and swelling of forehead (30%), and vomiting (20%) (34, 49, 58, 62, 68, 73).

Neuroradiology of SDE The best investigations are CTScan and MRI. Ct scan shows a hypodense (but denser than the CSF) crescentic or lenticular extracerebral lesion with dense enhancement of medial membrane (fig.4); inward displacement of gray-white interface; ventricular distorsion and effacement of basal cisterns are common findings. MRI shows a ‘pial ependymal line’, a non-specific MRI finding in CNS infection (20, 34, 49, 58, 62, 68).

Management This is an emergency and treatment is both medical and surgical. Medical treatment

1370 Parasitosis and infections

Fig. 4a CtScan;Subdural Empyema. Hypodense and lenticular extradural lesion with shift of the midline.

Fig. 4b CtScan showing a parafalcine and parietal subdural empyema.

Fig. 4c MRI: Subdural empyema with dense enhancement of medial membrane.

will depend upon the type of microorganisms found and the commonest are: aerobic streptococcus, Staphylococci, Streptococcus pneumonia, Haemophilus influenzae, microaerophilic and anaerobic streptococci, and other anaerobes, however culture may be sterile if the patient is on antibiotics. Like for intracerebral abscesses, a combination of Vancomycin, Metronidazole and third generation cephalosporine is adequate (24, 58, 68, 69, 73). Surgical treatment aim to drain as much pus as possible. There is still a debate regarding the performance of a craniotomy or a burr hole. Whatever is the choice, the opening should be adequate to remove septations. Dura is usually tense and appears white because of underneath pus. After opening the dura, usually pus comes out under pressure and thereafter the opening is obstructed by the brain. The later should be pushed gently inside in order to drain further pus which is usually on the periphery. Cavity could be washed out with normal saline and vacomycin (24, 58, 68, 69, 73).

Intracranial Supuration

1371

Prognosis This depends a lot upon initial Glasgow Coma Scale and the speed with which the treatment is initiated. Mortality is about 10-20%. Rapid recognition, surgical evacuation of subdural empyema and aggressive management with antibiotics for a period of 3-6 weeks with close monitoring of clinical status will reduce the mortality and gives the patient a good chance of recovery with little or no neurological deficit (49, 58, 69). Morbidity is due to persistent seizures (34%) and Residual hemiparesis (17%) (49, 5!, 69, 73).

INTRACRANIAL EPIDURAL ABSCESS Described first in 1760 by Sir Percival Pott who also documented the associated scalp swelling, the so-called Pott puffy tumor. Cranial epidural abscess (CEA) is the third most common localized intracranial infection, after brain abscess and subdural empyema. It is defined as a suppurative infection of the epidural space. In about 10% of cases, epidural abscess is associated with subdural abscess. It can result from spread of infection from paranasal sinuses, middle ear, orbit, mastoid or as a direct contamination from penetrating trauma or contamination at the time of surgery (8, 24, 30, 45). Overall incidence is unknown (59, 73), however, it is known that 90% of epidural abscesses occur mostly in the spine. It occurs particularly in older children and adults (8, 24, 40). Clinically, patient presents with high fever (Fig.5), headache, diffuse or localized to one side with scalp tenderness. Purulent discharge from the ears or sinuses, periorbital swelling, and brawny edema of the scalp as well (Fig. 6). Seizure is very rare unless CEA is associated to subdural empyema (3, 8, 24, 45, 59, 73). Epidural abscess usually occurs as a result of infection caused by Staphylococcus aureus, Staphylococcus epidermidis, enteric gram-negative bacilli (especially Escheria coli), Pseudomonas species, Bacteroides species, and other anaerobes. Haemophilus influenza may also be the responsible organism, in addition to Mycobacterium tuberculosis, Proteus penneri, Actinomyces species, Aspergillus fumigates, and Cladosporium species (3, 49, 59, 67).

Fig. 5 Pott Puffy tumor in a 9 year old boy.

1372 Parasitosis and infections

Fig. 6 High grade fever in subdural abscess.

Laboratory studies reveal polymorphonuclear (PMN) leukocytosis and elevated erythrocyte sedimentation rate (ESR). Results of blood culture may be positive. Hyponatremia has been reported in approximately 30% of cases (24, 35, 59, 73).

Neuroradiology Plain skull x-ray demonstrates the responsible sinusitis, mastoiditis, or osteomyelitis. Brain CT scanning without enhancement shows the abscess as a poorly defined lentiform area of low or intermediate density (Fig.7). CT scanning can also show bony destruction and fragmentation in patients with underlying mastoiditis. When contrast is administered, the convex inner side of the low-density lesion becomes enhanced and appears as rim enhancement caused by the inflamed dura. Brain MRI is the diagnosis of choice and it shows epidural fluid collection which has a higher signal than CSF on both T1- and T2-weighted MRI. Use of gadolinium can significantly enhance the dural on T1-

Fig. 7 Epidural abscess. Coronal view.

Fig. 7 Ctscan of epidural abscess. Lentiform lesion with contrast enhacement of the inner side due to inflamed dura.

Intracranial Supuration

1373

weighted MRI. MRI is particularly useful in differentiating subdural empyema from CEA. The typical MRI feature includes a crescentic or lentiform (Fig.7) fluid collection overlying the hemisphere or in the interhemispheric fissure, which is mildly hyperintense relative to CSF on T1-weighted images and isointense to CSF on T2-weighted images. A hypointense medial rim, representing the displaced dura is very characteristic of CEA (8, 20,34,49, 59, 67, 73). The goal of the treatment is to eradicate the infection and prevent further complications. A multidisciplinary approach involving an otolaryngologist may be necessary if patient presents with concurrent paranasal sinusitis. Until the culture and sensitivity report of the infectious agent become available, the choice of empiric antibiotic therapy should be based on the underlying etiology. Antibiotics must cover a broad spectrum of both aerobic and anaerobic bacterial organisms for a minimum of 8 weeks if surgery is not undertaken and for at least 4 weeks if the abscess is drained. Optimal treatment should include neurosurgical drainage except in case of very small abscesses. When burr holes cannot provide sufficient drainage or when debridement with drainage is indicated, craniotomy is undertaken (3, 8, 24, 30, 35, 37, 38, 49, 57, 59, 73).

SPINAL EPIDURAL ABSCESS Spinal epidural abscess (SEA) is a suppurative process which might compress the spinal cord on the cervical, thoracic or lumbar area even though they are frequently found on the thoracic spine, the cervicothoracic junction and between T11 and L2. These location are due to the anatomy which shows more epidural space in these locations. Because of the lack of resistance to rostro-caudal spread, abscesses located posteriorly may extend over several vertebral segments. In contrast, abscesses which occur ventrally are often associated with osteomyelitis and longitudinal extension over several segments is restricted by the adherence of the dura (16, 22, 32, 33, 40, 42).

Etiology Contamination of the epidural space can occur by extension from contiguous site of infection, by hematogenous seeding from distant infection (skin, urinary tract infection, respiratory tract infection, intrabdominal abscesses, septic arthritis, vertebral body osteomyelitis) , by direct contamination during medical procedure like lumbar puncture or epidural anaesthesia and ,Ct-guided needle biopsy (4, 6, 21, 23, 25, 32). General health condition plays also a role since 50% of patient with SHA have impaired immune sytem (32, 40, 55, 66).

Clinical presentation The classical presentation occur most of the time in four stages: 1)spinal pain worsening over time associated with high temperature (>38°); 2) Radicular pain; 3) progressive loss of power, sensation and incontinence; 4) complete loss of power. These stages may evolve very rapidly, sometime over hours or days, hence the necessity to make the diagnosis a soon as possible. The total power deficit which may take place is most of

1374 Parasitosis and infections

Fig. 8a MRI Spinal Epidural Abscess, thoraci spine

Fig. 8b MRI spinalepidural abscess in the Lumbar region.

the time irreversible. The reason being that vascular mechanisms are involved since thrombosis of small veins and arteries were found within the subarachnoid space. Other observation showed inflammatory infiltrates in the pia directly involving the walls of blood vessels even within the lumen of the anterior spinal artery (16, 32, 55, 64, 66, 70).

NEURORADIOLOGY OF SEA The gold standard standard for the diaganosis of SEA is MRI which will display the abscess and demonstration of the spinal cord compression (Fig.8). Ct scan shows better the bony destruction (2, 51, 70).

TREATMENT Treatment is both surgical and medical. Surgery allows the decompression of spinal cord and therefore preventing any neurological deficit. The procedure should target the area where there is maximum compression and consists of laminectomy limited to the affected area. If the compression is mostly anterior, an anterior approach would be most suitable. In the case where bone destruction is present, reconstruction must be done with autologous bone (25, 33, 55, 54). Medical treatment is always associated and targets Staphylococcus aureus which is the main microorganism isolated in 45-95% of the cases. Other Gram-positive cocci are Staphylococcus epidermidis, Streptococcus pneumonia and Streptococcus viridians for 10%. In recent years, Gram negative aerobes such as, Escherichia coli, Pseudomonas aeruginosa, Klelbsiella pneumonia, Citrobacter have been isolated as well. Mycobacterium tuberculosis continuous to play a role particularly with the AIDS endemic. There are also a number of less common organisms which have been reported; Nocardia, Actinomyces israelii, Clostridium perfringens,

Intracranial Supuration

1375

Brucella, Listeria an Aspergillus (8, 21, 33, 46, 47, 51, 54). Antibiotics specific to the offending organism should be initiated as early as possible. While awaiting results from culture of infected material, anti-staphylococcal agent associated to broad spectrum coverage for Gram-negative aerobes. The recommended duration for the antibiotic therapy is 4-6 weeks. In case of Mycobacterium tuberculosis, the treatment may take up to one year (18, 33, 40, 47, 55).

Prognosis The outcome is in relation to neurological deficit, the type and timing of surgery associated to a correct antibiotic therapy. Mortality is unfortunately still high and 20-30% of patients will survive with significant neurological impairment (4, 18, 21, 23, 33, 40, 42, 64).

REFERENCES 1. Alderson D, Strong AJ, Ingham HR, Selkon JB: Fifteen-year review of the mortality of brain abscess. Neurosurgery 1981; 8: 1-5 2. Antuaco EJ, McConnell JR, Chadduck WM, et al: MR imaging of spinal epidural sepsis. AJNR 1987; 8: 879-883 3. Ariza J, Casanova A, Fernandez Viladrich P, et al: Etiological agent and primary source of infection in 42 cases of focal intracranial suppuration. J. clin Microbiol 1986; 24: 899902 4. Baker AS, Ojemann RG, Schwarts MN, et al: Spinal epidural abscess. N. Engl J Med 1975; 293: 463-468 5. Barsoum AH, Lewis HC, Cannillo KL: Nonoperative treatment of multiple brain abscesses. Surg Neurol 1981; 16: 283-287 6. Bedforth NM, Aitkenhead AR, Hardman JG: Haematoma and abscess after epidural analgesia Br J Anaesth. 2008; 101: 291-293 7. Bhatia R, Tandon PN, Banerji AK: Brain abscess – an analysis of 55 cases. Int Surg 1973; 58: 565-568 8. Bleck TP, Green Lee JE, Mandell GL, et al: Principles and Practice of Infectious Diseases. New York: Churchill Livingstone; 2000: 1028-1031 9. Bohl I, WallenFang T, Bothe H, Schurmann K: The effect of glucocorticoids in the combined treatment of experimental brain abscess in Cats. Adv Neurosurg 1981; 9: 125133 10. Boom WH, Tuazon CU: Successful treatment of multiple brain abscesses with antibiotics alone. Rev. Infect Dis 1985; 7: 189-199. 11. Britt RH, Enzmann DR, Remington JS: Neuropathological and computerized tomographic findings in experimental brain abscess. J. Neurosurgery 1981; 55: 590-603 12. Britt RH, Enzmann DR, Remington JS: Intracranial infection in cardiac transplant recipients. Ann Neurol 1981; 9: 107-119 13. Britt RH: Brain abscess. In Wilkins RH, Rengachary SS (eds): Neurosurgery. New York; McGraw-Hill, 1985, pp 1928-1956. 14. Britt RH, Enzmann DR: Clinical stages of human brain abscess on serial CT Scans after contrast infusion: Computerized tomographic, Neuropathological, and Clinical correlations. J. Neurosurg 1983; 54: 972-989. 15. Brook I: Bacteriology of intracranial abscess in children. J Neurosurg 1981; 54: 484-488. 16. Browder J, Meyers R: Pyogenic infections of the spinal epidural space. A consideration

1376 Parasitosis and infections of the anatomic and Physiologic pathology. Surgery 1947; 10: 296-308. 17. Cavusoglu H, Kaya RA, Türkmenoglu ON, Clak I, Aydin Y: Brain abscess : analysis of results in a series of 51 patients with a combined surgical and Medical approach during an 11-year period. Neurosurg Focus. 2008; 24 (6): E9. 18. Chen WC, Wang JT, Chen YC, Chang SC: Spinal epidural abscess due to Staphylococcus aureus: clinical manifestations and outcomes. J Microbiol Immunol Infect. 2008; 41: 215221. 19. Chun CH, Johnson JD, Hosfstetter M, Raff MJ: Brain abscess. A study of 45 consecutive cases. Medecine (Baltimore) 1986; 65: 415-431. 20. Cure J: Imaging of intracranial infection. In: Batjer H, Loftus CM (eds). Textbook of Neurological Surgery- Philadelphia: Lippincott Williams & Wilkins; 2003; 3108-3130. 21. Curling OD, Gower DJ, Mc Whorter JM: Changing concepts in spinal epidural abscess: a report of 29 cases. Neurosurgery 1990; 27: 185-192. 22. Dandy WE: Abscess and inflammatory tumors in the spinal epidural space (so-called pachymeningitis Externa). Arch Surg 1936; 13: 477-494. 23. Danner RL, Hartman BJ: Update of spinal epidural abscess: 35 cases and review of the literature. Rev Infect Dis 1987; 9: 265-274. 24. Dashti SR, Baharvahdat H, Spetzler RF, Sauvagean E, Chang SW, Stiefel MF, Park MS: Operative intracranial infection following craniotomy. Neurosurg Focus. 2008: 24 (6): E10 25. de Goeij S, Nisolle JF, Glupcznski Y, Delgrange E, Delacre B: Vertebral osteomyelitis with spinal epidural abscess in two patients with Bacteroides fragilis bacteraemia. Acta Clin Belg. 2008; 63 (3): 193-196. 26. de Louvois J: The bacteriology and chemotherapy of brain abscess. J Antimicrob Chemother. 1978; 4: 395-413. 27. Doblin JF, Healton EB, Dickinson PC, Brust JCM: Nonspecificity of ring enhancement in “medically cured” brain abscess. Neurology 1984; 34: 139-144. 28. Dyste GN, Hitchon PW, Menezes AH, et al: Stereotaxic surgery in the treatment of multiple brain abscesses. J Neurosurg 1988; 69: 188-194. 29. Enzmann DR, Britt RH, Placone K: Staging of human brain abscess by computed tomography. Radiology 1983; 146: 703-708. 30. Erman T, Demirhindi H, Göçer AL, Tuna M, Jidan F, Boyar B: Risk factors for surgical site infections in neurosurgery patients with antibiotic prophylaxis. Surg Neurol. 2005; 63: 107-112. 31. Everitt ED, Strausbaugh LJ: Antimicrobial agents and the central nervous system. Neurosurgery 1980; 6: 691-714 32. Feldenzer JA, Mc Keever PE, Schaberg DR, et al: The pathogenesis of spinal epidural abscess; microangiographic studies in an experimental model. J Neurosurg 1988; 69: 110114. 33. Fischer EG, Greene CS, Winston KR: Spinal epidural abscess in children. Neurosurgery 1981; 9: 257-260. 34. Foerster BR, Thurnher MM, Malani PN, Petrou M, Carets-Zumelzu F, Sundgren PC: Intracranial infections: clinical and imaging characteristics. Acta Radiol. 2007; 48: 875893. 35. Fountas KN, Duwayri Y, Kapsalaki E, et al: Epidural intracranial abscess as a complication of frontal sinusitis : case report and review of the literature. South Med J. 2004; 97: 279282. 36. Garfield J: Management of supratentorial intracranial abscess: a review of 200 cases. Br Med J 1969; 2: 7-11. 37. Germiller JA, Monin DL, Sparano AM, Tom LW: Intracranial complications and their outcomes. Arch. Otolaryngol Head Neck Surg. 2006; 132: 969-976.

Intracranial Supuration

1377

38. Green HT, O”Donoghue MA, Shaw MD, Dowling C: Penetration of Ceftazidine into intracranial abscess. J Antimicrob Chemother. 1989; 24: 431-436. 39. Gómez J, Garcia-Vázquez E, Martinez Pérez M, Martinez Lage JF, Gónzalez Tortosa J, Pérez Espejo MA, Ruiz J, Canteras M, Herrero JA, Valdés M: Brain Abscess. The esperience of 30 years. Med Clin (Barc). 2008 May 24; 130 (19): 736-739. 40. Hernández AG, Fernández JC, Pi OF, Román MP, Toledo VA, Gallego JH: Epidural spinal abscesses. Review of a clinical serie Neurologia. 2008 Mar;23(2): 85-90. 41. Hirschberg H, Bosnes V: C-reactive protein levels in the differential diagnosis of brain abscesses. J. Neurosurg. 1987; 67: 358-360. 42. Hlavin ML, Kaminski HJ, Ross JS, et al: Spinal epidural abscess : a ten-year perspective. Neurosurgery 1990; 27: 177-184. 43. Kagawa M, Takeshita M, Yato S, Kitamura K: Brain abscess in congenital cyanotic heart disease. J Neurosurg 1983; 58: 913-917. 44. Kapsalaki EZ, Gotsis ED, Fountas KN: The role of proton magnetic resonance spectroscopy in the diagnosis and categorization of cerebral abscesses. Neurosurg Focus. 2008; 24(6): E7. 45. Kaptan H, Cakiroglu K, Kasimcan O, Killiç C: Bilateral frontal epidural abscess. Neurocirurgia (Astur). 2008;19(1):55-57. 46. Kraus WE, McCornick PC: Infections of the dural spaces. Neurosurg Clin N Am 1992;3:421-434. 47. Kaufman DM, Kaplan JG, Litman N: Infectious agents in spinal epidural abscesses. Neurology 1980; 30: 844-850. 48. Kole M, Rosenblum M: Bacterial brain abscess. In: McCutcheon I, Hall W (eds). Infections in neurosurgery, American Association of Neurological Surgeons, Neurosurgical Topics Series. Rolling Meadows, IL: American Association of Neurological Surgeons; 2001: 23-32. 49. Kombogiorgas D, Seth R, Athwal R, Modha J, Singh J: Suppurative intracranial complications of sinusitis in adolescence. Single institute experience and review of the literature. Br J Neurosurg. 2007; 21(6):603-609. 50. Legg NJ, Gupta PC, Scott DF: Epilepsy following cerebral abscess: a clinical and EEG study of 70 patients. Brain 1973; 96: 259-268. 51. Leys D, Lesoin F, Viaud C, et al: Decreased morbidity from acute bacterial spinal epidural abscess using computed tomography and nonsurgical treatment in selected patients. Ann Neurol 1985; 17: 350-355. 52. Levy RM, Bredesen DE, Rosenblum ML: Neurological manifestations of the acquired immunodeficiency syndrome (AIDS): Experience at UCSF and review of the literature. J. Neurosurg 1985; 62: 475-495. 53. Longatti P, Perin A, Ettore F, Fiorindi A, Baratto V: Endoscopic treatment of brain abscesses. Childs Nerv Syst. 2006; 22: 1447-1450. 54. Mampalam TJ, Rosegay H, Andrews BT, et al: Nonoperative treatment of spinal epidural infections. J. Neurosurg 1989;71: 208-210. 55. McClelland S 3 , Hall WA: Postoperative central nervous system infection: incidence and associated factors in 2111 neurosurgical procedures. Clin Infect Dis. 2007;45: 1248 56. Monferrer Guardiola R, Bonig Trigueros I, Albert Coll M, Marco Lattur JM: Spinal epidural abscess with spondylitis. Case report. An Med Interna. 2007; 24:459-460. 57. Moussa AH, Dawson BH: Computed tomography and morbidity in brain abscess. Surgical Neurol 1978; 10:301-304. 58. Nadvi SS, Nathoo N, van Dellen JR: Lumbar puncture is dangerous in patiens with brain abscess or subdural empyema. S Afr Med J. 2000;90:609-610. 59. Nathoo N, van Dellen JR, Nadvi SS: Conservative neurological management of intracranial epidural abscesses in children. Neurosurgery.2004;55:263-264. rd

1378 Parasitosis and infections 60. Nathoo N, Nadvi SS, van Dellen JR, Gouws E: Intracranial subdural empyemas in the era of computed tomography: a review of 699 cases. Neurosurgery. 1999;44:529-535. 61. Nathoo N, Nadvi SS, van Dellen JR: Cranial extradural empyema in the era of computed tomography: a review of 82 cases. Neurosurgery 1999; 44:748-753. 62. Nielsen H, Gyldensted C, Harmen A: Cerebral Abscess. Aetiology and pathogenesis, symptoms, diagnosis and treatment. A review of 200 cases from 1935-1976. Acta Neurol Scand 1982;65:609-622. 63. Ohaegbulam SC, Saddeegi NU: Experience with brain abscess treated by simple aspiration. Surg Neurol 1980;13:289-291. 64. Osborn MK, Steinberg JP: Subdural empyema and other suppurative complications of paranasal sinusitis. Lancet Infect Dis. 2007; 7: 62-67. 65. Papanagiotou P, Grunwald IQ, Politi M, Reith WJ: Cerebral abscess due to sinusitis. Arch Neurol. 2008;65:668-669. 66. Ravilovitch MA, Spallone A: Spinal epidural abscess. Surgical and parasurgical management. Eur Neurol 1982; 21:347-357. 67. Rosenblum ML, Hoff JT, Norman D, et al: Nonoperative treatment of brain abscess in selected high-risk patients. J Neurosurg 1980;52:217-225. 68. Russel NA, Vaughan R, Morley TP: Spinal epidural infection. Can J Neurol Sci 1979;6:325-328. 69. Tunkel A, Wispelwey B, Scheld W: Brain abscess. IN: Mandell G, Bennett J, Dolin R (eds.). Principles and practice of infectious diseases. Philadelphia: Churchill Livingstone; 2000:1016-1027. 70. Venkatesh MS, Pandey P, Devi BI, Khanapure K, Satish S, Sampath S, Chandramouli BA, Sastry KV: Pediatric infratentorial subdural empyema: analysis of 14 cases. J Neurosurg. 2006; 105:370-377. 71. Wu TJ, Chiu NC, Huang FY: Subdural empyema in children—20-year experience in a medical center. J Microbiol Immunol Infect. 2008;41:62-67. 72. Yadav RK, Agarwal S, Saini J: Profile of compressive myelopathy as evaluated by magnetic resonance imaging. J Indian Med Assoc. 2008;106:79-82. 73. Yang B, Jin HM, Sun LP, Cai W, Shi CR: Posterior fossa abscesses secondary to dermal sinus associated with dermoid cyst in children. Neuropediatrics.2008;39:39-42. 74. Yang SY: Brain abscess: a review of 400 cases. J Neurosurg 1981; 55:794-799 75. Ziai WC, Lewin JJ 3 : Update in the diagnosis and management of central nervous system infections. Neurol Clin. 2008;26:427-468. rd

1379

Neurocysticercosis VEDANTAM RAJSHEKHAR Department of Neurological Sciences Christian Medical College Vellore, India Key words: neurocysticercosis (NCC), Taenia Solium, cyst, cysticercotic encephalitis

Introduction Cysticercosis, which is caused by larval form of cestode Taenia Solium, is endemic in several underdeveloped regions of the world such as Latin America, Asia and subSaharan Africa. Factors such as poor sanitation and open defecation combined with free roaming pigs are responsible for the presence and spread of the disease. Infection of the brain and spinal cord is referred to as neurocysticercosis (NCC). NCC is the commonest parasitic infection of the central nervous system. It is estimated that worldwide 50 million individuals suffer from the disease and it results in 50,000 deaths annually. Epilepsy is the commonest manifestation of NCC. As the disease does not cause epidemics and most often results in chronic morbidity in several people around the world, it remains one of the neglected diseases. Man is the only known definitive host harboring the adult worm and pig is the intermediate host harboring the larval stage of the disease or cysticercus cellulosae. Man becomes an accidental intermediate host on consumption of food or water contaminated by eggs shed by a taenia carrier.

Epidemiology NCC is highly prevalent in Latin America, Sub-Saharan Africa and Asia. It is infrequently seen in Muslim countries of the Middle East and North Africa. However, patients with NCC are being reported from all over the world including developed countries such as USA and Japan due to increased travel and immigration of people from endemic regions. There is therefore, a need for clinicians to have some knowledge of this disease irrespective of the region where they practice. NCC was recognized as a major cause of seizures in Latin American populations and clinicians there were at the forefront of research studies on this disease. Therefore, most of the epidemiological data has emanated from countries such as Mexico, Peru, Ecuador and Brazil. In most other endemic countries, epidemiological data is only being collected in recent years. Epidemiological studies on NCC are difficult to perform as the diagnosis of the disease is based on the availability of expensive imaging tools such as computed tomography (CT). Even serological tests for the disease are not freely available. NCC is the cause focal seizures in up to 50% of patients in some Indian hospitals. We

1380 Parasitosis and infections recently showed that NCC was a major cause of active epilepsy (AE) in a population based CT study. It was responsible for the epilepsy in nearly a third of the patients. The prevalence of NCC as a cause of AE was 1 per 1000 population. Therefore, in India there are at least 1 million patients with AE due to NCC.

Life cycle of Taenia Solium Taenia solium causes two forms of disease in humans depending on whether man is the definitive or intermediate host. When man is the definitive host, harboring the adult tapeworm in the intestine, he is said to be suffering from taeniasis. When man harbors the larval form (cysticercus cellulosae) in the brain, subcutaneous tissues, eyes and muscles, the disease is termed cysticercosis. Only consumers of pork can get taeniasis whereas even vegetarians can infected by the larval form through consumption of food and water contaminated by the ova of the worm shed by the taenia carrier. Taenia carriers can also get cysticercosis through the feco-oral route, if they do not practice hand washing after defecation.

Pathology The ova consumed by man enter the circulation as larvae. These larvae can lodge in different organs but they selectively thrive in the brain, subcutaneous tissues, eyes and muscles. In the brain parenchyma the larva undergoes degeneration, which provokes an inflammatory response from the host’s immune system. The cyst goes through four stages; live (vesicular), colloidal, granular-nodular and calcific (end stage). Live cysts in the parenchyma rarely cause symptoms. Symptoms are usually associated with the degeneration of the cyst and the inflammation caused by the degeneration. Even the calcific stage causes symptoms due to the associated epileptogenic scar tissue around it. Besides the brain parenchyma, the larvae can also lodge in the ventricles or subarachnoid spaces where they usually persist as live forms for long periods. They can assume large sizes and cause obstruction of the CSF pathways and produce hydrocephalus. The cysts in the subarachnoid space do not have scolices and are referred to as “cysticercus racemosus”. The cysts in the CSF spaces also undergo degeneration and produce either ependymitis or arachnoiditis and vasculitis leading to cranial neuropathies and strokes.

Clinical features The clinical presentation of a patient with NCC does not point to the diagnosis of the disease. Clinical features depend on the location of the cysts. Parenchymal cysts are the commonest and they usually present with seizures. Nearly 65% to 80% of patients with the disease have seizures. Patients most often have partial seizures with or without secondary generalization. Other types of seizures can also occur. The other common presentations of parenchymal cysts include focal deficits, raised intracranial pressure due to a single large cyst or several granulomas with surrounding edema (cysticercotic encephalitis). Occasionally, patients with NCC may present with psychiatric

Neurocysticercosis

1381

manifestations. A form of the disease initially recognized and described from India is the solitary cysticercus granuloma (SCG)(Figure 1). This form of the disease is the commonest type of NCC seen in >60% of Indian patients with NCC. Biopsy on a series of solitary small brain lesions, in patients with seizures, which were earlier diagnosed as “microtuberculomas” or “disappearing” lesions, led to the recognition of the entity of SCG. While most patients with SCG present with seizures, about 5% present with severe episodic headache. Rarely they can present as brain stem masses. Cysts in the lateral, third or fourth ventricles cause hydrocephalus and present with features of raised intracranial pressure. Patients with racemose cysts in the basal cisterns can have a “stroke-like” presentation due to arteritis of the vessels in the subarachnoid spaces. They can also present with multiple cranial nerve palsies due to ischemia and strangulation of the nerves by the inflammatory exudates. Finally, the cysts can cause features of raised intracranial pressure due to obstruction of the basal cisterns or the outlet of the fourth ventricle producing hydrocephalus.

Diagnostic tests Diagnosis of NCC is based on imaging and serological tests. Till the introduction of CT scan, only calcified granulomas could be recognized as a sign of NCC. Ventriculograms could identify intraventricular cysts as filling defects. CT and more recently magnetic resonance imaging (MRI) has markedly enhanced our ability to diagnose NCC. However, in most situations, even with these tools, a definitive diagnosis of NCC is elusive. Parenchymal live cysts appear as non-enhancing hypodense or hypointense rounded lesions without surrounding edema (Figure 2). A scolex may be identified in some cysts as a hyperdense dot on CT or a hyperintense or hypointense dot on MRI (Figure 3). The colloidal and granular-nodular stages of the parenchymal cysts show enhancement of the wall and surrounding edema. Even these stages might reveal the scolex. This diagnostic image is characteristic of the diagnosis of NCC. The calcific stage is revealed as a calcific dot, which may or may not enhance and usually does not have edema around it (Figure 4). However, MR might show reveal enhancement in some calcific lesions and there might edema associated with some of them. In a patient with multiple

Fig. 1 Live parenchymal cysticercus cysts appearing as nonenhancing hypodense rounded lesions with no surrounding edema.

1382 Parasitosis and infections

Fig. 2 cysticercus granuloma on a contrast enhanced CT scan appearing as a ring enhancing lesion. Note the edema around the granuloma.

Fig. 3 Cysticercus cyst in the posterior third ventricle causing hydrocephalus.

Fig. 4 a and b. a. Racemose cysticercus cyst in the ambient and quadrigeminal cisterns. b. Racemose cysticercus cyst in the left sylvian fissure.

Fig. 5 Sagittal gadolinium enhanced MR showing a cysticercus cyst in the fourth ventricle with the scolex seen as a hyperintense dot in the superior part of the cyst.

Neurocysticercosis

1383

cysticercal lesions, all the four stages of the cyst may be seen indicating either exposure to the disease at different time periods or different rates of involution of the cysts (Figure 5). CT scan will reveal hydrocephalus although the cyst or cysts within the ventricles are difficult to discern as they have the same density as CSF. A CT ventriculogram might be necessary to reveal the filling defects due to the cysticercus cysts within the ventricle. MRI using 3D CISS (constructive interference steady state) sequences might distinguish the cysts from the CSF in the ventricles (Figure 6). Occasionally, the cyst wall might enhance following the injection of a contrast agent indicating the presence of ependymitis. Cysts in the subarachnoid spaces are seen as non-enhancing lesions, which widen the subarachnoid spaces especially in the basal cisterns such as the ambient and interpeduncular cisterns (Figure 7). These are best revealed on MRI. There might be associated hydrocephalus. Presence of infarcts in the brain might also be evident. Except for the presence of a scolex, there are no imaging features to categorically diagnose NCC. Several other diseases can mimic NCC on CT and MRI. For parenchymal cysts the differential diagnosis would include a low-grade cystic glioma or a hydatid cyst, brain abscess, metastasis and tuberculoma. Brain calcifications are seen with other infections such as tuberculosis, toxoplasmosis and cytomegalovirus (CMV). Epidermoid tumours may mimic subarachnoid cysticercal cysts.

Fig. 6 Calcified granuloma on the CT scan of a patient presenting with seizures. Note the lack of edema around the lesion.

Fig. 7 Gadolinium enhanced MR image showing all the different phases of parenchymal cysticercus cysts.

1384 Parasitosis and infections

Fig. 8

Immunological tests are used to detect antibodies against cysticercal antigens in the serum or CSF. Earlier the enzyme-linked immunosorbent assay (ELISA) was used but this test had many false positive due to cross reactions. In 1989, Centers for Disease Control (CDC), USA introduced the enzyme-linked immunoelectrotransfer blot (EITB) which was found to be more specific and also more sensitive than ELISA for the diagnosis of NCC. While the EITB gives a positive result in over 90% of patients with multiple cysticercal lesions in the brain, its sensitivity in patients with a SCG is only around 50 to 60%. Patients with calcific lesions alone are also unlikely to be positive on the EITB. Hence, a negative EITB does not eliminate the diagnosis of NCC. The specificity of EITB is however very high approaching 100%. Therefore, in a patient who has clinical and radiological features of NCC, a positive EITB indicates a high likelihood of NCC. However, the test is not readily available in most endemic countries and even if available its cost is prohibitive for most poor patients.

Diagnostic criteria Since the diagnosis of NCC is not secured in most patients with a single clinical, radiological or immunological test, a set of diagnostic criteria is required to arrive at the diagnosis. Such criteria were evolved for SCG and for NCC. The diagnosis of SCG is based on diagnostic criteria evolved by us (Table 1). These criteria have been validated in prospective studies and have a sensitivity and specificity of over 99% in a region endemic for NCC. The diagnostic criteria for NCC include absolute, major, minor and epidemiological criteria and on the basis of these criteria one could diagnose a patient suspected to have NCC as either having definite or probable NCC (Table 2).

Treatment Most patients with NCC can be treated medically and do not require surgery. The treatment is usually symptomatic but specific therapy for the cysts (cysticidal drugs) has been available in the form of praziquantel or albendazole since the late 1970s.

Neurocysticercosis Table 1

Table 2

1385

1386 Parasitosis and infections

i. Symptomatic therapy Anti-epileptic drugs (AEDs) are probably the most commonly prescribed drugs for patients with NCC considering the fact that most of them present with seizures. Monotherapy has been found to control seizures in over 80% of patients with SCG. In patients with SCG, there is evidence to support early withdrawal of AEDs soon (within 3 months) after the resolution of the granuloma is documented on the CT or MR provided the patient has not had a seizure in the 3 months prior to the resolution. In patients with multi-lesional NCC, however, most will require AEDs for several years if not life long. Prior to the introduction of cysticidal therapy, steroid therapy was the mainstay of treatment of NCC. Steroids reduce the inflammatory response around degenerating cysts and granulomas and thereby reduce the symptoms of the disease. They should be generally administered along with cysticidal drugs to reduce the adverse effects produced by the rapid degeneration of the cysts. Both dexamethasone and prednisolone have been used. Dexamethasone is prescribed in doses of 8 to 16 mg per day orally and prednisolone in doses of 40 to 60 mg/day orally. The therapy should be for a short period of a few days to a less than 2 weeks. Steroid therapy is often the mainstay of therapy for patients with cysticercotic encephalitis. Antiedema drugs such as mannitol, frusemide and oral glycerol may be required for short periods of time in patients with severely elevated intracranial pressure due to edema surrounding a a large number of degenerating cysts.

ii. Cysticidal therapy The natural history of the larval cysts within the brain leads to the death and ultimate resolution of the cysts from the brain. Some cysts, however, degenerate leaving a calcific residue. The risk factors for calcification of a cyst are unclear. The interval between infestation of the brain and the ultimate resolution of the cysticercal cysts are very variable. In some patients the duration might be as short as a few months and in others the process could take several years. Because of the feature of spontaneous resolution of parenchymal cysts and the variability in the rate of resolution of cysts, cysticidal drug therapy has been surrounded by controversy. It is well accepted that these drugs hasten the degeneration of live cysts in the brain but what is not clear is whether early degeneration leads to any clinical benefits to the patient. It is argued that use of cysticidal drugs might on the other hand lead to an exaggerated scar formation, which in turn could lead to an aggravation of seizures. This debate on the use of cysticidal drugs for NCC is unresolved. Albendazole is preferred over praziquantel because of its easy availability and lower cost. Albendazole also has better penetration into the CSF and its serum levels are not lowered with concomitant administration of steriods unlike praziquantel whose serum levels are lowered with steroid administration. There is consensus that cysticidal drugs are not needed for calcific lesions and is contraindicated in patients with cysticercotic encephalitis. Cysticidal drugs are useful in the management of large parenchymal live cysts and racemose cysts in the subarachnoid

Neurocysticercosis

1387

spaces. Although albendazole and praziquantel have been used successfully in patients with intraventricular cysts, surgery provides faster relief of symptoms and is a safer alternative to drugs. Albendazole is used in a dose of 15mg/kg body weight in two divided doses daily for anywhere between 8 days and 30 days. Its main side effects are related to the edema aournd the degenerating cysts and mild gastrointestinal effects.

iii. Surgery Surgery is uncommonly used in patients with NCC. Patients with intraventricular cysts causing hydrocephalus and large parenchymal cysts are generally offered surgery to provide instant relief of symptoms of raised intracranial pressure. For patients with intraventricular cysts, endoscopic surgery provides a minimally invasive technique for the Table 3

1388 Parasitosis and infections excision of the cysts. Surgery is also needed for patients with hydrocephalus due to fourth ventricular outlet obstruction or communicating hydrocephalus in the form of a ventriculo-peritoneal shunt. Besides the conditions mentioned above, surgery is indicated to obtain the diagnosis in a patient with a cysticercal lesion with an atypical clinical presentation such as spinal intramedullary mass or as a brain lesion in whom the diagnosis is uncertain. Occasionally, SCG can enlarge and mimic a tuberculoma. Histological diagnosis might be required to ascertain the diagnosis in such patients. Table 3 outlines the consensus statement from a group of experts regarding the management of various forms of NCC. Ultimately, these guidelines need to be individualized for a given patient and hence, may need modification in a particular situation based on the clinical features and availability of facilities.

Prognosis Of all the different manifestations of NCC, patients with SCG and possibly those with a single intraventricular cyst have the best prognosis. Over 80% of patients with SCG have no recurrence of seizures following withdrawal of AEDs provided the granuloma has resolved without a calcific residue. However, about 15% of patients with SCG may have recurrence of seizures and those at risk for recurrent seizures are those who have had > 2 seizures, patients with breakthrough seizures during the treatment and those with residual calcification in the CT scan. In patients with multilesional NCC, AEDs can only be withdrawn in 25 cmH2O and normal biochemical and cytological composition of CSF • No other explanation for the raised intracranial pressure In a 2002 review, Friedman and Jacobson propose an alternative set of criteria, derived from Smith's. These require the absence of symptoms that could not be explained by a diagnosis of IIH, but do not require the actual presence of any symptoms (such as headache) attributable to IIH. These criteria also require that the lumbar puncture is performed with patient lying sideways, as a lumbar puncture performed in the upright sitting position can lead to artificially high pressure measurements. Friedman and Jacobson also do not insist on MR venography for every patient; rather, this is only required in atypical cases.

Diagnostic workup Imaging Studies • Neuroimaging ° A patient with bilateral disc swelling should undergo urgent neuroimaging studies to rule out an intracranial mass or a dural sinus thrombosis. ° Although CT is certainly adequate in most instances, MRI and magnetic resonance venography are effective in ruling out both a mass lesion and a potential dural sinus thrombosis. ° In the setting of idiopathic intracranial hypertension, the findings on neuroimaging studies either are normal or demonstrate small slit-like ventricles, enlarged optic nerve sheaths, and occasionally an empty sella. • Ultrasonography ° Standardized A-scan orbital ultrasonography precisely measures the diameter of the optic nerve sheath. ° If this diameter increases in primary gaze and diminishes by 25% in eccentric gaze (30° test), then increased subarachnoid fluid surrounding the optic nerve is presumably present. This finding is consistent with papilledema if it is bilateral. ° The drawback of this noninvasive technique is that it requires a highly skilled clinician to obtain reproducible results.

Diagnostic Procedures • Lumbar puncture ° o Once an intracranial mass lesion is ruled out, a lumbar puncture is indicated. The opening pressure should be measured with the patient relaxed to avoid a falsely elevated pressure reading. ° The clinician performing the procedure must indicate to the ophthalmologist

1434 Miscel Ianeous if any specific difficulty was encountered that may have falsely elevated the pressure reading. ° Unfortunately, some patients demonstrate a transiently normal pressure despite their harboring idiopathic intracranial hypertension. Confirming the disease in these patients is difficult. ° Besides the value of the opening pressure, the clarity and the color of the cerebrospinal fluid should be noted. In addition, the cerebrospinal fluid should be forwarded for assessment of the cell count, cytology, culture, glucose, protein, and electrolyte concentration. All of these findings are normal in patients with idiopathic intracranial hypertension.

Treatment Treatment for patient with IIH can be divided into medical treatment and surgical treatment. The cornerstone of medical treatment is weight loss. It does not appear to be the total number of pounds lost. Some patients are effectively treated by losing one pound every week or two for several months and then maintaining the weight loss. It may be the loss of fluid accompanying weight loss that is the significant factor but this has not been proven. The treatment goal for patients is to preserve optic nerve function while managing their increased intracranial pressure. Therefore, optic nerve function should be carefully monitored with an assessment of visual acuity, color vision, optic nerve head observation, and perimetry.

Medical treatment The medical management is multifaceted and consists of the following: ° Weight control for patients who are overweight Most patients with this disorder are females who are overweight. Weight loss is a cornerstone in the management of these patients. Unfortunately, weight reduction generally proves to be a difficult task for these patients. As little as a 6% weight loss has been demonstrated to result in a reduction of the intracranial pressure with the accompanying resolution of papilledema. To formalize the process of weight reduction, referral to a dietitian may be appropriate. Treatment of related underlying diseases ° Cessation of exogenous agents related to increased intracranial pressure ° ° Use of diuretics to control the intracranial pressure To protect the optic nerve function, the intracranial pressure must be lowered. Acetazolamide (Diamox) appears to be the most effective drug in lowering the intracranial pressure. The initial dose should be 1 g/d. Although for compliance purposes, the 500 mg sequel taken orally ■

■

■

■

■

Idiopathic Intracranial Hypertension (Pseudotumor Cerebri)

1435

twice a day is preferred; This dose can be increased to 2 g/d, although most patients do not tolerate the troubling adverse effects (e.g., extremity paresthesias, fatigue, metallic taste when drinking carbonated beverages, decreased libido) of this medication at this high dose. In the event of intolerance to acetazolamide, a loop diuretic like furosemide may be used as a replacement diuretic in this group. Unfortunately, furosemide does not appear to be as effective as acetazolamide. Corticosteroids ° Corticosteroids are effective in lowering the intracranial pressure in those patients with an inflammatory etiology for their idiopathic intracranial hypertension. In addition, steroids may be used as a supplement to acetazolamide to hasten recovery in patients who present with severe papilledema. Because of the significant adverse effects, corticosteroids should not be considered as a long-term solution for these patients. ■

■

■

■

Surgical Therapy Patients with idiopathic intracranial hypertension should be closely monitored while on medical treatment. The frequency of visits is determined by the initial state of the patient's visual function and the response to medical treatment. Despite close follow-up care and maximum medical treatment, some patients experience deterioration of their visual function. In this situation, surgical intervention should be considered. Two procedures that can be performed are optic nerve sheath fenestration or a cerebrospinal fluid diversion procedure (ie, lumboperitoneal shunt, ventriculoperitoneal shunt). Treatment of this disorder by repeated lumbar punctures is considered to be of historic interest. • Optic nerve sheath fenestration ° Optic nerve sheath fenestration has been demonstrated to result in the reversal of optic nerve edema with some recovery of optic nerve function. The approach to the optic nerve may be from the medial or lateral aspect of the orbit; each technique has its benefits and drawbacks. ° Occasionally, a bilateral curative effect of the papilledema occurs from unilateral surgery. However, if this is not the case, then the opposite nerve must undergo the same procedure. ° Although the intracranial pressure remains elevated in these patients postoperatively, the local filtering effect of the fenestration acts as a safety valve and eliminates the pressure from being transmitted to the optic nerve. ° Complications related to this procedure include diplopia, optic nerve injury, vascular occlusion, a tonic pupil, and the inherent risk of hemorrhage and infection with intraconal surgery. ° Unfortunately, the long-term success rate of this operation may be only 16%. • Cerebrospinal fluid diversion procedures (ie, lumboperitoneal shunt, ventriculoperitoneal shunt)

1436 Miscel Ianeous ° These two neurosurgical interventions are highly effective in lowering the intracranial pressure. In some facilities, they remain the procedures of choice for treating patients with idiopathic intracranial hypertension who do not respond to maximum medical treatment. ° Shunts are also indicated in the following: patients with intractable headaches, regions where no access is available to a surgeon who is comfortable with optic nerve sheath fenestration, and patients with a failed optic nerve sheath fenestration. • Venous sinus stenting ° Focal stenotic lesions in the lateral sinuses obstructing cranial venous outflow can be found rather often in patients with IIH and overall, the importance of venous sinus disease in the etiology of IIH is probably underestimated. Lateral sinus stenting shows promise as an alternative treatment to neurosurgical intervention in intractable cases.

Follow-up • In patients with IIH, visual acuity and fields should be monitored by the appropriate specialist. • The frequency of the follow-up visits is determined by a number of factors, to include the following: ° Initial visual function of the patient ° Underlying disease causing increased intracranial pressure ° Perceived compliance of the patient with respect to medical therapy • Once the initial diagnosis has been established, investigations have been performed, and the therapy has been initiated, the patient can be observed every 3-4 weeks. However, patients who present with a significant visual function deficit or marked papilledema should be monitored daily for a week until they demonstrate some improvement and subsequent stability in their visual function. The clinician should be prepared to titrate the patient's treatment to the status of the visual function and should not hesitate to refer the patient for surgical treatment (optic nerve sheath fenestration or a neurosurgical shunting procedure) in the absence of stabilization of the visual function. • During follow-up visits, the best-corrected visual acuity for distant and near vision, color vision (using pseudoisochromatic plates), static perimetry, and optic nerve appearance (including the status of spontaneous venous pulsations) should be recorded. Patients who do not perform well on static perimetry testing may be better followed with kinetic perimetry testing. The spontaneous pulsation of large retinal veins generally indicates a normal intracranial pressure. If the patient continues to remark on the persistence of a significant headache despite the presence of spontaneous venous pulsations, evaluating a source other than idiopathic intracranial hypertension for the headache is important. • When a patient appears to have stabilized with respect to visual function and treatment, follow-up visits can extend to once every 2-4 months.

Idiopathic Intracranial Hypertension (Pseudotumor Cerebri)

1437

Complications • The main complication of this disorder is progressive optic neuropathy. Despite timely treatment, some patients develop an optic neuropathy related to the optic nerve edema. • Generally, this dysfunction presents in a progressive fashion with constriction of the peripheral visual field; worsening nerve fiber bundle visual field defects; a decrease of color vision; and, in end-stage disease, a drop in the central visual function. • Occasionally, a patient may develop an acute loss of vision due to ischemic optic neuropathy or a retinal vascular occlusion associated with the papilledema.

Outcome and Prognosis • The visual prognosis in timely and appropriately treated patients can be encouraging in cases of idiopathic intracranial hypertension. • Unfortunately, the incidence of visual loss has been reported to be significant in some studies of this disease. Corbett et al documented visual dysfunction in close to one half of patients with idiopathic intracranial hypertension.3 • Since the increase in intracranial pressure tends to be chronic in nature, all patients with this disorder must be monitored for years after presentation. If necessary, medical treatment should be continued on a long-term basis.

Patient Education • Informing patients who are overweight that weight control is a long-term factor in idiopathic intracranial hypertension is important. Asking patients about their weight loss at the beginning of each visit reinforces this concept. In addition, it may be worthwhile to mention that the loss of as little as 6% of body weight may lead to the termination of this disorder and also may significantly diminish the risk of its recurrence. • Although the disease may appear to be self-limiting, it is considered to be a chronic disorder; therefore, once the medication is tapered off, patients should be alerted to return to an ophthalmologist if symptoms of increased intracranial pressure recur. • If a particular agent, such as tetracycline, is associated with the rise in intracranial pressure, the patient should be educated to avoid this agent.

1438 Miscel Ianeous

grade 1 papilledema

grade 2 papilledema

grade 3 papilledema

Idiopathic Intracranial Hypertension (Pseudotumor Cerebri)

1439

Flow chart for treatment of Idiopathic Intracranial Hypertension

REFERENCES 1. Acheson JF (2006). Idiopathic intracranial hypertension and visual function. Br. Med. Bull. 79-80: 233–44. 2. Binder DK, Horton JC, Lawton MT, McDermott MW (March 2004). Idiopathic intracranial hypertension. Neurosurgery 54 (3): 538–51; discussion 551–2. 3. Brazis PW, Lee AG. Elevated intracranial pressure and pseudotumor cerebri. Curr Opin Ophthalmol. Dec 1998;9(6):27-32. 4. Brazis PW. Clinical review: the surgical treatment of idiopathic pseudotumour cerebri (idiopathic intracranial hypertension). Cephalalgia. 2008 Dec;28(12):1361-73. 5. Corbett JJ, Savino PJ, Thompson HS, Kansu T, Schatz NJ, Orr LS, et al. Visual loss in pseudotumor cerebri. Follow-up of 57 patients from five to 41 years and a profile of 14 patients with permanent severe visual loss. Arch Neurol. Aug 1982;39(8):461-74. 6. Corbett JJ, Thompson HS. The rational management of idiopathic intracranial hypertension. Arch. Neurol. Oct 1989; 46 (10): 1049–51. 7. Corbett JJ. Increased intracranial pressure: idiopathic and otherwise. J Neuroophthalmol. Jun 2004;24(2):103-5. 8. Dandy WE. Intracranial pressure without brain tumor - diagnosis and treatment. Ann. Surg. Oct 1937; 106 (4): 492–513. 9. Daniels AB, Liu GT, Volpe NJ, Galetta SL, Moster ML, Newman NJ, et al. Profiles of obesity, weight gain, and quality of life in idiopathic intracranial hypertension (pseudotumor cerebri). Am J Ophthalmol. Apr 2007;143(4):635-41. 10. Digre KB, Corbett JJ. Idiopathic intracranial hypertension (pseudotumor cerebri): A reappraisal. Neurologist 2000; 7: 2–67. 11. Friedman DI, Jacobson DM. Diagnostic criteria for idiopathic intracranial hypertension.

1440 Miscel Ianeous Neurology 2002; 59 (10): 1492–1495 12. Friedman DI, Jacobson DM. Idiopathic intracranial hypertension. J Neuroophthalmol. Jun 2004;24(2):138-45. 13. Higgins JN, Tipper G, Varley M, Pickard JD. Transverse sinus stenoses in benign intracranial hypertension demonstrated on CT venography. Br J Neurosurg. 2005 Apr;19(2):137-40. 14. Higgins JN, Cousins C, Owler BK, Sarkies N, Pickard JD. Idiopathic intracranial hypertension: 12 cases treated by venous sinus stenting. J Neurol Neurosurg Psychiatry. 2003 Dec;74(12):1662-6. 15. Higgins JN, Owler BK, Cousins C, Pickard JD. Venous sinus stenting for refractory benign intracranial hypertension. Lancet. 2002 Jan 19; 359 (9302):228-30. 16. Johnson LN, Krohel GB, Madsen RW, March GA Jr. The role of weight loss and acetazolamide in the treatment of idiopathic intracranial hypertension (pseudotumor cerebri). Ophthalmology. Dec 1998;105(12):2313-7. 17. Lin A, Foroozan R, Danesh-Meyer HV, De Salvo G, Savino PJ, Sergott RC. Occurrence of cerebral venous sinus thrombosis in patients with presumed idiopathic intracranial hypertension. Ophthalmology. Dec 2006;113(12):2281-4. 18. Miller NR, Newman NJ. Pseudotumor cerebri (benign intracranial hypertension). In: Walsh and Hoyt's Clinical Neuro-Ophthalmology. Vol 1. 5th ed. 1999:523-38. 19. Owler BK, Parker G, Halmagyi GM, Johnston IH, Besser M, Pickard JD, Higgins JN. Cranial venous outflow obstruction and pseudotumor Cerebri syndrome. Adv Tech Stand Neurosurg. 2005;30:107-74. 20. Pickard JD, Czosnyka Z, Czosnyka M, Owler B, Higgins JN. Coupling of sagittal sinus pressure and cerebrospinal fluid pressure in idiopathic intracranial hypertension--a preliminary report. Acta Neurochir Suppl. 2008; 102:283-5. 21. Skau M, Brennum J, Gjerris F, Jensen R. What is new about idiopathic intracranial hypertension? An updated review of mechanism and treatment. Cephalalgia. Apr 2006;26(4):384-99. 22. Smith JL. Whence pseudotumor cerebri?. J. Clin. Neuroophthalmol. (1985) 5 (1): 55–6. 23. Spoor TC, McHenry JG. Long-term effectiveness of optic nerve sheath decompression for pseudotumor cerebri. Arch Ophthalmol. May 1993;111(5):632-5.

1441

Pathophysiology and Treatment of Hydrocephalus J. ANDRÉ GROTENHUIS Department of Neurosurgery, University Medical Center St. Radboud, Reinier Postlaan 4, 6525GC Nijmegen, The Netherlands Key words: hydrocephalus, raised ICP, CSF circulation, endoscopicthird ventriculostomy (ETV) ventriculopreritoneal shunt, ventriculopleural shunt, ventriculoatrial shunt

Introduction Although hydrocephalus was already described in ancient times by Hippocrates, it could not be treated effectively until the mid 20th century, when the development of appropriate shunting materials and techniques occurred. Before that, tapping the ventricles was the only remedy and it was always in vain. At the beginning of the 20th century, after CSF dynamics had been elaborated, attempts were also made to remove the choroid plexus, because it was then known that it produces most of the cerebrospinal fluid (CSF). Interestingly, in that same period, surgeons already introduced scopes into the ventricular system in attempts to treat hydrocephalus. Today, the focus of hydrocephalus research is on pathophysiology, valve design in shunting, and minimally invasive techniques of treatment. Hydrocephalus should be considered as a progressive disease caused by the abnormal rise in CSF volume and, usually, pressure, that results from an imbalance of CSF production and absorption. Although the essentials of CSF dynamics have been described already at the end of the 19th century, not all details involving these dynamics in normal and in pathological circumstances are fully understood. The overall incidence of hydrocephalus is unknown. When cases of spina bifida are included, congenital hydrocephalus occurs in 2-5 births per 1000 births. Incidence of acquired types of hydrocephalus is unknown. The etiology of hydrocephalus in congenital cases is unknown. Very few cases (150 mg/dL). Obtain some idea of brain compliance in order to select the optimum valve pressure and decide if the pressure-programmable valve should be used. Use one dose of preoperative prophylactic antibiotics during induction of anesthesia.

Intraoperative Details • Endoscopic Third Ventriculostomy (ETV): Reserve this procedure for obstructive cases in patients who have normal or near-normal spinal fluid absorptive capacity. Use a blunt instrument to penetrate the floor of the third ventricle. Sharp instruments or lasers can cause vascular injury. Leaving a clamped drain in place postoperatively is still a matter of debate but might be prudent in some cases. The burr hole is placed just in front of the coronal suture which allows a straight trajectory to the foramen of Monro. Stereotactic guidance is not needed if endoscopic techniques are used and the ventricles are enlarged. Other indications to use neuroendoscopy in case of hydrocephalus include 1) dilating or stenting an obstructed aqueduct, 2) direct positioning of a proximal shunt catheter, 3) fenestration of intraventricular membranes, 4) opening of the septum pellucidum in unilateral obstruction of the foramen of Monro, 5) biopsy or excision of intraventricular tumours, 6) fenestration of intra- and paraventricular arachnoid cysts, and marsupialisation of neuro-epithelial cysts. But certainly indications are still evolving. • Ventriculoperitoneal shunting: This procedure is still by far the most common procedure for CSF diversion. The abdomen should be able to absorb the excess spinal fluid. Either 1 of 2 major locations for the burr holes are typically used. The ventricular catheter can be placed more reliably from the (right) frontal approach. Some surgeons still prefer parietooccipital catheters. The proximal catheter tip should lie anterior to the choroid plexus in the frontal horn of the lateral ventricle when the parietooccipital approach is used. In difficult cases, placement under neuronavigation guidance should be considered whenever available. • Ventriculoatrial shunting: This procedure is usually the first choice for patients who are unable to have distal abdominal catheters (eg, multiple operations, recent abdominal sepsis, known malabsorptive peritoneal cavity, abdominal pseudocyst ). The procedure carries more risk. Long-term complications are more serious (eg, renal failure, vena cava thrombosis). Fluoroscopic guidance is necessary to prevent catheter thrombosis (short distal catheter) or cardiac arrhythmias (long distal catheter). • Ventriculopleural shunting: Reserve this procedure for patients with failed peritoneal and atrial shunts. • Torkildsen shunts or internal shunts are straight tubes that communicate to

Pathophysiology and Treatment of Hydrocephalus

1445

cerebrospinal fluid spaces without a valve, usually from the occipital horn to the cistern magna. Their effectiveness and long-term efficacy are not proven. • Lumboperitoneal shunts are used in communicating hydrocephalus, especially if ventricles are small. Idiopathic intracranial hypertension (IIH) is the classical indication of this method of shunting. A positional valve is helpful because it turns off the flow of CSF when the patient is upright, thereby preventing overdrainage headache.

Contraindications Few cases of hydrocephalus should not be treated. Cases in which treatment should not be implemented include the following: • The patient in whom a successful surgery would not affect the outcome (eg, a child with hydranencephaly) • In ventriculomegaly of senescence, the patient who does not have the symptom triad • Ex vacuo hydrocephalus is merely the replacement of lost cerebral tissue with cerebrospinal fluid. Because no imbalance in fluid production and absorption exists, this technically is not hydrocephalus. • Arrested hydrocephalus is defined as a rare condition in which the neurologic status of the patient is stable in the presence of stable ventriculomegaly. The diagnosis must be made extremely carefully because children can present with very subtle neurological deterioration (eg, slipping school performance) that is difficult to document. • Benign hydrocephalus of infancy is found in neonates and young infants. The children are asymptomatic, and head growth is normal. CT scan shows mildly enlarged ventricles and subarachnoid spaces.

Postoperative care and follow-up In patients with high brain compliance, gradual assumption of the upright position and slow mobilization may reduce the incidence of early subdural hematoma formation. Plain radiographs of the entire hardware system confirm good position and serve as excellent baseline studies for the future. Postoperative CT scan is used to document ventricular size. Wounds should remain dry for at least 3 days postoperatively, until epithelialization has occurred. In patients with pleural shunts, perform an early postoperative chest radiograph to ensure adequate absorption of fluid. Large effusions can occur in short periods, and respiratory problems can ensue.

Follow-up • Remove stitches by 7-10 days postsurgery. • Perform CT scan for baseline at 2-4 weeks postsurgery after shunting.

1446 Miscel Ianeous • Perform MRI-scan to assess flow through the stoma for baseline at 8-12 weeks postsurgery in patients with third ventriculostomy. • Monitor all children with shunts and third ventriculostomy every 6-12 months. Carefully monitor head growth in infants. Check distal tubing length with plain radiographs when the child grows. Appropriate specialists should carefully assess child development. • What happens to ventricular size in patients who have a third ventriculostomy is not well known. Other methods of assessment of patency need to be used, such as MRI flow studies and clinical evaluations (eg, detailed funduscopic examinations).

Complications The most common complications differ depending on the kind of the procedure and in case of shunting on the type of shunt and the underlying pathophysiology. Bleeding is the most feared complication of ETV, although fortunately very rare. If it is due to damage to the basilar artery which underlies the floor of the third ventricle this is usually fatal. Venous bleeding from puncturing the ependyma or damaging the choroid plexus will eventually stop with prolonged rinsing but is can make the procedure impossible to proceed and when it occurs after the stoma has been made the chance is high that the stoma will close due to the bleeding. Other complications include damage to the hypothalamus and infundibulum (with memory deficit and hormonal disturbances), subdural hematoma and CSF leakage or pseudomeningocele formation. Infection is the most feared complication in the young age group after shunting. The overwhelming majority of infections occur within 6 months of the original procedure. Common infections are staphylococcal and propionibacterial. Early infections occur more frequently in neonates and are associated with more virulent bacteria such as Escherichia coli. Infected shunts need to be removed, the cerebrospinal fluid (CSF) needs to be sterilized, and a new shunt needs to be placed. Treatment of infected shunts with antibiotics alone is not recommended because bacteria can be suppressed for extended periods and resurface when antibiotics are stopped. Subdural hematomas occur almost exclusively in adults and children with completed head growth. Incidence of subdural hematomas can be reduced by slow postoperative mobilization and perhaps by avoiding rapid intraoperative ventricular decompression. This allows for brain compliance reduction. The treatment is drainage and may require temporary occlusion of the shunt. Shunt failure is mostly due to suboptimal proximal catheter placement. Occasionally, distal catheters fail. Suspect infection if the distal catheter is obstructed with debris. Abdominal pseudocysts are synonymous with low-grade shunt infection. Overdrainage is more common in lumboperitoneal shunts and manifests with headaches in the upright position. In most cases, overdrainage is a self-limiting process. However, revision to a higher-pressure valve or a different shunt system occasionally may be necessary. A positional valve that closes when the patient is upright is also available. Slit ventricle syndrome is a rare condition in which brain compliance is unusually low. It mostly occurs in the setting of prior ventriculitis or shunt infection. The patient may develop high pressures without ventricular dilatation. The slit ventricle syndrome

Pathophysiology and Treatment of Hydrocephalus

1447

does not imply overdrainage, and the symptoms usually are those of high pressure rather than low pressure. Most experts also agree that slit ventricles predispose the patient to a higher incidence of ventricular catheter failure. Repeated ventricular blockage by the coapted ventricular wall may be helped by performing a subtemporal decompression that creates an artificial pressure reservoir and induces slight reenlargement of the slit ventricle. ETV also has been described as a treatment for slitventricles but it is technically much more difficult because of the small size of the ventricles.

Outcome and Prognosis In general, outcome is good. A typical patient should return to baseline after shunting, unless prolonged elevated intracranial pressure or brain herniation has occurred. The neurologic function of children is optimized with shunting. Infection, especially if repeated, may affect cognitive status. The best long-term results in the most carefully selected patients are no better than 60% in normal pressure hydrocephalus. Few complete recoveries occur. Often, gait and incontinence respond to shunting, but dementia responds less frequently. Often, various other neurologic abnormalities associated with hydrocephalus are the limiting factor in patient recovery. Examples are migrational abnormalities and postinfectious hydrocephalus.

Future and Controversies Hydrocephalus research and treatment have advanced tremendously in the last 20 years. Examples are the development of new shunt materials and, more recently, programmable and gravitational valve technology. Current research categories include the following: • Transplantation of tissue, such as vascularized omentum, to reestablish normal cerebrospinal fluid (CSF) could be the best method to treat communicating hydrocephalus. • Endoscopic third ventriculostomy have eliminate the need for shunting in noncommunicating cases of hydrocephalus in older children and adults. New optics and smaller scopes have expanded this field over the last 10 years. But its role in infants with obstructing hydrocephalus is not yet solved (an multi-center international study is currently under way to help to solve this controversy). • The heterogeneous nature of hydrocephalus has hampered our understanding of the molecular basis of the disease. However, unraveling the molecular basis by disease gene identification opens new fields of study of hydrocephalus. Characterization of multiple transgenic mouse models has highlighted the importance of the secretory ependymal cells of the subcommissural organ (SCO) as a key factor in development of congenital hydrocephalus and many more areas (like the identification of a hormone secreted in this area, the SCO-spondin) are now under research.

1448 Miscel Ianeous

MRI scan with normal sized ventricular system

MRI scan of enlarged ventricular system in a case of hydrocephalus

Pathophysiology and Treatment of Hydrocephalus

Ventriculoperitoneal shunt

Ventriculo-atrial shunt

Three different approaches for the ventricular catheter of a shunt

1449

Lumbo-peritoneal shunt

1450 Miscel Ianeous

Pathophysiology and Treatment of Hydrocephalus

1451

1452 Miscel Ianeous

Pathophysiology and Treatment of Hydrocephalus

1453

1454 Miscel Ianeous

REFERENCES 1. Alvarez JA, Cohen AR. Neonatal applications of neuroendoscopy. Neurosurg Clin N Am 1998, 9, 405-413. 2. Aronyk KE. The history and classification of hydrocephalus. Neurosurg Clin N Am. Oct 1993; 4(4): 599-609. 3. Beems T, Grotenhuis JA. Is the success rate of endoscopic third ventriculostomy agedependent? An analysis of the results of endoscopic third ventriculostomy in young children. Childs Nerv Syst 2002, 18, 605–608. 4. Black PMcL, Ojemann RG. Hydrocephalus in adults. In: Youman JR, ed. Neurological Surgery. 3rd ed. Philadelphia, Pa:. WB Saunders Co;1990:927-944. 5. Brockmeyer D, Abtin K, Carey L, Walker ML. Endoscopic third ventriculostomy: an outcome analysis. Pediatr Neurosurg 1998, 28, 236–240. 6. Cohen AR. Endoscopic ventricular surgery. Pediatr Neurosurg 1994, 19, 127-134. 7. Gleason PL, Black PM, Matsumae M. The neurobiology of normal pressure hydrocephalus. Neurosurg Clin N Am. Oct 1993; 4(4): 667-675. 8. Grotenhuis JA: General principles of neuroendoscopy, in Grotenhuis JA: Manual of Endoscopic Procedures in Neurosurgery. Nijmegen: Machaon, 1995, pp 12-35. 9. Grotenhuis JA: Complications of neuroendoscopy, in Grotenhuis JA: Manual of Endoscopic Procedures in Neurosurgery. Nijmegen: Machaon, 1995, pp 57-63. 10. Grotenhuis JA: Third Ventriculocisternostomy, in Grotenhuis JA: Manual of Endoscopic Procedures in Neurosurgery. Nijmegen: Machaon, 1995, pp 98-104. 11. Grotenhuis JA. Endoscopic third ventriculostomy in the treatment of hydrocephalus. Thesis. University of Nijmegen, 2000, 1-248. 12. Hahn YS, Engelhard H, McLone DG. Abdominal CSF pseudocyst. Clinical features and surgical management. Pediatr Neurosci. 1985-1986; 12(2): 75-79. 13. Hellwig D, Grotenhuis JA, Tirakotai W, Riegel T, Schulte DM, Bauer BL, Bertalanffy H. Endoscopic third ventriculostomy for obstructive hydrocephalus. Neurosurg Rev. 2005 Jan; 28(1): 1-38. 14. McLone DG, Partington MD. Arrest and compensation of hydrocephalus. Neurosurg Clin N Am. Oct 1993; 4(4): 621-624. 15. Milhorat T. Hydrocephalus: Pathophysiology and Clinical Features. Neurosurgery. 1996; 3: 3625-3632. 16. Sainte-Rose C. Hydrocephalus in childhood. In: Youmans JR, ed. Neurological Surgery. Philadelphia, Pa:. WB Saunders Co; 1996: 890-926. 17. Siomin V, Cinalli G, Grotenhuis A, Golash A, Oi S, Kothbauer K, Weiner H, Roth J, Beni-Adani L, Pierre-Kahn A, Takahashi Y, Mallucci C, Abbott R, Wisoff J, Constantini S. Endoscopic third ventriculostomy in patients with cerebrospinal fluid infection and/ or hemorrhage. J Neurosurg 2002, 97, 519–524.

1455

Normal Pressure Hydrocephalus: from a practical point of view KIYOSHI TAKAGI, MD, PhD Department of Neurosurgery, Ohtakanomori Hospital, 113 Toyoshiki, Kashiwa, Chiba, 277-0863, Japan Key words: normal pressure hydrocephalus (NPH), gait disturbance, dementia, urinary incontinence, lumbar tap test, CSF shunt surgery

Introduction Normal pressure hydrocephalus (NPH) is one of the commonest causes of gait disturbance, dementia, and urinary incontinence. However, it is also one of the diseases easily over-looked. The typical clinical signs are slowly progressive gait disturbance, dementia, and urinary incontinence, which are also the characteristic features of the old ages. It is very often misdiagnosed as Parkinson disease, Alzheimer disease, overactive bladder syndrome, or disabilities by aging (geriatric triad). Brain CT scan and/or MRI shows dilated ventricles and sulci. Massive removal of cerebrospinal fluid (CSF) by lumbar spinal puncture (lumbar tap test) should not be hesitated to perform. When the patients show clinical improvement (mainly improved gait) by lumbar tap test, they are good candidates for CSF shunt surgery. Programmable shunt valve is strongly recommended to treat NPH.

Anatomical and physiological basis Normal cerebrospinal fluid (CSF) is watery clear. If it has some colors (usually, red or yellow), it means that the patient suffers form subarachnoid hemorrhage, meningitis, or some kind of degenerative diseases. Normal CSF pressure is between 60 mmH2O and 200 mmH2O. Recent understanding of CSF circulation is shown in Figure 1 [1]. Sixty to eighty percent of CSF are produced by choroid plexuses in the ventricles. The rest is produced by ventricular ependymal cell line and central nervous systems adjacent to CSF circulation. In adult, the amout of CSF is about 150 ml and the estimated amount of CSF production is about 500 ml. The circulation of CSF is shown in Figure 1 (arrows mean bulk flow of CSF). Most CSF is absorbed at arachnoid granulations and returns to blood circulation through superior sagital sinus. Minor part of CSF is, however, absorbed at spinal arachnoid villi and returns to blood circulation through epidural veins.

Definition of the disease Definition of hydrocephalus Hydrocephalus is conventionally defined as a state where an excess of CSF accumulates

1456 Miscel Ianeous

Fig. 1 CSF anatomy and circulation. “A” shows the anatomy and the pathway of CSF. “B” shows cerebral subarachnoid space and cerebral vessels. “C” shows the arachnoid villi of spinal root.

in the ventricular system because of the disturbed CSF circulation (over production, obstruction of CSF pathway, and/or disturbed absorption system) and intracranial pressure (ICP) is increased as a result (internal hydrocephalus). This definition is valid in most cases of child hydrocephalus and adult hydrocephalus of obstructive type. However, some cases show dilated subarachnoid spaces and this is called external hydrocephalus. The term “normal pressure hydrocephalus (NPH)” has been introduced by Hakim and Adams in 1965 [2, 3].

Definition of NPH In NPH, ICP is normal despite of enlarged ventricular system and typical clinical signs such as gait disturbance, dementia, and/or urinary incontinence are observed. The definition of ventricular enlargement is currently given by Evans’ index > 0.3 [4]. Figure 2 shows how to calculate the index. The original calculation of Evans’ index was based on the measurements on pneumoencephalogram [5], but recent measurements are based on computed tomogram (CT) or magnetic resonance image (MRI). Although CT or MRI shows enlarged ventricular system fulfilling the definition, the term “NPH” is not applied when clinical signs are not accompanied. On the contrary, it is not uncommon to see patients with the clinical signs without ventricular enlargement fulfilling the criteria. Most of these patients can be treated successfully by CSF shunt surgery. Therefore, the definition of the ventricular enlargement needs to be re-defined.

Normal Pressure Hydrocephalus: from a practical point of view

1457

Fig. 2 Evans’ index is calculated by dividing the widest transverse diameter of anterior horns by the widest width of inner diameter of the skull.

Classification of NPH There are two types of NPH. One is secondary normal pressure hydrocephalus (sNPH) and the other is idiopathic normal pressure hydrocephalus (iNPH). The causes of sNPH are multiple, such as subarachnoid hemorrhage, meningitis, brain tumors, and brain surgeries that disturb the CSF circulation (mainly disturb CSF absorption). Therefore, sNPH occurs at any age even in young adult. The pathogenesis of iNPH has not yet been elucidated. This is the reason why the term “idiopathic” is used. Although the guideline states that the age is over 40 years old [4], most patients are over 60 years old. The mean age of the patients treated by the author is 78 years old. The guideline may have been established on the data including other types of hydrocephalus such as “long-standing overt ventriculomegaly in adults (LOVA, Figure 3)” [6].

Diagnosis Figure 4 shows the diagnostic process proposed in the international guideline [4]. As show in Figure 4, the diagnosis of NPH is based on the characteristic clinical signs (gait disturbance, dementia, and urinary incontinence) and easily available neuroradiological findings. Therefore, it is fundamentally easy. However, it is very often overlooked because of these clinical signs are also characteristic to the old.

Clinical signs Clinical sins of NPH are gait disturbance, dementia, and urinary incontinence [4]. These signs are usually observed in the old people and the term “geriatric triad” is sometimes used. Among these signs, gait disturbance is most prevailing and usually noticed earlier than other signs. The patients can’t raise their leg high enough and

1458 Miscel Ianeous

Fig. 3 Typical MRI of LOVA (long-lasting overt ventriculomegary in adult). The ventricular system is enlarged but the age of this patient is 45 years old. She complaint headache, that is not usual in NPH.

Fig. 4 Diagnostic flow chart of NPH proposed in the international guideline. Tirad means a group of three clinical signs; gait disturbance, dementia, and urinary incontinence. The patients not always show three signs together but but at least one sign must be present. Ro means CSF out-flow resistance. ICP is expressed as mmHg.

Normal Pressure Hydrocephalus: from a practical point of view

1459

delete easy easily tumble with low steps. The gait is sometimes called “magnetic gait”. The patients are often apathetic and show slowness of thinking. The degree of dementia is very wide. Frontal lobe related functions, such as inattention, disturbed verbal fluency, and impaired memory are usually observed. In the far-advanced stage of the disease, the patient may become almost bed-ridden and close to vegetative state. Urinary incontinence may also be related to the frontal lobe function. Patients with NPH usually show bladder hyperactivity [7]. All of these signs are not always observed in all the patients. Some patients show only mild gait disturbance and other patients show only urinary incontinence. The progress of these signs is usually very slow and the patients are old. Therefore, these signs are very easily attributed to their old age. Although the patients with iNPH show these signs, definite neurological deficits such as motor paresis and sensory disturbances are not usually observed. If some definite neurological deficits are observed in the patients, organic brain disease such as cerebral infarction must be suspected.

Neuroradiological findings Brain CT scan or MRI is mandatory. The high-resolution image is not necessary to diagnose NPH. In these days, CT scan is available almost all over the world very easily. Coronary section of MRI by T2 weighted image is recommended [8]. In typical iNPH patient, high convexity subarachnoid space is tight [8]. As discussed in the part of definition of NPH, enlarged ventricular systems are characteristic and it is defined by Evans’ index > 0.3 (Figure 2) [4]. Typical cases are demonstrated in Figure 5 and 6. Figure 6 shows the slowly progressive nature of the disease.

Fig. 5 Typical MRI (T2 weighted image) findings of iNPH. 81-year-old woman with the triad. Marked enlargement of ventricular system and tight high convexity subarachnoid space. In this case, dilatation of Sysvian fissure is not prominent.

1460 Miscel Ianeous

A

B

Fig. 6 Slow progress of NPH. Figure 6B is a MRI coronal image taken 1 year after Figure 6A. The expansion of ventricular system is noted and high convexity subarachnoid space becomes tighter in Figure 6B than in Figure 6A.

Diagnostic tests Although international guidelines recommend CSF dynamic test [4], CSF bolus removal by lumbar puncture (LP) is easy, safe and enough in daily neurosurgical diagnostic stage. The recommend amount of CSF removal is 40 to 50 ml [4]. The author’s personal experience is that the larger the amount of CSF removal, the higher the rate of clinical improvement. The author recommends CSF removal up to 50 ml if possible. Although LP in the lateral recumbent position gives intracranial pressure (ICP) or CSF pressure and, as a definition of NPH, it must between 5 and 18 mmHg (68 and 244.8 mmH2O, nearly 70 and 250 mmH2O) [4], measurement of ICP is not always possible and not mandatory for the diagnosis of NPH. When the patient shows slowly progressive clinical signs of NPH with enlarged ventricular system without intracranial organic lesions and improvement of clinical sings by CSF removal by LP is observed, NPH is strongly suspected and CSF shunt surgery must be considered.

Differential diagnosis and problem of comorbidity Gait disturbance, dementia, and urinary incontinence are common in the elderly without definite neuroimaging abnormalities. Pakinson’s disease, spino-cerebellar degeneration, and progressive supranuclear palsy are common causes of gait disturbance in the elderly. Alzheimer’s disease, fronto-temporal dementia, Pick’s disease, and dementia with lewy bodies are the leading causes of senile dementia. Prostate cancer,

Normal Pressure Hydrocephalus: from a practical point of view

A

1461

B

Fig. 7 Very rapid progression of Creutzfeldt-Jacob disease. Figure 7B is a MRI coronal image taken only 3 months after Figure 7A.

benign prostate hypertrophy, over active bladder, and stress urinary incontinence are commonly observed in the old people. In the early phase of Creutzfeldt-Jacob disease (CJD), the patient shows gait disturbance similar to NPH. However, the progress of CJD is quite rapid clinically and pathologically. Figure 7 shows the rapid progression of CJD on MRI. It is of course that these diseases must be ruled out to diagnose NPH. However, the important thing is that these conditions can coexist with NPH (comorbidity). Therefore, bolus CSF removal by LP is strongly recommended when a patient shows one of the triad. It is important because some aspects of the clinical signs can be eliminated by treating NPH.

Treatment Currently, CSF shunt surgery and endoscopic third ventriculostomy (ETV) are the only two treatment modalities [4]. However, it is still difficult to decide which patient with NPH can be successfully treated by ETV. Those who can be treated by ETV can also be treated by shunt surgery. Therefore, CSF shunt surgery is most reliable and prevailing. In the shunt surgery, externally programmable valve is recommended [4]. Although many types of shunt surgeries are proposed [9], only ventriclulo-peritoneal shunt (VP shut), ventriculo-atrial shunt (VA shunt), and lumbo-peritoneal shunt (LP shunt) are applied to treat NPH. Among these three shunt surgeries, VP shunt is most frequently used [10]. However, there is no evidence that supports to utilize VP shunt as the first choice of CSF shunt. In a leading textbook of neurological surgery, VA shunt was once recommended [11]. The author also prefers VA shunt with some modification. In

1462 Miscel Ianeous the original VA shunt surgery, venous catheter was introduced through facial vein to atrium [12]. Hakim and Adams also used VA shunt for the treatment of NPH [2, 3]. The author inserts venous catheter directly through internal jugular vein by exposing the vein and introduces the catheter into superior vena cava. Therefore, the term ventriculo-caval shunt (VC shunt) is a better name. Although the risk of infection has been reported roughly to be 6% [4], the author experienced only one infection out of over 200 VC Shunts (data not published).

Fig. 8 Three types of shunt surgery. VP shunt is most prevailing (over 95%). LP shunt is increasing now, especially in Japan. VA shunt is almost abandoned but the author prefers this surgery.

Complication of shunt surgery There are many types of complications in CSF shunt surgery [4, 13]. The following are the list of complications; cranial nerve palsy (fourth nerve, sixth nerve, and seventh nerve), intracranial hemorrhage (surface, deep, and intraventricular), subdural fluid and/or hematoma collection, motor seizure, CSF infection, pneumonia, deep vein thrombosis, death, and so on. The serious complication except death may be CSF infection. The risk is around 6% [4]. Early diagnosis is most important to treat CSF infection and removal of shunt system is recommended. Subdural fluid and/or hematoma collection needs sometimes surgery. External programmable shunt valve is convenient to treat this complication. Once the subdural collection is noted, then the outflow pressure is raised maximally and the patient is kept in bed rest with enough intravenous fluid infusion. In majority of the cases, subdural collection can be treated without surgery.

Normal Pressure Hydrocephalus: from a practical point of view

1463

Conclusion NPH is one of the commonest causes of treatable gait disturbance, urinary incontinence, and dementia. Yet, these clinical signs are also common to the elderly and it is usually called “geriatric triad.” Therefore, NPH, especially iNPH, is very easy to be overlooked. Lumbar puncture is an easy, safe, and quite useful diagnostic procedure. It is important to check brain CT or MRI in the elderly with one of the three signs to rule out NPH. Despite a long history of NPH study, practical guideline has just emerged and it is quite incomplete. Piling up clinical and neuroradiological findings through careful observation is required for creating a better guideline. Clinical CSF study will also give new clue to understanding the veiled CSF function.

REFERENCES 1. Rowland, L.P. and e. al., Cerebrospinal fluid: Blood-Brain-Barrier, brain edema, and Hydrocephalus, in Principles of neuroscience, 3rd ed., R.R. Kandel, J.H. Shwarz, and J.T. M., Editors. 1991, Elsevier: New York, Amsterdam. p. 1050. 2. Hakim, S. and R.D. Adams, The special clinical problem of symptomatic hydrocephalus with normal cerebrospinal fluid pressure. Observations on cerebrospinal fluid hydrodynamics. J Neurol Sci, 1965. 2(4): p. 307-27. 3. Adams, R.D., et al., Symptomatic Occult Hydrocephalus with "Normal" CerebrospinalFluid Pressure.A Treatable Syndrome. N Engl J Med, 1965. 273: p. 117-26. 4. INPH GUIDELINE STUDY GROUP, Guidelines for the diagnosis and management of idiopathic normal-pressure hydrocephalus. Neurosurgery, 2005. 57(3 Suppl): p. S2-1S2-52. 5. Evans, W.A., An encephalographic ratio for estimating ventricular and cerebral atrophy. Arch Neurosurg Psychiatry, 1942. 47: p. 931-7. 6. Oi, S., et al., Pathophysiology of long-standing overt ventriculomegaly in adults. J Neurosurg, 2000. 92(6): p. 933-40. 7. Ahlberg, J., et al., Outcome of shunt operation on urinary incontinence in normal pressure hydrocephalus predicted by lumbar puncture. J Neurol Neurosurg Psychiatry, 1988. 51(1): p. 105-8. 8. Kitagaki, H., et al., CSF spaces in idiopathic normal pressure hydrocephalus: morphology and volumetry. AJNR Am J Neuroradiol, 1998. 19(7): p. 1277-84. 9. Pudenz, R.H., The surgical treatment of hydrocephalus--an historical review. Surg Neurol, 1981. 15(1): p. 15-26. 10. Black, P.M., Hydrocephalus in adults, in Neurological Surgery: A comprehensive reference guide to the diagnosis and management of neurosurgical problems, J.R. Youmans, Editor. 1996, W. B. Saunders Company: Philadelphia, London, Toronto, Montreal, Sydney, Tokyo. p. 927-44. 11. Ojemann, R.G. and P.M. Black, Hydrocephalus in adults, in Neurological Surgery: A comprehensive reference guide to the diagnosis and management of neurosurgical problems, J.R. Youmans, Editor. 1982, W. B. Saunders Company: Philadelphia, London, Toronto, Mexico City, Sydney, Tokyo. p. 1423-35. 12. Pudenz, R.H., Experimental and clinical observations on the shunting of cerebrospinal fluid into the circulatory system. Clin Neurosurg, 1957. 5: p. 98-114; discussion 114-5. 13. Lam, C.H. and J.G. Villemure, Comparison between ventriculoatrial and ventriculoperitoneal shunting in the adult population. Br J Neurosurg, 1997. 11(1): p. 43-8.

1464

Chronic CSF Depletion Syndrome (Intracranial Hypotension Syndrome) J. ANDRÉ GROTENHUIS Department of Neurosurgery, University Medical Center St. Radboud, Reinier Postlaan 4, 6525GC Nijmegen, The Netherlands Key words: chronic SCF depletion syndrome (CCSFD), intracranial hypotension syndrome (IHS), orthostatic headache, CSF leak, epidural blood patching

Introduction The syndrome of chronic CSF depletion (CCSFD) or intracranial hypotension syndrome (IHS) is a single pathophysiological entity of diverse origin, typically characterized by an orthostatic headache (i.e. one that occurs or worsens with upright posture), although patients with chronic headaches or even no headache have been described. After Quinke introduced the lumbar puncture in 1891 for diagnostic purposes, the lumbar puncture-related headaches were described rather soon after it (e.g. the surgeon August Bier himself suffered from it after a lumbar puncture and was the first to report them in 1898). George Schaltenbrand, a German neurologist, in a German-language article in 1938 and in an English-language article in 1953 emphasized the term "aliquorrhea", a condition marked by very low, unobtainable, or even negative CSF pressures that were clinically manifested by orthostatic headaches and other features that later came to be recognized as spontaneous intracranial hypotension. A few decades earlier the same syndrome had been described in the French literature as "hypotension of spinal fluid" or "ventricular collapse." Initially it was theorized that the cause of aliquorrhea or spontaneous intracranial hypotension was decreased CSF production or increased CSF absorption. However, modern evidence has not provided support for either theory, but it has implicated CSF leakage. Understandably the technology of the time could not have allowed Schaltenbrand or his contemporaries to assess patients adequately for CSF leakage. The full clinical manifestations of intracranial hypotension or CSF leak were described in several publications reported between the 1960s and early 1990s. The introduction of radioisotope cisternography, water-soluble myelography, and CT myelography provided the clinicians with more effective tools to diagnose and locate CSF leaks. In the 1990s MR imaging-documented abnormalities in CSF volume depletion due to CSF leakage or CSF shunt over-drainage were described. All of these discoveries have resulted in broader recognition of the syndrome and its variations.

Pathophysiology There is strong evidence indicating that most cases of CCSFD/IHS result from a

Chronic CSF Depletion Syndrome (Intracranial Hypotension Syndrome)

1465

persistent CSF leak. Such a leak most commonly occurs after dural puncture for a diagnostic LP, myelography, or spinal anesthesia. Nonetheless, symptoms of CCSFD/IHS may be experienced any time the dura mater is violated, such as after craniotomy, spinal surgery, craniospinal trauma, or placement of a ventriculoperitoneal shunt. In some cases, this syndrome may occur in the absence of an identifiable precipitant and, in fact, is believed to have developed spontaneously. Medical causes of CCSFD/IHS include dehydration, diabetic coma, hyperpnea, uremia, and severe systemic illness. Loss of CSF caused by the formation of a thoracomeningeal fistula is a rare complication of thoracic surgery. Cerebrospinal fluid volume depletion related to CSF shunt overdrainage or posttraumatic or postsurgical CSF leaks is well recognized. More intriguing are the CSF leaks that develop spontaneously. The majority of these occur in the thoracic spine or at the cervicothoracic junction; leaks occurring at other levels of spine are less common, and those demonstrated at the skull base are by far the least frequent. In spontaneous CSF leaks the exact cause often remains unknown, but two contributing factors are frequently suspected: 1) weakness of meningeal sac in certain regions and 2) trivial traumatic injury. A history of trivial traumatic injury is reported by many, although not the majority of patients with spontaneous CSF leaks. The following observations implicate focal weakness of thecal sac in some of these patients, which may be related to abnormality or deficiency of elastin or fibrillin in some of them: CSF leaks in Marfan syndrome, marfanoid features in some patients with CSF leaks, history of retinal detachment at young age, frequent detection of meningeal diverticula, sometimes multiple, and diverticula in certain inheritable disorders of connective tissue. Occasionally, a dural tear caused by a spondylotic spur may lead to CSF leak.

Clinical symptomatology The typical clinical manifestation in CSF volume depletion is orthostatic headache -a headache that typically occurs when the patient is upright and relieved by recumbency. It may be bifrontal, occipital, occipital and bifrontal, or holocephalic, and it may or may not be throbbing. Variability in the form of headache, however, is considerable. Sometimes, particularly in patients with chronic headache, the orthostatic features may blur and the headache may take the form of a lingering chronic daily headache that may or may not be more pronounced in upright position. Sometimes the headache may begin as a lingering headache, and typical orthostatic features may appear days or weeks later. At times the headache may be preceded by neck pain or interscapular pain for days or weeks. In patients with intermittent CSF leaks, the headaches (and any of the just-described features) may disappear for variable periods and reappear again. The nature and location of the headache vary greatly from patient to patient; but consistently the pain is exacerbated by laughing, coughing, jugular venous compression, and Valsalva maneuver, and is resistant to treatment with analgesic agents. In addition to headache, patients may experience nausea, vomiting, anorexia, neck pain, dizziness, horizontal diplopia, which is typically horizontal and due to unilateral or bilateral sixth cranial nerve palsy; dizziness; change in hearing (muffled or distant

1466 Miscel Ianeous hearing, distorted hearing, or echoes); visual blurring; photophobia; interscapular pain, galactorrhea, facial numbness or weakness, or radicular symptoms involving the upper limb, all of which are orthostatic in nature. When cervical, thoracic, or lumbar spine pain is present, the CSF level of the leak may not necessarily correspond with the level of the pain (indeed it often does not). Therefore this often, although not always, proves to be a false localizing sign. CCSFD/IHS generally is considered to be a benign condition, and most cases resolve with conservative management. With advances in diagnosis, however, atypically disabling presentations are increasingly recognized including parkinsonism, frontotemporal dementia, syringomyelia, hypopituitarism, seizures, coma, and death.

Diagnostic workup Diagnostic Procedures The diagnosis of CCSFD/IHS usually can be confirmed by demonstrating decreased CSF opening pressure, often less than 60 mm H20, on performing an LP. In some cases, spinal pressure may be so low that Valsalva maneuver or gentle aspiration with a syringe is required to produce CSF. Rarely, a "sucking noise" has been described to occur as the stylet is withdrawn and air enters the subarachnoid space, indicating subatmospheric pressure. Analysis of the CSF may show it to be entirely within normal limits, but more often increased protein concentration, lymphocytic pleocytosis, increased erythrocyte count, and/or xanthochromia are identified at some point during the patient's illness. Cultures of CSF are always nondiagnostic, and glucose levels are never low. In patients with intermittent or variable CSF leaks, variable pressures may be recorded at different times in the same patient ranging from very low, to low normal to entirely normal.

Imaging Studies Advances in neuroimaging have improved our ability to diagnose cCSFD/IHS. In particular, findings on MR imaging studies that are characteristic of this syndrome have allowed physicians to appreciate its true incidence as well as its varied modes of presentation, although other imaging modalities, like radioisotope cisternography and (CT-) myelography still have their use in diagnosis of .

CT Scanning In CSF leaks, head CT scanning is of limited value and typically demonstrates negative results. Only occasionally does it demonstrate subdural fluid collections or increased tentorial enhancement.

Indium 111 Radioisotope Cisternography In CSF leaks, typically the radioactivity produced by the radioisotope produced intrathecally at the lumbar level does not extend much beyond the basal cisterns and

Chronic CSF Depletion Syndrome (Intracranial Hypotension Syndrome)

1467

cannot be visualized over the cerebral convexities even at 24 or 48 hours postinjection. Less commonly it may demonstrate the level of the leak or the larger diverticulum. A common observation is early appearance of radioactivity in the kidneys and urinary bladder. This should not be misinterpreted as a manifestation of increased CSF reabsorption, as the radioisotope hardly reaches the brain convexities to be reabsorbed. Early clearance of radioactivity is an indication of a CSF leak, which has allowed extravasation of radioisotope in the paraspinal tissues, its early entrance into the venous system, and, therefore, its early clearance by the kidney and its early appearance in the urinary bladder.

Myelography and CT Myelography Myelography and CT myelography can demonstrate meningeal diverticula and extraarachnoid-dural leakage of contrast. Computerized tomography myelography is the best test for demonstrating site of CSF leak. Considering that the leaks may be rapid or slow, early and delayed CT cuts may be necessary and should be obtained at each spinal level; however, if cisternography or spine MR imaging has demonstrated the approximate level of the leak, then CT cuts may be concentrated in this zone.

Magnetic Resonance Imaging Magnetic resonance imaging has revolutionized the diagnosis of CCSFD/IHS. The major abnormalities demonstrated on MR imaging studies in patients with CCSFD/IHS are diffuse thickening of the pachymeninges with Gd enhancement, engorgement of venous sinuses, subdural fluid collections, enlargement of the pituitary gland, and downward displacement of the brain. The resolution of these abnormalities on MR images parallels improvement in clinical symptoms. Abnormalities demonstrated on head MR imaging studies in patients with CSF volume depletion include: • diffuse pachymeningeal enhancement (both supra- and infratentorial, bilateral, linear and nonnodular, typically uninterrupted, often thick and obvious, sometimes very thin, but always without leptomeningeal involvement • sinking or sagging of the brain, descent of the cerebellar tonsils sometimes mimicking Chiari I malformation • decrease in the size of prepontine and perichiasmatic cisterns • inferior displacement of the optic chiasm • crowding of posterior fossa • subdural fluid collections (uni- or bilateral and typically over the convexities of the brain, typically 2 to 7 mm in maximum thickness without compression or effacement of the underlying sulci, and with variable MR signal intensity depending on fluid protein concentration or presence of blood • decrease in size of the ventricles (sometimes obvious, sometimes quite subtle and only noted when pre- and postrecovery MR images are compared) • pituitary enlargement (sometimes mimicking pituitary adenoma or hyperplasia • enlarged/ engorged venous sinuses.

1468 Miscel Ianeous Abnormalities demonstrated on spine MR imaging studies include: • the presence of extraarachnoid/extradural fluid • meningeal diverticula (of various size, single or multiple, and may or may not be the actual site of the leak) • spinal pachymeningeal enhancement • enlargement and prominence of epidural venous plexus. • Sometimes the actual site of the CSF leak can be detected using spine MR imaging, but so far CT myelography with water-soluble contrast is the study of choice for demonstrating the site of the CSF leaks.

Doppler Flow Imaging A new technique has recently been used to successfully diagnose CCSFD/IHS. Given that the superior ophthalmic vein is a tributary of the cavernous sinus, Chen, et al., hypothesized that it might reflect the engorgement of the intracranial venous sinuses that occurs in CCSFD/IHS. Using transorbital color Doppler flow imaging, they demonstrated increased diameter and maximum flow velocity of the superior ophthalmic veins in patients with CCSFD/IHS. Statistical analysis indicates that this technique may have a very high sensitivity and specificity, demonstrating significant increases of these parameters in all of their 26 patients when compared with either healthy volunteers or patients with headache of other origin. In addition, this change in blood flow reverted to normal after treatment, paralleling resolution of symptoms.

Mechanism of MR Abnormalities and Clinical Manifestations Evidence indicates that several of these abnormalities are the result of vascular dilation to compensate for reduced CSF volume. This idea is based on the application of the Monro–Kellie hypothesis, which states that the sum of the volumes of intracranial blood, CSF, and brain tissue must remain constant in an intact cranium. According to this hypothesis, increased intracranial blood volume compensates for acute loss of CSF. Most of this compensation occurs through dilation of the venous side of the circulation, given its greater compliance and capacitance. Thus, venous sinus engorgement, abnormal pachymeningeal enhancement, subdural effusions, and enlargement of the pituitary gland occurring in CCSFD/IHS may represent compensatory changes to maintain intracranial volume in the face of CSF loss. Although it is a frequent finding, abnormal meningeal enhancement in patients with CCSFD/IHS is not the absolute rule. Mokri, et al., documented enhancement that resolved while the patients were still symptomatic, a patient without enhancement on initial studies, and patients whose MR images never revealed enhancement. Thus, it seems that Gadolineum enhancement varies during the course of a patient's illness. Furthermore, in some patients, the loss of volume and hydrostatic pressure changes may never be sufficient to result in venous congestion significant enough to lead to the appearance of meningeal enhancement on MR images. Another consequence of CSF volume depletion is sinking of the brain and ventricular collapse that lead to a decrease in size of the ventricles, descent of the cerebellar tonsils,

Chronic CSF Depletion Syndrome (Intracranial Hypotension Syndrome)

1469

crowding of posterior fossa, and obliteration of some of the subarachnoid cisterns. The major clinical consequence of sagging of the brain is traction and distortion of pain-sensitive suspending structures of the brain as well as development of orthostatic headaches. Similarly, compression of the cranial nerves (fifth, sixth, and seventh) is likely responsible for palsy that is sometimes noted to afflict these nerves. Visual blurring and visual field cuts likely result from compression or vascular congestion of intracranial portions of optic nerves. Galactorrhea and increased prolactin are likely caused by distortion of pituitary stalk. Dizziness and changes in hearing may be related to stretching of the eighth cranial nerve or, alternatively, to pressure change in the perilymphatic fluid of the inner ear. Radicular upper-limb symptoms may be a consequence of stretching of cervical nerve roots or the presence of structural abnormalities at the nerve root sleeve level. Stupor has been related to diencephalic compression and ataxia to compression of posterior fossa elements.

Treatment No definite standard approaches have been established. Bed rest, hydration, caffeine or theophylline, steroid medications, abdominal binders, epidural blood patch, continuous epidural saline infusion, epidural infusion of dextran, placement of a CSF shunt, and surgical repair of the leaks are some of the modalities that have been implemented. Many patients fortunately improve spontaneously. The beneficial effect of recumbency in sealing the leak has not been proven. However, because of the often orthostatic nature of the headache, many of the patients choose to remain recumbent as much as possible. Similarly, the effectiveness of hydration or overhydration has not been definitely established. The effectiveness of caffeine and theophylline therapy demonstrated in some studies, by and large is often unimpressive and not durable. Evidence for the efficacy of steroid therapy is at best sporadic, and a substantial lasting effect is doubtful. When the initial conservative management fails, an epidural blood patch procedure is the treatment of choice. Its effect is essentially twofold: 1) an immediate effect related simply to volume replacement by compressing the dura; and 2) a more latent effect related to sealing of the dural defect. Approximately half of the patients require more than one application of a blood patch. In our experience some patients have required as many as four to six epidural blood patches. Epidural saline infusion has produced varying results. Such therapy can be considered (with limited expectations) in some of the patients in whom repeated blood patch procedures have failed, especially if the site of the leak has not been found, which excludes a surgical approach. Surgery in well-selected cases should be considered when conservative measures and epidural blood patches have failed to resolve the CSF leakage. Although it would be beyond the scope of this book to discuss all technical aspects, it is good to stress a few points: ideally the site of the leak should be demonstrated preoperatively. Although dural tears, holes, and leaking diverticula can be usually repaired without significant difficulty, some cases are not entirely straightforward. The surgeon may encounter the leaking CSF but may not be able to find the exact site of the leak; a patchlike dural defect with attenuated margins may be detected that may not yield to suturing; or a leak may be

1470 Miscel Ianeous present at more than one site. The presence of a meningeal diverticulum, even when large, may not necessarily indicate the site of the leak unless neuroimaging studies have demonstrated extravasation of contrast or fluid in that area.

Conclusions The patient presenting with headache is very often a diagnostic dilemma, but the indiscriminate screening of these patients by performing MR imaging is not a good use of an expensive resource. CCSFD/HIS should be considered when there is a clear correlation of the headache with the patient position, a recent history of LP, or an accompanying cranial nerve deficit and prompt the appropriate use of Gadolineumenhanced MR imaging of the brain. The headache of CCSFD/IHS usually resolves with conservative management, but if it does not, epidural blood patching is highly effective.

Gadolineum-enhanced axial MRI image with the typical enhancement of the leptomeninges

Gadolinium-enhanced coronal MR image demonstrating diffuse, non-nodular leptomeningeal enhancement and also bilateral subdural fluid collections

Chronic CSF Depletion Syndrome (Intracranial Hypotension Syndrome)

1471

REFERENCES 1. Atkinson LD, Weinshenker BG, Miller GM, et al: Acquired Chiari I malformation secondary to spontaneous spinal cerebrospinal fluid leakage and chronic intracranial hypotension syndrome in seven cases. J Neurosurg 88:237-242, 1998 2. Bakshi R, Mechtler LL, Kamran S, et al: MRI findings in lumbar puncture headache syndrome: abnormal dural-meningeal and dural venous sinus enhancement. Clin Imaging 23:73-76, 1999 3. Beck CE, Rizk NW, Kiger LT, Spencer D, et al: Intracranial hypotension presenting with severe encephalopathy. Case report. J Neurosurg 89:470-473, 1998 4. Bell WE, Joynt RJ, Sahs AL: Low spinal fluid pressure syndromes. Neurology 10:512-521, 1960 5. Benamor M, Tainturier C, Graveleau P, et al: Radionuclide cisternography in spontaneous intracranial hypotension. Clin Nucl Med 23:150–151, 1998 6. Brightbill TC, Goodwin RS, Ford RG: Magnetic resonance imaging of intracranial hypotension syndrome with pathophysiological correlation. Headache 40:292–299, 2000 7. Bruera O, Bonamico L, Giglio JA, et al: Intracranial hypotension: the nonspecific nature of MRI findings. Headache 40: 848–852, 2000 8. Chen CC, Luo CL, Wang SJ, et al: Colour Doppler imaging for diagnosis of intracranial hypotension. Lancet 354:826–829, 1999 9. DiGiovanni AJ, Galbert MW, Wahle WM: Epidural injection of autologous blood for postlumbar-puncture headache. II. Additional clinical experiences and laboratory investigation. Anesth Analg 51:226-232, 1972 10. Dillon WP, Fishman RA: Some lessons learned about the diagnosis and treatment of spontaneous intracranial hypotension. AJNR 19:1001-1002, 1998 (Editorial) 11. Fishman RA, Dillon WP: Dural enhancement and cerebral displacement secondary to intracranial hypotension. Neurology 43:609-611, 1993 12. Front D, Penning L: Subcutaneous extravasation of CSF demonstration by scinticisternography. J Nucl Med 15:200-201, 1974 13. Gibson BE, Wedel DJ, Faust RJ, et al: Continuous epidural saline infusion for the treatment of low CSF pressure headache. Anesthesiology 68:789-791, 1988 14. Hochman MS, Naidich TP: Diffuse meningeal enhancement in patients with overdraining, long-standing ventricular shunts. Neurology 52:406-409, 1999 15. Hochman MS, Naidich TP, Kobetz SA, et al: Spontaneous intracranial hypotension with pachymeningeal enhancement on MRI. Neurology 42:1628-1630, 1992 16. Hong M, Shah GV, Adams KM, et al: Spontaneous intracranial hypotension causing reversible frontotemporal dementia. Neurology 58:1285–1287, 2002 17. Horton JC, Fishman RA: Neurovisual findings in the syndrome of spontaneous intracranial hypotension from dural cerebrospinal fluid leak. Ophthalmology 101:244251, 1994 18. Inenaga C, Tanaka T, Sakai N, et al: Diagnostic and surgical strategies for intractable spontaneous intracranial hypotension. Case report. J Neurosurg 94:642–645, 2001 19. Lasater, GM: Primary intracranial hypotension. The low spinal fluid pressure syndrome. Headache 10:63-66, 1970 20. Moayeri NN, Henson JW, Schaefer PW, et al: Spinal dural enhancement on magnetic resonance imaging associated with spontaneous intracranial hypotension. Report of three cases and review of the literature. J Neurosurg 88:912-918, 1998 21. Mokri B: Spontaneous cerebrospinal fluid leaks: from intracranial hypotension to cerebrospinal fluid hypovolemia -- evolution of a concept. Mayo Clin Proc 74:1113-1123, 1999

1472 Miscel Ianeous 22. Mokri B, Atkinson JLD, Dodick DW, et al: Absent pachymeningeal gadolinium enhancement on cranial MRI despite symptomatic CSF leak. Neurology 53:402-404, 1999 23. Mokri B, Hunter SF, Atkinson JLD, et al: Orthostatic headaches caused by CSF leak but with normal CSF pressures. Neurology 51:786-790, 1998 24. Mokri B, Piepgras DG, Miller GM: Syndrome of orthostatic headaches and diffuse pachymeningeal gadolinium enhancement. Mayo Clin Proc 72:400-413, 1997 25. Molins A, Alvarez J, Sumalla J, et al: Cisternographic pattern of spontaneous liquoral hypotension. Cephalalgia 10:59-65, 1990 26. Murros K, Fogelholm R: Spontaneous intracranial hypotension with slit ventricles. J Neurol Neurogurg Psychiatry 46: 1149-1151, 1983 27. Pakiam AS, Lee C, Lang AE: Intracranial hypotension with parkinsonism, ataxia, and bulbar weakness. Arch Neurol 56: 869-872, 1999 28. Pannullo SC, Reich JB, Krol G, et al: MRI changes in intracranial hypotension. Neruology 43:919-926, 1993 29. Pleasure SJ, Abosch A, Friedman , et al: Spontaneous intracranial hypotension resulting in stupor caused by diencephalic compression. Neurology 50:1854-1857, 1998 30. Rabin BM, Roychowdhury S, Meyer JR, et al: Spontaneous intracranial hypotension: spinal MRI findings. AJNR 19: 1034-1039, 1998 31. Rice GG, Dabbs CH: The use of peridural and subarachnoid injections of saline solution in the treatment of severe post-spinal headaches. Anesthesoiology 11:17-23, 1950 32. Schaltenbrand G: Neure Anschauungen zur Pathophyiologie der Liquorzirkulation. Zentrablbl Neurochir 3:290-300, 1938 33. Schaltenbrand G: Normal and pathological physiology of the cerebrospinal fluid circulation. Lancet 1:805-808, 1953 34. Schievink WI, Morreale VM, Atkinson JLD, et al: Surgical treatment of spontaneous spinal cerebrospinal fluid leaks. J Neurosurg 88:243-246, 1998 35. Silberstein SD, Marcelis J: Headache associated with changes in intracranial pressure. Headache 32:84, 1992 36. Sipe JC, Zyroff J, Waltz TA: Primary intracranial hypotension and bilateral isodense subdural hematomas. Neurology 31: 334-337, 1981 37. Vishteh AG, Schievink, Baskin JJ, et al: Cervical bone spur presenting with spontaneous intracranial hypotension. Case report. J Neurosurg 89:483-484, 1998 38. Weber WE, Heidendahl GA, de Krom MC: Primary intracranial hypotension and abnormal radionuclide cisternography: report of a case and review of the literature. Clin Neurol Neurosurg 93:55-60, 1991 39. Yamamoto M, Suehiro T, Nakata H, et al: Primary low cerebrospinal fluid pressure syndrome associated with galactorrhea. Intern Med 32:228-231, 1993 40. Yousry I, Forderreuther S, Moriggl B, et al: Cervical MR imaging in postural headache: MR signs and pathophysiological implications. AJNR 22:1239–1250, 2001

1473

Endoscopic Third Ventriculostomy (ETV) TAMOTSU MIKI, MD Department of Neurosurgery, Tokyo Medical University Key words: endoscopic, third ventriculostomy, flexible endoscope, infundibular recess, hydrocephalus

Introduction Endoscopic neurosurgery has created high expectations because it is less invasive than other alternatives. However, the surgery can potentially lead to serious complications. We herein outline endoscopic third ventriculostomy (ETV), which is one of the most common endoscopic procedures in neurosurgery.

Indication of third ventriculostomy The indication of third ventriculostomy is shown in Table 1. Patient with ballooning of the third ventricular floor, seen on preoperative MRI sagital section, is especially a good candidate for such surgery (Figure 1.). Table 1 Positive Prognostic Factors for Successful Outcome of Third Ventriculostomy (Teo C, 1998) 1) Aqueduct stenosis: primary or secondary. 2) CT showing triventricular hydrocephalus. 3) Oval-shaped third ventricle. 4) >2 years of age. 5) Previously shunted. 6) No previous radiation. 7) Transparently thin third ventricular floor.

Fig. 1 (left: pre-operation, right: post-operation)

1474 Miscel Ianeous

Fig. 2 Olympus VEF Type V, Olympus corporation, Tokyo

Setup of the surgery 1. Assignment of a surgeon, assistant, and care nurse. 2. An operating table, anesthesia apparatus, instrument table, monitor, and special equipment for endoscopic surgery (Micro Endoscopic Electrode (ME2) : Codman (Johnson & Johnson). Placed so that the monitor is preferably in front of the surgeon. Position of the patient (1) Supine position (2) Head-up (so that the burr hole is preferably on the top) (3) Fixation of the head The head is in the neutral position in principle. The orientation is more easily maintained. 4. Anesthesia General anesthesia is preferred, but local anesthesia is also possible in some cases. 5. Head shaving and draping Both partial head shaving and full head shaving are possible. Draping with a fluid-collecting pouch for reflux liquid drainage is useful. 6. Preparation and setup of the flexible endoscope We use the videoscope (Olympus VEF Type V, Olympus corporation Tokyo) because of its excellent image quality and maneuverability (Figure 2). Endoscope is conneceted to the light source device and video system. White balancing and, if necessary, the black balancing is done. Scope is moved from side to side or up and down to make comparisons with the field of view on the monitor. Inspection of treatment tools and running simulation using the monitor is done. 7. Example of positioning the endoscopic system (Figure 3) The positions of the operative field and the monitor should preferably be in the same direction.

Endoscopic Third Ventriculostomy (ETV)

1475

Fig. 3

Surgical manipulation I - Inserting the Flexible Endoscope into the ventriclar system 1. Holding the Flexible Endoscope Usually, the Flexible Endoscope is manipulated freehand, but for a right-handed operator, the device is positioned such that the body of endoscope is held vertically with left hand and the end of the scope is held with right hand, or so that the body of endoscope is held horizontally with right hand, and the end is held with left hand. The former is method of holding the endoscope that matches the original configuration, and it is easy for orientation, which is suitable for beginners. 2. Skin incision and skull perforation: Either a right or left anterior horn puncture is fundamental. Skin incision 12 cm posterior to the nasion (right before coronal suture) and about 3 cm lateral from the median line. Skull peroration to fully expose the dura mater is performed. 3. Dura matter incision: Minimum coagulations for pediatric cases (so that suturing can be done later). 4. Appropriate ventricular puncture: Anterior horn puncture with a ventricular puncture needle (make puncture vertically into the cerebral surface and not too deep). Check the drainage of cerebrospinal fluid (CSF). 5. Inserting a peel away sheath: Measure the distance between cerebral surface and ventricular wall, and be careful to avoid inserting the sheath too deep. Peel away the sheath, and fix the stump loosely. 6. Inserting the endoscope: Check the position of the end of the sheath before it enters the ventricle. If the operative field is stained with blood, insert under irrigation with artificial liquor. • If the sheath is not used, insert a drainage catheter after ventricular puncture, followed by endoscope along the catheter. If another burr hole is made for smaller ventricular system, ventricular puncture may be performed after irrigation fluid is infused into the ventricle to enlarge the them slightly following cerebrospinal fluid sampling. 7. Basic principle of manipulating the endoscope

1476 Miscel Ianeous [1] Check the projection of the flexible scope upon insertion To prevent damage to the surrounding tissue, be sure to insert and retract the endoscope in the center of the operative field. Align the axis of insertion with the center of the operative field (Figure 4). Never retract the endoscope with the tip bent.

Fig. 4 The concordance of projection of endoscope and operative target

[2] Do not maneuver the endoscope without a clear operative field. In the event of bleeding, without moving the endoscope, expose the normal anatomical area while rinsing it to verify the bleeding point and continue to rinse. [3] Place the object so as to manipulate as much directly below the vertical axis as possible. [4] Manipulate slowly and carefully. 8. Fundamental intraventricular observation Check following structures that constitute the characteristics of lateral ventricle. (foramen of Monro, chorioid plexus, anterior septal vein, and thalamo-striate vein) When entering the third ventricle, be careful not to damage the structures surrounding foramen of Monro. (Particularly the fornix and venous angle) The structures to be checked in the third ventricle (Figure 5)

Fig. 5 Endoscopic view of the floor of 3rd ventricle (left upper: anterior, right bottom: posterior)

Endoscopic Third Ventriculostomy (ETV)

1477

(Mammillary bodies, tuber cinerum, infundibular recess, optic chiasm, lamina terminalis, Aqueduct of sylvius, posterior commissure, and pineal body)

Surgical manipulation II - Third ventriculostomy [1] Ventriculostomy in the direction of the infundibular recess is fundamental. The center of triangle linking the bilateral mammillary bodies and the infundibular recess is the landmark. (Figure 6) [2] Puncture the same point bluntly towards the clivus. Matters that require attention at this point. • Posterior to the triangle (mammillary body): the basilar artery and thalamic perforators can be damaged. • Exterior to the triangle: the hypothalamic area, oculomotor nerve, posterior communicating artery, and its perforators can be damaged. • Anterior to the triangle, damage to infundibular recess: diabetes insipidus may occur. • In principle, do not make a puncture with electrical current. [3] Puncture the membrane of Lilliquist beneath the third ventricular floor at the same time. • The membrane of the third ventricular floor is thin in chronic hydrocephalus (Figure 7). • The membrane of the third ventricular floor is thick in acute hydrocephalus. (Bradycardia may occur when the third ventricular base is forcibly pushed.)

Fig. 6 Landmarks of ETV O.C.: optic chiasm, I.R.: infundibular recess, M.B.: mammillary body Cl: Clivus, B.S.: brain stem B.A.: basilar artery, arrow: the projection of endoscope

Fig. 7 Thin 3rd ventricular floor of severe hydrocephalus

1478 Miscel Ianeous [4] Expand the perforated stoma with a balloon catheter (a diameter of 4-5 mm as the target) [5] Check the structures (e.g., basilar artery) directly below the stoma [6] To and fro movement of the third ventricular floor following the ventriculostomy is the confirmation for patent stoma. [7] Most small hemorrhages upon perforation are naturally stopped by irrigation with perfusion fluid. Upon arterial hemorrhage, do not move the endoscope randomly. Maintain the irrigation route. Ask the anesthetist for low blood pressure management. If coagulants are used to arrest a hemorrhage, do so with a secure field of vision after sufficient cleansing. If a hematoma is created in the form of an intraventricular hemorrhage and the hemorrhage is arrested, attempt to evacuate the hematoma may be done. If it is difficult to do so, place a ventricular drain. [8] Removing the endoscope: Confirmation of hemostasis. With a small amount of hemorrhage during the surgery, ventricular drainage is not necessary. In case of persistence of air in the ventricle, replace it with perfusion fluid. [9] Removing the sheath and suturing the dura mater : Be careful to prevent the cerebrospinal fluid from leaking (particularly in children). It is desirable to suture as much as possible [10] Closing the surgical incision

Postoperative management of Third ventriculostomy 1. Acute stage (1) Early mobilize the patient (walking is possible the next day) (2) Postoperative intracranial hypotension-heaviness of the head and nausea (mostly transient) (3) Postoperative pyrexia (effect of perfusion fluid, improves within 2-3 days; steroids may be effective in the treatment) 2. Chronic phase (1) Confirmation of ETV flow by MRI (2) Follow up on the ventricular size and the ETV flow for a long period (3) Pay attention to sudden deterioration due to ETV chronic phase occlusion.

Conclusion The neuroendoscopic third ventriculostomy is safe, minimally invasive and extremely useful treatment modality for non-communicating hydrocephalus. If conducted in carefully selected patients, it can replace conventional ventriculo-peritoneal shunt operation for non-communicating hydrocephalus.

1479

Neurosurgeon training in China ZHAO YUANLI, JIZONG ZHAO Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University Key words: neurosurgery, neurosurgeon, training, China

Neurosurgery was introduced in China in 1930s by Dr. Song-tao Guan and Dr. Yicheng Zhao. Later, in 1949, Dr. Guan left for the USA, and Dr. Zhao stayed in China to train Chinese neurosurgeons and contributed significantly to the development of modern neurosurgery there. Yi-Cheng Zhao was trained in neurosurgery at the Montreal Neurological Institute by Wilder Penfield in 1938. He set up the first independent neurosurgical departments in Tianjin (1952) and in Beijing (1954). He was also enthusiastic about training neurosurgeons. More than 200 students have been trained by him, and most of them have set up centers in different cities in China. Within almost seven decades of development, the neurosurgery in China has progressed greatly; the same is true about training for neurosurgeon. In 1995 Standard Surgical Training (SST) which was structured by the Chinese Ministry of Health was launched at 2400 bases, with 52,000 trainees completing training at these bases, The clinical resident training programme aimed to set the standards for postgraduate surgical training. In 1999 the Chinese government started to implement a national licensing exam for medical graduates. However, there is still no national accreditation body to regulate and coordinate postgraduate medical training. Currently, China’s health care system is separated into three tiers and only the top two tiers can apply to the government to become an SST center. The SST is organized into two stages: the first stage lasts three year. After graduation from medical college, medical interns first rotate through one year of internal medicine and surgery, and then they take national licensing exam. After passing their licensing exam, medical interns rotate on various surgery services for 18 months. In the current year these are General Surgery, Cardiac and Thoracic Surgery, Orthopedics, Urinary Surgery. And then two months each are spent in Neurology, Anesthesia, and Radiology. After which an assessment is organized by the hospitals’ administrative body and professors testing clinical skills and ability to manage different surgical diseases. Depending on posts available, trainees who pass and get three- year resident certification can then become a neurosurgical trainee and enter stage two of the SST. Stage two lasts for a duration of two years in which trainee is required to complete rotation in general neurosurgery, including Neurovascular, Brain Tumors, Skull Base Surgery, Epilepsy, Spine, Pediatrics, Stereotactic Radiosurgery, Trauma. In the last six months the second stage residents should act as chief residents. After completing the two steps, the residents will have examinations for certificate by the national board of neurosurgery who set up its first national certificate examination in 2006 in Beijing. The certificate examination is held annually. The residents passing the examinations will begin their neurosurgery career as attending doctors. In addition to the examinations, there are other rules for continuous medical educations. For example, each year

1480 Miscel Ianeous neurosurgeons are also required to obtain certain credits by participating in certain academic conferences or training courses. As attending doctors, trainees are eligible to apply for specialist positions. As specialists, they are required to complete the specialist surgical exam, testing surgical cases as well as English and Computer Science. The promotion from Attending to vice-Chief and then Chief neurosurgeon requires both plenty of clinical practice and academic paper publication. For promotion the surgeon also needs to pass examinations by the board of neurosurgery and surgery. (figure 1) To make qualified doctors and keep the pace with ever advancing techniques to offer more satisfactory medical service are important parts of work for Chinese Neurosurgical Society (CNS). In large cities, such as Beijing and Shanghai, the continuous medical education is held regularly for tens of hours annually, but they can’t reach the rural areas easily. Like economic development imbalance in China, students graduating from different medical colleges have unequal training opportunities in different regions. Not all the doctor can enters the SST. In poor rural countryside areas the hospitals are too small and lack the basic equipment and resources necessary to set up adequate training programmes, and the doctors who can not go to SST center to get training, they only learn from senior doctors although senior doctor’ experiences is still limited and lack standardization. As 57% of China’s population resides in the rural countryside, Training more qualified neurosurgeons is still a big challenge for government and Chinese Neurosurgical Society,

Fig. 1 Neurosurgeon training in China

1481

Educational laboratories for young neurosurgeons Ling Feng Beijing Xuanwu Hospital, China Key words: Microsurgery, neurosurgery, training, Laboratory, Techniques

Role of the laboratory on a resident’s professional training Training should enable the neurosurgeon to work easily unlessly through the operating microscope. In order to acquire this, it is essential that adequate laboratory training should be used. Different from in the arts a faulty result can be destroyed or replaced, in surgery, it is the patient who pays for a defective procedure. So, it is a moral and ethical need to find a way to shorten the learning curve of junior surgeons. Moreover, the laboratory offers the chance to practice without strict time limits, psychological pressures, and medicolegal responsibilities which can be derived from incidental mistakes. Stress, anxiety, hurry, and inexperience are some of the worst enemies for a neurosurgeon. They cause inaccuracy, insecurity, and tremors which represent an absolute drawback to the execution of those delicate and precise movements mandatory in neurosurgery.

Introduction Donaghy et al. have been the first to introduce microsurgery in the neurological surgery performing the first microsurgical middle cerebral artery endarterectomy in 1962. He settled up a laboratory for vivisection at the University of Vermont in 1948. He started using more and more accurate and small instruments,as well as 10.0 and 11.0 suture strands. Practicing, he modified camber and diameter of the needles. He instructed Dr. Littman on how to modify surgical microscopes to enhance their handling and to fit them to requirements of vascular surgeons. Many eminent American and European surgeons built up their skills in his laboratory. Among them, there was Yasargil who developed the microsurgical techniques now unanimously considered the milestones of neurosurgery. Nowadays, the modern neurosurgery is based on microsurgery. During the last four decades, the use of the microscope led to an extraordinary reduction of both morbidity and mortality. Therefore, a complete training for young microsurgeons should include laboratory sessions where they can perform microsurgical techniques until excellence. Nevertheless, a laboratory is the optimal environment where they can plan new techniques and procedures and use new materials. The primary target of this works lies in supplying the readers with a compendium which would allow every authorized institution to create a laboratory and to start a microsurgical training program.

1482 Miscel Ianeous

Laboratory 1. The room should be well ventilated. A pleasant environment improves work efficiency. The best results can be obtained in a laboratory that all equipment work well at any time, and the equipment and techniques are the same as those used in the operating room. 2. The table should be large enough to place all the instrumentation, with a power source for an electrically driven drill or a coagulator and a trap large enough so that prolonged training can be performed without interruption for cleaning. And it should be suitable for both right hand users and left hand users. 3. The chair should be comfortable, adjustable for individual preference for height. Choose a chair with castors for mobility so that the trainee can move closer or far away form the table for proper extension and support of the arms. 4. An video recording system should be applied to the microscope allowing the tutor to follow the apprentice and to record the sessions; 5. A bench should be collocated in a divided room with someone who deals with litters, cages, food, and postoperative drugs .

Educational laboratories for young neurosurgeons

1483

Microscope Microscope is an essential instrument in neurosurgery.The first step in microsurgery is to acquire skull and proficiency in the use of the mobile operating microscope. This includes understanding of the basic optical and mechanical construction of the microscope and its principles as applied to neurosurgical procedures. The surgeron must be competent in the assembly and the dismantling of the microscope into its component parts. He or she should be familiar with the common types of mechanical and electrical failures that can affect the system. Balanced positioning of the microscope requires a working knowledge of the counterbalances and practice in precise alignment and balance. Interchangeable accessories for the microscope include different binocular eyepieces, various objective, and other attachments, such as hand or mouth switches for controlling horizontal, vertical, and translational movement. A Zeiss surgical microscope with adjustable focus and magnifying lens (to ×40) are used in microsurgical training center in China International Neuroscience Institute (China INI).

Drill Ideally, the drill should resemble the equipment in the operating room. Any drill with a variety of burr sizes will suffice, but reliability should be considered. Both of the cutting and diamond burrs are available and cutting burrs should be sharp.

Suction – Irrigation Equipment Adequate suction – irrigation is necessary in cadaveric training. Suction – irrigation removes bone dust that blocks view and becomes clogged between the flukes of the burrs. Besides it can cool the surface of the drill, avoiding thermal injury and prolonging lifetime of the burrs.

1484 Miscel Ianeous

Cadaver Head Holder House-Urban stainless steel bone holder is easily cleaned, and allows movement of the cadaver to any desired position for dissection. Cadaver’s head used in training dissection is fixed with a holder of similar shape and size.The holder should always be placed in a large trap that will contain spilt irrigation fluids and accumulated bone dust. The trap should be large enough and easily cleaned.

Instrumentation and materials Macroset includes: a scalpel, two pairs of forceps, scissors, and cotton fioc®. Microset comprises a pair of microscissors, one microscalpel or sharp point, two pairs of microforceps (possibly with a variable width of the tip), and one vascular approximator, two small straight clips, one clip applier and one microneedle holder (Table 1).

Educational laboratories for young neurosurgeons

1485

Threads 3.0 monofilament–silk for skin and muscle 4.0–6.0 monofilament for vessel ligatures 8.0–11.0 for microvascular sutures and anastomoses.

Materials Rodents (rats and mice) and cadavor heads have been used for vivisection.

Ethical issues and institutional authorization The drugs to be administered intraoperatively and postoperatively should assure immobilization and analgesia of the rodents during interventions and to provide an optimal state of absence of pain in the postoperative period. The training program should be approved by local ethical committee after the analysis of the following documents:

Microsurgical Laboratory Training Program This is aimed at enabling the surgeon to become familiar and proficient in the following: 1. The use of instrumentation and other apparatuses Setting up the microscope and its various components: The optical system The mechanical system The lighting system Balance and mobility Photography, film and video cameras Suction and bipolar coagulation apparatus Bone drill (electric / air) (use and assembly)

1486 Miscel Ianeous 2. Surgical training Suturing, using soft tubes Dissection of arteries and veins of the rat Abdomen: aorta – vena cava Neck: carotid artery – jugular vein Circle of Willis: basilar artery, cortical arteries Reconstruction of arteries and veins (extra – and intracranial) Craniotomies and laminectomies (brain and spinal cord surgery) 3. Anatomy of the skull-brain base and of the brain Human cadaver and studies a) Skull base (sella, cavernous sinus, optic canal, orbits) b) Brain base (vessels, cranial nerves and cisterns) c) Brain (cisterns, sulci, fissures, gyri, white matter and connecting fibers, central nuclei, basal ganglia, limbic lobe, ventricular system) 4. Research related to microsurgery: physiology, molecular biology, immunology 5. Visual learning: a) Observing surgery in the operating room, assisting with the preparation and positioning of the patient and at wound closure b) Observing video tapes of surgical procedures 6. Practicing on simulators and operating beforehand on “virtual reality” systems.

Microsurgery Training Course Description Three levels of training are available 1. Basic microsurgical training 2. Advanced microsurgical trainin 3. Observation of clinical microsurgery.˜

Basic Microsurgical Courses 1. Basic preparation for learning microsurgery • Microsurgical equipment set-up • Familiarity with operating microscope • Microsurgical instrument care • Handling microsurgical sutures and instruments 2. Basic Microsurgical technique Learning to handle microsurgical instruments • Hand position when holding instruments • Control of hand tremor • Use of the microsurgical needle holder and forceps • Needle-holding position (Forehand or Backhand) .Basic suturing technique with a practice card • Passing the needle through tissue • Tying a microsurgical knot

Educational laboratories for young neurosurgeons

1487

• Learning to use Silicone tubing for end-to-end anastomosis with microdot technique • Developing basic microsurgical suturing techniques for both hands

Advanced Microsurgical Course Model: small rat (30~40g) 1. Abdominal aorta arterial end-to-end and end-to-side anastomoses 2. Inferior vena cava veinous end-to-end anastomoses 3. Common internal carotid arterial end-to-end and end-to-side anastomoses 4. Common iliac arterial end-to-end anastomoses 5. Femoral arterial and venous end-to-end anastomoses 6. Kidney transplantation 7. Superior and inferior mesenteric arterial and venous end-to-end anastomoses 8. Free flap transfer (involves dissecting the flap and vascular pedicle, resituating the flap in the contralateral inguinal region or in the neck, revascularizing the flap by arterial and venous anastomosis)

Live surgical demonstrations Observation of intracranial aneurysm clipping and EC-IC grafting operation Laboratory training is very useful for the learning process of young microsurgeons. Nonetheless, it would represent an outstanding medium for research in neurosurgery for senior surgeons too. All the participants will noticed an improvement of their surgical skills. They will be more firm and confident in the operating room and less anxious. All the trainees executed all the exercises foreseen by the course, testifying that even the most difficult exercises are more accessible with practice, regardless of the individual predispositions and deftness at the starting point.