Manual of peripheral nerve surgery from the basics to complex procedures 9783132409552, 3132409553, 9783132410015, 3132410012

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TPS 19.5 x 27 - 2 | 27.07.17 - 13:12

TPS 19.5 x 27 - 2 | 27.07.17 - 13:12

TPS 19.5 x 27 - 2 | 27.07.17 - 13:12

Manual of Peripheral Nerve Surgery From the Basics to Complex Procedures Mariano Socolovsky, MD Head Peripheral Nerve and Brachial Plexus Unit Department of Neurosurgery University of Buenos Aires School of Medicine Buenos Aires, Argentina Chairman, WFNS Peripheral Nerve Surgery Committee Lukas Rasulic, MD, PhD Professor and Head Department of Peripheral Nerve Surgery, Functional Neurosurgery and Pain Management Surgery, Clinic for Neurosurgery, Clinical Center of Serbia School of Medicine University of Belgrade Belgrade, Serbia Vice Chairman, WFNS Peripheral Nerve Surgery Committee Rajiv Midha, MD, MSc, FRCSC, FAANS, FCAHS Professor and Head Department of Clinical Neurosciences University of Calgary Calgary, Alberta, Canada Peripheral Nerve Section Associate Editor, Neurosurgery and World Neurosurgery Vice Chairman, WFNS Peripheral Nerve Surgery Committee Debora Garozzo, MD Head Brachial Plexus and Peripheral Nerve Surgery Unit Neurospinal Hospital Dubai, UAE Vice Chairman, WFNS Peripheral Nerve Surgery Committee 267 illustrations

Thieme Stuttgart • New York • Delhi • Rio de Janeiro

Library of Congress Cataloging-in-Publication Data Names: Socolovsky, Mariano, editor. | Rasulic, Lukas, editor. | Midha, Rajiv, editor. | Garozzo, Debora, editor. Title: Manual of peripheral nerve surgery : from the basics to complex procedures / [edited by] Mariano Socolovsky, Lukas Rasulic, Rajiv Midha, Debora Garozzo. Description: Stuttgart ; New York : Thieme, 2017. | Includes bibliographical references and index. Identifiers: LCCN 2017029566 (print) | LCCN 2017030596 (ebook) | ISBN 9783132410015 | ISBN 9783132409552 (hardcover) | ISBN 9783132410015 (eISBN) Subjects: | MESH: Peripheral Nervous System Diseases– surgery | Peripheral Nerves–surgery Classification: LCC RD124 (ebook) | LCC RD124 (print) | NLM WL 520 | DDC 617.4/83–dc23 LC record available at https://lccn.loc.gov/2017029566 Illustrators: Luis Domitrovic, León, Castilla, Spain Martin Montalbetti, Buenos Aires, Argentina

© 2018 by Georg Thieme Verlag KG Thieme Publishers Stuttgart Rüdigerstrasse 14, 70469 Stuttgart, Germany +49 [0]711 8931 421, [email protected] Thieme Publishers New York 333 Seventh Avenue, New York, NY 10001 USA +1 800 782 3488, [email protected]

Important note: Medicine is an ever-changing science undergoing continual development. Research and clinical experience are continually expanding our knowledge, in particular our knowledge of proper treatment and drug therapy. Insofar as this book mentions any dosage or application, readers may rest assured that the authors, editors, and publishers have made every effort to ensure that such references are in accordance with the state of knowledge at the time of production of the book. Nevertheless, this does not involve, imply, or express any guarantee or responsibility on the part of the publishers in respect to any dosage instructions and forms of applications stated in the book. Every user is requested to examine carefully the manufacturers’ leaflets accompanying each drug and to check, if necessary in consultation with a physician or specialist, whether the dosage schedules mentioned therein or the contraindications stated by the manufacturers differ from the statements made in the present book. Such examination is particularly important with drugs that are either rarely used or have been newly released on the market. Every dosage schedule or every form of application used is entirely at the user’s own risk and responsibility. The authors and publishers request every user to report to the publishers any discrepancies or inaccuracies noticed. If errors in this work are found after publication, errata will be posted at www.thieme.com on the product description page. Some of the product names, patents, and registered designs referred to in this book are in fact registered trademarks or proprietary names even though specific reference to this fact is not always made in the text. Therefore, the appearance of a name without designation as proprietary is not to be construed as a representation by the publisher that it is in the public domain.

Thieme Publishers Delhi A-12, Second Floor, Sector-2, Noida-201301 Uttar Pradesh, India +91 120 45 566 00, [email protected] Thieme Publishers Rio, Thieme Publicações Ltda. Edifício Rodolpho de Paoli, 25º andar Av. Nilo Peçanha, 50 – Sala 2508 Rio de Janeiro 20020-906, Brasil +55 21 3172 2297 Cover design: Thieme Publishing Group Cover illustration: Martin Montalbetti, Buenos Aires, Argentina Typesetting by Thomson Digital, India Printed in India by Replika Press Private Ltd. ISBN 978-3-13-240955-2 Also available as an e-book: eISBN 978-3-13-241001-5

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This book, including all parts thereof, is legally protected by copyright. Any use, exploitation, or commercialization outside the narrow limits set by copyright legislation without the publisher’s consent is illegal and liable to prosecution. This applies in particular to photostat reproduction, copying, mimeographing or duplication of any kind, translating, preparation of microfilms, and electronic data processing and storage.

TPS 19.5 x 27 - 2 | 08.08.17 - 16:54

I dedicate this book to my beloved wife, Veronica, my partner in the fascinating journey of life; to my children, Federico, Valentina, and Francisco, who give reason to my life; and to my parents, Eddie and Mariela, who gave me life and continued to lovingly and generously guide me through it for many years. Mariano Socolovsky, MD I dedicate this book to my driving force, my family: my wife Katarina, our daughter Milica, and our son Mihailo; my parents: my father Grujica and my mother Dusanka; my sister Katarina; my mentor, Prof. Dr. Miroslav Samardzic, and my associates; and last but not the least, my patients with peripheral nerve disorders. Lukas Rasulic, MD, PhD I dedicate this book to my brother, Samir, who, despite his shortened life, taught me how to live and love. Rajiv Midha, MD, MSc, FRCSC, FAANS, FCAHS I dedicate this book to Vita and the everlasting memory of Filippo, for the unconditional love and constant support I received from them since I was brought into this world: I could have not found better parents and I would like to thank them for the privileged life they bestowed upon me. To my patients: I learned a lot from them, on science and surgery, but most of all, on life. I would have never become the woman I am without them all. Debora Garozzo, MD

TPS 19.5 x 27 - 2 | 27.07.17 - 13:12

Contents Foreword

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

xiv

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

xv

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

xvi

Miguel Arraez

Foreword Madjid Samii

Foreword

Franco Servadei

Foreword

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

xvii

Robert J. Spinner

1

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xviii

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xix

Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

xx

Nerve Anatomy of the Upper Limbs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

Gilda Di Masi and Gonzalo Javier Hugo Bonilla 1.1

Supraclavicular Brachial Plexus . . . . . . .

1.1.1

Collateral Branches of the Supraclavicular Brachial Plexus . . . . . . . . . . . . . . . . . . . . . . .

2

1.2

Infraclavicular Brachial Plexus . . . . . . . .

3

1.2.1

Collateral Branches of the Infraclavicular Brachial Plexus . . . . . . . . . . . . . . . . . . . . . . .

3

2

1

1.3

1.3.1 1.3.2 1.3.3 1.3.4 1.3.5

Terminal Branches of the Brachial Plexus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

4

Radial Nerve . . . . . . . . . . . . . . . . . . . . . . . . . Median Nerve . . . . . . . . . . . . . . . . . . . . . . . . Ulnar Nerve . . . . . . . . . . . . . . . . . . . . . . . . . . Musculocutaneous Nerve . . . . . . . . . . . . . . Axillary Nerve . . . . . . . . . . . . . . . . . . . . . . . .

4 5 6 7 8

References . . . . . . . . . . . . . . . . . . . . . . . . . .

8

Surgical Anatomy and Approaches to the Nerves of the Lower Limb

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

10

Sciatic Nerve . . . . . . . . . . . . . . . . . . . . . . . . . Terminal Branches of the Sciatic Nerve . . .

14 15

References . . . . . . . . . . . . . . . . . . . . . . . . . .

16

18

Fernando Martínez and Federico Salle 2.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

10

2.2

Lumbar Plexus . . . . . . . . . . . . . . . . . . . . . . .

10

2.2.1 2.2.2

Inguinal Group . . . . . . . . . . . . . . . . . . . . . . . Femoral Group . . . . . . . . . . . . . . . . . . . . . . .

11 11

2.3

Sacral Plexus . . . . . . . . . . . . . . . . . . . . . . . .

14

3

Nerve Injuries: Anatomy, Pathophysiology, and Classification . . . . . . . . . . . . . . . . . . . .

2.3.1 2.3.2

Bassam M. J. Addas 3.1

Anatomy of the Peripheral Nerves . . . .

18

3.3

Laceration Injury . . . . . . . . . . . . . . . . . . . . .

20

3.2

Traction Injury . . . . . . . . . . . . . . . . . . . . . . .

19

3.4

Compression/Pressure Injury . . . . . . . . .

20

vii

Contents Thermal Injury . . . . . . . . . . . . . . . . . . . . . . . Radiation Injury . . . . . . . . . . . . . . . . . . . . . .

22 23

References . . . . . . . . . . . . . . . . . . . . . . . . . .

23

Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb . . . . . . . . . . . . . . . . . . .

24

3.5

Injection Injury . . . . . . . . . . . . . . . . . . . . . .

22

3.6

Rare Forms of Peripheral Nerve Injuries

22

3.6.1

Electrical Injuries . . . . . . . . . . . . . . . . . . . . .

22

4

3.6.2 3.6.3

Javier Robla Costales, Luis Domitrovic, David Robla Costales, Javier Fernández Fernández, and Javier Ibáñez Plágaro 4.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

24

4.2

Musculocutaneous Nerve . . . . . . . . . . . .

4.3 4.3.1 4.3.2 4.3.3

24

4.4.1 4.4.2 4.4.3

Motor Innervation . . . . . . . . . . . . . . . . . . . . Sensory Innervation . . . . . . . . . . . . . . . . . . . Clinical Findings . . . . . . . . . . . . . . . . . . . . . .

32 34 35

Median Nerve . . . . . . . . . . . . . . . . . . . . . . .

26

4.5

Radial Nerve . . . . . . . . . . . . . . . . . . . . . . . .

36

26 30

4.5.1 4.5.2 4.5.3

Motor Innervation . . . . . . . . . . . . . . . . . . . . Sensory Innervation . . . . . . . . . . . . . . . . . . . Clinical Findings . . . . . . . . . . . . . . . . . . . . . .

36 39 40

4.3.4

Motor Innervation . . . . . . . . . . . . . . . . . . . . Sensory Innervation . . . . . . . . . . . . . . . . . . . Martin-Gruber and Riche-Cannieu Anastomoses . . . . . . . . . . . . . . . . . . . . . . . . . Clinical Findings . . . . . . . . . . . . . . . . . . . . . .

30 31

Further Readings . . . . . . . . . . . . . . . . . . . .

41

4.4

Ulnar Nerve . . . . . . . . . . . . . . . . . . . . . . . . .

31

Clinical Aspects of Traumatic Peripheral Nerve Lesions in the Lower Limb. . . . . . .

42

5

Yuval Shapira and Shimon Rochkind 5.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

42

5.4.2

Injuries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

46

5.2

Lumbosacral Plexus . . . . . . . . . . . . . . . . . .

42

5.5

Femoral Nerve . . . . . . . . . . . . . . . . . . . . . .

46

5.3

Sciatic, Tibial, and Peroneal Nerve . . . . .

42

5.3.1 5.3.2 5.3.3 5.3.4

42 43 45

Anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Femoral Nerve Lesions . . . . . . . . . . . . . . . . . Saphenous Nerve Lesions. . . . . . . . . . . . . . . The Symptoms and Signs of Femoral Nerve Involvement . . . . . . . . . . . . . . . . . . . .

46 46 46

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . .

47

5.3.5

Anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Injuries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Common Sites and Types of Nerve Lesions Symptoms and Signs of Common Peroneal Nerve Injury . . . . . . . . . . . . . . . . . . . . . . . . . . Symptoms and Signs of Tibial Nerve Injury

5.5.1 5.5.2 5.5.3 5.5.4

References . . . . . . . . . . . . . . . . . . . . . . . . . .

47

5.4

Obturator Nerve . . . . . . . . . . . . . . . . . . . . .

46

5.4.1

Anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

46

Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations . . . . . . . . . . . . . . . . . . . . .

48

6

45 46

5.6

46

Carlos Alberto Rodríguez Aceves, Miguel Domínguez Páez, and Victoria E. Fernández Sánchez

viii

6.1

Basic Considerations . . . . . . . . . . . . . . . . .

48

6.2.2

Demyelination . . . . . . . . . . . . . . . . . . . . . . . .

48

6.1.1 6.1.2

Anatomical Characteristics . . . . . . . . . . . . . Physiological Characteristics . . . . . . . . . . . .

48 48

6.3

EDSs for Preoperative Evaluations . . . . .

49

Pathophysiology . . . . . . . . . . . . . . . . . . . . .

48

6.3.1 6.3.2

6.2.1

Axonal Damage . . . . . . . . . . . . . . . . . . . . . . .

48

6.3.3

Technical Considerations . . . . . . . . . . . . . . . Nerve Conduction Studies/ Electroneurography . . . . . . . . . . . . . . . . . . . Electromyography . . . . . . . . . . . . . . . . . . . .

49

6.2

49 51

Contents Electrophysiological Findings with Different Types of Nerve Injury . . . . . . . .

52

6.6.2 6.6.3

Intraoperative Monitoring Techniques . . . Surgical Procedures . . . . . . . . . . . . . . . . . . .

54 56

6.5

When Are EDSs Indicated? . . . . . . . . . . . .

53

6.7

EDSs for Postoperative Evaluations . . . .

56

6.6

EDSs for Intraoperative Evaluations . . .

53

6.8

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . .

57

6.6.1

Lesions-in-continuity . . . . . . . . . . . . . . . . . .

53

References . . . . . . . . . . . . . . . . . . . . . . . . . .

57

Magnetic Resonance Neurography and Peripheral Nerve Surgery . . . . . . . . . . . . . . . .

59

6.4

7

Daniela Binaghi and Mariano Socolovsky 7.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

59

7.4

Tumors . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

62

7.2

Trauma . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

59

7.5

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . .

63

7.3

Entrapment Neuropathies . . . . . . . . . . . .

62

References . . . . . . . . . . . . . . . . . . . . . . . . . .

64

Ultrasound in Peripheral Nerve Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

65

8

Maria Teresa Pedro and Ralph W. König 8.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

65

8.4

Trauma . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

68

8.2

How to Start (Basic Principles) . . . . . . . .

65

8.4.1 8.4.2

Preoperative HRU . . . . . . . . . . . . . . . . . . . . . Intraoperative HRU . . . . . . . . . . . . . . . . . . .

68 68

8.3

Compression Neuropathies . . . . . . . . . . .

66

8.5

Tumor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

69

8.3.1

Compression Neuropathies of the Upper Limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Compression Neuropathies of the Lower Limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Recurrent Compression Neuropathies . . . .

References . . . . . . . . . . . . . . . . . . . . . . . . . .

73

Surgical Repair of Nerve Lesions: Neurolysis and Neurorrhaphy with Grafts or Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

74

8.3.2 8.3.3

9

66 66 66

Sudheesh Ramachandran and Rajiv Midha 9.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

74

9.6.2

Allografts . . . . . . . . . . . . . . . . . . . . . . . . . . . .

78

9.2

Evaluation and Approach . . . . . . . . . . . . .

74

9.7

Nerve Tubes . . . . . . . . . . . . . . . . . . . . . . . . .

79

9.3

General Principles of Nerve Repair . . . .

75

9.7.1 9.7.2

Autologous Conduits . . . . . . . . . . . . . . . . . . Artificial Conduits . . . . . . . . . . . . . . . . . . . . .

80 80

9.4

Neurolysis . . . . . . . . . . . . . . . . . . . . . . . . . . .

75

9.8

Post-op Management . . . . . . . . . . . . . . . .

81

9.5

Direct Repair . . . . . . . . . . . . . . . . . . . . . . . .

75

9.9 9.5.1 9.5.2

End-to-End Repair . . . . . . . . . . . . . . . . . . . . End-to-Side Repair . . . . . . . . . . . . . . . . . . . .

75 76

Tissue Engineering and Future of Nerve Repairs . . . . . . . . . . . . . . . . . . . . .

81

References . . . . . . . . . . . . . . . . . . . . . . . . . .

82

9.6

Nerve Grafting . . . . . . . . . . . . . . . . . . . . . .

77

9.6.1

Autografts . . . . . . . . . . . . . . . . . . . . . . . . . . .

77

ix

Contents

10

Timing in Traumatic Peripheral Nerve Lesions

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

84

10.5.1 10.5.2 10.5.3 10.5.4

Open Wounds: Laceration Mechanism . . . Open Injuries: Gunshot Wounds . . . . . . . . Closed Injuries: Traction or Compression . Closed Injuries: Special Situations . . . . . . .

86 87 87 88

10.6

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . .

89

References . . . . . . . . . . . . . . . . . . . . . . . . . .

89

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

90

Leandro Pretto Flores 10.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

84

10.2

Basic Science as an Aid for Taking an Important Decision . . . . . . . . . . . . . . . . . .

84

Initial Evaluation of a Peripheral Nerve Injury . . . . . . . . . . . . . . . . . . . . . . . . .

85

10.3

10.4

10.5

11

Causes of Traumatic Peripheral Nerve Injury . . . . . . . . . . . . . . . . . . . . . . . . .

85

Specific Surgical Timing . . . . . . . . . . . . . .

86

Outcomes in the Repair of Nerve Injuries Lukas Rasulic and Miroslav Samardzic

11.1

Prognostic Factors . . . . . . . . . . . . . . . . . . .

90

11.2

General Grading Systems . . . . . . . . . . . . .

92

11.1.1 11.1.2 11.1.3 11.1.4 11.1.5

Patient Age . . . . . . . . . . . . . . . . . . . . . . . . . . . Characteristics of the Nerve . . . . . . . . . . . . Characteristics of the Nerve Injury . . . . . . . Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Postoperative Rehabilitation . . . . . . . . . . . .

90 90 91 92 92

11.2.1 11.2.2

Upper Extremity Repair . . . . . . . . . . . . . . . . Lower Extremity Repairs . . . . . . . . . . . . . . .

94 96

References . . . . . . . . . . . . . . . . . . . . . . . . . .

97

12

Gunshot and Other Missile Wounds to the Peripheral Nerves

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

98

Miroslav Samardzic and Lukas Rasulic 12.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

98

12.4

Indications for and Timing of Surgery . . .

100

12.2

Clinical Characteristics . . . . . . . . . . . . . . .

99

12.5

Results and Prognosis . . . . . . . . . . . . . . . .

101

12.2.1 12.2.2

Brachial Plexus . . . . . . . . . . . . . . . . . . . . . . . Peripheral Nerves . . . . . . . . . . . . . . . . . . . . .

99 99

12.5.1 12.5.2

Brachial Plexus . . . . . . . . . . . . . . . . . . . . . . . Peripheral Nerves . . . . . . . . . . . . . . . . . . . . .

101 102

12.3

Characteristics of Nerve Lesions . . . . . .

99

12.6

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . .

103

12.3.1 12.3.2

Brachial Plexus . . . . . . . . . . . . . . . . . . . . . . . Peripheral Nerves . . . . . . . . . . . . . . . . . . . . .

99 100

References . . . . . . . . . . . . . . . . . . . . . . . . . .

103

13

Compressive Lesions of the Upper Limb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

105

Gregor Antoniadis and Christine Brand

x

13.1

Median Nerve . . . . . . . . . . . . . . . . . . . . . . .

105

13.3

Radial Nerve . . . . . . . . . . . . . . . . . . . . . . . .

13.1.1 13.1.2

Carpal Tunnel Syndrome . . . . . . . . . . . . . . . Median Nerve Entrapment at the Elbow . .

105 107

13.3.1

13.2

Ulnar Nerve . . . . . . . . . . . . . . . . . . . . . . . . .

109

13.3.2

13.2.1 13.2.2

Ulnar Nerve Entrapment at the Elbow . . . . Ulnar Nerve Entrapment at the Wrist (Guyon’s Syndrome) . . . . . . . . . . . . . . . . . . .

109

Radial Nerve Entrapment at the Elbow (Posterior Interosseous Nerve Syndrome) . . . . . . . . . . . . . . . . . . . . . . . . . . . Radial Sensory Nerve Entrapment (Wartenberg’s Syndrome, Cheiralgia Paresthetica) . . . . . . . . . . . . . . . . . . . . . . . . .

111

13.4

Suprascapular Nerve Entrapment . . . . .

111

111

112 112

Contents 13.4.1 13.4.2 13.4.3

14

Clinical Presentation . . . . . . . . . . . . . . . . . . Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Surgical Strategy . . . . . . . . . . . . . . . . . . . . . .

112 113 113

References . . . . . . . . . . . . . . . . . . . . . . . . . .

Compressive Lesions of the Lower Limb and Trunk

113

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

115

Ilioinguinal Nerve/Iliohypogastric Nerve/ Genitofemoral Nerve . . . . . . . . . . . . . . . . . . Femoral Nerve . . . . . . . . . . . . . . . . . . . . . . . . Obturator Nerve . . . . . . . . . . . . . . . . . . . . . . Pudendal Nerve/Pudendal Neuralgia . . . . .

122 122 124 124

References . . . . . . . . . . . . . . . . . . . . . . . . . .

126

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

128

Christian Heinen and Thomas Kretschmer 14.1

Nerves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

115

14.1.5

14.1.1 14.1.2 14.1.3 14.1.4

Sciatic Nerve . . . . . . . . . . . . . . . . . . . . . . . . . Peroneal Nerve . . . . . . . . . . . . . . . . . . . . . . . Tibial Nerve . . . . . . . . . . . . . . . . . . . . . . . . . . Lateral Femoral Cutaneous Nerve (Meralgia Paraesthetica). . . . . . . . . . . . . . . .

115 117 120

14.1.6 14.1.7 14.1.8

15

Thoracic Outlet Syndrome

121

Mariano Socolovsky, Daniela Binaghi, and Ricardo Reisin 15.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

128

15.2

Diagnosis and Management of TOS . . .

128

15.2.1 15.2.2

Important Concepts Regarding TOS . . . . . . Important Concepts in DNTOS . . . . . . . . . .

128 131

16

15.3

What Does the Literature Say about TOS? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

133

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . .

133

References . . . . . . . . . . . . . . . . . . . . . . . . . .

133

Traumatic Brachial Plexus Lesions: Clinical Aspects, Assessment, and Timing of Surgical Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

135

15.4

Mario G. Siqueira and Roberto S. Martins 16.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

135

16.2

Types and Mechanisms of Injury . . . . . .

135

16.3

Location of the Injury . . . . . . . . . . . . . . . .

136

16.4

Pain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

137

16.5

Evaluation of Brachial Plexus Function and Diagnosis . . . . . . . . . . . . . . . . . . . . . . .

137

Physical Evaluation . . . . . . . . . . . . . . . . . . .

137

16.5.1

17

16.5.2 16.5.3

Image Studies . . . . . . . . . . . . . . . . . . . . . . . . Electrodiagnostic Studies . . . . . . . . . . . . . .

137 139

16.6

Indications for Surgery . . . . . . . . . . . . . . .

139

16.7

Timing of Surgery . . . . . . . . . . . . . . . . . . .

139

16.8

Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . .

140

References . . . . . . . . . . . . . . . . . . . . . . . . . .

140

Traumatic Brachial Plexus Injuries: Surgical Techniques and Strategies . . . . . . . . . .

141

Debora Garozzo 17.1

Main Principles in Repair Strategy for Brachial Plexus Injuries . . . . . . . . . . . . . . .

141

17.1.1 17.1.2

Reinnervation Priorities . . . . . . . . . . . . . . . . Surgical Approach . . . . . . . . . . . . . . . . . . . . .

141 141

17.2

Repair Strategies . . . . . . . . . . . . . . . . . . . .

141

17.2.1

17.3

Repair Strategies Depending on the Injury Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

142

Outcome of Surgical Reinnervation . . .

147

References . . . . . . . . . . . . . . . . . . . . . . . . . .

147

xi

Contents

18

Neonatal Brachial Plexus Palsy: Clinical Presentation and Assessment

..........

149

Thomas J. Wilson and Lynda J-S Yang 18.1

Epidemiology and Risk Factors . . . . . . . .

149

18.4

Electrodiagnostics . . . . . . . . . . . . . . . . . . .

152

18.2

Clinical Assessment . . . . . . . . . . . . . . . . . .

150

18.5

Surgical Assessment . . . . . . . . . . . . . . . . .

152

18.3

Imaging . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

151

References . . . . . . . . . . . . . . . . . . . . . . . . . .

153

The Neonatal Brachial Plexus Lesion: Surgical Strategies . . . . . . . . . . . . . . . . . . . . . . . . . .

155

19

W. Pondaag and M.J.A. Malessy 19.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

155

19.2

Selection for Surgery . . . . . . . . . . . . . . . . .

155 19.5.4

Group 2: C5, C6, C7, (C8) Lesions . . . . . . . . Group 3: C5, C6, C7, C8, T1 Lesions (Pan-plexopathy) . . . . . . . . . . . . . . . . . . . . . Postoperative Care . . . . . . . . . . . . . . . . . . . .

163 163

19.6

Results of Nerve Surgery . . . . . . . . . . . . .

163

19.6.1 19.6.2 19.6.3 19.6.4 19.6.5

Factors That Affect Functional Recovery after Nerve Repair . . . . . . . . . . . . . . . . . . . . . Shoulder Function . . . . . . . . . . . . . . . . . . . . . Hand Function . . . . . . . . . . . . . . . . . . . . . . . . Elbow Flexion . . . . . . . . . . . . . . . . . . . . . . . . Evaluation of Outcome . . . . . . . . . . . . . . . . .

163 164 164 165 165

19.7

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . .

166

References . . . . . . . . . . . . . . . . . . . . . . . . . .

166

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

169

19.3

Surgical Exposure . . . . . . . . . . . . . . . . . . . .

155

19.3.1 19.3.2 19.3.3

Supraclavicular Exposure . . . . . . . . . . . . . . Infraclavicular Exposure . . . . . . . . . . . . . . . Exposure and Technique for Nerve Transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

155 157

19.4

19.5

19.5.1

20

158

Assessment of the Severity of the Lesion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

159

Principles Underlying Strategies for Surgical Reconstruction . . . . . . . . . . . . . .

159

Group 1: C5, C6/Upper Trunk Lesions . . . .

161

Lumbosacral Plexus Injuries

19.5.2 19.5.3

162

Debora Garozzo 20.1

Epidemiology and Causative Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . .

169

20.2

Clinical Pictures . . . . . . . . . . . . . . . . . . . . .

169

20.3

Management . . . . . . . . . . . . . . . . . . . . . . . .

170

20.4

Natural History . . . . . . . . . . . . . . . . . . . . . .

171

21

20.5

Indication for Surgery . . . . . . . . . . . . . . . .

172

20.6

Main Principles in Repair Strategy . . . . .

172

References . . . . . . . . . . . . . . . . . . . . . . . . . .

173

Facial Nerve Palsy: Indications and Techniques of Surgical Repair . . . . . . . . . . . . . . . .

174

Stefano Ferraresi 21.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

174

21.2.5

21.2

Surgical techniques and Results . . . . . . .

174

21.2.6 21.2.7

21.2.1 21.2.2

Extracranial Nerve Repair (10 Cases) . . . . . Intracranial Repair with Proximal Stump Available (3 Cases) . . . . . . . . . . . . . . . . . . . . Nerve Transfers When the Proximal Stump is Unavailable (58 Cases) . . . . . . . . . Hypoglossal-Facial Jump Graft (28 Patients) .

174

21.2.3 21.2.4

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21.2.8

Hypoglossal-Facial Intratemporal Translocation (14 Patients) . . . . . . . . . . . . . Timing of Repair . . . . . . . . . . . . . . . . . . . . . . Facial Nerve Paralysis after Skull Base Fracture (82 Cases) . . . . . . . . . . . . . . . . . . . . Nuclear Peripheral Palsy (4 Cases) . . . . . . .

21.3

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . .

181

References . . . . . . . . . . . . . . . . . . . . . . . . . .

182

177 180 181 181

175 175 176

Contents

22

Benign Peripheral Nerve Tumors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

184

José Fernando Guedes-Corrêa, Francisco José Lourenço Torrão, Jr., and Daniel Barbosa 22.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

184

22.7.2

Symptomatic . . . . . . . . . . . . . . . . . . . . . . . . .

190

22.2

Types and Nomenclature . . . . . . . . . . . . .

184

22.8

Operative Techniques . . . . . . . . . . . . . . . .

190

22.2.1 22.2.2

Benign peripheral nerve sheath tumors . . Benign tumors of nonneural sheath origin . . . . . . . . . . . . . . . . . . . . . . . . .

184

22.8.1 22.8.2

Brachial Plexus. . . . . . . . . . . . . . . . . . . . . . . . Lumbosacral Plexus (or Pelvic Plexus) . . . .

191 191

22.9

Surgical Outcome . . . . . . . . . . . . . . . . . . . .

192

22.3

Clinical Presentation . . . . . . . . . . . . . . . . .

188 22.9.1

22.4

Imaging (Magnetic Resonance Imaging) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

188

Surgical Outcome of Benign Tumors of Neural Sheath Origin . . . . . . . . . . . . . . . . . . Outcomes of Operative Benign Tumors of Nonneural Sheath Origin . . . . . . . . . . . . . . .

22.5

Electrodiagnostic Testing . . . . . . . . . . . . .

189

22.6

Biopsy. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

189

22.7

Approach to Treatment . . . . . . . . . . . . . .

190

22.7.1

Asymptomatic . . . . . . . . . . . . . . . . . . . . . . . .

190

23

Malignant Peripheral Nerve Sheath Tumors

187

22.9.2

22.10

192 194

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . .

194

References . . . . . . . . . . . . . . . . . . . . . . . . . .

194

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

196

Jennifer Hong, Jared Pisapia, Paul J. Niziolek, Viviane Khoury, Paul Zhang, Zarina Ali, Gregory Heuer, and Eric L. Zager 23.1

Introduction . . . . . . . . . . . . . . . . . . . . . . . . .

196

23.7

Workup and Evaluation . . . . . . . . . . . . . .

202

23.2

Epidemiology . . . . . . . . . . . . . . . . . . . . . . . .

196

23.8

Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . .

202

23.2.1 23.2.2

Neurofibromatosis Type 1 . . . . . . . . . . . . . . Previous Radiation . . . . . . . . . . . . . . . . . . . .

196 196

23.9

Surgery . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

202

23.3

Clinical Presentation . . . . . . . . . . . . . . . . .

196

23.9.1 23.9.2 23.9.3

Chemotherapy . . . . . . . . . . . . . . . . . . . . . . . . Radiation Therapy . . . . . . . . . . . . . . . . . . . . . Neoadjuvant Therapy . . . . . . . . . . . . . . . . . .

203 204 204

23.4

Radiology . . . . . . . . . . . . . . . . . . . . . . . . . . .

197

23.10

Prognosis . . . . . . . . . . . . . . . . . . . . . . . . . . .

204

23.4.1 23.4.2

197 199 199 200

23.5

Pathology . . . . . . . . . . . . . . . . . . . . . . . . . . .

200

23.10.1 Overall Survival . . . . . . . . . . . . . . . . . . . . . . . 23.10.2 Disease Free Survival, Local and Distant Recurrence . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.10.3 Low-Grade MPNST . . . . . . . . . . . . . . . . . . . . 23.10.4 Pediatric MPNST . . . . . . . . . . . . . . . . . . . . . . 23.10.5 Postradiation MPNST . . . . . . . . . . . . . . . . . .

204

23.4.3 23.4.4

Magnetic Resonance Imaging . . . . . . . . . . . Positron Emission Tomography/Computed Tomography . . . . . . . . . . . . . . . . . . . . . . . . . . Computed Tomography . . . . . . . . . . . . . . . . Ultrasound . . . . . . . . . . . . . . . . . . . . . . . . . . .

23.5.1 23.5.2 23.5.3 23.5.4

Gross Examination . . . . . . . . . . . . . . . . . . . . Microscopic Examination . . . . . . . . . . . . . . Immunohistochemistry . . . . . . . . . . . . . . . . Pathologic Subtypes of MPNST . . . . . . . . . .

201 201 201 202

23.11

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . .

207

References . . . . . . . . . . . . . . . . . . . . . . . . . .

207

23.6

Pathogenesis and Cancer Genetics . . . .

202

Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

210

204 207 207 207

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Foreword Once in a while, we have the opportunity to make a contribution to a great treatise in the field of neurosurgery, and in this occasion through this foreword. A great neurosurgical treatise must be related to difficult and complex topics and must be written by expert neurosurgeons in the field with full dedication. Peripheral nerve surgery comprises a long list of potentially difficult and complicated cases in the surgery of the nervous system. Anatomy of the peripheral nerves, current diagnostic ancillary techniques (ultrasonography and MRI), the most advanced techniques for nerve reconstruction and repair, compressive syndromes, adult and neonatal brachial plexus lesions, facial nerve reconstruction, and benign and malignant peripheral nerve tumors, are dealt with in this monumental book. The editors and contributors of this book are leading experts in these difficult topics. The activity of the WFNS Peripheral Nerve Surgery Committee has been outstandingly exemplary under the guidance of Prof. Socolovsky, from 2013 to 2017. We must consider this book as the colophon of the tireless activity of the committee with dozens of steps related to teaching courses, publications, countless initiatives such as online courses, etc. These actions of great value deserve further comments. The field of peripheral nerve surgery may be one of the less developed areas in any average neurosurgical department all around the world. This is clearly due to its

xiv

difficulty and complexity, and it is also true that medical industry customarily does not furnish any financial support, as in this case, technology is substituted by anatomical knowledge, fine microsurgical techniques, and passion. So, in the current world (in the context of the importance of the financial aspect), the devotion toward peripheral nerve must be considered an enormous inspiration and an example to be followed because of all the aforementioned reasons. Last but not the least, it is important to mention how this book and its very practical and didactic approach will contribute to the dissemination of knowledge of this field all around the globe, with special mention and interest in developing countries—an aspect that the editors and many of the authors have promoted considerably. My deepest and most sincere congratulations for this magnificent contribution to the world’s neurosurgical knowledge. Miguel A. Arraez, MD, PhD Chairman, Department of Neurosurgery Carlos Haya University Hospital Associate Professor of Neurosurgery Malaga University Malaga, Spain WFNS, Coordinator of Committee Activities Chairman, WFNS Foundation

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Foreword The Manual of Peripheral Nerve Surgery is a new book on all aspects of peripheral nerve systems. In this book, experienced scientists from the field of peripheral nerve have contributed chapters to explain the human peripheral nerve system in all existing aspects, with the description of pathophysiology of nerve degeneration and regeneration as well as classification of Seddon and Sunderland. With the study of the anatomy, the reader will get a very precise orientation of the location and pathways of individual peripheral nerves in upper and lower extremities in which the brachial plexus and lumbosacral plexus are included. The collateral branches of individual nerves have been specially considered, which is very important in diagnostic and in surgical treatment. A special chapter has been dedicated to surgical anatomy and approaches to all peripheral nerve systems. The clinical and neurophysiological examination and evaluation of individual peripheral nerve as well as neuroradiological exposure have been very nicely described. To demonstrate the fact that peripheral nerve can be injured not only by trauma, but also by other circumstances, a special chapter has been dedicated to the gunshot lesion as well as electrical, thermal and radiation injuries. A special chapter is dedicated to electrodiagnostic pre-, intra- and postoperative evaluations which can give neurologists and neurosurgeons good information about the condition of injuries of individual nerves. In the past 10 years, magnetic resonance neurography has increasingly been introduced to the diagnostic of peripheral nerve systems and is giving very useful information sometimes, not only about the peripheral nerve itself but also about all the tissues around the nerves. That is another reason that adds value to such a chapter in

this book. The same is true about the introduction of ultrasound in peripheral nerve surgery which can also be used by compression neuropathy, trauma, and tumor. A very interesting and important chapter is the description of all existing compression syndromes of peripheral nerve in the entire human body. Many clinical examples of surgical repair of nerve lesions give the reader a good understanding of the microsurgical technique of neurolysis and neurorrhaphy with grafts. The problem of diagnostic and treatment of neonatal brachial plexus palsy has been described very well for clinical evaluation and indication, as well as results of surgery. I am very pleased that facial nerve palsy has become a very important chapter in this book, particularly the indication, technique, and surgical repair. Peripheral nerve tumors are also an important part of peripheral nerve surgery as they create not only neurological deficit but also cause severe pain, and therefore this chapter is very helpful for all colleagues who are dealing with peripheral nerve systems. I would like to congratulate the editors of this book, Mariano Socolovsky, Lukas Rasulic, Rajiv Midha und Debora Garozzo, as well as all chapter authors for publishing such an excellent and very useful book to support all active surgeons from different specialities who are interested in the diagnostic and treatment of human peripheral nerve systems.

Prof. Dr. med. Dr. h. c. mult. M. Samii President INI Hannover GmbH Hannover, Germany Honorary President, WFNS

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Foreword It is with immense pleasure that I am writing these lines to introduce this book on peripheral nerve surgery, which represents the ultimate work of wellknown experts in the field. It has been estimated that the rate of posttraumatic peripheral nerve injuries has been continuously rising in recent years due to widespread motorization in developing areas of the world, such as in Southeast Asia, and the ongoing warfare in the Arab world. This has consequently resulted in a major demand for professionals presenting the cultural background, necessary to manage and treat these patients. On the other hand, remarkable progress in imaging and surgical technique has revolutionized this subspecialty and today, peripheral nerve surgery has become a much more complex and articulate art in comparison with the past. Unfortunately, too many neurosurgeons around the world neglect and have abandoned this discipline that, on the contrary, has become a major legacy of surgeons from other specialties (such as plastic and orthopaedic surgery). Yet we reckon that it should be emphasized that peripheral nerve surgery should be undeniably considered an integral and indispensable part of neurosurgery. We should reclaim this specialty as essential to knowledge and competence, especially of young neurosurgeons. We are therefore delighted to support the Peripheral Nerve Surgery Committee in the World Federa-

xvi

tion of Neurosurgical Societies, and we truly appreciate and hold in high esteem the work done by the editors of this book: Drs Socolovsky, Midha, Rasulic, and Garozzo, who have coordinated a group of very distinguished specialists in the field in an effort to offer an updated and comprehensive approach to peripheral nerve surgery, providing a useful tool of knowledge to those who want to deal with the management and treatment of such pathology in their professional practice. The book admirably presents traumatic injuries, entrapment syndromes, and nerve tumors in every aspect, dealing, in an effective and practical approach, with all the situations that neurosurgeons are likely to face during daily practice. As the president of the World Federation of Neurosurgical Societies, I am grateful to all the authors for their invaluable contribution to spread their expertise and knowledge, and I do hope that this book will soon be considered a fundamental source of information by every neurosurgeon in the world. Prof. Franco Servadei, MD Department of Neurosurgery Humanitas University and Research Hospital Milano, Italy President Elect, WFNS Past President, Italian Society of Neurosurgery (SINCh)

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Foreword It is an honor to write the Foreword for this book on peripheral nerve surgery, written and edited by distinguished colleagues and dear friends from around the globe. This book spans a spectrum of peripheral nerve disorders including entrapments, injuries, tumors, and neuropathic pain, and has broad applications (from head to toe in the neonate and the adult) and wide implications based on specific anatomy and pathology, physiology, and treatment. It offers pearls for the beginner and the subspecialist and, as in its very title, an overview of the basics and the complex. Peripheral nerve surgery is an exciting discipline with a rich heritage: it balances the failures and the advances. This book reflects the excitement of our times; it provides glimpses into what is known and remains unknown, and what is fact and controversy. The voyage through history conjures respect for the

past, perspective on the present, and hope for the future. The future of peripheral nerve surgery is bright. Growing interest and experience in the field and technological advances are allowing us to reach newer heights. This book will help raise the bar and will serve a dual purpose: educating generalists and inspiring experts with common purposes—to expand knowledge and to improve patient outcomes. Robert J. Spinner, MD Chairman, Department of Neurologic Surgery Burton M. Onofrio, MD Professor of Neurosurgery Professor of Orthopedics and Anatomy Mayo Clinic Rochester, Minnesota, USA

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Preface This book is the product of the intense, concerted efforts of numerous individuals who have dedicated their professional lives to the fascinating field of peripheral nerve surgery. The editors were fortunate to receive contributions from several renowned experts from around the world. Spread over 23 chapters, the book covers all of the essential topics. It starts with the very basics, such as anatomy, physical examination, and diagnosis. It then progresses through the surgical management of every nerve problem that is currently deemed amenable to surgical treatment, including nerve trauma, nerve compressions, and nerve tumors. To make the information easy to understand and concise, but complete, descriptions of surgical treatments are divided by pathology. The book has been designed to serve as a consultative reference for those surgeons or clinicians who have experience with nerve problems; but it can also be used to gently guide relative novices in the field who want to immerse themselves more deeply in this engaging and eminently rewarding subspecialty. This book has been written for neurosurgeons, plastic surgeons, orthopaedic surgeons, hand surgeons, vascular surgeons, neurologists, and physical and occupational therapists, as well as any other health care provider who is interested in the surgical treatment of peripheral nerve disorders. This field is extremely rewarding because, contrary to brain and spinal surgery, peripheral nerve surgery has the potential to induce the recovery of previously completely lost function. This is due to the innate capacity that axons have to regenerate and grow, so that, over time, they can reach an intended target, whether that be a denervated muscle or an insensate

xviii

area of the skin. However, this theoretical advantage is, at the same time, its Achilles tendon: the velocity of a regenerating axon's growth, at roughly 1 mm per day, requires intensive and constant follow-up by the physician, the patient's compliance with the rehabilitation process, and both parties having the patience to wait for positive results to become evident. Historically, relatively few surgeons have been resolute in their dedication to the surgical treatment of peripheral nerve disorders. However, this trend has changed in recent years, probably due to the work of the many pioneers who have revealed consistently good results that can be obtained with nerve repairs, nerve transfers, and nerve decompression. Moreover, the functional improvement that such patients experience is clinically and functionally so important that it is now becoming more and more recognized by the entire medical community. The World Federation of Neurosurgical Societies is a professional, nonprofit, scientific organization that is composed of member societies from more than 130 different countries across 5 continents. As part of its internal organization, the Peripheral Nerve Surgery Committee has been intensively working to promote this type of surgery and, thereby, encouraging even more surgeons to start practicing in this exciting field. As mentioned initially, this book is a concerted effort in this direction. Mariano Socolovsky, MD Lukas Rasulic, MD, PhD Rajiv Midha, MD, MSc, FRCSC, FAANS, FCAHS Debora Garozzo, MD

Acknowledgments We want to thank Dr. Kevin P. White, MD, PhD (www. scienceright.com), for the help in reviewing many of the chapters; Luis Domitrovic, MD (https://ladvic. myportfolio.com), for the illustrations in Chapters 2 and 4; and Martin Montalbetti (http://martinmontal-

betti-ilustracion.blogspot.com.ar) for illustrating the rest of the book and the cover. Mariano Socolovsky, MD Lukas Rasulic, MD, PhD Rajiv Midha, MD, MSc, FRCSC, FAANS, FCAHS Debora Garozzo, MD

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Contributors Carlos Alberto Rodríguez Aceves, MD Neurosurgeon and Peripheral Nerve Surgeon Neurosurgery Division Neurological Center, The American British Cowdray Medical Center Mexico City, Mexico

Gonzalo Javier Hugo Bonilla, MD Staff Surgeon, Peripheral Nerve and Brachial Plexus Unit Department of Neurosurgery University of Buenos Aires School of Medicine Buenos Aires, Argentina

Bassam M. J. Addas, FRCSC Associate Professor Neurological Surgery Department of Surgery King Abdul-Aziz University Hospital Jeddah, Saudi Arabia

Christine Brand, MD Peripheral Nerve Surgery Unit Department of Neurosurgery University of Ulm Ulm, Germany

Zarina Ali, MD, MS Assistant Professor Department of Neurosurgery Perelman School of Medicine University of Pennsylvania Philadelphia, Pennsylvania, USA Gregor Antoniadis, MD, PhD Director Peripheral Nerve Surgery Unit Department of Neurosurgery University of Ulm Guenzburg, Germany Daniel Alves Neiva Barbosa Research Internist Division of Neurosurgery Hospital Universitário Gaffrée e Guinle (HUGG) Federal University of the State of Rio de Janeiro (UNIRIO) Rio de Janeiro, Brazil Daniela Binaghi, MD Chief of Peripheral Nerve Section Radiology Department Favaloro University Favaloro Foundation Buenos Aires, Argentina

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David Robla Costales, MD Department of Plastic and Reconstructive Surgery Hospital Universitario Central de Asturias Oviedo, Spain Javier Robla Costales, MD Department of Neurosurgery Complejo Asistencial Universitario de León León, Spain Luis Domitrovic, MD Department of Radiology Complejo Asistencial Universitario de León León, Spain Javier Fernández Fernández, MD Department of Neurosurgery Complejo Asistencial Universitario de León León, Spain Stefano Ferraresi, MD Head Department of Neurosurgery Ospedale S.Maria della Misericordia Rovigo, Italy Leandro Pretto Flores, MD, PhD Chairman Department of Neurosurgery Hospital das Forças Armadas Brasília–Distrito Federal, Brazil

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Contributors

Debora Garozzo, MD Head Brachial Plexus and Peripheral Nerve Surgery Unit Neurospinal Hospital Dubai, UAE Vice Chairman, WFNS Peripheral Nerve Surgery Committee José Fernando Guedes-Corrêa, MD, PhD Full Professor of Neurosurgery Head of the Division of Neurosurgery Hospital Universitário Gaffrée e Guinle (HUGG) Federal University of the State of Rio de Janeiro (UNIRIO) Rio de Janeiro, Brazil Christian Heinen, MD Senior Consultant Department of Neurosurgery Evangelisches Krankenhaus Oldenburg Carl-von-Ossietzky-University Oldenburg Oldenburg, Germany Gregory Heuer, MD, PhD Assistant Professor Department of Neurosurgery Perelman School of Medicine The Children's Hospital of Philadelphia Philadelphia, Pennsylvania, USA Jennifer Hong, MD Resident Department of Neurosurgery Dartmouth-Hitchcock Medical Center One Medical Center Drive Lebanon, New Hampshire, USA Viviane Khoury, MD Assistant Professor Department of Radiology Director of Musculoskeletal Ultrasound Perelman School of Medicine University of Pennsylvania Philadelphia, Pennsylvania, USA Ralph W. König, MD, PhD Deputy Medical Director Department of Neurosurgery University of Ulm Guenzburg, Germany

Thomas Kretschmer, MD, PhD, IFAANS Professor of Neurosurgery and Director Department of Neurosurgery Evangelisches Krankenhaus Oldenburg University Oldenburg, Germany Martijn J. A. Malessy, MD, PhD Professor of Nerve Surgery Department of Neurosurgery Leiden University Medical Center Leiden, The Netherlands Fernando Martínez, MD Associate Professor Neurosurgical Department Hospital de Clínicas Montevideo, Uruguay Associate Professor Department of Anatomy Facultad de Medicina CLAEH Maldonado, Uruguay Roberto S. Martins, MD, PhD Co-Director Peripheral Nerve Surgery Unit Division of Functional Neurosurgery Institute of Psychiatry University of São Paulo Medical School São Paulo, Brazil Gilda Di Masi, MD Staff Surgeon, Peripheral Nerve and Brachial Plexus Unit Department of Neurosurgery University of Buenos Aires School of Medicine Buenos Aires, Argentina Rajiv Midha, MD, MSc, FRCSC, FAANS, FCAHS Professor and Head Department of Clinical Neurosciences University of Calgary Calgary, Alberta, Canada Peripheral Nerve Section Associate Editor, Neurosurgery and World Neurosurgery Vice Chairman, WFNS Peripheral Nerve Surgery Committee

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Contributors

Paul J. Niziolek, MD Resident Department of Radiology Perelman School of Medicine University of Pennsylvania Philadelphia, Pennsylvania, USA Miguel Domínguez Páez, MD Neurosurgeon and Peripheral Nerve Surgeon Neurosurgery Division Malaga Regional University Hospital Malaga, Spain Maria Teresa Pedro, MD Peripheral Nerve Surgery Unit Department of Neurosurgery University of Ulm Guenzburg, Germany Jared Pisapia, MD Resident Department of Neurosurgery Perelman School of Medicine University of Pennsylvania Philadelphia, Pennsylvania, USA Javier Ibáñez Plágaro, MD Department of Neurosurgery Complejo Asistencial Universitario de León León, Spain W. Pondaag, MD, PhD Neurosurgeon Department of Neurosurgery Leiden University Medical Center Leiden, The Netherlands Sudheesh Ramachandran M.Ch Clinical Fellow Peripheral Nerve Surgery Department of Clinical Neurosciences Hotchkiss Brain Institute University of Calgary Calgary, Alberta, Canada

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Lukas Rasulic, MD, PhD Professor and Head Department of Peripheral Nerve Surgery, Functional Neurosurgery and Pain Management Surgery Clinic for Neurosurgery, Clinical Center of Serbia School of Medicine University of Belgrade Belgrade, Serbia Vice Chairman, WFNS Peripheral Nerve Surgery Committee Ricardo Reisin, MD Chairman of Neurology Hospital Británico Buenos Aires, Argentina Shimon Rochkind, MD, PhD Professor and Director Division of Peripheral Nerve Reconstruction Department of Neurosurgery Head, Research Center for Nerve Reconstruction Tel Aviv Sourasky Medical Center Tel Aviv University Tel Aviv, Israel Federico Salle, MD Neurosurgeon and Assistant Professor Neurosurgical Department Hospital de Clínicas Montevideo, Uruguay Prof. Dr. Miroslav Samardzic Neurosurgeon and Professor Department for Peripheral Nerve Surgery, Functional Neurosurgery and Pain Management Surgery Clinic for Neurosurgery, Clinical Center of Serbia School of Medicine University of Belgrade Belgrade, Serbia Member, WFNS Peripheral Nerve Surgery Committee Victoria E. Fernández Sánchez, MD Clinical Neurophysiologist Clinical Neurophysiology Department Malaga Regional University Hospital Malaga, Spain

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Contributors

Yuval Shapira, MD Vice-Chairman of Neurosurgery Division of Peripheral Nerve Reconstruction Department of Neurosurgery Tel Aviv Sourasky Medical Center Tel Aviv University Tel Aviv, Israel Mario G. Siqueira, MD, PhD Director Peripheral Nerve Surgery Unit Division of Functional Neurosurgery Institute of Psychiatry University of São Paulo Medical School São Paulo, Brazil Mariano Socolovsky, MD Chief Peripheral Nerve and Brachial Plexus Unit Department of Neurosurgery University of Buenos Aires School of Medicine Buenos Aires, Argentina Chairman, WFNS Peripheral Nerve Surgery Committee

Thomas J. Wilson, MD Clinical Assistant Professor Department of Neurosurgery Stanford University Stanford, California, USA Lynda J-S Yang, MD, PhD Professor Department of Neurosurgery University of Michigan Ann Arbor, Michigan, USA Eric L. Zager, MD, FACS, FAANS Professor Department of Neurosurgery Perelman School of Medicine University of Pennsylvania Philadelphia, Pennsylvania, USA Paul Zhang, MD Professor Department of Pathology and Laboratory Medicine Perelman School of Medicine University of Pennsylvania Philadelphia, Pennsylvania, USA

Francisco José Lourenço Torrão, Jr., MD Neurosurgeon Division of Neurosurgery Gaffree e Guinle University Hospital Federal University of Rio de Janeiro State

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Nerve Anatomy of the Upper Limbs

1 Nerve Anatomy of the Upper Limbs Gilda Di Masi and Gonzalo Javier Hugo Bonilla Abstract A strong understanding of the anatomy of the brachial plexus and its terminal branches (radial, axillar, median, ulnar and musculocutaneous nerves) is critical for a correct approach to the nerve injuries of the upper limb. In this chapter, we describe the anatomy and relationships of these structures, focusing on those items that are important when performing surgery on them. Keywords: upper limb, brachial plexus, median nerve, ulnar nerve, radial nerve, axillary nerve, musculocutaneous nerve

1.1 Supraclavicular Brachial Plexus The brachial plexus is a complex structure located in the lower half of the lateral neck, extending from the cervical spine to the axilla (▶ Fig. 1.1). It provides motor, sensory, and autonomic innervation to the upper limb, except for the skin of the upper half of the medial and posterior part of the arm, which is supplied by the intercostobrachial nerve. The brachial plexus can be divided into: (1) a supraclavicular portion, constituted by roots C5 to T1, the upper, middle, and inferior trunks, and its divisions; and (2) an infraclavicular portion, formed by the cords and its

terminal branches. Commonly when we refer to the brachial plexus, we say that it is formed by the union of the C5–C8, and T1 roots.1 However, this is not entirely accurate. In actuality, the brachial plexus is an anastomosis of the ventral rami of spinal nerves C5–C8 and T1, its posterior rami being directed to the spinal muscles (▶ Fig. 1.2). There are two anatomic variants: the prefixed brachial plexus receiving fibers from C4, with little to no contribution from T1; and the postfixed plexus receiving fibers from T2, with little to no contribution from C5.2 Each spinal nerve consists of a ventral root, which has motor and autonomic functions, and a dorsal root, which is sensory. The dorsal root enters the spinal ganglion. Distal to the spinal ganglion, both roots coalesce to emerge through the intervertebral foramen as the spinal nerve. Almost immediately, this nerve divides into two rami: ventral and dorsal. The dorsal rami supply the paraspinal muscles and the skin of the back, while the ventral rami form the brachial plexus.3 The ventral and dorsal roots and the intra-axial portion of the spinal nerve are only covered by an arachnoid sheath. As it exits the intervertebral foramen, this sheath continues as the epineurium. At this level, there are adhesions between the nerve sheath and the transverse process. These adhesions anchor the nerve structures, protecting the roots from traction injury. They are more important at the C5–C7 levels, and weaker at the C8 and T1 levels; for this reason, the C8 and T1 roots are more susceptible to root avulsion.3,4,5

Fig. 1.1 Schematic drawing of the brachial plexus and its terminal branches. The roots, trunks, divisions, cords, and terminal branches can be seen. A, C4 root; B, C5 root; C, C6 root; D, C7 root; E, C8 root; F, T1 root; G, superior trunk; H, middle trunk; I, inferior trunk; J, anterior division of the upper trunk; K, posterior division of the upper trunk; L, anterior division of the middle trunk; M, posterior division of the middle trunk; N, posterior division of the lower trunk; O, anterior division of the lower trunk; P, lateral cord; Q, posterior cord; R, medial cord; S, musculocutaneous nerve; T, axillary nerve; U, radial nerve; V, median nerve; W, ulnar nerve.

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Nerve Anatomy of the Upper Limbs

Fig. 1.2 Each spinal nerve consists of a ventral root and a dorsal root that arise from the spinal cord. The dorsal root enters the spinal ganglion. Distal to the spinal ganglion, both roots coalesce to emerge through the intervertebral foramen as the spinal nerve. Almost immediately, this nerve divides into two primary rami: ventral and dorsal. The primary dorsal rami supply the paraspinal muscles and the skin of the back, while the primary ventral rami form the brachial plexus.

clavicle, the three trunks are located between the anterior and middle scalene muscles (▶ Fig. 1.3). The three trunks emerge from the interscalene space and traverse the inferior region of the posterior triangle of the neck.6

1.1.1 Collateral Branches of the Supraclavicular Brachial Plexus

Fig. 1.3 Supraclavicular brachial plexus. ADUT, anterior division of the upper trunk; C, clavicle; LT, lower trunk; MT, medial trunk; PDUT, posterior division of the upper trunk; SPN, suprascapular nerve; UT, upper trunk.

Before continuing with a description of how the brachial plexus is formed, it is important to mention the relationship it has with the sympathetic nervous system. Immediately distal to its origin, the ventral rami of the spinal nerves that form the brachial plexus receive gray rami communications from the middle and inferior cervical sympathetic ganglia and the first thoracic sympathetic ganglion. Sympathetic fibers destined for the face, via the trigeminal nerve, pass through spinal nerves T1 and T2. It is for this reason that proximal lesions of T1 and/or T2 can cause Horner’s syndrome, which consists of anhidrosis, miosis, ptosis, and enophthalmos.3,4 The most proximal structures in the brachial plexus are the trunks. The upper trunk is formed by the anastomosis of C5 and C6, C7 continues as the middle trunk, and C8 and T1 form the lower trunk. Between the spine and the

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The most proximal collateral branches of the brachial plexus arise from spinal nerves C5–C7 (the phrenic, long thoracic, and dorsal scapular nerves) and upper trunk (suprascapular nerve). They are intended to innervate the muscles of the proximal upper limb. The function of this is to stabilize and mobilize the shoulder, with the exception of the phrenic nerve, which actually is not considered a collateral branch of the plexus, but has a contribution from C5. More detailed descriptions of the nerves and their consistency follow: ● Phrenic nerve: The phrenic nerve receives contributions from C3–C5. It is purely motor and supplies the ipsilateral hemidiaphragm. It runs along the surface of the anterior scalene, its direction being from medial to lateral (making it the only nerve having this direction in the posterior triangle). A proximal lesion of C5 (root avulsion) can cause ipsilateral diaphragmatic paralysis.7 ● Long thoracic nerve: This nerve receives contributions from C5–C7. It passes between the anterior and middle scalene, behind the brachial plexus. It innervates the serratus anterior muscle, the function of which is to stabilize the scapula and allow for scapular rotation and anterior displacement. Injury to this nerve results in a winged scapula. ● Dorsal scapular nerve: The dorsal scapular nerve is a branch of C5, directed dorsally to pierce the middle

Nerve Anatomy of the Upper Limbs

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scalene muscle, after which it continues to run below the levator scapulae to ultimately reach and innervate the rhomboid muscles and the levator scapulae. Its function is to approximate the scapula to the midline. Interscapular injuries cause atrophy, which may manifest as a slightly winged scapula at rest. When this nerve is affected in the context of a brachial plexus injury, it indicates a proximal lesion affecting C5. Suprascapular nerve: This nerve is the only branch that arises from the trunks of the brachial plexus, with contributions from C5 and C6. It originates in the superior portion of the upper trunk, immediately proximal to the clavicle (▶ Fig. 1.3). It then redirects back toward the suprascapular notch. In the notch, it joins the suprascapular artery and vein, both of which are located above the upper scapular ligament, while the nerve lies below. It innervates the supraspinatus and infraspinatus muscles—the former stabilizes the humeral head and contributes to the first 30 degrees of shoulder abduction, while the latter is an external rotator.8

1.2 Infraclavicular Brachial Plexus Within the posterior triangle of the neck, each trunk is divided into an anterior and a posterior division.9 Each division passes under the midclavicle, thereby entering the axilla. The combination of these divisions will form the cords (i.e., the infraclavicular brachial plexus). The cords are named according to their relationship with the axillary artery, so that we have the lateral, medial, and posterior cords. The anterior divisions of the upper and middle trunks form the lateral cord, carrying fibers from C5–C7. The anterior division of the lower trunk continues as the medial cord, carrying fibers from C8 and T1. The posterior divisions of the three trunks are joined to form the posterior cord, carrying fibers from C5–C8 and T1. In the projection of the lateral border of the pectoralis minor muscle, the three cords divide to give rise to the five terminal branches of the brachial plexus. The lateral cord gives rise to the lateral contribution to the median nerve (mainly sensitive) and the musculocutaneous nerve. The medial cord gives rise to the medial contribution of the median nerve (mainly motor) and the ulnar nerve (▶ Fig. 1.4). The axillary and radial nerves arise from the posterior cord. One way to potentially simplify learning the anatomy of the brachial plexus is to relate each structure to a certain function. Consequently, the posterior divisions form the posterior cord, which in turn gives birth to the radial and axillary nerves, both of which are responsible for upper limb extension. Conversely, the anterior divisions form the lateral and medial cords that are responsible for upper limb flexion through their terminal branches: the musculocutaneous, median, and ulnar nerves.

Fig. 1.4 Infraclavicular brachial plexus. AA, axillary artery; BCN, antebrachial cutaneous nerve (medial cutaneous nerve of the forearm); LT, lateral trunk; MC, musculocutaneous nerve; MLB, median lateral branch; MMB, median medial branch; MT, medial trunk; MN, median nerve; UN, ulnar nerve.

1.2.1 Collateral Branches of the Infraclavicular Brachial Plexus In addition to the above-mentioned terminal branches, the infraclavicular brachial plexus also gives out collateral branches.10 They are the following: ● Medial cutaneous nerve of the arm: This branch arises from the medial cord, and has its axonal origin in C8 and T1. After its origin, it descends on the medial side of the axillary artery in an anterior direction. In the arm, it initially is located medial and then anterior to the ulnar nerve, descending in front of the basilic vein. It pierces the aponeurosis next to the basilic vein, and is distributed to the skin of the lower third of the medial surface of the arm. ● Medial cutaneous nerve of the forearm: This nerve is also a branch of the medial cord that supplies the skin of the anterior and posterior surfaces of the medial aspect of the forearm. Within the axilla, it anastomoses with the intercostobrachial nerve, which provides

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Nerve Anatomy of the Upper Limbs

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sensory innervation to the distal axillary region and proximal inner arm. Medial pectoral nerve: This is a collateral branch of the medial cord. It passes through the pectoralis minor and pectoralis major, supplying both muscle groups. Upper and lower subscapular nerve: These are branches of the posterior cord. The former innervates the subscapularis muscle, while the latter supplies the teres major and the distal portion of the subscapularis. Thoracodorsal nerve: Also a branch of the posterior cord, this nerve innervates the latissimus dorsi muscle.11 Lateral pectoral nerve: A collateral branch of the lateral cord, the lateral pectoral nerve pierces the clavipectoral fascia and innervates the pectoralis major muscle.

1.3 Terminal Branches of the Brachial Plexus 1.3.1 Radial Nerve The radial nerve has its axonal origin in the roots C5–C8, and its macroscopic origin in the posterior cord, posterior

Fig. 1.5 Radial nerve. AA, axillar artery; MC, musculocutaneous nerve; MLB, median lateral branch; RN, radial nerve.

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to the third portion of the axillary artery and anterior to the subscapularis, teres major, and latissimus dorsi muscles. In the arm, it is directed obliquely downward, laterally and posteriorly, and passes through the humeral-tricipital slit located below the teres major and the latissimus dorsi.4 This is a musculoskeletal conduit between the radial sulcus of the humerus dorsally and the long and lateral heads of the triceps ventrally, accompanied by the deep humeral artery. Near its origin, the nerve emits a variable number of branches to the triceps directed to innervate its long, medial, and lateral portions separately, as well as a sensory branch, the posterior cutaneous nerve of the arm, which, as its name suggests, provides sensation to the proximal posterior region of the arm. It then continues its course as a satellite of the deep artery of the arm, located between the long and medial heads of the triceps (▶ Fig. 1.5). From there, it comes into contact with the humerus within the radial sulcus or spiral groove, where it gives off additional muscular branches for the lateral and medial heads of the triceps, as well as for the anconeus muscle. It is important to note the anatomy of the collateral sensory branches: the inferior lateral cutaneous nerve of the arm and the posterior cutaneous nerve of the forearm. They provide sensory innervation to the posterior and medial region of the distal arm, elbow, and proximal forearm. At the level of the elbow, the radial nerve can be found between the biceps medially and the brachioradialis laterally, along with the radial recurrent artery; and 2 to 3 cm from this point, it provides a motor branch for the brachioradialis. Once it is beyond the elbow crease, it divides into its two terminals branches, anterior or superficial (sensory) and posterior or deep (motor) (▶ Fig. 1.6). The deep branch or posterior interosseous nerve proceeds posteriorly through the two layers (superficial and deep) of the supinator muscle.12 These layers form the arcade of Frohse, through which the nerve passes to

Fig. 1.6 Terminal branches of radial nerve. AB, anterior branch; BRM, brachioradialis muscle; PB, posterior branch; RN, radial nerve; SM, supinator muscle.

Nerve Anatomy of the Upper Limbs reach the posterior aspect of the forearm. It supplies the muscles in the posterior compartment.13 The superficial or anterior branch continues parallel but dorsal to the brachioradialis muscle (▶ Fig. 1.7), accompanied by the radial artery so that, once through the posterior fascia of the hand, it gives sensation to the posterior surface of the hand.

1.3.2 Median Nerve The median nerve originates in the roots C5–C8 and T1. Macroscopically, it stems from the union of the internal fibers of the medial cord and the external fibers of the lateral cord, forming an “M” above the axillary artery.14 It should be noted that there is considerable anatomical variety in how the cords divide and in the conformation of the median nerve (▶ Fig. 1.8). From its origin, the nerve always runs adjacent to the brachial artery (▶ Fig. 1.9). There are no collateral branches in the arm. Distally in the arm, it is located in the cubital fossa, along with the humeral artery and articular branches, where muscular branches arise from the medial side and travel to the pro-

Fig. 1.7 Radial nerve (superficial branch). BRM, brachioradialis muscle; RA, radial artery; RN, radial nerve; FDS, flexor digitorum superficialis muscle.

Fig. 1.9 Median nerve conformation. AA, axillary artery; LT, lateral trunk; MC, musculocutaneous nerve; MLB, median lateral branch; MMB, median medial branch; MT, medial trunk.

nator teres muscle, flexor digitorum superficialis, flexor carpi radialis, and palmaris longus. Once past the elbow crease, it is located between the humeral (surface) and ulnar (deep) heads of the pronator teres muscle, crossing the ulnar artery from medial to lateral. Almost immediately after passing through the heads of the pronator teres, it gives off one of its longer branches, the anterior interosseous nerve, located posterior (deep) to the main trunk of the median nerve (▶ Fig. 1.10), along with the anterior interosseous artery, above the pronator quadratus muscle and the interosseous membrane. Approximately 4 cm distal to the origin of the anterior interosseous nerve, the median nerve gives off its first branch to the flexor pollicis longus, followed by branches to the first and second flexor digitorum profundus. There are some anastomosis between the median and ulnar nerves, that is, the so-called Martin-Gruber anastomosis, existing in roughly 10 to 25% of the population. Another anastomosis between both nerves are the socalled Riche-Cannieu anastomosis, between the thenar branch of the median nerve and the deep branch of the ulnar nerve in the palm.

Fig. 1.8 Median nerve conformation (“M”). AA, axillary artery; LT, lateral trunk; MC, musculocutaneous nerve; MLB, median lateral branch; MMB, median medial branch; MN, median nerve; MT, medial trunk.

Fig. 1.10 Anterior interosseous nerve. AIA, anterior interosseous artery; AIN, anterior interosseous nerve; PQ, pronator quadratus.

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Nerve Anatomy of the Upper Limbs

Fig. 1.11 Thenar branches of median nerve. MN, median nerve; PB, palmaris brevis muscle; RMB, recurrent motor branch.

Fig. 1.12 Median and ulnar nerve in the wrist. MN, median nerve; RA, radial artery; UA, ulnar artery; UN, ulnar nerve.

The median nerve continues its course through the antebrachial region to about 5 cm proximal to the wrist, where it is located superficial and lateral to the flexor digitorum superficialis muscle. One of the sensory branches in this region is the palmar cutaneous branch, which gives sensation to the proximal palm. Already in the distal forearm region, the nerve is located between the tendons of the palmaris longus muscle medially and the flexor carpi radialis laterally, before entering the carpal tunnel. The carpal tunnel is an osteofibrous structure through which several structures pass, including the median nerve, the tendons of the flexor digitorum superficialis and profundus, and flexor pollicis longus and, in 10% of the population, an arterial branch called the median persistent artery.15 Distal to the carpal tunnel, the nerve divides into its terminal branches: the recurrent branch (▶ Fig. 1.11 and ▶ Fig. 1.12) (to the opponens pollicis, abductor pollicis brevis, and superficial part of flexor pollicis brevis); branches for the first and second lumbricals; and digital cutaneous branches to the first, second, and third fingers, as well as the inner (lateral) surface of the fourth finger.

1.3.3 Ulnar Nerve The ulnar nerve has its axonal origin in roots C8 to T1, and its macroscopic origin in the medial cord (▶ Fig. 1.13), along with the internal brachial cutaneous and brachial cutaneous accessory nerve, located medially to the humeral artery.4 About 8 cm proximal to the epicondyle, the ulnar nerve pierces the medial intermuscular septum to end up located in the posterior compartment of the arm. This region, formed by the arch of the brachial fascia and muscle fibers of the medial head of the triceps, is called

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Fig. 1.13 Ulnar nerve. AA, axillary artery; CBM, coracobrachialis muscle; MC, musculocutaneous nerve; MN, median nerve; RN, radial nerve; UN, ulnar nerve.

Nerve Anatomy of the Upper Limbs

Fig. 1.15 Ulnar nerve in the proximal forearm. FCU, flexor carpi ulnaris muscle; UN, ulnar nerve.

Fig. 1.14 Arcade of Struthers. SA, arcade of Struthers; UN, ulnar nerve between the medial epicondyle and the olecranon.

Fig. 1.16 Ulnar nerve in the distal forearm. FCU, flexor carpi ulnaris muscle; FDS, flexor digitorum superficialis muscle; PB, palmaris brevis muscle; UN, ulnar nerve.

the arcade of Struthers (▶ Fig. 1.14); it is a potential nerve compression site. Once at the elbow, the nerve passes between the medial epicondyle and the olecranon, covered by the ulnar ligament. Continuing its route, it enters under a tendinous arch formed by the humeral and ulnar heads of the flexor carpi ulnaris muscle, called the cubital tunnel. The ulnar nerve emerges 4 to 6 cm from the medial epicondyle through the flexor pronator muscle fascia, where it gives off two motor branches to the flexor carpi ulnaris muscle, and more distally to the fourth and fifth flexor digitorum profundus. Then it continues distally in the medial forearm above the flexor digitorum profundus and under the flexor carpi ulnaris (▶ Fig. 1.15). Distally, it is located lateral to the flexor carpi ulnaris, always in relation to the ulnar artery, the artery satellite of the ulnar nerve (▶ Fig. 1.16). It gives off a sensory branch, the palmar branch of the ulnar nerve, and then enters Guyon’s canal.16 This canal is formed by the palmar carpal ligament anteriorly, the pisiform medially, and extensions of the flexor carpi ulnaris and the deeper flexor retinaculum posteriorly.17 Immediately distal to this tunnel, or in some cases within the tunnel, the ulnar nerve divides into its two terminal branches: the superficial branch and the deep branch (▶ Fig. 1.17).

Fig. 1.17 Guyon’s canal. DB, deep branch; GC, Guyon’s canal; SB, superficial branch; UN, ulnar nerve.

The superficial branch descends in front of the hypothenar eminence to end as digital branches for the fourth and fifth fingers and the ulnar aspect of third finger, while the deep branch passes below the hypothenar muscles and gives off muscular branches to them. Finally, it innervates the palmar interossei, the third and fourth lumbrical muscles, and the adductor pollicis (▶ Fig. 1.12).

1.3.4 Musculocutaneous Nerve The musculocutaneous nerve has its axonal origin in roots C5 and C6, with a small contribution from C7.4 Its macroscopic origin is in the lateral cord, together with the lateral root of the median nerve near the inferior edge of the pectoralis minor muscle. It runs laterally to the axillary artery, emitting branches to the coracobrachialis muscle. It pierces the coracobrachialis muscle and passes obliquely between the biceps and the brachialis, giving off a variable number of motor branches to these two muscles (▶ Fig. 1.18, ▶ Fig. 1.19). Then the musculocutaneous nerve continues its course as the lateral cutaneous nerve, running in an oblique and superficial direction and having an exclusively sensory

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Nerve Anatomy of the Upper Limbs

Fig. 1.19 Musculocutaneous nerve. BB, biceps brachialis muscle; MB, motor branches; MC, musculocutaneous nerve; MN, median nerve.

Fig. 1.18 Musculocutaneous nerve. AA, axillary artery; CBM, coracobrachialis muscle; MC, musculocutaneous nerve; MLB, median lateral branch.

function. It ends in the skin of the elbow crease and lateral surface of the forearm.18

Fig. 1.20 Axillary nerve. AA, axillary artery; AN, axillary nerve; MLB, median lateral branch; MMB, median medial branch; RN, radial nerve; TMA, teres major muscle; TMI, teres minor muscle.

1.3.5 Axillary Nerve The axillary nerve has its axonal origin in roots C5 and C6, and its macroscopic origin in the posterior cord of the brachial plexus along the radial nerve.4 It is located lateral to the radial nerve and posterior to the axillary artery. It passes over the subscapularis until it reaches its inferior edge, where it encounters the posterior humeral circumflex artery, a collateral branch of the axillary artery. There it is located in the quadrangular space,19 where it is bounded by the subscapularis (anterior), the teres minor muscle (posterior), the surgical neck of the humerus and long head of the triceps (lateral), and the teres major muscle (inferior) (▶ Fig. 1.20). Approximately 3 cm distal to this space, it divides into two branches. The anterior branch is accompanied by the posterior circumflex vessels surrounding the surgical

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neck of the humerus, giving off branches to the anterior and medial portions of the deltoid muscle. Likewise, it gives sensory cutaneous branches to the shoulder girdle. The posterior branch supplies the teres minor and posterior deltoid muscles.20

References [1] Sunderland S, ed. Nervios Perifericos y sus Lesiones. Barcelona: Salvat; 1985 [2] Thompson GE, Rorie DK. Functional anatomy of the brachial plexus sheaths. Anesthesiology. 1983; 59(2):117–122 [3] Russel SM, ed. Examination of Peripheral Nerve Injury: An Anatomical Approach. 2nd ed. New York, NY: Thieme; 2008 [4] Siqueira MG, Martins RS, eds. Anatomia Cirúrgica das Vias de Acceso aos Nervos Periféricos. 1st ed. Rio de Janeiro: DiLivros; 2006

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Nerve Anatomy of the Upper Limbs [5] Museti Lara A, Dolz C, Rodriguez Baeza A. Anatomy of the brachial plexus. In: Gilbert A, ed. Brachial plexus injuries. London: Martin Dunitz; 2001 [6] Pro A, ed. Anatomía Humana de Latarjet-Ruiz Liard. Buenos Aires: Editorial Médica Panamericana; 2004 [7] Alnot JY, Narakas A, eds. Les Paralysies du Plexus Brachial. Monographies du Groupe d'étude de la main. Paris: Expansion scientifique francaise; 1989 [8] Franco CD, Rahman A, Voronov G, Kerns JM, Beck RJ, Buckenmaier CC, III. Gross anatomy of the brachial plexus sheath in human cadavers. Reg Anesth Pain Med. 2008; 33(1):64–69 [9] Bollini CA. Revision anatómica del plexo braquial. Revista Argentina de Anestesiología. 2004; 62:386–398 [10] Moore K, Dalley AF, eds. Anatomía con Orientación Clínica. 5th ed. Madrid: Editorial Médica Panamericana; 2007 [11] Netter FH, ed. Atlas de Anatomía Humana. 2nd ed. Barcelona: Masson; 1999 [12] Testut L, Jacob O, eds. Anatomía Humana Tomo 1. 8th ed. Barcelona: Salvat; 1981

[13] Testut L, Jacob O, eds. Tratado de Anatomia Topográfica con Aplicaciones Medicoquirúrgicas Tomo 2. Barcelona: Salvat; 1982 [14] Blunt MJ. The vascular anatomy of the median nerve in the forearm and hand. J Anat. 1959; 93(1):15–22 [15] Williams P, Warwick R, eds. Anatomía de Gray, Tomo 11. 36th ed. Barcelona, Salvat; 1985 [16] Netter FH, ed. Sistema Nervioso. Anatomía y Fisiología. Tomo 1. 1. Colección Ciba de ilustraciones médicas. Barcelona: Salvat; 1990 [17] Reyes JT, Nuñez CT. Nomenclatura Anatómica Internacional. Mexico: Editorial Médica Panamericana; 1998 [18] Rouvière H, Delmas A, eds. Anatomía Humana. Descriptiva, Topográfica y Funcional. 10th ed. Barcelona: Masson; 1999 [19] Bouchet A, Cuilleret J, eds. Anatomía descriptiva, topográfica y funcional. Buenos Aires: Editorial Médica Panamericana; 1987 [20] Kahle W, ed. Atlas de Anatomía, tomo 3: Sistema Nervioso y Organos de los Sentidos. Barcelona: Omega; 1995

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Surgical Anatomy and Approaches to the Nerves of the Lower Limb

2 Surgical Anatomy and Approaches to the Nerves of the Lower Limb Fernando Martínez and Federico Salle Abstract The innervation of the lower limb is given by the lumbar plexus (L1–L4) and sacral plexus (L5–S3). The lumbar plexus innervates through its branches: the abdominal wall, the inguinocrural region, and the anterior, lateral, and inner thigh regions. From the motor point of view, it is responsible for the flexion of the thigh over the pelvis and the extension of the knee. The sacral plexus innervates from the motor point of view: the posterior region of the thigh, posterior and anterior region of the leg, and dorsal and ventral aspects of the foot. This chapter details the collateral and terminal branches of the lumbar and sacral plexuses, their motor and sensory distribution, as well as the surgical approaches to these nerve structures. Keywords: lumbar plexus, sacral plexus, lateral femoral cutaneous nerve, femoral nerve, sciatic nerve

2.1 Introduction Innervation of the lower limbs follows a basic pattern: two nerve plexuses (lumbar and sacral) give rise to a number of nerves that enter the extremity through three anatomical regions—the inguinal, gluteal, and obturator— to distribute themselves throughout the muscular, cutaneous, bony, and vascular structures of the limb.1,2,3,4,5,6,7,8 In this chapter, we review the anatomy of the nerves of the lower limb, especially focusing on: (1) how this anatomy can cause clinical disorders, and (2) how it influences surgical approaches to treatment.

2.2 Lumbar Plexus The lumbar plexus is formed by the union of the anterior branches of spinal roots L1–L4, with additional nerve fiber contributions from T12 (▶ Fig. 2.1). The anterior branches of the aforementioned roots emerge from their corresponding neural foramina and, thereafter, remain inside the psoas major muscle which has two fascicles of insertion. The anterior insertions correspond to the lumbar vertebral bodies, while the posterior ones can be found at the level of the transverse processes of the same vertebrae. This is how a V-shaped interstice is created between the two fascicles.3 Within the substance of the muscle, L1–L4 exchange fibers and form the lumbar plexus as follows: L1 mostly supplies the ilioinguinal, iliohypogastric, and genitofemoral

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Fig. 2.1 Schematic drawing of the lumbar and sacral plexus. A, ilioinguinal nerve; B, iliohypogastric nerve; C, femorocutaneous nerve; D, femoral nerve; E, genitofemoral nerve; F, obturator nerve; G, sciatic nerve; H, pudendal nerve.

nerves; L2 and L3 contribute to the lateral femoral cutaneous nerve of the thigh; and L2–L4 give rise to the obturator and femoral nerves. Conceptually, Russell has divided the terminal branches of the lumbar plexus into two groups of three nerves each: (1) the inguinal group, composed of the ilioinguinal, iliohypogastric, and genitofemoral nerves; and (2) the femoral group, composed of the lateral femoral cutaneous, femoral, and obturator nerves. From an anatomical point of view, the first four nerves are considered collateral branches of the lumbar plexus, while the last two are considered terminal branches.

Surgical Anatomy and Approaches to the Nerves of the Lower Limb

2.2.1 Inguinal Group The three nerves within the inguinal group originate within the psoas major muscle and run across the anterior abdominal wall to reach the inguinal region. These nerves can suffer direct trauma, can be damaged by traction or kinking, and can even be injured by sutures placed during operative procedures involving the lower anterior abdominal wall (such as, appendectomies, C-sections, etc.) or lateral wall (lumbotomy), giving rise to sensory disturbances or pain syndromes across their territory of distribution (i.e., the inguinal area and genitalia).9,10,11,12

Iliohypogastric Nerve The iliohypogastric nerve has its origins in L1, although it also receives a T12 anastomosis. After emerging from under the psoas muscle, it runs outward across the quadratus lumborum muscle to finally rest between the transversus abdominis and internal oblique muscles. In the region of the anterior superior iliac spine, it divides into two branches. The outer branch becomes superficial and innervates the lateral gluteal region. The internal branch continues its descending path, passing through the inguinal canal to innervate the inguinal region. The sensory distributions of all the nerves of the inferior limb are shown in ▶ Fig. 2.2.

Ilioinguinal Nerve The ilioinguinal nerve stems from a branch of the L1 root and has a trajectory which is similar to that of the iliohypogastric nerve, albeit somewhat more caudal. It runs at the level of the oblique muscles of the abdomen and innervates structures, such as, the spermatic cord and cremaster muscle. Along with the iliohypogastric nerve, it provides sensory innervation to the inguinal and genital regions.

Genitofemoral Nerve The genitofemoral nerve receives nerve fibers from both L1 and L2. It has a deeper trajectory than the aforementioned two nerves within the lumbar region. Before reaching the inguinal ligament, it divides into two branches: genital and femoral.9 The femoral branch runs beneath the inguinal ligament, lateral to the common femoral artery, and innervates the region of the femoral triangle. The genital branch enters the inguinal canal and terminates in the skin of the external genitalia and cremaster muscle (in males).

Surgical Approach These three nerves are not generally approached per se, except when they are affected by postoperative fibrosis or iatrogenic lesions secondary to different kinds of surgery in the region. Ideally, a thorough clinical examination will

Fig. 2.2 Sensory distribution of the nerves of the inferior limb. At left, an anterior view of the lower limb; at right, a posterior view. 1-A, ilioinguinal nerve; 2.1, iliohypogastric nerve; 2.2, genitofemoral nerve; 3-F, lateral femoral cutaneous nerve; 4.1, femoral nerve (musculocutaneous branches); 4.2-J, femoral nerve (internal saphenous nerve); 5-H, obturator nerve; 6, peroneal nerve; 7, musculocutaneous nerve; 8, anterior tibial nerve; 9-K, external saphenous nerve; 10, calcaneal nerve; E, gluteal and sacral nerves; G, lesser sciatic nerve; I, cutaneous peroneal nerve; L1-L2, internal and external plantar nerves.

reveal the source of pain, guiding the location and extent of the surgical incision.

2.2.2 Femoral Group The femoral group of nerves is composed of two mixed (both motor and sensory) nerves and one that is purely sensory.

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Surgical Anatomy and Approaches to the Nerves of the Lower Limb

Lateral Femoral Cutaneous Nerve

Surgical Approach

The lateral femoral cutaneous nerve (LFCN) is an exclusively sensory nerve that has its origins in branches from L2 and L3. From its origin, it runs lateral and downward, relative to the iliac muscle. When it reaches the inguinal ligament, anatomical variations may be evident.5,13,14 It usually passes below the outermost sector of the ligament, and traverses the superficial fascia 2.5 cm below and medial to the anterior superior iliac spine.14 After entering the anterior region of the thigh, it then divides into two branches that innervate the anterolateral thigh, from the gluteal region to the knee.2 Among the anatomical variations that have particular clinical relevance, we note the following: passage of the nerve between the fibers of the inguinal ligament; entrance into the thigh lateral to the anterior superior iliac spine; absence of the main nerve trunk in the thigh with two or more branches already divided; and a nerve that pierces the sartorius muscle to become superficial.14,15 In its passage from the inguinal region to the thigh, the LFCN can be trapped by aponeurotic fibers or can suffer direct trauma. Iatrogenic trauma can arise from specific surgical positions (ventral decubitus) and interventions, such as, obtaining bony grafts from the anterior superior iliac spine.16 Compressive neuropathy affecting the LFCN typically is associated with pain in the anterolateral part of the thigh.

Consistent with the anatomical features just reviewed, the LFCN is approached by creating an incision parallel to the inguinal ligament, 2 cm below and 2 cm medial to the anterior superior iliac spine (▶ Fig. 2.3, ▶ Fig. 2.4, ▶ Fig. 2.5).

Since these nerves are largely sensory, their examination requires an assessment of sensory function throughout their territory of cutaneous distribution.

The obturator nerve has its origin in L2–L4. From its origin, it runs medially along the internal border of the psoas muscle into the retroperitoneum, to finally enter the lower pelvis.17,18 In the pelvis, it follows the lateral wall until the subpubic canal, through which the nerve enters the obturator region (▶ Fig. 2.6). Just before exiting the pelvis, it divides into an anterior and posterior branch. The anterior branch runs deep to the adductor longus and superficial to the adductor brevis muscle. From this, a sensory branch sprouts extending to the subcutaneous layer to innervate the medial surface of the knee. The anterior branch of the obturator nerve innervates the adductor magnus, gracilis, and adductor brevis muscles. The posterior branch runs downward between the adductor brevis and adductor magnus, innervating both muscles.10,17 In total, the obturator nerve innervates the adductor muscles (longus and magnus, shared with the femoral and sciatic nerves, respectively), the gracilis, pectineus, and obturator externus.18 Between 13 and 40% of individuals have an accessory obturator nerve that stems from L3 and L4 and follows a similar course to that of the anterior branch, innervating the pectineus muscle and hip joint.10,19

Fig. 2.3 Superficial anatomy and topography of the groin region, left side. ASIS, anterosuperior iliac spine; LCFN, lateral cutaneous femoral nerve; VAN, femoral vein, artery, and nerve.

Fig. 2.4 Surgical approach for the lateral cutaneous nerve. Note the nerve retracted with a red silicone band and its two terminal branches.

Clinical Exploration

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Obturator Nerve

Surgical Anatomy and Approaches to the Nerves of the Lower Limb

Fig. 2.5 Groin region, left side (formalin specimen). Located lateral to the femoral vessels are the branches of the femoral nerve. ASIS, anterosuperior iliac spine; LCFN, lateral cutaneous femoral nerve.

Clinical Exploration As their name suggests, hip adductor muscles adduct the thigh and, during normal walking, are crucial flexors of the hip, whereby they initiate each step, causing the trailing leg to swing forward to become the lead leg. The gracilis muscle contributes to flexing the knee and can be used as a donor for free muscle transplants. The obturator externus participates in external rotation of the hip.3 The obturator nerve’s sensory function covers the territory depicted in ▶ Fig. 2.2.

Surgical Approach The obturator nerve is not prone to any specific entrapment syndrome, so there is infrequently any need to access it. When access is required, the surgical approach ultimately selected should be planned taking into consideration the section of nerve involved, as well as the nerve’s anatomical course.

Femoral Nerve The femoral nerve is a mixed motor and sensory nerve that stems from L2–L4.3,18 It descends within the interior of the psoas (innervating it) and then travels through the region of the internal iliac fossa in relation to the caecum and sigmoid (to the right and left, respectively). It can be located here at the angle that forms the iliac and psoas muscles, before traversing behind the inguinal ligament into the thigh. At the level of the inguinal ligament, the nerve and femoral vessels lie as follows: vein, artery, and nerve, from medial to lateral. In the thigh, the nerve is located within the femoral triangle, medial to the sartorius and lateral and in front of the pectineus. In this region, the femoral nerve divides rapidly into its four terminal branches, which are organized in two planes: the

Fig. 2.6 Intrapelvic topography of the obturator nerve and vessels. In this cadaveric specimen, note the obturator vessels and nerve and their relationship with the obturator foramen and internal obturator muscle.

saphenous nerve and the nerve of the quadriceps in the deep plane, and the lateral and medial musculocutaneous nerves in the superficial plane. Even though this is the classical description, the femoral nerve can also reach the thigh already divided into two branches (superficial and deep) or already as its four terminal branches. These four terminal branches are: ● Nerve to the quadriceps: This can be a single nerve or several branches that supply the four different parts of the muscle: the vastus medialis, vastus lateralis, vastus intermedius, and rectus femoris. ● Saphenous nerve: This is a sensory nerve that traverses the entire lower limb, from the inguinal region to the medial aspect of the foot, although it does not give off any branches in the thigh. The nerve follows the femoral artery in the thigh until the knee, where it perforates the superficial fascia and descends toward the medial side of the leg until it reaches the medial border of the foot. ● Medial musculocutaneous nerve: This is a mixed motor–sensory nerve that supplies the pectineus and adductor longus muscles. It gives off cutaneous branches for the skin that lies between the territories of the genitofemoral and obturator nerves. ● Lateral musculocutaneous nerve: Also a mixed nerve, it supplies the sartorius muscle before giving off three perforating branches that innervate the skin of the anterolateral region of the thigh.

Clinical Exploration The motor function of the femoral nerve can be summarized by saying that this nerve allows for flexion of the thigh (via the psoas, iliac, pectineus, and rectus femoris) and extension of the knee (via the quadriceps).20 The territory for sensory function is shown in ▶ Fig. 2.2.

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Surgical Anatomy and Approaches to the Nerves of the Lower Limb

Surgical Approach The femoral nerve can be approached by making a linear, vertical incision, which is located lateral to the pulse of the femoral artery.

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obturator internus, gluteus maximus, piriformis, gastrocnemius, quadratus femoris, and gluteus minimus. It also supplies a collateral branch that travels through the gluteal region and posterior thigh, producing sensory branches for these zones.

2.3 Sacral Plexus

2.3.1 Sciatic Nerve

The sacral plexus is formed by the anterior branches of nerve roots S1–S3 and the lumbosacral trunk (▶ Fig. 2.1). The latter is composed of the union of the anterior branch of L5 and an anastomotic branch of L4. These elements travel in front of the anterior sacral foramen and join inside the pelvis to form a single terminal trunk: the sciatic nerve. Both the plexus and the sciatic nerve are originally situated deep in the pelvis, in front of the sacrum and the sacroiliac joint and behind the rectum. For this reason, traumatic injuries to the sacral plexus and initial part of the sciatic nerve are infrequent and almost always associated with fractures of the sacrum itself. The sacral plexus gives off various collateral branches that mostly supply muscles in the proximal part of the lower limb. It provides muscular branches for the

The sciatic nerve is the thickest and longest nerve in our body. Even though it has traditionally been considered a single nerve, there are actually two nerves with a common epineural sheath. This can be explained by histologic cuts that show that the components of the sciatic nerve (peroneus and tibial) are already separated from its origin with segregation of the motor flexor and extensor functions of the foot.4,21 Once the nerve is formed in the pelvis, it runs backward and passes through the greater sciatic notch, deep to the piriformis muscle, into the gluteal region. Although this is a matter of debate, at this point the nerve can be compressed by aponeurotic bands or variants of the piriformis muscle, giving rise to what is known as “piriformis syndrome” (▶ Fig. 2.7 and ▶ Fig. 2.8).

Fig. 2.7 Anatomic specimen, view of the gluteal region. The greater gluteal muscle is retracted, revealing the piriformis muscle (arrow) and the superior gluteal nerve and vessels (1). Located below the piriformis muscle are the pudendal nerve (2) and the sciatic nerve (3) in close proximity to the inferior gluteal vessels and nerve.

Fig. 2.8 The same specimen as in ▶ Fig. 2.7, after resection of the piriformis muscle. 1, Sciatic nerve; 2, pudendal nerve; 3, superior gluteal vessels and nerve.

Surgical Anatomy and Approaches to the Nerves of the Lower Limb In the gluteal region, the nerve has a descending course within the ischiotrochanteric canal, where it passes in close proximity to the neck of the femur. As such, it can be injured in hip fractures in which any bony fragment is directed posteriorly, as well as during hip replacement surgeries. In the thigh, the nerve descends between the biceps femoris (lateral), semimembranosus, and semitendinosus (medial) muscles and innervates all three. The collateral branches along this section of the nerve mostly originate from the medial border of the nerve (nerves for the semitendinosus, semimembranosus, and adductor magnus) (▶ Fig. 2.9). The lateral border only gives off nerves to the biceps.7 Near the vertex of the popliteal fossa, it divides into its two terminal branches: the common fibular nerve and tibial nerve. This division, however, can sometimes be found at a higher level in the thigh or even within the gluteal region.

Clinical Exploration The sciatic nerve gives off collaterals that innervate the muscles of the posterior region of the thigh, which is why, when examining its motor function, one should ask

the patient to flex the knee. If the sciatic nerve is injured in the gluteal region, there will be paralysis of the muscles innervated by its collateral and terminal branches. However, if the lesion is located at the level of the thigh, some collateral branches may be preserved.

Surgical Approach The proximal portion of the sciatic nerve can be approached in a classic way through a long incision that starts in the gluteal region and is directed laterally, descending to the gluteal fold. The current authors prefer the transgluteal or subgluteal approaches, either alone or combined, due to their better functional and aesthetic results.22 The middle third of the nerve can be approached simply through a linear incision in the midline of the thigh posteriorly. Once the fascia is opened, the nerve can be located easily between the posterior thigh muscles. The inferior third requires a similar incision, but extended to the flexion fold of the knee should the nerve and its terminal branches need to be exposed.23

2.3.2 Terminal Branches of the Sciatic Nerve Tibial Nerve

Fig. 2.9 Popliteal region. 1, Sciatic nerve; 2, common peroneal nerve; 3, tibial nerve; 4, gastrocnemius muscle.

The tibial nerve originates within the superior part of the popliteal fossa and is located medial to the fibular nerve and posterior to the popliteal vessels. It travels along the main axis of the popliteal fossa and enters the posterior compartment of the leg, where it passes deep to the medial and lateral heads of gastrocnemius muscle and to the ring of the soleus (i.e., the upper fibrous border of the muscle). At this level, it gives off motor branches to these muscles. It then takes a somewhat oblique course to end up behind the medial malleolus. In the leg, it gives off the inferior branches for the soleus and its terminal branch: the posterior tibial nerve. This nerve enters an osteofibrotic tunnel located behind the medial malleolus: the tarsal tunnel. In this tunnel, the nerve can be located, along with the posterior tibial vessels and the tendons of the posterior tibial, flexor digitorum, and flexor hallucis longus muscles. In the most distal part of the tunnel, there are fibrotic partitions that “guide” the vessels and nerves to the plantar region. The posterior tibial nerve terminates by dividing into the medial and lateral plantar nerves. It also gives off a calcaneal branch. The medial plantar nerve is large and innervates the muscles of the hallux.8 It also has a branch that runs laterally to innervate the muscles of the middle plantar compartment. The lateral plantar nerve mostly innervates the muscles of the lateral plantar compartment.

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Surgical Anatomy and Approaches to the Nerves of the Lower Limb

Clinical Exploration Through the muscles that it innervates, the posterior tibial nerve produces plantar flexion of the foot and the toes as a whole. It also innervates foot inversion.

Surgical Approach The tibial nerve does not have a specific entrapment neuropathy, so it is approached when it suffers traumatic lesions, the incision made dependent on the location of the lesion itself.

Common Fibular Nerve As the common fibular nerve descends, it follows the medial border of the biceps femoris muscle, lateral to the popliteal vessels and the tibial nerve. More distally, it crosses the superior border of the lateral gastrocnemius and continues forward to follow the contour of the fibular neck. At this point, it is relatively superficial, covered only by the insertion tendon of the peroneal muscles (particularly the peroneus longus) that form an osteomuscular tunnel (peroneal tunnel) where the nerve can be compressed.16,24,25 At this level, the nerve divides into its terminal branches: the superficial and deep fibular nerves. It also gives off the articular branch to the proximal tibiofibular joint that generates the synovial cysts that can affect this portion of the nerve.25

Superficial Fibular Nerve This nerve descends vertically along the lateral aspect of the fibula, between the peroneus longus and peroneus brevis muscles, innervating both. It gradually becomes superficial and, when it reaches the inferior third of the leg, traverses the superficial fascia to divide into two sensory branches that innervate the lateral surface of the leg and dorsal surface of the foot.

Deep Fibular Nerve Like the superficial fibular nerve, the deep fibular nerve originates in the peroneal tunnel. From there, it follows a descending path to enter the anterior compartment of the leg. It then runs alongside the anterior tibial artery that passes above the interosseous ligament. In the anterior compartment of the leg, the nerve supplies the muscles of the region (tibialis anterior, extensor digitorum, and extensor hallucis longus), becoming superficial as the muscle bodies become tendons. Within the inferior third of the leg, it is located between the tibialis anterior and extensor hallucis longus, where it gives off articular branches to the tibiotarsal joint and passes beneath the superior extensor retinaculum. It terminates in a medial and lateral branch. The former is considered a continuation of the deep fibular nerve and follows the axis of the

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first interosseous space in close proximity to the pedal artery and muscle.

Clinical Exploration The fibular nerve innervates extension and eversion of the foot. Lesions affecting the nerve produce a typical gait, associated with a dropped foot, which is often called a “steppage gait.”

Surgical Approach The fibular nerve can become entrapped within the peroneal tunnel. In such patients, it can be approached through an S-shaped incision created just distal to the fibular head.23,24

References [1] Bouchet A, Cuilleret J. Anatomía descriptiva, topográfica y funcional. Miembros Inferiores. Buenos Aires: Panamericana; 1979:296 [2] Carpenter MB. Neuroanatomía humana. 7th ed. Buenos Aires: El Ateneo; 1985:174–177 [3] Lazorthes G. Le sistème nerveux pèriphérique. Paris: Masson et Cie Èditeurs; 1955 [4] Lucien M. Le carrefour sciatique du plexus crural. Compt Rend Assoc Anat. 1956:967–971 [5] Martinez F, Bonilla G, Pinazzo S. Anatomía del sistema nervioso periférico. Parte II: Inervación del miembro inferior. In: Socolovsky M, Siqueira M, Malessy M, eds. Introducción a la cirugía de los nervios periféricos. Buenos Aires: Ediciones Journal; 2013:19–32 [6] Pro A. Anatomía Humana de Latarjet-Ruiz Liard. Buenos Aires: Editorial Panamericana; 2004 [7] Rigoard P, Buffenoir-Billet K, Giot JP, d’Houtaud S, Delmotte A, Lapierre F. Bases anatomiques des voies d’abord chirurgicales des nerfs du membre inférieur: à l’usage des jeunes neurochirurgiens. Neurochirurgie. 2009; 55(4–5):375–383 [8] Rouviere H, Delmas A. Anatomía humana. Tomo 3: Miembros. 11th ed. Mexico: Masson; 2005:525–644 [9] Laha RK, Rao S, Pidgeon CN, Dujovny M. Genito-femoral neuralgia. Surg Neurol. 1977; 8(4):280–282 [10] Russell SM. Examination of Peripherals Nerve Injuries. An Anatomical Approach. New York, NY: Thieme; 2006:108–163 [11] Vanderlinden RG, Midha R. Ilioinguinal/iliohipogastric neuropathy. In: Midha R, Zager EL, eds. Surgery of Peripheral Nerves. A CaseBased Approach. New York, NY: Thieme; 2008:163–166 [12] Viswanathan A, Kim DH, Reid N, Kline DG. Surgical management of the pelvic plexus and lower abdominal nerves. Neurosurgery. 2009; 65(4)(Suppl):A44–A51 [13] Cook D, Midha R. Meralgia paresthetica. In: Midha R, Zager EL, eds. Surgery of Peripheral Nerves. A Case-Based Approach. New York, NY: Thieme; 2008:167–170 [14] Mattera D, Martinez F, Soria V, et al. Surgical anatomy of the lateral femoral cutaneous nerve in the groin region. Eur J Anat. 2008; 12(1): 33–37 [15] de Ridder VA, de Lange S, Popta JV. Anatomical variations of the lateral femoral cutaneous nerve and the consequences for surgery. J Orthop Trauma. 1999; 13(3):207–211 [16] Peri G. The “critical zones” of entrapment of the nerves of the lower limb. Surg Radiol Anat. 1991; 13(2):139–143 [17] Kitagawa R, Kim D, Reid N, Kline D. Surgical management of obturator nerve lesions. Neurosurgery. 2009; 65(4)(Suppl):A24–A28 [18] Spiliopoulos K, Williams Z. Femoral branch to obturator nerve transfer for restoration of thigh adduction following iatrogenic injury. J Neurosurg. 2011; 114(6):1529–1533

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Surgical Anatomy and Approaches to the Nerves of the Lower Limb [19] Huang JH, Whitmore RG, Zager EL. Obturator nerve injury and repair. In: Midha R, Zager EL, eds. Surgery of Peripheral Nerves. A CaseBased Approach. New York, NY: Thieme; 2008:171–174 [20] Kapandji AI. Cuadernos de fisiología articular. Tomo II: Miembro inferior. 5th ed. Madrid: Panamericana; 2007 [21] Straja A. Anestesia locorregional del miembro inferior. In: Lafaye PG, ed. Anestesia Regional. Barcelona: Masson; 1986:109–128 [22] Socolovsky M. Estudio anatómico y microquirúrgico del abordaje transmuscular a la porción proximal del nervio ciático mayor. Tesis de Doctorado, Facultad de Medicina de la Unidad de Buenos Aires; 2010:76 [23] Steinmetz MP, Mason AM, Lastra-Powera JJ, Benzel EC. Abordaje quirúrgico de los nervios periféricos de la extremidad inferior.

Parte 1: Nervio ciático y sus ramas (nervios peroneos y tibial posterior). In: Wolfla CE, Resnick DK, eds. Atlas de procedimientos neuroquirúrgicos. Columna y nervios periféricos. Caracas: Segunda Edición, Amolca; 2009:372–377 [24] Martínez F, Pinazzo S, Moragues R, et al. Neuropatía del nervio peroneo secundaria a paraganglioma paraneural. Reporte de caso. Rev Chil Neurocirugía. 2013; 39:61–64 [25] Van den Bergh FRA, Vanhoenacker FM, De Smet E, Huysse W. Verstraete KL. Peroneal nerve: Normal anatomy and pathologic findings on routine MRI of the knee. Insights Imaging. 2013; 4(3): 287–299

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Nerve Injuries: Anatomy, Pathophysiology, and Classification

3 Nerve Injuries: Anatomy, Pathophysiology, and Classification Bassam M. J. Addas Abstract Understanding the normal anatomy and the pathophysiology of peripheral nerve injury is of paramount importance to the clinician who deals with peripheral nerves. This knowledge allows reaching the optimal recovery. The causes of nerve injuries are many; however, they share common basic pathophysiological processes. Traction and laceration injuries are the commonest traumatic mechanism with completely different approach to treatment. Entrapment neuropathy is the commonest nontraumatic nerve injury encountered in clinical practice. Rare forms of nerve injuries are briefly addressed in this chapter. Overall, this chapter focuses mainly on the practical approach to different pathological processes involving peripheral nerves based on well-established basic pathophysiological knowledge.

Keywords: peripheral nerves, traction injury, laceration injury, entrapment neuroma in continuity

3.1 Anatomy of the Peripheral Nerves The basic anatomy of the peripheral nerves is illustrated in ▶ Fig. 3.1a, b. In simple terms, the axon is the basic unit of the peripheral nervous system, surrounded by myelin that is produced by Schwann cells. Axons are grouped together in a fascicle, and the fascicles constitute the main nerve trunk. Endoneurium surrounds the axons, perineurium surrounds the fascicles, and epineurium surrounds the main nerve trunk. Epineurium (fibrovascular stroma) is the most outer layer of the peripheral nerve Fig. 3.1 (a) Schematic drawing of the basic structure of normal peripheral nerves. (b) The essential elements of the three layers of peripheral nerves.

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Nerve Injuries: Anatomy, Pathophysiology, and Classification trunk, composed mainly of collagen type I and III. Epineurium gives the nerve trunk its flexibility, allowing stretch up to 15 to 20% of its length. Thickness of the epineurium varies from one nerve to the other and it is generally more abundant near joints. Major nerve blood vessels, lymphatics, mast cells, and fibroblasts can be seen in this layer. Perineurium is a specialized layer formed by multiple layers of flattened perineurial cells and acts as a diffusion barrier. It also provides a protective environment to the underlying endoneurium. Endoneurium is the most inner compartment that surrounds axons, Schwann cells, macrophages, and capillaries. The tight junctions of the endoneurium capillaries form the “blood–nerve barrier.” Schwann cells, the most essential component of regeneration of axons, are present only in the endoneurium.1 Nerves are subjected to trauma by many different mechanisms, traction and laceration injury being the most common traumatic mechanisms. Different, less common, and rare forms of injury can also lead to significant nerve dysfunction, pain, and disability (▶ Table 3.1). To be able to offer the best management in a timely fashion, it is essential to understand the different pathophysiological processes related to each mechanism of injury.

3.2 Traction Injury Traction injury is a common mechanism of injury affecting peripheral nerves; traumatic and birth-induced plexus injuries represent classical examples of traction injury. According to the severity of injury in form of traction, pathological changes take place within the nerve. The grading of nerve injury is classically accredited to Seddon

Table 3.1 Mechanisms of nerve injuries ●

Traction (stretch, rupture, and avulsion)

●

Laceration (sharp and blunt)

●

Entrapment

●

Pressure

●

Ischemic/compartment

●

Injection injury

●

Radiation injury

●

Electrical

●

Thermal

and Sunderland. Seddon2 first described three well-defined types of nerve injury: neuropraxia (conduction block), axonotmesis (neuroma-in-continuity), and neurotmesis (nerve division). Sunderland3 followed Seddon by a fivepoint grading system in ascending order of severity with both anatomical and functional correlations (▶ Table 3.2). These injuries may not be of uniform severity. Different grades can be present in the same segment of the nerve and different grades can be present along the course of the nerve. This classification is based on the effect of the injury on the nerve and not necessary the mechanism of injury, as this pattern can be caused by stretch, thermal, or ischemic mechanisms. Sunderland grade I (neuropraxia) is characterized by conduction block, with usually an excellent recovery. Early in the process, the involved muscles are weak/ paralyzed, and sensory loss is evident, particularly for touch and proprioception; pain is usually more resistant. Autonomic function is usually not affected. Wasting of muscles is not common and is a useful clinical clue. The exact duration of neuropraxia is debatable; however, it may range from 1 to 4 months, with an average of 2 months in most cases. Sunderland grade II nerve injury is characterized by loss of axons with preservation of the endoneurial tube. Clinically, this is manifested by complete loss of motor, sensory, and autonomic functions. Because of the intact endoneurium, the regenerating axons find its old path and reach their targets. The time to recovery depends on the level of injury—the more proximal the lesion, the longer the time for recovery. Regenerating axons travel in a speed of 1 to 3 mm/day. Tourniquet injury is believed to be a combination of grade I and II.4,5 Sunderland grade III nerve injury combines grade II and endoneurial tube disruption. The perineurium is intact or minimally involved. This pattern means that the fascicles are preserved as tubes but their inside is “messed up.” Trauma inside the fascicles may cause hemorrhage, edema, ischemia, and eventually fibrosis. Fibrosis constitutes the main barrier for the regenerating axons. The scar created also can cause rerouting of the regenerating axons, not reaching their original targets; this is more evident in mixed fascicles with motor and sensory axons compared to pure motor fascicles. This nature of mixed nerve can explain why grade III injury of the median nerve (mixed nerve) at the arm level is different from grade III injury of the radial nerve (mostly

Table 3.2 Grading of peripheral nerve injuries Sunderland grade

Seddon grade

Pathological features

I

Neuropraxia

Conduction block, myelin loss

Excellent

II

Axonotmesis

Axon loss

Very good

III

Grade II and endoneurium loss

Variable

IV

Grade III and perineurium loss

Poor/no recovery

Nerve trunk disruption

No recovery

V

Neurotmesis

Clinical outcome

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Nerve Injuries: Anatomy, Pathophysiology, and Classification

Fig. 3.2 Intraoperative photograph depicting the cut section in the middle of nonconducting neuroma of the sciatic nerve showing complete loss of internal architecture with the formation of dense fibrous scar.

motor) at the same level. In proximal lesions, retrograde neuronal degeneration is more pronounced compared to grade II, making recovery of grade III injuries significantly worse. Also, the chance for axonal misdirection is higher, affecting the extent and quality of recovery. Sunderland grade IV nerve injury (fascicular disruption) occurs in nerves subjected to higher forces, with complete and more severe disorganization of the fascicles (▶ Fig. 3.2), with no or very little recovery that is usually nonfunctional. Sunderland grade V nerve injury (neurotmesis) represents a severed, discontinuous nerve. This mode of injury is not commonly seen in traction injuries at the level of the nerve trunk and is usually caused by lacerations. Grades I and II are not surgical lesions and usually recover spontaneously. They can be found in association with more severe lesions of grades III and IV (neuromain-continuity) involving other nerves. They usually show positive nerve action potential (NAP) following external neurolysis. In cases of neuroma-in-continuity (grade III and IV), the affected nerve segment is isolated; if no NAP or nerve stimulation is present, the neuroma is resected and either primarily repaired or grafted (▶ Fig. 3.3).

3.3 Laceration Injury It has been estimated that laceration injury to the limbs, caused by knifes or sharp objects, causes transection of the underlying nerves in 30% of the cases.6,7 This percentage depends on the injury location. Volar wrist laceration injury will cause median or ulnar nerve injury in the majority of cases. Sharp injuries to different areas of the body may not necessary transect the underlying nerve, yet can cause a temporary loss of function depending on the degree of injury. In clean sharp lacerations, there is a minimal contusive injury, bruises, or hemorrhage in the proximal and distal stumps. Both stumps form neuromas

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Fig. 3.3 Intraoperative photograph demonstrating the technique of slicing the nonconducting neuroma starting from the center and going proximally and distally until reaching the normal fascicular pattern for repair.

and retract and adhere to the underlying tissues. Both ends may remain attached by thin, fibrous tissue or normal part of the partially preserved fascicles (▶ Fig. 3.4). Retraction can progress with time because of limb movement, and usually stopped by the next distal branch. Significant retraction is usual in median and ulnar nerve injuries at the arm level because of lack of branches of both nerves at this level. Both stumps usually remain in the same plane but may change location according to the adherence to nearby tissues (▶ Fig. 3.5). In blunt lacerations caused by blunt objects (motor blades, machinery, chainsaw), irregular, ragged tears of the nerve trunk occur; this causes bruises and hemorrhages along both ends for some distance, making identification of healthy end difficult (▶ Fig. 3.6). It is a good practice to explore sharp injuries causing complete loss of function of the underlying nerves, as this gives the best chance for good recovery. In cases of blunt lacerations or contaminated wounds or large wounds with soft-tissue loss, delayed repair (4–6 weeks) is advised allowing the edematous, bruised ends of the nerve to heal and therefore delineating the zone between the normal and the abnormal parts of the nerve, allowing better reconstruction with either end-to-end or, more commonly, graft repair.

3.4 Compression/Pressure Injury Carpal tunnel and cubital tunnel syndromes are the most common surgical conditions that surgeons face on a regular basis. Abnormal compression of nerves as they

Manual of Peripheral Nerve Surgery | 25.07.17 - 10:00

Nerve Injuries: Anatomy, Pathophysiology, and Classification

Fig. 3.4 Intraoperative photograph of sharp, near-completely lacerated common peroneal nerve 1 month following injury, showing minimal distal and proximal stump changes.

Fig. 3.5 Exposure of the common peroneal nerve following gunshot wound to the popliteal fossa showing the proximal stump (P) ends into an attenuated, fibrous scar at a different plane from the distal end (D).

Fig. 3.6 Blunt laceration of the ulnar nerve at the forearm level caused by a chainsaw. Note the severely lacerated, contused, hemorrhagic, and edematous ends making meaningful repair difficult.

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Nerve Injuries: Anatomy, Pathophysiology, and Classification run in their natural courses can lead to dysfunction. Deficit depends mainly on the degree and the duration of the compression. Ischemia and mechanical distortion are found to be the most common responsible mechanisms.8,9,10 When severe and prolonged ischemia produce axonal loss and Wallerian degeneration, Lundborg had found that if the ischemia is prolonged for more than 8 hours, an irreversible damage will take place.11 Chronic compression of the nerves produces a characteristic changes that are quite unique in form of alteration in paranodal myelination, axonal thinning, and segmental demyelination.12 Severe and neglected compression will eventually lead to Wallerian degeneration. Generally, in entrapment syndromes, symptoms start with pain, and only if compression is prolonged, muscle weakness becomes evident. Recovery of nerve compression varies; generally, most of the pressure neuropathies caused by anesthesia positioning will eventually recover without surgical intervention.13 This is also true for most of neuropathy produced by the use of tourniquets. Pressure neuropathies caused by hematomas because of anticoagulant therapy represents a dilemma, and surgical decision should be evaluated according to every case. Delaying evacuation and repair of pseudoaneurysms causing compression and producing new neurological symptoms may produce long-lasting deficits.14 Compartment syndrome is the most severe form of compression and produces ischemic necrosis that extends beyond the nerves and involves muscles, tendon, and soft tissues—the commonest scenario being brachial artery injury in children with supracondylar fractures. If the flow of the brachial artery is not restored in a timely fashion, ischemia to the forearm nerves and muscles of the volar forearm surface will occur, and if fasciotomy is not performed urgently, the already swollen muscles and surrounding structures, including swollen nerves, will become necrotic. Necrosis of nerves usually involves long segment, making nerve repair options less realistic.15

3.5 Injection Injury Although it seems largely avoidable and preventable, injection injury to the peripheral nerves remains a common problem particularly in the developing countries. Extremes of age groups are usually the victims.16 Because the gluteal muscle is the commonest site of injection, the sciatic nerve is clinically the commonest nerve involved. The two most important determinants of the degree of injury are the site of injection (outside epineurium vs. inside epineurium) and the nature of the injected material. The puncture injury of the needle is wrongly blamed for the cause of the injury. Pathological changes vary according to the injected material as there are some highly toxic chemicals such as penicillin, gentamicin, and diazepam. Less toxic chemicals can also produce significant damage if injected in large quantities. When injected

22

inside the epineurium, acute edema takes place, followed by inflammatory changes and eventually necrosis. This produces a scar, creating axonal block and nerve dysfunction. Blood–nerve barrier is also disrupted, worsening the damage and further allowing more edema formation. Injections outside the epineurium are usually less damaging to the nerve architecture, but may evoke an inflammatory response and cause scar formation and adhesions to the overlying gluteal muscles. Leakage of the injected material from the site of injection to the vicinity of the nerve may be the explanation of the delayed symptoms that some patients report. Most cases show improvement on conservative management.17 The tibial component recovers more quickly than the common peroneal component. Exploration is advised if no improvement is evident in 6 months’ time. Usually, the sciatic nerve is grossly normal with or without NAP recorded. The surrounding tissue usually does not show much of any reaction. Moderate to severe adhesions are rarely seen surrounding the nerve. In some cases, the nerve is stuck to the posterior surface of the gluteal muscle. Primary or secondary repair is rarely needed in the author’s experience.

3.6 Rare Forms of Peripheral Nerve Injuries 3.6.1 Electrical Injuries This type of injury is commonly associated with high-voltage injuries that result in death, and peripheral nerve injury is usually the least of the concerns; this makes the available cases of nerve injury rare, and therefore no uniform or clear strategy of management is available. Electrical current produces tissue damage by heating tissue. The more the current and the duration of exposure, the more the heat generated and therefore the damage. Resistance of tissues increases in the following order: nerves, blood vessels, muscles, skin, tendons, fat, and bones, nerves being the most vulnerable.18,19 The commonest clinical scenario encountered is a young boy electrocuted following holding a high-voltage wire. The electrical current burns his hand and exits from the forearm or the trunk, with the median and ulnar nerves being the commonly affected nerves (▶ Fig. 3.7). The principal pathological change in the nerve is coagulative necrosis, which is subsequently replaced by fibrous scar. When indicated, surgical exploration following a period of no recovery will delineate the zone of injury, and the prognosis of recovery will depend on the length of the segment involved. If there is a large area of soft-tissue loss, including muscles, muscle or tendon transfers may be a more logical surgical option.

3.6.2 Thermal Injury Burning nerves by flames or hot metals may result is neural damage. This depends on the level of the heat and the

Nerve Injuries: Anatomy, Pathophysiology, and Classification benefit some patients.24 Nerve transfer can be used in a few selected cases.25

References

Fig. 3.7 Electrical injury in a young boy following holding of a high-current metal wire, burning the palm of both hands and exiting from the volar aspect of the distal forearm causing partial median and ulnar nerve injury.

duration of exposure. The nerve can be compressed initially because of edema and fasciotomy may be necessary.20 Compression of neural elements may occur later following fibrous tissue development. Patients with circumferential burns will be the most susceptible group for this form of compression neuropathy as the surrounding fibrosis may produce a tourniquet-like effect.

3.6.3 Radiation Injury With the refinement of the radiotherapy techniques, this form of neuropathy is reduced. It is dose-dependent and more than 70% of patients who receive more than 6,000 rad will eventually suffer radiation neuropathy.21 It usually involves the upper part of brachial plexus in patients receiving radiation for breast cancer treatment.22,23 Symptoms may start few months to several years following the treatment. The pathological changes consist of extensive endoneurial fibrosis, with axonal degeneration. Changes in blood vessels are universal. Surgery is indicated if there is a question between metastatic and radiation brachial plexopathy. Pain is another indication for surgery when medical treatment fails. External neurolysis with excision of the surrounding scar may

[1] Scheithauer B, Woodruff J, Erlandson R, eds. Atlas of Tumor Pathology: Tumors of the Peripheral Nervous System. 1st ed. Washington, DC: Armed Forces Institute of Pathology; 1999 [2] Seddon HJ. Three types of nerve injury. Brain. 1943; 66(4):237–288 [3] Sunderland S. A classification of peripheral nerve injuries producing loss of function. Brain. 1951; 74(4):491–516 [4] Ochoa J, Danta G, Fowler TJ, Gilliatt RW. Nature of the nerve lesion caused by a pneumatic tourniquet. Nature. 1971; 233(5317):265– 266 [5] Ochoa J, Fowler TJ, Gilliatt RW. Anatomical changes in peripheral nerves compressed by a pneumatic tourniquet. J Anat. 1972; 113(Pt 3):433–455 [6] Kline DG. Physiological and clinical factors contributing to the timing of nerve repair. Clin Neurosurg. 1977; 24:425–455 [7] Sunderland S. Nerve and Nerve Injuries. Baltimore, MD: Williams & Wilkins; 1968 [8] Eames RA, Lange LS. Clinical and pathological study of ischaemic neuropathy. J Neurol Neurosurg Psychiatry. 1967; 30(3):215–226 [9] Williams IR, Jefferson D, Gilliatt RW. Acute nerve compression during limb ischaemia–an experimental study. J Neurol Sci. 1980; 46(2): 199–207 [10] Lundborg G. Nerve Regeneration. Nerve Injury and Repair. London: Churchill Livingstone; 1988:149–195 [11] Lundborg G. Ischemic nerve injury. Experimental studies on intraneural microvascular pathophysiology and nerve function in a limb subjected to temporary circulatory arrest. Scand J Plast Reconstr Surg Suppl. 1970; 6:3–113 [12] Aguayo A, Nair CP, Midgley R. Experimental progressive compression neuropathy in the rabbit. Histologic and electrophysiologic studies. Arch Neurol. 1971; 24(4):358–364 [13] Addas BM. An uncommon cause of brachial plexus injury. Neurosciences (Riyadh). 2012; 17(1):64–65 [14] Roganović Z, Misović S, Kronja G, Savić M. Peripheral nerve lesions associated with missile-induced pseudoaneurysms. J Neurosurg. 2007; 107(4):765–775 [15] Spinner M. Injuries to the Major Branches of Peripheral Nerves of the Forearm. 2nd ed. Philadelphia, PA: WB Saunders; 1978 [16] Villarejo FJ, Pascual AM. Injection injury of the sciatic nerve (370 cases). Childs Nerv Syst. 1993; 9(4):229–232 [17] Kline DG, Kim D, Midha R, Harsh C, Tiel R. Management and results of sciatic nerve injuries: a 24-year experience. J Neurosurg. 1998; 89(1): 13–23 [18] DiVincenti FC, Moncrief JA, Pruitt BA, Jr. Electrical injuries: a review of 65 cases. J Trauma. 1969; 9(6):497–507 [19] Grube BJ, Heimbach DM, Engrav LH, Copass MK. Neurologic consequences of electrical burns. J Trauma. 1990; 30(3):254–258 [20] Salzberg CA, Salisbury RE, Gelberman RH. Thermal Injury of Peripheral Nerve. Operative Nerve Repair and Reconstruction. Philadelphia, PA: J.B. Lippincott Company; 1991:671–678 [21] Powell S, Cooke J, Parsons C. Radiation-induced brachial plexus injury: follow-up of two different fractionation schedules. Radiother Oncol. 1990; 18(3):213–220 [22] Bowen BC, Verma A, Brandon AH, Fiedler JA. Radiation-induced brachial plexopathy: MR and clinical findings. AJNR Am J Neuroradiol. 1996; 17(10):1932–1936 [23] Clodius L, Uhlschmid G, Hess K. Irradiation plexitis of the brachial plexus. Clin Plast Surg. 1984; 11(1):161–165 [24] Lu L, Gong X, Liu Z, Wang D, Zhang Z. Diagnosis and operative treatment of radiation-induced brachial plexopathy. Chin J Traumatol. 2002; 5(6):329–332 [25] Addas BM, Midha R. Nerve transfers for severe nerve injury. Neurosurg Clin N Am. 2009; 20(1):27–38, vi

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Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

4 Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb Javier Robla Costales, Luis Domitrovic, David Robla Costales, Javier Fernández Fernández, and Javier Ibáñez Plágaro Abstract An accurate physical examination of a patient with a peripheral nerve injury provides enough information to establish the level of the lesion and the nerve(s) that is (are) affected. Peripheral nerves in the upper limb originate from the brachial plexus, and they are the musculocutaneous nerve, the median nerve, the ulnar nerve, and the radial nerve. This chapter offers a concise summary of the information and key points needed to do an accurate physical examination of the peripheral nerves of the upper limb. Keywords: peripheral nerve injury, brachial plexus, peripheral nerve surgery, physical examination, upper limb

4.1 Introduction An accurate physical examination of a patient with a peripheral nerve injury generally provides enough information to establish the level of the lesion and identify which nerves are affected. It is also important to monitor any improvement in nerve function over the course of follow-up. This chapter offers a concise summary of the information and key points needed to perform an accurate physical examination of the peripheral nerves in the upper limb. Anatomy of peripheral nerves in the upper limb is only mentioned as needed to explain certain issues; a thorough review of upper limb nerve anatomy is provided in Chapter 1.

All the peripheral nerves in the upper limb originate in the brachial plexus. Excluding branches, there are four nerves: the musculocutaneous nerve, the median nerve, the ulnar nerve, and the radial nerve.

4.2 Musculocutaneous Nerve Transformation of the medial and lateral cords of the brachial plexus into their terminal branches is M-shaped. The lateral leg of the letter M is the musculocutaneous nerve (▶ Fig. 4.1). The first muscle that the musculocutaneous nerve innervates is the coracobrachialis muscle. It assists the anterior deltoid with shoulder flexion (lifting the arm forward in front of one’s body), and it also stabilizes the humerus during elbow flexion. The coracobrachialis cannot be isolated or readily palpated. Therefore, it is not examined clinically. After passing through and then deep to the coracobrachialis, the musculocutaneous nerve innervates the brachialis muscle and the biceps brachii muscle (▶ Fig. 4.2). The biceps brachii, with the assistance of the brachialis and brachioradialis (innervated by the radial nerve), flexes the elbow. The biceps brachii is also a strong supinator of the forearm when the elbow is flexed. To test the biceps brachii and brachialis, have the patient flex a fully supinated forearm against resistance. Contribution from the brachioradialis (radial nerve) is minimized by performing this test with the patient’s forearm in full supination (▶ Fig. 4.3).

Fig. 4.1 Anatomy of brachial plexus and peripheral nerves.

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Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

Fig. 4.2 Anatomy of the musculocutaneous nerve.

The brachialis muscle receives some innervation from the radial nerve (in addition to its main innervation from the musculocutaneous nerve). However, this innervation is usually not enough to flex the arm in the presence of musculocutaneous nerve palsy. Distal to the branches to the biceps brachii and the brachialis muscle, the musculocutaneous nerve continues as the lateral antebrachial cutaneous nerve. The territory of this sensory nerve includes, as the name implies, the lateral half of the forearm (▶ Fig. 4.4). Isolated musculocutaneous palsies are rare, but can occur following shoulder trauma or dislocation. These patients present with numbness on the surface of their anterolateral forearm, along with elbow flexion weak-

ness. These findings need to be clinically differentiated from a biceps tendon rupture, as well as from a C6 radiculopathy. Following a tendon rupture, the biceps still contracts and can be felt rolling up the arm. A C6 radiculopathy is identified not only because of the radicular pain, but also because of possible weakness in other, nonmusculocutaneous innervated C6 muscles, including the brachioradialis and latissimus dorsi. Furthermore, C6 radiculopathies usually cause numbness confined to the thumb and index finger, whereas the sensory coverage of the lateral antebrachial cutaneous nerve stops at the wrist. Focal damage to the lateral antebrachial cutaneous nerve can occur during venipuncture in the antecubital fossa.

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Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

Fig. 4.4 Musculocutaneous nerve. Lateral antebrachial cutaneous nerve innervation.

Fig. 4.3 Musculocutaneous nerve. Biceps brachii examination.

4.3 Median Nerve The median nerve is derived from the lateral and medial cords of the brachial plexus, with the lateral cord providing mostly sensory axons from C6 and C7, and the medial cord mostly motor axons from C8 and T1 (▶ Fig. 4.1). The median nerve remains slightly lateral and superficial to the brachial artery as it travels down the arm. About halfway down the upper arm, the median nerve crosses over the top of the brachial artery, to lie just medial to it by the time it passes under the bicipital aponeurosis (lacertus fibrosis) in the proximal forearm. The median nerve travels down the center of the forearm deep to the flexor digitorum superficialis, but superficial to the underlying flexor digitorum profundus (FDP; ▶ Fig. 4.5). About one-third to halfway down the forearm, an important branch of the median nerve exits: the anterior interosseous nerve (AIN). Once formed, the AIN passes deeper within the forearm and terminates in the distal forearm deep to the pronator quadratus. As the median nerve continues down the forearm, it becomes superficial about 5 cm proximal to the wrist. Before entering the

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hand, the median nerve gives out a pure sensory branch—the palmar cutaneous branch—which runs superficial to the carpal tunnel and ramifies over the thenar eminence. The median nerve passes through the center of the wrist within the carpal tunnel. After it passes through the carpal tunnel, the median nerve gives a branch off on its radial side: the thenar motor branch (or recurrent thenar motor branch). Next, in the deep palm, the median nerve splits into two divisions: radial and ulnar. The radial division divides into the common digital nerve to the thumb and the proper digital nerve to the radial half of the index finger. The common digital nerve to the thumb subsequently divides into the two proper digital nerves to the thumb. The ulnar division of the median nerve divides into the common digital nerves of the second and third web spaces, which also subsequently divide into proper digital nerves.

4.3.1 Motor Innervation The median nerve innervates no muscles in the upper arm. However, it innervates numerous muscles in the forearm and hand that control forearm pronation, wrist flexion, flexion of the digits (especially the first three), and thumb opposition and abduction. To facilitate memorization, these muscles can be separated into four groups: proximal forearm, anterior interosseous, thenar motor, and terminal group.

Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

Fig. 4.5 Anatomy of the median nerve.

The Proximal Forearm Group Four muscles form this group: the pronator teres, flexor carpi radialis, flexor digitorum superficialis, and palmaris longus. The pronator teres is the main pronator of the forearm and the first muscle innervated by the median nerve. Branches to the pronator teres exit the median nerve in the lowest part of the upper arm, before the median nerve passes between the two heads of the pronator teres. To test this muscle, the elbow should be extended with the forearm fully pronated. The patient is then instructed to resist forced supination by the examiner (▶ Fig. 4.6a). The flexor carpi radialis is the more important wrist flexor. Wrist flexion is done through contraction of the flexor carpi radialis (median nerve) and flexor carpi ulnaris (ulnar nerve). Loss of flexor carpi radialis function severely limits wrist flexion, but not toward the ulnar side. Test the flexor carpi radialis by having the patient flex the wrist toward the anterior aspect of the forearm (▶ Fig. 4.6b). During wrist flexion, the flexor carpi radialis

tendon can be observed and palpated proximal to the wrist. The palmaris longus corrugates the palmar skin. This muscle is not readily examined for muscular strength; in fact, it is absent in roughly 15% of the population. The flexor digitorum superficialis flexes all the fingers, except the thumb, at their proximal interphalangeal joint. To assess proximal interphalangeal joint flexion, each finger is tested separately. Placing your fingers between the single finger to be tested and the remaining fingers isolates this movement (▶ Fig. 4.6c). This position places the finger to be tested in mild flexion at the metacarpal– phalangeal joint and stabilizes the remaining fingers in extension, a position that allows for isolation of the flexor digitorum superficialis.

The Anterior Interosseous Group The AIN innervates three forearm muscles: the FDP (to the second and third digits), the flexor pollicis longus, and the pronator quadratus. Although the AIN gives

27

Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

Fig. 4.6 Median nerve. The proximal forearm group: (a) pronator teres, (b) flexor carpi radialis, (c) flexor digitorum superficialis.

sensory innervation to the distal radioulnar, radiocarpal, intercarpal, and carpometacarpal joints, it provides no cutaneous innervation. The median and ulnar nerves innervate the FDP. The median nerve controls flexion of the distal interphalangeal joint of the second and, partly, the third digits; the ulnar nerve controls this muscle’s action upon the third (partly), fourth, and fifth digits. Distal interphalangeal joint flexion of the third (or long) digit has variable dominance, in terms of innervation from the median versus ulnar nerve. Therefore, to assess median innervation of the FDP in isolation, one must concentrate on the index finger. To do so, hold the metacarpophalangeal and proximal interphalangeal joints immobile and have the patient flex the distal phalanx against resistance (▶ Fig. 4.7a). The flexor pollicis longus flexes the distal phalanx of the thumb at the interphalangeal joint. Assess the flexor pollicis longus by immobilizing the thumb, except for the interphalangeal joint, and asking the patient to flex the distal phalanx against resistance (▶ Fig. 4.7b). A quick way to assess both FDP and flexor pollicis longus innervation from the AIN is to ask the patient to make an okay sign by touching the tips of the thumb and index finger together. When these muscles are weak, the distal phalanges of the thumb and index finger cannot flex;

28

consequently, instead of the fingertips touching, the volar surfaces of each distal phalanx make contact (▶ Fig. 4.7d). The third muscle innervated by the AIN is the pronator quadratus. This is a significantly weaker forearm pronator than the pronator teres. In fact, weakness of the pronator quadratus is often not readily apparent when the pronator teres is strong. However, fully flexing the forearm at the elbow removes the mechanical advantage of the pronator teres; and, in this position, weakness of the pronator quadratus should be detectable when compared against the normal arm (▶ Fig. 4.7c).

The Thenar Group The thenar motor branch of the median nerve innervates three muscles: the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis. There are two types of thumb abduction: palmar abduction away from the plane of the palm (mediated by the abductor pollicis brevis) and radial abduction away from the line of the forearm (mediated by the abductor pollicis longus). Therefore, even with complete palsy of the abductor pollicis brevis, radial abduction of the thumb can still occur. To test the abductor pollicis brevis, resist movement of the thumb away from the plane of

Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

Fig. 4.7 Median nerve. The anterior interosseous group: (a) flexor digitorum profundus (to the second and third digits), (b) flexor pollicis longus, (c) pronator quadratus, (d) okay sign.

Fig. 4.8 Median nerve. The thenar group: (a) abductor pollicis brevis, (b) flexor pollicis brevis, (c) opponens pollicis.

the palm (palmar abduction) while the hand is immobilized (▶ Fig. 4.8a). The flexor pollicis brevis has both a deep and superficial head. The superficial head is innervated by the median nerve and the deep head by the ulnar nerve. This muscle flexes the thumb at the metacarpophalangeal joint. To test the flexor pollicis brevis, immobilize the thumb’s interphalangeal joint and have the patient flex at the metacarpal–phalangeal joint (▶ Fig. 4.8b). Make certain that the distal interphalangeal joint is blocked for flexion because, if it is allowed, substitution by the flexor pollicis longus may occur. Also use

your other hand to immobilize the first metacarpal to reduce substitution by the opponens pollicis. Because the flexor pollicis brevis is dually innervated, some thumb flexion can still occur with median nerve palsy. To assess the opponens pollicis, have the patient forcibly maintain contact between the fingertips of the thumb and fifth digit while you try to pull the first metacarpal away from the fifth digit (▶ Fig. 4.8c). Although the median nerve independently controls thumb opposition, a combination of thumb adduction (adductor pollicis; ulnar nerve) and thumb flexion (flexor pollicis brevis;

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Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb deep head, ulnar nerve) may mimic thumb opposition when median nerve palsy is present. The key to exploring motor function in the thumb is to compare it against the normal hand. This is because, even after complete loss of median nerve function, some movement of the thumb may occur either secondary to true muscle action via radial and ulnar innervations or through substitution by adjacent muscles.

The Terminal Group The terminal group consists of the first and second lumbricals, which are innervated by the terminal radial and ulnar divisions of the median nerve, respectively. To examine the first lumbrical, stabilize the index finger in a hyperextended position at the metacarpophalangeal joint and then provide resistance as the patient extends the finger at the proximal interphalangeal joint (▶ Fig. 4.9).

4.3.2 Sensory Innervation The median nerve carries cutaneous sensory information from the radial two-thirds of the palm and the volar surfaces of the first, second, third, and radial half of the fourth digits (▶ Fig. 4.10). Dorsal fingertip sensation is also carried by the median nerve, including the dorsum of the ulnar half of the distal phalanx of the thumb. Explore sensation over the thenar eminence to assess the palmar cutaneous branch, and sensation over the distal portion of the second and third digits to assess the sensory fibers that are carried by the median nerve through the carpal tunnel.

Fig. 4.9 Median nerve. The terminal group: first and second lumbricals.

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4.3.3 Martin-Gruber and Riche-Cannieu Anastomoses Anastomoses between the ulnar nerve and either the median nerve or its anterior interosseous branch may occur in the hand and in the forearm. Many variations are possible, and minor and major shifts in motor innervation of the hand may occur through these two potential routes of communication: the Martin-Gruber and Riche-Cannieu anastomoses. In up to 15% of limbs, a Martin-Gruber anastomosis is present that involves the median nerve–innervated thenar muscles (opponens pollicis, abductor pollicis brevis, and flexor pollicis brevis). With this variation, nerve fibers destined for these three muscles run down the anterior interosseous branch and are transferred to the ulnar nerve. Within the palm, these fibers are finally transferred back to the thenar motor branch, innervating their respective muscles. This distal communication between the deep ulnar branch and the thenar motor branch in the palm is termed the Riche-Cannieu anastomosis. Therefore, in patients with a low median nerve injury in the wrist or distal forearm in whom a Martin-Gruber anastomosis is present, thenar motor function can paradoxically be spared. In the same way in these patients, damage to the ulnar nerve near the wrist can cause more severe deficits in intrinsic hand function than typically expected. It is important to remember that, whenever strange deficit patterns are evident following a median or ulnar nerve injury, one should always consider these potential anastomoses.

Fig. 4.10 Median nerve. Sensory innervation.

Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

4.3.4 Clinical Findings The Upper Arm Severe injury to the median nerve in the upper arm affects the entire distribution of the nerve, with sensory loss and lost function in all of the muscles innervated. The branch to the pronator teres (the first muscle innervated by the median nerve) often arises above the elbow. Loss of pronator function suggests injury to the median nerve at or above the elbow. Involvement of the flexor carpi radialis also suggests median nerve injury at or above the elbow. When examining for complete median nerve palsy, the following pitfalls must be considered. The brachioradialis (innervated by the radial nerve), aided by gravity, may pronate the forearm from full supination. Next, you may observe thumb opposition via the indirect actions of the flexor pollicis brevis (its deep muscle head) and the adductor pollicis (both innervated by the ulnar nerve).

The Forearm Pronator Teres Syndrome and Sublimis Arch Syndrome The median nerve may be compressed or pinched where it passes between the two heads of the pronator teres. The only median-innervated muscle that is not affected by this syndrome is the pronator teres itself. This is because branches from the median nerve destined for this muscle originate proximal to where the median nerve passes underneath it. Median-innervated hand sensation is often normal; and motor function may be difficult to ascertain because of pain. Nonetheless, weakness is occasionally seen during flexion of the second and third digits. A fibrotic arch between the two heads of the flexor digitorum superficialis may also compress the median nerve as it passes underneath. This ridge has been called the sublimis arch. Clinical manifestations of this entrapment are quite similar to those of pronator teres syndrome, except that forceful flexion of the proximal interphalangeal joints of the second to fifth digits, which is mediated by contraction of the flexor digitorum superficialis muscle, may precipitate symptoms.

Anterior Interosseous Nerve Palsy An isolated palsy affecting the AIN may occur secondary to trauma, fractures, Parsonage–Turner syndrome, anomalous muscles and/or tendons, or without any known cause. Patients usually complain of weakness or clumsiness grasping objects with their first two digits. There are usually no complaints of pain; and, because this nerve contributes nothing to cutaneous sensation, no numbness occurs. There is weakness of the FDP (involving the second and third digits), flexor pollicis longus, and prona-

tor quadratus. This results in the inability to perform a pinch-type maneuver with the affected hand (patients have a positive “okay sign”). Weak forearm pronation will also frequently be present, but is difficult to demonstrate because the pronator teres remains functional. To confirm a pure AIN palsy, all other muscles innervated by the median nerve, as well as sensation, must be normal. Variations and incomplete syndromes are common. Consequently, many other etiologies may mimic this condition. AIN syndrome is a pure motor nerve palsy. Inability to perform a pinch maneuver should alert the physician to this diagnosis, as this is almost pathognomonic.

The Wrist: Carpal Tunnel Syndrome In cases of median nerve injury at the wrist, objective sensory testing over the thenar eminence should be normal, because sensation is transmitted via the palmar cutaneous branch, which does not pass through the carpal tunnel (▶ Fig. 4.5). However, the thenar muscular group (the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis) will be affected. Rarely, the thenar motor branch is affected selectively.

4.4 Ulnar Nerve As stated previously, the transformation of the medial and lateral cords into their terminal branches is Mshaped, lying over the anterior aspect of the axillary artery. The lateral leg of the letter M is the musculocutaneous nerve, while the medial leg is the ulnar nerve. The ulnar nerve is an extension of the medial cord of the brachial plexus (▶ Fig. 4.1). Until it reaches the forearm, the ulnar nerve gives off no branches to any muscle (▶ Fig. 4.11). Below the elbow, the first branches are destined for the flexor carpi ulnaris. Then, the ulnar nerve passes deep to the two proximal heads of the flexor carpi ulnaris, where it provides just a single major branch to the FDP (the ulnar portion of the FDP). Two sensory branches originate from the ulnar nerve in the distal half of the forearm—the dorsal ulnar cutaneous nerve and the palmar ulnar cutaneous nerve—which arise approximately 5 to 10 cm proximal to the wrist crease. In some cases, the dorsal ulnar cutaneous nerve may branch from the superficial sensory radial nerve. The ulnar nerve enters the hand via Guyon’s tunnel. Distally in Guyon’s tunnel, the nerve divides into a deep motor branch and a superficial sensory branch. From the deep branch of the ulnar nerve originates a small branch that innervates the hypothenar muscles. The deep (motor) branch supplies all the muscles innervated by the ulnar nerve in the hand. The superficial branch splits into digital nerves destined for the fourth and fifth digits. This mixed nerve supplies muscles of the forearm and hand and provides sensation over the fourth and fifth

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Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

Fig. 4.11 Anatomy of the ulnar nerve.

digits, as well as in the palm (ulnar side) and over the dorsal (ulnar side) surface of the hand.

The ulnar nerve innervates no muscles in the upper arm. The muscles innervated by the ulnar nerve may be grouped into: a forearm group (flexor carpi ulnaris, FDP); a hypothenar group (palmaris brevis, abductor digiti minimi, flexor digiti minimi, opponens digiti minimi); intrinsic muscles of the hand (the third and fourth lumbricals, and the palmar and dorsal interossei); and the thenar group (adductor pollicis, flexor pollicis brevis).

proximal to the wrist. Flexor carpi ulnaris contraction stabilizes the pisiform, so the abductor digiti minimi can abduct the fifth digit (▶ Fig. 4.12a). Then, instruct the patient to flex the wrist against resistance in an ulnar direction, which is the primary action of this muscle (▶ Fig. 4.12b). The FDP to the fourth and fifth digits is tested as its median-innervated half, focusing on the fifth digit. Immobilize the proximal interphalangeal joint while the patient flexes the distal interphalangeal joint (▶ Fig. 4.12c). Although the median nerve’s anterior interosseous branch may occasionally control distal interphalangeal joint flexion of the ring finger, the ulnar nerve always controls this movement in the fifth digit.

Forearm Group

Hypothenar Group

Testing the flexor carpi ulnaris is a two-step process. First, while the patient is abducting the fifth digit, observe and palpate the flexor carpi ulnaris tendon just

The palmaris brevis is located within the roof of Guyon’s tunnel. When it contracts, it corrugates the hypothenar skin. To test this muscle, have the patient forcibly abduct

4.4.1 Motor Innervation

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Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

Fig. 4.12 Ulnar nerve. Forearm group: (a,b) flexor carpi ulnaris, (c) flexor digitorum profundus.

Fig. 4.13 Ulnar nerve. Hypothenar group: (a) palmaris brevis, (b) abductor digiti minimi, (c) flexor digiti minimi, (d) opponens digiti minimi.

the fifth digit and “contract” the hypothenar eminence. Skin corrugation (wrinkling) should occur (▶ Fig. 4.13a). The abductor digiti minimi is tested by having the patient abduct his or her fifth digit against resistance (▶ Fig. 4.13b). Immobilizing the interphalangeal joints of the fifth digit and instructing the patient to flex the metacarpophalangeal joint against resistance assesses the flexor digiti minimi (▶ Fig. 4.13c). One cannot isolate this muscle’s function entirely, because flexion of the fifth digit’s metacarpophalangeal joint is also performed by the fourth lumbrical and the interossei.

The opponens digiti minimi is tested by the examiner trying to force the patient’s distal fifth metacarpal away from the thumb, while the patient holds the volar pads of the distal thumb and fifth digit together (▶ Fig. 4.13d).

Intrinsic Muscles of the Hand The hand’s intrinsic muscles can be organized into three groups: lumbricals, palmar interossei, and dorsal interossei. The lumbricals assist with flexing the metacarpophalangeal joints and extending the proximal interphalangeal

33

Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb joints when the metacarpophalangeal joints are immobilized in a hyperextended position. The dorsal interossei abduct or spread the fingers. Conversely, the palmar interossei adduct or close the fingers. The deep branch of the ulnar nerve innervates the third and fourth lumbricals (to the fourth and fifth digits), as well as all of the palmar and dorsal interossei muscles. To test the third and fourth lumbricals, immobilize the metacarpophalangeal joints of these two fingers in hyperextension, and then test extension of the proximal interphalangeal joints against resistance (▶ Fig. 4.14a). A simple way to test the palmar and dorsal interossei is by abducting the index finger against resistance (first dorsal interosseous) (▶ Fig. 4.14b) and adducting the index finger against resistance (second palmar interosseous) (▶ Fig. 4.14c).

Thenar Group The ulnar nerve innervates two muscles within the thenar eminence: the adductor pollicis and the deep head of the flexor pollicis brevis. The adductor pollicis can be tested by the examiner by trying to separate the thumb from the lateral border of the palm while having the patient adduct a straightened thumb (▶ Fig. 4.15a).

The deep head of the flexor pollicis brevis is innervated by the ulnar nerve. However, as stated previously, its superficial head is innervated by the median nerve. Testing this muscle is not very useful because of its dual innervation. However, some weakness relative to the other hand may occur with ulnar lesions. To test this muscle, have the patient flex the thumb’s metacarpophalangeal joint while the interphalangeal joint is maintained in extension to minimize compensatory action by the flexor pollicis longus (▶ Fig. 4.15b).

4.4.2 Sensory Innervation The ulnar nerve has three sensory branches, which together provide sensory innervation to the medial third of the hand (▶ Fig. 4.16). The dorsal ulnar cutaneous nerve innervates the dorsomedial third of the hand. It also innervates the dorsum of the fifth finger and the medial half of the fourth. However, the skin under and surrounding the fingernail is innervated by the superficial sensory division of the ulnar nerve. Sensory testing of the dorsal ulnar cutaneous nerve should take place on the dorsal surface of the medial third of the hand. The palmar ulnar cutaneous nerve provides sensory innervation to the whole medial third of the palm.

Fig. 4.14 Ulnar nerve. Hand intrinsic muscles: (a) third and fourth lumbricals, (b) first dorsal interosseous, (c) second palmar interosseous.

Fig. 4.15 Ulnar nerve. Thenar group: (a) adductor pollicis, (b) flexor pollicis brevis.

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Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

The Elbow

Fig. 4.16 Ulnar nerve. Sensory innervation.

However, because of variations in sensory territory, the best area to test this nerve’s function is over the hypothenar eminence. The superficial sensory division of the ulnar nerve carries sensation from the volar surface of the fifth finger and the medial half of the fourth, including the dorsal aspect of the distal phalanges (fingernails). The digital nerves carry sensation from the fingers to the superficial sensory division. The best area to test sensation for this nerve is over the volar surface of the fifth digit.

4.4.3 Clinical Findings The Upper Arm Injuries to the ulnar nerve in the upper arm can produce complete ulnar nerve palsy. This includes lost sensation over the hypothenar eminence (palmar ulnar cutaneous branch), the volar surface of the fifth and half of the fourth digit (superficial sensory division), and the dorsomedial third of the hand and fingers (dorsal ulnar cutaneous nerve). If sensory loss extends more than 2 cm proximal to the wrist crease, one should consider involvement of the medial antebrachial cutaneous nerve and therefore the medial cord of the brachial plexus (▶ Fig. 4.1). Wrist flexion in the ulnar direction will be absent. The distal phalanges of the fourth and especially the fifth digit will not flex secondary to FDP weakness. Marked intrinsic weakness of the hand can occur, with residual function provided by the thenar muscles innervated by the median nerve. There will be lost finger abduction and adduction from paralysis of the dorsal and palmar interossei, respectively. However, some finger abduction or adduction can still occur due to compensation by the long finger flexors and extensors. The so-called ulnar claw hand is characteristic of an ulnar nerve palsy.

Cubital tunnel syndrome is the second most frequent nerve entrapment in the body after carpal tunnel syndrome. This ulnar nerve entrapment is localized most frequently within the postcondylar groove. Even though branches to the flexor carpi ulnaris often originate from the ulnar nerve distal to the postcondylar groove (▶ Fig. 4.11), weakness of this muscle in cubital tunnel syndrome is rare. This has been attributed to the sensory and intrinsic hand muscle motor fibers in the ulnar nerve at the elbow being more superficial and, therefore, more prone to injury. If flexor carpi ulnaris weakness is present or occurs early, a lesion more proximal to the postcondylar groove should be considered. In other kinds of injury not associated with entrapment at the elbow, the flexor carpi ulnaris will always be affected, and the clinical findings can be the same as when the site of injury is located in the upper arm.

The Forearm Injuries in the forearm that occur distal to the elbow but proximal to the wrist present with normal function of the FDP and flexor carpi ulnaris muscles. Depending on the location of the injury along the course of the ulnar nerve, hand sensation can be more or less affected— for example, if the dorsal and palmar cutaneous nerves’ origins are proximal versus distal to the injury site. Where the ulnar sensory branches originate is most valuable in localizing ulnar nerve lesions. Sensory loss that includes the palmar or dorsal aspect of the hand implies that the lesion is proximal to Guyon’s tunnel (▶ Fig. 4.11). Distal to Guyon’s tunnel, the ulnar nerve divides into superficial and deep branches. The superficial (sensory) branch supplies skin over the hypothenar eminence, as well as sensation to the entire fifth (little) finger and the ulnar half of the fourth (ring) finger.

The Wrist Ulnar lesions in the wrist generally spare flexor carpi ulnaris and FDP function, and also spare sensation over the palm and dorsum of the hand. Ulnar nerve compression at the wrist (Guyon’s tunnel) is rare. Three variations in clinical presentation have been described (purely motor, purely sensory, or mixed), because compression can occur within three zones: ● Zone 1: With compression of the ulnar nerve before it divides within Guyon’s tunnel, sensory loss occurs over the volar surfaces of the fifth and medial half of the fourth finger, including the nail beds (superficial sensory division). Sensation to the hypothenar eminence is commonly spared because the palmar ulnar cutaneous nerve is unaffected. Patients can have intrinsic hand

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Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

●

●

muscle weakness, including a claw hand, a Wartenberg sign, and a Froment paper sign. Zone 2: When compression only affects the deep motor branch, no cutaneous sensory loss is evident. However, the motor deficits seen are similar to those of a zone 1 lesion. To confirm that the superficial sensory division is spared, one can test for palmaris brevis contraction. The superficial sensory division innervates this small muscle; therefore, if this muscle contracts, one knows that this division is at least partially functional. Zone 3: When compression only affects the superficial sensory division, the best area to test for sensory loss is over the volar surface of the fifth digit. Motor function is normal.

Remember that the intrinsic muscles of the hand may be intact in some patients with a Martin-Gruber or RicheCannieu anastomosis.

4.5 Radial Nerve Distal to the origins of the thoracodorsal and axillary nerve branches, the posterior cord of the brachial plexus becomes the radial nerve (▶ Fig. 4.1). The radial nerve in the arm courses around the humerus and pierces the lateral intermuscular septum. In the lateral arm, it lies between the brachialis and brachioradialis muscles and enters the antecubital fossa under the cover of the brachioradialis, the extensor carpi radialis longus, and the extensor carpi radialis brevis, which sequentially arcade over the nerve. This arcade of muscles is referred to as the radial tunnel. Distal to the elbow joint, the radial nerve bifurcates into the posterior interosseous and superficial sensory

radial nerves (▶ Fig. 4.17). The location of this bifurcation is variable. The radial nerve provides motor innervation to the brachioradialis and extensor carpi radialis longus 2 to 3 cm proximal to the elbow. The branch to the extensor carpi radialis brevis originates from the radial nerve near its bifurcation. The superficial head of the supinator muscle forms a pocket into which the posterior interosseous nerve (PIN) descends. The edge of this pocket can be fibrous and is termed the arcade of Fröhse. The superficial sensory radial nerve remains superficial to both heads of the supinator. The PIN is a pure motor nerve. It enters the supinator pocket deep to the arcade of Fröhse. Once between the two heads of the supinator muscle, the PIN travels laterally, entering the extensor compartment of the forearm. After emerging from between the two heads of the supinator muscle in the extensor compartment of the forearm, it then ramifies into a large number of branches, which are often called the cauda equina of the forearm, which run sequentially over the abductor pollicis longus, the extensor pollicis longus, and the extensor pollicis brevis (the three thumb muscles that are innervated by the radial nerve). The superficial sensory branch continues under the brachioradialis muscle until approximately two-thirds of the way down the forearm. In the lower third of the forearm, it becomes superficial and branches toward the dorsolateral aspect of the hand.

4.5.1 Motor Innervation The radial nerve innervates four muscle groups: the triceps group (triceps muscle, three heads), the lateral epicondyle group (brachioradialis, extensor carpi radialis

Fig. 4.17 Anatomy of the radial nerve.

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Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb longus and brevis, and supinator muscle), the PINsuperficial group (extensor carpi ulnaris, extensor digitorum communis, and extensor digiti minimi), and the PIN-deep group (abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis, and extensor indicis).

Triceps Group The triceps has three heads (long, medial, and lateral), which act together to extend the forearm. To test the tri-

Fig. 4.18 Radial nerve. Triceps muscle examination.

ceps muscle, support the limb with the elbow halfextended and instruct the patient to extend the elbow against resistance (▶ Fig. 4.18).

Lateral Epicondyle Group Branches to the brachioradialis muscle originate proximal to the lateral epicondyle. To test this muscle, have the patient flex the elbow against resistance with the forearm halfway between pronation and supination (▶ Fig. 4.19a). With contraction, the brachioradialis muscle becomes prominent and can be both observed and palpated. The extensor carpi radialis longus and brevis are tested together by having the patient extend and abduct the wrist against resistance while you stabilize the distal forearm (▶ Fig. 4.19b). With the forearm pronated, these muscles can be seen lateral to the brachioradialis. Most branches to the extensor carpi radialis longus originate from the radial nerve above the lateral epicondyle, whereas branches to the extensor carpi radialis brevis usually arise below the lateral epicondyle. In the proximal forearm, the PIN innervates the supinator before it passes under the arcade of Fröhse. The supinator muscle supinates the forearm. Although the biceps muscle is also a strong forearm supinator, it can be placed at a mechanical disadvantage by extending the elbow. Therefore, to isolate supinator function, it should be tested with the elbow extended (▶ Fig. 4.19c).

Fig. 4.19 Radial nerve. Lateral epicondyle group: (a) brachioradialis muscle, (b) extensor carpi radialis longus and brevis, (c) supinator.

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Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

Posterior Interosseous Nerve—Superficial Group

digit (▶ Fig. 4.20c). This digit is usually quite weak and should be compared against the normal hand.

After passing through the supinator and entering the extensor compartment, the PIN supplies the superficial group of extensor muscles, often through a common branch. This group includes the extensor carpi ulnaris, the extensor digitorum communis, and the extensor digiti minimi. Test the extensor carpi ulnaris by stabilizing the distal forearm and having the patient extend and adduct the wrist, bent in an ulnar direction (▶ Fig. 4.20a). This muscle’s tendon can be observed and palpated at the wrist. The extensor digitorum communis extends the second to fifth digits at the metacarpophalangeal joints. To evaluate this muscle, have the patient extend each finger at the knuckle joint while you apply resistance just proximal to the proximal interphalangeal joint (▶ Fig. 4.20b). The patient should not be allowed to simultaneously flex the wrist because this will extend the fingers secondary to a tenodesis effect. The second and fifth digits have supplementary extensors: the extensor indicis and digiti minimi. The extensor digiti minimi acts in a similar fashion to the extensor digitorum communis, but only upon the fifth

Posterior Interosseous Nerve—Superficial Group The deep group of muscles is usually innervated by two separate branches from the PIN. This group includes muscles that act upon the thumb and index finger: the abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis, and extensor indicis. They are the most distal, radial nerve–innervated muscles. The abductor pollicis longus abducts the thumb in a radial direction (remember that the abductor pollicis brevis is responsible for palmar abduction of the thumb). To test the abductor pollicis longus, the patient should maintain an extended thumb away from the index finger in the plane of the palm (▶ Fig. 4.21a). Thumb extension can be tested with the hand in a fist, resting with its ulnar surface on some flat surface (like a table or the patient’s thigh). The thumb is actively extended away from the other fingers. The extensor pollicis longus extends the interphalangeal joint (▶ Fig. 4.21b), while the extensor pollicis brevis extends the metacarpophalangeal joint (▶ Fig. 4.21c).

Fig. 4.20 Radial nerve. Posterior interosseous nerve—superficial group: (a) extensor carpi ulnaris, (b) extensor digitorum communis, (c) extensor digiti minimi.

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Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

Fig. 4.21 Radial nerve. Posterior interosseous nerve—superficial group: (a) abductor pollicis longus, (b) extensor pollicis longus, (c) extensor pollicis brevis.

The extensor indicis acts only upon the index finger and is examined like the extensor digitorum communis, as described earlier. Rarely, the PIN can communicate with the deep motor branch of the ulnar nerve and control the first dorsal interossei muscles. This anomalous communication is called the Froment–Rauber nerve.

4.5.2 Sensory Innervation Deficits involving the radial nerve’s sensory branches can help localize the level of injury (▶ Fig. 4.22).

Posterior Cutaneous Nerve to the Arm The posterior cutaneous nerve to the arm is the first sensory branch of the radial nerve. It originates in the axilla. Sensory loss in this territory is indicative of a radial nerve lesion proximal to the spiral groove.

Lower Lateral Cutaneous Nerve to the Arm The lower lateral cutaneous nerve to the arm originates from the radial nerve in the spiral groove. The sensory territory of this branch includes the lower lateral arm below the deltoid. Sensory loss here, with preserved posterior arm sensation (via the posterior cutaneous nerve to Fig. 4.22 Radial nerve. Sensory innervation.

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Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb the arm), may indicate injury of the radial nerve within the spiral groove.

Posterior Cutaneous Nerve to the Forearm The posterior cutaneous nerve to the forearm originates at the brachial-axillary angle, proximal to the origin of the lower lateral cutaneous nerve to the arm. The posterior cutaneous nerve to the forearm runs with the radial nerve in the spiral groove, and pierces the brachial fascia with the lower lateral cutaneous nerve to the arm near the lateral intermuscular septum. Then it passes posterior to the lateral epicondyle and lateral to the olecranon. Its sensory territory includes the dorsolateral aspect of the forearm.

Superficial Sensory Radial Nerve The superficial sensory radial nerve provides sensation to the dorsolateral half of the hand, as well as the proximal two-thirds of the second, third, and lateral half of the fourth digits. The more lateral portion of the thumb is also part of the sensitive territory of this nerve. It is not clear which area is the most specific for testing a lesion affecting this nerve; areas that have been proposed include the anatomical snuff box, the first dorsal web space, and the area over the distal half of the second metacarpal bone (▶ Fig. 4.23). However, variations in and overlap between sensory territories are frequent with the superficial sensory radial nerve, the dorsal ulnar cutaneous nerve, and the lateral antebrachial cutaneous nerve.

4.5.3 Clinical Findings The Arm Triceps palsy is rare in radial nerve injuries in the arm, because branches to these muscles originate high in the

Fig. 4.23 Sensory innervations in the hand.

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axilla. When a high radial palsy in the axilla occurs, it can cause both triceps weakness and posterior arm sensory loss (from injury to the posterior cutaneous nerve to the arm), two deficits that distinguish this location from more common radial nerve injuries occurring at the spiral groove. Injuries affecting the proximal radial nerve in the axilla may be differentiated from posterior cord involvement by confirming normal deltoid and latissimus dorsi strength (innervated by the axillary and thoracodorsal branches of the posterior cord, respectively). Patients with C7 palsies can be distinguished from posterior cord or radial nerve injuries because they usually have numbness on both the volar and dorsal surfaces of the third digit. Furthermore, C7 muscles innervated by the median nerve (i.e., pronator teres and flexor carpi radialis longus) would also be weak. Consequently, the hallmark of a radial nerve injury in the axilla is triceps weakness, whereas radial nerve injuries in the arm from the spiral groove through the distal humerus and elbow spare the triceps muscle, but lead to weakness involving the remaining muscles, including the brachioradialis. Due to brachioradialis palsy, elbow flexion may be a bit weak relative to the normal side. There is wrist drop from extensor carpi radialis (longus and brevis) and extensor carpi ulnaris weakness. The fingers cannot extend at the metacarpophalangeal joint. Supination is somewhat weak, with residual supination performed by the biceps brachii. The wrist and hand appear flaccid, with the fingers semiflexed and the metacarpal bone of the thumb ventral to the palm (▶ Fig. 4.24). Sensory loss differentiates injury in the spiral groove from injury at the distal humerus. Loss of sensation along the lower lateral arm and posterior forearm usually occurs with spiral groove radial nerve injuries, due to associated injury of the lower lateral cutaneous nerve to the arm and posterior cutaneous nerve to the forearm.

Fig. 4.24 Wrist drop sign.

Manual of Peripheral Nerve Surgery | 25.07.17 - 10:00

Clinical Aspects of Peripheral Nerve Lesions in the Upper Limb

The Forearm The hallmark of injury to the radial nerve in the forearm is normal strength of the brachioradialis muscle. In the proximal forearm, the radial nerve divides into the superficial sensory radial nerve and the PIN. Injuries of the PIN cause a purely motor neuropathy; since this nerve carries no cutaneous sensory fibers, sensation remains normal. PIN palsy has two characteristics: wrist extension weakness in an ulnar direction (radial wrist extension remains normal, mediated by the extensor carpi radialis longus and brevis that are innervated more proximally by the radial nerve) and finger extension weakness at the metacarpophalangeal joints. Of note is that these patients do not present with a wrist drop because the extensor carpi radialis muscles are unaffected. Supinator and extensor carpi radialis brevis weakness may occur from PIN palsy if the injury is proximal to the arcade of Fröhse. As such, weakness of the supinator is classically not evident in supinator syndrome because

most of the branches to this muscle originate from the PIN proximal to where this nerve passes under the arcade of Fröhse. In summary, isolated PIN palsy is confirmed by documenting normal brachioradialis and superficial sensory radial nerve function. Isolated damage to the superficial sensory radial nerve can also occur in the forearm, resulting in hypoesthesia or anesthesia in its territory, but no motor deficits.

Further Readings Birch R. Surgical Disorders of the Peripheral Nerves. 2nd ed. London: Springer-Verlag; 2011 Midha R, Zager EL. Surgery of Peripheral Nerves: A Case-Based Approach. New York, NY: Thieme Medical Publishers, Inc.; 2008 Russell SM. Examination of Peripheral Nerve Injuries. An Anatomical Approach. 2nd ed. New York, NY: Thieme Medical Publishers Inc.; 2015 Slutsky DJ, Hentz VR. Peripheral Nerve Surgery: Practical Applications in the Upper Arm. London: Churchill Livingstone, Elsevier Inc.; 2006

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Clinical Aspects of Traumatic Peripheral Nerve Lesions in the Lower Limb

5 Clinical Aspects of Traumatic Peripheral Nerve Lesions in the Lower Limb Yuval Shapira and Shimon Rochkind Abstract Knowledge of neuroanatomy and the clinical exam is of paramount importance for accurate diagnosis and optimal management of nerve injuries in the lower extremity. When evaluating patients with peripheral nerve lesions in the lower limb, it is important to exclude differential diagnosis. In cases where the injured nerves do not recover spontaneously, the surgeon has several treatment modalities. Selecting the correct treatment depends on the diagnosis and other specific factors such as the level of injury, the current neurological status, the existence of neuropathic pain, the time since the injury, and other specific factors related to the expected recovery. Keywords: lumbosacral plexus, sciatic nerve, peroneal nerve, tibial nerve, obturator nerve, femoral nerve, saphenous nerve

5.1 Introduction When evaluating patients with peripheral nerve lesions in the lower limb, it is important to exclude spinal lumbar radiculopathy and nonstructural neuropathies.1,2,3,4,5,6,7 Generally, femoral neuropathy should be differentiated from L2–L4 radiculopathy. L5 radiculopathy should be excluded in patients presenting with symptoms related to peroneal neuropathy, whereas S1 radiculopathy should be excluded from symptoms related to tibial neuropathy. Other nonsurgical processes such as lumbosacral plexitis (amyotrophic neuralgia), proximal diabetic neuropathy, and neoplastic and postradiation neuropathy should also be considered. The diagnosis and management are based on the clinical history and physical examination together with imaging studies and electrodiagnostic findings. The extent of injury and distance to the target, together with the interval of time since the injury, are the most important prognostic factors for recovery. Here, we briefly describe applicable neuroanatomy and clinical aspects to support the management and surgical treatment of peripheral nerve lesions in the lower limb.

5.2 Lumbosacral Plexus All motor and sensory innervation of the lower limbs originate from the lumbar and sacral nerve roots, which together form the lumbosacral plexus. Anatomy of the lumbar and sacral plexus and corresponding nerves are presented in ▶ Fig. 5.1, ▶ Tables 5.1 and ▶ 5.2.

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The lumbar plexus originates from the ventral rami of spinal nerve roots T12–L4 deep to the psoas muscle emerging through and lateral to the border of the muscle. Major components of the lumbar plexus include iliohypogastric, ilioinguinal, genitofemoral, and lateral femoral cutaneous nerves together with the femoral nerve and the obturator nerve. The anterior division of L4 joins the ventral rami of L5 to form the lumbosacral trunk, which contributes to the sacral plexus. The sacral plexus comprises spinal nerve root segments (L4–S3) and lies deep within the pelvis. The anterior divisions of L4–S3 join to form the tibial nerve, whereas posterior divisions of L4– S2 comprise the common peroneal nerve. The tibial and peroneal nerve merge in a common epineural sheath to form the sciatic nerve, as it exits the pelvis via the greater sciatic foramen inferior to the pyriformis muscle together with the posterior cutaneous nerve to the thigh, the inferior gluteal nerve, and the pudendal nerve most medially. Less common, the sciatic nerve passes through or even superior to the piriformis muscle. Injury to the lumbosacral plexus may occur following high-energy trauma (e.g., motor vehicle accident or high fall), gunshot wound, or as a complication of spine or orthopaedic surgery.3

5.3 Sciatic, Tibial, and Peroneal Nerve 5.3.1 Anatomy The sciatic nerve is the main output from the lumbosacral plexus and originates from nerve roots L4–S3 after receiving a contribution from the lumbar plexus through the lumbosacral trunk. The sciatic nerve exits the pelvic at the sciatic notch together with the posterior cutaneous nerve via the greater sciatic foramen, deep to the gluteus magnus muscle and inferior to the piriformis muscle. The sciatic nerve continues along the posterior aspect of the thigh as two branches, tibial (medial aspect) and peroneal (lateral aspect), joined by a common epineurium up to the sciatic bifurcation at the lower third of the thigh just superior to the popliteal fossa. The tibial nerve originates from the ventral rami of the anterior divisions of L4–S3. The posterior divisions of L4–S2 supply the common peroneal nerve. The tibial nerve runs along the medial aspect and the peroneal nerve runs along the lateral aspect of the sciatic nerve and they both innervate muscles as described in ▶ Table 5.2.

Clinical Aspects of Traumatic Peripheral Nerve Lesions in the Lower Limb T12

L1

(T12—L1)

lliohypogastric n. llioinguinal n.

Fig. 5.1 Lumbosacral plexus illustration depicting the major components of the lumbosacral plexus with its spinal nerve root segments. Note relationship of the lumbar and sacral plexus through the lumbosacral trunk.

L2

(L1) L3

Lumbar plexus

Genitofemoral n.

(L1—L2) L4

Lateral femoral cutaneous n.

(L2—L3) L5

Femoral n. Obturator n.

Lumbosacral trunk

(L2—L4) (L2—L4) S1

Superior gluteal n. Inferior gluteal n. Common fibular n. Sacral plexus

Tibial n. Sciatic n. Posterior femoral cutaneous n. Pudendal n.

(L4—S4) (L5—S2) (L4—S2)

S2 S3 S4

(L4—S3) (L4—S3) (S4—S3)

(S2—S4)

5.3.2 Injuries Nerve Lesions due to Open Injuries Partial or complete loss of function in the distribution of the sciatic nerve or one of its divisions, following a deep penetrating wound from a sharp object, suggests a high probability of a partially or completely severed nerve. The nerve is injured as a result of a direct hit or, more importantly, by the destructive forces created by the passage of a high-velocity missile through the limb though it misses the nerve, subjects it to tremendous deforming forces leading to extensive stretch lesions over a considerable length of the nerve. Shrapnel injury has been shown to be more destructive for nerve tissue than gunshot injuries.8

second-degree damage from which it will recover spontaneously and completely. However, the nerve might be subjected to such abrupt and violent deformation that extensive third- and fourth-degree damage involves considerable lengths of the nerve. In particularly severe injuries, the nerve may be ruptured. Other serious closed lesions are those in which the common peroneal nerve is subjected to prolonged unrelieved compression at the head or neck of the fibula. This leads to irreversible changes in the nerve in the form of a destructive fibrosis, which blocks all attempts of spontaneous regeneration. The prognosis in these cases is poor.

Stretch Injuries Nerve Lesions due to Closed Injuries In general, closed injuries are traction or compression lesions. With mild trauma, the nerve sustains first- or

The most serious nerve lesions are those due to traction, mostly occurring when the nerve is violently displaced in severe injuries to the limb.

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Clinical Aspects of Traumatic Peripheral Nerve Lesions in the Lower Limb Table 5.1 Nerves of the lumbar plexus Nerve (spinal root)

Muscle innervation

Sensory branch

Iliohypogastric (T12–L1)

Internal and transverse abdominal

Lateral cutaneous (iliac) Anterior cutaneous (hypogastric)

Ilioinguinal (L1)

Internal oblique

Anterior scrotal/labial

Cremaster (male)

Femoral Genital

Lateral femoral cutaneous (L2–L3)

–

LFCN

Femoral (L2–L4)

Iliopsoas Pectineus Sartorius Quadriceps femoris (RF, VL, VM, VI)

Anterior cutaneous Saphenous

Obturator (L2–L4)

External obturator Adductor (longus, brevis, magnus) Gracilis

Medial cutaneous

Accessory obturator (30%)

Pectineus

–

Genitofemoral (L1–L2)

Abbreviations: LFCN, lateral femoral cutaneous nerve; RF, rectus femoris; VI, vastus intermedius; VL, vastus lateralis; VM, vastus medialis.

Table 5.2 Nerves of the sacral plexus Nerve (spinal root)

Muscle innervation

Sensory branch

Superior gluteal (L4–S1)

Gluteus medius Gluteus minimus Tensor fasciae latae

–

Inferior gluteal (L5–S2)

Gluteus maximus

–

Common peroneal (L4–S2)

Biceps femoris SH Tibialis anterior (DPN) EDL and EDB (DPN) EHL and EHB (DPN) PT (DPN) Peroneus longus (SPN) Peroneus brevis (SPN)

Lateral sural cutaneous Lateral dorsal cutaneous (DPN) Intermediate dorsal cutaneous (DPN) Medial dorsal cutaneous (SPN)

Tibial (L4–S3)

Semitendinosus Semimembranosus Biceps femoris LH Adductor magnus Gastrocnemius Popliteus Soleus Plantaris Tibialis posterior FDL and FHL Abductor hallucis (MP) FDB and FHB (MP) Lumbricals (MP) Quadratus plantae (LP) FDM (LP) Adductor hallucis (LP) Interossei and lumbricals (LP) ADM foot (LP)

Medial sural cutaneous Calcaneal Medial plantar Lateral plantar

Posterior femoral cutaneous (S1–S3)

–

Inferior cluneal Perineal branch

Abbreviations: ADM, abductor digiti minimi of foot; DPN, deep peroneal nerve; FDL and FDB, flexor digitorum longus and brevis; FHL and FHB, flexor hallucis longus and brevis; LH, long head; SH, short head; SPN, superficial peroneal nerve.

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Clinical Aspects of Traumatic Peripheral Nerve Lesions in the Lower Limb

Obstetrical and Birth Injuries These are nerve lesions in the mother and infant caused by trauma during obstetrical delivery. The lumbosacral trunk in the mother may be injured where it crosses the pelvic rim during the application of forceps in a difficult delivery. Pressure inadvertently applied to the lateral aspect of the knee during delivery may result in a compression lesion of the common peroneal nerve. More common are the stretch lesions of the sciatic and peroneal nerves, which result from traction on the limb of forcible intrauterine manipulations to assist delivery.

5.3.3 Common Sites and Types of Nerve Lesions The Pelvis: Sacral Plexus Compression and Traction Lesions Sciatic nerve lesions associated with pelvic fractures are severe injuries which involve the sacroiliac joint and fracture of the bones constituting the posterior and posterolateral walls of the pelvis cavity. These are traction and/or compression nerve lesions involving one or a combination of the lumbosacral trunk and the sciatic nerve itself.

The Gluteal Region The sciatic nerve is at risk in the gluteal region because the buttock is a common site for therapeutic injections. Besides, the nerve is intimately related to the hip joint and it may be involved in orthopaedic injuries affecting that joint.

Injection Injury They are lesions caused by the injection of sclerosing and toxic agents in or around the sciatic nerve. The nerve may be damaged by the needle, by the agent used, by pressure from a hematoma, or later by the scarring which follows tissue reaction to the external material. Sciatic nerve injury originating in this way has been reported after intragluteal injections in premature infants, children, and adults. Pain during or immediately following the injection is both severe and generalized, though it may be confined to the sciatic field. Signs and symptoms are maximal in the common peroneal nerve distribution with a foot drop and varying degrees of sensory loss along the outer line of the leg and dorsum of the foot. With more severe and extensive damage, all movements below the knee are grossly affected or lost.

the sciatic nerve, which may also be injured during attempts to reduce the dislocation. Damage to the sciatic nerve can occur during operations on the hip joint and femur.

The Popliteal Fossa and Knee Joint Considering the two terminal divisions of the sciatic nerve, the tibial is more deeply placed and better protected in the popliteal fossa. The common peroneal nerve is intimately related to the knee joint. In this position, the nerve may be stretched, torn, or ruptured in traumatic dislocations of the joint.

The Head and Neck of the Fibula The common peroneal nerve is closely related to the superior tibiofibular joint and to the head and neck of the fibula. The nerve may be damaged in several ways, including the following: ● Fractures of the neck of the fibula. ● Blows on the lateral side of the knee. ● Superficial lacerations affecting the upper end of the fibula. ● Posterior dislocation of the tibiofibular joint. ● The stretched nerve may be damaged by being forcibly angulated around the head of fibula. ● Pressure from an improperly applied plaster, leg braces, or thigh bondage.

5.3.4 Symptoms and Signs of Common Peroneal Nerve Injury Symptoms and signs of common peroneal nerve involvement include the following: ● Paresthesia and pain down the outer aspect of the leg and dorsum of the foot and ultimately hypoesthesia in the cutaneous distribution of the superficial and deep peroneal nerves. ● In common peroneal lesions, cutaneous sensation is defective over the outer aspect of the leg and the dorsum of the foot. ● Tenderness to deep pressure over the neck of the fibula. ● Progressive weakness of the peronei and tibialis anterior muscles in particular, which may proceed to a foot drop.

The Motor Disability ●

●

Injuries about the Hip Joint Injuries fracturing the acetabulum and/or dislocating the head of the femur posteriorly may result in damage to

●

Eversion of the foot. The peronei can be seen and felt to contract when the foot is everted against resistance. Dorsiflexion of the foot. A paralyzed tibialis anterior is too weak to dorsiflex the foot against gravity. Extension of the toes. Deceptive extension of the toes is observed in complete lesions of the common peroneal nerve.

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Clinical Aspects of Traumatic Peripheral Nerve Lesions in the Lower Limb

5.3.5 Symptoms and Signs of Tibial Nerve Injury ●

●

●

●

●

Plantar flexion of the foot resulting in paralysis of gastrocnemius and soleus muscles. Plantar flexion of the foot should be tested with gravity eliminated and against resistance. Inversion of the foot in plantar flexion, a movement which is performed by the tibialis posterior muscle. Flexion in the toes. In complete lesions of the tibial nerve, the toe may be feebly plantar flexed. Intrinsic muscles of the foot. Paralysis of the intrinsic muscles is revealed by a claw deformity. Abnormal sensation in the tibial aspect of the leg and inner aspect of the foot. The most serious sensory loss involves the sole, the main weight-bearing area.

longus muscle medially.5 The femoral nerve splits into an anterior and posterior branch distal to the femoral triangle. The cutaneous branches include intermediate femoral cutaneous, medial femoral cutaneous, and the saphenous nerves. The saphenous nerve runs distally with the femoral vessels parallel to the sartorius muscle to provide sensory coverage to the medial leg, medial malleolus, and arch of the foot. The lateral femoral cutaneous nerve is a separate branch coming off directly from the lumbar plexus. The femoral nerve gives motor innervation to the quadriceps (rectus femoris, vastus lateralis, vastus intermedius, and vastus medialis), sartorius, and pectineus muscles.

5.5.2 Femoral Nerve Lesions Open Injuries

5.4 Obturator Nerve 5.4.1 Anatomy The obturator nerve originates from the lumbar plexus, arising from the anterior divisions of L2–L4 ventral rami. The nerve runs posterior to the psoas major muscle along its medial border and exits the pelvis through the obturator foramen in the obturator canal. The obturator nerve gives motor innervation to the adductor muscles of the lower extremity (obturator externus, adductor longus, adductor brevis, adductor magnus, gracilis) and the pectineus (only in 30% by the accessory obturator nerve). The obturator nerve gives sensory innervation to the medial aspect of the thigh.

5.4.2 Injuries Lesions of the obturator nerve are uncommon. The nerve may be damaged in this region during total hip arthroplasty. The lesion is caused by pressure exerted by the cementing material. Obturator nerve lesions may also occur as a result of a pelvic fracture.

The nerve may be damaged in penetrating injuries such as in gunshots and other missile wounds, stab wounds, and by penetrating fragments of glass and other sharp objects. In lesions of the nerve immediately below the inguinal ligament, the iliacus and psoas muscles are not affected, but all other muscular and cutaneous branches are involved. Penetrating injuries involving the midthigh and the adductor canal may involve the saphenous nerve and the branch to the vastus medialis.

Closed Injury as a Result of External Trauma A femoral nerve palsy may follow a severe fall, usually on the side or back, or an injury received in a road accident or sporting activity. Nerve damage is due to: ● Rupture of the iliacus or iliopsoas muscles with hemorrhage into the iliacus compartment producing pressure over the nerve. ● Acute stretching of the nerve due to forced extension of the limb. ● A fractured pubis.

5.5.3 Saphenous Nerve Lesions

5.5 Femoral Nerve 5.5.1 Anatomy The femoral nerve is the largest branch of the lumbar plexus. It originates from the posterior divisions of L2–L4 ventral rami (▶ Fig. 5.1, ▶ Table 5.1) posterior to the psoas major muscle. The nerve runs inferiorly and laterally under the pelvis major and passes over the iliacus muscle in the pelvic.4 The nerve enters the anterior thigh at the femoral triangle lateral to the femoral artery, outside the femoral sheath and deep to the iliacus fascia, where it is bordered by the inguinal ligament superiorly, the sartorius muscle laterally and inferiorly, and the adductor

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Lacerations and surgical incisions involving the medial aspect of the knee may divide branches of the saphenous nerve given off where the nerve becomes cutaneous. The largest and most important of these branches is the infrapatellar. Transection of these nerves can result in the formation of a painful neuroma, which in this region can be very troublesome and disabling.

5.5.4 The Symptoms and Signs of Femoral Nerve Involvement Atrophy of the quadriceps muscle mass gives an obvious wasted appearance to the anterior part of the thigh.

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Clinical Aspects of Traumatic Peripheral Nerve Lesions in the Lower Limb

The Motor Disability ●

●

●

Paresis or paralysis of the iliopsoas and rectus femoris is reflected in weakness in flexion of the thigh. Paresis or paralysis of the quadriceps muscle results in weakness or an inability to extend the leg. The limb is unstable. Walking and many other activities and movements involving strong extension at the knee are severely disabled. Quadriceps function is readily tested by asking the patient to extend the leg against gravity or resistance, or holding the leg in an extended position against resistance.

Sensation Paresthesia or a deepening numbness affecting the anterior and medial aspect of the thigh and extending down the inner side of the leg and foot to the big toe.

5.6 Conclusion Anatomical knowledge and understanding the pathophysiological process, depending on the nature of injury, is

vital for tailoring the optimal treatment plan and achieving the best possible functional outcome in lower limb peripheral nerve injuries. In cases where the injured nerves are not able to recover spontaneously, surgical approach allow for potential recovery.

References [1] Wilbourn AJ. Plexopathies. Neurol Clin. 2007; 25(1):139–171 [2] Planner AC, Donaghy M, Moore NR. Causes of lumbosacral plexopathy. Clin Radiol. 2006; 61(12):987–995 [3] Kutsy RL, Robinson LR, Routt ML, Jr. Lumbosacral plexopathy in pelvic trauma. Muscle Nerve. 2000; 23(11):1757–1760 [4] Reinpold W, Schroeder AD, Schroeder M, Berger C, Rohr M, Wehrenberg U. Retroperitoneal anatomy of the iliohypogastric, ilioinguinal, genitofemoral, and lateral femoral cutaneous nerve: consequences for prevention and treatment of chronic inguinodynia. Hernia. 2015; 19(4):539–548 [5] Choy KW, Kogilavani S, Norshalizah M, et al. Topographical anatomy of the profunda femoris artery and the femoral nerve: normal and abnormal relationships. Clin Ter. 2013; 164(1):17–19 [6] Mackinnon SE, ed. Nerve Surgery. New York, NY: Thieme; 2015 [7] Sunderland S, ed. Nerves and Nerve Injuries. 2nd ed. Edinburgh: Churchill Livingstone; 1978 [8] Rochkind S, Strauss I, Shlitner Z, Alon M, Reider E, Graif M. Clinical aspects of ballistic peripheral nerve injury: shrapnel versus gunshot. Acta Neurochir (Wien). 2014; 156(8):1567–1575

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Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations

6 Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations Carlos Alberto Rodríguez Aceves, Miguel Domínguez Páez, and Victoria E. Fernández Sánchez Abstract Electrodiagnostic studies are considered an extension of the clinical examination for peripheral nervous system diseases and injuries. They started to be included as a part of the diagnostic protocol for nerve injuries after the Second World War. Since then, they have been used routinely to evaluate damaged peripheral nerve function, regardless of etiology (e.g., trauma, chronic compression, tumors, neuropathies, etc.). Currently, electrodiagnostic studies are a very useful tool for peripheral nerve surgery during pre- and intraoperative evaluations and postoperative follow-up. For this purpose, all professionals involved (neurophysiologists, anesthesiologists, neurosurgeons, and rehabilitation specialists) should be part of a multidisciplinary team and maintain continuous communication. Different techniques are available to assess nerves’ functional status, including: sensory and motor nerve conduction studies; electroneurography; electromyography; somatosensory and motor evoked potentials; and nerve action potentials with direct stimulation of the nerve trunk. This chapter will examine general aspects of nerve impulse conduction, current recording techniques and their utility, clinical correlations, and the perioperative use of these techniques for peripheral nerve surgery. Keywords: electrodiagnostic studies, peripheral nerve surgery, nerve injury, nerve conduction studies, electroneurography, electromyography, somatosensory evoked potentials, motor evoked potentials, neuroma-incontinuity, nerve action potential, multimodal intraoperative monitoring

6.1 Basic Considerations 6.1.1 Anatomical Characteristics Axons are extensions of neuronal cell bodies. They transmit nerve impulses and are enveloped by myelin. Myelin is produced by Schwann’s cells (SCs) in the peripheral nervous system (PNS); its function is to isolate axons from each other and optimize the transmission of nerve impulses through periodic gaps called nodes of Ranvier. Individual axons are surrounded by connective tissue called the endoneurium. Axons are bundled together in groups called fascicles, each one covered by a connective tissue sheath known as the perineurium. Fascicles are grouped together in bundles that together constitute a nerve trunk, which also is surrounded by epineurium.

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Understanding this structure allows one to appreciate the pathophysiological substrate of nerve injuries, the degeneration/regeneration process, and the degree of injury.1,2,3,4 In the PNS, effector information is transmitted through motor units (MUs), each of which is composed of an alpha motor neuron, its axon, and whatever number of extrafusal muscle fibers it innervates. Afferent information is integrated through sensory receptors; its axons and cell bodies are located in the dorsal root ganglia.5

6.1.2 Physiological Characteristics At rest, nerve fibers maintain their resting membrane potential. Generation of a stimulus of supramaximal intensity results in changes in ion flow from the exterior to the interior of the axon. This increases positivity within the interior of the nerve fiber, decreasing the potential difference between the inside and outside to transmit the impulse that generates an action potential (AP).5 Electrodiagnostic studies (EDSs) evaluate the impulse conduction of thicker and more myelinated nerve fibers (i.e., the most rapid ones), which are classified as type A fibers, as per Erlanger and Gasser.6,7

6.2 Pathophysiology Two pathophysiological processes—axonal damage and demyelination—occur individually or concurrently in a damaged nerve that are independent of the etiology and mechanism of injury.

6.2.1 Axonal Damage Any injury that causes disruption in an axon’s integrity results in degeneration of the distal segments through a process called Wallerian degeneration (WD), which is completed within 3 weeks of an injury. This degeneration process can also occur in the cell body (chromatolysis), proximal axon, and distal target organs. Its broad etiology includes the following mechanisms: crush, transection, stretch, and intrinsic neuropathy.8,9

6.2.2 Demyelination Demyelination is the loss of the myelin layer, either isolated or associated with axonal damage. In the latter case, there is some alteration of the myelin sheath, but not of the SCs. As such, the lack of myelin around any axon segment only requires SC division for remyelination to occur

Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations within that segment. Etiologies include compression injuries with ischemia, edema, and intrinsic neuropathies.8,9

●

6.3 EDSs for Preoperative Evaluations During this stage of evaluation, EDSs are useful to complement the clinical examination of patients, detect signs not confirmed by neurological examination, and guide in the diagnosis and therapeutic management of patients. However, EDSs will never replace a thorough medical history and physical examination. In general, EDSs help to safely: (1) pinpoint the site of injury (i.e., anterior horn, root, plexus, terminal nerve, neuromuscular junction); (2) identify the underlying pathophysiological process (i.e., demyelination and/or axonal damage); (3) establish the timing, severity, and extent of injury; (4) generate a list of possible diagnoses (e.g., compression syndrome, mononeuropathy, diffuse neuropathy); and (5) assess progression, which allows for some estimate regarding the prognosis for functional recovery10,11 (▶ Table 6.1). EDSs performed at different time points over the course of follow-up help establish whether axonal regeneration is present or not, thereby assisting with predicting prognosis, as well as the need and timing of surgical intervention. It should be noted that the optimal timing for performing EDSs is 2 to 3 weeks post injury (i.e., after the WD process is completed), because none of the electrical changes that define a nerve injury are likely to be evident earlier. Sensory nerve conduction studies (SNCSs), motor nerve conduction studies (MNCSs), and electromyography (EMG) are among the studies recommended during this assessment phase.

6.3.1 Technical Considerations The same equipment is used for both EMG and SNCS and should meet the following specifications: Table 6.1 Electrodiagnostic studies (EDSs): preoperative and intraoperative EDS techniques are demonstrated Preoperative NCS

Intraoperative Evaluation of spontaneous activity:

●

Sensory

●

●

Motor

Evaluation of evoked responses:

EMG

Continuous EMG

●

●

Recording equipment is composed of: (1) an amplifier to eliminate potential interference, (2) recording channels, (3) enough sensitivity to measure the amplitude of potentials, which range from 1 µV to 10 mV, (4) filters to reduce distortion and interference, measured in hertz (Hz; ranging from 2 to 10,000 Hz), (5) a display screen, (6) an audio amplifier and AD converter, and (7) a printer. A stimulator with which stimulus intensity, frequency, and duration can be controlled; generally, this will entail the use of surface electrodes (adhesive, flat metal, and/or ring surface electrodes). Recording electrodes: this usually would involve flat surface electrodes (adhesive, flat metal, and/or ring) or concentric or Teflon-coated monopolar needle electrodes for EMG, and an active electrode and reference electrode for SNCS.7

Recording is performed with the patient lying on an examination table or in a bed. Electrodes are then placed at sites that are specific to the study being performed. The process begins with stimulating a specific site via an electrical current until a desired potential is reached. EMG recording is obtained by introducing the concentric needle into the muscle being tested (▶ Fig. 6.1).7

Equipment and Electrodes All data are recorded based on parameters that will be reviewed later, with internationally standardized values available for each potential. Patients may feel some discomfort or experience a tingling sensation. However, these studies are generally well tolerated.

6.3.2 Nerve Conduction Studies/ Electroneurography Nerve conduction studies are performed by applying some supramaximal electrical stimulus that triggers the activation of all fibers through a percutaneous electrode placed over a specific nerve. This generates an AP, which is recorded by other surface electrodes applied at a defined distance. Based on whether it is a sensory or motor study, electrodes are placed in a sensory innervation territory or into a specific muscle innervated by the nerve under study, respectively.6,7,11,12,13

●

Stimulated EMG

●

SSEP

Motor Nerve Conduction Studies

●

MEP

●

NAP

MNCSs evaluate the muscular response or compound motor action potentials (CMAPs) by electrically stimulating the nerve that should innervate the muscle. The CMAP is the summation of AP from all the MUs (▶ Fig. 6.2).6,7,11,12,13

Abbreviations: EMG, electromyography; MEP, motor evoked potentials; NAP, nerve action potential; NCS, nerve conduction studies; SSEP, somatosensory evoked potentials.

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Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations

Fig. 6.1 Equipment and electrodes. Left: The recording equipment consists of one amplifier, recording channels, sensitivity, a display screen, filters, an audio amplifier, and a printer. Right: Recording electrodes: stimulator (A), ring (B), surface (C), and monopolar needle (D). (Source: Neurophysiology Department archives, American British Cowdray Medical Center.)

Fig. 6.2 Motor nerve conduction studies. Recording of motor action potentials for the ulnar nerve. (Source: Neurophysiology Department archives, American British Cowdray Medical Center.)

Fig. 6.3 Sensory nerve conduction studies. Recording of sensory action potentials for the ulnar nerve. (Source: Neurophysiology Department archives, American British Cowdray Medical Center.)

Sensory Nerve Conduction Studies SNCSs assess sensory nerve action potentials (SNAPs), which are the summation of APs from sensory fibers of the nerve produced by stimulation. Contrary to MNCSs, the amplitude is measured in µV. SNAPs can be either orthodromic or antidromic, and nerve conduction

50

velocity (NCV) is measured by stimulating only a single point (▶ Fig. 6.3).6,7,11,12,13

Parameters to Be Evaluated The following parameters of the generated potentials are analyzed:6

Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations ●

●

●

●

●

●

Latency is the time interval between the moment of nerve stimulation and the onset of the resulting potential. It is measured in milliseconds (ms) and represents the velocity of transmission. Amplitude is the maximum voltage difference between two points (i.e., the intensity of the impulse) expressed in millivolts (mV) for motor studies and in microvolts (µV) for sensory studies. It is measured from baseline to maximum peak, and is related to the number of activated fibers. Area provides information on the number of axons being stimulated. NCV is calculated by dividing latency into the distance between the stimulation and recording points. NCV is measured in meters per second (m/s), and reflects myelin integrity. Duration reflects the degree of synchrony between nerve fibers. Wave morphology: In general, waves show a monophasic or biphasic configuration. A polyphasic configuration denotes chronodispersion (▶ Fig. 6.4).

Unlike demyelinating lesions, which frequently exhibit increased latency with a resulting decrease in NCV, sensory, motor, and mixed axonal injuries characteristically display some reduction in the amplitude of APs.13

Delayed Responses: F-Wave and H-Reflex Late responses may be evaluated when lesions affect the proximal segments of the nerve structure, making it impossible to use conventional electroneurography.

F-Wave After a stimulus is applied, it travels antidromically to the anterior horn of the spinal cord where neurons generate small APs that travel back (orthodromically), thereby activating the muscle and generating a small-amplitude response (less than 10%), which is not elicited in all stimuli. Latency may be variable, so it is advisable to repeatedly apply series of 10 to 20 stimuli. F-wave studies are useful for identifying proximal lesions in nerves; but they are only of limited value for diagnosing radiculopathies and of no use assessing posterior roots.14

H-Reflex The H-reflex is the electrophysiological analogue of the stretch reflex; hence, it assesses sensory and motor fibers at a specific metameric level. It is initiated with a submaximal stimulus. In adults, it is consistently evoked from the flexor carpi radialis muscle by stimulating the median nerve at the elbow; and from the flexor muscles of the foot by stimulating the tibial nerve in the popliteal fossa. In these contexts, it is only useful for C7 and S1 radiculopathies, respectively.

6.3.3 Electromyography

Fig. 6.4 Parameters. Latency, amplitude, area, conduction velocity, duration, and phases are evaluated for each potential.

EMG is the group of recording techniques that assesses electrical activity within skeletal muscles. The selection of muscles depends on the patient’s clinical picture. The examination involves a single-use concentric needle electrode, which is introduced into the muscle, where it records four phases of muscular activity. The signals are displayed on a digital screen, and can also be converted into an audible acoustic file. The following phases are examined:12,15 ● Insertion phase: This is derived from some needleinduced mechanical irritation stimulus, and characterized by the presence of small-amplitude potentials and a crackling sound. ● Resting phase: This phase is characterized by a flat trace (electrical silence) under normal conditions. “Plate activity” can occasionally be detected due to irritation of the neuromuscular plate; but this does not imply pathology. ● Mild contraction phase: This phase evaluates the configuration of the MU potential (MUP), which represents the summation of APs for each MU fiber. The contraction force is determined by the number and frequency

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Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations

Fig. 6.5 Electromyography phases. (a) Normal pattern and (b) neurogenic pattern. Phases of the EMG include: (1) insertion, (2) resting, (3) mild contraction, (4) maximal contraction. The image in (a) shows a normal pattern for each phase, and in (b), the pattern secondary to a nerve lesion.

●

with which simultaneous activated MUs are fired. The following MUP parameters are examined: ○ Duration: This is determined by the synchrony of discharges and ranges from 8 to 14 ms. ○ Amplitude: This reflects the number and synchrony of discharging fibers and ranges from 0.5 to 2 mV. ○ Phases: The phases represent the section of a wave that falls between two baseline crossings; they can be either biphasic or triphasic. Maximal contraction phase: This phase determines MUP recruitment, which is called spatial recruitment if MUPs are increasing in number, and temporal recruitment if they are increasing in frequency. This makes it difficult to identify the individual MUs, as well as the baseline, and is known as an interference pattern (the normal muscle recruitment pattern).

Neurogenic Pattern on Electromyography EMG findings are not pathognomonic of any nosological entity; nevertheless, it is possible to differentiate between normal, neurogenic, and/or myogenic patterns. There is a high level of concordance (greater than 90%) between EMG and muscle biopsy findings. Accordingly, EMG can be useful for the diagnosis of peripheral nerve lesions when a neurogenic pattern is present. During denervation, since there is an increase in fiber excitability, the activity of the insertion phase also increases. However, this may decline due to fibrotic changes in the muscle. The resting phase of the neurogenic pattern is characterized by the presence of spontaneous activity, indicated by fibrillation, fasciculations (spontaneous, repetitive, short, biphasic discharges), and acute positive waves. This phase commonly starts 3 weeks after the injury and tends to disappear over time because of reinnervation or fibrosis. Repetitive complex discharges may also be present. The presence of fasciculations is suggestive of a proximal lesion (anterior horn or anterior nerve root). In the mild contraction phase, MUPs are polyphasic and greater in duration and amplitude; these characteristics become more pronounced as the process becomes more chronic.

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However, innervation MUPs are short and smaller in amplitude. In the maximal contraction phase, the recruitment pattern is incomplete which, from higher to lower severity, can be: high-intermediate, low-intermediate, simple, or absent (▶ Fig. 6.5).7,15

Registry Errors and Other Considerations EDSs may yield false-positive or false-negative results. As age is among the factors commonly associated with altered results, it is necessary to remember that children complete myelination at 4 to 5 years of age, and that CV begins to decline at roughly 60 years of age. At temperatures below 33 °C, CV slows down to 1.5 to 2.5 m/s; and latency increases by 0.2 ms per degree reduction. Tissue resistance can reduce amplitude. Results may be altered by technical factors such as the improper placement of recording electrodes, increased tissue impedance (resistance), the wrong nerve being stimulated, or the presence of an anastomosis not previously detected (e.g., MartinGruber or Riche-Cannieu anastomosis).6,7 Although EMG is a low-risk procedure and complications are rare, it is important to know if a patient has a central catheter, pacemaker, or a coagulation disorder before conducting such a study.12

6.4 Electrophysiological Findings with Different Types of Nerve Injury Peripheral nerve pathologies exhibit neurophysiological changes that correlate well with ED records. For example, during the initial phases of chronic compression, CV is reduced by the demyelination–remyelination process. In the case of a distal lesion, distal latency is increased and can coexist with decreased CMAP amplitude due to chronodispersion (increased potential duration); except with severe compression, the EMG does not exhibit any changes, due to the absence of axonal damage. With acute compression, conduction block due to segmental demyelination is a common finding. Recovery

Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations Table 6.2 Clinical correlation: correlating electrophysiological findings with nerve lesions Grade injury

Neurapraxia I

Axonotmesis II–IV

Neurotmesis V

NCS

Conduction block with decreased amplitude that is restored within a few weeks

First day: proximal CMAP amplitude reduced. After 4 days, distal CMAP amplitude reduced

Absent proximal CMAP. After 4 days, absent distal CMAP

No spontaneous activity Normal MUP Recruitment decreased of MU that is restored within a few weeks

First day: recruitment decreased. After 3 weeks: spontaneous activity, abnormal MUP If reinnervation: polyphasic and prolonged MUP If recovery: fewer denervation signs and increased recruitment

First day: absent MUP with no spontaneous activity. After 3 weeks: spontaneous activity, absent MUP. Reinnervation signs only if reconstructive surgery successful; otherwise spontaneous activity disappears by fibrosis

EMG

Abbreviations: CMAP, compound motor action potential; EMG, electromyography; MU, motor unit; MUP, motor unit potentials; NCS, nerve conduction studies.

is observed after a number of days or weeks. NCSs with evidence of reduced amplitude or CMAP area between proximal and distal stimulation points are useful tools. WD manifests as the loss of MUs and presence of spontaneous activity (fibrillations and positive acute waves). These findings indicate neurapraxia. The pathophysiological substrate of acute traction or transection lesions and severe entrapment is WD, since it implies the loss of nerve fiber continuity. In such cases, EMG shows evidence of fibrillations and positive acute waves due to increased spontaneous activity, with lost MU proportional to the degree of degenerated fibers. NCSs show reduced amplitude or absence of CMAP. During the first 48 to 72 hours, the distal segment maintains function and can respond to a stimulus. However, since conduction capacity is lost after this time, it is impossible to differentiate conduction block from axonotmesis in early EDSs.7,16 Most of the time, different degrees of lesion severity coexist within the same segment. In the EMG, reinnervation data show longer-duration, low-amplitude polyphasic potentials (▶ Table 6.2).

6.5 When Are EDSs Indicated? The distal segment of the damaged nerve becomes nonexcitable after 5 to 7 days for motor fibers, and after 7 to 10 days for sensory fibers. Since the denervation process is complete after 3 weeks, EDSs are not indicated before that time. This is because, even though they may provide data about location, they yield no information about the extent or severity of injury. Subsequent monitoring during preoperative evaluations depends on the type of lesion and should be individualized. The first monitoring evaluation should be conducted at 3 months, when EDSs tend to exhibit spontaneous innervations.11

6.6 EDSs for Intraoperative Evaluations Appreciating that the different neurophysiological recording techniques used for routine preoperative evaluation may also be used during surgical procedures has enabled clinicians to integrate them into multimodal intraoperative monitoring (MIOM). Using different neurophysiological techniques adapted to each procedure permits the objective and continuous identification and quantification (with unique time resolution) of certain parameters that indicate the functional status of nerve structures at risk during surgery. Results are compared against preestablished reference values so that possible changes can be evaluated during surgery based on the structure being monitored. Since these changes are detected early, pertinent measures can be taken to restore function and avoid potential adverse consequences. In 1960, Kline and De Jonge were the first to report using evoked nerve potentials to evaluate nerve lesions.17,18 MIOM has two major functions: the continuous monitoring of a specific nerve pathway’s functional integrity to aid in the early detection of variations that might require changes in surgical management; and mapping for the timely identification of nerve structures that should be preserved. Recording techniques follow the same principles applied during the preoperative phase, except that monopolar needles are used for EMG recording. Moreover, all the recording and stimulation electrodes in the surgery field must remain sterile.

6.6.1 Lesions-in-continuity A neuroma-in-continuity is a disorganized tissue mass that contains axons, connective tissue, and different types

53

Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations prepare the surgical field, and perform intraoperative manipulation of the nerve under study. Currently, the following intraoperative recording techniques can be considered for PNS, divided based on bioelectrical signals: (1) spontaneous activity: EMG and (2) evoked responses: somatosensory evoked potentials (SSEPs), evoked EMG (muscle APs), and nerve action potentials (NAP). The recorded responses can be obtained from the cerebral cortex, spinal cord, muscle, or the peripheral nerve itself. The study selected will depend on the structure and function that must be evaluated.21,22,23,24,25

Continuous Intraoperative Electromyography Fig. 6.6 Lesion-in-continuity. With a neuroma-in-continuity, the external anatomical integrity of nerve remains unchanged, so the viability of the nerve trunk is evaluated through NAP conduction. The black arrow demonstrates the anatomical (but not necessary functional) integrity of the nerve after a traumatic event.

of cells, including macrophages, fibroblasts, and SC. It can be caused by a variety of mechanisms which result in the nerve failing to regenerate adequately. Lesions-in-continuity develop in up to 70% of nerve lesions. As suggested by the name, anatomical continuity is preserved within the nerve trunk. However, this does not imply that the internal structure is preserved. In some cases, function can be spontaneously restored; but this is not the rule, and the prognosis is difficult to establish. It is for this specific type of lesion that using MIOM permits practitioners to evaluate peripheral nerve function and determine the potential for spontaneous functional recovery, since observation and palpation are insufficient to determine the functional viability of a nerve trunk during surgery. Therefore, the different intraoperative recording techniques are the only ways to preserve the function of a nerve, since external appearance does not correlate with histology (▶ Fig. 6.6).19,20

6.6.2 Intraoperative Monitoring Techniques MIOM is especially useful for some peripheral nerve lesions that pose interesting surgical challenges. Unlike other studies, MIOM provides real-time functional data. For this reason, it is essential to know, in detail, the patient’s medical history and baseline neurological status, as well as the regional anatomy, surgical goals, and type of anesthesia used, since the data obtained can alter the course of the surgical procedure (as in the specific case of a lesion-in-continuity). The multidisciplinary team must know how to position the electrodes, apply the stimulus,

54

Continuous intraoperative EMG is the continuous recording of the electrical activity of the muscle(s) of interest (depending on the surgery). It is useful to prevent nerve trunk damage during surgical manipulation, which is manifested as increased muscle activity due to irritation of the nerve. Surgical manipulation should be altered or interrupted in the presence of sustained tonic activity that does not disappear immediately after the surgical manipulation that triggered it is discontinued. The EMG activity generated by irritating the nerve is displayed on a digital screen; and an audible signal can be used to alert the surgeon as to when the nerve is in proximity.26,27

Stimulated Intraoperative Electromyography Stimulated intraoperative EMG is the application of a stimulus with subsequent recording of a compound muscle AP, using the same electrodes as for continuous EMG recording. It is a mapping technique used to detect nerves of interest. It is useful for the evaluation of neuromas-in-continuity near the target muscle, or large nerve trunk lesions on their way to the innervated muscle (▶ Fig. 6.7).26,27

Somatosensory Evoked Potentials Evoked potentials are electrical signals generated by the nervous system in response to a specific external stimulus. Measuring SEPs entails applying a peripheral stimulus to the nerve trunk and subsequently recording the response at the cortical level of the sensory pathway or at upward relay stations (e.g., Erb’s point, the popliteal fossa, or the cervical cord). Responses are compared with reference values obtained before the surgical procedure is begun. Wave morphology, amplitude, and latency are evaluated. In the upper limbs, the response is elicited by stimulating the median and/or ulnar nerve; and in the inferior limbs, the response is elicited by stimulating the posterior tibial nerve and/or peroneal nerve. The intraoperative interpretation of results relies on the detection

Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations

Fig. 6.8 Intraoperative somatosensory evoked potentials. Intraoperative recording of SSEP via stimulation of the median and radial nerves after an infraclavicular brachial plexus injury. (Source: Neurophysiology Department archives, American British Cowdray Medical Center.)

Fig. 6.7 Intraoperative electromyography. Intraoperative EMG recording during neurolysis of the ulnar nerve for neurotization of the musculocutaneous nerve. (Source: Neurophysiology Department archives, Hospital Regional Universitario de Málaga.)

of reliable, significant changes, such as a > 50% decrease in amplitude or a > 10% decrease in latency. SEPs are useful for the evaluation and recording of preganglionic lesions involving the supraclavicular brachial plexus when combined with recording of SNAPs. Generally, it is possible to determine which nerve roots are in continuity with the central nervous system, thereby avoiding extensive, time-consuming dissections in cicatricial or difficult-access areas (▶ Fig. 6.8).28,29

Motor Evoked Potentials MEPs are obtained using high-voltage, short-duration repetitive stimulations, with electrodes placed on the scalp to evaluate motor responses within the muscles being monitored. Similar to SSEP, this technique enables the evaluation of more proximal segments of the nerve trunk.

Nerve Action Potentials The use of NAPs involves direct stimulation of the nerve trunk proximal to the area of the lesion, so as to obtain the NAP distal to the lesion using recording electrodes. At least 4,000 myelinated nerve fibers are required to evoke NAPs. Stimulation electrodes have two tips, while recording electrodes have three J-shaped tips to be in direct contact with the nerve and reduce propagation of the stimulus, thereby preventing artifacts. This technique is useful for the evaluation of lesions-in-continuity, since it permits clinicians to identify impulse transmission within the nerve trunk, in this way determining the need

Fig. 6.9 Nerve action potential. Direct nerve stimulation for the recording of NAP after neurolysis of the median nerve.

to carry out more complex reconstruction procedures. It is also possible to use quadrant mapping to differentiate healthy areas of the nerve trunk, so only partial reconstructions are performed (▶ Fig. 6.9).19,30,31,32

Intraoperative Monitoring Limitations The main limitations of NAPs relates to technical problems. EMG is affected by the use of muscle relaxants, since it requires the partial preservation of functioning MU to elicit a motor response. Moreover, it only assesses the segment from the point of stimulation to the muscle; but there can be conduction block proximal to the stimulation point. Using MEPs can partially solve this problem.

55

Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations

6.6.3 Surgical Procedures When a lesion’s pathogenesis involves partial injury to the nerve trunk or the development of lesions-incontinuity due to either extraneural cicatricial tissue or a neuroma-in-continuity, MIOM plays a key role in determining the most suitable technique to restore nerve function. Neurolysis is a surgical procedure that entails removing any cicatricial tissue that is pressing on the nerve. This is the only surgical procedure indicated when there is evidence of nerve impulse transmission after decompression using NAP recordings. In the absence of conduction, it is recommended that one resect the damaged segment and perform reconstruction with a graft.33 Similarly, with severe lesions of the brachial plexus involving radicular avulsion, it is of vital importance to identify the functionality of the proximal stumps of the damaged roots (i.e., that they remain connected to the spinal cord). This is because, if integrity is maintained, they can be used as axon donors for reconstruction. This is not possible in the case of preganglionic involvement.6,19 Furthermore, MIOM can be used to identify specific groups of fascicles with the aim of performing nerve transfers. This procedure consists of donating the proximal end or fascicles of a healthy nerve to the distal end of a damaged nerve. A well-known example is the Oberlin technique, with which the fascicles that innervate the flexor carpi ulnaris muscle are used to anastomose with the muscular branches of the musculocutaneous nerve to the biceps, in patients with paralysis of the elbow secondary to an incomplete brachial plexus injury.34 Based on the recording technique used, MIOM in the PNS enables surgeons to: (1) identify damaged nerves or specific areas of injury within a nerve trunk; (2) establish the severity and location of the nerve injury; (3) prevent possible nerve injury from intraoperative manipulation; (4) guide surgical practice for the application of different reconstruction techniques (decompression, neurolysis, or resection and application of a graft); (5) identify the presence of radicular avulsions; (6) identify nerve topography to allow for the safe collection of nerve biopsy specimens; (7) identify healthy fascicles that are susceptible to sectioning; and (8) provide information regarding the prognosis of a nerve injury.25 In some situations, using MIOM is not essential, as in late injuries beyond 1 year of evolution, for which there would be limited likelihood of restoring nerve function using different reconstruction techniques. The reason for this is that they present irreversible changes in the nerve trunk and effector organs after the degeneration process.19

56

6.7 EDSs for Postoperative Evaluations Utilizing different EDS techniques to monitor patients after surgery depends on the type of procedure performed. The main goals are to establish the procedure’s effectiveness (due to the presence of electrical signs which precede clinical recovery), as well as the final outcome of the technique used. The major interest of these studies lies in the follow-up of nerve reconstruction (neurorrhaphy with or without grafting). The timing of the first clinical and neurophysiological manifestations of functional recovery of a nerve graft is highly variable, as late as 1 to 2 years post reconstruction. Motor recovery, from a clinical and electrophysiological perspective, occurs before sensory recovery. Sometimes, clinical evolution is disproportional to neurophysiologic evolution. Whereas in some cases this relationship is acceptable and concordant, in others clinical recovery is completely disproportionate to the slowness of NCV. Thus, it is necessary to highlight the importance of the individual evaluation in each particular case.35 Despite this limitation, EDSs provide data that permit clinicians to evaluate whether the intervention adopted has been successful or not. The first step involves knowing when to order EDSs; and this depends on the time that is likely to elapse before reinnervation of target muscle occurs. This, in turn, relates to the distance between the neurorrhaphy area and the motor end plate of the muscle that is being reinnervated. The following factors should be considered: (1) axons grow approximately 1 to 3 mm/day; (2) axon growth generally begins about 7 days after anastomosis; and (3) only 60% of fibers cross the first suture line, and not all fibers reach the intended muscle.36 Therefore, when performing neurotization (as with the Oberlin procedure) using direct neurorrhaphy (wherein the distance from the area of neurorrhaphy to the target muscle is less than 10 cm in most cases), the first signs of reinnervation may occur within 3 to 6 months. Three to six months postoperative is therefore a reasonable time at which to order neurophysiological studies. Electrical and clinical recovery with more proximal injuries—as with reconstructions with grafts in the primary upper trunk of the brachial plexus—are not expected to occur until at least 9 months have elapsed. Some authors37 argue that the first ED examination should be performed between 3 and 4 months after the surgical procedure, with the aim of recording the first electrical signs of reinnervation. The presence of lowamplitude, short-duration MUPs is the first sign of regeneration detected by EMG. MUPs with better synchronization, greater amplitude, and shorter duration develop over time. Moreover, the spontaneous activity

Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations caused by denervation during rest gradually disappears. If at the time of the first examination, there are no signs of reinnervation, one must repeat the study within a period no longer than 2 months. It also is advisable to examine several muscles innervated by the same nervous structure that was repaired. Reinnervation commonly occurs first in more proximal muscles, but there are exceptions (e.g., with lesions involving the primary upper trunk, reinnervation of biceps sometimes precedes that of the deltoid). When there is no electrical sign of reinnervation at the time of this second postoperative evaluation, surgical exploration should be considered, due to the likelihood that the initial nerve restoration was unsuccessful. This being said, some authors advise against such exploration, since very late nerve regeneration sometimes does occur. It is considered advisable to perform a subsequent examination 6 months after nerve repair when studies show electrical signs of reinnervation, this time focusing on more distal muscles within the denervated area. A further evaluation 1 year after surgery is also recommended. However, it should be considered that regenerating fibers are initially amyelinic, so CV will generally be much lower than normal during the early phases of postoperative recovery. Rarely, physiological velocities are achieved post neurorrhaphy. One final examination, which is often not performed, can be done 3 to 4 years after surgery to establish the degree of recovery and resulting sequelae. In some cases, EDSs show evidence of reinnervation, but significant motor function is not achieved. Although the cause of such failure is unknown, it may be related to the preoperative prognosis and/or to the inability of the motoneuron to induce maturation within the new MU structures.38

6.8 Conclusion Undoubtedly, EDSs enable surgeons to identify nerve injuries, differentiate the underlying pathophysiological mechanisms, and assess injury severity and time course. Moreover, they assist with intraoperative decision-making, particularly with surgical procedures indicated for the treatment of traumatic injuries or tumors. The reason for this is that they permit the surgical team to establish the need to perform more complex nerve reconstructions that involve resection of the damaged segment and application of a graft, as opposed to decompression by simple neurolysis. Accordingly, modifying surgical management to require less complex surgical intervention significantly reduces surgical time, limits the risk of excessive manipulation of nerve tissue (decreasing the probability of iatrogenic lesions), and provides insights into the functional status of nerve trunks involved in the lesion and their effector organs. Moreover, long-term functional prognosis can be established with data collected during postoperative

follow-up, even though, in some cases, the clinical findings are inconsistent with their electrical counterparts.

References [1] Rodríguez-Aceves CA, Cárdenas-Mejía A. Experiencia de un año en el Hospital General “Manuel Gea González” en las lesiones nerviosas del miembro superior y plexo braquial. Arch Neurocien. 2013; 18(3): 120–125 [2] Kim DH, Midha R, Spinner RJ. Kline y Hudson. Lesiones Nerviosas. Philadelphia, PA: Elsevier; 2010 [3] Llusá M, Palazzi S, Valer A. Anatomía quirúrgica del plexo braquial y de los nervios de la extremidad superior. Panamericana; 2013 [4] Mackinnon S. Nerve Surgery. 1st ed. New York, NY: Thieme; 2015 [5] Guyton CG, Hall JE. Textbook of Medical Physiology. 11th ed. Philadelphia, PA: Elsevier; 2006 [6] Kimura J. Electrodiagnosis in Diseases of Nerve and Muscle: Principles and Practice. 4th ed. Oxford: Oxford University Press; 2013 [7] Iriarte-Franco J, Artieda-González J. Manual de Neruofisiología Clínica. 1st ed. Editorial Panamericana; 2013 [8] Oh SJ. Color Atlas of Nerve Biopsy Pathology. 1st ed. Boca Raton, FL: CRC Press; 2001 [9] Cuccurullo S. Physical Medicine and Rehabilitation Board Review. New York, NY: Demos; 2004 [10] Fuller G, Bone I. Neurophysiology. J Neurol Neurosurg Psychiatry. 2005; 76 S2:ii1 [11] Chémali KR, Tsao B. Electrodiagnostic testing of nerves and muscles: when, why, and how to order. Cleve Clin J Med. 2005; 72 (1):37–48 [12] Gooch CL, Weimer LH. The electrodiagnosis of neuropathy: basic principles and common pitfalls. Neurol Clin. 2007; 25(1):1–28 [13] Mallik A, Weir AI. Nerve conduction studies: essentials and pitfalls in practice. J Neurol Neurosurg Psychiatry. 2005; 76 Suppl 2:ii23– ii31 [14] Fisher MA. H reflexes and F waves. Fundamentals, normal and abnormal patterns. Neurol Clin. 2002; 20(2):339–360, vi [15] Mills KR. The basics of electromyography. J Neurol Neurosurg Psychiatry. 2005; 76 Suppl 2:ii32–ii35 [16] Llusá M, Palazzi S. Anatomía quirúrgica del plexo braquial. Panamericana; 2013 [17] Zouridakis G, Papanicolau A. A Concise Guide to Intraoperative Monitoring. Boca Raton, FL: CRC Press LLC; 2012 [18] Galloway GM. The preoperative assessment. In: Galloway GM, Nuwer MR, Lopez JR, Zamel KM. Intraoperative neurophysiologic monitoring. New York, NY: Cambridge University Press; 2010:10–18 [19] Socolovsky M, Siqueira M, Malessy M. Introducción a la Cirugía de los Nervios Periféricos. Argentina: Ediciones Journal; 2013 [20] Flores LP. The importance of the preoperative clinical parameters and the intraoperative electrophysiological monitoring in brachial plexus surgery. Arq Neuropsiquiatr. 2011; 69(4):654–659 [21] Sclabassi RJ, Balzer J, Crammond D, et al. Technological advances in intraoperative neurophysiological monitoring. In: Dauber JR, Maguiere F, Nuwer MR, et al., eds. Handbook of Clinical Neurophysiology, Intraoperative Monitoring of Neural Function. New York, NY: Elsevier; 2008:464–480 [22] Jameson LC, Sloan TB. Neurophysiologic monitoring in neurosurgery. Anesthesiol Clin. 2012; 30(2):311–331 [23] Kim SM, Kim SH, Seo DW, Lee KW. Intraoperative neurophysiologic monitoring: basic principles and recent update. J Korean Med Sci. 2013; 28(9):1261–1269 [24] Slimp JC. Intraoperative monitoring of nerve repairs. Hand Clin. 2000; 16(1):25–36 [25] Wang H, Spinner R. Intraoperative testing and monitoring during peripheral nerve surgery. In: Nuwer M, ed. Handbook of Clinical Neurophysiology. New York, NY: Elsevier BV;2008:764–773 [26] Holland NR. Intraoperative electromyography. J Clin Neurophysiol. 2002; 19(5):444–453

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Electrodiagnostic Pre-, Intra-, and Postoperative Evaluations [27] Malessy M, Pondaag W. Electromyography, nerve action potential, and compound motor action potentials in obstetric brachial plexus lesions: validation in the absence of a “gold standard”. Neurosurgery. 2009; 65(4):A153–A159 [28] Salengros JC, Pandin P, Schuind F, Vandesteene A. Intraoperative somatosensory evoked potentials to facilitate peripheral nerve release. Can J Anaesth. 2006; 53(1):40–45 [29] Sutter M, Eggspuehler A, Muller A, Dvorak J. Multimodal intraoperative monitoring: an overview and proposal of methodology based on 1,017 cases. Eur Spine J. 2007; 16 Suppl 2:S153–S161 [30] Wang H, Bishop AT, Shin AY. Intraoperative testing and monitoring during brachial plexus surgery. In: Nuwer M, ed. Handbook of Clinical Neurophysiology. New York, NY: Elsevier BV;2008:720–730 [31] Everett R, Happel LT. Intraoperative nerve action potential recordings: technical considerations, problems and pitfalls. Neurosurgery. 2009; 65(4)(Suppl):A97–A104 [32] Pondaag W, van der Veken LP, van Someren PJ, van Dijk JG, Malessy MJ. Intraoperative nerve action and compound motor action

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[33] [34]

[35] [36]

[37] [38]

potential recordings in patients with obstetric brachial plexus lesions. J Neurosurg. 2008; 109(5):946–954 Robla J, Domínguez M, Socolovsky M. Técnicas modernas en microcirugía de los nervios periféricos. Argentina: Ediciones Journal; 2014 Rodríguez-Aceves CA, Collado-Ortíz MA, Correa-Márquez LI. Monitoreo intraoperatorio multimodal y su aplicación en cirugía de nervios periféricos: ¿Cuándo es de utilidad? An Med (Mex). 2016; 61 (2):123–131 Portillo R, Rojas E, Vera J, Concha G. Seguimiento neurofisiológico en injertos de nervios periféricos. An Fac Med. 2003; 64(1):63–70 Brown WF. Negative symptoms and signs of peripheral nerve disease. In Brown WF, Bolton CF, eds. Clinical Electromyography. 2nd ed. Boston, MA: Butterworths; 1993:95–116 Montserrat L. Lesiones traumáticas del nervio. Rehabilitación. 1993; 27:44–55 Parry GJ. Electrodiagnostic studies in the evaluation of peripheral nerve and brachial plexus injuries. Neurol Clin 1992;10(4):921–934

Magnetic Resonance Neurography and Peripheral Nerve Surgery

7 Magnetic Resonance Neurography and Peripheral Nerve Surgery Daniela Binaghi and Mariano Socolovsky Abstract Magnetic resonance neurography has become the imaging modality of choice for identifying and characterizing pathology within the peripheral nervous system. It provides vital information for patients in whom surgical intervention is being contemplated. Keywords: magnetic resonance neurography, peripheral neuropathy, peripheral nerve trauma, nerve entrapment, peripheral nerve tumor

7.1 Introduction Peripheral neuropathy is a commonly encountered disorder. Although clinical examination and electrophysiological studies are the traditional mainstay of the diagnostic work-up, magnetic resonance imaging (MRI) has recently become an important component of this process, facilitating operative interventions, including: targeted fascicular biopsies; making surgical exploration faster and more straightforward; and enhancing neurological outcomes. Furthermore, a new MRI technique called diffusion tensor imaging (DTI) is becoming available, allowing for the assessment of axonal integrity in neural tissues and enabling three-dimensional (3D) reconstruction to evaluate neural tracts (diffusion tensor tractography [DTT]). Unfortunately, however, DTI–DTT is a time-consuming technique with technical difficulties that need to be overcome. In addition, data interpretation requires experience and further comparisons with surgical and histological findings. The term magnetic resonance neurography (MRN) was introduced in the early 1990s to describe the application of high-resolution sequences to visualize peripheral nerves and surrounding soft tissues. It requires the use of a high-field MR system (1.5-T or 3-T) and dedicated radiofrequency coils. Depending on the clinical picture,

contrast media may not be required, though patterns of contrast enhancement can distinguish between pathologies that have similar noncontrast appearances. MRN imaging evaluates nerve anatomy, signal intensity, internal pattern, and course, as well as the surrounding tissues and innervated muscles. Normal peripheral nerves appear isointense to muscle on T1-weighted (T1w) images and iso- to slightly hyperintense on T2weighted (T2w) images—depending on the amount of endoneural fluid—revealing a fascicular pattern. Meanwhile, normal nerves do not exhibit enhancement after gadolinium administration because of the nerve–blood barrier (▶ Fig. 7.1). On DTI, normal nerves show fractional anisotropy values greater than 0.4 to 0.5.1

7.2 Trauma Most patients with acute nerve transection do not require MRN imaging. Nevertheless, in patients without nerve transection—which accounts for the majority of serious injuries—it might be difficult to distinguish between those injuries that will and those that will not recover spontaneously and may require surgery. MRN imaging plays an essential role in this subset of patients. In an attempt to classify the physical and functional state of damaged nerves, Seddon2 introduced the terms neurapraxia, axonotmesis, and neurotmesis. Sunderland3 refined this classification, based on the recognition that axonotmetic injuries had widely variable prognoses, depending on the degree of connective tissue involvement. These terms and this classification system are useful, because they indicate the pathological status of the nerve, predict the prognosis if the injury is left untreated, and provide a guide to management. MRI can aid in distinguishing between these lesions, providing vital information for management and surgical planning.

Fig. 7.1 Normal median nerve within the carpal tunnel. On axial T1w (a), it is isointense to muscle (flexor carpi ulnaris, asterisk) and exhibits a fascicular appearance; on STIR (b), it exhibits mildly high signal intensity (arrows).

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Magnetic Resonance Neurography and Peripheral Nerve Surgery Table 7.1 MRN findings in traumatic nerve injuries Seddon classification Neurapraxia Axonotmesis

Neurotmesis

Sunderland classification

MRN findings

First degree

Nerve: increase SI on FSS Muscle: mild atrophy, no denervation

Second degree

Nerve: enlargement, increased SI on FSS Muscle: signs of denervation

Third degree

Nerve: ● Acute: enlargement, increased SI on FSS, loss of fascicular appearance ● Subacute/chronic: neuroma-in-continuity Muscle: signs of denervation

Fourth degree

Nerve: enlargement, increased SI, loss of fascicular appearance, blockage of axoplasmic flow on DTT Muscle: signs of denervation

Fifth degree

Nerve: Acute: gap shows high SI on FSS ● Chronic: terminal neuroma Muscle: signs of denervation ●

Abbreviations: DTT, diffusion tensor tractography; FSS: fluid-sensitive sequences; SI, signal intensity.

Fig. 7.2 Neurapraxia. On coronal STIR, note increased signal intensity in the C5 (arrow) and C6 roots (arrowhead) of the brachial plexus.

With neurapraxia, the nerve is intact, but cannot transmit impulses. With axonotmesis, the axon is damaged or destroyed, but most of the connective tissue framework is maintained. Meanwhile, with neurotmesis, the nerve is disrupted and the connective tissue framework is either totally lost or badly distorted. On MRN imaging, these three classes of injury look different4,5 (▶ Table 7.1). Typical MRN imaging findings in neurapraxic injuries (▶ Fig. 7.2) and Sunderland´s first-degree nerve lesions are a focal increase in nerve signal intensity on fluidsensitive sequences, combined with no signal abnormal-

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ities in muscle signal intensity, except for mild atrophy secondary to disuse. MRI findings in axonotmetic lesions include neural enlargement and transient increases in nerve signal intensity on T2w and short tau inversion recovery (STIR) images, combined with loss of the normal fascicular appearance, blurring of the perifascicular fat, and signs of muscle denervation (appearing within 24–48 hours); this is followed by muscle volume reduction and fatty atrophy if nerve regeneration does not occur. MRN is further able to distinguish axonotmetic injuries as subclassified by Sunderland. With a type III injury, the endoneurium is disrupted, intrafascicular fibrosis takes place, and a neuroma-in-continuity (▶ Fig. 7.3) is formed that appears, on MRN imaging, as a fusiform enlargement with intermediate to high signal intensity in fluid-sensitive images with variable contrast enhancement. With Sunderland type IV injuries, only the epineurium is intact, so MRN images demonstrate lost fascicular appearance, increased nerve signal intensity on T2w and STIR sequences, and blockage of the axoplasmic flow on DTT (▶ Fig. 7.4), which is an emerging MRN technique that generates a 3D image of neural tracts, thereby allowing clinicians to assess axonal integrity.6 During the acute stage of a neurotmetic injury, MRN can demonstrate nerve discontinuity (▶ Fig. 7.5), the gap filled with fluid and granulation tissue5 that, over time (1–12 months), will form proximal “bulbous-end” thickening with intermediate signal intensity on T1w images, and inhomogeneous intermediate to high signal intensity on T2w images; contrast enhancement is variable and dependent on the level of maturity of any fibrotic and regenerated nerve tissue involved in the repair. Diagnosis

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Magnetic Resonance Neurography and Peripheral Nerve Surgery

Fig. 7.3 Neuroma-in-continuity in the elbow, distal to the cubital tunnel. (a) Sagittal STIR and (b) axial proton density (PD) images show fusiform enlargement and a slight increase in signal intensity (arrows).

Fig. 7.4 Peroneal injury secondary to knee dislocation. On axial PD images (a), the peroneal nerve (arrow) shows loss of fascicular appearance. On fiber tract images (b), blockage of peroneal axonal flow is seen, while the tibial nerve displays normal axonal flow (arrowhead). After surgery (c), axonal flow is restored (arrow).

Fig. 7.5 Root avulsion. (a) An axial reformatted T2w 3D image shows complete left brachial plexus root avulsion (dashed circle). (b) Tractographic image of the lumbosacral plexus overlaid on coronal T2w MRN demonstrates avulsion of L5 (arrow) and S1 (arrowhead) right-sided nerves, but normal contralateral nerves (dotted arrows).

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Magnetic Resonance Neurography and Peripheral Nerve Surgery

Fig. 7.6 Terminal ulnar nerve neuroma in the distal forearm. (a) Sagittal T2w shows fusiform enlargement of the nerve (arrow) consistent with a terminal neuroma. (b) Axial STIR exhibits the gap (arrowheads). R, radial bone; U, ulnar bone.

Fig. 7.7 Carpal tunnel syndrome secondary to radial bursitis. (a) Axial PD-SPIR image shows radial bursa (asterisk) contacting with the median nerve, which is normal in appearance (arrow). (b) Tractographic image overlaid on axial PD exhibits decreased axonal flow (dotted arrow) in fascicles close to the bursitis.

of a stump neuroma is not always straightforward. For this reason, MRN should be performed as soon as possible, before repair tissue covers the gap, after which time imaging becomes very difficult (▶ Fig. 7.6).

7.3 Entrapment Neuropathies Compression neuropathies encompass a heterogeneous group of focal neuropathy syndromes characterized by peripheral nerve compression. Nerve compression results in pain, paresthesias, and lost function of the affected nerve. The term entrapment neuropathy defines a pressureinduced chronic compression injury. Although nerves may be injured anywhere along their course, they are more prone to compression, entrapment, or stretching as they traverse anatomically vulnerable regions, such as superficial or geographically constrained spaces.4 Compression may be episodic and may have a cumulative effect. The nerves affected by dynamic or fixed compressive neuropathy have an injury-related abnormal appearance, indicators of compression or swelling, as well as high signal on fluid-sensitive sequences, a sign of intraneural edema. Muscular denervation changes

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may also be evident in advanced cases. MRN imaging criteria used to determine the presence of compression are: (1) close contact with the compressive structure, (2) disappearance of the fat plane around the affected nerve, and (3) change in the normal nerve appearance. MRN imaging is particularly valuable in complex cases with discrepant nerve function test results, when a secondary cause is suspected (▶ Fig. 7.7), and in patients who require postsurgical evaluation (▶ Fig. 7.8).

7.4 Tumors Developing a classification system and nomenclature for peripheral nerve tumors has been difficult and confusing. However, advances in MRN imaging have improved the diagnostic work-up, helping to delineate the various differential diagnostic possibilities and determining whether lesions are intra- or extraneural. These advances have implications for safe and complete resection of both common and less common neurogenic and nonneurogenic tumors, as well as for targeted fascicular biopsy. The diagnosis of benign neurogenic tumors and pseudotumors can be suggested from their imaging

Magnetic Resonance Neurography and Peripheral Nerve Surgery appearances and characteristics; luckily, they are more common than secondary involvement in systemic malignancies and malignant peripheral nerve sheath tumor (MPNST). The clinical appearance of a neurogenic tumor is usually that of a soft-tissue mass that might be associated with symptoms related to the involved neural structures. The most common benign peripheral nerve tumors are schwannomas and neurofibromas. It is usually difficult, if not impossible, to reliably differentiate these two lesions on the basis of MRN imaging features, despite their different pathological characteristics. The typical MRN appearance (▶ Fig. 7.9) of a benign peripheral nerve tumor is that of a well-defined oval lesion, usually in continuity with the nerve of origin, which is less than 5 cm in diameter, isointense to muscle on T1w images, and hyperintense on T2w images, while exhibiting prominent enhancement after contrast administration. Often, there is an area of low signal on T2w images, which usually does not enhance, representing the classic “target sign” of a benign neurogenic tumor, caused by peripheral myxoid material and central fibrous tissue. On DTI, these lesions are associated with high apparent diffusion coefficient (ADC) values (> 1.1–1.2 × 10–3 mm/s2).7 Also, DTT can be used to visualize the 3D course of nerve fibers and bundles, which are displaced in the presence of schwannomas, but infiltrated by neurofibromas. DTT can also identify a “safe zone” in which dissection can be performed while avoiding damage to normal fascicles. MPNSTs are an extremely rare group of malignancies. Unfortunately, MRN differentiation of benign versus MPNSTs remains challenging.8 It has been suggested that a combination of two or more of the following MRI features can serve as indicators of malignancy: ill-defined or invasive margins; peritumoral edema; largest diameter greater than 5 cm; and heterogeneous signal intensity on T1w and T2w images.9 Low diffusivity values (ADC) indicate malignancy on DTI, while, on DTT, there will be partial or complete disruption of tracts.10 Even in the absence of such findings, malignancy must be suspected in patients who have tumors that have increased rapidly in size, become progressively painful, or produced a new neurological deficit.

7.5 Conclusion Fig. 7.8 Peroneal nerve entrapment, which developed after lateral ligament reconstruction surgery. (a) Sagittal T2w of the peroneal head shows the peroneal nerve (asterisk) passing through a constrained space. (b) Axial PD-SPIR demonstrates an altered fascicular pattern and increased nerve signal (arrow). BT, biceps tendon; LCL, lateral collateral ligament.

MRN imaging plays an essential role in the diagnostic work-up of peripheral neuropathies. It helps to establish the cause of the condition; confirms, locates, and characterizes the pathological process; and provides crucial information that may alter the choice of treatment or surgical plan.

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Fig. 7.9 Schwannoma versus neurofibroma. Axial PD (a, c) shows focal neural enlargement (arrow) with a similar image appearance. Tractographically reconstructed images demonstrate, in the first case (b), displaced tracts consistent with schwannoma (arrowhead), while in the second case (d) the mild disorganization (arrowhead) of tracts suggests neurofibroma. Both cases were confirmed histologically.

References [1] Chhabra A. Peripheral MR neurography: approach to interpretation. Neuroimaging Clin N Am. 2014; 24(1):79–89 [2] Seddon HJ. Three types of nerve injury. Brain. 1943; 66(4): 237–288 [3] Sunderland S. A classification of peripheral nerve injuries producing loss of function. Brain. 1951; 74(4):491–516 [4] Andreisek G, Crook DW, Burg D, Marincek B, Weishaupt D. Peripheral neuropathies of the median, radial, and ulnar nerves: MR imaging features. Radiographics. 2006; 26(5):1267–1287 [5] Chhabra A, Andreisek G, Soldatos T, et al. MR neurography: past, present, and future. AJR Am J Roentgenol. 2011; 197(3):583– 591

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[6] Lehmann HC, Zhang J, Mori S, Sheikh KA. Diffusion tensor imaging to assess axonal regeneration in peripheral nerves. Exp Neurol. 2010; 223(1):238–244 [7] Ahlawat S, Chhabra A, Blakely J. Magnetic resonance neurography of peripheral nerve tumors and tumorlike conditions. Neuroimaging Clin N Am. 2014; 24(1):171–192 [8] Li CS, Huang GS, Wu HD, et al. Differentiation of soft tissue benign and malignant peripheral nerve sheath tumors with magnetic resonance imaging. Clin Imaging. 2008; 32(2):121–127 [9] Wasa J, Nishida Y, Tsukushi S, et al. MRI features in the differentiation of malignant peripheral nerve sheath tumors and neurofibromas. AJR Am J Roentgenol. 2010; 194(6):1568–1574 [10] Chhabra A, Thakkar RS, Andreisek G, et al. Anatomic MR imaging and functional diffusion tensor imaging of peripheral nerve tumors and tumorlike conditions. AJNR Am J Neuroradiol. 2013; 34(4):802–807

Ultrasound in Peripheral Nerve Surgery

8 Ultrasound in Peripheral Nerve Surgery Maria Teresa Pedro and Ralph W. König Abstract High-frequency ultrasound (HFU) has become an indispensable diagnostic tool in peripheral nerve surgery. Progress in technical equipment made it possible to depict peripheral nerves in high resolution, up to 500 µm. Especially concerning “failed surgeries” of compression neuropathies, HFU is able to capture morphological pathologies (scars, nerve kinking, partial neuroma, cysts). It provides essential information for the medical evaluation of recurrent surgery. HFU has also changed the time frame in treating traumatic nerve lesions since loss of continuity of damaged nerves are depicted right away. During reconstructive nerve surgery, intraoperative HFU has a direct impact on the surgeon’s decision, since tissue differentiation and pathologies becomes immediately visible. Nerve surgeons can take a look into the affected nerve and decide which microsurgical technique could be optimally applied. For the diagnostic evaluation of peripheral nerve tumors, magnetic resonance imaging (MRI) is the gold standard, but nevertheless misinterpretations are frequent, in particular, concerning rare nerve tumors. Multimodal ultrasound (power Doppler, superb microvascular imaging, contrast-enhanced ultrasound) offers additional morphological knowledge. However, further expertise and studies are necessary to evaluate these results first.

neurologists or nerve surgeons a readily available and deeper insight into the nerve, including its surrounding soft tissue.

8.2 How to Start (Basic Principles) One of the basic principles of US is the fact that high frequency (17–15 MHz; ▶ Fig. 8.1) leads to high resolution but low tissue penetration. Therefore, the visualization of superficial peripheral nerves is decently feasible. However, for the presentation of deeper lying nerves (for instance, sciatic nerve), the application of lower frequency transducers (10–12 MHz) becomes necessary. To start examination, the authors would recommend obtaining transverse US images. At the beginning, it is difficult to distinguish nerves from tendons (i.e., median nerve at the wrist) (▶ Fig. 8.2). However, when the US probe is slightly tilted, nerves will not change their shape, while tendons will become either hyperechoic or hypoechoic. The typical transverse picture of a healthy peripheral nerve is similar to a honeycomb, meaning that single fascicles are hypoechoic, those are surrounded by hyperechoic membranes of the perineural sheath. The whole nerve is coated by epineural tissue, which is also

Keywords: high-frequency ultrasound, compression neuropathy, traumatic nerve lesions, peripheral nerve tumor, multimodal ultrasound

8.1 Introduction Regular application of ultrasound (US) as a medical diagnostic tool goes back to the 1960s. However, it was not earlier than 1988 when Fornage1 first described the ultrasonographic visualization of peripheral nerves. Nowadays, as a consequence of an ongoing combined development of US transducers and image processing software (i.e. compound imaging, tissue harmonic imaging), high-frequency/high-resolution ultrasound (HFU/ HRU) has become a highly versatile diagnostic tool for the diagnostic evaluation of peripheral nerve problems in general.2 In particular, its intraoperative implementation provides valuable additional information for surgery of peripheral nerve trauma and tumors.3 Nowadays, US, besides the medical history, a complete clinical examination, and electrophysiological studies, can be considered as a valuable standard in the diagnosis of peripheral nerve pathologies. US, rather than magnetic resonance neurography (MRN), is capable of offering

Fig. 8.1 The 15-MHz transducer, called ice hockey stick (left-hand side); the 17 MHz transducer (right-hand side).

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Fig. 8.2 Transversal plane of the median nerve. RCFT, flexor tendon of the M. carpi radialis muscle; RF, retinaculum flexorum.

hyperechoic. Note that the real anatomical existing number of fascicles is usually much higher. It does not correspond to the number of fascicles depicted by HRU. The investigator should start US at an anatomical relevant area, where the nerve is lying superficially or nearby a typical bone structure, for example: ● Median nerve: carpal tunnel/wrist. ● Ulnar nerve: cubital tunnel/elbow. ● Radial nerve: humerus/middle upper arm. ● Peroneal nerve: fibula/knee joint. ● Tibial nerve: tarsal tunnel/medial malleolus. HRU should be a dynamic examination. It is important to examine the whole or at least a long trail of the nerve, sometimes even to compare the healthy side of the body with the lesioned one. By slightly increasing the pressure of the transducer, the investigator can even provoke a Tinel sign; or by asking the patient to flex and stretch the elbow, a subluxation or complete luxation of the ulnar nerve can be seen by HRU. Last but not least, one should also evaluate the structure of the different surrounding tissues, i.e., muscles, bones, and tendons, especially in trauma.

Note: High frequency means less tissue penetration. Start examination in transverse plane on an anatomical relevant area. HRU is a dynamic examination, keep moving.

8.3 Compression Neuropathies 8.3.1 Compression Neuropathies of the Upper Limb Bearing in mind that the carpal and the cubital tunnel syndrome (CTS and CUTS) are the most frequent entrapment syndromes, clinical examination and electrophysi-

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ology are indispensable and usually sufficient. However, if the visualization of the affected nerve becomes necessary, for instance, in cases of suspected recurrence, HRU is the suitable diagnostic tool to provide additional morphological information. Historically, the first HRU studies were dealing with CTS and CUTS. Already in 1991, only 3 years after Fornage first described a neural structure in US, Buchberger and his colleagues4 published their findings in patients with CTS. The study group pointed out that the median nerve appeared enlarged before entering the entrapment zone. One possible pathological explanation for the development of this swelling is postulated to be caused by compression of the vasa nervorum. As a result, an ischemia and venous congestion may occur, which in turn leads to neural edema.5 This suspicious surface area has to be compared to the more proximal or distal parts of the nerve. If the ratio is 2:1, one can speak of a pseudoneuroma (▶ Fig. 8.3a–c). Kele et al6 examined 110 median nerves of patients suffering from CTS via US. A cross-sectional area (CSA) of > 0.11 cm2 was considered to be highly predictive for the diagnosis of CTS (sensitivity 89.1% and specificity 98%). Therefore, diagnostic accuracy of HRU is comparable to electrophysiological studies in CTS.7 Another group reported that by combining HRU with nerve conduction studies, sensitivity and specificity increased to 98 and 91%, respectively, in patients with CUTS.8 For all other rare entrapment syndromes of the upper limb, such as, supinator syndrome, thoracic outlet syndrome, Guyon’s syndrome, etc., HRU is even more essential, and it provides helpful additional information (existence of cysts, lipoma, cervical ribs) since electrophysiology examination is often challenging in those cases.

8.3.2 Compression Neuropathies of the Lower Limb Entrapment syndromes of the lower limb are quite rare, but peroneal and tibial nerves in particular can be compressed by extraneural or intraneural cysts. Therefore, for surgical planning, HRU is extremely helpful (▶ Fig. 8.4).9 Even Morton’s neuroma of the interdigital plantar nerve can be visualized as a spherical swelling. Also, a hypoechoic enlargement of the lateral femoral cutaneous nerve (LFCN) is a secure sign of entrapment at the anterior superior iliac spine in patients with meralgia paresthetica, but since those patients are often obese, an examination via HRU is in general difficult.10 Infiltrations of the LFCN as a nonsurgical treatment option are firmly performed by US guidance.11

8.3.3 Recurrent Compression Neuropathies HRU is of great importance and indispensable in cases of recurrent entrapment syndromes. Before a surgical redo

Ultrasound in Peripheral Nerve Surgery

Fig. 8.3 Transversal plane of the ulnar nerve of a patient suffering of CUTS. (a) At the level of the epicondylus medialis, showing a hypoechoic enlargement of 0.146 cm2. (b) At the middle of the upper arm with a CSA of 0.068 cm2. (c) At the middle of the forearm next to the ulnar artery with a CSA of 0.067 cm2.

Fig. 8.4 Tibial nerve next to an extraneural cyst at the malleolus medialis.

surgery is decided, the visualization of new postoperative morphological changes, such as, scars, epineural fibrosis (▶ Fig. 8.5), partial neuromas, cysts, nerve kinking after transposition, etc. have to be depicted and evaluated. Also the CSA of the pseudoneuroma before and after surgery can be compared. Tas et al12 described a decrease in CSA

Fig. 8.5 Median nerve of a symptomatic patient, who was previously operated for CTS, showing epineural fibrosis.

after CTS surgery in asymptomatic patients, postulating that after decompression the swelling of the affected median nerve is reversible.

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Note: Pseudoneuroma means CSA 2:1. HRU is above all useful for “failed surgery” and rare compression neuropathies of the upper or lower limb (e.g., detection of cysts).

8.4 Trauma 8.4.1 Preoperative HRU HRU in the recent past had a significant impact on peripheral nerve surgery, especially in peripheral nerve trauma. Besides medical history, clinical examination, and electrophysiological studies, HRU provides morphological information of the lesioned nerve segment and its surrounding tissues (bone, tendons, muscles). Before, clinical and electrodiagnostic examination were the only tools to evaluate patients. In some instances, MRN was performed, but in the majority of cases, due to the presence of osteosynthetic material, nerve structures could hardly be recognized. Now, via HRU, the injured area can be examined as a whole. Tendons, muscles, bones, osteosynthetic material, hematoma, and nerves become visible.13 Since morphological nerve damage is visualized and registered by HRU, this diagnostic tool has obtained an outstanding role especially in regard to iatrogenic nerve lesions14 (▶ Fig. 8.6a,b). It is now possible to distinguish between direct (sharp transection) and indirect nerve lesions (compression due to scar tissue, osteosynthetic material, hematoma).15 The cause is determined as well as the exact localization of the nerve damage is registered. This enables the physicians to make a proper decision whether to operate or to wait for reinnervation.16 Furthermore, surgical approach and skin incision can be precisely targeted (▶ Fig. 8.7a–c). In the case of a sharp transection with discontinuity of the nerve, HRU depicts neuroma as large hypoechoic enlarged stumps (▶ Fig. 8.8). The distance between them

can be measured, so that the needed length of nerve grafting can be determined and surgery can accordingly be performed at an early stage. Indirect nerve lesions may lead to incomplete neurological deficits, which makes it often more difficult to find the right decision whether to operate or not. Morphological findings in HRU do help to understand the pathogenic mechanism and to better evaluate nerve’s damage. The affected nerve may lose its fascicular structure and become swollen and hypoechoic, epineural tissue may be fibrotic, or scar tissue may lead to compression (▶ Fig. 8.9).

8.4.2 Intraoperative HRU High-frequencies transducers (e.g., 17 MHz) in HRU achieve a spatial resolution of up to 500 µm, but tissue penetration is restricted to few centimeters. Especially in enlarged extremities due to lymphedema or hematoma, the tissue differentiation may become difficult. Lee was the first who used HRU intraoperatively to localize directly a neuroma in situ.17 To exploit maximal spatial resolution, our study group evaluated HRU findings in traumatic lesioned nerve segments in an intraoperative setting (iHRU) in 2011. After external neurolysis, the injured nerve segment was embedded in sterile US gel cushions and the affected part of the nerve was visualized via a 15- or 17-MHz transducer (▶ Fig. 8.10a,b). These findings were compared to the results of compound nerve action potentials (cNAP) and, in the case of the neuroma being resected, also compared to histopathology. Morphological alterations correlated well with intraoperative recording of cNAP and therefore with functionality.3 Focusing on neuroma-in-continuity surgical management, especially in cases with partial neurological regeneration, becomes challenging. Even after microsurgical exposure, neuromas involving the complete internal structure are hard to be distinguished from partial neuromas. Frequently, different morphological alterations merge into one another and thus the complete extent of

Fig. 8.6 (a) Preoperative ultrasound revealing the exact location where the radial nerve slides under the screw. (b) Intraoperative picture of osteosynthesis after a fracture of the left humerus; radial nerve is lying under a screw.

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Fig. 8.7 Patient with humeral fracture after osteosynthesis with loss of hand extension. (a) Transversal plane of radial nerve lying on osteosynthetic material. (b) Transversal plane of the radial nerve slipping over a screw as over a hypomochlion. (c) Through preoperative HRU detection of the location of damage and planning the further incision (red lines and red arrows, former scars, suspected location of nerve damage at the elbow level; black line, new incision).

In summary, pre- and intraoperative HRU merge into one another. Both have changed peripheral nerve surgery, especially in traumatic nerve lesions. They are complementary diagnostic tools to electrodiagnosis and clinical examination. All of them together enable us to achieve important knowledge about morphology and function of an affected nerve. The implementation of both techniques is shown in the trauma flowchart (▶ Fig. 8.11).

Note: Preoperative HRU locates and depicts nerve damage at an early stage. Intraoperative HRU helps determine the best microsurgical technique that should be employed in each case. Fig. 8.8 Longitudinal scan of a dissected sciatic nerve (stump) in a child of 10 years.

8.5 Tumors lesion gets exposed. Via iHRU, the inner architecture of the affected nerve segment becomes visible, and by this means, it has a direct influence on the surgical procedure (▶ Table 8.1). Nowadays, HRU is a fixed component in the operating room during peripheral nerve surgery.

Peripheral nerve tumors (PNTs), especially schwannoma and neurofibroma, each account for 5% of all soft-tissue tumors. Magnetic resonance imaging (MRI) as a diagnostic tool has been the gold standard until now. However, nevertheless, misinterpretations, especially concerning rare peripheral nerve tumors, are frequent.18 A secure differentiation between benign and malignant

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Fig. 8.9 Longitudinal scan of a median nerve being compressed from above by a scar tissue.

Fig. 8.10 Intraoperative HRU. (a) Sterile-draped 15-MHz probe, while the ulnar nerve is embedded in a sterile gel cushion. (b) IHRU picture of a peroneal nerve via 17 MHz, honeycomb structure clearly visible.

peripheral nerve sheath tumors (BPNST and MPNST), despite advances in MRI sequences, containing MR enhanced neurography or diffusion tensor imaging, and 18F-fluorodeoxyglucose positron emission tomography (FDG PET), is not yet possible.19,20 Nowadays, HRU has become a further additional promising diagnostic medium, but concerning PNTs, experience is still limited and until now with only a few published studies.21,22 Our study group first started to perform iHRU in PNTs in 2010. The first step was to obtain maximal morphological knowledge, by using high-frequency transducers (17 MHz) to gain a resolution of up to 500 µm. In summary, due to US findings, three different groups (A–C) were described. In the first group, the examined nerves revealed enlarged hypoechoic fascicles. Their inner architecture per se was definable (▶ Fig. 8.12). After biopsy of one conspicuous fascicle, pathological examination revealed very rare tumor entities, such as amyloidoma and perineurioma, or tumorlike lesions, such as multifocal acquired demyelinating sensory and motor (MADSAM) neuropathy. The second group consisted of one case with a giant sciatic nerve, showing in iHRU huge, dense, enlarged isoechoic fascicles. In 2015, only one case revealed this

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impressive US result. Histopathology defined it as a B-cell lymphoma. Until now, a second case of lymphoma could be examined and the same criteria were depicted (▶ Fig. 8.13). The third group came out to be grossly inhomogeneous in their pathological examinations, although iHRU revealed no large differences within this group. The affected nerves showed large hypoechoic tumor masses and no affected fascicles were displaced or hardly distinguishable. Cysts or even areas with hyperechoic solid parts were seen. Ancient benign schwannomas, as well as MPNST, were hardly distinguishable (▶ Fig. 8.14). However, depending on pathological results, surgical management differs widely, ranging from complete enucleation of the tumor mass under strict neurological preservation (e.g., schwannoma) to biopsy of one fascicle (e.g. perineurioma) and complete resection of the tumorous nerve taking into account a loss of function (e.g., MPNST). To date, it is still a long-awaited requirement to improve diagnostic accuracy within preoperative classification. Since tissue penetration is limited in HRU, further US modalities such as contrast-enhanced US, power Doppler, and superb microvascular imaging are being used for possible PNT differentiation (▶ Fig. 8.15a–c) in ongoing research.21,23

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Ultrasound in Peripheral Nerve Surgery Table 8.1 Trauma classification via iHRU Type I

Normal

Type II

Epineural fibrosis

Epineurotomy

Type III

Intraneural fibrosis

Epineurotomy and intraneural dissection

Type IV

Partial neuroma

Split repair

Type V

Complete neuroma (in continuity)

Nerve grafting

Trauma

Fig. 8.11 Trauma flowchart. In case of traumatic nerve lesions, HRU should be performed as soon as possible to depict nerve’s continuity. Depending on nerve’s regeneration, early-staged surgery should be carried out. iHRU enables visualization of nerve’s damage. Together with nerve action potentials, it helps determination of nerve’s lesion in a trauma classification (I–V). HRU, high-resolution ultrasound; iHRU, intraoperative high-resolution ultrasound; NAP, nerve action potential.

HRU

Lost Continuity

Continuity

Follow up

Surgery − Regeneration

+ Regeneration

Follow up Ongoing regeneration

Time

Stagnant regeneration

Surgery

3 months iHRU

I

II

NAP

III

IV

V

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Fig. 8.12 Transversal plane of an ulnar nerve, showing hypoechoic enlarged fascicles next to smaller regular ones. Classical picture of an amyloidoma.

Fig. 8.13 Transversal plane of sciatic nerve of a B-cell lymphoma. Fascicles are enlarged, dense, isoechoic; the inner architecture is distinguishable.

Fig. 8.14 Longitudinal HRU picture of a schwannoma of a median nerve. Hypoechoic cystic tumor displaces no affected fascicles. No fascicles distinguishable in the tumor mass.

Fig. 8.15 Multimodal HRU. (a) Preoperative ultrasound of a schwannoma of a sciatic nerve (left side). Same picture examined via superb microvascular imaging showing a positive perfusion on the upper part of the tumor (right side). (b) Intraoperative contrast-enhanced ultrasound of those two schwannoma of the right tight, directly after intravenous application intravenous application, showing no inner enhancement. (c) Same patient after 20 seconds, revealing a homogenous complete enhancement.

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Note: MRI is the gold standard for PNT.

[12]

Ongoing research for multimodal HRU in PNT. [13]

References [1] Fornage BD. Peripheral nerves of the extremities: imaging with US. Radiology. 1988; 167(1):179–182 [2] Beekman R, Visser LH. High-resolution sonography of the peripheral nervous system – a review of the literature. Eur J Neurol. 2004; 11 (5):305–314 [3] Koenig RW, Schmidt TE, Heinen CP, et al. Intraoperative highresolution ultrasound: a new technique in the management of peripheral nerve disorders. J Neurosurg. 2011; 114(2):514–521 [4] Buchberger W, Schön G, Strasser K, Jungwirth W. High-resolution ultrasonography of the carpal tunnel. J Ultrasound Med. 1991; 10 (10):531–537 [5] Bodner G. Nerve compression syndromes. In: Peer S, Bodner G, eds. High-Resolution Sonography of the Peripheral Nervous System. Berlin: Springer-Verlag; 2008:71–122 [6] Kele H, Verheggen R, Bittermann HJ, Reimers CD. The potential value of ultrasonography in the evaluation of carpal tunnel syndrome. Neurology. 2003; 61(3):389–391 [7] American Association of Electrodiagnostic Medicine, American Academy of Neurology, and American Academy of Physical Medicine and Rehabilitation. Practice parameter for electrodiagnostic studies in carpal tunnel syndrome: summary statement. Muscle Nerve. 2002; 25(6):918–922 [8] Beekman R, Van Der Plas JP, Uitdehaag BM, Schellens RL, Visser LH. Clinical, electrodiagnostic, and sonographic studies in ulnar neuropathy at the elbow. Muscle Nerve. 2004; 30(2):202–208 [9] Visser LH. High-resolution sonography of the common peroneal nerve: detection of intraneural ganglia. Neurology. 2006; 67(8): 1473–1475 [10] Onat SS, Ata AM, Ozcakar L. Ultrasound-guided diagnosis and treatment of meralgia paresthetica. Pain Physician. 2016; 19(4):E667– E669 [11] Tagliafico A, Serafini G, Lacelli F, Perrone N, Valsania V, Martinoli C. Ultrasound-guided treatment of meralgia paresthetica (lateral femoral cutaneous neuropathy): technical description and results of treat-

[14]

[15]

[16]

[17]

[18]

[19]

[20]

[21]

[22]

[23]

ment in 20 consecutive patients. J Ultrasound Med. 2011; 30(10): 1341–1346 Tas S, Staub F, Dombert T, et al. Sonographic short-term follow-up after surgical decompression of the median nerve at the carpal tunnel: a single-center prospective observational study. Neurosurg Focus. 2015; 39(3):E6 Kele H. Sonographie der peripheren Nerven. In: Reimers CD, Gaulrapp H, Kele H, eds. Sonographie der Muskeln, Sehnen und Nerven. Köln: Deutscher Ärzteverlag; 2004:271–280 Antoniadis G, Kretschmer T, Pedro MT, König RW, Heinen CPG, Richter HP. Iatrogenic nerve injuries: prevalence, diagnosis and treatment. Dtsch Arztebl Int. 2014; 111(16):273–279 Gruber H. Traumatic nerve lesions. In: Peer S, Bodner G, eds. Highresolution sonography of the peripheral nervous system. Berlin: Springer-Verlag; 2008:123–149 Gruber H, Glodny B, Galiano K, et al. High-resolution ultrasound of the supraclavicular brachial plexus–can it improve therapeutic decisions in patients with plexus trauma? Eur Radiol. 2007; 17(6): 1611–1620 Lee FC, Singh H, Nazarian LN, Ratliff JK. High-resolution ultrasonography in the diagnosis and intraoperative management of peripheral nerve lesions. J Neurosurg. 2011; 114(1):206–211 Kransdorf MJ, Murphey MD. Radiologic evaluation of soft-tissue masses: a current perspective. AJR Am J Roentgenol. 2000; 175(3): 575–587 Koenig RW, Coburger J, Pedro MT. Intraoperative Findings in Peripheral Nerve Pathologies. In: Prada F, Solbiati L, Martegani A, DiMeco F, eds. Intraoperative Ultrasound (IOUS) in Neurosurgery: From Standard B-mode to Elastosonography. Heidelberg: Springer; 2016:71–79 Ferner RE, Golding JF, Smith M, et al. [18F]2-fluoro-2-deoxy-Dglucose positron emission tomography (FDG PET) as a diagnostic tool for neurofibromatosis 1 (NF1) associated malignant peripheral nerve sheath tumours (MPNSTs): a long-term clinical study. Ann Oncol. 2008; 19(2):390–394 Pedro MT, Antoniadis G, Scheuerle A, Pham M, Wirtz CR, Koenig RW. Intraoperative high-resolution ultrasound and contrast-enhanced ultrasound of peripheral nerve tumors and tumorlike lesions. Neurosurg Focus. 2015; 39(3):E5 Capek S, Hébert-Blouin MN, Puffer RC, et al. Tumefactive appearance of peripheral nerve involvement in hematologic malignancies: a new imaging association. Skeletal Radiol. 2015; 44(7):1001–1009 Loizides A, Peer S, Plaikner M, Djurdjevic T, Gruber H. Perfusion pattern of musculoskeletal masses using contrast-enhanced ultrasound: a helpful tool for characterisation? Eur Radiol. 2012; 22(8): 1803–1811

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9 Surgical Repair of Nerve Lesions: Neurolysis and Neurorrhaphy with Grafts or Tubes Sudheesh Ramachandran and Rajiv Midha Abstract Peripheral nerve injuries are devastating, and management is complex. Microsurgical repair forms the mainstay of treatment, which includes direct repair, nerve grafting, nerve transfers, and nerve tubes. This chapter elaborates on the technical nuances of surgical repair and critically analyses the evidence for various surgical modalities. Advances in tissue engineering provide considerable promise in the future as alternative/adjunct to existing management strategies. Keywords: nerve surgery, nerve injury, neurorrhaphy, conduits, functional outcome

9.1 Introduction Peripheral nerve injuries (PNIs) are disturbingly frequent, affecting around 2.8% of the trauma population.1 Most of them occur as a consequence of motor vehicle accidents or injuries at home/workplace, resulting in substantial and often permanent morbidity and disability. The strict enforcement of the use of seat belts and crash helmets in many countries has significantly reduced the mortality; however, a simultaneous increase in the incidence of PNI has been an undesirable offshoot.2 Most of our understanding of PNIs come from the First and Second World Wars’ experience in the 20th century. However, the concepts of nerve repair and regeneration were described as early as 7th century by Paul of Aegina. In 1850, Augustus Waller threw some light on the pathophysiology of nerve injury by describing anterograde myelin and axonal degeneration.3 The first successful nerve regeneration after surgical repair was reported by Cruikshank in 1795. Primary epineurial suturing and nerve suturing techniques were described by Heuter in 1871 and Mikulicz in 1882, respectively.4 Albert in 1876 pioneered nerve grafting procedures to bridge the gaps, and Loebke in 1884 elaborated on bone-shortening procedures to reduce nerve tension during repair. Many of these techniques were further refined in the 20th century, resulting in tremendous advances in the realm of PNI management. To date, the clinical recovery following PNI is incomplete. The timing of repair, severity and extent of injury, fascicular anatomy and realignment, mechanism of injury, patient age and comorbidities, and early psychological stress are some of the few factors known to impact outcome. The technical skill of the surgeon, as well as the surgical technique used, is also one of the key influences on functional recovery.5,6,7 Various surgical techniques for

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peripheral nerve repair have originated from the information gleaned from numerous animal models. This chapter attempts to provide an overview of the surgical techniques currently used for peripheral nerve repair with special emphasis on grafting, tubulization techniques, and recent advances such as cell-based supportive therapies.

9.2 Evaluation and Approach A thorough understanding of the nerve injury is imperative following a clinical diagnosis. This is because subsequent management strategies are strongly based on the type of insult sustained. We now know that a regenerative cascade of events begins immediately after a nerve injury. When the neural elements are disrupted, each axon forms several filopodia, which steadily and slowly advance toward the distal nerve stump in an attempt to bridge the gap. The recovery time is dependent on the regeneration rate, which averages 1 mm/day.8 When endoneurial tubes are intact (pure axonotmesis injury), there is an excellent chance of an uninhibited regenerative process culminating in satisfactory reinnervation. However, when there is a partial or complete internal rupture, the advancing and regenerating axons become tangled in disrupted internal architecture and scar tissue, often resulting in a neuroma-in-continuity. The recovery in axonotmesis largely depends on the ability of the regenerating axons to bridge the gap and establish functional continuity without being impeded by the scarring process. Neuropraxia recovers spontaneously, and neurotmesis requires surgery. In complex clinical scenarios, multiple levels and types of injuries can coexist, giving rise to a therapeutic challenge. The timing of intervention for nerve repair is largely dependent on the type of nerve injury sustained, condition of the wound, and vascular supply of the nerve bed.9,10 Early surgery is indicated when there is a laceration with concurrent neurological deficit, where the possibility of a nerve transection is quite high. These types of injuries are typically caused by knife wounds, lacerations from glass, or razor blade. Spinner and Kline recommended action with end-to-end repair within 72 hours in such scenarios of sharp lacerating injuries.10 On the other hand, a bluntly transected nerve is best managed at 3 to 4 weeks so that the neuromas and scarred portions of the nerve are more obvious at the time of repair. These portions are resected and then the nerve is reapproximated with or without grafts. If such an injury is identified during an early exploration, the contused and ragged

Surgical Repair of Nerve Lesions: Neurolysis and Neurorrhaphy with Grafts/Tubes ends of the nerve are tacked to the adjacent fascial or muscular planes to minimize retraction and to aid an elective end-to-end repair. Delayed exploration with possible repair is indicated in traction injuries, partial nerve defects, infected wounds, and poor patient’s status. These are typically performed at 3 to 4 months to allow time for spontaneous recovery or complete evaluation of the nerve function with serial clinical and electrophysiological assessments.11 When there is no nerve tissue loss and ends can be approximated without undue tension, an end-to-end repair should be attempted. In case of injuries resulting in defects less than 3 cm, autografting or tubulization techniques are attempted, whereas in larger defects nerve grafting with autografts (rarely allografts) is recommended.12 Nerve transfer repairs are especially indicated in brachial plexus injuries, proximal intraforaminal injuries, spinal cord root avulsion injuries, and in cases with delayed presentation and redo brachial plexus injuries. They are covered in detail in other chapters.

9.3 General Principles of Nerve Repair The general principle of nerve repair is based on the following: a thorough knowledge of the gross anatomy of the limbs and peripheral nerves; clinical evaluation including a detailed history and a complete physical examination; electrophysiological studies; and relevant imaging. Following determination of the type of nerve injury and formulation of a surgical plan, patients should be adequately informed about the surgical procedure and expected outcome. Proper positioning of the limb, padding of pressure points and draping to allow full exposure of the nerve, and assessment of distal muscle function are crucial. Microsurgical techniques should be used for nerve repair, including the use of microsurgical instruments and an operating microscope or magnifying loupes. A short-acting muscle relaxant is typically used because intraoperative stimulation may be required to test for muscle contraction from nerve stimulation during surgery. The injured nerve should be exposed well proximal and distal to injury, in addition to the injury zone, in a thorough and meticulous manner. As mentioned earlier, the damaged nerve must be resected until a normal fascicular pattern is observed, as the repair will fail unless healthy tissues are approximated. Bleeding occurring from the sectioned surface of the stump can be controlled by using a piece of Gelfoam or muscle, whereas arterial bleeding is controlled using fine-tipped bipolar electrocautery visualized using a microscope. To summarize, a technically perfect nerve repair must consist of four parts: (1) complete debridement to healthy nerve tissue, (2) nerve approximation without tension, (3) end-on alignment of fascicles, and (4) atraumatic and secure mechanical coaptation of nerve ends.13

9.4 Neurolysis Neurolysis has paramount importance in surgical repair of nerve injuries. In this context, the authors are referring to external neurolysis which essentially involves dissection outside the epineurium to release it from points of compression or tethering due to scarring, particularly in cases of delayed exploration. This will enable sufficient mobilization of the nerve, which is a critical step prior to any form of coaptation. Sufficient exposure of the injured segment, both proximal and distal, is mandatory prior to neurolysis. Dissection is preferably performed toward the injury site from a normal segment of the nerve. Adequate neurolysis is believed to act in concert with a healthy vascularized bed to improve nerve vascularity, thus enhancing the results of nerve repair.

9.5 Direct Repair This type of repair is attempted when the severed ends can be approximated without tension and when the gap is minimal. A better outcome is observed when the nerves are exclusively motor or sensory and also when the amount of intraneural connective tissue is relatively less.14 Several technical principles should be strictly followed in every case of direct nerve repair. The importance of adequate visualization of relevant neural, vascular, and musculoskeletal structures during surgical exposure cannot be overemphasized. External neurolysis should be performed without causing neural damage, as mentioned earlier. The repair should be achieved with minimal tension. Numerous authors have reported that excessive tension is detrimental to nerve vascularity and functional outcome.15,16,17 Due to the elastic nature of nerves, some degree of tension is expected in every repair. The amount of acceptable tension is, however, not properly defined. De Medinaceli and colleagues reported that failure to hold an end-to-end repair with single 9–0 suture is a sign of excessive tension.18 Whenever there is excess tension at repair site, nerve grafting is preferred.

9.5.1 End-to-End Repair This is one of the most widely used techniques for direct nerve repair. Numerous authors have described different techniques to achieve an end-to-end repair. ● Epineural repair: This technique is commonly used when there is a sharp injury to the proximal portion of the nerves without nerve loss and also in cases of partial injuries with good fascicle alignment. It is highly effective for monofascicular and diffusely grouped polyfascicular nerve repairs.19 The primary goal is to achieve continuity of the nerve stumps without tension, along with proper alignment of the fascicles. The correct fascicle positioning is confirmed by aligning the longitudinal blood vessels in the epineurium.20

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The coaptation is performed using 8–0 or 9–0 nylon sutures under magnification. To begin with, two orienting epineural sutures are taken 180 degrees apart to avoid rotational displacement during mobilization. It is important to avoid injury to the perineurium; however, a small amount of internal epineurium should be taken in the suture for appropriate fascicular coaptation. Following placement of the first suture, its tail is held using an instrument such as a fine hemostat, to facilitate the rotation of the nerve for coaptation on the opposite side. Additional interrupted sutures may be placed 90 degrees away from the initial sutures for added strength. Minimal number of sutures (usually four) for accurate coaptation are preferred to reduce the scarring process.19,20,21 Many surgeons will augment repair using fibrin glue to further minimize the number of microsutures. Grouped fascicular repair: This technique is used in mixed motor and sensory nerves where the fascicles serving specific functions are well formed and easily recognized (e.g., ulnar nerve at wrist, radial nerve above elbow before giving rise to posterior interosseous nerve, and superficial sensory radial nerve). Contrary to epineural repair, grouped fascicular repair is a more accurate but technically demanding method of coaptation. Resection of the damaged nerve ends is imperative to precisely delineate fascicular anatomy. The external epineurium is reflected back to organize the fascicles. Fascicular coaptation is achieved with placement of sutures in the interfascicular epineurium and perineurium with 8–0 to 10–0 nylon sutures. As mentioned earlier, not more than two to three sutures per group are preferred to reduce scarring.22 It is imperative to keep the tension at the repair site to the utmost minimum as the interfascicular epineurium is not as tough as the external epineurium. Excessive tension could also contribute to malalignment of the fascicles and increased scarring. Fascicular repair: This technique is used in a clean lacerating injury, where the motor and sensory fascicles can be easily identified, in the partially damaged nerve. This involves coaptation of the individual fascicles for optimal alignment, and hence this is a more technically difficult repair. Following dissection of the interfascicular epineurium, the fascicles are identified using the spiral bands of Fontana in the perineurium. These bands are instrumental in maintaining proper fascicular structure and elastic properties of the perineurium.23 If there is protrusion of the intrafascicular material in the perineural edge, it should be carefully trimmed prior to suturing. The external epineurium is stripped for lengths approximately twice the cross-sectional diameter of the nerve. Care should be taken to preserve the surrounding paraneurial tissue as it contains blood vessels, and this can be used to cover the repair site. Fascicular coaptation is achieved under high

Fig. 9.1 Intraoperative photograph showing matching fascicles during nerve repair to enhance functional recovery.

magnification by placement of sutures, usually two to three 10–0 or 11–0 nylon sutures 120 to 180 degrees apart, in the perineurium. It is important to avoid injury to the endoneurium during suture placement. Excessive tension produces lateral protrusion of the interfascicular contents and disappearance of spiral bands of Fontana.23 Should this occur during repair, the surgeon should reassess the tension at the repair site. Unlike epineural repair, both grouped fascicular and fascicular coaptation provides better alignment of the fascicles, thereby reducing misdirection of axons (▶ Fig. 9.1). Nevertheless, the additional dissection and increased sutures involved in this technique could potentially lead to increased scarring and disruption of blood supply.20,21 Studies have found no significant difference in functional outcome when individual or grouped fascicular repair techniques were used compared to simple epineural repair.24,25,26

9.5.2 End-to-Side Repair End-to-side or terminolateral neurorrhaphy involves connecting the distal stump of a transected nerve, referred to as the acceptor nerve, to the side of an intact adjacent or neighboring nerve, referred to as the donor nerve. This technique is particularly useful in sensory nerve transfers and facial nerve reanimation. The advantage of this technique is that there is no length limitation and also that there is recovery of injured nerve without compromising the function of donor nerve. The mechanism of functional recovery in the acceptor nerve is not entirely clear. Rovak et al opined that nerve fibers invade from the donor axons damaged during nerve preparation for coaptation.27 Zhang et al, based on double-labelling studies, found that collateral sprouting occurs from the undamaged donor nerve.28 Since its introduction by Viterbo et al in 1992, many studies on end-to-side repair have shown that outcomes range from poor to modest but rarely excellent. However,

Surgical Repair of Nerve Lesions: Neurolysis and Neurorrhaphy with Grafts/Tubes Mennen demonstrated good sensory or motor recovery in a large cohort of 50 patients with various peripheral nerve injuries. Excellent results were seen in facial reanimation procedures, where end-to-side facial to hypoglossal nerve anastomosis was performed with an interpositional jump graft.29,30 This technique was also used with good results for the repair of dysesthesia after removal of the sural nerve, as well as to connect the phrenic nerve to the brachial plexus. End-to-side repair has been used to link the nerve gap after ulnar nerve injury, with median nerve as donor nerve, in addition to phrenic and spinal accessory nerve neurotization, and coaptations of palmar digital nerves and select cases of brachial plexus trauma. Viterbo and Ripari reported good outcome when they tried to restore lower limb sensation in paraplegics, thereby reducing the chances of formation of pressure sores, by linking the intercostal nerves above the site of injury and sciatic nerve in an end-toside fashion using sural nerve graft.31 However, Bertelli and Ghizoni reported poor results using this technique to repair radial nerve, C5 or C6 root rupture, and common peroneal nerve lesion.32 It now appears that end-to-side repair would be ideal only in specific and limited clinical scenarios. With microscopic magnification, following adequate mobilization of the recipient nerve, a small epineural window is created matching the size of recipient nerve end. As with other techniques, any terminal neuromas on the recipient nerve stump should be excised and healthy fascicles be properly visualized prior to coaptation, which is achieved with two to three microsutures placed 180 degrees apart through the epineurium.

9.6 Nerve Grafting Nerve grafting is recommended whenever a direct repair is likely to result in excessive tension at the repair site.33 In the past, nerve stretching, bone shortening, extremity positioning, and stump mobilization were some of the procedures used to shorten the bridging gaps, most of which are now obsolete. In current clinical practice, the ideal choice to circumvent such a scenario is to use a nerve graft. Tubulization techniques may be used for smaller gaps (< 3 cm), but larger defects need nerve grafts.34,35 Split repair is a technique which is used when there is partial injury to the nerves with damage to only a portion of the fascicles with relative sparing of the rest. In these conditions, the healthy fascicles are dissected from the injured ones and nerve action potential (NAP) recording is used. Usually, the NAP is recordable from the healthy fascicles and absent in the injured ones. The injured fascicles are then resected till normal fascicular anatomy is visualized and then coapted with a graft using an interfascicular technique.10

9.6.1 Autografts Although many options exist for bridging the gap, an autograft is used whenever possible. Several technical principles influence the success of nerve grafting. The proximal and distal nerve stumps are meticulously inspected, and any damaged portion or neuroma is resected. The epineurium is cut in a longitudinal fashion, and the fascicles are closely inspected under magnification. All fibrotic tissue amid these fascicles is removed using sharp dissection. The surgeon must make sure that the proximal and distal nerve stumps are tension-free even when the extremity is moved along its full range. The harvested graft should be kept moist and handled carefully to prevent injury. To avoid fascicular malalignment, the interfascicular tissue is retracted and the fascicles are defined in groups akin to fingers. The sensory or motor components should be matched as accurately as possible (▶ Fig. 9.2). However, this is practically feasible in only distal nerves. The number and length of the graft depend on the cross-sectional area and the bridging gap, respectively. In general, the graft length should be 10 to 20% longer than the gap, to provide room for retraction and shrinkage. The cross-sectional area of the graft is preferably smaller than the recipient nerve. Smaller diameter grafts are associated with better results as larger grafts have compromised vascularity in their core, thus leading to necrosis and greater scar formation. The smalldiameter nerves obtain nourishment from their surface.36 Owing to this, it would be ideal to use multiple small diameter nerves for grafting major nerves (▶ Fig. 9.3). Sutures are taken through the epineurium in the host stump 180 degrees apart, to the interfascicular epineurium and perineurium of the isolated fascicles, spreading the cross section of the graft in a fish mouth pattern. Fibrin glue may be used to reinforce the repair. The surgeon must revisit all repair sites at the end of the

Fig. 9.2 Intraoperative photograph demonstrating the technique of fish mouthing in the proximal segment (P) of a repaired common peroneal nerve using two grafts of sural nerve, to include all the outgoing axons to reach the distal segment, in an attempt to maximize the functional recovery.

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Fig. 9.3 Intraoperative photograph depicting coaptation of three sural nerve grafts from C5 nerve root healthy stump to upper trunk elements (suprascapular nerve, posterior and anterior divisions of upper trunk). C6 nerve root was avulsed in this case. UT, upper trunk.

Fig. 9.4 Local sensory nerves can be used when the major injured neighboring nerves requires repair. In this case, the median nerve (M) was reconstructed using graft obtained from the adjacent medial antebrachial cutaneous nerve of the arm (MACN).

procedure, as they can get distracted when repair is performed elsewhere. It is important to place the repair on a healthy vascularized bed to promote healing and reduce scarring. The functional outcome is believed to be inversely proportional to the length of the graft, with poorer results with the use of longer grafts. Though seemingly true, this has to be viewed in a different light. Longer grafts are used when there is a greater nerve tissue loss, which in turn is usually seen in extensive and more proximal injuries. This is also associated with loss of neurons in the spinal cord or dorsal ganglia, which would substantially contribute to the negative outcome. Hence, the use of longer grafts is associated with more severe injuries and greater reinnervation time. Siemionow et al described the single fascicle method of nerve repair. In experimental models, they could demonstrate faster regeneration and better functional outcome when single fascicle repair was performed on rat sciatic nerve covering 25 to 59% of the cross-sectional area of the nerve. They believed that this technique reduced foreign body reaction, intraneural fibrosis, and donor-site morbidity by reducing the amount of graft material required.37 Clinical application, however, has not been reported. The commonly used donor nerve grafts are sural nerve, medial antebrachial cutaneous nerve above and below elbow, lateral antebrachial cutaneous nerve below elbow, superficial sensory radial nerve, dorsal cutaneous branch of ulnar nerve, and lateral femoral cutaneous nerve of thigh. The graft choice depends on site of nerve injury and surgeon’s preference. Whenever possible, the graft should be harvested from the same limb so that the surgery can be performed under regional anesthesia and an additional incision can be avoided (▶ Fig. 9.4). However, most often, sufficient graft length is not available from the injury site, leading to incision and exploration of the

different region, thus increasing morbidity, operative time, and chances of wound complications. Moreover, harvesting of a nerve adjacent to the injured nerve would result in clinically unacceptable sensory loss. The sural nerve is one of the most commonly used donor nerve grafts. It supplies cutaneous sensation to the posterior and lateral aspect of the lower one-third of the leg and also lateral aspect of the foot and heel. It can be easily harvested from the posterolateral lower leg. The sural nerve has a diameter of 2.5 to 4 mm proximally and 2 to 3 mm distally with around 9 to 14 fascicles fed by robust nutrient artery and veins. This contributes to the faster graft revascularization and better healing. The sural nerve can easily provide 30 to 50 cm of graft, making it the first choice when repairing large gaps. It is harvested with the patient in supine position with the lower extremity internally rotated and flexed at the hip, flexed at the knee, and dorsiflexed at the ankle. A longitudinal incision or multiple-step incisions may be used to obtain the nerve. The morbidity associated with this procedure includes calf tenderness, numbness along the lateral aspect of the foot, neuroma formation, and intolerable pain. In a study, 6.1% had clinically symptomatic neuromas and 9.1% were found to be dissatisfied with the numbness in the foot.38

9.6.2 Allografts Allografts from cadaveric donors have been used rarely when the bridging gap is exceedingly high so that available autografts would not suffice.39 With allografts, surgeons have an unlimited length of nerve tissue available for grafting. They provide guidance and viable donor Schwann’s cells (SCs) to regenerating host axons. Allograft nerve is not as immunogenic as skin or muscle, but certainly requires immunosuppressive therapies to prevent rejection. Without such therapies posttransplantation, the

Surgical Repair of Nerve Lesions: Neurolysis and Neurorrhaphy with Grafts/Tubes donor nerves blood–nerve barrier is broken down, graft is revascularized, and infiltration of immune cells occurs, ultimately leading to graft rejection.40 However, Midha et al reported that the immunogenicity of allografts steadily decreased over time as the process of SC exchange from donor to host proceeds.41,42 The following are the strategies available today to prevent graft rejection: ● MHC matching: MHC matching leads to better results, similar to any organ transplantation. Mackinnon et al, in a study of seven patients, demonstrated a return of sensory and motor function in six patients when ABO blood type matched donor allografts were used. Despite being covered with immunosuppressive medications, one of these patients experienced rejection.39 ● Nerve allograft preparation: Several methods of allograft preparation are reported in literature. Irradiation and freeze drying techniques were used initially in the 1960s. Subsequently, cryopreservation (10% dimethyl sulfoxide at -196 °C in liquid nitrogen) and lyophilization techniques were used. In cold storage technique, allografts were harvested within 24 hours of death and were stored in university of Wisconsin cold storage solution at 5 °C for 1 week. This decreased the antigenic load and hence the chances of rejection. Moreover, the doses of immunosuppressive agents could be reduced following cold storage.43 ● Immunosuppression: Most of the data for immunosuppressive strategies come from experimental models. Cyclosporine, which is a calcineurin inhibitor, was one of the first drugs to be tried with nerve allografts. It worked by blocking the transcription of interleukin-2, which played a significant role in the inflammatory cascade of rejection. Subsequently, tacrolimus (FK-506, also a calcineurin inhibitor) was found to be better than cyclosporine in terms of functional recovery and axonal regeneration. The graft pretreatment in cold storage substantially reduced the therapeutic doses of these drugs, thereby bringing down the undesirable side effects.43 Unlike cyclosporine, tacrolimus can rescue grafts within 10 days of onset of rejection.44 When decellularized allografts are used, immunosuppressive medications are not required as they are devoid of living SCs. These allografts act like a scaffold provided by the extracellular matrix for axon regeneration.45,46,47 In a study by Karabekmez et al, 10 sensory nerve gaps in seven patients were reconstructed with AxoGen nerve allografts (decellularized allograft), the lengths of which ranged between 5 and 30 mm. Five patients achieved excellent results, and the other five patients had good results.47 AxoGen allografts are thought to have better results when compared to type 1 collagen conduits.48 Despite the lack of living SCs, several uncontrolled studies have reported good results with decellularized grafts.47,49 The authors do not advise use of decellularized allograft or tube repairs for gaps exceeding 3 cm (see Chapter 9.7).

9.7 Nerve Tubes Despite being the gold standard in bridging the gap in peripheral nerve injuries, autologous nerve grafts come with several disadvantages such as donor-site neurological deficit, need for additional incisions and chances of wound complications, neuroma formation and neuropathic pain, limited availability, and so on. Only 40 to 50% of autologous nerve grafting show useful degree of functional recovery.50 These issues have paved the way to the study and use of nonnerve grafts as a conduit for axonal regeneration. A tube works by encasing the distal and proximal nerve ends, guiding axons sprouting from the regenerating nerve end, protecting them from fibrous tissue, and providing a path for diffusion of neurotropic and neurotrophic factors from the injured nerve stump.51 An ideal conduit should be biodegradable and nontoxic to axons, produce minimal foreign body reaction and scarring, semipermeable, have an internal structure similar to the architecture of the nerve fascicle, provide protective environment to the nerve regeneration, and be easy to manipulate.52,53,54 Some biomaterials used for tubulization are prone to swelling in vivo, which, if excessive, may block the tunnel and prevent nerve regeneration through it. Therefore, the tube diameter should exceed the nerve diameter by 20%. Conduits are expected to be resorbed gradually with the completion of axonal regeneration. Should this happen too fast, there will be focal inflammation and swelling. On the other hand, if it is too slow, it can cause compression of the regenerated nerve and chronic immune rejection.55 Technique: The healthy nerve stumps are inserted into the tube. Following this, a nonabsorbable microsuture is placed in a “U” fashion—outside to inside of the tube, then through the epineurium 1 to 2 mm behind the stump edge, then again from inside to the outside of the tube to tie a knot after pulling the stump into the lumen (▶ Fig. 9.5).

Fig. 9.5 A 1.5-cm gap in the deep peroneal nerve in the dorsum of the foot is shown being repaired with a 2-cm long collagen tube. The nerve at the proximal end has already been approximated within the lumen of the tube with a single 9–0 microsuture, while the two branches distally are shown inserted within the tube, awaiting microrepair.

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Surgical Repair of Nerve Lesions: Neurolysis and Neurorrhaphy with Grafts/Tubes The interior of the lumen is then filled with saline, using a small-gauge needle and syringe, to flush out any air bubbles. Fibrin glue is used to reinforce the ends. At present, tubulization techniques are indicated only for shorter nerve gaps (< 3 cm).35,56

9.7.1 Autologous Conduits Autologous nonnerve grafts constitute a natural and nontoxic alternative to autologous nerve grafts. These include arteries, veins, mesothelial chambers, skeletal muscle or muscle basal lamina, human amniotic membrane, and epineural sheath. Arterial grafts were initially used, but subsequently fell into disfavor due to morbidity, poorer outcome when compared to nerve grafts, and lack of dispensable arteries. Vein grafts have been studied extensively by many authors. Wang et al demonstrated faster conduction velocities and greater axon counts with inside-out vein grafts compared to autologous nerve grafts in experimental models.57 The adventitia of these vessels provides a conduit which is rich in collagen, laminin, and SCs, thereby creating a milieu ideal for axonal regeneration. Some authors have used vein grafts filled with muscle to prevent collapse of the conduit.58 Similar to a nerve graft, the SCs migrate and proliferate very early in these types of grafts. Karacaoglu et al, in a study of 40 rats, compared nerve grafts, vein grafts, and epineural grafts.59 They found that the functional outcome with epineural grafts was similar to that of the nerve grafts and was significantly better than the vein grafts. They concluded that the use of epineural graft, which is a readily available conduit, could potentially eliminate the use of nerve grafts and the morbidity associated with them. Another biological conduit of historical interest is the tendon autograft; however, with the absence of clinical studies, it is unclear whether autologous tendons are useful in human nerve repair.60,61

9.7.2 Artificial Conduits Over the past few decades, several authors have explored the potential of synthetic biocompatible conduits for axonal regeneration. Lundborg et al,62 with their landmark work on silicone tubes, threw light on this novel treatment strategy. The mechanism by which these conduits aid axonal regeneration was elucidated. The fluid exuding from the transected nerve ends is known to create a fibrin matrix which would act like a cable for cell migration. Subsequently, a regenerating core is formed which eventually matures to form a pseudonerve sheath with microfascicles. With longer gaps, thin cables are formed, resulting in contraction of the fibrin matrix, thus limiting axonal regeneration. Lundborg et al reported a series of mixed nerve injuries in the forearm, with gaps less than 5 cm, treated with silicone tubes.63 These patients suffered a constellation of problems secondary to the use of silicone tubes such as superficial soft-tissue irritation,

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fibrotic reaction, and compression necessitating the removal of the conduits in many of them. This gave rise to the popularity of several other semipermeable and biocompatible conduits such as polyglycolic acid polymer (PGA), polylactide-caprolactone polymer (PLCL), type 1 collagen, polyglycolic acid coated with cross-linked collagen, and decellularized porcine submucosa tubes, with silicone being reserved for shorter gaps (1 cm). Mackinnon and Dellon pioneered the use of polyglycolic acid conduits in 1990.56 They reported a series of 15 patients with digital nerve injuries, with gaps ranging from 5 to 30 mm. They found that 13 patients had good to excellent results after a follow-up of 11 to 32 months. Weber et al conducted a large, prospective, randomized study in which PGA conduits were compared to direct coaptation or autologous nerve grafting.64 They reported similar results in both groups; however, PGA conduits fared better when the gaps were longer than 4 mm. In a recent experimental study by Costa et al, the differences between autografts, PGA conduits, and autografts enveloped with PGA conduits were analyzed. They showed greater number of regenerated myelinated axons in autografts enveloped with PGA group; however, there was no demonstrable difference in functional outcome.65 PLCL tubes are transparent polymer-based tubes allowing visualization of the nerve stumps within. This material degrades by hydrolysis and is fully resorbed by 3 to 24 months. They swell circumferentially post implantation, thereby having an impact on the selection of the size of the conduit. Bertleff et al compared PLCL tubes with autologous grafts in a randomized study of 30 patients and found no significant difference in the outcome between the two groups.66 However, they reported complications such as irritation and extrusion from the wound, necessitating revisions in two of their patients. Chiriac et al reported 29 patients who have undergone repair with PLCL conduits in sensory and mixed nerves, with gaps ranging from 2 to 25 mm. They found recovery of useful function in only 31% of sensory nerves and 8% of mixed nerves, with a 30% complication rate necessitating explantation in some of them. The unsatisfactory outcome and safety profile prompted them to advise against the use of PLCL conduits in hand surgeries.67 Collagen conduits are being used by numerous authors in many arenas of peripheral nerve repair. Outcomes were first reported by Lohmeyer et al in 2009 in 15 digital nerve repairs with a mean nerve gap of 12.5 ± 3.7 mm. They achieved good to excellent results in nine of these patients, but did not recommend its use in gaps more than 15 mm.68 Haug et al also reported the results of 45 digital nerve repairs in 35 patients with a mean defect length of 12 mm. The recovery of sensory function at 12-month follow-up was found to be good to excellent in 25 patients. They also reported 40% return of static twopoint discrimination in gaps up to 20 mm. In their opinion, the positive prognostic factors were age < 50 years

Surgical Repair of Nerve Lesions: Neurolysis and Neurorrhaphy with Grafts/Tubes and distance of the lesion to the fingertip < 5 cm.69 Recently, in a prospective two-center cohort study, Lohmeyer et al analyzed 49 digital nerve repairs using type 1 collagen in 40 patients, with gaps ranging from 5 to 25 mm.70 They had good to excellent results in 20 patients (based on two-point discrimination), whereas 9 patients achieved no sensibility. They added that gaps less than 10 mm performed significantly better than those more than 10 mm, which was a change from their previous recommendation of 15 mm. Boeckstyns et al compared collagen conduits and conventional neurorrhaphy in a prospective randomized controlled trial in 32 patients.71 They concluded that collagen conduits gave useful recovery of sensory and motor functions similar to conventional neurorrhaphy at 2-year follow-up when the gap was less than 6 mm. They also observed that the operating time was significantly shorter for collagen conduits. However, collagen conduits are also not immune to complications. Two papers have reported complications such as failure of resorption of the conduit, classic hourglassing of the fibrin matrix, fibrosis, scarring, neuroma formation, and foreign body reaction on histological assessments.72,73 In the authors’ opinion, commercially available tubes and decellularized allografts should be restricted to gap lengths of 25 mm with no larger than 30 mm tubes used. All other gap repairs should be repaired with nerve autografts.

9.8 Post-op Management Post-op care is a critical phase in the management of peripheral nerve injuries. A thorough and meticulous attempt for adequate hemostasis should be made to avoid operative site hematoma. Suction drains may be avoided as much as possible to avoid potential injury to the nerve repair during drain removal. The strength of a nerve repair usually plateaus by the third week. Hence, all limb movements should be exercised with caution during this time period, with special attention to avoid overstretching, abduction, or extension. Most nerve repairs are performed in extension to avoid suture distraction postoperatively. A bulky operative site dressing usually serves as a reminder to avoid excessive movements in the early post-op period. Shoulder immobilization or sling is used for brachial plexus repair. After 3 weeks, the degree of limb excursions and ambulation should be gradually escalated with the help of physiotherapy and occupational therapy. It is important to mobilize the extremity to promote healing and to avoid joint contractures. Clinical evidence of target muscle innervation is usually not apparent for several months postoperatively, depending on the regeneration distance. Once reinnervation occurs, more focus is invested on strengthening measures. Sensory symptoms and neuropathic pain could be alleviated by pharmacotherapy. In case of refractory pain, referral to pain services or neurostimulation may be considered.

9.9 Tissue Engineering and Future of Nerve Repairs Due to an improved understanding of the pathophysiological processes of axonal regeneration in the past few decades, there has been a stupendous advance in the surgical management of PNI. However, the management of PNI with defects > 30 mm still remains a challenge. The use of autologous grafts, despite being a gold standard strategy, comes with significant associated morbidity, as mentioned earlier. As a result of this, focus is now invested on tissue engineering techniques to enhance nerve regeneration on a larger scale. Autologous cell transplantation has gained a lot of attention in the last two decades. Glial cell transplantation is known to play a significant role in axonal regeneration, in addition to myelinic and amyelinic ensheathing of axons.74 SCs and olfactory ensheathing cells (OECs) are cell types which have been extensively studied experimentally. In the event of a PNI, SCs express cell adhesion molecules and play an integral role in forming the endoneurial sheath, thus creating a microenvironment conducive to axonal regeneration. On the basis of this, some authors have tried to enrich conduits with SCs hoping to achieve regeneration over a larger distance.75,76 They could demonstrate improvement in the rate and quality of regeneration. Strauch et al reported that SC-seeded vein conduits enabled regeneration over longer gaps (6 cm) in rabbits.77 SCs are derived from the bone marrow, fresh/banked human umbilical cord or neural crest pluripotent, and stem cells found in sites of gliogenesis such as the sciatic nerve and dorsal root ganglia. Recently, Kumar et al demonstrated that adult skin–derived precursor SCs exhibited superior myelination and regeneration properties compared to the chronically denervated SCs.78 Reid et al reported that transdifferentiated adipose-derived SCs expressed a range of neurotrophic factors conducive to axonal regeneration.79 These are convenient alternatives to conventional techniques of SC harvest. SCs are also known to influence the macrophage response following PNI, thus impacting myelin debris clearance and regeneration. Stratton et al have reported the positive immunomodulatory and regenerative properties of adult skin–derived precursor SCs.80 Recently, OECs derived from the olfactory nerve have triggered a lot of interest in axonal regeneration research. Its applicability in central and peripheral nervous system makes it unique. It is believed that OEC transplantation at the time of microsurgical repair would act like a scaffold and also provide trophic and directional cues for axonal regeneration.74 The therapeutic benefits of cell transplantation are tainted with several setbacks which would essentially hamper their translation to clinical practice. The primary issue has been preservation of cell viability after thawing and insertion into the conduit.81 Other concerns are aberrant, nonlinear axonal growth, possibility of malignancy,

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Surgical Repair of Nerve Lesions: Neurolysis and Neurorrhaphy with Grafts/Tubes and influence of donor conditions such as age, smoking, and diabetes on regeneration. Tissue engineering may be augmented by some adjuncts to microsurgical and transplantation techniques, which includes electrical stimulation,82 manual stimulation,83 and photostimulation.84 The search for a drug or hormone with positive effects on axonal regeneration is still in progress. In the future, we can envision targeted cellular and adjunctive approaches to improve nerve repair and outcomes for peripheral nerve injuries.

References [1] Noble J, Munro CA, Prasad VS, Midha R. Analysis of upper and lower extremity peripheral nerve injuries in a population of patients with multiple injuries. J Trauma. 1998; 45(1):116–122 [2] Narakas AO. Lesions found when operating traction injuries of the brachial plexus. Clin Neurol Neurosurg. 1993; 95 Suppl:S56–S64 [3] Stoll G, Jander S, Myers RR. Degeneration and regeneration of the peripheral nervous system: from Augustus Waller’s observations to neuroinflammation. J Peripher Nerv Syst. 2002; 7(1):13–27 [4] Millesi H. Microsurgery of peripheral nerves. Hand. 1973; 5(2):157– 160 [5] Jaquet JB, Luijsterburg AJ, Kalmijn S, Kuypers PD, Hofman A, Hovius SE. Median, ulnar, and combined median-ulnar nerve injuries: functional outcome and return to productivity. J Trauma. 2001; 51(4): 687–692 [6] Scholz T, Krichevsky A, Sumarto A, et al. Peripheral nerve injuries: an international survey of current treatments and future perspectives. J Reconstr Microsurg. 2009; 25(6):339–344 [7] Ruijs AC, Jaquet JB, Kalmijn S, Giele H, Hovius SE. Median and ulnar nerve injuries: a meta-analysis of predictors of motor and sensory recovery after modern microsurgical nerve repair. Plast Reconstr Surg. 2005; 116(2):484–494, discussion 495–496 [8] Hamlin E, Jr, Watkins AL. Regeneration in the ulnar, median and radial nerves. Surg Clin North Am. 1947; 27:1052–1061 [9] Siemionow M, Sari A. A contemporary overview of peripheral nerve research from the Cleveland Clinic microsurgery laboratory. Neurol Res. 2004; 26(2):218–225 [10] Spinner RJ, Kline DG. Surgery for peripheral nerve and brachial plexus injuries or other nerve lesions. Muscle Nerve. 2000; 23(5): 680–695 [11] Campbell WW. Evaluation and management of peripheral nerve injury. Clin Neurophysiol. 2008; 119(9):1951–1965 [12] Siemionow M, Brzezicki G. Chapter 8: Current techniques and concepts in peripheral nerve repair. Int Rev Neurobiol. 2009; 87:141– 172 [13] Isaacs J. Major peripheral nerve injuries. Hand Clin. 2013; 29(3):371– 382 [14] Townsend PL. Microsurgical techniques in reconstructive surgery. In: Keen G, Farndon JR, eds. Operative Surgery and Management. 3rd ed. Oxford: Butterworth-Heinemann; 1994:434–435 [15] Dvali L, Mackinnon S. Nerve repair, grafting, and nerve transfers. Clin Plast Surg. 2003; 30(2):203–221 [16] Maggi SP, Lowe JB, III, Mackinnon SE. Pathophysiology of nerve injury. Clin Plast Surg. 2003; 30(2):109–126 [17] Tetik C, Ozer K, Ayhan S, Siemionow K, Browne E, Siemionow M. Conventional versus epineural sleeve neurorrhaphy technique: functional and histomorphometric analysis. Ann Plast Surg. 2002; 49(4): 397–403 [18] de Medinaceli L, Prayon M, Merle M. Percentage of nerve injuries in which primary repair can be achieved by end-to-end approximation: review of 2,181 nerve lesions. Microsurgery. 1993; 14(4):244–246 [19] Matsuyama T, Mackay M, Midha R. Peripheral nerve repair and grafting techniques: a review. Neurol Med Chir (Tokyo). 2000; 40(4):187– 199

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[20] Ogata K, Naito M. Blood flow of peripheral nerve effects of dissection, stretching and compression. J Hand Surg [Br]. 1986; 11(1):10–14 [21] Brushart TM, Tarlov EC, Mesulam MM. Specificity of muscle reinnervation after epineurial and individual fascicular suture of the rat sciatic nerve. J Hand Surg Am. 1983; 8(3):248–253 [22] Trumble TE. Peripheral nerve injury: Pathophysiology and repair. In: Feliciano DV, Moore EE, Mattox KL, eds. Trauma. 4th ed. New York, NY: McGraw-Hill; 1999: 2048–2053 [23] Clarke E, Bearn JG. The spiral nerve bands of Fontana. Brain. 1972; 95 (1):1–20 [24] Lundborg G, Rosén B, Dahlin L, Danielsen N, Holmberg J. Tubular versus conventional repair of median and ulnar nerves in the human forearm: early results from a prospective, randomized, clinical study. J Hand Surg Am. 1997; 22(1):99–106 [25] Bratton BR, Kline DG, Coleman W, Hudson AR. Experimental interfascicular nerve grafting. J Neurosurg. 1979; 51(3):323–332 [26] Hudson AR, Hunter D, Kline DG, Bratton BR. Histological studies of experimental interfascicular graft repairs. J Neurosurg. 1979; 51(3): 333–340 [27] Rovak JM, Cederna PS, Kuzon WM, Jr. Terminolateral neurorrhaphy: a review of the literature. J Reconstr Microsurg. 2001; 17(8):615–624 [28] Zhang Z, Soucacos PN, Bo J, Beris AE. Evaluation of collateral sprouting after end-to-side nerve coaptation using a fluorescent doublelabeling technique. Microsurgery. 1999; 19(6):281–286 [29] Mennen U. End-to-side nerve suture–a technique to repair peripheral nerve injury. S Afr Med J. 1999; 89(11):1188–1194 [30] Mennen U. End-to-side nerve suture in clinical practice. Hand Surg. 2003; 8(1):33–42 [31] Viterbo F, Ripari WT. Nerve grafts prevent paraplegic pressure ulcers. J Reconstr Microsurg. 2008; 24(4):251–253 [32] Bertelli JA, Ghizoni MF. Nerve repair by end-to-side coaptation or fascicular transfer: a clinical study. J Reconstr Microsurg. 2003; 19(5): 313–318 [33] Millesi H. Nerve grafting. Clin Plast Surg. 1984; 11(1):105–113 [34] Dellon AL, Mackinnon SE. An alternative to the classical nerve graft for the management of the short nerve gap. Plast Reconstr Surg. 1988; 82(5):849–856 [35] Meek MF, Coert JH. US Food and Drug Administration/Conformit Europe- approved absorbable nerve conduits for clinical repair of peripheral and cranial nerves. Ann Plast Surg. 2008; 60(4):466–472 [36] Best TJ, Mackinnon SE, Evans PJ, Hunter D, Midha R. Peripheral nerve revascularization: histomorphometric study of small- and largecaliber grafts. J Reconstr Microsurg. 1999; 15(3):183–190 [37] Siemionow M, Zielinski M, Meirer R. The single-fascicle method of nerve grafting. Ann Plast Surg. 2004; 52(1):72–79 [38] Ortigüela ME, Wood MB, Cahill DR. Anatomy of the sural nerve complex. J Hand Surg Am. 1987; 12(6):1119–1123 [39] Mackinnon SE, Doolabh VB, Novak CB, Trulock EP. Clinical outcome following nerve allograft transplantation. Plast Reconstr Surg. 2001; 107(6):1419–1429 [40] Hettiaratchy S, Melendy E, Randolph MA, et al. Tolerance to composite tissue allografts across a major histocompatibility barrier in miniature swine. Transplantation. 2004; 77(4):514–521 [41] Midha R, Mackinnon SE, Becker LE. The fate of Schwann cells in peripheral nerve allografts. J Neuropathol Exp Neurol. 1994; 53(3): 316–322 [42] Midha R, Mackinnon SE, Evans PJ, et al. Comparison of regeneration across nerve allografts with temporary or continuous cyclosporin A immunosuppression. J Neurosurg. 1993; 78(1):90–100 [43] Strasberg SR, Hertl MC, Mackinnon SE, et al. Peripheral nerve allograft preservation improves regeneration and decreases systemic cyclosporin A requirements. Exp Neurol. 1996; 139(2):306–316 [44] Feng FY, Ogden MA, Myckatyn TM, et al. FK506 rescues peripheral nerve allografts in acute rejection. J Neurotrauma. 2001; 18(2):217– 229 [45] Isaacs J. Treatment of acute peripheral nerve injuries: current concepts. J Hand Surg Am. 2010; 35(3):491–497, quiz 498 [46] Johnson PJ, Newton P, Hunter DA, Mackinnon SE. Nerve endoneurial microstructure facilitates uniform distribution of regenerative fibers:

Manual of Peripheral Nerve Surgery | 25.07.17 - 10:01

Surgical Repair of Nerve Lesions: Neurolysis and Neurorrhaphy with Grafts/Tubes

[47]

[48]

[49]

[50] [51] [52]

[53]

[54]

[55] [56]

[57]

[58]

[59]

[60]

[61] [62]

[63]

[64]

[65]

[66]

a post hoc comparison of midgraft nerve fiber densities. J Reconstr Microsurg. 2011; 27(2):83–90 Karabekmez FE, Duymaz A, Moran SL. Early clinical outcomes with the use of decellularized nerve allograft for repair of sensory defects within the hand. Hand (NY). 2009; 4(3):245–249 Whitlock EL, Tuffaha SH, Luciano JP, et al. Processed allografts and type I collagen conduits for repair of peripheral nerve gaps. Muscle Nerve. 2009; 39(6):787–799 Guo Y, Chen G, Tian G, Tapia C. Sensory recovery following decellularized nerve allograft transplantation for digital nerve repair. J Plast Surg Hand Surg. 2013; 47(6):451–453 Lee SK, Wolfe SW. Peripheral nerve injury and repair. J Am Acad Orthop Surg. 2000; 8(4):243–252 Hudson TW, Evans GR, Schmidt CE. Engineering strategies for peripheral nerve repair. Orthop Clin North Am. 2000; 31(3):485–498 Chang CJ, Hsu SH, Yen HJ, Chang H, Hsu SK. Effects of unidirectional permeability in asymmetric poly(DL-lactic acid-co-glycolic acid) conduits on peripheral nerve regeneration: an in vitro and in vivo study. J Biomed Mater Res B Appl Biomater. 2007; 83(1):206–215 Deumens R, Bozkurt A, Brook GA. US Food and Drug Administration/ Conformit Europe-approved absorbable nerve conduits for clinical repair of peripheral and cranial nerves. Commentary. Ann Plast Surg. 2010; 65(3):371 Yannas IV, Zhang M, Spilker MH. Standardized criterion to analyze and directly compare various materials and models for peripheral nerve regeneration. J Biomater Sci Polym Ed. 2007; 18(8):943–966 Muheremu A, Ao Q. Past, present, and future of nerve conduits in the treatment of peripheral nerve injury. BioMed Res Int. 2015; 2015:6 Mackinnon SE, Dellon AL. Clinical nerve reconstruction with a bioabsorbable polyglycolic acid tube. Plast Reconstr Surg. 1990; 85(3): 419–424 Wang KK, Costas PD, Bryan DJ, Eby PL, Seckel BR. Inside-out vein graft repair compared with nerve grafting for nerve regeneration in rats. Microsurgery. 1995; 16(2):65–70 Brunelli GA, Battiston B, Vigasio A, Brunelli G, Marocolo D. Bridging nerve defects with combined skeletal muscle and vein conduits. Microsurgery. 1993; 14(4):247–251 Karacaoglu E, Yüksel F, Peker F, Güler MM. Nerve regeneration through an epineurial sheath: its functional aspect compared with nerve and vein grafts. Microsurgery. 2001; 21(5):196–201 Brandt J, Dahlin LB, Lundborg G. Autologous tendons used as grafts for bridging peripheral nerve defects. J Hand Surg [Br]. 1999; 24(3): 284–290 Tang JB. Vein conduits with interposition of nerve tissue for peripheral nerve defects. J Reconstr Microsurg. 1995; 11(1):21–26 Lundborg G, Dahlin LB, Danielsen N. Ulnar nerve repair by the silicone chamber technique. Case report. Scand J Plast Reconstr Surg Hand Surg. 1991; 25(1):79–82 Lundborg G, Rosén B, Dahlin L, Holmberg J, Rosén I. Tubular repair of the median or ulnar nerve in the human forearm: a 5-year follow-up. J Hand Surg [Br]. 2004; 29(2):100–107 Weber RA, Breidenbach WC, Brown RE, Jabaley ME, Mass DP. A randomized prospective study of polyglycolic acid conduits for digital nerve reconstruction in humans. Plast Reconstr Surg. 2000; 106(5): 1036–1045, discussion 1046–1048 Costa MP, Teixeira NH, Longo MV, Gemperli R, Costa HJ. Combined polyglycolic acid tube and autografting versus autografting or polyglycolic acid tube alone. A comparative study of peripheral nerve regeneration in rats. Acta Cir Bras. 2015; 30(1):46–53 Bertleff MJ, Meek MF, Nicolai JP. A prospective clinical evaluation of biodegradable neurolac nerve guides for sensory nerve repair in the hand. J Hand Surg Am. 2005; 30(3):513–518

[67] Chiriac S, Facca S, Diaconu M, Gouzou S, Liverneaux P. Experience of using the bioresorbable copolyester poly(DL-lactide-ε-caprolactone) nerve conduit guide Neurolac™ for nerve repair in peripheral nerve defects: report on a series of 28 lesions. J Hand Surg Eur Vol. 2012; 37 (4):342–349 [68] Lohmeyer JA, Sommer B, Siemers F, Mailänder P. Nerve injuries of the upper extremity-expected outcome and clinical examination. Plast Surg Nurs. 2009; 29(2):88–93, quiz 94–95 [69] Haug A, Bartels A, Kotas J, Kunesch E. Sensory recovery 1 year after bridging digital nerve defects with collagen tubes. J Hand Surg Am. 2013; 38(1):90–97 [70] Lohmeyer JA, Kern Y, Schmauss D, et al. Prospective clinical study on digital nerve repair with collagen nerve conduits and review of literature. J Reconstr Microsurg. 2014; 30(4):227–234 [71] Boeckstyns ME, Sørensen AI, Viñeta JF, et al. Collagen conduit versus microsurgical neurorrhaphy: 2-year follow-up of a prospective, blinded clinical and electrophysiological multicenter randomized, controlled trial. J Hand Surg Am. 2013; 38(12):2405–2411 [72] Liodaki E, Bos I, Lohmeyer JA, et al. Removal of collagen nerve conduits (NeuraGen) after unsuccessful implantation: focus on histological findings. J Reconstr Microsurg. 2013; 29(8):517–522 [73] Moore AM, Kasukurthi R, Magill CK, Farhadi HF, Borschel GH, Mackinnon SE. Limitations of conduits in peripheral nerve repairs. Hand (NY). 2009; 4(2):180–186 [74] Radtke C, Vogt PM. Peripheral nerve regeneration: a current perspective. Eplasty. 2009; 9:e47 [75] Hadlock T, Sundback C, Hunter D, Cheney M, Vacanti JP. A polymer foam conduit seeded with Schwann cells promotes guided peripheral nerve regeneration. Tissue Eng. 2000; 6(2):119–127 [76] Mosahebi A, Woodward B, Wiberg M, Martin R, Terenghi G. Retroviral labeling of Schwann cells: in vitro characterization and in vivo transplantation to improve peripheral nerve regeneration. Glia. 2001; 34(1):8–17 [77] Strauch B, Rodriguez DM, Diaz J, Yu HL, Kaplan G, Weinstein DE. Autologous Schwann cells drive regeneration through a 6-cm autogenous venous nerve conduit. J Reconstr Microsurg. 2001; 17(8):589– 595, discussion 596–597 [78] Kumar R, Sinha S, Hagner A, et al. Adult skin-derived precursor Schwann cells exhibit superior myelination and regeneration supportive properties compared to chronically denervated nerve-derived Schwann cells. Exp Neurol. 2016; 278:127–142 [79] Reid AJ, Sun M, Wiberg M, Downes S, Terenghi G, Kingham PJ. Nerve repair with adipose-derived stem cells protects dorsal root ganglia neurons from apoptosis. Neuroscience. 2011; 199:515–522 [80] Stratton JA, Shah PT, Kumar R, et al. The immunomodulatory properties of adult skin-derived precursor Schwann cells: implications for peripheral nerve injury therapy. Eur J Neurosci. 2016; 43(3):365–375 [81] Rodrigues MC, Rodrigues AA, Jr, Glover LE, Voltarelli J, Borlongan CV. Peripheral nerve repair with cultured schwann cells: getting closer to the clinics. Sci World J. 2012; 2012:413091 [82] Panetsos F, Avendaño C, Negredo P, Castro J, Bonacasa V. Neural prostheses: electrophysiological and histological evaluation of central nervous system alterations due to long-term implants of sieve electrodes to peripheral nerves in cats. IEEE Trans Neural Syst Rehabil Eng. 2008; 16(3):223–232 [83] Bischoff A, Grosheva M, Irintchev A, et al. Manual stimulation of the orbicularis oculi muscle improves eyelid closure after facial nerve injury in adult rats. Muscle Nerve. 2009; 39(2):197–205 [84] Rochkind S, Geuna S, Shainberg A. Chapter 25: Phototherapy in peripheral nerve injury: effects on muscle preservation and nerve regeneration. Int Rev Neurobiol. 2009; 87:445–464

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Timing in Traumatic Peripheral Nerve Lesions

10 Timing in Traumatic Peripheral Nerve Lesions Leandro Pretto Flores Abstract Surgical timing is one of the most important decisions to take in the operative management of traumatic injuries of peripheral nerves. It depends on a number of factors such as associated injuries, patient stability, level and degree of injury, medical comorbidities, and even the available operative resources. This chapter aims to demonstrate the proper timing for surgical intervention of the different types of traumatic injuries of peripheral nerves. Open wounds due to laceration mechanism deserve urgent attention, and sharp injuries are best treated within the first 72 hours after the trauma; blunt open injuries need a short delay of 3 to 4 weeks before exploration, aiming to avoid further nerve shortening and scar tissue formation into the suture site. Gunshot wounds should be treated conservatively for 4 to 6 months, as most of these injuries do not result in direct nerve hit. The majority of the closed injuries are explored from the third month after the trauma, and surgery is indicated for patients who do not demonstrate signs of spontaneous recovery of the critical muscles. Keywords: nerve injury, timing, microsurgery, trauma

10.1 Introduction Peripheral nerve injury is a dramatic event that significantly affects the daily-living activities of victims sustaining such type of trauma. Although the appropriate treatment is individually based, some general considerations may help in guiding the physician to optimize the proper therapy for a specific case. The main mechanisms that provoke injuries to the nerves of the neck or the limbs are very well known, i.e., traction, compression, laceration, and gunshot wounds. However, the clinical decision about when to operate can be, sometimes, difficult. For the cases of sharp and clean penetrating injuries, it seems logical that an immediate nerve repair shall be indicated. However, if the surgeon performs such acute repair in a penetrating injury associated with blunt trauma, the result may be disastrous. It is even worse for cases of traction injuries, because the decision about when to operate the patient may be one of the most important factors that will determine the final outcome. For these last cases, the surgeon faces a clinical dilemma: to operate early, aiming to decrease the time of muscle denervation, and at the same time taking the risk of operating (and occasionally transecting) a given nerve that would have a potential for spontaneous regeneration; or,

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otherwise, operate later in order to be completely sure about the lack of potential for spontaneous recovery, and assuming the risk that the mechanisms of muscle denervation and atrophy that follows a nerve injury may become so intense that the surgery may become useless. Hence, determining the optimal surgical timing of each patient is one of the most important decisions to take in the operative management of traumatic injuries of peripheral nerves. The operative timing is variable and depends on a number of factors such as associated injuries, patient stability, level and degree of injury, medical comorbidities, and even the available operative resources. The knowledge about nerve regeneration, mechanism of injury, nerve injury classification, and neuropathology may be helpful in order to guide the surgeon in taking the appropriate decision.1 This chapter aims to summarize the most available modern data from the medical literature about the proper timing for surgical intervention of the different possible types of traumatic injuries that affect peripheral nerves. Discussion about surgical timing for brachial plexus and facial nerve injuries has been excluded, because these issues will be further detailed in specific chapters.

10.2 Basic Science as an Aid for Taking an Important Decision There are three critical temporal factors that may affect the decision of when to operate and also when to avoid surgery. Resolution of segmental demyelination requires 8 to 12 weeks, so deficits that persist beyond that period of time indicate that there has been axonal damage, not only neuropraxia (Grade I injury). Under ideal conditions, axon regrowth occurs at 1 to 3 mm/day, or 1 inch/month. The time after which irreversible muscle atrophy has occurred and operation cannot provide benefit ranges from 18 to 24 months, depending on: (1) the type of injury, (2) the injured nerve, and (3) the proposed technique for reconstruction. The Schwann cells and the endoneurial tubes remain viable for 18 to 24 months after injury. If they do not receive a regenerating axon within this time span, the tubes degenerate. Reinnervation must occur not only before the muscle undergoes irreversible changes, but also before the endoneurial tubes will no longer support the nerve regrowth. Hence, the timedistance equation has two primary variables: irreversible changes in critical target structures after 18 to 24 months, and axon regrowth rate at 1 to 3 mm/day from the site of injury or from the site of the surgical repair.2

Timing in Traumatic Peripheral Nerve Lesions

10.3 Initial Evaluation of a Peripheral Nerve Injury The injuries that involve the nerves of the head, neck, and limbs are classified generally as closed (those caused by stretch or compression mechanisms) and open or penetrating (consequence of laceration or missile wounds). The most frequent type of injury observed in civilian practice are closed tractions injuries resulting from vehicular accidents; the injuries provoked by gunshot wounds and those that occurs secondary to blunt penetrating mechanism are less frequent, but still not uncommon; and lesions from sharp and clean divisions of peripheral nerves are usually very uncommon (in this last group, iatrogenic injuries may be very incidental).3 The surgical timing and the management of closed and open injuries are different, and the type of the injury must always be determined at the moment of the initial evaluation. It is apparent in the majority of the cases, and specific details about the circumstances of the aggression or the trauma itself should be sought, as this kind of information may have prognostic value. For example, the severity of the trauma is usually roughly proportional to the degree of damage to the involved nerves. Evaluating the postinjury neurological status following a peripheral nerve trauma—i.e., whether the deficit is improving, static, or worsening—has paramount importance for the decision-making process that finally will allow the surgeon to determine who are going to be operate or when one must be operated. Moreover, close attention to the progression of the neurological recovery in such cases will provide additional data about the severity of the lesion and will aid in establishing a working prognosis. Immediately following the injury, nearly all of the patients will show a specific neurological loss (it is very rare a progressive neurologic deficit following a peripheral nerve injury that initiate hours or days after the trauma; however, they may be observed occasionally in clinical practice, for example, in injection injuries). Some of the patients will improve, and the prognosis of such lesions is good for the great majority of them. Other patients will not improve, and eventually they will need a surgical intervention in order to obtain a better recovery. However, some deficits may become worse in time—what may indicate a continued or progressive increasing pressure onto the involved nerve (e.g., the development of a pseudoaneurysm in a nearby artery; or the presence of a clot on a tunnel nerve area) and may demand an urgent surgery for decompression.4

10.4 Causes of Traumatic Peripheral Nerve Injury As described earlier, traumatic peripheral nerve injuries are basically classified as closed or open, and operative

timing is mainly dictated by type of the lesion. However, there are a number of different possible causes that has the potential to damage the peripheral nervous system, named as follows: ● Stab wounds are characteristically open lesions that result from clean and sharp lacerations. They are more often provoked by objects with a cutting edge in one or both of its borders, such as a knife or a glass. Neurological deficits associated with such type of injury are always associated with nerve transection (partial or total) or neurotmesis (Sunderland Grade V injury). Little trauma to the nerve stumps and minimal local tissue trauma is the rule in most of these cases. ● Open injuries secondary to lacerations may also be caused by blunt trauma. In these cases, the nerve is divided by jagged metal or saws, especially chain saws, where a ragged, torn skin wound is usually observed. Local damage is often more extensive in such type of injury, and associated vascular or bone trauma may also be present. It is not infrequent that the wound may show gross contamination. The extension of the nerve injury is usually longer than those associated with stab wounds, and it is usually difficult to evaluate it in the first days that follow the trauma. Moreover, these injuries are associated with a large amount of scar tissue formation following the healing process, and this fibrosis may prevent appropriate nerve regeneration if an early nerve suture is attempted.5 ● Gunshot wounds are open injuries with little or no tissue exposure, with some unique features that require different approach from the other wounds provoked by penetrating mechanism. Such lesions have a variable degree of intraneural derangement. Most of the missile trajectories are associated with neural injury that do not directly strike the nerve, but instead provide a near miss. The projectile may provoke contusive forces that result in dual stretching to the neural tissue: as the missile approaches the nerve, the nerve explodes away from the missile’s trajectory and then implodes back when the missile passes by. Such damage extends over a length of the nerve, and produces a swollen and hemorrhagic neural segment. These forces may produce a combination of conduction block, axonotmesis, or neurotmesis, and a neuroma-in-continuity is often observed. The proportion of axonotmetic and neurotmetic changes will determine the potential for useful regeneration. These injuries may also result in vascular and bone trauma, and the formation of acute hematoma, traumatic pseudoaneurysm, or arteriovenous fistula has the potential to determine nerve compression.6 ● Bone fractures may also be implicated as a cause of injury to adjacent nerves. The dislocation of a bony fragment may result in lesion by mechanism of stretching, direct compression, or ischemia. In all of these situations, the injury is considered and managed as closed. Good examples are the classical pattern of radial nerve

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Timing in Traumatic Peripheral Nerve Lesions

●

●

●

●

palsy that follows a fracture of the middle third of the humerus, or an injury of the suprascapular nerve associated with fractures of the scapula. There are cases in which the lesion is promoted by a mechanism of ischemia of the nerve. It is a mechanism of injury that is frequently linked to deformations associated with nerve compressions. In these cases, a quick nerve recovery should be expected. The most common example is the so-called Saturday night palsy, associated with a radial nerve compression. However, more serious injuries may be associated with the mechanism of ischemia: Volkmann’s contracture that follows vascular injuries may result in disastrous lesions in even more than one nerve at once, which are often associated with poor recovery. The most common cause for closed injuries is traction or stretching. These lesions have the potential to result in a number of different nerve damage, which include neuropraxia, axonotmesis, and neurotmesis. The formation of a neuroma-in-continuity is frequently noted, and the prognosis will be dictated by the severity of the damage to the cover layer of the nerve. Although this type of lesions are more frequently observed in association with brachial plexus trauma, stretching injuries of distal nerves are also very often observed as a consequence of vehicular accidents. Traction may also provoke lesions to nerves at some points, where they run under a tunnel area, for example, the axillary nerve at the level of the quadrangular space or the musculocutaneous nerve at the level of the coracobrachialis tunnel.7 Injection injuries are closed lesions that deserve attention. This type of injury is caused by a needle placed into or close to a nerve, and the damage is a consequence of the neurotoxic chemical of the agent injected. The extension of the injury varies, depending on whether the toxic substance is injected in the nerve or not, and the degree of neurotoxicity of the agent. In 10% of the cases, the symptoms may be delayed hours or days before their onset. The most common neural injection site is the level of the buttocks, damaging the sciatic nerve; however, injection injuries may involve every major nerve of the body.8 Indirect mechanism of nerve injury, such as thermal, radiation, and electrical, are closed lesions that promote very extensive and diffuse damage to nerves. Moreover, these aggressors also result in extensive fibrosis formation in the surroundings soft tissues, and managing these cases is usually very difficult.

10.5 Specific Surgical Timing For many years, there was a strong tendency to favor delayed repair in traumatic nerve injuries. This bias has its origin from the experience obtained with wartime injuries, in which considerable soft-tissue trauma was frequently associated, preventing a clear demarcation of the

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ultimate level of nerve injury until the local inflammation declines.9 However, with the progressive advance of the microsurgical techniques and electrophysiology, early repairs become increasingly advised. Currently, delayed reconstruction is done when nerve continuity is uncertain or when it is suspected that the natural recovery could be better than surgery. One of the major precepts of peripheral nerve surgery is that incomplete lesions do better without surgery. The major disadvantages of late nerve reconstructions include the progressive collapsing of the endoneural tubes and the continuous progression of the muscular denervation, factors that can downgrade the final outcome.10 An end-to-end suture maximizes the axonal offer to the distal stump of the transected nerve; however, this type of repair needs some extra length of nerve mobilization, which is only possible during the first few days that follows the trauma.11 Early or late repair can be indicated based on the type of injury associated with the nerve trauma, as discussed next.

10.5.1 Open Wounds: Laceration Mechanism In stab wounds, the associated neurological deficit is assumed as being a consequence of a nerve transection, and recovery will not occur without repair. Still, there is a small but realistic chance that the nerve has not been divided, as the wounding agent may only contused or stretched the nerve rather than transected it; however, early exploration of the involved nerve is always advised. Although most of the authors agree that a clean and sharp injury (knife, blade, glass, etc.) may require immediate repair in order to optimize the final outcome, there is no reason to treat it as a surgical emergency. A delay of 24 to 72 hours is acceptable if the general conditions of the patient need some further stabilization or if the ideal resources for the nerve suture are still not available. When the repair is done within few days, an end-to-end suture of the nerve stumps is possible once the elasticity of the epineurium allows that the stumps may be drawn together. If the nerve is not repaired acutely, there is retraction of the proximal and distal stumps, and the scar tissue will fix the nerve ends at their retracted lengths. These mechanisms increase the probability that grafting will be needed to bridge the gap, lessening the likelihood of a good outcome.12 Technical conditions in performing the surgery is another important issue that must be taken into consideration when deciding for an early repair: this implies the use of microscope magnification, 9.0 or 10.0 caliber sutures, and a careful manipulation of nerve structures using microsurgical instrumental. Any attempt to suture the nerve beyond these conditions will result in unnecessary damage to nerve tissue, increasing local fibrosis reaction and worsening the functional results at long-term

Timing in Traumatic Peripheral Nerve Lesions follow-up. Hence, it is better to wait until ideal technical conditions for nerve repair are available before deciding to explore the wound.13 Lacerations associated with blunt trauma require a different approach. If the wound is torn, contused, or contaminated, it is better to delay the repair until the affected site becomes cleaned and uninfected. Moreover, under these conditions it is uncertain what length of the nerves is really damaged, or to predict how much scar tissue is going to deposit into the injury site. Early surgery may lead to poor outcomes, as scar tissue may form within the nerve and also at the suture site, blocking the axonal regeneration. Delayed (not late) surgery is the rule for such scenarios. The best approach to these injuries is to identify the stumps of the affected nerve during the initial surgery (i.e., surgery for soft-tissue debridement, stabilization of fractures, vascular repair, etc.) and to tack them down to tissue near each other. Any attempt of primary suture under tension must not be done, even temporarily, as this maneuver will lead to increased scar formation at the nerve stumps. Tacking down the nerve stumps during the acute exploration of the wound will limit the shortening of the nerve ends, allowing further reconstructions with shorter grafts. Hence, blunt and contuse penetrating traumas to nerves are best managed by waiting 3 to 4 weeks before performing the definitive nerve suture. The repair can be done after resection of the damaged nerve back to areas of healthy tissue appearance and where viable fascicles can be identified, decreasing the chance of excessive fibrosis formation at the suture site.14

10.5.2 Open Injuries: Gunshot Wounds These are penetrating injuries that require different treatment from the other open nerve wounds. In most of the cases, the missile does not strike the nerves directly, but it causes much more contusion and ischemia. The involved nerves may be damaged over a long extension, although many of them are found in gross anatomical integrity. Hence, the best way to manage such lesions is to consider them as closed, and due to the high incidence of injuries in continuity—with implies likelihood of spontaneous recovery—conservative initial treatment is advised.15 Most of the authors advocate that a 4 to 6 months’ wait before surgical exploration should be indicated for such patients. Data from wartime records show that military wounds (high-velocity missiles) result in nerve lesions that are characterized by a prolonged recovery period, and a longer period of clinical observation is advised (6 months).16 In civilian practice, the low-velocity missile wounds usually result in more focal nerve injuries, and it is recommended to shorten the period of conservative treatment, exploring the nerve in 3 to 4 months following the trauma.17

Vascular and soft-tissues injuries are relatively common in association with these injuries. If an acute vascular or bone repair is necessary, the affected nerve must be inspected for signs of visible macroscopic discontinuity. If this is the case, no attempt should be made to repair it immediately—because the extent of damage to the nerve ends cannot be determined—and, as in blunt lacerations, it is better to wait 3 to 4 weeks for a second approach, when the longitudinal extent of the injury is more clearly demarcated. If the nerve is found in anatomical continuity, conservative treatment, as described earlier, is recommended. Associated pain syndromes with poor medical and conservative control may also require earlier surgery.18

10.5.3 Closed Injuries: Traction or Compression Closed injuries are more frequently associated with nerve injuries in continuity, i.e., characterized by an absence of gross nerve rupture. The decision to explore a nerve in such scenarios is made by determining whether the neurological deficit is due to a neurotmetic nerve injury— transection or severe internal disrupture—or due to axonotmesis. All efforts are directed toward establishing as precisely as possible whether the nerve is injured completely or partially, and whether or not it is recovering. A common approach when the nerve continuity is uncertain is to wait and to search for signs of clinical or electrophysiological evidence of reinnervation. If no reinnervation has occurred by 3 to 4 months after the injury, exploration should be considered. This time delay allows any component of neuropraxia or axonotmesis to be resolved, confirmed by signs of recovery on the target muscles. This is true for most of the injuries of the large compound nerves of the body, because their first target muscles are frequently placed no more than 10 cm far from the site of the injury, and their recovery can be observed in such time frame. However, this may not be true to very proximal lesions of long nerves in which the critical muscles are located far from the injury site (such as the ulnar nerve or the peroneal nerve); particularities of the surgical managing of such lesions will be discussed in Chapter 10.5.4. Exploration may be delayed some few more months later if the injury is considered incomplete or if the circumstances of the lesion indicate relative minor trauma, but it should not be delayed for more than 6 months. Waiting beyond this time frame will impact negatively on the degree of recovery if the lesion is complete and requires repair, once all time lost prior to the surgical treatment is counted, and the total time required to reinnervate the paralyzed muscles is additioned.19 Electrodiagnostic studies are also useful in planning the timing for the surgery in such cases. A measurement is made from the injury site to the most critical muscle to reinnervate, assuming that, if surgery is necessary, sprouts from the repair site must reach the muscle before

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Timing in Traumatic Peripheral Nerve Lesions irreversible changes occur. At 1 inch/month for axonal regeneration velocity, it important to calculate the time required for the sprouts from the injury site to reach the first target muscle in line for reinnervation. If the first target muscle does not reinnervate on time, exploration is advised.20 On the other hand, in recent years highresolution ultrasonography has been used with increasingly frequency for the study of nerve injuries. It has demonstrated to be a very useful tool to anticipate the operative timing for closed injuries (and also for missile wounds), as it allows disclosing focal nerve abnormalities (such as focal enlargement) and evaluating the degree of intraneural damage (the amount of scar tissue formation within the nerve, and the arrangement and viability of the fascicles). Ultrasound is also useful to differentiate posttraumatic neuroma-in-continuity from nerve discontinuity with end-bulb neuroma, which can guide the surgical planning for an earlier nerve repair.21 There are some specific situations in which closed injuries can or must be managed acutely: ● The first scenario corresponds to those cases in which the involved wound needs to be explored for correction of fractures or vascular or other soft-tissue lesions. In these cases, the nerve can be inspected for its integrity. If the nerve is intact, clinical observation is advised and a second exploration is indicated for the individuals in which no signs of nerve regeneration can be registered 3 to 4 months after the trauma. If the nerve is discontinued, the stumps are tacked down near each other, and the repair is delayed for 4 weeks or until the healing of the fracture. Nerve suture should be avoided in patients with poor or no bone fusion.22 ● Surgery may also be anticipated when it becomes necessary for treating some poorly controlled painful syndromes associated with nerve injuries. Although this kind of complication is more frequently observed in association with missile wounds, they can be noted in patients suffering from traction injuries of nerves with extensive sensory component, such as the median or the posterior tibial nerve. If the surgery is indicated for controlling the pain, intraoperative electrophysiological studies (in special nerve action potentials [NAP]) must be employed to guide the optimal decision regarding the type of technique to repair the nerve (neurolysis or grafting).23 ● Finally, there are cases in which the closed trauma occurred at an area of possible nerve entrapment (such as carpal tunnel, cubital tunnel, and peroneal tunnel), resulting in acute nerve compression manifested by irradiated pain or partial or complete neurological deficit. These cases must be urgently evaluated by imaging techniques, aiming to identify the local elements with potential for compression of the nerve, such as hematomas or dislocated bone fragments. Such scenarios demand acute exploration, appropriate nerve decompression and correction of the underlying condition if possible.

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It is also important to define the time when the nerve repair has little or nothing to offer. Although this limit may vary, because some nerves and muscles may recover better than others, most of the authors agree that nerve surgery should be avoided when the duration of the total muscle denervation exceeds 18 to 24 months. Exceptions to this rule may occur in a group of patients with lesions that maintained some distal axonal continuity, and when the main goal of the surgery is to recover only sensory function (e.g., lesions of the digital nerves). It is also important to recognize when the distance between the nerve injury and the muscles is too great that the nerve reconstruction cannot predict any degree of functional recovery. One of the best examples for such situations is the suture of the ulnar nerve at the level of the axilla: the distance between the injury site and the critical muscles is so far that no intrinsic recovery is predicted, even with early exploration and optimal repair. In these cases, tendon transfers or distal nerve transfer techniques should be elected as the primary approach for restoring motor function.24

10.5.4 Closed Injuries: Special Situations ●

●

Injections injuries: There is considerable controversy regarding the treatment of nerve injection injuries. If the complication is noted immediately, acute open irrigation with normal saline has been advocated in an attempt to dilute the drug and thereby to prevent permanent neuropathy. Although logical, such treatment is rarely practical as patients are infrequently seen acutely and widespread experience with this method is lacking. Early exploration (within 3 to 4 weeks), aiming to perform a thorough external neurolysis, has also been advised. However, most of the authors recommend exploration of those nerve injection injuries that are complete and show no or little recovery at 4 to 6 months.25 Proximal injuries of long nerves: injuries of a complex nerve in a position above the elbow or above the knee are problematic—because of the long distance that the sprouts must travel—making it difficult to reinnervate critical distal muscles before irreversible changes occur. The clinical decision regarding exploration must occur over a much shorter time frame. In these cases, it is advisable to wait 8 to 12 weeks for any component of neuropraxia to resolve. Early surgery (3 months) is acceptable and recommendable for these patients, in order to allow proper time for distal motor and sensory reinnervation. However, the use of intraoperative NAP recording is mandatory during such surgeries: if a NAP can be recorded across the lesion, then external neurolysis is performed; otherwise, repair by means of nerve grafting or by distal nerve transfer is advised.26

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Timing in Traumatic Peripheral Nerve Lesions

10.6 Conclusion Injuries of peripheral nerves may result in severe neurological deficits that can be improved if a proper management strategy is adopted. The surgical timing and a careful microsurgical technique are the most important factors that will determine the outcomes of such lesions. Open wounds due to laceration mechanism deserve urgent attention: sharp injuries are best treated within the first 72 hours, while blunt injuries need a short delay of 3 to 4 weeks to avoid further nerve shortening and scar tissue formation into the suture site. Gunshot wounds should be treated conservatively for 4 to 6 months, as most of this type of lesion does not result in nerve transection. The majority of the closed traction, compression, or stretching injuries must be explored from the third month after the trauma, and surgery are indicated for patients who do not demonstrate signs of spontaneous reinnervation of the target muscles. The best outcomes are obtained if the nerve is treated within the sixth month that follows the trauma; thus, all effort must be directed to properly manage such patients within this time limit. Surgery is still indicated for lesions more than 6 months old; however, the outcomes associated with such procedures are frequently less than optimal. The neurological surgery is not advisable for cases with fixed deficits resulting from injuries more than 2 years old, and secondary procedures (such as tendon transfers) should be offered as primary option for these patients.

References [1] Kline DG, Hackett ER. Reappraisal of timing for exploration of civilian peripheral nerve injuries. Surgery. 1975; 78(1):54–65 [2] Liuzzi FJ, Tedeschi B. Peripheral nerve regeneration. Neurosurg Clin N Am. 1991; 2(1):31–42 [3] Selecki BR, Ring IT, Simpson DA, Vanderfield GK, Sewell MF. Trauma to the central and peripheral nervous systems: Part I: an overview of mortality, morbidity and costs; N.S.W. 1977. Aust N Z J Surg. 1982; 52(1):93–102 [4] Höke A. Mechanisms of disease: what factors limit the success of peripheral nerve regeneration in humans? Nat Clin Pract Neurol. 2006; 2(8):448–454 [5] Rochkind S, Filmar G, Kluger Y, Alon M. Microsurgical management of penetrating peripheral nerve injuries: pre, intra- and postoperative analysis and results. Acta Neurochir Suppl (Wien). 2007; 100:21–24

[6] Kline DG. Civilian gunshot wounds to the brachial plexus. J Neurosurg. 1989; 70(2):166–174 [7] Kline DG. Physiological and clinical factors contributing to the timing of nerve repair. Clin Neurosurg. 1977; 24:425–455 [8] Kretschmer T, Antoniadis G, Braun V, Rath SA, Richter HP. Evaluation of iatrogenic lesions in 722 surgically treated cases of peripheral nerve trauma. J Neurosurg. 2001; 94(6):905–912 [9] Smith JW. Factors influencing nerve repair. II. Collateral circulation of peripheral nerves. Arch Surg. 1966; 93(3):433–437 [10] Hudson AR, Hunter D. Timing of peripheral nerve repair: important local neuropathological factors. Clin Neurosurg. 1977; 24:391–405 [11] Millesi H. Reappraisal of nerve repair. Surg Clin North Am. 1981; 61 (2):321–340 [12] Robinson LR. Traumatic injury to peripheral nerves. Muscle Nerve. 2000; 23(6):863–873 [13] Martins RS, Bastos D, Siqueira MG, Heise CO, Teixeira MJ. Traumatic injuries of peripheral nerves: a review with emphasis on surgical indication. Arq Neuropsiquiatr. 2013; 71(10):811–814 [14] Sunderland S. The anatomic foundation of peripheral nerve repair techniques. Orthop Clin North Am. 1981; 12(2):245–266 [15] Katzman BM, Bozentka DJ. Peripheral nerve injuries secondary to missiles. Hand Clin. 1999; 15(2):233–244, viii [16] Roganović Z, Savić M, Minić L, et al. Peripheral nerve injuries during the 1991–1993 war period [in Serbian]. Vojnosanit Pregl. 1995; 52 (5):455–460 [17] Nicholson OR, Seddon HJ. Nerve repair in civil practice; results of treatment of median and ulnar nerve lesions. BMJ. 1957; 2(5053): 1065–1071 [18] Stanec S, Tonković I, Stanec Z, Tonković D, Dzepina I. Treatment of upper limb nerve war injuries associated with vascular trauma. Injury. 1997; 28(7):463–468 [19] Kline DG. Timing for exploration of nerve lesions and evaluation of the neuroma-in-continuity. Clin Orthop Relat Res. 1982(163):42–49 [20] Aminoff MJ. Electrophysiologic testing for the diagnosis of peripheral nerve injuries. Anesthesiology. 2004; 100(5):1298–1303 [21] Koenig RW, Pedro MT, Heinen CP, et al. High-resolution ultrasonography in evaluating peripheral nerve entrapment and trauma. Neurosurg Focus. 2009; 26(2):E13 [22] Amillo S, Barrios RH, Martínez-Peric R, Losada JI. Surgical treatment of the radial nerve lesions associated with fractures of the humerus. J Orthop Trauma. 1993; 7(3):211–215 [23] Dworkin RH, Backonja M, Rowbotham MC, et al. Advances in neuropathic pain: diagnosis, mechanisms, and treatment recommendations. Arch Neurol. 2003; 60(11):1524–1534 [24] Hubbard JH. The quality of nerve regeneration. Factors independent of the most skillful repair. Surg Clin North Am. 1972; 52(5):1099– 1108 [25] Clark WK. Surgery for injection injuries of peripheral nerves. Surg Clin North Am. 1972; 52(5):1325–1328 [26] Spinner RJ, Kline DG. Surgery for peripheral nerve and brachial plexus injuries or other nerve lesions. Muscle Nerve. 2000; 23(5): 680–695

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Outcomes in the Repair of Nerve Injuries

11 Outcomes in the Repair of Nerve Injuries Lukas Rasulic and Miroslav Samardzic Abstract Grading systems for nerve function are needed not only to evaluate individual motor and sensory function, but also to assess entire nerves or plexus elements. Most major nerves innervate one or more proximal muscles, a group of distal muscles, and a distal sensory field of variable functional importance. The most widely accepted system for grading nerve function loss and recovery was introduced by the British Medical Research Council (MRC). Since then, several modifications have been made, but these have not altered the original concept, especially regarding functional priorities. Keeping this in mind, the results of nerve repairs for complex nerve structures—such as the brachial plexus and proximal sciatic nerve—should be analyzed in a somewhat different way than for individual nerves. This chapter focuses on the analysis of prognostic factors and grading systems for individual peripheral nerves, and how they should be modified for more complex nerve structures. Keywords: brachial plexus, nerve injury, operative outcome, prognostic factors, sciatic nerve

11.1 Prognostic Factors Several factors influence the final outcome following nerve repair, most of them independent of the surgeon. These factors can be subdivided as follows: ● Patient age. ● Characteristics of the nerve, including: ○ Topography of the motor neurons. ○ Nerve microanatomy. ○ Main muscle effectors. ● Characteristics of the nerve injury, including: ○ Mechanism. ○ Level. ○ Length of the nerve defect. ○ Associated injuries. ● Surgery. ● Postoperative rehabilitation.

11.1.1 Patient Age It has been generally accepted that a patient’s age is the most important predictor of outcome following nerve repair, with significantly better results generally observed in children and teenagers. The prognosis for functional recovery is the best in children younger than 10 years, with good to excellent results in more than 90% of cases. This compares with 75% in patients between 10 and 20 years old, with results in older children and

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adolescents still better than those attained in adults. On the other hand, there is no significant difference in the outcomes obtained between different age groups among adults. No critical age at which outcomes tend to decline has been established, though other factors may play a more significant role in the elderly. Possible explanations for the enhanced results that children typically experience are: (1) the earlier initiation of regeneration; (2) an increased rate of neural regeneration; (3) greater stability of the neuromuscular junction after denervation; (4) shorter extremities; and (5) increased adaptability and ability for other nonaffected muscles to substitute or modify their motor function to compensate for muscles that have been paralyzed.1

11.1.2 Characteristics of the Nerve It is obvious that repair outcomes vary between different nerves, even within the heterogeneous series that have been reported. Generally, repair of a pure motor or sensory nerve is technically simpler, and its results are better than for combined motor–sensory nerves because of the diminished likelihood of axonal mixing. Discrepancies in repair outcomes between nerves in the upper and lower extremities have also long been described, as well as greater recovery in the tibial nerve versus the peroneal nerve, and better outcomes with radial nerve versus median and peroneal nerve repairs. Most investigators have been unable to detect any meaningful difference in recovery potential between the median and ulnar nerves, though opposing claims also exist in favor of either one or the other. The reasons for differences in motor recovery potential include the topography of motor neurons in the spinal cord, characteristics pertaining to the nerve’s microanatomy, and the nature of the main muscle effectors.2 Examining the topography of motor neurons within the anterior horns of the spinal cord, peroneal nerve neurons are found to be numerous and scattered, while radial nerve neurons are concentrated over a small area within the cross-section of the anterior horn. The topography of the neurons for other nerves is between these two extremes. Considering the characteristics of nerve microanatomy, the following may contribute to different nerve recovery potentials: ● A great proportion of intraneural connective tissue (e.g., within the peroneal nerve) makes it difficult for regenerating axons to grow into empty endoneurial tubes. ● A greater proportion of sensory fibers (e.g., within the median, ulnar, and tibial nerves) is a risk factor for poor

Outcomes in the Repair of Nerve Injuries

●

●

recovery, because of the potential for cross motor– sensory reinnervation. An oligofascicular pattern within the nerve and sparse connections between the bundles increase the probability of good recovery (such are characteristics of the radial, musculocutaneous, and axillary nerve, but not of the tibial and peroneal nerves). Inadequate vascularization in some regions (e.g., the peroneal nerve as it passes by the fibular neck).

Contrary to the peroneal nerve, only one to three risk factors exist for nerves with the best recovery potential (e.g., the radial, musculocutaneous, femoral, and axillary nerve), while four to six risk factors are present among nerves with moderate motor recovery potential (e.g., the median, ulnar, and tibial nerve).

11.1.3 Characteristics of the Nerve Injury

With respect to main muscle effector characteristics, repair outcomes tend to be better in the following cases: ● If the main effectors receive their input relatively proximal within the limb (e.g., the main effectors for the musculocutaneous, axillary, radial, tibial, and femoral nerves). ● If functionally useful reinnervation of the main effectors requires relatively few nerve fibers (e.g., the tibial and radial nerves), as opposed to the lion’s share of the regenerating axons (e.g., the ulnar nerve). ● If complete return of muscle strength is not necessary for good functional recovery (e.g., contraction of finger extensors with only 20% of maximal strength results in minimal functional disability after radial nerve repair). ● If it is not necessary to restore precise or coordinated muscle contractions; such contractions only need to be restored by median, ulnar, and peroneal nerve repairs. ● If any major disability can be precluded or alleviated by muscles supplied by an uninjured nerve; only injuries to the peroneal, ulnar, and radial nerve lack such potential.

Final repair outcomes are influenced considerably by the mechanism of injury and the severity of trauma. In particular, nerve injuries resulting from projectiles/missiles and from traction have a poorer prognosis than other types of injury, because they involve longer segments of nerve. Numerous authors have also recognized the influence of the repair level on the outcome (▶ Table 11.1). Poor prognosis after high-level repairs can be attributed to variations in nerve mapping, especially in cases of nerve tissue loss, and to the irreversible degeneration of sensorimotor effectors. Muscle atrophy starts within 3 weeks of denervation, with almost complete replacement of the muscle with fibrous tissue over the next 2 years. If the calculated reinnervation period for the main muscle effectors is longer than that, nerve repair cannot be accompanied by motor recovery, because of irreversible muscle fibrosis (e.g., useful reinnervation of hand muscles cannot be expected after ulnar nerve repair in the axilla). Conversely, after high radial nerve repairs, regenerating axons grow into distal effectors early enough to prevent irreversible muscle fibrosis (for thumb extensors, within 16–18 months). Such limitations do not apply to sensory recovery, which can be anticipated even after delayed and high-level nerve repairs (▶ Table 11.1 and ▶ Table 11.2). The length of nerve defect—which is determined by both the extent of the initial trauma and the passage of time (due to stump distraction)—impacts outcomes more than the length of the graft. In principle, shorter grafts do better than longer ones. Several authors have claimed

Reviewing these factors, it is clear that risk factors portending poorer motor recovery are especially numerous for the peroneal nerve, which is likely why the peroneal nerve must be considered, among the major nerves, probably the worst candidate for graft repair. The peroneal nerve also has less connective tissue and is less vascularized than the tibial nerve, which is also protected by fatty tissue in the popliteal fossa. Table 11.1 Establishing the level of injury in upper extremity nerves Nerve

High

Medium

Low

Median

Above midarm

Above the lower margin of the pronator teres muscle

Below the pronator teres muscle

Ulnar

Above midarm

Above the middle third of the forearm

Middle and lower third of the forearm

Radial

Above midarm

Above the nerve bifurcation

Posterior interosseous nerve

Musculocutaneous

Above the biceps-brachialis muscle space

Below the biceps-brachialis muscle space

–

Table 11.2 Establishing the level of injury in lower extremity nerves Nerve

High

Medium

Low

Peroneal

Above midthigh

Above the final division

Peroneus profundus

Tibial

Above midthigh

Above the soleus muscle arc

Below the soleus muscle arc

Femoral

Above Poupart’s ligament

Below Poupart’s ligament

–

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Outcomes in the Repair of Nerve Injuries that nerve grafts longer than 5 to 10 cm considerably limit the probability of a good outcome, even though experimental data indicate that certain other factors (e.g., the concomitant damage of effectors) also may be responsible for the poor results typically observed with long nerve grafts.3 Combined nerve injuries, particularly simultaneous lesions affecting the ulnar and median nerve, are frequent, especially after projectile-caused wounds. Although opposing claims also exist, most authors consider that such injuries almost always result in a nonfunctional hand, warranting additional corrective measures. Comorbid injuries in the repair region (e.g., bone fractures, injuries to main arteries, and soft-tissue defects) influence repair outcomes through ischemia, perineural scarring, and defects involving the effectors. Useful motor recovery is more frequent among patients with less local damage.

11.1.4 Surgery One of the most significant determinants of repair outcomes is the duration of time between the initial trauma and surgery. Progressive closing of distal endoneural tubes, resulting in increasingly disproportionate sizes in the proximal and distal nerve stumps, is the consequence of a prolonged preoperative interval. Delaying surgery beyond the aforementioned critical denervation period of 24 months is particularly problematic, particularly for proximal repairs. According to some published data, operations may be postponed safely for 4 to 6 months, but further delay may endanger motor recovery. If the preoperative interval is longer than 24 months, the outcome is likely to be poor, though good results have been sporadically reported for surgeries performed 3 or more years after injury. The choice of surgical procedure is directly influenced by the characteristics of the nerve injury and the timing of nerve repair. Unquestionably, the best results are obtained with neurolysis of lesions-in-continuity. In nerve transections, the chances for useful functional recovery are best following direct nerve suture. It should be emphasized that there is no significant difference in the results obtained with direct epineural or fascicular repair versus nerve grafting with nerve defects up to 5 cm in length. Certainly, other favorable circumstances are necessary in these situations.

11.1.5 Postoperative Rehabilitation Consistent rehabilitation is also necessary for good recovery after nerve repair, particularly after repairs in the upper extremity. Soon after surgery, the patient should be encouraged to use his/her injured extremity as much as possible to prevent contractures and achieve maximal functional recovery.

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11.2 General Grading Systems As stated at the outset, grading systems are needed not only for individual muscle and sensory functions, but also for the evaluation of entire nerve or plexus elements. Most nerves and plexus elements innervate one or more proximal muscles, a group of distal muscles, and also some distal sensory field, the functional importance of which may vary.4 The British Medical Research Council (MRC) system for grading loss or the return of motor function after nerve injury and repair was originally based on grading systems developed to evaluate paralysis associated with poliomyelitis (▶ Table 11.3 and ▶ Table 11.4). To expand the scale, grade 4 subdivisions were introduced, as follows: (4–) slight movement without resistance; (4) moderate movement against resistance; and (4 +) strong movement against resistance. Paternostro-Sluga et al introduced further modifications to this scale, including range of movement (ROM) to indicate subgrades5: ● Grade 2–3: active movement against gravity over less than 50% of the feasible ROM. ● Grade 3: the same as 2–3, with feasible ROM over more than 50%. ● Grade 3–4: active movement against resistance over less than 50% of the feasible ROM. ● Grade 4: the same as 3–4, with feasible ROM over more than 50%. ● Grade 4–5: active movement against strong resistance over the feasible ROM, but distinctly weaker than the contralateral side. ● Grade 5: normal power.

Table 11.3 Grading of the motor outcome—Highet’s classification system Score

Motor outcome

0

Total paralysis

1

Muscle fibrillation

2

Visible muscle contraction

3

Movement against gravity

4

Movement against gravity and some resistance

5

Normal muscle function

Table 11.4 Scoring of motor recovery as recommended by the British Medical Research Council Motor recovery M0

No contractions

M1

Visible or palpable contractions in the proximal muscles

M2

Voluntary contractions of proximal muscles and trace or no contractions of distal muscles

M3

Some voluntary contractions of distal muscles

M4

Contractions of distal muscles against resistance

M5

Full and separate contractions of all distal muscles

Outcomes in the Repair of Nerve Injuries A similar grading system was introduced by the Louisiana State University Medical Center (LSUMC), wherein movement with gravity eliminated was excluded (▶ Table 11.4 and ▶ Table 11.5). Useful motor function was considered to be grade 3 with the MRC scale, versus grade 2 with the LSUMC rating system. For the grading of complete motor function in selected nerves, no system has really superseded the one introduced by Highet in 19416 and proposed to the Nerve Injuries Committee of the MRC in 1954.6,7 The definition of proximal and distal muscles varies depending on the height of repair. Proximal muscles include forearm muscles (for the median and ulnar nerves), the brachioradial and triceps brachii muscles (for the radial nerve), the triceps muscle of calf and posterior tibial muscle (for the tibial nerve), the anterior tibial and peroneus muscles (for the peroneal nerve), and the iliacus and pectineus muscles (for the femoral nerve). Distal muscles include hand muscles (for the median and ulnar nerves), the dorsal forearm muscles (for the radial nerve), the extensor/ flexor muscles of toes (for the peroneal/tibial nerve), and the sartorius and quadriceps muscles (for the femoral nerve). For the grading of sensory function in the autonomous zone of a nerve where there is minimal overlap from adjacent nerves, there are also two systems: MRC and LSUMC (▶ Table 11.6 and ▶ Table 11.7). Samardzic et al8,9,10 used a grading system introduced by Millesi et al in

1976,11 which included the testing of two-point discrimination (▶ Table 11.8). Sensory recovery is not a reliable sign of regeneration, however, mainly because of its late occurrence and difficulties associated with its clinical evaluation. It is functionally important after median and tibial nerve repairs in particular, because sensory loss that occurs in the sole of the foot predisposes patients to recurrent trophic ulceration. Recovery is frequently followed by “sensory relearning,” which is a process of functional cortical reorganization caused by axonal misdirection at the repair site. Sensory recovery is less important for the overall outcome of ulnar, radial, axillary, peroneal, femoral, and musculocutaneous nerve repairs. Recovery of sweating in the autonomous zone may precede sensorimotor recovery by several weeks or months, because autonomic fibers are small in diameter and regenerate more quickly. Finally, to grade the entire nerve, including motor and sensory function, the LSUMC system has been used in several studies (▶ Table 11.9).8,9,10 The term “useful recovery” has been adopted frequently to reflect the functional impact of the repair and variations from nerve to nerve. For the tibial nerve, useful sensory recovery is defined as the return of superficial painful and some tactile sensation, without clear

Table 11.6 Scoring of sensory recovery as recommended by the British Medical Research Council Sensory recoverya

Table 11.5 Louisiana State University Medical Center grading system for motor function Individual muscle grade

S0

Absence of sensation

S1

Recovery of deep cutaneous pain sensation

S2

Return of some degree of superficial pain and tactile sensation

S2 +

Same as in Stage S2, with additional slight hyperresponsiveness

S3

Further recovery of pain and tactile sensation, with no dysesthesia

Grade

Evaluation

Description

0

Absent

No contraction

1

Poor

Trace contraction

2

Fair

Movement against gravity only

3

Moderate

Movement against gravity and some resistance

S3 +

Same as Stage 3, with the addition of some two-point discrimination

4

Good

Movement against moderate resistance

S4

Complete recovery

5

Excellent

Movement against maximal resistance

aSensation

should be tested in the autonomous zone of a nerve, where there is minimal overlap from adjacent nerves.

Table 11.7 Louisiana State University Medical Center grading system for sensory function Sensory grade Grade

Evaluation

Description

0

Absent

No response to touch, pin, or pressure

1

Bad

Testing yields hyperesthesia or paresthesia; deep pain recovery in autonomous zones

2

Poor

Sensory response sufficient for grip and slow protection; sensory stimuli poorly localized with hyperresponsiveness

3

Moderate

Response to touch and pin in autonomous zones; sensation poorly localized and abnormal with some hyperresponsiveness

4

Good

Response to touch and pin in autonomous zones; response localized but sensation abnormal; no hyperresponsiveness

5

Excellent

Near-normal response to touch and pin in entire field including autonomous areas

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Outcomes in the Repair of Nerve Injuries Table 11.8 Grading of the sensory outcome—Millesi’s classification Score

Motor outcome

0

Anesthesia

1

Dysesthesia

2

Protective sensation

3

2PD > 10 mm

4

2PD < 10 mm

5

Normal function

Abbreviation: 2PD, two-point discrimination.

localization (> S2). On the other hand, some restoration of two-point discrimination is also required after median and ulnar nerve repairs. Useful motor recovery (usually > M3) after peroneal nerve repair means restoration of dorsiflexion of the ankle to bring the foot into a neutral position (with or without some degree of foot eversion) because this means that a foot brace will no longer be needed for walking. Inability to regain toe extension is of much less functional importance. Similarly, some plantar flexion must be present to consider the outcome after tibial nerve repair useful. However, useful motor recovery also requires some finger movements to be regained after median and ulnar nerve repair.

11.2.1 Upper Extremity Repair Generally, it is difficult to accurately assess the results of brachial plexus surgery (i.e., nerve transfers), due to poor standardization of the complex injury patterns, varying

functional priorities, and the use of different methods to evaluate functional recovery. For practical purposes, one can use the grading system for upper arm function that is based on the gradations published by Ploncard in 1982 (▶ Table 11.10). The main reasons for this modification are the significance of both nerves for upper arm function, the complexity of shoulder function involving several muscles, and the role of two muscles (biceps and brachialis) in elbow flexion. Other reasons include the importance of ROM, endurance, and the capacity for repetition.10 The level of recovery is typically categorized as fair, good, or excellent. With this grading system, good recovery roughly corresponds to restoration of strength to the level of M2 or higher using the LSUMC grading system, and to M3 or higher according to the British MRC system. To establish a final grade and level of recovery, the follow-up period should be at least 2 years (▶ Table 11.10). Taking into consideration global upper arm function that includes both shoulder abduction and elbow flexion, functional results are graded as follows: ● Poor: when there is absent elbow flexion with any range of shoulder abduction, or fair elbow flexion in the absence of shoulder abduction. ● Partial: when there is fair elbow flexion with any level of shoulder abduction, or good and excellent elbow flexion in the absence of active abduction—such patients may be suitable for secondary reconstructive procedures. ● Useful, grade A: includes good or excellent elbow flexion with fair shoulder abduction—this grade of recovery enables normal daily activities.

Table 11.9 Louisiana State University Medical Center criteria for grading whole nerve injuries Individual muscle grade Grade

Evaluation

Description

0

Absent

No muscle contraction, absent sensation

1

Poor

Proximal muscles contract but not against gravity; sensory grade 1 or 0

2

Fair

Proximal muscles contract against gravity; distal muscles do not contract; sensory grade, if applicable, usually 2 or lower

3

Moderate

Proximal muscles contract against gravity and some resistance; some distal muscles contract against gravity; sensory grade is usually 3

4

Good

All proximal and some distal muscles contract against gravity and some resistance; sensory grade is 3 or better

5

Excellent

All muscles contract against moderate resistance; sensory grade is 4 or better.

Table 11.10 Grading of recovery for upper arm functions following nerve transfers Result Bad Fair Good Excellent

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Elbow flexion

Arm abduction

Shoulder exorotation

No movement or only movement without gravity Movement against gravity with the ability to hold position Up to 90°

Up to 45°

Repeated movements against gravity Full range

Over 45°

Near-normal function with preserved brachiothoracic pinch

Up to 45° Up to 90° Over 90°

Outcomes in the Repair of Nerve Injuries Useful, grade B: includes good or excellent elbow flexion and shoulder abduction—this grade gives the patient some capacity to do manual work with the affected limb.

●

Useful recovery, especially grade B, depends on hand function, which may be partially or completely preserved in patients with a partial injury. In those with total brachial plexus palsy due to avulsions of four to five spinal nerve roots, limited results for hand motion recovery can be achieved with wrist arthrodesis or some other secondary procedure or procedures; however, at best, the patient’s ability to perform any work with that hand will be poor. The published rates of recovery vary depending on the type of nerve transfer and recipient nerve. Meta-analysis data have been collected from 57 reports published over the past 45 years and are presented in ▶ Table 11.11. Shoulder function has also been restored using spinal accessory to suprascapular nerve transfers, with an M3 grade or more of arm abduction achieved in 36.4 to 92% Table 11.11 Rates of recovery of nerve transfers to the musculocutaneous and axillary nerves (meta-analysis data) Percentage of recovery Nerve transfer

Elbow flexion (%)

Arm abduction (%)

Intercostal

42.8–100

33.8–87.5

Spinal accessory

44.4–100

61.5–67.0

Thoracodorsal

83.3–100

36.0–100 81.8–100

Medial pectoral

80.0–91

Oberlin procedure

75.0–100

Phrenic

29.4–100

of cases (mean 58.2%). Similarly, crucial external shoulder rotation has been obtained in 21.4 to 55% of cases, with ROM ranging from 16.7 to 118 degrees. The results of nerve transfers for the lower brachial plexus are not as impressive, achieving M3-level recovery in just 25 to 32% for the median, ulnar, and radial nerves. Kim12 reported rates of recovery of 84.2, 65.1, and 45.9%, respectively, for neurolysis, direct repair, and grafting with lacerations of the brachial plexus. The results for gunshot wounds were in the same range, with 94, 70, and 54% of patients achieving at least an M3 level of recovery. Previously reported results indicated lower rates of recovery. The obtained results for upper nerve elements were significantly better than for the lower elements, with 95 versus 75% of patients achieving M3-level recovery. Results for nerves of the entire upper arm are graded using the scales indicated in ▶ Table 11.12 and ▶ Table 11.13. A period of 2 to 3 years is required for maximal motor recovery after proximal nerve repairs, while even longer periods are necessary for maximal sensory recovery (5–7 years). Clinical series dealing with nerve repairs are infrequent and differ in their outcome assessment protocols, definition of repair levels, mechanisms of injury, patient age ranges, and other variables. ▶ Table 11.14 summarizes the meta-analysis of data reported over the past 40 years by 56 first authors in 77 well-documented papers, where the percentage of useful sensorimotor recovery is considered separately for proximal-level and distal-level repairs. Literature reports on repairs of the median and ulnar nerves mostly include wrist-level lesions. Series exclusively assessing proximal repairs are rare and have mostly yielded discouraging

Table 11.12 Grading of functional recovery for complex structures of the brachial plexus Nerve elements

Function

Good outcome

Satisfactory outcome

I

C5–C6 or upper trunk

Elbow flexion Abductiona Wrist flexion Sensory Extension

M4–5 M3–5 M3–5 S3–4 M3–5

M3 M3 Mc S2 Mc

II

C5–C7 or upper trunk and medium trunk

As for I Finger extension Thumb abduction

As for I M3–5 M3–5

As for I

III

C8–T1 or lower trunk

Finger flexion Hand muscles Sensory

M4–5 M3–5 M3–4

M3 Mc S2

IV

Lateral cord

Elbow flexion Wrist flexion Sensory

M4–5 M3–5 M3–4

M3 M3 S2

V

Medial cord

As for III

As for III

As for III

VI

Posterior cord

Abductionb Wrist and finger extension Thumb abduction

M4–5 M3–5 M3–5

M3 M3 Mc

Note: Lowest limitations, according to functional priorities, are as follows: aabduction innervated by the axillary nerve or suprascapular nerve, or both; babduction innervated by the axillary nerve; cmotor outcome irrelevant for a satisfactory result.

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Outcomes in the Repair of Nerve Injuries Table 11.13 Grading of outcomes for peripheral nerves of the upper extremity (lowest limits) Outcome

Median nerve

Ulnar nerve

Radial nerve

Musculocutaneous nerve

Axillary nerve

High

Low

High

Low

Excellent

M4–5 all muscles S4

M5 hand S4

M4–5 all muscles S4

M3 hand S4

M4–5 all muscles

M5 biceps

M5 deltoid

Good

M4–5 forearm M3 hand S3–4

M4 hand S3

M4–5 forearm M3 hand S3–4

M4 hand S3

M4–5 all muscles but M3 of thumb abduction

M45 biceps

M4–5 deltoid

Satisfactory

M3 forearm M0–3 hand S2

M3 hand S2

M3 forearm M3 hand S2

M3 hand S2

M3 all muscles but M0–3 of thumb abduction

M3 biceps

M3 deltoid

Poor

M0–2 all muscles S0–1

M0–2 hand S0–1

M0–2 all muscles S0–1

M0–2 hand S0–1

M0–2 all muscles

M0–2 biceps

M0–2 deltoid

Table 11.14 Percentage of useful sensorimotor recovery after nerve graft repairs of the upper extremity (meta-analysis data) Repaired nerve

Height of repair

Useful motor recovery (%)

Useful sensory recovery (%)

Median

Proximal

40.1

61.7

Distal

67.3

71.9

Ulnar

Proximal

35.0

66.0

Distal

66.4

72.8

Radial

Proximal

75.5

–

Distal

90.7

–

Musculocutaneous

All levels

87.1

–

Axillary

All levels

79.4

–

results, though current reports on ulnar nerve repairs are more optimistic than in the past.

11.2.2 Lower Extremity Repairs The peroneal and tibial components should be evaluated separately after sciatic nerve repairs. Generally, the tibial division has exhibited the greater potential for recovery, even when lengthy grafts are necessary. Significant recovery appears to be more difficult to achieve with the peroneal division, with data showing an average of only 36% of patients reaching grade M3 or higher after suturing or graft repair.8,9 Motor function has been classified into six grades, from M0 to M5, using Highet’s clinical scale. Sensory function was classified into five grades, from S0 to S4 (anesthesia, dysesthesia, protective sensation, and two-point discrimination above and below 10 mm). Patients experiencing grade M3 recovery of plantar or dorsal flexors of the foot and S2 sensory function were considered to have had useful functional recovery of the corresponding division. The results of surgery for the sciatic nerve complex were classified according to functional priorities (▶ Table 11.15).

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Protective sensation is the first priority of surgical repair. A second complication that must be addressed is foot drop with an equinovarus deformity. Since adequate functional improvement of the muscles innervated by the peroneal nerve is rare, the second functional priority of restoration is plantar flexion. Recovery of plantar flexors is essential to using an orthopaedic device or even the restoration of active movements in the ankle joint by anterior transfer of the tibialis posterior tendon. These two functions may be established by repairing the tibial division. Therefore, the best results can be obtained by successful nerve repair or grafting. In this case, even partial improvement may prevent contact sores; and with a limited palliative procedure, this yields a good result. Finally, a retarded vasomotor response with cyanosis and discomfort when the leg is in a vertical position is another important complication, for which functional restoration is a priority. The results reported for the largest series on sciatic nerve repairs, published by Kim and Murovic in 2008,13 are similar to those reported by Samardzic et al.9 The corresponding rates of recovery, listed by surgical procedure (neurolysis, split repair, grafting), were 74.3, 58.9, and

Outcomes in the Repair of Nerve Injuries Table 11.15 Grading of outcome for peripheral nerves of the lower extremity (lowest limits) Outcome

Peroneal nerve

Tibial nervea

Femoral nerve

Sciatic nerve

Excellent

M4–5 all muscles S2

M4–5 all muscles S3–4

M5 quadriceps

Good VMF T4 P2

Good

M4–5 tibialis ant. peroneal group M3 finger extension S2

M4–5 triceps sure M3 tibialis post., finger flexion S3

M4 quadriceps

Good VMF T3 P1 (tendon transfer)

Satisfactory

M3 tibialis ant. peroneal group M0–2 finger extension S2

M3 triceps sure M0–2 tibialis post., finger flexion S2

M3 quadriceps

Good VMF T2 P1 (orthopaedic aid)

Poor

M0–2 all muscles S0–1

M0–2 all muscles S0–1

M0–2 quadriceps

Poor VMF T1 P1

Abbreviations: P, peroneus; T, tibialis; VMF, vasomotor function. aGrading

is only for lesions below Poupart’s ligament.

Table 11.16 Scoring of sensory recovery as recommended by the British Medical Research Council Sensory recoverya S0

Absence of sensation

S1

Recovery of deep cutaneous pain sensation

S2

Return of some degree of superficial pain and tactile sensation

S2 +

Same as Stage S2, with slight additional hyperresponsiveness

S3

Further recovery of pain and tactile sensation, with no dysesthesia

S3 +

Same as Stage 3, with the addition of some two-point discrimination

S4 aThe

Complete recovery sensation should be tested in the autonomous zone of a nerve, where there is minimal overlap from adjacent nerves.

36% for the peroneal nerve and 90.9, 87.5, and 72.7% for the tibial nerve, respectively. However, results were significantly different for the buttocks and thigh. Excluding neurolysis, the difference was approximately 20% for the individual components. As could be expected, the rates of recovery for nerve grafting were lower: 24.3 and 44.9%, respectively. Therefore, this procedure is no less than questionable at the buttock level. Our own corresponding rates of recovery, again by surgical procedure, were 73.3, 63.6, and 33% for the peroneal nerve, and 93.7, 93.3, and 71.4% for the tibial nerve (▶ Table 11.16).

References [1] Seddon H. Surgical Disorders of the Peripheral Nerves. 1st ed. New York, NY: Churchill Livingstone; 1975 [2] Roganovic Z. Repair of traumatic peripheral nerve lesions: operative outcome. In: Siqueira MG, Sokolovsky M, Malessy M, Devi I, eds. Treatment of Peripheral Nerve Lesions. Bangalore: Prism Books Pvt Ltd; 2011:111–120 [3] Roganovic Z, Pavlicevic G. Difference in recovery potential of peripheral nerves after graft repairs. Neurosurgery. 2006; 59(3):621–633, discussion 621–633 [4] Kline DG. Grading results. In: Kim DH, Midha R, Murovic JA, Spinner RJ, eds. Kline and Hudson’s Nerve Injuries. 2nd ed. Philadelphia, PA: Saunders; 2008:65–74

[5] Paternostro-Sluga T, Grim-Stieger M, Posch M, et al. Reliability and validity of the Medical Research Council (MRC) scale and a modified scale for testing muscle strength in patients with radial palsy. J Rehabil Med. 2008; 40(8):665–671 [6] Highet WB. Grading of Motor and Sensory Recovery in Nerve Injuries. Report to the Medical Research Council. London: Her Majesty’s Stationary Office; 1954 [7] Medical Research Council. Aids to Examination of the Peripheral Nervous System. Memorandum No. 45. London: Her Majesty’s Stationery Office; 1976 [8] Samardzic M, Rasulić L. Repair of traumatic peripheral nerve lesions: operative outcome after repair of complex nerve structures. In: Siqueira MG, Socolovsky M, Malessy M, Devi I, eds. Treatment of Peripheral Nerve Lesions. Bangalore: Prism Books Pvt Ltd; 2011:121– 126 [9] Samardzic MM, Rasulić LG, Vucković CD. Missile injuries of the sciatic nerve. Injury. 1999; 30(1):15–20 [10] Samardzic M, Rasulić L, Grujicić D, Milicić B. Results of nerve transfers to the musculocutaneous and axillary nerves. Neurosurgery. 2000; 46(1):93–101, discussion 101–103 [11] Millesi H, Meissl G, Berger A. Further experience with interfascicular grafting of the median, ulnar, and radial nerves. J Bone Joint Surg Am. 1976; 58(2):209–218 [12] Kim D. Gunshot wounds to the brachial plexus. In: Kim D, Midha R, Murovic JA, Spiner R, eds. Kline and Hudsons: Nerve Injuries. Philadelphia, PA: Saunders; 2008:313–323 [13] Kim D. Murovic JA. Lower extremity nerve: sciatic nerve injuries. In: Kim D, Midha R, Murovic JA, Spiner R, eds. Kline and Hudsons: Nerve Injuries. Philadelphia, PA: Saunders; 2008:209–225

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Gunshot and Other Missile Wounds to the Peripheral Nerves

12 Gunshot and Other Missile Wounds to the Peripheral Nerves Miroslav Samardzic and Lukas Rasulic Abstract Gunshot or other missile injuries to the peripheral nerves, and especially the brachial plexus, present a specific problem with respect to their clinical and morphological characteristics, indications and timing of surgery, and prognosis. Furthermore, missile injuries to the brachial plexus are difficult to explore and treat because of its complex anatomy, including the proximity of great vessels and their possible injury, which increases the risks of surgery. In the majority of cases, these injuries produce lesions-in-continuity with incomplete functional loss and the potential for spontaneous recovery. Therefore, surgery should usually be postponed for 2 to 4 months after injury. After this time, surgery is indicated if there has been no or only partial functional recovery, or if recovery plateaus over this period. In cases of missile injury to the lower brachial plexus elements and peroneal division of the sciatic nerve, and particularly in patients with an extended nerve defect, the rationale for surgery is unclear. This chapter summarizes experiences from extensive wartime and civilian practice series. Keywords: brachial plexus, gunshot injury, missile injuries, peripheral nerve

12.1 Introduction Missile injuries to the brachial plexus and peripheral nerves may be produced by both low- and high-velocity missiles. Low-velocity missile (less than 700 m/s) injuries are caused by hand guns, revolvers, and shell fragments (for which the velocity is generally around 300 m/s), although some authors exclude the last of these three. In such cases, nerve elements are damaged by small shock waves, by temporary cavitation, and sometimes by direct impact. Thus, the lesions are largely neurapraxia, and spontaneous recovery can take place, even in patients with severe neurologic deficits at presentation, unless the nerve is transected by direct impact.1,2,3,4,5,6 These lesions are characteristic of older military series7,8 and civilian practice.4 On the other hand, high-velocity missile (with velocities over 700 m/s, averaging 1,000 m/s) injuries, produced by modern rifles or machine guns, cause more extensive damage. The destructive effects of these projectiles depend on the amount of energy that is released, which in turn is determined by the mass, velocity, and angle of incidence of the bullet. Nerve elements are rarely injured by direct impact; rather, these injuries are most

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often attributable to shock waves and cavitation that cause them to be compressed and stretched.9,10 These extensive injuries also involve soft tissues, blood vessels, and bones. Nerve structures, all or only in part, may be damaged outside the projectile path, at the longer nerve segment or at multiple levels.1,9 Furthermore, different degrees of injury usually coexist, and spontaneous recovery may or may not occur. In recent wars, the effects of blast explosions from improvised explosive devices are often devastating to the whole extremity, including the nerves.11 The first large series of brachial plexus injuries were reported by Brooks in 19547 and Nulsen and Slade in 1956.8 Thereafter, no large series were published for about 30 years, until the reports made by Kline and Judice in 19835 and Kline in 1989,4 who analyzed injuries in civilian practices. Generally, gunshot wounds to the brachial plexus are infrequent in civilian practice, such that there have been only few large series published over the past two decades.2,3,12 However, in recent military conflicts, these injuries constituted 2.6 to 14% of all peripheral nerve injuries.13,14 The largest surgical series on peripheral nerve missile injuries have been based on war practice. In 1924, Delageniere15 published his experiences from World War I among 375 surgically treated penetrating injuries (mostly gunshot injuries to the peripheral nerves). Pollock and Davis16 reviewed their cumulative experiences with 397 cases from the same war.16 After World War II, Seddon reported on the British experience with 699 missile nerve injuries, 8.6% of which were treated with nerve grafts,17 while Woodhal and Beebe reported on American experiences with 3,656 nerve injuries, but only 30 grafting procedures.18 Thereafter, there were no large series on this subject until the Vietnam War. At that time, Omer published a series of 917 injuries involving the upper extremity peripheral nerves, 753 (66.6%) of which were gunshot wounds, including 269 surgically treated nerves.19 Similar experiences, with 135 nerve injuries operated on during the Vietnam War, were reported by Brown.20 Somewhat later, Samardzic et al reported a series of 90 missile injuries involving upper arm peripheral nerves operated upon during the war which took place within the former country of Yugoslavia.21 Kline and Hudson also published their series of 64 surgically treated gunshot injuries from civilian practice.22 Few reports have detailed the incidence and results of the surgical management of sciatic nerve injuries.22,23,24,25,26 Published opinions based on World War II experiences generally were very pessimistic and led to the conclusion that

Gunshot and Other Missile Wounds to the Peripheral Nerves nerve reconstruction should not be recommended, given that foot drop could be managed via tendon transfers, arthrodesis, or orthotic support.5 Similarly, Seddon reported his experiences and concluded that there was no need to repair severe nerve lesions with lost substance.25 However, a number of recent papers23,26 have challenged this traditional approach, particularly one paper that described a series of 324 patients with sciatic nerve lesions, including surgically managed gunshot wounds that affected 43 tibial and 42 peroneal divisions.22 As stated previously, the largest series of missile injuries to the peripheral nerves were drawn from war practice.15,16,17,18,19,20 However, these series are difficult to evaluate and compare, because they include heterogeneous patient populations, especially regarding the characteristics of the nerve lesions, timing of surgery, and surgical techniques used. It should be remembered that magnification, delicate instruments, and less reactive suture materials only became available for use during the Vietnam War.19 Techniques such as interfascicular nerve and modified cable grafting also were not used at that time. Gunshot wounds to the brachial plexus are technically difficult to explore and treat, since the anatomy is complex, including great vessels that are close to the nerve elements, such that intraoperative vascular injury is a genuine risk during surgery. However, recently, there have been considerable advances in this respect, owing to improved preoperative evaluations, intraoperative monitoring, and nerve repair techniques.

12.2 Clinical Characteristics 12.2.1 Brachial Plexus Older reports used to emphasize partial neurologic deficits in large numbers of patients, with the potential for spontaneous recovery, especially in the upper trunk and posterior cord, but not with injuries affecting the lower elements.7,8 In the first published series that Brooks reviewed, only 31.8% of 170 patients with open injuries were operated upon.7 Nulsen and Slade reported a larger number of operated-upon patients, 76% of their selected case group.8 Kline reported similar clinical characteristics in his series.4 Complete or nearly complete functional loss in the distribution of all nerve elements at the injured level was present in only 19 patients (21%). Kline operated on 63.8% of his patients and stated that complete injury to one element could recover spontaneously, but often did not. Meanwhile, incomplete functional loss in the distribution of one element usually recovered spontaneously; but this did not guarantee that other elements would experience the same recovery. In recent years, it has been appreciated that many missile injuries to the brachial plexus do not recover spontaneously; many, in fact, cause persistent pain and

severe disability, even though lesions-in-continuity are common.1,11,27 Most of these lesions are associated with complete functional loss.3,6 Kim et al documented complete loss of function in 69% of the nerve elements, which was clearly contradictory to older reports.3 Moreover, Samardzic et al registered complete functional loss in the distribution of all brachial elements in 62.9% of patients, with spontaneous recovery noted only in 16.6%.9 A significant number of patients with upper trunk and posterior cord injuries who present with only partial neurologic deficits will recover spontaneously, but not those with injury to the lower elements.10 Patients exhibiting signs of spontaneous recovery over the first 4 weeks are likely to have a good or excellent outcome.27 It should be emphasized that lesions-in-continuity, with functionally and electromyographically complete loss persisting for 3 months after injury, displayed nerve impulse transmission in 23% of the elements, which meant that neurolysis was indicated as the surgical method of choice.28 Lesions affecting multiple levels of the brachial plexus are common, and will never recover spontaneously.1

12.2.2 Peripheral Nerves Spontaneous recovery may also occur in a significant number of peripheral nerve missile injuries, though this recovery can be delayed for up to 11 months.29 Interestingly, the noted rates of spontaneous recovery were similar in the retrospective studies for World War I, World War II, and Vietnam War missile injuries, ranging from 67 to 69% of cases.

12.3 Characteristics of Nerve Lesions 12.3.1 Brachial Plexus In previously published series,4,5,7,8 a large majority of brachial plexus lesions preserved some nerve continuity. Brooks identified division of some neural elements in 29.6% of his patients who underwent surgical repair.7 Meanwhile, Kline noted that 46.6% of the nerve elements had complete functional loss without any continuity.4 Lesions-in-continuity were detected in 221 elements, among which 75% exhibited complete functional loss. Among nerve elements with incomplete loss, only seven required nerve repair. Conversely, studies on intraoperative nerve action potentials confirmed signs of early regeneration in 48 of these elements (28.9%), and only neurolysis or a split repair had to be performed. Samardzic et al reported that 23.9% of the nerve elements lacked any continuity and, consequently, were associated with complete functional loss.9 Among the remaining nerve elements, 15.3% were preserved but compressed by an external scar, and 60.8% had lesions-in-continuity

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Gunshot and Other Missile Wounds to the Peripheral Nerves (fibrosis, a neuroma-in-continuity, or partial loss of continuity). Recent series have confirmed the predominance of nerve lesions-in-continuity.3,6,14,27,28 Gunshot wounds to this region may also injure the neighboring vessels (e.g., axillary and subclavian arteries and veins), bones (e.g., clavicle, scapula, humerus, ribs), and viscera (e.g., lung, pharynx, esophagus).6 Generally, there is a high incidence of associated injuries. The most frequent injuries are vascular, which are apparent in over 30% of patients. These vascular injuries are of two types.27 The first results in major vascular interruption, while the second is manifested as a pseudoaneurysm, which is often difficult to diagnose and treat.12 Bone fractures increase the risk of nerve damage since the shattered bone fragments become secondary projectiles and travel in almost all directions, causing extraneous damage to surrounding tissues.1,6

12.3.2 Peripheral Nerves The radial nerve was the most commonly injured peripheral nerve in World Wars I and II.16,17,18 Injuries were otherwise equally distributed among the rest of the upper extremity nerves.19,20,21 It should be noted that, in 26% of all patients, and in 32% of those with injuries to upper extremity nerves, there were multiple injuries that involved two or even three nerves.21 Proximal injuries predominate in all of the published series. Preserved nerve continuity was noted in roughly one-third of surgically treated cases from the Vietnam War19,29 and in the majority of cases drawn from civilian practice.22 In the series reported by Samardzic et al,21 nerve continuity was preserved at least partially in almost one-third of patients, as well. For the large majority of nerve transections, surgeons performed nerve grafting, with 40% of the nerve grafts over 6 cm in length. Direct nerve suturing was possible in only two instances. Factors contributing to the partial extent of sciatic nerve injuries include the large size of the nerve and the existence of two separate divisions. In the series reported by Samardzic et al,24 nerve continuity was preserved at least partially in 76.4% of sciatic nerve injuries and in 25.4% of patients with a neuroma-in-continuity or fibrotic changes, with preserved fascicular patterns for both divisions. Finally, in 51% of partially transected nerves, one of the divisions was completely preserved in roughly one-third of cases.24 There was no significant difference in the extent of injury between gunshot and shell fragment wounds.24 Regarding the total number of injured divisions, 40.1% of divisions were completely transected, 24.5% were partially transected, and 35.4% had preserved continuity.24 In the series published by Kline and Hudson, preserved continuity was identified in approximately half of the divisions, but they provided no data on the extent of transections. This variety in anatomical lesions may cause complete or, in many instances, partial functional loss that may improve spontaneously.22

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Samardzic et al24 registered partial functional loss in only 13.3% of their patients, while additional functional improvement was observed in another 7.3%. However, this partially preserved function involved either motor or sensory function, or only some of the muscles, and rarely exceeded M2 or S2 in terms of the ultimate functional grade attained.21

12.4 Indications for and Timing of Surgery If there is a clean aseptic wound, a stable bone fracture, and skin closure over neurovascular structures, there are few reasons why surgery cannot be delayed.6 Other reasons to delay surgery that pertain to the affected nerve elements themselves include difficulty evaluating the extent of nerve damage and the potential for spontaneous recovery.9,10 Generally, an operation is indicated if, at the time of follow-up clinical examination: there has been no recovery; there is nonanatomic recovery in distal but not proximal muscles; or there is a complete functional loss in the distribution of one or more nerve elements that has persisted for at least 3 months, a period that should permit spontaneous recovery from the first three grades of injury.3,8,24,27 Association with vascular injuries may warrant emergent surgery. Otherwise, the question arises as to whether brachial plexus repair should be attempted or not. In most instances, it is much better to perform secondary repair of nerve injuries.1,30 Early exploration and nerve repair within the first 3 months are indicated in cases with progressive neurologic deficits because of an aneurysm or arteriovenous fistula, or in cases with noncausalgic pain that proves resistant to conservative treatment, especially if bullet or bone fragments are present.31 If lost nerve continuity is documented upon early exploration, early secondary repair is indicated.9 It should be mentioned that, in these cases and in those with a proximal nerve stump that is either fibrotic or unavailable for grafting, there is the potential for performing nerve transfers.1,28 Surgery can be delayed for up to 6 months with no unfavorable effect on outcomes. Within this period of time, earlier repair is indicated if: there is no evidence of anatomic recovery or such recovery plateaus over the first few months; there is dissociated recovery, with a discrepancy between motor and sensory functional improvement; or there is uneven functional recovery with regular chronology but the absence of improvement in certain muscles.9,10,24 Operative results have been proven to decline if surgery is delayed for more than 1 year.4,5,9,10,21,24 Adult patients with lesions affecting the C8 and T1 spinal nerves, lower trunk, and medial cord and its outflows— especially the ulnar nerve—as well as the sciatic nerve are suited for conservative treatment unless associated pain is intolerable and resistant to medication.10,21,24 Repairing sciatic nerve lesions that are accompanied by the loss of substance was not recommended previously,

Gunshot and Other Missile Wounds to the Peripheral Nerves because of the poor prognosis, risk of increased pain after operation, and potential for spontaneous recovery. One additional reason was that, following complete transection of the sciatic nerve, the patient still has control of the knee joint, owing to the preserved hamstring branch, and is thereby able to walk using an orthotic to support the foot and ankle.23,25,31 The main complication of such injuries is the loss of sensation over the sole, which can lead to trophic ulcer formation. Consequently, restoring sensory function is the priority of surgical repair. A second major complication is foot drop, with an equinovarus deformity. Since adequate functional improvement of the muscles innervated by the peroneal nerve is rare, the second functional priority for restoration is plantar flexion. Recovery of the plantar flexors is essential to using an orthotic device and even to the restoration of active movements in the ankle joint by anterior transfer of the tibialis posterior tendon. These two functions may be restored by repairing the tibial division. Therefore, the best results can be obtained by its successful nerve repair or grafting.21 In such cases, even partial improvement may prevent pressure sores and, with a limited palliative procedure, yield a good result.26 A final important complication of sciatic nerve injuries that is a priority of surgical repair is a retarded vasomotor response, characterized by cyanosis and discomfort when the leg is in a vertical position.

12.5 Results and Prognosis 12.5.1 Brachial Plexus On the basis of obtained results, Brooks7 concluded that surgery for gunshot wounds to the brachial plexus was “rarely profitable and justifiable,” because recovery occurred only after upper trunk or C5 and C6 spinal nerve suture. Neurolysis of the other elements provided some pain relief, but rarely enhanced the functional outcome. Nulsen and Slade8 made similar observations. In their experience, recovery occurred after suturing the upper spinal nerves and trunk, and in the proximal muscles after repair of the lateral and posterior cord. Surgical repair of the lower elements and grafting procedures were not successful. Meanwhile, Kline and Hudson22 obtained useful functional recovery in 92% of patients treated with neurolysis. The rate of recovery for elements thought to have a favorable prognosis was 96%; for those with an unfavorable prognosis, it was much lower, at 79%. Direct suture overall yielded a recovery rate of 69%, while nerve grafting was successful in just 54% of patients. The results of nerve repair have been especially favorable for the upper spinal nerves, upper trunk, and the lateral and posterior cords and their nerves, together having an overall rate of recovery of 83% with direct sutures and 66% with nerve grafting, ranging from 50 to 100%

depending on the different nerve segments. Repair of the C7 spinal nerve and middle trunk was associated with a 45% recovery rate after grafting. As far as the lower spinal nerves, lower trunk, and medial cord are concerned, only medial cord to median nerve repairs generated useful recovery, which amounted to 66.6% with direct suturing and 53% with a nerve graft. Citing these results, Kline and Hudson22 concluded that nerve repair of brachial plexus injuries caused by gunshot wounds not only was possible, but also produced acceptable results. They further concluded that end-to-end repairs were usually, though not always, possible. More recent reports have confirmed their beliefs. For example, rates of recovery obtained by neurolysis have ranged from 90 to 94%,9,14,32 with failures mostly attributed to lesions involving the lower trunk or the ulnar or radial nerve.31 Results were especially good if the nerve element was compressed by scar or there was a neuroma-in-continuity.10 Approximately 70% of the lesions repaired by direct suture experienced successful functional recovery.2 Secer et al,10 meanwhile, obtained functional recovery only 36.6% of the time with direct sutures and 56.5% of the time using partial direct sutures. Nerve grafting was performed for lesions with lost continuity, whether total or partial, and for lesions-in-continuity without transmission of nerve action potentials.4,31 The techniques used were interfascicular nerve grafting for split-nerve repairs, and the same technique or modified cable nerve grafting for complete nerve transections.9 The reported rates of recovery ranged from 70 to 89%,1,9,14,32 although Secer et al10 reported a total rate of recovery of only 16.6%. Some of the factors portending favorable results included the use of short nerve grafts,9 using a significant number of split-nerve repairs,4,9 and surgery performed within the first 3 months of injury. However, the most important determinant of outcome was performing nerve grafts for elements thought to have a favorable prognosis, such as the C5, C6, and possibly C7 spinal nerves, upper trunk, lateral and posterior cords, and musculocutaneous and axillary nerve.1,9,10,14,32 This has been especially true with infraclavicular lesions involving the lateral cord and musculocutaneous nerve, because the target muscles are closer than in other situations.30 Neurolysis and repair of the lower nerve elements— including the C8 and T1 spinal nerves, lower trunk, medial cord, and ulnar nerve—rarely result in functional improvement.9,10,14 However, such repair can help with pain relief.10 This being said, Siqueira et al30 obtained reinnervation of the wrist and digital flexors in 50 to 60% of patients without reinnervating the intrinsic muscles of the hand. Sensory restoration throughout the area innervated by the median nerve was achieved in 70 to 80%.6,30 Noncausalgic pain may be related to partial transections, especially with lower-level lesions, or to compression by scar. This pain responds well to both external and internal neurolysis.1

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12.5.2 Peripheral Nerves Citing his series from World War I, Delageniere15 concluded that the overall results in his 113 patients treated via neurolysis were not good; on the other hand, 122 of 142 (85.9%) sutures were completely successful, while 16 were partial successes and there were only 4 failures. Pollock and Davis16 reported a success rate of 72% for radial, 69% for median, and 57% for ulnar nerve repairs. The use of nerve grafts was largely unsuccessful throughout this period. Reviewing British experiences from World War II, Seddon17 claimed that radial nerve injuries generally had more satisfactory outcomes than either median or ulnar nerve injuries. He noted that 36.9% of his 114 radial nerve repairs achieved grade M4–M5 strength. Furthermore, he noted that only 8.6% of median nerve injuries achieved a satisfactory level of sensory function, while just 4.9% of ulnar nerve injuries attained satisfactory motor function. Similar findings were documented by Woodhal and Beebe,18 who noted good motor function in just 21.3% of 127 radial nerve repairs. Poor results with nerve grafting during World War II were largely attributed to the severity of nerve injuries, associated with large nerve gaps, and to the use of trunk graft techniques without magnification. However, Seddon17 reported the successful use of cable grafts for median nerve injuries. He noted motor recovery to grade M3–M4 in 54% and sensory recovery to S3–S3 + in 63% following median nerve grafting procedures. For the largest series of nerve injuries from the Vietnam War, Omer19 reported a total rate of recovery of 55% with external neurolysis, including 37.5% for highvelocity and 76.2% for low-velocity gunshot wounds. Additionally, he noted a total rate of recovery of 25% in cases with epineural sutures, 20% for high-velocity and 31.2% for low-velocity gunshots. Approximately 75% of the successful nerve sutures were performed between 3 and 6 months after the injury, and 80% of the patients were 20 years old or younger. Clinically significant function was not observed after any of the 19 nerve graft procedures. The techniques used included multiple cable grafts and two pedicle grafts. Omer concluded that there was no significant difference between the outcomes with the repair of gunshot nerve injuries during World War II and those of his own series. The high incidence of failures was attributed to the overall condition of the extremity, the severity and level of nerve injury, and delayed surgery. Similar results with nerve sutures were reported by Brown,20 with corresponding rates of recovery for the ulnar nerve of 35%, for the median nerve of 50%, and for the radial nerve of 40%. Reporting their cumulative experiences with gunshot wounds to the peripheral nerves from civilian practice, Kline and Hudson22 noted individual rates of recovery of 92.8% for radial, 89.2% for median, 64% for ulnar, and 80%

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for peroneal nerve injuries, if all levels of injury and all surgical procedures were included. Failures were mostly related to nerve grafting procedures and extensive nerve defects. Additionally, Kline and Hudson22 noted recovery with peroneal nerve injuries following 43.8% of their graft procedures. In this series, patients achieving a lower level of M3-level strength were graded as having experienced useful recovery. Differences in the results achieved with nerve grafting for gunshot wounds versus clean transections might be attributed to the extensive and high-located nerve injuries, as well as the extra surgical delay that is predominant in the first group. Furthermore, it should be remembered that the series of gunshot wounds reported by Samardzic et al9 also included the results of nerve grafting for peroneal nerve injuries, which have exhibited the lowest rate of recovery in all series. In 1972, Kline published a series of 13 patients with gunshot wounds to the sciatic nerve. Functional improvement (without detailed gradations) was obtained in all neurolysis cases for both divisions, in all sutured tibial divisions, and in two-thirds of sutured peroneal divisions.31 Likewise, Seddon in 1975 analyzed a series of 329 patients, including 132 for whom some form of surgical repair had been performed. He obtained useful functional recovery (first three grades, according to his classification system) in 64% of cases, but stated that recovery in the long muscles of the leg was usually disappointing, except for the triceps surae.25 Millesi in 1987 published a series of 39 injuries that included 6 injuries secondary to injections. He obtained useful functional recovery, according to his own grading system, in 5 (83.3%) of the 6 patients who underwent neurolysis, in all 13 with combined neurolysis and nerve grafting, and in 10 (71.3%) of 14 who underwent grafting alone.23 Finally, Kline and Hudson published their results of surgery for gunshot wounds affecting 43 tibial and 42 peroneal divisions. They obtained functional recovery of tibial divisions in 93.3 and 69.2% post neurolysis and grafting, respectively, while corresponding rates for the peroneal division were 86.2 and 25%.22 Samardzic et al published a series of 45 patients with missile injuries to the sciatic nerve, in whom they obtained functional recovery in 86.7% for tibial divisions and 53.3% for peroneal divisions.24 The rates of functional recovery, by surgical procedure, were also significantly higher for tibial versus peroneal division repairs. These rates were 93.7 versus 68.7% for neurolysis, 93.3 versus 63.6% for split repairs, and 71.4 versus 33.3% for nerve grafts. Graft failures for the tibial division were related to injuries at the gluteal level. The total rate of recovery across the whole sciatic nerve complex was 86.7%. The rates of recovery following neurolysis and repair of partially transected nerves were similar: 90.9 versus 96.0%. The quality of recovery was better for partial transections if split repairs were performed for both divisions, or if

Gunshot and Other Missile Wounds to the Peripheral Nerves neurolysis for one division was combined with split repair of the other. The rate of recovery following nerve grafting for both divisions was 55%, which is significantly lower than for the other two surgical procedures. It should be emphasized that the final outcome is also influenced greatly by the existence of associated injuries, such as vascular lesions, bone fractures, and soft-tissue defects.3,6 Vascular lesions affect nerve elements through ischemia. Bone fragments can cause additional nerve damage or subsequent callus spread around the repaired nerve.10

12.6 Conclusion Drawing from the experiences of others, we can determine several conclusions: ● In a significant number of patients, gunshot wounds to the brachial plexus and peripheral nerves produce lesions-in-continuity, with either incomplete functional loss, with which spontaneous recovery is possible, or complete loss, with which spontaneous recovery typically does not occur. ● Associated vascular injury is an indication for emergent surgical exploration. ● The potential for spontaneous recovery and difficulties with the initial evaluation of nerve lesions are the main reasons for delaying surgery and nerve repair until 2 to 4 months postinjury. ● After this period, surgery is indicated (1) if there is complete functional loss; (2) if there is incomplete loss that does not improve spontaneously; (3) if recovery plateaus or only partial recovery is evident 6 months after the injury; or (4) if a pseudoaneurysm or fistula is compressing nerve elements. ● Delaying surgery past 1 year is not justifiable. ● Neurolysis yields useful functional recovery for over 90% of lesions with preserved nerve continuity. ● Similar results may be obtained by split repairs and nerve grafting on elements thought to be prognostically favorable—such as the C5 and C6 spinal nerves, the upper trunk, the lateral and posterior cord and their outflows (except the ulnar nerve), and the tibial nerve. ● Nerve grafting has a lower rate of recovery for gunshot wounds than for clean transections, due to the predominance of more extensive and higher-level injuries. ● For injuries affecting lower brachial plexus elements, conservative treatment is usually warranted, except in patients with resistant noncausalgic pain. ● The peroneal division of the sciatic nerve should not be repaired if there is a long nerve defect, especially at the buttock level. The available donor nerves should be saved for reconstruction of the tibial division, which is the priority when the whole sciatic nerve is injured.

References [1] Bhandari PS, Sadhotra LP, Bhargava P, et al. Management of missile injuries of the brachial plexus. Indian J. Neurotrauma. 2006; 3(1):49– 54 [2] Kim DH, Cho YJ, Tiel RL, Kline DG. Outcomes of surgery in 1019 brachial plexus lesions treated at Louisiana State University Health Sciences Center. J Neurosurg. 2003; 98(5):1005–1016 [3] Kim DH, Murovic JA, Tiel RL, Kline DG. Penetrating injuries due to gunshot wounds involving the brachial plexus. Neurosurg Focus. 2004; 16(5):E3 [4] Kline DG. Civilian gunshot wounds to the brachial plexus. J Neurosurg. 1989; 70(2):166–174 [5] Kline DG, Judice DJ. Operative management of selected brachial plexus lesions. J Neurosurg. 1983; 58(5):631–649 [6] Secer HI, Daneyemez M, Tehli O, Gonul E, Izci Y. The clinical, electrophysiologic, and surgical characteristics of peripheral nerve injuries caused by gunshot wounds in adults: a 40-year experience. Surg Neurol. 2008; 69(2):143–152, discussion 152 [7] Brooks DM. Open wounds of the brachial plexus. In: Seddon HJ, ed. Peripheral Nerve Injuries, Medical Research Council Special Report Series. London: Her Majesty’s Stationery Office; 1954 [8] Nulsen FE, Slade WW. Recovery following injury to the brachial plexus. In: Woodhal B, Beebe GW, eds. Peripheral Nerve Regeneration: A Follow-Up Study of 3656 World War II Injuries. Washington, DC: Government Printing Office; 1956:389–408 [9] Samardzic MM, Rasulic LG, Grujicic DM. Gunshot injuries to the brachial plexus. J Trauma. 1997; 43(4):645–649 [10] Secer HI, Solmaz I, Anik I, et al. Surgical outcomes of the brachial plexus lesions caused by gunshot wounds in adults. J Brachial Plex Peripher Nerve Inj. 2009; 4:11 [11] Birch RM, Stewart MPM, Eadley WEP. War and gunshot wound injuries of the peripheral nerves. In: Tubbs S, Rizk E, Shoja M, Loukas M, Barbaro N, Spinner R, eds. Nerve and Nerve Injuries. Vol. 2. Amsterdam: Elsevier; 2015:629–653 [12] Kim DH, Murovic JA, Tiel RL, Kline DG. Gunshot wounds involving the brachial plexus: surgical techniques and outcomes. J Reconstr Microsurg. 2006; 22(2):67–72 [13] Gousheh J. The treatment of war injuries of the brachial plexus. J Hand Surg Am. 1995; 20(3, Pt 2):S68–S76 [14] Stewart MP, Birch R. Penetrating missile injuries of the brachial plexus. J Bone Joint Surg Br. 2001; 83(4):517–524 [15] Delageniere H. A contribution to the study of the surgical repair of peripheral nerves. Surg Gynecol Obstet. 1924; 39:543–553 [16] Pollock LJ, Davis L. Peripheral nerve injuries. Am J Surg. 1932; 15: 179–217 [17] Seddon H. Nerve grafting and other unusual forms of nerve repair. In: Seddon H, ed. Peripheral Nerve Injuries, Medical Research Council Special Report, No 282. London: Her Majesty’s Stationery Office; 1954:389–417 [18] Woodhal B, Beebe GW. Peripheral Nerve Regeneration: A Follow-up Study of 3656 World War II Injuries. Veterans Administration, Medical Monograph. Washington, DC: US Government Printing Office; 1956 [19] Omer GE, Jr. Injuries to nerves of the upper extremity. J Bone Joint Surg Am. 1974; 56(8):1615–1624 [20] Brown PW. The time factor in surgery of upper-extremity peripheral nerve injury. Clin Orthop Relat Res. 1970; 68(68):14–21 [21] Samardzic MM, Rasulic LG, Antunovic V, Grujicic DM. Missile injuries to the peripheral nerves. Eur J Emerg Surg Intensive Care. 1998; 21: 173–178 [22] Kline DG, Hudson A. Nerve Injuries. Philadelphia, PA: Saunders; 1995 [23] Millesi H. Lower extremity nerve lesions. In: Terzis JK, ed. Microreconstruction of Nerve Injuries. Philadelphia, PA: Saunders; 1987: 239–251 [24] Samardzic MM, Rasulić LG, Vucković CD. Missile injuries of the sciatic nerve. Injury. 1999; 30(1):15–20

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Gunshot and Other Missile Wounds to the Peripheral Nerves [25] Seddon H. Surgical Disorders of the Peripheral Nerves. 2nd ed. Edinburgh: Churchill Livingstone; 1975 [26] Sedel L. Surgical management of the lower extremity nerve lesions (clinical evaluation, surgical technique, results). In: Terzis JK, ed. Microreconstruction of Nerve Injuries. Philadelphia, PA: Saunders; 1987:253–265 [27] Vrettos BC, Rochkind S, Boome RS. Low velocity gun shot wounds of the brachial plexus. J Hand Surg [Br]. 1995; 20(2):212–214 [28] Kline DG, Tiel RL. Direct plexus repair by grafts supplemented by nerve transfers. Hand Clin. 2005; 21(1):55–69, vi

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[29] Omer G. Nerve injuries associated with gunshot wounds of the extremities. In: Gelberman RH, ed. Operative Nerve Repair and Reconstruction. Vol. 1. Philadelphia, PA: Lippincott; 1991:655–670 [30] Siqueira MG, Martins RS. Surgical treatment of adult traumatic brachial plexus injuries: an overview. Arq Neuropsiquiatr. 2011; 69 (3):528–535 [31] Kline DG. Operative management of major nerve lesions of the lower extremity. Surg Clin North Am. 1972; 52(5):1247–1265 [32] Samadian M, Rezaee O, Haddadian K, et al. Gunshot injuries to the brachial plexus during wartime. Br J Neurosurg. 2009; 23(2):165–169

Compressive Lesions of the Upper Limb

13 Compressive Lesions of the Upper Limb Gregor Antoniadis and Christine Brand Abstract Compressive lesions of the upper limb are widespread diseases. The most common entrapment neuropathy is the carpal tunnel syndrome, followed by ulnar nerve entrapment at the elbow. Rare entrapment neuropathies are the pronator teres syndrome and suprascapular nerve entrapment at the upper limb. Direct pressure on peripheral nerves leads to local ischemia, caused by reduced blood flow in the vasa vasorum of the nerve. As a result of chronic pressure, demyelination of the nerve and then scarring occur. Loss of function in late stages is the result of chronic peripheral nerve compression. In most cases, peripheral nerves are entrapped in anatomical bottlenecks. Repetitive motions or a trauma may cause neuropathies. Diagnosis is easily established with the help of medical history and clinical examination in most cases. Electrophysiological testing can confirm the diagnosis. Further diagnostic measures are ultrasound and magnetic resonance imaging (MRI), especially in cases of tumor, ganglion cysts, and trauma. If conservative therapy fails, surgery is an effective procedure. Decompression of the nerve is mostly the treatment of choice. Internal neurolysis is contraindicated by the first procedure. Prognosis is in general good. Poor outcome is mostly the result of incorrect diagnosis, incomplete decompression, or functional loss in late stages.

and palmar hand. The numbness may be intermittent or absent in an early stage, and, with time, symptoms increase. Usually, numbness occurs more frequently during sleep (nocturnal paresthesia)3,4 and disappeared by hand activity. Shaking the hand or rubbing it alleviates the symptoms. In later stages, burning pain occurs in the palmar hand, wrist, and forearm and is a major complain. If CTS is burned out, the patient develops thenar atrophy, weakness of thumb opposition, and persistent numbness with loss of texture discrimination and fine motor skills.5 In neurologic examination, Tinel’s sign (tingling is reproduced by tapping the anterior aspect of the wrist with your fingers) may be positive above the carpal canal. Phalen’s test (wrist flexion test) may be also present. Both tests are less sensitive than the electrodiagnosis.3,6 In most cases, physical examination is specific. To confirm the diagnosis, electrophysiological evaluation is essential.7 In early stages, sensory nerve conduction studies are more sensitive than motor conduction studies.8 Electromyograms (EMGs) are usually not needed.9 Ultrasound imaging is of value in the diagnosis of recurrent CTS10 or to exclude a tumor. Magnetic resonance imaging (MRI) is more expensive and not generally available. It is indicated in special situations.

Keywords: peripheral nerve entrapment syndromes, median nerve entrapment, ulnar nerve entrapment, radial nerve entrapment, suprascapular nerve entrapment

Treatment options range from nonsurgical approaches, including activity modification, nonsteroidal anti-inflammatory medication, splinting (full-time vs. nocturnal), and corticosteroid injections, to surgical decompression of the carpal tunnel using a variety of methods. Conservative management is used for patients with mild symptoms in the absence of neurological deficits. In case of nocturnal paresthesia, volar wrist splints can temporary relieve the symptoms. Steroid injection into the carpal canal can alleviate symptoms; however, it is generally felt to be a temporary treatment. The following circumstances indicate surgical intervention in a timely manner: ● Failure of nonsurgical therapy after a period of 8 weeks to relieve pain and/or progressive motor or sensory deficits.11 ● Neurological deficits such as permanent numbness, weakness, loss of texture discrimination, and fine motor skills. ● Absolute indications for carpal tunnel release include rapidly progressive or acute course.

13.1 Median Nerve 13.1.1 Carpal Tunnel Syndrome Clinical Presentation Carpal tunnel syndrome (CTS) is caused by chronic compression of the median nerve within the carpal tunnel.1 Carpal tunnel is built by carpal bones (scaphoid, trapezium, hamate) and is covered by the flexor retinaculum. Tendons of the flexor pollicis longus, flexor digitorum superficialis and profundus, and the median nerve pass through it. CTS is the most common upper limb nerve entrapment neuropathy. The estimated prevalence of CTS is 6%.2 CTS is much more common in women than men (3–4:1). In gravidity, obesity, and renal dialysis, the incidence is higher than in normal population. Symptoms vary from numbness in the thumb, index, middle, and/or radial half of the ring fingers to pain in the forearm, wrist,

Timing

One year after surgical treatment, patients’ complaints are relieved in almost all cases (90–95%).12 The results correlate with the degree of preoperative deficits and

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Compressive Lesions of the Upper Limb the duration of symptoms. The recurrent rate is low (0.5–2.2%).12,13

Surgical Strategy Surgical carpal tunnel release can be performed under general, regional, or local anesthesia on outpatient basis. Generally, we perform the procedure under local anesthesia on outpatient basis. Exceptional cases are patients under antiplatelet therapy, tumor as a cause of CTS, and recurrent CTS. Open carpal tunnel release is the current gold standard treatment. Endoscopic technique has been developed and in use for over 20 years. Release of the transverse carpal ligament is the aim of both techniques.

Open Carpal Tunnel Release After subcutaneous infiltration with a local anesthetic, a blood pressure cuff is applied to achieve ischemia. Incision is made in the proximal palm between the thenar and hypothenar creases with a total length of 3 to 4 cm (▶ Fig. 13.1). Fatty tissue is removed to exhibit the palmar fascia. At this stage of the surgery, you have to take care of the terminal branches of the palmar cutaneous nerves. The palmar fascia is divided sharply and the transverse carpal ligament is shown distally to the rascetta. Afterward, the entire ligament is divided under direct vision. Additional motor branch decompression is usually not needed. Further manipulation, particularly, internal neurolysis, may result in scar formation and has risk of fascicle damage. No difference in results was reported either after internal neurolysis or after epineurotomy.14 Reapproximation of the sectioned carpal ligament is not recommended. The skin is closed in a simple fashion. At the end of the surgery, the wrist should be bandaged. Splinting is not necessary. A variation of this open technique is called “limited open technique” or “mini-incision.” In this case, the trans-

Fig. 13.1 Skin incision for open surgery. Standard technique (black line), mini-incision (red line).

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verse carpal ligament is divided through a shortened skin incision of about 1.5 to 2 cm. This technique allows limited inspection of the carpal tunnel and may lead to incomplete release of the ligament and iatrogenic nerve lesion by unexperienced surgeons.

Endoscopic Carpal Tunnel Release There are two systems used for endoscopic carpal tunnel release: the Agee single portal technique15 and the Chow dual portal system.16 In comparison to the open technique, results do not differ relating to side effects, complications, and recovery time.17 Contraindications are prior surgery on the palmar hand, tumor, arthritis, or wrist articulation rigidity.

Single-Portal Technique Described by Agee15 The requirements of this technique are the same as for the open technique (decompression performed under local anesthesia, ambulatory care). A tourniquet control is obligatory. Skin incision is made at the ulnar side of the tendon of the palmaris longus with a total length of 1 cm (▶ Fig. 13.2). The palmar fascia is divided and the transverse carpal ligament is visualized through an endoscope, which looks like a pistol (▶ Fig. 13.3). A specially designed blade through the open roof of the trocar is used to transect the ligament from the distal to the proximal end (▶ Fig. 13.4). Visibility may be reduced by fatty tissue.

Two-Portal Technique Described by Chow16,18,19 Release of the transverse carpal ligament is performed under tourniquet control and local anesthesia. Two skin incisions are needed. The first incision is made like the single-portal technique and the second in the palmar hand (▶ Fig. 13.2). The endoscope is inserted from both sides after positioning a slotted cannula from the opposite skin incision (▶ Fig. 13.5). Retrograde blade cuts

Fig. 13.2 Skin incision for endoscopic procedures. Single portal technique (black line), two portal technique (red lines).

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Fig. 13.3 Inserted endoscope for splitting the retinaculum flexorum (Agee’s technique).

Fig. 13.4 Endoscopic view of the retinaculum flexorum (partially divided).

13.1.2 Median Nerve Entrapment at the Elbow Anterior Interosseous Nerve Syndrome (Kiloh–Nevin Syndrome) Clinical Presentation Fig. 13.5 Two-portal technique according to Chow.

the whole length of the ligament until fatty tissue protrudes.

Complications Complications from surgical treatment of CTS must be attributed mainly to poor technique. Complication rate for the endoscopic technique is around 5.6%, meanwhile it is 2.8% for open release.20 The most common cause of failure of carpal tunnel release is incomplete sectioning of the transverse carpal ligament. Damage of motor and sensory branches is rare; however, it can cause severe disability of hand function. The phenomenon of so-called pillar pain is controversial. Patients complain of pain in the palmar hand after surgical treatment. Symptoms usually relieve after 4 to 6 months spontaneously. Complex regional pain syndrome (CRPS I) after surgical treatment is rare. Symptoms are edema, pain, circulatory disturbance, skin changes, and finally functional limitation of hand movement. Rosenbaum and Ochoa described CRPS I in 10 cases out of 7,000 surgeries.21

The anterior interosseous nerve is a motor branch of the median nerve and arises 4 to 8 cm distally to the elbow. It penetrates the anterior interosseous membrane as the last major branch of the median nerve and innervates the pronator quadratus and flexor digitorum profundus to the index and long digits. Typically, patients have a history of acute pain in the elbow and forearm for a few hours, which terminates spontaneously. Corresponding to the nerves distribution, a nerve lesion leads to inability to flex the distal phalanges of the thumb and index finger and/or paralysis of the distal interphalangeal joints of the long finger. Therefore, the patient is unable to form an “O” with their tips of the thumb and index finger (pinch sign) (▶ Fig. 13.6). In addition, weakness of the pronator quadratus occurs. Sensory complaints are missing. Besides a tendon rupture, further differential diagnosis is a Parsonage–Turner syndrome (plexus neuritis). Cases of nerve rotation located within the median nerve trunk or anterior interosseous nerve were described. Electrophysiological testing is of value. Electromyography shows denervation in the muscles supplied by the anterior interosseous nerve. Sensory nerve conduction studies are normal, because this nerve has no primary sensory component. In all these cases, MR neurography

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Fig. 13.7 Skin incision for the interosseous anterior syndrome. Fig. 13.6 Interosseous anterior syndrome with paresis of the flexor pollicis longus and flexor digitorum profundus muscles on the right hand.

of the upper arm and brachial plexus region is recommended.

Timing Decompression of the nerve should be done if conservative treatment has not been successful after 12 weeks22,23,24 and other causes for this pathology are excluded. Seror concluded that surgery should not be considered for a year, as late spontaneous recovery can occur.25 There have also been reports that suggest no difference in outcome between surgical and conservative treatment.26,27

Surgical Strategy Surgery can be performed under general anesthesia and tourniquet control. The skin incision is S-shaped along the radial border of the pronator muscle (▶ Fig. 13.7). Branches of the lateral and medial antebrachial cutaneous nerves must be protected. The lacertus fibrosus should be divided along the median border of the biceps tendon. Struthers’ ligament, if present, should be cut through. The nerve and its branches should be exposed in its course more distally until the flexor superficial arch. Constrictive tissue like fibrous bands should be removed when encountered.

Pronator Teres Syndrome Clinical Presentation Symptoms can be similar to the CTS. Nocturnal paresthesia is usually missing. Patients describe pain in the area of the elbow and proximal forearm aggravated by using the arm (especially in activities where the forearm is subjected to permanent pronation and supination). Sensory complaints are inconsistent. Weakness may occur especially if the anterior interosseous nerve is involved. Tenderness on palpation over the median nerve in the

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proximal forearm can be observed. Spinner described provocative tests to establish the level of compression: in flexion and supination of the forearm against resistance, the pain can be triggered if the compression level occurs at the level of lacertus fibrosus or the Struthers arcade. If pain aggravates while extending the pronated forearm against resistance, the entrapment could occur beneath the pronator teres; and resisted middle finger sublimis flexion suggests compression at the sublimis arch if these resisted movements trigger pain in the proximal forearm.28 Electrophysiological testing may show denervation of the median nerves’ supplied muscles. Highresolution ultrasound can be of value. There are doubts of the real existence of the interosseous anterior and the pronator teres syndrome.

Timing Treatment depends on the severity of the symptoms. Avoiding triggering movements and the use of antiinflammatory medication and splints at the elbow or wrist may be helpful. Surgical treatment is an option if symptoms persist longer than 6 to 8 weeks.

Surgical Strategy The surgical approach is a gentle S-shaped incision in both entrapment syndromes (▶ Fig. 13.7). The antebrachial cutaneous nerve should be treated with care. The median nerve is easily found medial to the tendon of the biceps. The lacertus fibrosus is excised. A possible supracondylar process of the humerus and/or a Struthers ligament should be resected. A high origin of the superficial head of the pronator teres could be responsible for compressing the nerve: in this case, it must be divided. Branches that arise from the medial aspect of the nerve and go into the muscle must be preserved. The next possible compression point is the deep head of the pronator teres on the lateral side of the median nerve, which build

Compressive Lesions of the Upper Limb together with the superficial head a fibrous arch. After resecting this arch, dissection continues along the course of the median nerve. A more distal compression can also occur at an accessory long head of the flexor pollicis longus muscle (Gantzer’s muscle), which must be resected. After releasing all potentially structures, the nerve itself is observed. Pseudoneuromas, increased vascularization, and fibrotic areas may be detected at the compressions side.

13.2 Ulnar Nerve 13.2.1 Ulnar Nerve Entrapment at the Elbow Clinical Presentation The so-called cubital tunnel is a fibro-osseous tunnel whose extension is about 10 cm. It begins approximately 6 cm proximal to the elbow where the ulnar nerve transverses the intermuscular septum from anterior to posterior. Struthers described a ligament between the medial triceps head and the medial intermuscular septum (“Struthers’ arcade”)29,30 as a potential compressive point. Dellon could not verify the existence of this arcade in his explorations.31 As it approaches the elbow, the ulnar nerve is located between the medial epicondyle of the humerus and the olecranon, being bridged by an aponeurosis called Osborne’s ligament (or ligamentum arcuatum).32 In 11% of all cases, a residual anconeus epitrochlearis muscle is identified instead of the Osborne ligament.33 The ulnar nerve transverses the two heads of the flexor carpi ulnaris underneath the deep fascia (submuscular membranes) 5 cm distally. This fascia contains fibrovascular bands, which may also compress the ulnar nerve at this point at the end of the tunnel. A further reason for ulnar nerve entrapment is chronic subluxation or luxation of the ulnar nerve. Cubitus valgus deformity after a humeral fracture may be a cause years prior to the onset of symptoms (tardy ulnar nerve palsy). Rare reasons are tumors or a ganglion cyst (see ▶ Fig. 13.9). Ulnar nerve entrapment at the elbow is the second most common entrapment syndrome.34 Intermittent hypesthesia in the ulnar nerve distribution is the most common initial symptom. Furthermore, patients report of pain in the region of the elbow and forearm as well as shooting pain in the hand and digits. Loss of fine motor skills, such as writing and turning around a key, intrinsic muscle atrophy, and weakness occur on later stages. Positive Froment’s sign35 is a characteristic sign of ulnar nerve deficit. The patient is asked to take a piece of paper between the thumb and the index finger. The examiner tries to move away the piece of paper. Because of the weakness of the adductor pollicis, flexor pollicis brevis,

and first dorsal interosseous muscles, the patient is not able to hold the paper, compensating by flexing the flexor pollicis longus of the thumb to maintain grip pressure. The elbow flexion test36 is another clinical test for ulnar nerve dysfunction. Hypesthesia and tingling occur as a result of direct compression over the ulnar nerve at the elbow. In many cases, Tinel’s sign is positive as well. Electrophysiological testing is useful for diagnosis. Motor nerve conduction velocity is decreased in the elbow region (< 50 m/s). In comparison to the forearm region, motor nerve conduction velocity is reduced to about 10 m/s. Furthermore, there may be a significant amplitude reduction of the motor response potential after stimulation proximally—but not distally—at the cubital tunnel of about 20%. If there is a history of trauma, X-ray of the elbow is helpful. Ultrasound of the ulnar nerve may show pseudoneuromas, tumors and ganglion cysts, scar tissue compressing the nerve, and potential transposition of the nerve in motion. In comparison to ultrasound, MRI is more specific, but also more expensive. C8 radiculopathy, Guyon’s syndrome, thoracic outlet syndrome, and plexus brachialis lesions are potential differential diagnoses.

Timing The treatment decision is based on the degree and severity of symptoms, as in other entrapment syndromes. For patients with mild and/or intermittent symptoms, treatment is nonsurgical, including avoidance of repetitive movements (flexion and extension). Splinting has no advantage.37 If development of atrophy or weakness is detected, primary surgical treatment is indicated without delay.

Surgical Strategies There are various surgical techniques: ● Simple in situ decompression (open and endoscopic). ● Subcutaneous transposition. ● Submuscular transposition. ● Medial epicondylectomy. ● Intramuscular transposition. The last technique is not in use anymore, at least in our department.

Simple In Situ Decompression Decompression is performed under local anesthesia on an in- or outpatient basis. Tourniquet control can be used. The incision is made slightly anterior to the medial condyle with a total length of 3 to 4 cm (▶ Fig. 13.8). The posterior branches of the medial cutaneous nerve of the forearm often have variable courses, so they have to

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Fig. 13.8 Skin incision for open decompression of the ulnar nerve at the elbow.

Fig. 13.9 Extended decompression of the ulnar nerve by compression neuropathy due to an extraneural ganglion cyst.

Fig. 13.11 Subcutaneous decompression of the ulnar nerve at the elbow.

Fig. 13.10 Submuscular membranes (deep fascia) after endoscopic decompression of the ulnar nerve at the elbow.

be protected when using this approach. The ulnar nerve is identified proximally to the sulcus and dissected 5 cm distally toward the condyle. To achieve this, the Osborne ligament is divided. If the arcade of Struthers is found, it is also released. The ulnar nerve should be explored between the two heads of the flexor carpi ulnaris muscle and the submuscular membranes, and other constrictive tissue around the nerve are released. Pseudoneuromas may be present proximally to the compression. Splinting is not necessary after surgery. Endoscopic decompression of the ulnar nerve was first described by Tsai in 1995.38 For this approach, the incision is up to 2 cm in length, which is used as a port for the endoscope. Long-distance decompression is possible for a length of up to 12 cm from the retrocondylar groove and 6 to 8 cm proximally of the sulcus (▶ Fig. 13.9, ▶ Fig. 13.10).

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Anterior Transposition In comparison to the submuscular or deep transposition, the subcutaneous transposition of the ulnar nerve is less traumatic for the surrounding tissue. In both cases, the ulnar nerve is removed out of its original environment to protect the nerve from repetitive friction trauma and therefore from chronic neuropathy. If using the subcutaneous technique, the skin incision is made above the cubital tunnel. The ulnar nerve is exposed proximally to the epicondyle and dissected circumferentially to enable a transposition out of the ulnar groove, anterior and superficial to the flexor pronator muscle mass (▶ Fig. 13.11). Muscular branches to the flexor carpi ulnaris should be mobilized before transposition is made. The medial intermuscular septum and the deep fascia of

Compressive Lesions of the Upper Limb the flexor carpi ulnaris (submuscular membranes) must be divided to avoid kinking of the ulnar nerve. After creating the new tissue bed, the surgeon must secure the nerve in his new anterior position by loosely suturing a portion of subcutaneous tissue medial to the nerve. After the surgery, it is recommended to treat the elbow with care in a 90-degree flexion position for 2 weeks.

Medial Epicondylectomy In this procedure, there is no need to remove the nerve from its soft-tissue bed, which ensures the blood supply to the nerve by sparing its feeding blood vessels. First, the ulnar nerve and its branches are exposed next to the epicondyle. Second, the surrounding muscular masses are pushed aside and the diaphyseal–metaphyseal junction of the medial epicondyle is exposed. Afterward, an osteotomy is performed with a rongeur or an osteotome. The muscle mass has to be refixed to the elbow in extension. Impingement of the nerve has to be avoided, especially in motion. Postoperative splinting is not necessary. According to many comparative studies performed in the last two decades, the complication rate of simple in situ decompression is lower than anterior transposition, but the results of both techniques are equal,39,40 even for luxation of the ulnar nerve.41 Recurrences can occur in all kinds of techniques, especially after the intramuscular transposition.34

13.2.2 Ulnar Nerve Entrapment at the Wrist (Guyon’s Syndrome) Clinical Presentation The ulnar nerve is most frequently compressed at the region of the wrist. The Guyon’s canal is built by the pisiform, the hook of hamate, the volar carpal, and the transverse carpal ligament. The ulnar nerve and the ulnar artery and vein pass through the tunnel. Tendons, unlike in the carpal tunnel, are missing. Compression of the nerve in the forearm is possible but rare. If the nerve is affected at the wrist, patient’s complaints are both sensory and motor. Lesions of the nerve more distally may lead to a purely motor deficit syndrome. Sensory branches are not affected. Clinical examination may show atrophy and weakness of intrinsic muscles innervated by the ulnar nerve, monkey or claw hand, and loss of sensory function. Tinel’s and Froment’s signs may be positive. Electrophysiological testing is helpful for localizing the compression site. Distal motor latency is prolonged at the hypothenar and the first interosseous dorsalis muscle in isolated compressions of the deep (motor) branch. Sensory action potentials are reduced or missing if the ulnar nerve is compressed more proximally. A common trigger for ulnar neuropathy at the wrist is chronic repetitive trauma. Examples for extrinsic trauma are long-distance cycling or chronic pressure from tools such

as screwdriver and pliers. Further reasons for ulnar neuropathy are fractures of the hook of the hamate, metacarpals, and pisiform, and ulnar artery thrombosis. Ganglion cysts are also a common cause of compression of the ulnar nerve inside the Guyon’s tunnel.

Timing Traumatic lesions of the ulnar nerve caused by cycling, for example, have a good prognosis to recover spontaneously. Ganglions, thrombosis of the ulnar artery, and other tumors should be removed. Fractured hook of the hamate bone should be excised and the ulnar nerve released. Surgical therapy is indicated if symptoms do not improve or severe paresis and atrophy are present.

Surgical Strategy The surgery can be performed under general or local anesthesia and tourniquet control. The incision is similar to the one used for releasing the median nerve at the wrist, but just a bit longer at the distal end, toward the ulnar side, and angled at the wrist. The ulnar nerve is exposed radial to the tendon of the flexor carpi ulnaris. Afterward, the nerve is identified more distally. A possible existing palmaris brevis muscle is excised, as well as the volar carpal ligament. The next step is to identify the level of the bifurcation of the ulnar nerve. The deep branch of the ulnar nerve is tracked to the pisohamate ligament, which has to be divided for reaching a complete decompression.42 Finally, ganglions, if present, are identified and excised.

13.3 Radial Nerve Compressions of the radial nerve are rare compared with the carpal and cubital tunnel syndromes. Lesions of the radial nerve in the upper arm are in most cases result of humeral fractures or spontaneous compressions when the radial nerve pierces the lateral intermuscular septum.

13.3.1 Radial Nerve Entrapment at the Elbow (Posterior Interosseous Nerve Syndrome) Clinical Presentation The most common site of radial compression at the elbow is the arcade of Frohse.43 The arcade is a fibrous arch from the supinator muscle tendon. The posterior interosseous nerve passes beneath this structure. At this level, the radial nerve has already bifurcated into the sensory and deep motor branch. That is the reason why patients present just motor deficits, especially paralysis of the extensor digitorum superficialis and the extensor pollicis longus muscles. The extensor carpi radialis is not involved, as the branches that innervate this muscle are proximal to the compression

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Compressive Lesions of the Upper Limb site. Pain and sensory deficits are generally missing. Pain on palpation in the region of the supinator tunnel may occur, but this is meaningful only when the difference with the opposite side is very evident. Electrophysiological testing shows denervation in the muscles supplied by the deep branch of the radial nerve. Supinator and the extensor carpi radialis muscles are normal. Sensory action potentials are normal. Further causes for radial nerve compression are tumors such as lipomas and cysts. Those can be detected by ultrasound or MRI.

Timing If tumors, lipomas, or cysts are present, they should be removed. Watch-and-wait strategy may be performed for 8 to 12 weeks. If there is no spontaneous recovery, surgery is indicated. Prognosis for complete recovery is good and can be expected within 2 to 6 months after surgery.

13.3.2 Radial Sensory Nerve Entrapment (Wartenberg’s Syndrome, Cheiralgia Paresthetica) Clinical Presentation The superficial radial nerve runs on the surface of the distal radial bone. Therefore, it is exposed to external pressure (wristwatch, handcuffs) and fractures. Symptoms are hypesthesia at the dorsal radial aspect of the hand and first digit. Pain on palpation may be present at the distal portion of the forearm. Sensory action potentials are missing in electrophysiological testing. Quervain’s disease is the most common differential diagnosis.

Timing In most cases, it is sufficient to remove the source of external pressure (watch band, handcuff). In case of persistent symptoms, exploration is useful.

Surgical Strategy Surgery is performed under general or local anesthesia; tourniquet control can be used. There are two possible approaches: dorsal and anterior. In the former, the nerve is exposed to get access to the distal part of the supinator tunnel. Therefore, the skin incision is made between the tendons of the extensor carpi radialis and extensor digitorum communis muscles. The anterior approach is used more frequently. It begins proximally in the cubital fossa between the brachialis and the brachioradialis muscles (▶ Fig. 13.12). Then, the radial nerve is detected in the region of the radial head, where the nerve bifurcates into the superficial and deep branches. Crossing vessels (leash of Henry) are coagulated. The arcade of Frohse is exposed and released. The deep branch of the radial nerve is directly observed up to the end of the supinator tunnel. If present, tumors, ganglion cysts (▶ Fig. 13.13), or lipomas are excised.

Fig. 13.12 Skin incision performed by interosseous posterior syndrome.

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Surgical Strategy The skin incision is made at the palmar and radial aspect of the distal forearm with a total length of 5 to 6 cm. The superficial radial nerve is exposed between the distal portion of the brachioradialis and the extensor carpi radialis muscles. The superficial radial nerve is released from constrictive tissue such as fascia and scars.

13.4 Suprascapular Nerve Entrapment 13.4.1 Clinical Presentation The suprascapular nerve is fixed within the scapular notch. This notch is covered by the superior transverse scapular ligament. If the arm is abducted and the

Fig. 13.13 Interosseous posterior syndrome with compression of the deep branch of the radial nerve due to a parosteal lipoma.

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Fig. 13.14 Prone position for decompression of the suprascapular nerve. Skin incision (dashed line). Fig. 13.15 Compressed suprascapular nerve (N) due to a ganglion cyst (C) in the suprascapular notch.

shoulder is moved forward, the nerve is pushed against the ligament. Repetitive motions may damage the nerve. Various sports such as basketball, volleyball, tennis, and handball are typical motion sequences for repetitive compression of the nerve. Ganglions are rare causes for compression and can be seen on MRI. Antoniadis et al presented a series of 28 patients, of whom 16 were athletes. Only in three cases, a ganglion cyst was the origin for nerve compression.44 Electrophysiological testing is helpful. Denervation in the supra- and infraspinatus muscles is present. Patients report about deep-seated pain in the shoulder as well as weakness in abduction and rotation of the shoulder. The examination shows prominent atrophy of the supra- and infraspinatus muscles.

13.4.2 Timing Athletes should pause their training to avoid repetitive motions. If atrophy and weakness of the infra- and supraspinatus muscles is present, exploration is necessary.

13.4.3 Surgical Strategy Surgery is performed under general anesthesia in prone position. Skin incision is made 2 cm above and parallel to the scapular spine (▶ Fig. 13.14). The trapezius is split and the supraspinatus muscle is retracted. Then the scapular notch and the superior transverse scapular ligament are exposed. The suprascapular vein and artery are located above the ligament. The suprascapular nerve passes under the superior transverse scapular ligament. Complete section of this ligament is sufficient to release the nerve (▶ Fig. 13.15). The surgery is performed using the microscope.

References [1] Assmus H, Antoniadis G, Bischoff C, et al. Diagnostik und Therapie des Karpaltunnelsyndroms. Germany: Interdisziplinäre Leitlinien der AWMF; 2012. Avaialble at: http://www.awmf.org/leitlinien/detail/ll/ 005–003.html [2] de Krom MC, Knipschild PG, Kester AD, Thijs CT, Boekkooi PF, Spaans F. Carpal tunnel syndrome: prevalence in the general population. J Clin Epidemiol. 1992; 45(4):373–376 [3] Phalen GS. The carpal-tunnel syndrome. Seventeen years’ experience in diagnosis and treatment of six hundred fifty-four hands. J Bone Joint Surg Am. 1966; 48(2):211–228 [4] Phalen GS. The carpal-tunnel syndrome. Clinical evaluation of 598 hands. Clin Orthop Relat Res. 1972; 83(83):29–40 [5] Padua L, Lo Monaco M, Padua R, Gregori B, Tonali P. Neurophysiological classification of carpal tunnel syndrome: assessment of 600 symptomatic hands. Ital J Neurol Sci. 1997; 18(3):145–150 [6] El Miedany Y, Ashour S, Youssef S, Mehanna A, Meky FA. Clinical diagnosis of carpal tunnel syndrome: old tests-new concepts. Joint Bone Spine. 2008; 75(4):451–457 [7] de Krom MC, Knipschild PG, Kester AD, Spaans F. Efficacy of provocative tests for diagnosis of carpal tunnel syndrome. Lancet. 1990; 335 (8686):393–395 [8] Melvin JL, Schuchmann JA, Lanese RR. Diagnostic specificity of motor and sensory nerve conduction variables in the carpal tunnel syndrome. Arch Phys Med Rehabil. 1973; 54(2):69–74 [9] Allieu Y, Mackinnon SE, eds. Nerve Compression Syndromes of the Upper Limb. London: Martin Dunitz; 2002 [10] Kamolz LP, Schrögendorfer KF, Rab M, Girsch W, Gruber H, Frey M. The precision of ultrasound imaging and its relevance for carpal tunnel syndrome. Surg Radiol Anat. 2001; 23(2):117–121 [11] Practice parameter for carpal tunnelsyndrome (summary statement). Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 1993; 43(11):2406–2409 [12] Chow JC, Hantes ME. Endoscopic carpal tunnel release: thirteen years’ experience with the Chow technique. J Hand Surg Am. 2002; 27(6): 1011–1018 [13] Kern BC, Brock M, Rudolph KH, Logemann H. The recurrent carpal tunnel syndrome. Zentralbl Neurochir. 1993; 54(2):80–83 [14] Mackinnon SE, McCabe S, Murray JF, et al. Internal neurolysis fails to improve the results of primary carpal tunnel decompression. J Hand Surg Am. 1991; 16(2):211–218

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Compressive Lesions of the Upper Limb [15] Agee JM, McCarroll HR, North ER. Endoscopic carpal tunnel release using the single proximal incision technique. Hand Clin. 1994; 10(4): 647–659 [16] Chow JCY. Endoscopic release of the carpal ligament: a new technique for carpal tunnel syndrome. Arthroscopy. 1989; 5(1):19–24 [17] Scholten RJ, Gerritsen AA, Uitdehaag BM, van Geldere D, de Vet HC, Bouter LM. Surgical treatment options for carpal tunnel syndrome. Cochrane Database Syst Rev. 2004; 4(4):CD003905 [18] Chow JCY. The Chow technique of endoscopic release of the carpal ligament for carpal tunnel syndrome: four years of clinical results. Arthroscopy. 1993; 9(3):301–314 [19] Chow JCY. Endoscopic carpal tunnel release. Two-portal technique. Hand Clin. 1994; 10(4):637–646 [20] Thoma A, Veltri K, Haines T, Duku E. A systemic review of reviews comparing the effectiveness of endoscopic and open carpal tunnel decompression. Plast Reconstr Surg. 2004; 113:1184–1191 [21] Rosenbaum RB, Ochoa JL, eds. Carpal Tunnel Syndrome and Other Disorders of the Median Nerve. Amsterdam: Butterworth Heinemann; 2002 [22] Spinner M. The anterior interosseous-nerve syndrome, with special attention to its variations. J Bone Joint Surg Am. 1970; 52(1):84–94 [23] Nigst H, Dick W. Syndromes of compression of the median nerve in the proximal forearm (pronator teres syndrome; anterior interosseous nerve syndrome). Arch Orthop Trauma Surg. 1979; 93(4):307–312 [24] Hill NA, Howard FM, Huffer BR. The incomplete anterior interosseous nerve syndrome. J Hand Surg Am. 1985; 10(1):4–16 [25] Seror P. Anterior interosseous nerve lesions. Clinical and electrophysiological features. J Bone Joint Surg Br. 1996; 78(2):238–241 [26] Nakano KK, Lundergran C, Okihiro MM. Anterior interosseous nerve syndromes. Diagnostic methods and alternative treatments. Arch Neurol. 1977; 34(8):477–480 [27] Sood MK, Burke FD. Anterior interosseous nerve palsy. A review of 16 cases. J Hand Surg [Br]. 1997; 22(1):64–68 [28] Spinner M, ed. Injuries to the Major Branches of Peripheral Nerves of the Forearm. Philadelphia, PA: WB Saunders; 1978 [29] Struthers J. On a particularity of the humerus and humeral artery. Month J Med Sci. 1948; 28:264–267 [30] Struthers J. On some points in the abnormal anatomy of the arm. Br For Med Chir Rev. 1854; 14:170–179

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[31] Dellon AL. “Think nerve” in upper extremity reconstruction. Clin Plast Surg. 1989; 16(3):617–627 [32] Osborne GV. The surgical treatment of tardy ulnar neuropathy. J Bone Joint Surg Br. 1957; 39:782 [33] Dellon AL. Musculotendinous variations about the medial humeral epicondyle. J Hand Surg [Br]. 1986; 11(2):175–181 [34] Assmus H, Antoniadis G, Bischoff C, et al. Cubital tunnel syndrome - a review and management guidelines. Cent Eur Neurosurg. 2011; 72 (2):90–98 [35] Froment MJ. La paralysie de làdductur du pouce et le signe de la prahnsion. Rev Neurol (Paris). 1915; 28:1236–1240 [36] Fine EJ. The ulnar flexion maneuver. Muscle Nerve. 1985; 8:612 [37] Caliandro P, La Torre G, Padua R, Giannini F, Padua L. Treatment for ulnar neuropathy at the elbow. Cochrane Database Syst Rev. 2011(2): CD006839 [38] Tsai TM, Bonczar M, Tsuruta T, Syed SA. A new operative technique: cubital tunnel decompression with endoscopic assistance. Hand Clin. 1995; 11(1):71–80 [39] Barthels RH, Verhagen WI, van der Wilt GJ, Meulstee J, van Rossum LG, Grotenhuis JA. Prospective randomized controlled study comparing simple decompression versus anterior subcutaneous transposition for idiopathic neuropathy of the ulnar nerve at the elbow: Part 1. Neurosurgery. 2005; 56(3):522–530 [40] Gervasio O, Gambardella G, Zaccone C, Branca D. Simple decompression versus anterior submuscular transposition of the ulnar nerve in severe cubital tunnel syndrome: a prospective randomized study. Neurosurgery. 2005; 56(1):108–117, discussion 117 [41] Kraus A, Sinis N, Werdin F, Schaller HE. Is intraoperative luxation of the ulnar nerve a criterion for transposition? Chirurg. 2010; 81(2): 143–147 [42] Ombaba J, Kuo M, Rayan G. Anatomy of the ulnar tunnel and the influence of wrist motion on its morphology. J Hand Surg Am. 2010; 35(5):760–768 [43] Frohse F, ed. Die Muskeln des Menschlichen Armes. Bardelebens Handbuch der Anatomie des Menschlichen. Jena: Fischer; 1908 [44] Antoniadis G, Richter HP, Rath S, Braun V, Moese G. Suprascapular nerve entrapment: experience with 28 cases. J Neurosurg. 1996; 85 (6):1020–1025

Compressive Lesions of the Lower Limb and Trunk

14 Compressive Lesions of the Lower Limb and Trunk Christian Heinen and Thomas Kretschmer Abstract Compressive nerve lesions in the lower extremities are less frequent than in the upper limb. Clinical features include pain, sensory impairment, and weakness. Due to symptomatic similarity, symptoms are prone to be misinterpreted and falsely attributed to the much more common lumbar spine syndromes. Therefore, meticulous assessment and review of history, physical examination, and imaging and electrophysiology studies are mandatory to exclude spinal genesis and confirm peripheral nerve compression. Common primary compression syndromes occur in the anatomically predefined narrow spaces of the lower extremity and trunk, such as at the infrapiriform foramen, at the anterior superior iliac spine, in the vicinity of the inguinal ligament and superficial inguinal ring, around the exit of Alcock’s and Hunter’s canal, around the fibular head, and the anterior and posterior tarsal tunnel. They are discerned from secondary forms, which may be caused by scarring, cysts, varices, muscle hypertrophy, and acquired bony changes following trauma or medical treatment. In order to confirm diagnosis and choose the most appropriate surgical strategy, we seek for anatomical resolution of the presumed narrowing by the use of highresolution magnetic resonance imaging (MRI) and neurosonography imaging. In view of significant functional loss and differing recovery potential of involved nerves, adequate timing of decompression is important. Keywords: entrapment, decompression, surgical technique, endoscopy, lower extremity, trunk, timing

14.1 Nerves 14.1.1 Sciatic Nerve General Considerations Being the largest nerve in the body, the sciatic nerve usually consists of L4–S3 contributions. After its intrapelvic course in the vicinity of the sacrum, the bladder, the rectum, and the iliac vessels, it leaves the pelvis in the incisura ischiadica major between the piriformis muscle and the gemellus superior muscle passing the infrapiriform foramen. Different courses above/within/beneath piriformis muscle have been described.1 Despite appearing as one nerve, the sciatic is already divided in its peroneal and tibial aspect with respective root supply at an infrapiriform level.

The peroneal portion of the nerve is located laterally, whereas the tibial portion remains medially. In varying manifestations, a dividing groove between these two portions can already be seen at an infrapiriform level. Its close relationship to the hip joint predisposes the sciatic nerve to traumatic or iatrogenic lesions, the peroneal portion being more frequently affected. One major drawback of a proximal sciatic nerve lesion is its very limited amenability to imaging and electrophysiological preoperative work-up due to its deep localization. In patients with previous surgery, metal artefacts, e.g., may impair magnetic resonance imaging (MRI) neurography. High-resolution neurosonography lacks depth of tissue penetration, impeding detailed nerve depiction. Therefore, frequently the exact level of compression or lesion remains unclear, necessitating an explorative approach with intraoperative inspection and evaluation. This can be accomplished with minimal surgical morbidity by the endoscopic approach we described.2 In essence, a small entry port of 3 cm is used via the subgluteal fold to follow the nerve proximally by a retractor-held endoscope along its gluteal course. Simple decompression from scar, adhesions, and venous tethering can easily be accomplished by this route. The same port allows for exploration in the opposite caudal direction along the proximal thigh.

Deep Subgluteal Syndrome/Piriformis Syndrome There still is controversy concerning the proper diagnosis, assessment, and treatment in piriformis syndrome.3 Some authors introduced the more adequate term of deep subgluteal syndrome (DSS) encompassing different causes for sciatic nerve entrapment.4 Aside from the “classic” piriformis syndrome caused by a hypertrophic muscle or sharp tendinous muscle border, a large variety of pathologies have been reported— compressive fibrous bands, anatomic variants or acquired changes of surrounding muscles such as obturator internus, quadratus internus, and gemellus muscles or the hamstrings, and more. Inborn or acquired bony alterations of the hip joint/ischial tuberosity or vascular abnormalities such as circumferential or penetrating varices may be the underlying cause. Clinical symptoms consist of deep gluteal pain and sensory-motor deficits involving tibial, peroneal, and dorsal cutaneous femoral nerve. External rotation, hip flexion, and simultaneous knee extension may provoke the symptoms. Deep gluteal palpation and pressure overlying the sciatic exit and course at its infrapiriform level in relaxed prone and in a lateral

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Compressive Lesions of the Lower Limb and Trunk decubitus position with the hip flexed, the knee bent, and the leg rotated inward (“quadripartite position”; stretches sciatic and at the same time lifts the nerve to a more superficial level) may provoke the typical pain. Frequently, patients have problems to sit on the affected half of the buttock and prefer to use an asymmetric sitting position that releases pressure on this side. In terms of imaging, MRI is the gold standard assessing or excluding space-occupying lesions. High-resolution neurosonography with detailed depiction of the intraneural anatomy is limited due to restricted tissue penetration. Some reports on electrophysiology with pathologic H-reflexes in different positions may underline DSS. Electromyogram (EMG) alone might be misleading if only the peroneal part of a lesioned sciatic nerve is affected. Conservative treatment consists of physiotherapy, anti-inflammatory medication, and local injections of corticoids or botulinum under ultrasound control into the corresponding muscles. According to the literature, both conservative and surgical treatment seem to be helpful,5,6 and classically only in conservative therapy refractory cases’ surgery is considered. We think this very general approach should be more nuanced. Fibrovascular compression or the abovementioned secondary causes can only be relieved surgically (see the next section on Surgical Strategy).

Key to successful treatment will remain exclusion or identification of mechanical encroachment, which at times may be hard to achieve. In cases of high degree of suffering or significant functional loss, (early) surgical exploration is justified.

Surgical Strategy Different approaches have been described, such as infragluteal, transgluteal, and subgluteal (see ▶ Fig. 14.1a–e).2,7,8 Position is usually prone; anatomical landmarks and the course of the nerve are highlighted (midline, subgluteal skin fold, coccyx, posterior superior iliac spine) with a skin marker. Using a small horizontal incision within the subgluteal skin fold, the nerve can be easily and bluntly detected in the proximal thigh entering the space between the long head of biceps femoris and the semitendinosus muscle. This access facilitates dissection of the nerve in both distal and proximal direction. If necessary, an additional gluteal incision can be made, allowing for transgluteal exposure and decompression of the nerve. Endoscopy via a subgluteal port enables dissection of the nerve along its gliding tissue and easy identification of the dorsal cutaneous branch. Even in big-framed patients, visualization of compressive tissue and thus

Fig. 14.1 (a) Indication in centimeters to demonstrate the possible range of triportal decompression starting at the subgluteal level; white dots indicate infrapiriform foramen level. (b) Triportal decompression of the sciatic/peroneal nerve (arrows indicating surgical accesses). (c) Identifying the sciatic nerve (asterisk) via the subgluteal incision. (d) Endoscopic view; elevated connective tissue (arrows) compressing the sciatic nerve (asterisk). (e) Endoscopic view; decompressed sciatic nerve at the infrapiriform foramen level (asterisk).

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Compressive Lesions of the Lower Limb and Trunk targeted surgery up to the infrapiriform foramen level are possible. If the piriform muscle is the origin of symptoms, it can be partially or completely dissected and incised without subsequent gait impairment.6 This seems to account for gemelli muscles as well. In case of a sudden stop and resistance of endoscopic advancement that cannot be resolved and neurolyzed via this route, it is simple and fast to add a transgluteal focused route in a second step during the same surgery. For this, we use an oblique incision at the buttock overlying the anticipated course of the sciatic nerve. In case of substantial trauma, these two ports could potentially still be connected to a flap resembling the more classic large question mark–shaped skin incision (classic approach according to Henry). This will provide a more extensile overview to the whole region at the price of massive gluteal muscle disinsertion. Accessrelated morbidity and muscle trauma, therefore, is a major drawback of this large approach, and even in sciatic nerve reconstruction or tumor surgery at gluteal level, we do not see the need for this approach anymore. We prevent cutting the gluteal muscles by atraumatic blunt dissection in a more perpendicular trajectory directly overlying the nerve, which already has been identified via the subgluteal port. Muscle dissection is in line with the fiber orientation of the gluteus maximus after sharp incision of the gluteal fascia. Care must be taken to avoid the plane of the gluteal nerve branches and vessels. Intermediate use of a nerve stimulator to detect branches is most helpful. When treating big or very athletic patients, a fixed frame-retractor system with long blunt blades is useful. Proximal intrapelvic compression syndromes within the pelvis are rare. Cases of intrapelvic sciatic nerve compression syndromes have been reported, such as sciatic endometriosis (“catamenial syndrome”), ganglion cysts, varices, or postoperative scarring. Treatment includes hormonal or anti-inflammatory medication. In case of surgery, transabdominal or minimal-invasive methods can be used.9

14.1.2 Peroneal Nerve General Considerations Anatomy After emanating from the sciatic, the peroneal nerve descends adjacent to the medial border of the biceps femoris muscle. It then turns laterally toward the fibular head lying superficially. Its proximity to the bones and knee as well as to the tibiofibular joint favors its vulnerability. The nerve enters the space between the two heads of the long peroneus muscle at the fibular head.

This is the actual anatomic predefined notch. At this level, the nerve divides into three branches (from medial to lateral): the tibiofibular joint branch, the deep branch, and the superficial branch. The deep branch innervates anterior tibial muscle and the toe extensors including the hallux. It supplies the interdigital space between the hallux and the second toe autonomously. The superficial branch supplies the foot everting long and short peroneus muscles and the lateral lower leg as well as the instep.

Clinical Aspects The compression neuropathy of the peroneal nerve at the fibular head is the most common neuropathy in the lower extremity.10 Sudden nonpainful functional loss is the leading clinical symptom. However, there seem to be no reliable data on incidence.11 Unfamiliar physical activity, sustained work in a kneeling position (“harvester’s palsy”), sitting with legs crossed, uncommon postures, and long periods of immobilization with casts stress the peroneal nerve at its notch. By fortifying an already (latently) existing compressive site, an edematous nerve reaction will be induced that leads to further rise in pressure and more edema in a vicious circle. Furthermore, systemic illness such as diabetes and polyneuropathy predisposes peroneal neuropathy. If a patient presents with pain in an otherwise atraumatic lesion, tumor or an intraneural ganglion cyst needs to be ruled out. Intraneural ganglia play an important role in the compression syndromes of the peroneal nerve. There are different theories on the origin of extra-/ intraneural or combined ganglia (degenerative/synovial/ tumorous). In recent years, the “unifying articular (synovial) origin of intraneural ganglia” was established.12 In brief, it postulates that connection of tibiofibular joint synovia to articular nerve branches enables entry of synovial fluid into the nerve’s internal structure and thus paves the way for fluid extension within the intraneural space. The progressive filling with synovial fluid and gel leads to formation and rise of intraneural pressure, and as such to an “internal compression syndrome.” Clinical symptoms may vary from complete/incomplete, whole/partial nerve, etc., and include foot/toe drop, weakness of foot eversion, sensory impairments, and pain. Thorough physical examination usually gives clear hints to determine the lesion level (pattern of neurological deficit, Hoffmann–Tinel sign, pain, palpable mass). Note that the posterior tibial muscle (foot inversion) is a tibial nerve–innervated muscle. This is of clinical importance discerning pure peroneal from combined peroneal-tibial, sciatic, or L5 lesion. Imaging usually encompasses MR neurography and high-resolution neurosonography depicting caliber changes

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Compressive Lesions of the Lower Limb and Trunk of the nerve at the compression site or space-occupying lesions such as intra/extraneural ganglia, varices, popliteal aneurysms, and sesamoid bones (“fabella”). Nerve ultrasound gives excellent resolution of lower extremity nerves up to a level of 1 mm, and is easy to apply. It enables quick differentiation of cyst from classic compression or tumor. Electrophysiology further enhances nerve lesion assessment and gives clues as to the nerve’s functional state by using EMG and conduction studies (complete vs. incomplete lesion, absence of voluntary muscle potentials). Polyneuropathies and diabetes seem to promote compression; nonetheless, these patients benefit from surgery.13

Surgical Strategy Surgical strategy is dictated by the underlying pathology. Timing of surgery depends on the severity of symptoms, as the recovery potential of the peroneal nerve is limited. With severe symptoms and definitely with complete foot drop, we favor prompt surgery. At the junction of incomplete traumatic nerve lesions and compressive elements (anatomic notch, constricted scar), external compression can prevent regeneration of otherwise intact internal nerve structure (Sunderland lesions I to III, Millesi A and B). Decompression can enable or at least facilitate proper recovery in these cases. This is why we are quite generous when it comes to indicating simple decompression at the fibular head notch. The benefit can be enormous, the risk is minimal, and the surgery is simple.

The patient is positioned prone, allowing for decompression of the nerve in both cranial and caudal direction if necessary. Some authors prefer lateral or supine position with flexed and slightly internally rotated leg. A semilunar incision is placed on the fibular head anterior to the nerve, avoiding a direct scar on the nerve. Already at a fascial level, the nerve can be detected digitally in its course medial and posterior to the fibular head. The fascia is then incised and opened up. Usually, the nerve is surrounded by a gliding fatty tissue that should be maintained and not manipulated or coagulated as it protects and provides the nerve with vessels enabling passive motion during leg movement. Following the nerve distally, the superficial fascia of the long peroneal muscle inserting at the fibular head is verified, incised, and kept apart. One should ensure not to open the superficial layer only but also the deeper lamina. Then, the trifurcation of the nerve can be worked out once again respecting the surrounding gliding tissue. Electrostimulation is used to identify and test nerve response of the single branches. For verification of proper decompression, dissectors can be useful. After wound closure, we prefer compression dressing instead of wound drains. Mobilization of the patient can start immediately avoiding novel adherences due to scarring. Intraneural ganglia require a different approach and setting (see ▶ Fig. 14.2a–f).

Fig. 14.2 (a) Intraoperative view; irregular shape of the distended nerve. (b) Evacuation of the intraneural cyst after epineurotomy. (c) Identification of the feeding articular branch. (d) Ligation of the feeding articular branch. (e) Note the enlarged lumen (arrow) of the dissected feeding articular branch. (f) Decompressed peroneal nerve.

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Compressive Lesions of the Lower Limb and Trunk Frequently, onset of sensorimotor impairments is quick and substantial. Timing is crucial and early surgery should be scheduled, as only few patients experience a spontaneous and sufficient recovery. We prefer prone position and a microsurgical setup including microscope, electrostimulation, intraoperative electrophysiology, and neurosonography. Skin incision is determined by the lesion’s extension. Exposition should comprise the whole lesion including a healthy nerve segment proximal and distal to the lesion. By doing that, the healthy nerve sections can be inspected and more importantly tracked into/within the cystic part. The goal of surgery is to decompress the nerve by epineurotomy and cyst fenestration. At the same time, a recurrence is prevented by disconnecting the “feeding” articular branch (“close the faucet”). This is accomplished by radical ligation and transection of the feeding branch as close to the tibiofibular joint as possible. We prefer to excise a larger segment for histopathology in order to enlarge the distance between joint and nerve. Disconnection is regarded as the most effective measure to prevent cyst recurrence; as multiple articular branches can occur, these also should be ruled out to minimize this risk. As the cystic wall cannot be dissected from the epineurium, an attempt to make a “radical resection” of the cyst will definitively lead to fascicular damage and thus is contraindicated. The “cyst treatment” is limited to a microsurgical fenestration of the cyst wall at a fascicle free site where it reaches the epineural surface. In some patients, there is one big communicating intraneural, i.e., intraepineurial, cyst, compressing, dislocating, and thinning out the fascicles. These cases can be treated easily with one larger fenestration. However, multiple and multilobular cysts can occur. They complicate surgery in so far as more fenestrations are needed and frequently not all cysts can be opened. The recurrence rate is higher in such cases. Intraoperative ultrasound can help to detect deep lying cyst chambers. We try to avoid electrocauterization within the nerve and prefer mild focused compression using cottonoids to stop bleeding. In patients with underlying bony deformations in the form of exostosis, fragments, or additional bones (fabella), the surgical task consists of tissue-sparing bone removal, decompression, and creation of a new and smooth nerve bed using autologous fat pads to enable supple passive motion of the nerve during leg movements. Rarely intraneural varices are the underlying pathology of peroneal nerve deficit. They demand careful microsurgical interfascicular dissection and disconnection of the vessel after epineurotomy.

Results For simple entrapment neuropathy, there are only a few systematic outcome studies. In addition, they refer to small patient numbers. They report favorable surgical outcome and low complication rates.14,15 This accounts particularly for patients with mild symptoms.16 Pain and motor weakness seem to benefit better than sensory function.17 Results of surgery for intraneural ganglia differ from simple decompression. It has been reported that surgery improves pain in the majority of patients. Improvement of sensorimotor function is dependent on the severity and duration of symptoms prior to surgery, and the extent of lesion. It occurs in 50 to 64% of cases.18 A significant problem is recurrent cyst formation, which is reported in up to 24% of the patients.19 Disconnection of the feeding articular branch is the accepted measure to prevent recurrent ganglia.20 The peroneal nerve has low regenerative capacity in general.21 Therefore, in patients with only fair or insufficient recovery, secondary procedures such as transfer of the tendon of posterior tibial muscle have a definite role to improve gait and should be considered in failed nerve regeneration. There is a need to counsel patients in that regard and offer this type of treatment.

Anterior Tarsal Tunnel This rare entrapment syndrome affects the terminal branch of deep peroneal nerve at the cruciform ligament or underneath the extensor hallucis brevis tendon. Both the medial (providing the first interdigital space) and the lateral (providing the dorsum) branch can be affected, provoking different symptoms. Diabetic patients seem to be susceptible. Association with lumbosacral radiculopathy and foot deformities has been described.22 Local and activity-related pain and paraesthesia are the main symptoms. Conservative treatment consists of anti-inflammatory medication, infiltration with local anesthetics or corticoids, and shoe orthoses. When symptoms persist, the nerve can be surgically decompressed. The longitudinal or transverse skin incision follows the dorsal pedis artery as the most important anatomic landmark. After that, the cruciform ligament and the extensor tendon are dissected. Then, the nerve is identified and decompressed by transecting the cruciform ligament. Rarely, part of the tendon needs to be notched. Surgery can greatly be eased if performed in a bloodless field. Pain relief can be achieved in up to 80%.23

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Entrapment of the Superficial Peroneal Nerve Isolated entrapment of the superficial peroneal nerve distal to the fibular head is postulated to occur, at the site where the nerve perforates the deep fascia of the leg.24 MRI and/or neurosonography help to detect compressive pathologies. Electrophysiology may display lowered conduction velocities or pathologic EMG of the peroneal muscles. Skin incision is placed about 5 cm lateral to the lateral tibial border. Then, the fascia is opened and the nerve decompressed. Reports describe pain relief after surgery, with body mass index being a negative predictor for successful surgical treatment.25

Sural Nerve Primary sural nerve entrapment is extremely rare. Compression can occur throughout the whole course of the nerve, with pain and sensory impairments being the clinical features. Due to its rather long course, the nerve can be damaged secondarily after fractures and their treatment. Conduction studies reveal pathologic sural nerve values. Imaging using MRI and neurosonography may reveal bony or vascular anomalies or secondary scarring. In case of failed conservative treatment, the nerve can easily be accessed between the lateral ankle and the Achilles tendon, and decompressed.26 Patients undergoing diagnostic sural nerve biopsy harbor the risk of painful neuroma formation. As mostly only a few centimeters are harvested for histopathological exam, the proximal neuroma often is located superficially and distal to the fascia. Symptoms such as pain and dysesthesia occur in up to 19% of the patients on contact but also when moving.27 Conservative treatment consists of medication, serial infiltrations under ultrasound guidance using local anesthetics and/or corticoids.28 If conservative treatment fails, neuroma resection can be performed. However, a new neuroma will form anyway. Superficial neuromas are much more prone to ectopic nerve activity and painful transformation. Surgery therefore aims at high-level nerve resection to bury the stump deep within the muscular compartment. This implies to extend the resection above mid lower leg.

14.1.3 Tibial Nerve Anatomy In contrast to the anatomic course of the peroneal nerve, the tibial nerve proceeds in a straight line along with tibial artery to the lower leg before it changes direction toward the dorsal aspect of the inner ankle to branch into a medial and a lateral plantar nerve that supply the sole of the foot and its intrinsic muscles.

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Usually, L5–S2 account for tibial nerve function providing all foot and toe flexors including posterior tibial muscle (foot inversion) and sensation to the sole of the foot and heel (calcaneal branch). The tibial nerve passes the soleal sling at the knee level (two to three fingers’ breadth below the flexor crease) to enter the tarsal tunnel distally behind the medial malleolus. The calcaneal branch usually forks off the main branch before or within the tarsal tunnel. The tibial nerve then divides into the sensorimotor medial and lateral plantar nerve before or after entering the flexor retinaculum. There are different anatomically given bottlenecks, with the most important one being within the tarsal tunnel at the ankle.

Proximal Soleal Sling A fascia connecting the tibial and fibular head of the soleus muscle can compress the tibial nerve. Aside from idiopathic causes, posttraumatic and diabetic forms have been described. Clinical presentation is calf pain and mostly sensory problems in addition to a Hoffmann–Tinel sign. Weakness can afflict flexor hallucis longus muscle. MRI may help to confirm soleal sling syndrome by identification of nerve swelling and hyperintensity at this location.29 As this entrapment syndrome is very rare, symptomatic patients may have undergone tarsal tunnel surgery prior to its diagnosis. Surgery consists of a skin incision at the medial calf and dissection of the gastrocnemius fascia. After identification of the space between the gastrocnemius and the most proximal aspect of the soleus muscle, the sling can be divided.30

Posterior Tarsal Tunnel Syndrome A proximal tarsal tunnel syndrome (TTS) can be differentiated from the distal one. In nearly 80% of the cases, an underlying pathology such as perineural ganglia, lipoma, and nerve sheath tumors account for TTS. Clinically, the proximal TTS also affects the calcaneal branch and therefore includes sensory deficits at the heel. This is in contrast to the distal TTS. Toe flexion and/or toe spreading may be impaired. The surface of the sole can be flattened. A Hoffmann–Tinel sign can be elicited along the nerve’s course within the tarsal tunnel.31 Imaging should include MR neurography and highresolution neurosonography. Electrophysiologically, lowered conduction velocities of the lateral and medial plantar nerves in combination with altered EMG of toe flexor may empower the diagnosis. In primary TTS, conservative management with antiinflammatory medication, physiotherapy, and splinting is of first choice. Patients with persisting or worsening symptoms may undergo decompressive surgery.

Compressive Lesions of the Lower Limb and Trunk The same accounts for secondary space-occupying lesions provoking TTS. A semilunar skin incision is placed along the course of the nerve dorsal the medial malleolus. Dissection of the complete retinaculum flexorum should be performed assuring the decompression not only of the main trunk but also of the medial and lateral plantar nerve. This long incision, however, bears a relatively high risk of impaired wound healing (skin tension, vascular insufficiency, tissue edema, venous insufficiency). Therefore, we prefer one or two short horizontal skin incisions—the first at the proximal and the second at the distal end of the tunnel. The skin bridge can be lifted with a Langenbeck retractor, or alternatively a retractorheld endoscope can be used from a proximal to distal direction. Sparing of the calcaneal branch is of utmost importance. Surgery can be performed openly or with endoscopic assistance.32 Especially in patients with diabetes or venous insufficiency, preservation of veins and arteries is mandatory to prevent impaired wound healing. We usually advise the patients to intermittently elevate the leg and ambulate on elbow crutches for the first 1 to 2 weeks of mobilization, avoiding full weight bearing on the affected foot. Results may vary significantly: patients with secondary causes seem to benefit more frequently from the procedure contrasting with those with idiopathic origin.33,34

Distal Tibial Nerve Compression Syndromes For the sake of completeness, rare distal entrapments of the medial plantar nerve (“jogger’s foot”) as well as of the lateral plantar nerve (“Baxter’s neuropathy”) are mentioned in the literature.35

tion and simultaneously applying pointed pressure on the sole between the affected metatarsal bones. MRI imaging confirms the diagnosis. High-resolution ultrasound is also capable of detecting the mass.37 In addition to medication, physiotherapy, and splinting, diagnostic therapeutic blocks are indicated. Infiltration can easily be performed with or without ultrasound guidance from a less painful dorsal interdigital approach. Serial infiltration with local anesthetic and corticoids aims at reducing pain and inflammation. However, we think its potential to lead to long-lasting relief in severe Morton’s neuralgia is limited. Surgical excision of the neuroma, in contrast, has a strikingly high success rate. For surgery, a dorsal and a plantar approach have been described.38 We have clear preference for the dorsal interdigital “web-space” approach as it circumvents a very painful plantar incision that limits early weight bearing and has high potential for wound infection. Most authors use the dorsal approach and either resect the pseudoneuroma or decompress it.35 The pseudoneuroma is located directly between the eminences of the metatarsal heads underneath the transverse metatarsal ligamentum (TML). A 3-cm longitudinal incision is placed from in-between the bases of the affected toes to proximal. Once the metatarsalgia have been identified, they are pushed apart by a small retractor placed on the bone to open the space. The visible TML builds the rooftop of the pseudoneuroma. It is either incised to approach the pseudoneuroma directly from above or left intact to reach from a more anterior trajectory. The conglomerate of pseudoneuroma, bursa, and thickened sensory digital nerve endings in the pseudoneuroma are dissected out and excised. Surgery is greatly eased in a bloodless field and can be accomplished under local anesthesia. Results are very satisfying even in the long term.36,38,39,40

Morton’s Neuroma

14.1.4 Lateral Femoral Cutaneous Nerve (Meralgia Paraesthetica)

Even more distal and certainly more frequent is the entrapment of the terminal branches of the medial and lateral plantar nerve. It affects mainly the nerves between the second and third or third and fourth metatarsal bones. Chronic irritation of the nerve and adjacent bursa intermetatarsophalangea may provoke a painful pseudoneuroma and chronic bursitis. Women are affected four times more often, and multiple Morton’s neuromas are frequent. Association with foot deformities have been reported.36 Arthritis and other degenerative osseous conditions should be excluded. Patients often prefer to walk barefoot as narrow shoes may provoke the symptoms. Clinically, aside from pain and sensory deficits, the characteristic Mulder’s sign is the main feature. It is performed by compressing the arch of the foot in a mediolateral direc-

The incidence of meralgia paraesthetica (MP) is estimated at 4 to 10 per 10,000. Mean age of occurrence is 30 to 40 years, and correlation with pregnancy and carpal tunnel syndrome has been reported.41 A total of 7 to 10% of the patients display bilateral manifestation.42 There seems to be an association with positioning in surgery in prone position, weight change, tight clothing, etc.43 Being a pure sensory nerve, patients with MP suffer from paresthesias or dysesthesias in the anterolateral thigh depending on posture. Frequently, there is a burning and tingling component on the pain. Classic teaching states retroflexion (“inverse Lasègue”) as pain inflicting posture. In our observation, we find both retroflexion and hip flexion or sitting to provoke pain. In clear cases, there is a punctum maximum (PM) of the pain in the vicinity of the anterior iliac spine, where finger tapping can elicit the typical

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Compressive Lesions of the Lower Limb and Trunk painful sensations spreading to the anterolateral thigh. The PM should be in accordance with the lateral femoral cutaneous nerve (LFCN) course and is the supposed point of compression. Electrophysiology may show lowered conduction velocity of LFCN; imaging with high-resolution neurosonography can reveal the nerve and its compressive site. In addition, MRI may help to exclude compressive pathologies in the nerve’s vicinity. Anatomically, the nerve arises from L1–L2 and then takes its course beneath the iliac fascia in the retroperitoneum toward the superior anterior iliac spine (SAIS).44 At this point, the nerve bends nearly 90 degrees, entering the thigh usually below the inguinal ligament and lateral to the sartorius muscle border covered by the thigh fascia (85% of the cases).45 There are several variants of the nerves’ course, from intrapelvic to infrainguinal. The LFCN can run underneath, through, or above the ligament. It can also perforate the sartorius muscle. At times, it will run above the iliac spine, and can have a bony roof or its own bony iliac canal.46 Differential diagnoses such as general neuropathy, spinal problems, pathologies of the lumbar plexus, or intrapelvic causes have to be excluded. In roughly 25% of patients, symptoms will resolve spontaneously especially if associated with pregnancy. Aside from weight reduction, change of clothing habits and infiltrations using local anesthetics or corticoids can be applied with a high success rate.47 In patients with pain refractory to conservative treatment or intractable pain, surgery is indicated. There are two surgical techniques available: one is a simple decompression at the inguinal ligament level, the other one is an intra-abdominal transection of the nerve. None has proven significant superiority.48,49 We prefer decompression as a first surgical step, leaving transection for cases of failed decompression and massive residual pain. After supine positioning, a 4-cm skin incision is placed transversely from SAIS in a medial direction. This allows for supra- and infrainguinal dissection. The subcutaneous tissue is bluntly separated freeing the fascia and enabling identification of the inguinal ligament, the lateral sartorius muscle border, and the fascia lata. Once the fascia is opened, the LFC nerve usually can be found in a triangle between the SAIS laterally, the inguinal ligament above, and the sartorius muscle medially. The nerve is then followed proximally to its point of compression toward the inguinal ligament. Now step-by-step decompression of the nerve is carried out by nicking the inguinal ligament, sartorius muscle or other compressive structures. Sometimes the nerve is covered by an own fascia layer on its way from the abdominal space into the thigh, which than should also be incised. When accessing the nerve via a retroperitoneal route, an incision is placed above and parallel to the inguinal

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ligament centering the anterior superior iliac spine. Then, the aponeurosis of the external oblique muscles is split. The fibers of the internal oblique and transversus abdominis muscles are dissected to allow identification of the nerve underneath the iliac fascia heading toward the SAIS.50 At this point, decompression can be performed. Authors postulate a better feasibility of nerve detection51 by this more invasive approach. In case the nerve is transected intra-abdominally, the stump should remain without any other compression deep in the abdominal space (e.g., iliac fascia). In conclusion, the majority of patients can be treated conservatively, and will only have transient symptoms. In refractory cases, surgery is an option. We prefer simple decompression at the inguinal level as the first surgical treatment option. In severe debilitating cases with prior recurrent surgery, we see intrapelvic transection as an option. For this, we can also enter from below the ligament. The nerve can be followed along its intrapelvic course by using a retractor or a retractor-held endoscope. However, there still is ongoing debate whether the nerve should be approached from a supra- or infrainguinal access. Moreover, there is disagreement whether decompression or neurotomy is the most appropriate primary surgical treatment. There are no reliable data assessing large patient collectives favoring one or the other method.47,49

14.1.5 Ilioinguinal Nerve/ Iliohypogastric Nerve/Genitofemoral Nerve These nerves are provided by T12–L3. Clinically, the supplied area may vary significantly, overlapping also with the pudendal nerve, complicating a clear diagnosis. MRI and ultrasound may exclude space-occupying masses. However, true entrapment syndromes of these nerves are rarities. Most of the neuropathies arise after iatrogenic manipulation.52 When reoperating, it can be very difficult to find the nerves within in the scar due to their small diameter. In analogy to Morton’s neuroma or meralgia, a deep nerve resection can be taken into account.

14.1.6 Femoral Nerve The femoral nerve is built by L1–L4 contributions. It follows the psoas muscle dorsally and laterally and clings to the femoral vessels entering the thigh underneath the inguinal ligament. At this point, there are variants in the branching pattern.

Compressive Lesions of the Lower Limb and Trunk Although the space beneath the inguinal ligament is narrow, primary compression neuropathies of the femoral nerve are uncommon. When it comes to traumatic or iatrogenic lesion due to surgery, positioning, or compressive hematomas—either inguinal or retroperitoneal—the nerve is highly susceptible to secondary compression53 (e.g., by scar). Depending on the level of impairment, not only knee extension but also hip flexion due to weakness of quadriceps and iliopsoas muscle occurs. Sensory areas comprise median femoral cutaneous and saphenous nerve. MRI and ultrasound rule out secondary causes. Electrophysiological assessment reveals depth of nerve damage. Treatment depends on the underlying pathology necessitating either trans/retroperitoneal or inguinal approach for nerve decompression. If compression in the vicinity of the inguinal ligament is suspected, an incision parallel to it allows exploring the nerve’s intra- and extrapelvic portion. Usually, the nerve lies lateral to the femoral vein and artery. By either palpation or ultrasound, the vessels can easily be depicted and marked on the skin. After incision, the subcutaneous fat is mobilized and the fascia identified. Incision of the fascia gives view on both vessels and the nerve. There is considerable variation of branching pattern and level. Thus, one has to be particular careful not to harm the rather small-sized muscle and sensory nerve divisions and other nerves such as the femoral branch of the genitofemoral nerve. The inguinal ligament can now be partially incised for proper decompression. As the skin in the groin region is very flexible, the same skin incision suffices for a suprainguinal, i.e., retroperitoneal, inspection and decompression of the femoral nerve.

Otherwise, it can easily be extended into a semilunar incision along the ventral iliac bone. After mobilizing the fat, the aponeurosis of the external oblique muscle, internal oblique muscle, and rectus abdominis muscle can be split bluntly if needed. Once the peritoneum is identified, it can be retracted by self-holding systems giving view to the iliopsoas muscle. Usually, the femoral nerve can be found at its medial border within the muscle’s fascia. Psoas hematomas represent a cause of femoral nerve impairment: in those cases, fascial opening and evacuation of the hematoma significantly improve the situation. The nerve can be easily followed caudally to the inguinal ligament. As already detailed for the LFCN, the femoral nerve can also be visualized from its extra- to intrapelvic course by lifting the inguinal ligament. An endoscope with 30 degrees optics enables following its course from an infrainguinal approach without the need to go transmuscular via the abdominal wall (see ▶ Fig. 14.3). Complete transection of the inguinal ligament is not recommended in order to avoid hernia formation requiring further surgical treatment. Fortunately, the femoral nerve has a high regeneration potential.54 Therefore, in patients with no spontaneous recovery, an attempt to decompress the nerve enabling proper regeneration can be performed.

Saphenous Nerve The saphenous nerve is the terminal sensory branch of the femoral nerve emanating shortly below the inguinal ligament level. It provides sensation to the medial distal thigh as well as the calf. One of its branches is the infrapatellar nerve, which detours the saphenous nerve slightly above the knee level, perforating the distal sartorius muscle. Compression within the adductor canal (“Hunter’s canal”) as an

Fig. 14.3 (a) Endoscopic view; scar tissue (arrows) compressing the femoral nerve (asterisk). (b) Endoscopic view; decompressed femoral nerve (asterisk).

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Compressive Lesions of the Lower Limb and Trunk anatomically given notch provokes pain or sensory impairment in the provided region. Ultrasound and MRI may exclude secondary causes (varices/tumors). If conservative treatment including anesthetic blocks fails, a simple decompression by a small skin incision on the anterior border of the sartorius muscle can help improve the symptoms.55 The point of maximum discomfort should be marked prior to surgery, as this branch is of small caliber (1–2 mm): a bloodless field greatly helps its identification. A true idiopathic entrapment neuropathy of the infrapatellar nerve is very rare with only few reports, whereas iatrogenic lesion is much more frequent.56,57

14.1.7 Obturator Nerve The nerve arises from L2–L4 and heads caudally at the medial border of the psoas muscle. After exiting the pelvis through the obturator foramen, the nerve divides into two main branches. The anterior branch supplies the gracilis, adductor longus, and brevis and pectineus muscle. An articular branch provides the hip joint and the medial thigh. The external obturator and adductor magnus muscles and the medial thigh above the knee are innervated by the posterior branch. Primary entrapment neuropathies of the obturator nerve are rare. Mainly in athletic persons, the thickened fascia of the adductor brevis muscle harbors the danger of obturator nerve entrapment.58 Secondarily, tumors, ganglia, endometriosis, and hypertrophic muscles can cause obturator nerve compression. Furthermore, obturator nerve lesions occur after hip or pelvic surgery.59 Clinically, patients present with pain and sensory impairment on the medial thigh as well as weakness of leg adduction. Electrophysiology reveals rarefication of voluntary muscle action potentials in EMG of the adductor muscles. Imaging with MRI and neurosonography detects the site and cause of compression along the course of the nerve from its origin in the retroperitoneum, to the pelvis and leg. Treatment depends on the underlying pathology. The first option is NSAID medication and physiotherapy or avoidance of pain-provoking maneuvers. If pain persists, sensorimotor deficits increase, and secondary causes are excluded, decompression of the extrapelvic part of the nerve has been proposed.58 An oblique incision on the lateral aspect of the long adductor muscle allows for blunt dissection of the nerve between the pectineus/long adductor and short adductor muscle. It then can be followed in both directions facilitating proper decompression (▶ Fig. 14.4).

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Fig. 14.4 Surgical access to obturator nerve (yellow loop) identified between pectineus and adductor muscle.

Other authors described a laparoscopic decompression of the intrapelvic nerve portion.60 In cases of tumor or perineural ganglia, the surgical approach can differ. According to the extent of the lesion, even biportal accesses (retroperitoneal—thigh) may be necessary. There are no reliable data on patient’s outcome following surgery. Decision-making remains highly individual and the diagnostic work-up clearly should implement MRI imaging to rule out pelvic or lumbosacral neoplasia or inflammatory disease, and electrophysiology should confirm affection of the obturator-innervated muscles.

14.1.8 Pudendal Nerve/Pudendal Neuralgia Usually, S2–S4 roots contribute to the pudendal nerve. Being a mixed motor-sensory-autonomic nerve, it divides into three main branches: dorsal nerve of the clitoris/penis, perineal nerve, and inferior anal nerve. They supply anal and urethral sphincters and the pelvic floor muscles. The nerve provides sensation to genital (clitoral-vulvarvaginal/scrotal-testicular-penile) and perineal areas.61 Different compression mechanisms have been described in primary pudendal neuralgia, including the sacrospinal or sacrotuberal ligament (alone or combined), the falciform process due to obturator fascia, the piriformis muscle, and the ischial spine.62 In addition, a more distal compression site within the Alcock’s canal was proposed.63 Clinical symptoms mainly consist of genital, perineal, and anal pain and sensory deficits typically aggravated by sitting. Defecation and sexual intercourse are additional pain triggers, having a deep impact on life quality.

Compressive Lesions of the Lower Limb and Trunk Pain is characterized as burning, torsion, or foreignbody feeling. Most of the patients will not use the bike anymore but feel some relief sitting on ringlike cushion. Sensory impairments include all the above-mentioned areas, rending the clinical picture difficult to discern from syndromes of other nerves. Secondary nerve entrapments can be attributed to surgery, tumors, or trauma. Imaging mainly consists of MRI excluding other inflicting pathologies such as tumors, varices, and bony alterations. Electrophysiology may reveal altered conduction velocity or EMG changes in sphincter or bulbospongiosus muscle. Most authors insist on diagnostic-therapeutic blocks using CT- or MRI-guided infiltrations of the nerve at its origin at the spine as well as in Alcock’s canal.61 Surgery can be done in different ways: transgluteal, transperineal, transabdominal (open or by laparoscopy), or transischiorectal.

The approaches include the decompression of the nerve by dissection of compressive portions of the sacrotuberal and sacrospinal ligament. This seems to have no impact on pelvic stability. Some authors perform a transposition of the nerve anterior to the ischial spine in the same session.64 The direct anterior access is provided for the so-called distal entrapment syndrome within the Alcock’s canal. We prefer a transgluteal approach to the nerve. An oblique 5- to 6-cm incision is placed 2 to 3 cm paramedian to the coccyx. After blunt dissection of the gluteus maximus muscle, the sacrotuberal and sacrospinal ligament are identified. The nerve can be found at the cranial border of the sacrotuberal ligament entering the space between the two ligaments. At this point, careful decompression can be performed by sectioning both ligaments (▶ Fig. 14.5a–d). In our setting, we use intraoperative sphincter EMG to confirm nerve identity.

Fig. 14.5 (a) Skin incision for pudendal nerve decompression. (b) Intraoperative view; retractor holding back the bluntly dissected maximus gluteus muscle giving view on the sacrotuberal ligament. (c) Intraoperative view; partially dissected sacrotuberal ligament (asterisk) with the pudendal nerve (arrow). (d) Intraoperative view; visualization of the pudendal nerve (arrow) after complete ligament dissection.

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Compressive Lesions of the Lower Limb and Trunk Attention has to be paid to the accompanying vessels. Moreover, the vicinity of the sacral roots and the sciatic nerve lateral to the pudendal nerve have to be taken into account. After wound closure in layers, patients can be mobilized immediately. Results show that careful selection for surgery within the mostly chronic pain patients warrants reasonable improvement after nerve decompression even in the long run.65,66 Neuromodulation may help as a rescue strategy.67

References [1] Pokorný D, Jahoda D, Veigl D, Pinskerová V, Sosna A. Topographic variations of the relationship of the sciatic nerve and the piriformis muscle and its relevance to palsy after total hip arthroplasty. Surg Radiol Anat. 2006; 28(1):88–91 [2] Giuliano Heinen CP, Schmidt T, Kretschmer T. Endoscopically assisted piriformis-to-knee surgery of sciatic, peroneal, and tibial nerves: technical note. Neurosurgery. 2015; 11 Suppl 2:37–42, discussion 42 [3] Cassidy L, Walters A, Bubb K, Shoja MM, Tubbs RS, Loukas M. Piriformis syndrome: implications of anatomical variations, diagnostic techniques, and treatment options. Surg Radiol Anat. 2012; 34(6):479– 486 [4] Hernando MF, Cerezal L, Pérez-Carro L, Abascal F, Canga A. Deep gluteal syndrome: anatomy, imaging, and management of sciatic nerve entrapments in the subgluteal space. Skeletal Radiol. 2015; 44(7): 919–934 [5] Reus M, de Dios Berná J, Vázquez V, Redondo MV, Alonso J. Piriformis syndrome: a simple technique for US-guided infiltration of the perisciatic nerve. Preliminary results. Eur Radiol. 2008; 18(3):616–620 [6] Filler AG. Piriformis and related entrapment syndromes: diagnosis & management. Neurosurg Clin N Am. 2008; 19(4):609–622, vii [7] Patil PG, Friedman AH. Surgical exposure of the sciatic nerve in the gluteal region: anatomic and historical comparison of two approaches. Neurosurgery. 2005; 56(1) Suppl:165–171, discussion 165–171 [8] Socolovsky M, Garategui L, Campero A, Conesa H, Basso A. Exposure of the sciatic nerve in the gluteal region without sectioning the gluteus maximus: an anatomical and microsurgical study. Acta Neurochir Suppl (Wien). 2011; 108:233–240 [9] Possover M, Forman A. Pelvic neuralgias by neuro-vascular entrapment: anatomical findings in a series of 97 consecutive patients treated by laparoscopic nerve decompression. Pain Physician. 2015; 18(6):E1139–E1143 [10] Poage C, Roth C, Scott B. Peroneal nerve palsy: evaluation and management. J Am Acad Orthop Surg. 2016; 24(1):1–10 [11] Aprile I, Tonali P, Caliandro P, et al. Italian CTS and other entrapments Study Group. Italian multicentre study of peroneal mononeuropathy: multiperspective follow-up. Neurol Sci. 2009; 30(1):37–44 [12] Spinner RJ, Scheithauer BW, Amrami KK. The unifying articular (synovial) origin of intraneural ganglia: evolution-revelation-revolution. Neurosurgery. 2009; 65(4) Suppl:A115–A124 [13] Baltodano PA, Basdag B, Bailey CR, et al. The positive effect of neurolysis on diabetic patients with compressed nerves of the lower extremities: a systematic review and meta-analysis. Plast Reconstr Surg Glob Open. 2013; 1(4):e24–e29 [14] Maalla R, Youssef M, Ben Lassoued N, Sebai MA, Essadam H. Peroneal nerve entrapment at the fibular head: outcomes of neurolysis. Orthop Traumatol Surg Res. 2013; 99(6):719–722 [15] Ramanan M, Chandran KN. Common peroneal nerve decompression. ANZ J Surg. 2011; 81(10):707–712 [16] Mont MA, Dellon AL, Chen F, Hungerford MW, Krackow KA, Hungerford DS. The operative treatment of peroneal nerve palsy. J Bone Joint Surg Am. 1996; 78(6):863–869

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[17] Humphreys DB, Novak CB, Mackinnon SE. Patient outcome after common peroneal nerve decompression. J Neurosurg. 2007; 107(2):314– 318 [18] Harbaugh KS, Tiel RL, Kline DG. Ganglion cyst involvement of peripheral nerves. J Neurosurg. 1997; 87(3):403–408 [19] Nucci F, Artico M, Santoro A, et al. Intraneural synovial cyst of the peroneal nerve: report of two cases and review of the literature. Neurosurgery. 1990; 26(2):339–344 [20] Spinner RJ, Atkinson JLD, Scheithauer BW, et al. Peroneal intraneural ganglia: the importance of the articular branch. Clinical series. J Neurosurg. 2003; 99(2):319–329 [21] Roganovic Z, Pavlicevic G. Difference in recovery potential of peripheral nerves after graft repairs. Neurosurgery. 2006; 59(3):621–633, discussion 621–633 [22] Zheng C, Zhu Y, Jiang J, et al. The prevalence of tarsal tunnel syndrome in patients with lumbosacral radiculopathy. Eur Spine J. 2016; 25 (3):895–905 [23] Dellon AL. Deep peroneal nerve entrapment on the dorsum of the foot. Foot Ankle. 1990; 11(2):73–80 [24] Styf J, Morberg P. The superficial peroneal tunnel syndrome. Results of treatment by decompression. J Bone Joint Surg Br. 1997; 79(5): 801–803 [25] Franco MJ, Phillips BZ, Lalchandani GR, Mackinnon SE. Decompression of the superficial peroneal nerve: clinical outcomes and anatomical study. J Neurosurg. 2017; 126(1):330–335 [26] Yuebing L, Lederman RJ. Sural mononeuropathy: a report of 36 cases. Muscle Nerve. 2014; 49(3):443–445 [27] Flachenecker P, Janka M, Goldbrunner R, Toyka KV. Clinical outcome of sural nerve biopsy: a retrospective study. J Neurol. 1999; 246(2): 93–96 [28] Ruth A, Schulmeyer FJ, Roesch M, Woertgen C, Brawanski A. Diagnostic and therapeutic value due to suspected diagnosis, long-term complications, and indication for sural nerve biopsy. Clin Neurol Neurosurg. 2005; 107(3):214–217 [29] Chhabra A, Williams EH, Subhawong TK, et al. MR neurography findings of soleal sling entrapment. AJR Am J Roentgenol. 2011; 196(3): : W290–W297 [30] Williams EH, Rosson GD, Hagan RR, Hashemi SS, Dellon AL. Soleal sling syndrome (proximal tibial nerve compression): results of surgical decompression. Plast Reconstr Surg. 2012; 129(2):454–462 [31] Logullo F, Ganino C, Lupidi F, Perozzi C, Di Bella P, Provinciali L. Anterior tarsal tunnel syndrome: a misunderstood and a misleading entrapment neuropathy. Neurol Sci. 2014; 35(5):773–775 [32] Krishnan KG, Pinzer T, Schackert G. A novel endoscopic technique in treating single nerve entrapment syndromes with special attention to ulnar nerve transposition and tarsal tunnel release: clinical application. Neurosurgery. 2006; 59(1) Suppl 1:ONS89–ONS100, discussion ONS89–ONS100 [33] Ahmad M, Tsang K, Mackenney PJ, Adedapo AO. Tarsal tunnel syndrome: A literature review. Foot Ankle Surg. 2012; 18(3):149–152 [34] Takakura Y, Kitada C, Sugimoto K, Tanaka Y, Tamai S. Tarsal tunnel syndrome. Causes and results of operative treatment. J Bone Joint Surg Br. 1991; 73(1):125–128 [35] Pomeroy G, Wilton J, Anthony S. Entrapment neuropathy about the foot and ankle: an update. J Am Acad Orthop Surg. 2015; 23(1):58–66 [36] Valero J, Gallart J, González D, Deus J, Lahoz M, PhD JV. Multiple interdigital neuromas: a retrospective study of 279 feet with 462 neuromas. J Foot Ankle Surg. 2015; 54(3):320–322 [37] Xu Z, Duan X, Yu X, Wang H, Dong X, Xiang Z. The accuracy of ultrasonography and magnetic resonance imaging for the diagnosis of Morton’s neuroma: a systematic review. Clin Radiol. 2015; 70(4): 351–358 [38] Kasparek M, Schneider W. Surgical treatment of Morton’s neuroma: clinical results after open excision. Int Orthop. 2013; 37(9):1857– 1861– (SICOT) [39] Pace A, Scammell B, Dhar S. The outcome of Morton’s neurectomy in the treatment of metatarsalgia. Int Orthop. 2010; 34(4):511–515 [40] Assmus H. Morton metatarsalgia. Results of surgical treatment in 54 cases. Nervenarzt. 1994; 65(4):238–240

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Compressive Lesions of the Lower Limb and Trunk [41] van Slobbe AM, Bohnen AM, Bernsen RM, Koes BW, Bierma-Zeinstra SM. Incidence rates and determinants in meralgia paresthetica in general practice. J Neurol. 2004; 251(3):294–297 [42] Kitchen C, Simpson J. Meralgia paresthetica. A review of 67 patients. Acta Neurol Scand. 1972; 48(5):547–555 [43] Omichi Y, Tonogai I, Kaji S, Sangawa T, Sairyo K. Meralgia paresthetica caused by entrapment of the lateral femoral subcutaneous nerve at the fascia lata of the thigh: a case report and literature review. J Med Invest. 2015; 62(3–4):248–250 [44] Ghent WR. Meralgia paraesthetica. Can Med Assoc J. 1959; 81(8): 631–633 [45] Carai A, Fenu G, Sechi E, Crotti FM, Montella A. Anatomical variability of the lateral femoral cutaneous nerve: findings from a surgical series. Clin Anat. 2009; 22(3):365–370 [46] Ghent WR. Further studies on meralgia paresthetica. Can Med Assoc J. 1961; 85(16):871–875 [47] Williams PH, Trzil KP. Management of meralgia paresthetica. J Neurosurg. 1991; 74(1):76–80 [48] Cheatham SW, Kolber MJ, Salamh PA. Meralgia paresthetica: a review of the literature. Int J Sports Phys Ther. 2013; 8(6):883–893 [49] de Ruiter GCW, Wurzer JAL, Kloet A. Decision making in the surgical treatment of meralgia paresthetica: neurolysis versus neurectomy. Acta Neurochir (Wien). 2012; 154(10):1765–1772 [50] Aldrich EF, van den Heever CM. Suprainguinal ligament approach for surgical treatment of meralgia paresthetica. Technical note. J Neurosurg. 1989; 70(3):492–494 [51] Alberti O, Wickboldt J, Becker R. Suprainguinal retroperitoneal approach for the successful surgical treatment of meralgia paresthetica. J Neurosurg. 2009; 110(4):768–774 [52] Kretschmer T, Antoniadis G, Börm W, Richter HP. Iatrogenic nerve injuries. Part 1: Frequency distribution, new aspects, and timing of microsurgical treatment. Chirurg. 2004; 75(11):1104–1112 [53] Craig A. Entrapment neuropathies of the lower extremity. PM R. 2013; 5(5) Suppl:S31–S40 [54] Kim DH, Kline DG. Surgical outcome for intra- and extrapelvic femoral nerve lesions. J Neurosurg. 1995; 83(5):783–790 [55] Kalenak A. Saphenous nerve entrapment. Oper Tech Sports Med. 1996; 4(1):40–45

[56] House JH, Ahmed K. Entrapment neuropathy of the infrapatellar branch of the saphenous nerve. Am J Sports Med. 1977; 5(5):217– 224 [57] Figueroa D, Calvo R, Vaisman A, Campero M, Moraga C. Injury to the infrapatellar branch of the saphenous nerve in ACL reconstruction with the hamstrings technique: clinical and electrophysiological study. Knee. 2008; 15(5):360–363 [58] Bradshaw C, McCrory P, Bell S, Brukner P. Obturator nerve entrapment. A cause of groin pain in athletes. Am J Sports Med. 1997; 25 (3):402–408 [59] Tipton JS. Obturator neuropathy. Curr Rev Musculoskelet Med. 2008; 1(3–4):234–237 [60] Rigaud J, Labat J-J, Riant T, Bouchot O, Robert R. Obturator nerve entrapment: diagnosis and laparoscopic treatment: technical case report. Neurosurgery. 2007; 61(1):E175–, discussion E175 [61] Popeney C, Ansell V, Renney K. Pudendal entrapment as an etiology of chronic perineal pain: Diagnosis and treatment. Neurourol Urodyn. 2007; 26(6):820–827 [62] Robert R, Prat-Pradal D, Labat JJ, et al. Anatomic basis of chronic perineal pain: role of the pudendal nerve. Surg Radiol Anat. 1998; 20(2): 93–98 [63] Hruby S, Ebmer J, Dellon AL, Aszmann OC. Anatomy of pudendal nerve at urogenital diaphragm–new critical site for nerve entrapment. Urology. 2005; 66(5):949–952 [64] Robert R, Labat J-J, Bensignor M, et al. Decompression and transposition of the pudendal nerve in pudendal neuralgia: a randomized controlled trial and long-term evaluation. Eur Urol. 2005; 47(3):403–408 [65] Stav K, Dwyer PL, Roberts L. Pudendal neuralgia. Fact or fiction? Obstet Gynecol Surv. 2009; 64(3):190–199 [66] Hruby S, Dellon L, Ebmer J, Höltl W, Aszmann OC. Sensory recovery after decompression of the distal pudendal nerve: anatomical review and quantitative neurosensory data of a prospective clinical study. Microsurgery. 2009; 29(4):270–274 [67] Valovska A, Peccora CD, Philip CN, Kaye AD, Urman RD. Sacral neuromodulation as a treatment for pudendal neuralgia. Pain Physician. 2014; 17(5):E645–E650

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Thoracic Outlet Syndrome

15 Thoracic Outlet Syndrome Mariano Socolovsky, Daniela Binaghi, and Ricardo Reisin Abstract Thoracic outlet syndrome (TOS), defined as compression of the brachial plexus as it passes from the lower neck into the axilla, is a condition that continues to be plagued by controversy. This controversy stems not so much from so-called true neurogenic thoracic outlet syndrome (TNTOS), which is characterized by muscular atrophy of the intrinsic muscles of the hand, but from the disputed neurogenic thoracic outlet syndrome (DNTOS) variant, with which patients only have sensory symptoms. TNTOS is caused by anatomical compression that can usually be visualized in images, especially magnetic resonance imaging (MRI). Implicated structures include cervical ribs, supernumerary muscles, and anomalous ligaments, among others. It is associated with clear, objective denervation of the intrinsic musculature of the hand, for which prompt decompression surgery is warranted upon diagnosis. Conversely, DNTOS may or may not be accompanied by pathological findings on MRI or computed tomography (CT) scans, and is therefore largely considered a diagnosis of exclusion. In general, it should be treated conservatively, unless prolonged failed conservative treatment is documented. The current authors prefer the supraclavicular approach to decompression, as do many plexus surgeons, though the transaxillary approach is also a widely accepted approach for the treatment of both syndromes. Keywords: thoracic outlet syndrome, chronic nerve compression, brachial plexus, neurolysis, cervicobrachialgia, hand atrophy, cervical rib

15.1 Introduction Thoracic outlet syndrome (TOS) is a chronic nerve compression that can affect the brachial plexus or the subclavian vessels (artery and vein). It is a highly controversial syndrome in terms of its clinical picture, diagnosis, and treatment, lacking absolute consensus on all three counts. The brachial plexus can be compressed proximally within the interscalene space, at the level of its primary trunks, or within the costoclavicular and retropectoral spaces, at the level of its secondary trunks. The term “thoracic outlet syndrome” was initially coined by Peet in 1956.1 However, the phenomenon had been mentioned several times previously in the literature, dating as far back as 1742. The first rib was initially identified as the main compressive element. However, over time several other anatomical landmarks have been implicated—the scalene muscles; Sibson’s fascia; other ligaments, vessels, and aberrant muscles; and a hypertrophied C7 transverse

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process, among others. This multitude of potential offending structures may be why this syndrome has received so many different names over its long history— names such as scalene syndrome, supernumerary rib syndrome, cervical rib syndrome, costoclavicular syndrome, and the current and probably more accurate TOS. The syndrome can be divided grossly into vascular TOS and neurogenic TOS (NTOS). The vascular form can target the subclavian artery, causing distal ischemia, or the subclavian vein, characterized by repetitive thrombosis during exercise, which is called Paget–Schroetter syndrome. The neurogenic counterpart, which is the topic of the current chapter, generally affects the inferior primary trunk, though this can vary. In recent years, subcategorization of neurogenic TOS into so-called true neurogenic TOS (TNTOS) and disputed neurogenic TOS (DNTOS) has become more widely accepted. Of these, the former produces motor changes, including simultaneous atrophy of the thenar and hypothenar eminences and sensory loss in the lower trunk distribution (the so-called GilliattSumner hand).2 In contrast, DNTOS is characterized by sensory changes alone in the upper extremity, including pain that typically spreads through the territory of the lower trunk, but which also can affect the entire upper limb, the neck, and/or the shoulder. By definition, DNTOS is not associated with atrophic changes or sensory loss in the muscles of the hand, lest it be called TNTOS. The first step toward diagnosing TOS is suspecting it. In our experience, many patients bounce between several different physicians, receiving a broad constellation of ineffective treatments. Once the correct diagnosis is made, treatment will depend on the anatomical elements affected, the cause, and the site of compression.

15.2 Diagnosis and Management of TOS 15.2.1 Important Concepts Regarding TOS TNTOS is a well-defined entity, a fact that allows for relatively easy diagnosis and treatment. It predominantly affects young people, typically ranging from 15 to 35 years old. Its symptoms are both motor and sensory: the usual presentation is a Gilliatt-Sumner hand: an atrophy of the thenar and hypothenar eminences (▶ Fig. 15.1), associated with pain, dysesthesias, paresthesias, or hypo/anesthesia in the lower trunk territory, which includes the little finger and medial side of the ring finger, and the medial forearm and arm, with preserved sensation throughout the rest of the hand, mediated by the noncompressed primary upper

Thoracic Outlet Syndrome

Fig. 15.1 Gilliatt-Sumner hand. Note the atrophy of the thenar and the hypothenar eminences of the right hand.

trunk of the brachial plexus. This clinical presentation is almost pathognomonic, since very few other entities share this picture. An intramedullary or extramedullar–intradural tumor or degenerative disease affecting anterior horn neurons—in the latter case, without sensory impairment—can share some of the clinical findings described before. Also, an ulnar neuropathy can share some of the findings of TOS, but the involvement of the thenar eminence as well as the sensory loss in the forearm do not occur in an ulnar nerve lesion. There is a broad constellation of clinical signs and tests described to diagnose both TNTOS and DNTOS such as Adson’s test, Wright’s test, the Roos test, and the Halsted test, among many others. For clinical practice, it is important to note that none of these tests is highly specific or sensitive, with many positive tests present in the normal population. In our experience, two good methods by which to elucidate tension or compression within the thoracic outlet are supraclavicular percussion of the brachial plexus and the interscalene space, and arm abduction associated with contralateral rotation of the head, both of which generate sensory symptoms. This being said, these signs are also neither highly sensitive nor specific. The typical patient who presents with TNTOS is a thin, tall woman with slouching shoulders, though this is not always the rule. Nevertheless, it is extremely uncommon to see an overweight man of short stature with this clinical picture, as his anatomy does not predispose him to lower trunk compression, even in the presence of a cervical rib. Of course, neurophysiological studies will show abnormalities in such patients, as denervation of the thenar and hypothenar muscles is easily demonstrated, also involving the flexor carpi ulnaris and flexor digitorum profundus of the fourth and fifth digit. Other neurophysiological abnormalities can be expected in this picture, as reduced or absent sensory responses in the ulnar nerve and in medial cutaneous nerve of the forearm.

Imaging plays a very important role in the management of both TNTOS and DNTOS. TNTOS is always associated with a compression site, such as a cervical rib, the first rib, an anomalous ligament, and a supernumerary muscle. It is important to obtain a high-quality computed tomography (CT) scan with a bone window of the thoracic outlet, together with a high-quality magnetic resonance imaging (MRI). Both studies will help determine the compression site, thereby confirming the diagnosis and assisting in the planning of subsequent surgery (▶ Fig. 15.2, ▶ Fig. 15.3, ▶ Fig. 15.4). It is important to keep in mind that cervical ribs are present in a relatively high percentage of the normal population.3 As such, the presence of one, on its own, does not confirm TOS. Similarly, the absence of clear pathology on imaging does not rule out the diagnosis of TOS when the clinical and neurophysiological pictures are compatible, since up to one-third of compressive structures are identified during surgery, most of them anomalous ligaments that are difficult to visualize on preoperative MRI. Once TNTOS is diagnosed, our approach is to offer the patient surgical decompression as first-line management. This is a completely different strategy than the one we adopt for DNTOS. In TNTOS, the patient already has distal motor and sensory compromise caused by nerve compression in the proximal limb. Any time delay decompressing the brachial plexus can interfere with eventual motor recovery as, even after decompression, the nerve fibers have a long way to go to reach the hand (nearly 1 m, with a growing speed of 1 mm/day). Our preferred surgical approach is the standard supraclavicular technique. We start with a 6-cm transverse cervical incision, which is a bit shorter than what we generally use to expose the brachial plexus for traumatic injuries. After dissecting the platysma and the cervical aponeurosis, the omohyoid muscle is retracted to provide access to the brachial plexus. It is extremely important to individualize each of the three primary trunks of the brachial plexus under stimulation, as well as the subclavian artery, before starting any resection procedure, to minimize the risk of damaging any of the neurovascular structures—typically the lower trunk, which is being compressed by a cervical rib or some other anomalous structure. Palpation may help to identify the site of compression, especially if it is within the interscalene space. In addition, intraoperative mobilization of the upper limb may be useful for detecting infraclavicular narrowing within the brachial plexus’ path toward the arm. If compression is caused by a ligament, simple sectioning should be enough to correct the problem. However, if a cervical or first rib needs to be resected, Kerrison rongeurs should be used, cautiously, to resect the bone structures, taking care not to damage the plexus and surrounding vessels. Removing the periosteum before rib resection has some advantages, including reduced

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Thoracic Outlet Syndrome

Fig. 15.2 (a) Frontal radiograph of a right cervical rib (arrow). Postoperatory CT coronal reconstruction (b) image demonstrates partial resection (arrow), and the axial reconstruction (c) image shows a prominent tubercle in which the cervical rib was fused. (d) Coronal STIR exhibits a mild signal increase of the lower trunk (arrow) of the brachial plexus secondary to compression. (e) Sagittal T2 shows the inferior trunk (arrow) located above the subclavian artery (SA), and in contact with the first rib tubercle (asterisk). (f) Sagittal PD SPIR demonstrates slight effacement of the typical fascicular nerve appearance and mild signal increase of the lower truck.

Fig. 15.3 Frontal radiograph shows bilateral elongated C7 transverse process (arrows).

bleeding and creating a definitive surgical plane in which no neurovascular structures will be found (▶ Fig. 15.5). The results of surgical decompression obviously depend on the anatomical findings observed during the

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procedure and on the surgical technique. Most of our patients4 evidenced good recovery, both for pain and motor weakness. Hypoesthesia do not always recover so well. Young people operated upon early after the diagnosis is made should, theoretically, recover more quickly. How well and quickly pain symptoms resolve varies. In some patients, a return to normal sensation and/or resolution of pain is almost immediate; meanwhile, others, especially those who present with severe pain that has lasted for more than 6 months prior to surgery, will actually be worse postoperatively. The worsening of sensory symptoms in those patients may be secondary to intraoperative manipulation of the brachial plexus, particularly the lower trunk, when a larger structure such as the first rib has to be resected. Unless actual nerve damage occurs, however, all patients should experience resolution of their sensory symptoms within a short time of surgery, albeit with some patients requiring antineuropathic pain drugs such as pregabalin, at least short term. Some surgeons, especially vascular and thoracic surgeons, prefer the axillary approach. In the literature and in our own experience, both approaches are adequate to decompress the brachial plexus in patients with TOS. We

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Thoracic Outlet Syndrome

Fig. 15.4 (a) Sagittal T2-w shows a scalenus minimus muscle (asterisk) at the interscalene triangle, which is located between the anterior (ASM) and middle (MSM) scalene muscles, and lying anteriorly to C8 (arrow head) and T1 (dashed arrow) nerves. (b) Coronal STIR demonstrates a signal increase of the C8 nerve (arrow).

prefer the supraclavicular approach mostly because we are more familiar with it, as are most brachial plexus surgeons. In addition, because the nerves and vessels are situated in front of the compressive structures with the axillary approach, sometimes greater retraction is necessary.

15.2.2 Important Concepts in DNTOS DNTOS is an extremely controversial entity. Neither its existence nor any benefits of surgery have been adequately documented in the scientific literature. DNTOS is a completely different condition than TNTOS. Therefore, management of the two entities differs completely. The typical clinical picture in a supposed DNTOS patient is neck pain that radiates down into the shoulder and ipsilateral upper limb, with limb pain displaying either a radicular distribution or more classical lower trunk distribution. Patients with DNTOS tend to be older than those with TNTOS, likely because the former is usually not associated with some congenital anatomical variation such as a cervical rib and anomalous ligament, but with degenerative compression of brachial plexus structures. The same clinical signs can be applied to diagnose DNTOS as for TNTOS, but they are neither specific nor sensitive. Therefore, we face a patient with cervical and upper limb pain, normal cervical spine, and neurophysiological studies (again, if there was such denervation, the correct diagnosis would be TNTOS). In this scenario, imaging again plays a very important diagnostic role. In the presence of definite brachial plexus compression on MRI—for instance, caused by a supernumerary scalene muscle or anomalous ligament—the diagnosis of DNTOS is clear. However, often the images are inconclusive and, given the subjectivity of sensory symptoms, ruling out a long list of differential diagnoses is still needed. This list includes other compression syndromes, such as: ulnar and median nerve compression at the elbow or wrist, respectively; fibromyalgia which, by definition, is associated with pain elsewhere as well; repetitive strain syndrome, often related to work; and various psychosomatic conditions. Once all other differential diagnoses have

been excluded, we can presume that the correct diagnosis is DNTOS. An especially problematic scenario exists when a patient suffers from two compressions at once—the socalled double crush syndrome—which makes the diagnosis even more difficult. It is advisable in such cases wherein data are inconclusive (e.g., a cervical rib accompanied only by pain radiating to the distribution of the lower trunk) to initiate conservative medical treatment rather than plan surgery, as for TNTOS. We say this for two main reasons. First, the vast majority of patients will experience symptom amelioration with conservative treatment. And second, even with mechanical compression demonstrated on MRI, the absence of hand atrophy and sensory loss allows for noninvasive treatment as a first choice. In selected patients with very severe pain and a clear compressive structure on MRI or CT scans, this time frame can be shortened. Initial treatment should include teaching the patient to avoid certain postures that aggravate symptoms; physiotherapy, including cervical muscle relaxation and elongation; exercises; and analgesics, dosed in accordance with the patient’s degree of pain. Botulinum toxin injections have been advocated as an effective palliative treatment when more standard conservative measures all fail. All these measures need to be continued over an extended period of time, however—first, because they might be successful, and second, because they may help to rule out work-related, social, or other problems that can cause pain. Consultation with a rheumatologist, pain specialist, psychiatrist, and/or neurologist can be arranged over this period, as well. A minimum of 6 months of conservative treatment is advisable before any kind of surgery for DNTOS is considered. When all of the above-mentioned measures fail, surgical treatment should be considered. For this, the approach is the same as for TNTOS. Again, our preference is the supraclavicular incision already described. If, during the diagnostic work-up, an obviously anomalous structure is found, all efforts need to target its release. Nevertheless, the whole brachial plexus, including the infraclavicular space, should be inspected carefully via this approach, since other compressive structures not discovered on imaging may sometimes be found. When no anomalous compressive structure is found, an anterior

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Fig. 15.5 (a) Classical incision for a supraclavicular approach to the left brachial plexus on a young female patient suffering TOS. (b) The omohyoid muscle and the jugular vein are reclined in order to expose the brachial plexus. (c) The three primary trunks and its branches (yellow loops), are identified. (d) The subclavian artery is also dissected (red loop). The cervical rib can be observed below this structure. (e) The periosteum of the rib is detached before starting bone resection. (f) After bone resection, decompressed brachial plexus structures can be observed and monitored with motor stimulation.

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Thoracic Outlet Syndrome scalenectomy should be performed to release the brachial plexus and subclavian vessels. This surgical maneuver not only entails sectioning the muscle, but actually resecting some portion of it to avoid the possibility of later spontaneous reattachment. Meticulous hemostasis must be achieved prior to closure to avoid a compressive hematoma, secondary fibrosis, or both. Recurrences are not uncommon, due to the abovementioned spontaneous reattachment or due to the formation of new fibrotic tissue encompassing nerve structures. In such patients, the new diagnostic work-up may identify the presence of a new source of compression, at which point a second decompression procedure can be offered to patients, if necessary, taking obvious care to avoid new fibrosis.

15.3 What Does the Literature Say about TOS? For a recent Cochrane review, Povlsen et al5 analyzed the published English literature from 1966 through 2009. Comparisons between studies and between treatments were difficult, because no consensus had been established regarding the diagnosis or treatment of this entity; consequently, different criteria were used both for diagnosis and management decisions. The authors’ final conclusion was that no published evidence exists to indicate the superiority of conservative management versus surgery, or vice versa, in the treatment of TOS. The vast majority of papers failed to differentiate between TNTOS and DNTOS, which made treatment comparisons even more difficult. The authors ultimately concluded that TOS is probably one of the most controversial issues in medicine. Epidemiologically, the prevalence of TOS is yet unknown, even though some authors estimate that it affects roughly 10 individuals per 100,000.6 It is very interesting to note that, in one study on cadaveric dissections, only 10% had what would be considered “normal anatomy.”7 Vascular TOS (arterial or venous) is estimated to exist in 5% of cases, with the rest neurogenic. Of these, only 1 to 3% can be considered TNTOS, while DNTOS accounts for the remainder.3 In the United States, 90% of all TOS cases operated upon have what would be classified as DNTOS, which gives some idea of the rarity of TNTOS and a possible explanation for the findings of Povlsen et al’s study. Patients with DNTOS generally have a worse course, especially in terms of symptomatic relief; on one hand, this is because sometimes no compressive structure can be found during surgery; and on the other, because some of the patients operated upon had some other diagnosis that was missed.8 Another interesting finding described in the Cochrane review was that just one prospective randomized study had been published, even though this pathology had initially been described in the 1740s. This study, by Sheth

and Campbell,9 was methodologically flawed on several fronts. Among these flaws were that it only included patients with DNTOS, excluded patients with a cervical rib, had no control group, and was not double blinded. Moreover, the diagnosis was made by a just single surgeon. In this study, 24 patients operated upon via a supraclavicular approach were compared against 25 patients who underwent a transaxillary approach. Both groups enjoyed symptom improvement versus baseline, though the improvement in pain scale ratings was slightly better in the axillary approach group. The remaining published studies on TOS were retrospective, with just a few exceptions. Among them was the study by Lindgren,10 in which 88% of patients experienced a positive response to physiotherapy, but design concerns were noted. Jordan et al11 reported a good response in 64% of patients who received an infiltration of botulinum toxin, over lidocaine or corticosteroids. Other prospective studies12,13,14,15,16 identified good to excellent responses to surgical treatment, though they also had methodological issues, such as nonrandomization, indeterminate diagnostic criteria, and the lack of double-blind analysis. Unfortunately, these clearly inconclusive data are, at present, the strongest evidence that we have that shows surgery is better than the natural history of the disease or its conservative/medical treatment.

15.4 Conclusion TNTOS, which is characterized by the atrophy of intrinsic hand muscles and sensory loss in the lower trunk distribution, is a very rare clinical syndrome that is caused by compression of the lower trunk of the brachial plexus by some abnormal structure; for this, prompt early decompression is necessary to avoid permanent deficits. Conversely, DNTOS is highly controversial. Its diagnosis should be made by exclusion and its initial treatment should be conservative, including physiotherapy and possibly medication for pain control. A decision to pursue surgery for DNTOS should only be made after at least 6 months’ failed conservative treatment and with careful selection of the patient. At present, considerable retrospective but limited prospective evidence exists on the surgical treatment of either form of TOS, none of it statistically significant, even though such surgery is widely accepted.

References [1] Peet RM, Henriksen JD, Anderson TP, Martin GM. Thoracic-outlet syndrome: evaluation of a therapeutic exercise program. Proc Staff Meet Mayo Clin. 1956; 31(9):281–287 [2] Gilliatt RW, Le Quesne PM, Logue V, Sumner AJ. Wasting of the hand associated with a cervical rib or band. J Neurol Neurosurg Psychiatry. 1970; 33(5):615–624 [3] Fechter JD, Kuschner SH. The thoracic outlet syndrome. Orthopedics. 1993; 16(11):1243–1251

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Thoracic Outlet Syndrome [4] Socolovsky M, Di Masi G, Binaghi D, Campero A, Páez MD, Dubrovsky A. Thoracic Outlet Syndrome: is it always a surgical condition? Analysis of a series of 31 cases operated by the supraclavicular route. Surg Neurol Int. 2014; 5 Suppl 5:S247–S255 [5] Povlsen B, Belzberg A, Hansson T, Dorsi M. Treatment for thoracic outlet syndrome. Cochrane Database Syst Rev. 2010; 20(1):CD007218 [6] Edwards DP, Mulkern E, Raja AN, Barker P. Trans-axillary first rib excision for thoracic outlet syndrome. J R Coll Surg Edinb. 1999; 44(6):362–365 [7] Juvonen T, Satta J, Laitala P, Luukkonen K, Nissinen J. Anomalies at the thoracic outlet are frequent in the general population. Am J Surg. 1995; 170(1):33–37 [8] Wilbourn AJ. The thoracic outlet syndrome is overdiagnosed. Arch Neurol. 1990; 47(3):328–330 [9] Sheth RN, Campbell JN. Surgical treatment of thoracic outlet syndrome: a randomized trial comparing two operations. J Neurosurg Spine. 2005; 3(5):355–363 [10] Lindgren KA. Conservative treatment of thoracic outlet syndrome: a 2-year follow-up. Arch Phys Med Rehabil. 1997; 78(4):373–378

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[11] Jordan SE, Ahn SS, Freischlag JA, Gelabert HA, Machleder HI. Selective botulinum chemodenervation of the scalene muscles for treatment of neurogenic thoracic outlet syndrome. Ann Vasc Surg. 2000; 14(4): 365–369 [12] Bhattacharya V, Hansrani M, Wyatt MG, Lambert D, Jones NAG. Outcome following surgery for thoracic outlet syndrome. Eur J Vasc Endovasc Surg. 2003; 26(2):170–175 [13] Landry GJ, Moneta GL, Taylor LM, Jr, Edwards JM, Porter JM. Long-term functional outcome of neurogenic thoracic outlet syndrome in surgically and conservatively treated patients. J Vasc Surg. 2001; 33(2):312–317, discussion 317–319 [14] Martens V, Bugden C. Thoracic outlet syndrome: a review of 67 cases. Can J Surg. 1980; 23(4):357–358 [15] Redenbach DM, Nelems B. A comparative study of structures comprising the thoracic outlet in 250 human cadavers and 72 surgical cases of thoracic outlet syndrome. Eur J Cardiothorac Surg. 1998; 13(4):353–360 [16] Sällström J, Gjöres JE. Surgical treatment of the thoracic outlet syndrome. Acta Chir Scand. 1983; 149(6):555–560

Traumatic Brachial Plexus Lesions: Clinics, Assessment, and Timing

16 Traumatic Brachial Plexus Lesions: Clinical Aspects, Assessment, and Timing of Surgical Repair Mario G. Siqueira and Roberto S. Martins Abstract Traumatic adult brachial plexus injuries are devastating and usually occur in young male adults involved in motorcycle accidents. In this chapter, we will discuss general aspects of the preoperative evaluation necessary to lead to a diagnosis and eventual indication for surgery in these patients. Starting with the clinical aspects (types and mechanisms of injury, location of the injury and pain), passing through the assessment of the patient (physical evaluation, image studies, electrodiagnostic studies), and ending by discussing the indications and timing for surgical repair, we will briefly cover the most important preoperative aspects of this traumatic disease. This chapter will provide the readers the basic knowledge for the clinical management of traumatic brachial plexus injuries until the decision to operate or not. Keywords: traumatic adult brachial plexus injuries, diagnosis, indications for surgery, timing for surgery

16.1 Introduction Adult posttraumatic brachial plexus palsies are severely debilitating and rather common injuries. Patients with traumatic injuries of the brachial plexus (TIBP) usually lose motor power and sensation of the upper limb and frequently experience disabling neuropathic pain. The exact number of these lesions occurring each year is difficult to ascertain. A North American study of 4,538 polytrauma patients presenting to a tertiary trauma facility found that 1.2% had sustained brachial plexus injuries.1 The National Trauma Data Bank Annual Report 20152 reported that 356,522 suffered moderate to severe traumatic injuries (9 to 24 points on the Injury Severity Score). If we assume that 1.2% of that number is taken as an estimate of traumatic brachial plexus injury prevalence, then roughly 4,000 patients a year sustain these injuries in the United States. Another publication3 suggested that 450 to 500 close supraclavicular injuries occur each year in the United Kingdom. Although the exact incidence is unknown, it is certainly growing, in parallel with the increasing number of high-speed motor vehicle accidents, especially involving motorcycles. The advances in peripheral nerve surgery over the last few decades changed significantly the outcome of brachial plexus lesions treatment. Nowadays, modern surgical techniques can restore useful function in many cases, even to completely paralyzed limbs. However, despite this major

progress, the results from the surgical treatment of traumatic brachial plexus injuries in adults are still far from ideal.

16.2 Types and Mechanisms of Injury The typical patient with a brachial plexus injury is a young man involved in a motorcycle accident. Although his helmet in many cases saves his life, it is not useful to prevent lesions to the brachial plexus when he strikes the ground. The extent of injury is due to the level of energy and to the direction of the force relative to the limb and shoulder. Low-energy injuries (e.g., fall onto the shoulder) cause mostly reversible injuries (stretch), while highenergy (e.g., motorcycle accident) is associated with more significant injuries (rupture and avulsion). Closed injuries produce stretch/contusion lesions and are the most frequent type of TIBP (73%).4 The vast majority of cases of closed TIBP are related to accidents with high-power engines, mainly motorcycles (79%)5 and are usually associated with a traction mechanism, where the arm and shoulder are forcefully distracted away from the neck or trunk. Sudden caudal traction of the shoulder and arm usually injures first the upper roots of the plexus (C5, C6 and/or C7) and cranial traction involves mainly the lower roots (C8 and T1). All roots can be damaged when a massive momentum is transferred, resulting in a flail upper limb. The force of the impact is projected first to the structures with a straighter course from the spine to the arm (C8 and T1 roots and their continuation as the inferior trunk). The structures with a longest anatomical course from fixed points in the neck to fixed points in the shoulder and arm (C5 and C6 roots and their continuation as superior trunk) receive the last impact of the force. The C7 root and associated middle trunk receive an intermediate impact. As a consequence, the lower structures of the brachial plexus suffer more significant injuries (e.g., root avulsion) than more proximally located elements. It should be remembered that the same patient can injury several different elements of the brachial plexus, in varying severity. Open TIBP is less frequent (27%)4 and can be produced by lacerations and gunshot wounds. Lacerations of the plexus can result from sharp transections (knives or glass) or blunt transection (automobile metal, fan and motor blades, animal bites, or open fractures of the shoulder) and can either transect a portion (most common) or the entire

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Traumatic Brachial Plexus Lesions: Clinics, Assessment, and Timing plexus. Vascular lesions are frequently associated with laceration injuries. The penetrating injuries caused by gunshot wounds are also often associated with vascular injuries. Low-velocity missile wounds from handguns usually produce lesions-in-continuity, but can also transect elements. The force associated with the injury varies and depends on the missile caliber, velocity, and angle of entry of the bullet. Missile injuries produced by low-velocity shell fragments damage the nerve elements by direct impact and tend to be associated with less damage to the plexus. High-velocity gunshot injuries damage the nerve elements through three different mechanisms: direct impact (rare), shock wave effects, and cavitation effects. The latter two mechanisms provoke compression and stretching of the nerve.6 These lesions are more intense and usually fail to recover spontaneously. Based on his experience over 18 years with 1,068 patients, Narakas7 developed an epidemiological rule on brachial plexus lesions called “the seven seventies rule”: approximately 70% were motor vehicle accidents; of these accidents, 70% involved motorcycles or bicycles. Of the cycle riders, 70% had multiple injuries: 70% were supraclavicular injuries. Of the supraclavicular injuries, 70% had at least one root avulsed, 70% of the avulsed roots involved the lower nerve root level (C7, C8, T1), and 70% of the avulsions cases developed chronic pain.

16.3 Location of the Injury Traumatic brachial plexus lesions in adults can be supraclavicular or infraclavicular. Supraclavicular lesions (72%)4 involve spinal nerves and brachial plexus trunks. The subdivision of these lesions in relation to the dorsal root ganglion (preganglionic and postganglionic) has a prognostic value and helps in the elaboration of the treatment planning. Preganglionic lesions essentially point to a permanent loss of that root without possibility of direct repair, while postganglionic lesions are amenable to repair since they represent distal axons which can regenerate. There are signs and physical findings that suggest a preganglionic injury8: (1) absence of Tinel’s sign in supraclavicular region (absence of proximal spinal nerve stump); (2) Horner’s syndrome (sympathetic ganglion injury/T1 level); (3) injury to very proximal nerves such as dorsal scapular nerve (atrophy of rhomboid muscles), long thoracic nerve (winged scapula), and phrenic nerve (ipsilateral hemidiaphragm paralysis); (4) cervical paraspinal muscle weakness and denervation (seen in electromyography [EMG] studies), and loss of posterior neck sensation (dorsal rami of cervical nerve roots injury); (5) pseudomeningocele in image studies (development of meningeal diverticulum after healing of torn nerve root sleeve); (6) intact sensory nerve action potentials in the area of sensory deficit (absence of wallerian degeneration of the sensory axons owing to the position of sensory nerve cells in the dorsal root ganglion); and (7) severe

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Table 16.1 Roots-relevant gross motor function Root

Motor function

C5

Shoulder abduction, extension, and external rotation; some elbow flexion

C6

Elbow flexion, forearm pronation and supination, some wrist extension

C7

Diffuse loss of function in the extremity without complete paralysis of a specific muscle group, elbow extension, consistently supplies the latissimus dorsi

C8

Finger extensors, finger flexors, wrist flexors, hand intrinsics

T1

Hand intrinsics

pain in an anesthetic extremity. Pre- and postganglionic injuries may coexist, the full extent of the lesion being difficult to perceive until surgical exploration is undertaken. Infraclavicular lesions (28%)4 usually occur at the cord and terminal branches’ levels. Combined supra/infraclavicular lesions are possible and seem to occur in 10% of patients.7 The motor neurologic deficits can be separated according to each root involved (▶ Table 16.1), but usually they are organized in patterns according to the level of the injury.9 Supraclavicular injuries can produce four patterns of injury: (1) upper arm type (C5/C6 nerve roots/upper trunk) produces loss of shoulder abduction and of elbow flexion, together with loss of sensation in the shoulder, outside of the arm, and the thumb; (2) the extended upper arm type (C5/C6/C7 nerve roots/upper and middle trunks), besides the same loss of movement in shoulder and elbow as the previous pattern, also presents loss of elbow extension and sometimes of wrist extension (variable as C8 too also supplies the wrist extensors); (3) in the lower upper arm type (C8, T1 nerve roots/inferior trunk), patients will maintain shoulder and elbow strength but will lose hand function associated with hand numbness in at least the ring finger and small finger; and (4) in total arm type (C5–T1/all trunks), the patient presents a complete paralysis of the entire upper limb, usually referred as “flail arm.” Infraclavicular injuries also can produce three different patterns of injury: (1) lateral cord/musculocutaneous nerve pattern produces loss of elbow flexion, (2) in medial cord/median and ulnar nerves pattern, the patient loses finger flexion and intrinsic hand function; and (3) in posterior cord/axillary and radial nerves, the patient loses shoulder abduction (partially) and elbow and wrist extension. Sensory examination is also important in locating the lesion, as deep pressure sensation may be the only clue to continuity in a nerve with no motor function or other sensation. When the examiner apply a full pinch to the nail base and pull the patient’s finger outward, any burning sensation suggests continuity of the tested nerve. The thumb is related to C6 root, the middle finger to C7, and the little finger to C8.

Traumatic Brachial Plexus Lesions: Clinics, Assessment, and Timing

16.4 Pain Pain is present in up to 80% of adult patients who sustained a brachial plexus injury.10 Usually, it is reasonably controlled with drugs and subsides within months. When the pain is intense and starts early, a diagnosis of differentiation and probable root avulsion is made. This severe neuropathic pain reacts poorly to conventional therapy and has two distinct features: constant burning background pain and periodic sharp paroxysms of shooting pain. A considerable number of patients with root avulsions and this severe type of pain will need a procedure for intraspinal coagulation of the dorsal root entry zone as their definitive treatment.

16.5 Evaluation of Brachial Plexus Function and Diagnosis The aim of the evaluation of brachial plexus function is to determine as accurately as possible the localization and extent of the lesion. Based on the information derived from this evaluation, a decision whether the patient is a candidate for early surgery or for a period of further observation usually can be made. Physical, electrophysiological, and imaging evaluations should be done. Whatever the clinical picture, all patients with traumatic paralysis of the brachial plexus who have not shown signs of recovery by the 30th day after the injury should undergo additional work-up, including electrodiagnostic tests and image evaluations, in order to come to a decision regarding surgery.

16.5.1 Physical Evaluation Patients should be evaluated early on, but this is often not possible owing to delayed referral or because in many cases the brachial plexus lesion is only one part of a multisystemic trauma, and either the deficits are overlooked or their evaluation is deferred while life-threatening injuries are treated.11 The standard advanced trauma life support protocol should be followed. Abrasions to the head, helmet, or shoulder suggest supraclavicular injury, while Horner’s syndrome (ptosis, enophthalmos, and miosis) suggests a lower plexus lesion with lesion of the sympathetic ganglion at T1 level. Diminished or absent pulses suggest vascular injury. The early patient’s postinjury neurological status permits the determination by the nerve surgeon of the neurological evolution in subsequent clinical evaluations. Details about the mechanism of injury as well as associated injuries are essential for lesion localization and treatment planning. Information about the type and severity of pain is also important and should be documented. Having in mind the possibility of associated spine and spinal cord lesions, a thorough neurological examination should be done. The active and passive ranges of motion of the upper limb should be recorded, as well as the presence or absence of reflexes.

Table 16.2 Key sensory areas Root

Key sensory area

C5

Skin over deltoid

C6

Thumb and index finger

C7

Middle finger

C8

Ulnar two fingers but particularly little finger

T1

Inner arm

The motor power of every muscle related to the brachial plexus of the injured limb should be evaluated and documented according to the Medical Research Council System Scale from grade 0 to grade 5. When performing the motor examination, keep in mind that most individual muscles have contributions from multiple cervical levels. The sensibility of the affected limb is also evaluated and documented. The examination of some key sensory areas may give precise information about the affected nerve roots (▶ Table 16.2). It is important to note what is real loss of sensation and what the patient perceives as altered sensation. Dry skin is a sign of loss of sweatingmotor function. The production of a shooting nerve–like sensation when the examiner taps along the affected plexus elements (Tinel’s sign) suggests an injury farther from the spinal cord. Over time, if the location of the Tinel sign moves down the arm toward the hand, it is a sign that the injury is repairing itself. This clinical evaluation will permit diagnosing if the plexus is totally or partially compromised. However, it is important to bear in mind that this gradation is not static and that brachial plexus injuries are, in the great majority of cases, a blend of complete and incomplete injured elements. The clinical course should be followed by means of repeated (monthly) clinical examinations.

16.5.2 Image Studies Plain X-rays of the neck and shoulder can depict first and second rib fractures, clavicle fracture, fracture of the transverse process of the cervical spine, fracture of the scapula, and shrapnel from gunshot wounds, associated with the brachial plexus injury. Chest X-rays produced after inspiration and expiration can demonstrate the presence of hemidiaphragm elevation and immobility suggesting a phrenic nerve injury and possible proximal C5 injury (▶ Fig. 16.1). Computed tomography myelography (CTM) has a reported accuracy greater than 90%,12,13 especially when combined with data from clinical examination, in the demonstration of nerve root status (presence, disruption, or absence) and of pseudomeningocele formation (▶ Fig. 16.2). For demonstration of those diverticulum consequent to healing of torn nerve sleeve filled with intrathecal contrast, the exam should be done at least 1 month after the injury to allow time for its formation and to allow edema and blood clots in the area of the nerve root to resolve. Although highly suggestive, these

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Traumatic Brachial Plexus Lesions: Clinics, Assessment, and Timing

Fig. 16.1 Chest X-rays after inspiration (a) and expiration (b) demonstrating elevation and immobility of the right hemidiaphragm, suggesting a phrenic nerve injury.

Fig. 16.2 Axial image of cervical CTM showing complete avulsion of ventral and dorsal roots at the right side with formation of pseudomeningocele. Note the normal roots at the left side (arrows).

Fig. 16.4 Coronal T2-weighted magnetic resonance image showing a giant pseudomeningocele (P) related to lower roots of the brachial plexus.

pseudomeningoceles do not provide proof of rootlet avulsion and this examination presents false-positive and false-negative results ranging from 5 to 10%. The drawbacks of the CTM are the possibility to demonstrate only proximal lesions (until the intervertebral foramina)

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Fig. 16.3 Axial image of cervical CTM demonstrating complete avulsion of right ventral and dorsal roots.

(▶ Fig. 16.3) and its invasive nature. Although CTM is still considered to be the “gold standard” by some authors for studying root lesions, the noninvasive nature and the image details of the entire brachial plexus are responsible for the increasing popularity of magnetic resonance imaging (MRI). Techniques such as fast imaging using steadystate acquisition, MR neurography, and high-field 3-T MRI can demonstrate spinal nerve root lesions with high resolution, matching the diagnostic accuracy of CTM.13,14 Besides providing a noninvasive means of detecting nerve root avulsion and easily demonstrating abnormal cerebrospinal fluid collection of pseudomeningoceles in T2weighted images (▶ Fig. 16.4), MRI can also show spinal cord edema (an indirect sign of nerve root avulsion), postganglionic lesions such as postinjury fibrosis and neuromas, and associated inflammation or edema (▶ Fig. 16.5). Although MRI probably will become the most important method for evaluation of brachial plexus injuries, the possibility of false-positives is still a disadvantage of the technique. Associated injury to major vessels has been reported in TBPI to be as high as 23% in some series.7 They are more frequently in infraclavicular lesions, usually involving subclavian artery and vein or

Traumatic Brachial Plexus Lesions: Clinics, Assessment, and Timing

Fig. 16.5 Magnetic resonance image (diffusion sequence) showing postganglionic lesion-in-continuity of the lower trunk and cords (arrows).

the axillary artery. In cases of suspected arterial damage, a conventional angiography, CT angiography, or MR angiography should be performed. An angiography should always be done in cases of gunshot wound to the plexus because of the possibility of early vascular lesion and posterior formation of a pseudoaneurysm.

16.5.3 Electrodiagnostic Studies A preoperative electrodiagnostic protocol usually includes nerve conduction studies and needle EMG. Besides the importance of the nerve conduction velocity analysis in diagnosing preganglionic lesions that was mentioned earlier, these evaluations are useful in investigating neuropraxic injuries. Injured motor axons continue to conduct action potentials for several days, but as wallerian degeneration proceeds, this ability disappears. If distal motor conduction is positive after this period, even though the related muscles are still paralyzed, the injury is probably a conduction block (neuropraxia). EMG can determine the distribution and extent of the lesion, can evaluate muscles that are difficult to test clinically, and can quantify the extent of denervation. Because of wallerian degeneration, the EMG signs of denervation (polyphasic, fibrillation, positive sharp waves) are not reliably demonstrated until 3 to 4 weeks after nerve injury,15 and for this reason, this examination should not be done earlier. Another important use of EMG examinations is in serial evaluations of the injury to search for signs of reinnervation, which are seen several weeks before the onset of detectable voluntary muscle contraction.

16.6 Indications for Surgery Until the 1960s, most brachial plexus lesions were treated conservatively. Patients were monitored for over 12 to 18 months for recovery of any function, and after this period any residual deficit was pronounced permanent. When a

decision for surgical treatment was made (uncommon), the customary techniques applied at that time were shoulder fusion, elbow fusion, wrist and finger tenodesis, and transhumeral amputation. With the introduction of the surgical microscope in the late 1960s, the results improved and brachial plexus surgery became more frequent. For multisystem trauma patients, the initial management nowadays is directed toward the associated lifethreatening conditions, which include head, spinal, chest, and vascular injuries. The need for surgical treatment of the brachial plexus lesion will depend on the degree of preliminary regeneration: approximately two-thirds of the cases will recover spontaneously over the first months. Surgery should be performed in the absence of clinical substantial spontaneous recovery or electrical evidence of recovery, or when spontaneous recovery is impossible. During the variable observation period, physical therapy should be provided to prevent contractures and to strengthen functioning muscles. Virtually all patients without significant spontaneous recovery may benefit from microsurgical reconstruction of the brachial plexus, but some contraindications to surgery do exist: joint contractures, late referral, advanced patient age, additional injuries or medical conditions, lack of patient motivation to follow a long period of rehabilitation, and lack of patient understanding of surgical goals.

16.7 Timing of Surgery To achieve good results in the surgical treatment of traumatic brachial plexus lesions, the timing of surgery is extremely important. When patients are operated too late, the denervated muscles will undergo the process of denervation atrophy and become refractory to reinnervation. On the other hand, too early surgeries may interfere in the possibility of spontaneous recovery. Immediate or early (3–4 weeks postinjury) exploration and repair of the brachial plexus is performed only in sharp, open injuries. About one-third of the patients with lacerating injuries to the brachial plexus undergo acute surgical exploration because of suspected or angiographically proven vascular injuries, and nerve surgeons should be involved in this emergency procedure, first to assess the nerve damage and secondly to guide the vascular surgeon in dissection of the vessels that present a close relationship to the plexus elements. Only plexus elements sharply sectioned without contusion of the stumps should be immediately repaired. If the injured elements present any evidence of contusion, they should be tagged to adjacent fascia to lessen retraction and re-exploration should be performed 3 to 4 weeks later. This time period allows for better identification of the injury zone in the nerve stumps. Early intervention is also indicated in cases of increasing neurological deficit, which may be associated with progressive pain due to hematoma, arteriovenous fistula, or pseudoaneurysm.

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Traumatic Brachial Plexus Lesions: Clinics, Assessment, and Timing Kline16 observed in his large surgical series that among the closed stretch/contusion injuries of the brachial plexus, 40% of C5–C6 injuries and 15% of C5–C7 injuries spontaneously recovered in 3 to 4 months. Although timing is controversial for stretch injuries, it seems reasonable, based in Kline’s observations, to operate those lesions 4 to 6 months after the injury. During this time, spontaneous recovery could occur and axonal regeneration could reach the target muscle before irreversible motor end plate degeneration occurs. However, in the same period of time, only 5% of C5–T1 (flail arm) lesions had functional recovery and this finding encouraged an earlier exploration and repair for closed complete lesions, especially when a multilevel preganglionic lesion is detected. Generally, complete lesions are explored and repaired 3 months after injury. Low-velocity gunshot wounds are usually treated later on (3–4 months), just like in cases of stretch/contusion lesions, because most of these lesions have a neuropraxic component. On the other hand, high-velocity gunshot wounds are usually associated with significant soft-tissue damage and sometimes with vascular injuries as well, and therefore demand an earlier surgical exploration.

16.8 Treatment The surgical treatment of traumatic injuries to the brachial plexus is based on a combined analysis of the type of injury, possibility of reconstruction, and personal philosophy of the surgeon, and will be dealt with in the next chapter.

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References [1] Midha R. Epidemiology of brachial plexus injuries in a multitrauma population. Neurosurgery. 1997; 40(6):1182–1188, discussion 1188– 1189 [2] American College of Surgeons. National Trauma Data Bank Annual Report. Chicago, IL; 2015 [3] Goldie BS, Coates CJ. Brachial plexus injury: a survey of incidence and referral pattern. J Hand Surg [Br]. 1992; 17(1):86–88 [4] Kim DH, Cho Y-J, Tiel RL, Kline DG. Outcomes of surgery in 1019 brachial plexus lesions treated at Louisiana State University Health Sciences Center. J Neurosurg. 2003; 98(5):1005–1016 [5] Faglioni W, Jr, Siqueira MG, Martins RS, Heise CO, Foroni L. The epidemiology of adult traumatic brachial plexus lesions in a large metropolis. Acta Neurochir (Wien). 2014; 156(5):1025–1028 [6] Samardzic MM, Rasulic LG, Grujicic DM. Gunshot injuries to the brachial plexus. J Trauma. 1997; 43(4):645–649 [7] Narakas AO. The treatment of brachial plexus injuries. Int Orthop. 1985; 9(1):29–36 [8] Songcharoen P, Shin AY. Brachial plexus injury: acute diagnosis and treatment. In: Berger RA, Weiss AP, eds. Hand Surgery. Philadelphia, PA: Lippincott Williams & Wilkins; 2003:1005–1025 [9] Spinner RJ, Shin AY, Hébert-Blouin M, et al. Traumatic brachial plexus injury. In: Wolfe SW, Hotchkiss RN, Pederson WC, eds. Green’s Operative Hand Surgery. 6th ed. Philadelphia, PA: Churchill Livingstone Elsevier; 2010:1235–1292 [10] Bruxelle J, Travers V, Thiebaut JB. Occurrence and treatment of pain after brachial plexus injury. Clin Orthop Relat Res. 1988(237):87–95 [11] McGillicuddy JE. Surgical anatomy and management of brachial plexus injury. In: Tindall GT, Cooper PR, Barrow DL, eds. The Practice of Neurosurgery. Vol. 3. Baltimore, MD: Williams & Wilkins 1996:2859–2877 [12] Amrami KK, Port JD. Imaging the brachial plexus. Hand Clin. 2005; 21 (1):25–37 [13] Doi K, Otsuka K, Okamoto Y, Fujii H, Hattori Y, Baliarsing AS. Cervical nerve root avulsion in brachial plexus injuries: magnetic resonance imaging classification and comparison with myelography and computerized tomography myelography. J Neurosurg. 2002; 96(3) Suppl: 277–284 [14] Nakamura T, Yabe Y, Horiuchi Y, Takayama S. Magnetic resonance myelography in brachial plexus injury. J Bone Joint Surg Br. 1997; 79 (5):764–769 [15] Warren J, Gutmann L, Figueroa AF, Jr, Bloor BM. Electromyographic changes of brachial plexus root avulsions. J Neurosurg. 1969; 31(2): 137–140 [16] Kline DG. Timing for brachial plexus injury: a personal experience. Neurosurg Clin N Am. 2009; 20(1):24–26, v

Traumatic Brachial Plexus Injuries: Surgical Techniques and Strategies

17 Traumatic Brachial Plexus Injuries: Surgical Techniques and Strategies Debora Garozzo Abstract Most brachial plexus injuries are not amenable of spontaneous recovery and require surgical treatment. The diagnostic assessment hinges on differentiating between pre- and post-ganglionic injuries, a prerequisite to correctly give the indication for surgery. It is well known that timing for brachial plexus microreconstruction is of paramount importance in determining the procedural outcome, especially when root avulsions are present. In spite of the remarkable progress achieved by imaging in recent years, a thorough surgical exploration still retains its usefulness, since the repair strategy is ultimately dictated by the overall extent and severity of the damage suffered by the brachial plexus. Till the beginning of the 1990s, brachial plexus surgery was mostly based on anatomical graft reconstruction, which unfortunately encompasses a non-negligible percentage of failure inherent to the technique itself, and is not a viable option in avulsive injuries. In recent decades, after Oberlin’s genial intuition inaugurated a new era in brachial plexus reconstruction, this surgical subspecialty has known a renovated interest due to the massive introduction of nerve transfers: these new techniques have dramatically changed its outcome when compared with the results achieved in the past. Yet at present there are still no guidelines that ratify which is the best repair strategy according to the injury pattern: this implies that surgeons still decide what techniques to apply according to their experience and cultural background. Keywords: brachial plexus injury, root avulsions, nerve graft, nerve transfer, free muscle transfer

17.1 Main Principles in Repair Strategy for Brachial Plexus Injuries 17.1.1 Reinnervation Priorities It must be stated as a preliminary remark that complete injuries rule out the possibility to restore the whole function of the upper limb: the reconstruction scheme follows priorities, generally assuming that elbow flexion and shoulder function (stabilization, abduction, and extrarotation) are the primary goals of surgical reinnervation. Elbow extension and restauration of protective sensitivity in the hand are less unanimously advocated.1 Reinnervation of the distal extremity of the upper limb is still out of

our reach, in spite of some promising reports published by Asian surgeons;2 however, it must be emphasized that even in the best cases, only a basic function can ultimately be regained, certainly incomparable with the flexible refinement of the normal hand.

17.1.2 Surgical Approach Brachial plexus exploration was considered mandatory until recent times, when some surgeons started to challenge its validity advocating the remarkable progress of imaging and the fact that nerve transfers have replaced graft reconstruction whenever possible;3,4 especially in cases of partial injuries, distal neurotization aiming to restore the function could be the only repair strategy, the evaluation of the extension and severity of the injury at root level therefore ceasing to be a major concern. However, in our opinion, surgical exploration still retains its value and we regularly perform it. We also reckon that, regardless the overall successful outcome of nerve transfers, anatomical graft reconstruction still retains its advantages and should not be abandoned. Brachial plexus exploration can be performed via two basic approaches: a posterior and an anterior approach. In spite of the initial wave of enthusiasm, the posterior approach proved to be limited in indications. Nowadays surgical exploration is regularly carried out via an anterior approach with few exceptions.

17.2 Repair Strategies A clear evaluation of the type of injury suffered by the plexus is necessary to choose the repair strategy that can offer the best possible functional restoration; thus, each procedure involves an individually designed reconstruction according to the surgical findings. No guidelines are stated and surgeons mostly rely on their personal knowledge and expertise. Surgical techniques basically imply two options: graft reconstruction and neurotization. Graft reconstruction1,5,6,7 can be applied when root continuity with the spinal cord is maintained, such as in cases of complete nerve rupture or severe stretch injuries resulting in the formation of neuromas. Sural nerves are usually harvested (in cases of complete injuries, radial sensory nerve, medial cutaneous nerve, or even the ulnar nerve can become suitable) and used to prepare cable grafts that bridge the two stumps of the nerve whose function must be restored. Graft reconstruction is obviously not appropriate in avulsive injuries and neurotization techniques (also called

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Traumatic Brachial Plexus Injuries: Surgical Techniques and Strategies nerve transfers) are the viable options.8,9,10,11,12,13,14,15,16,17, 18,19,20,21,22 The main concept behind neurotization techniques is that the proximal stump of a nerve (“donor”) still in continuity with the spinal cord is coapted to the distal stump of the nerve (“recipient”) considered the priority to restore. The donor nerve function is obviously estimated of lesser utility or it can be performed by another muscle. The donor and recipient nerves should preferably be in close proximity, thus avoiding the need for an interposition nerve graft or at least reducing its length as much as possible. Three forms of neurotization are available: plexoplexual neurotization, extraplexual neurotization, and distal neurotization. In plexoplexal neurotization,3,5 one of the roots is found ruptured after its exit from the foramen. The most common scenario is C5 root found in continuity with the spinal cord, whereas the other roots are likely to be avulsed: from C5 proximal stump, an interposition graft is bridged to the anterior division from the upper trunk to restore biceps contraction. In extraplexual neurotization, the donor nerve does not belong to the plexus. ▶ Table 17.1 shows the most frequently used donors and their preferable recipients in relation with the most favorable outcome. Distal neurotizations were introduced after the genial intuition of the French surgeon Christophe Oberlin,14 who designed a technique to certainly be considered the Copernican revolution in brachial plexus surgery: fascicles selected from a sound nerve are intraneurally isolated thanks to direct stimulation, severed and coapted with the distal trunk of the recipient nerve. ▶ Table 17.2 illustrates the most frequently used techniques labeled as distal neurotization.15,16,17,18,19,20,21

17.2.1 Repair Strategies Depending on the Injury Pattern In upper brachial plexus injuries, surgery aims to reinnervate shoulder muscles (spinati and deltoid) and biceps. Surgeons usually rely on the spinal accessory to suprascapular nerve transfer to regain spinati muscles; biceps is reinnervated via Oberlin’s technique14 or its variants15,16 and deltoid is restored via Somsak’s procedure.17,18 Alternative options for biceps are pectoral to musculocutaneous nerve transfer and subclavius or thoracodorsal to axillary nerve transfers for deltoid.13 If valid proximal root stumps are available, some surgeons prefer to associate graft reconstruction of the upper trunk with nerve transfers, claiming the outcome is more favorable as it allows restoration of pectoral muscles and median hand sensitivity. Avulsions of the three upper roots are rare; in such case, the repair strategy could encompass the spinal accessory to suprascapular nerve transfer for the spinati muscles, Oberlin’s technique for the biceps, and an intercostal nerve transfer to the long thoracic nerve to functionally restore dentatus anterior (consequently

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providing a more stable shoulder) and to the axillary nerve to reinnervate the deltoid muscle. If a wrist drop is also present due to C7 injury, tendon transfers have been classically considered the standard option, but recently distal transfers (e.g., median nerve to posterior interosseous nerve transfer) have been advocated.21 In (C7), C8, T1 brachial plexus injuries, muscle transfers were the choice in the past, but nowadays nerve transfers (e.g., the brachialis muscle branch of the musculocutaneous to the median nerve transfer to regain finger flexion; ▶ Fig. 17.1) are the preferred option according to many surgeons.19,20,21,22 In total palsies, regardless of the clinical presentation of a flail arm, four different situations can be distinguished.6 About 20% of patients with total palsies immediately after the trauma will present a spontaneous recovery of some hand flexors in the following weeks: in our experience, when wrist and finger flexors score back M3 or plus after the initial paralysis, a repair strategy similar to that applied for upper injuries can be considered (e.g., spinal accessory transfer to regain the spinati and the infraclavicular nerve transfer for the biceps). Yet it must be clear that these injuries have a worse prognosis and less favorable outcome than the “pure” upper plexus injuries. In more than 50% of total palsies, surgical exploration confirms the presence of a viable root stump, usually C5. A plexoplexual neurotization for the biceps and a spinal accessory to suprascapular nerve transfer for the spinati can enable the restoration of shoulder function and elbow flexion. When two root stumps are available, the repair strategy can include the deltoid reinnervation thanks to the reconstruction of the whole upper trunk. In a second stage, an intercostal nerve transfer to the triceps represents a valid option for increasing the functional restoration. If aiming to attempt hand reinnervation, alternative options are contralateral C72 and/or free gracilis muscle transfer.22 In the remaining cases, avulsions of all five roots of the plexus are detected or, if the upper roots are still found in continuity with the spine, the severe fibrosis and scarring of their proximal stumps do not allow for a plexoplexual reconstruction. In such cases, normally the surgical technique resorts to extraplexual nerve transfers, namely, spinal accessory and intercostal nerve transfers. Our personal strategy is to associate with the spinal accessory to suprascapular nerve transfer for the spinati, the harvest of four intercostal nerves from T3 to T6. T3 is coapted to the long thoracic nerve to favor reinnervation of dentatus anterior and therefore enhance shoulder stability, the motor branches of the T4–T6 intercostal nerves are coapted to the musculocutaneous nerve for elbow flexion and their corresponding sensory branches to the lateral root of the median nerve to restore sensitivity on the hand. Both recipient nerves are dissected and cut when branching off the lateral cord.15

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Table 17.1 Extraplexual donor nerves most commonly used for brachial plexus repair (continued) Historical background

Recipient nerve/s

Pros

Cons

Remarks

The author’s experience

First mentioned by Tuttle in United States in 1913, largely popularized in Japan by Kotani in 1963

Suprascapular nerve (SS)/ musculocutaneous nerve (MC)

Excellent donor for the SS

Interposition graft in XI-MC transfer is required

XI-SS nerve transfer can be performed via anterior or posterior approach; according to some authors, the latter provides better results, due to its proximity to the target muscles and the decompression of the SS at the first notch

Routinely used to reinnervate the spinati muscles, by an anterior approach. The posterior approach is used only when anterior exploration revealed distal rupture of the SS that rules out direct XI-SS nerve transfer.

Phrenic nerve

Introduced by Gu in China in the 1980s

Mostly used to restore the biceps

Valid donor

Contraindicated in babies for the high rate of complications if used in patients younger than 3-y-old (respiratory infections, thoracic cage deformities, etc.). No available follow up studies of respiratory function in elderly patients

Harvest can be performed from the supraclavicular area or via video-assisted thoracoscopy at the thorax

Not used for fear of onset of respiratory complications when the patient reaches the third age

Pectoral nerve

Largely popularized by Kline in United States

Mostly used to restore the biceps

Valid donor

Denervation of the pectoral muscles, thus ruling out possibilities of secondary muscle transfer

Adduction is unaffected as supported by other muscles

Seldom used as complete denervation remarkably affects cosmetics

Thoracodorsal nerve

Introduced by Foester in the late 1920s

Axillary nerve Musculocutaneous nerve

Valid donor

Denervation of the latissimus dorsi ruling out possibilities for secondary muscle transfer

Adduction is unaffected as supported by other muscles

Routinely used to reinnervate the axillary nerve being preferred to Somsak’s procedure

Subscapular nerves

Introduced by Foester in the late 1920s and popularized in the 1940s in United States by Steindler

Axillary nerve Musculocutaneous nerve

Valid donor

No cons

Adduction is unaffected as supported by other muscles

Routinely used to reinnervate the axillary nerve being preferred to Somsak’s procedure

Intercostal nerves

First used by Casserini in Italy attempting to restore motor function in paraplegic patients. Popularized by Kotani, Hara and Tsuyama

Mostly the musculocutaneous nerve Other recipients: radial nerve, axillary nerve, long thoracic nerve

Valid donor

Cannot be used in cases of multiple rib fractures, cervical cord injury or Brown Sequard’s injury

Movement in the reinnervated muscle is initially elicited and synchronous with inspiration, autonomization takes about 1 y

Largely used in panavulsive injuries (see text)

(continued)

Traumatic Brachial Plexus Injuries: Surgical Techniques and Strategies

Donor nerve Spinal accessory nerve (XI)

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Historical background

Recipient nerve/s

Pros

Cons

Remarks

The author’s experience

Contralateral C7 (cC7)

Introduced by Gu in Shanghai at the end of the 1980s. His original technique has been later on modified by Xu Lei and Wang Shu Feng (“prespinal way”) According to the different surgical variants, the surgeon can harvest the whole of cC7 or one of the two divisions (anterior or posterior) from the splitting of the middle primary trunk

Mostly advocated to restore hand function.

Valid donor due to the high number of axons

Although safely harvested in the majority of the patients, cC7 can occasionally result in deficits of the extensors. The Asian surgeons describe the possibility of a later recovery Pain and paresthesias in the radial territory of the hand in the donor limb can be permanent

Autonomization of the reinnervated limb from synchronous movement of the donor limb can require more than 5 y and is not guaranteed

Used in lesions with multiple avulsions if the following criteria are met: patient younger than 30 y, slim, no major head injury, surgery within 6 mo after the traumatic event. Indication given in panavulsive injuries with no possibilities to use the intercostal nerves. Used to restore reinnervation in the territory of the upper trunk or in lesions with lower root avulsions to attempt hand rehanimation. Harvest of cC7 is always performed under intraoperative electrodiagnostic tests in order to avoid possible damage to the donor limb. Experience with Gu’s technique mainly

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Donor nerve

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144 Table 17.1 (continued) Extraplexual donor nerves most commonly used for brachial plexus repair

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Table 17.2 Most frequently used distal neurotizations Donor fascicles

Recipient nerve

Pros

Cons

Remarks

The author’s experience

The ulnar to musculocutaneous nerve transfer. Introduced by Oberlin in the beginning of the 1990s has revolutionized brachial plexus surgery Universally known as “Oberlin’s transfer”

Fascicles for the flexor carpi ulnaris (FCU) from the ulnar nerve at the arm

The muscular branches of the musculocutaneous nerve

It can be used even in cases of avulsions of the upper roots regaining excellent biceps function

Only reinnervation of the biceps

It can successfully be used even in late referral cases

We started to apply this nerve transfer according to the original description, later on we modified it using the whole musculocutaneous nerve as recipient and occasionally choosing the median nerve as donor

The double neurotization: modified technique of the above procedure introduced by Oberlin in 2004, largely popularized by Mc Kinnon

Fascicles for the FCU from the ulnar nerve and fascicles for the pronator muscles form the median nerve

FCU fascicles are coapted to the muscular branches of the MC, whereas the fascicles from the median nerve are coapted to the brachialis muscle

Valid reinnervation of biceps and brachialis with increased strength in elbow flexion of the hand

Possibility of complications in the hand

It can be used in late referral cases

No personal experience

The medial cord to musculocutaneous infraclavicular transfer. Introduced by Ferraresi and Garozzo in Italy

Fascicles for the pronator or wrist flexors from the medial part of the medial cord

The whole musculocutaneous nerve cut at its origin form the lateral cord

Valid reinnervation of both biceps and brachialis at the same time

Not possible in those cases of anatomical variants of the lateral cord that branches off for the biceps at the arm level

Although the reinnervation time takes a few months longer than with Oberlin’s transfer, this does not influence the outcome

After the development of this variant of Oberlin’s technique, we have used it routinely and we consider it the best option

The brachialis branch to the median nerve transfer. Introduced by Accioli, popularized in Spain by Palazzi with the development of technical variants

Branch for the brachialis muscle from the musculocutaneous nerve

Fascicles for the AIN (anterior interosseous nerve) and FDS (flexor digitorum superficialis) in the median nerve

Valid reinnervation of finger flexors

Denervation of the brachialis muscle

The fascicles for the AIN and FDS are located in the posterior portion of the median nerve The lateral cutaneous nerve of the forearm can be added in the procedure to improve sensitivity in the median nerve territory

Limited experience but valid results

The triceps to deltoid nerve transfer, generally known as Somsak’s procedure. Introduced by Leechavenvongs (Somsak is his first name) in Thailand in the 1990s, technical variants introduced by Mckinnon in United States and Bertelli in Brazil later on

Branch to the long head of the triceps In the technical variant introduced by Mckinnon, the branch for the medial head

Axillary nerve

Valid reinnervation of deltoid

Reduced strength in the triceps in the early weeks/months after the procedure, not to be used in cases of weak triceps

Usually performed via a posterior approach, via an anterior approach at the axilla level in the technical variant by Bertelli

Limited experience and results less favorable than reported in the literature

Traumatic Brachial Plexus Injuries: Surgical Techniques and Strategies

The technique and its historical background

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Traumatic Brachial Plexus Injuries: Surgical Techniques and Strategies

Fig. 17.1 Findings at brachial plexus exploration. (a) C5 root avulsion: the tip of the scissors is showing the avulsed rootlets. (b) T1 root avulsion. (c) Posttraumatic pseudomeningocele of the upper roots. (d) Bulky neuroma of the upper trunk: note the splitting into the terminal branches of the upper trunk (anterior and posterior contributions, suprascapular nerve) at its distal end. (e) Neuroma-incontinuity of the lateral cord in a gunshot injury in association with a vascular injury (previously repaired by a vascular surgeon): the humeral insertion of the pectoralis major was detached to allow better control of the surgical field. Note that this patient presented an anatomical variant: the splitting of the lateral cord into its terminal branches occurred at the level of the proximal arm instead of infraclavicularly, as usual. (f) Neuroma-in-continuity of the origin of the median nerve, affecting both the lateral and medial roots. (g) Stretch injury of the median nerve associated with an infraclavicular lesion. (h) Neuroma on the proximal stump of the axillary nerve following a rupture at the inlet into the quadrangular space. (i) Rupture of the suprascapular nerve at supraclavicular level.

It must be reminded that intercostal nerve transfer is not always possible (5% of cases in our series), that is, when the patient suffered a severe thoracic trauma with multiple rib fractures and/or when there was also a cervical spinal injury or a Brown Sequard syndrome (consequent to multiple avulsions).6 These cases offer a very limited range of options: especially in the past, a number of surgeons would give up shoulder reinnervation and focus only on biceps function resorting to spinal accessory to musculocutaneous nerve transfer with an interposition graft. In our opinion, this strategy

146

should be abandoned: without any shoulder stability (and in such cases the complete denervation also rules out the possibility to perform a shoulder arthrodesis), in spite of biceps reinnervation, elbow flexion is unlikely to be functional. Probably an option for these desperate cases can be contralateral C7 and its synergic use with free muscle transfers2,23 although this surgical scenario clearly offers further limitations (see ▶ Table 17.1). In infraclavear injuries, surgery mostly focuses on graft repair.3,5

Traumatic Brachial Plexus Injuries: Surgical Techniques and Strategies

17.3 Outcome of Surgical Reinnervation Outcome in brachial plexus microreconstruction is obviously affected by the severity and extension of the injury and the consequently dictated repair strategy but is also influenced by other factors.24,25 The timing of the procedure is a factor of paramount importance in determining a successful outcome. In particular, in avulsive injuries, surgery should not be procrastinated: any loss of time just favors degenerative changes in the denervated muscles, thus jeopardizing the functional validity of the postsurgical reinnervation. In the literature, it has been clearly demonstrated that the best outcome is consequent to procedures performed between 3 and 6 months after the injury, whereas successful outcome progressively drops after 1 year has elapsed from the trauma.1,5,7 Nerve reinnervation is usually considered to proceed at the speed of 1 mm per day: overall results are therefore evident in about 1.5 to 2 years from the date of the surgery, although signs of further improvement have been observed till 5 years after the surgery. Nowadays, results in upper brachial injuries are definitely favorable, even in cases with root avulsions: we can claim we are certainly able to rescue these patients from invalidity restoring a valid shoulder and elbow flexion function in more than 90% of cases.6 Even lower plexus injuries (although series are certainly smaller given their low incidence) seem to present favorable outcome after the introduction of nerve transfers.6,21 On the contrary, for total palsies, it must be honestly admitted that, being surgery unable to restore a functional hand, these patients actually do not regain a valid function of the upper limb and surgery only results in a savage-like procedure. Moreover, we are only able to regain a valid function of the proximal arm in about 60% of cases.6 As a final remark, it must be remembered that in cases of unsuccessful outcome of the nerve repair surgery or when we reckon there is further possibility to improve the results obtained thanks to brachial plexus reconstruction, palliative procedures can improve the functional results.

[4]

[5]

[6]

[7]

[8]

[9]

[10] [11]

[12]

[13]

[14]

[15]

[16]

[17]

[18]

References [1] Siqueira M, Malessy M. Lesiones traumaticas del plexo braquial: aspectos clinicos y quirurgicos. In: Socolovsky M., Siqueira M., Malessy, eds. Introduccion a la cirugia de los nervios perifericos. Buenos Aires. Ediciones Journal; 2013:121–136 [2] Wang SF, Li PC, Xue YH, Yiu HW, Li YC, Wang HH. Contralateral C7 nerve transfer with direct coaptation to restore lower trunk function after traumatic brachial plexus avulsion. J Bone Joint Surg Am. 2013; 95(9):821–827, S1–S2 [3] Garg R, Merrell GA, Hillstrom HJ, Wolfe SW. Comparison of nerve transfers and nerve grafting for traumatic upper plexus palsy: a

[19]

[20] [21]

[22]

systematic review and analysis. J Bone Joint Surg Am. 2011; 93(9): 819–829 Heiner C, Kretschmer T. Adult brachial plexus injuries: surgical techniques and approaches. In: Mahapatra Ak, Midha R, Sinha S, eds. Surgery of Brachial Plexus. Delhi: Thieme; 2016:101–114 Millesi H. Brachial plexus injury in adults. In: Gelbermann RH, ed. Operative Nerve Repair and Reconstruction. Philadelphia, PA: Lippincott; 1991:1285–1328 Garozzo D, Basso E, Gasparotti R, et al. Brachial plexus injuries in adults: management and repair strategies in our experience. Results from the analysis of 428 supraclavicular palsies. J Neurol Neurophysiol. 2013; 5:180 Narakas A. Neurotization in the treatment of brachial plexus injuries. In: Gelberman R, ed. Operative Nerve Repair and reconstruction. Philadelphia, PA: J.B. Lippincott Company; 1991:1329–1358 Kotani PT, Matsuda H, Suzuki T. Trial surgical procedures of nerve transfer to avulsion injuries of plexus brachialis. Proceedings of the 12th Congress of the International Society of Orthopaedic Surgery and Traumatology. Excerpta Med. 1972:348–350 Songcharoen P, Mahaisavariya B, Chotigavanich C. Spinal accessory neurotization for restoration of elbow flexion in avulsion injuries of the brachial plexus. J Hand Surg Am. 1996; 21(3):387–390 Gu YD, Wu MM, Zhen YL, et al. Phrenic nerve transfer for brachial plexus motor neurotization. Microsurgery. 1989; 10(4):287–289 Xu WD, Gu YD, Xu JG, Tan LJ. Full-length phrenic nerve transfer by means of video-assisted thoracic surgery in treating brachial plexus avulsion injury. Plast Reconstr Surg. 2002; 110(1):104–109, discussion 110–111 Tsuyama N, Hara T. Intercostal nerve transfer in the treatment of brachial plexus injury of root avulsion type. In: Delchef J, de Marneffe R, Vander Elst E, eds. Orthopaedic surgery and traumatology. International Congress Series No. 291. Amsterdam: Excerpta Medica; 1973:351–353 Samardzic M, Rasulic LG, Grujicic DM, Bacetic DT, Milicic BR. Nerve transfers using collateral branches of the brachial plexus as donors in patients with upper palsy–thirty years’ experience. Acta Neurochir (Wien). 2011; 153(10):2009–2019, discussion 2019 Oberlin C, Béal D, Leechavengvongs S, Salon A, Dauge MC, Sarcy JJ. Nerve transfer to biceps muscle using a part of ulnar nerve for C5-C6 avulsion of the brachial plexus: anatomical study and report of four cases. J Hand Surg Am. 1994; 19(2):232–237 Ferraresi S, Garozzo D, Buffatti P. Reinnervation of the biceps in C5–7 brachial plexus avulsion injuries: results after distal bypass surgery. Neurosurg Focus. 2004; 16(5):E6 Ferraresi S, Garozzo D, Basso E, Maistrello L, Lucchin F, Di Pasquale P. The medial cord to musculocutaneous (MCMc) nerve transfer: a new method to reanimate elbow flexion after C5-C6-C7-(C8) avulsive injuries of the brachial plexus–technique and results. Neurosurg Rev. 2014; 37(2):321–329, discussion 329 Leechavengvongs S, Witoonchart K, Uerpairojkit C, Thuvasethakul P. Nerve transfer to deltoid muscle using the nerve to the long head of the triceps, part II: a report of 7 cases. J Hand Surg Am. 2003; 28(4): 633–638 Bertelli JA, Kechele PR, Santos MA, Duarte H, Ghizoni MF. Axillary nerve repair by triceps motor branch transfer through an axillary access: anatomical basis and clinical results. J Neurosurg. 2007; 107 (2):370–377 Accioli ZA (1999). Neurotisation de la branche epitrochleenne du median par le brachial anterieur. These doctorale. Universite’ Rene’ Descartes Palazzi S, Palazzi JL, Caceres JP. Neurotization with the brachialis muscle motor nerve. Microsurgery. 2006; 26(4):330–333 Gutierrez Olivera N, De La Red Gallego MA, Gilbert A. In: Mahapatra AK, Midha R, Sinha S, eds. Surgery of Brachial Plexus. Delhi: Thieme; 2016:131–151 Garozzo D. Nerve transfers for shoulder and elbow in adult brachial plexus injuries. In: Mahapatra AK, Midha R, Sinha S, eds. Surgery of Brachial Plexus. Delhi: Thieme; 2016:115–129

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Traumatic Brachial Plexus Injuries: Surgical Techniques and Strategies [23] Tu YK, Chung KC. Surgical procedures for recovery of hand function. In: Chung KC, Yang LJS, McGillicuddy JE, eds. Practical Management of Pediatric and Adult Brachial Plexus Palsies. New York: Elsevier Saunders; 2012:271–300 [24] Socolovsky M, Di Masi G, Battaglia D. Use of long autologous nerve grafts in brachial plexus reconstruction: factors that affect the outcome. Acta Neurochir (Wien). 2011; 153(11):2231–2240

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[25] Socolovsky M, Paez MD. A literature review of intercostal –to-musculocutaneous nerve transfers in brachial plexus injury patients: does body mass index influence result in Eastern versus Western countries? Surg Neurol Int r. 2013; 4:152

Neonatal Brachial Plexus Palsy: Clinical Presentation and Assessment

18 Neonatal Brachial Plexus Palsy: Clinical Presentation and Assessment Thomas J. Wilson and Lynda J-S Yang Abstract In this chapter, we review the epidemiology, risk factors, and typical clinical presentation of neonatal brachial plexus palsy (NBPP). We differentiate between incidence and persistence of NBPP and discuss what these differences mean to the treating physician. We then discuss the typical evaluation of a patient presenting with NBPP, including physical examination, electrodiagnostic studies, and imaging studies. A variety of physical examination tests and grading scales specific to the NBPP patient population have been devised and these are discussed. We further discuss the utility of ultrasound, computed tomographic myelography, and magnetic resonance myelography in the evaluation. Finally, we summarize these evaluation methods by discussing how we determine which patients with NBPP should be considered surgical candidates and which should not. Keywords: neonatal brachial plexus palsy, clinical assessment, electrodiagnostics, CT myelography, computed tomography, MR myelography, magnetic resonance

18.1 Epidemiology and Risk Factors Neonatal brachial plexus palsy (NBPP) is injury to the brachial plexus that occurs before, during, or after labor and parturition. Reported incidence varies between approxi-

mately 0.5 and 5 per 1,000 live births.1,2,3,4,5,6,7,8 The most common pattern of injury is injury to the upper trunk. This occurs due to stretch to the upper trunk as a result of a forceful increase in the angle between the shoulder and the head before, during, or after labor and parturition (▶ Fig. 18.1). This results in loss of shoulder abduction, external rotation, and elbow flexion. Overall, the clinical presentation is highly variable and depends on the portion of the brachial plexus that is injured. Fortunately for patients who sustain a brachial plexus injury, most spontaneously recover. Though there is variance in how persistence is defined, most studies report a persistent deficit in 20 to 30% of patients.9,10 Identification of risk factors for the incidence of NBPP falls within the realm of obstetricians as identification of such risk factors may help in the prevention of NBPP. A variety of risk factors for the incidence of NBPP have been previously identified. Factors previously found to increase the incidence of NBPP include advanced maternal age, obesity, diabetes mellitus, abnormalities of the second stage of labor, vacuum- or forceps-assisted delivery, and shoulder dystocia.11,12,13,14,15 Conversely, multiple births and cesarean delivery have both been found to be protective against NBPP.16 It remains to be seen how to optimally incorporate these identified risk factors into a management strategy that reduces the overall incidence of NBPP. In contrast, the identification of risk factors for the persistence of NBPP falls within the realm of treating

Fig. 18.1 As seen in this example of a vacuum-assisted delivery with shoulder dystocia, a forceful increase in the angle between the shoulder and the head before, during, or after labor and parturition often results in injury to the upper trunk of the brachial plexus.

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Neonatal Brachial Plexus Palsy: Clinical Presentation and Assessment physicians such as nerve surgeons and physiatrists as identification of such risk factors may allow for the development of prediction algorithms that help optimize care. We have recently identified several factors associated with persistence of NBPP. Further studies are needed to fully elucidate the list of factors associated with persistence. We found that cephalic presentation, induction or augmentation of labor, birth weight > 9 lb, and the presence of Horner’s syndrome on clinical examination all increased the likelihood of persistence at 1 year. To the contrary, cesarean delivery and Narakas grade I/II injury both were associated with a decreased likelihood of persistence. Given the incidence rate and not insignificant rate of persistence, physiatrists and nerve surgeons are likely to have these patients referred to them. They are then left with determining how to evaluate these patients in order to best determine appropriate management. Evaluation of these patients involves a clinical assessment consisting of a thorough history and physical examination, electrodiagnostic studies, imaging studies, and finally an overall assessment to determine the need for operative intervention. In this chapter, we discuss the clinical presentation and evaluation of patients with NBPP.

18.2 Clinical Assessment Patients present with a combination of motor, sensory, and proprioceptive deficits in addition to possible extraplexal symptoms such as hemidiaphragm paralysis or Horner’s syndrome. The specific pattern of deficits is determined by the portion of the brachial plexus (and possibly extraplexal segments) that is injured. Clinical assessment including a thorough history and physical examination is paramount and remains the mainstay of evaluation. Imaging studies and electrodiagnostics should not be thought of as the primary means of diagnosis and evaluation but rather as an extension of the physical examination. The history and physical examination should serve five primary purposes: (1) to document the presence or absence of risk factors for persistence; (2) to localize the injured plexal and extraplexal segments; (3) to determine available plexal or extraplexal donors if nerve transfers are being considered; (4) to document evidence of spontaneous recovery, or lack thereof, on sequential examinations; and (5) to determine the need for surgical intervention. Clinical assessment begins with taking a thorough history. The history should focus on both the neonatal history and maternal history. As risk factors for persistence continue to be identified and potentially incorporated into prediction algorithms, this information will become increasingly important in optimizing management. Obstetric records should be obtained and available to the treating physiatrist or nerve surgeon. As this is an evolving area and the specific factors that are important for

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management continue to be elucidated, suffice it to say that a thorough maternal and neonatal history should be obtained. The most important component of evaluation is the physical examination. A detailed examination of the neonate is difficult secondary to the fact that the typical detailed neurologic examination requires voluntary participation that is not possible with a neonate. Thus, alternative approaches must be employed to achieve the same evaluation. The most common tactics utilize close observation during play or in response to irritating stimuli. The neonate should be observed for activation of specific muscle groups during play or in response to irritating stimuli, and the degree of active range of motion for each muscle group should be noted. In addition to observation for muscle activation, additional physical examination features that should be noted include asymmetric chest expansion that may be consistent with a phrenic nerve palsy, miosis and ptosis that may be consistent with a Horner’s syndrome, and the presence of any classic postures such as the waiter’s tip posture that may help localize the injured segments of the brachial plexus. It is important not to be binary in the evaluation of specific muscles (i.e., activates vs. does not activate) but rather to be as precise in grading the activation as possible. This may become highly important in both determining the need for surgery and also when considering whether a specific nerve is a viable donor for nerve transfer. Weakness, though activation is present, may make a given nerve a less attractive donor candidate. In addition to active range of motion, passive range of motion should be examined. In general, joint subluxations and contractures take several months to develop. The presence of early joint subluxation or contractures may indicate that an additional musculoskeletal condition is present.1,17 Some clinical exam findings indicate a lack of hope for spontaneous recovery including the presence of a flail arm suggestive of a panplexus injury and the presence of a Horner’s syndrome suggestive of a preganglionic injury. In circumstances aside from these, it is important that the physical examination is documented on multiple occasions and compared over time to determine progressive spontaneous recovery. A single physical examination is significantly less useful than multiple examinations over time. A variety of assessment scales have been developed specifically for evaluation of NBPP. While these scales are often applied preoperatively, they are more commonly applied postoperatively in order to assess recovery. Probably the most commonly applied motor grading scale is the Medical Research Council (MRC) grading scale. However, the application of this scale requires voluntary participation of the patient making it not applicable for evaluation of neonates. To address this limitation, the Active Movement Scale (AMS) was proposed (▶ Table 18.1).18 This scale focuses on range of motion

Neonatal Brachial Plexus Palsy: Clinical Presentation and Assessment Table 18.1 The Active Movement Scale (AMS) Finding

Muscle grade

Gravity eliminated No contraction

0

Contraction but no motion

1

Motion ≤ 1/2 range

2

Motion > 1/2 range

3

Full motion

4

Against gravity Motion ≤ 1/2 range

5

Motion > 1/2 range

6

Full motion

7

of motor function is important, there may be other equally important factors that are ignored, only evaluating motor function. Examples of other factors that may be important to incorporate into future evaluation metrics include sensation, arm preference, proprioception, functional use of the extremity, cognitive development, pain, quality of life, and language development.21 Going forward, it will be important to determine the optimal methods and domains of evaluation aside from motor function.

18.3 Imaging

with gravity and with gravity eliminated with the score ranging 0 (no contraction with gravity eliminated) to 7 (full range of motion against gravity). It has been found to have high interrated reliability independent of the experience of the rater. Using the AMS, each movement is given an individual score. Mallet also developed a grading scale but rather than focusing on individual movements, this scale focuses on function of the entire limb (▶ Table 18.2).19 Components of the scale include active shoulder abduction, external rotation of the shoulder, hand to head, hand to back, and hand to mouth. This scale has several significant drawbacks, however. First, it has the same limitation as the MRC grading scale in that it requires active participation of the patient and thus can only be used after approximately 3 years of age. Second, the interrater reliability has been found to be variable between the assessed movements.20 Finally, this scale focuses on shoulder and elbow movements and ignores hand function. While this is a limitation, this scale is appropriate for upper plexus injuries, which is the most common pattern. Several other assessment scales have been developed for assessment of a specific movement or joint. These scales include the Gilbert scale for shoulder function, Gilbert and Raimondi scale for elbow function, and the Raimondi scale for hand function. Most evaluation metrics that pertain to NBPP focus on evaluation of motor function over time. While evaluation

Table 18.2 Mallet shoulder score Grade 2

Grade 3

Grade 4

Active abduction

< 30 degrees

30–90 degrees

> 90 degrees

External rotation

0 degrees

1–20 degrees

> 20 degrees

Hand to head

Impossible

Difficult

Easy

Hand to back

Impossible

S1

T12

Hand to mouth

Impossible

Difficult

Easy

Imaging studies can be a valuable addition to the evaluation of the NBPP patient but should be thought of as an extension of the neurologic examination and certainly do not replace it. No consensus currently exists regarding the appropriate diagnostic imaging studies to obtain. Options include computed tomography (CT) myelography, magnetic resonance (MR) myelography, and ultrasound. MR neurography is becoming increasingly available as well, though its role is even more unclear at this time. Imaging is typically employed looking for evidence of nerve root avulsion or nerve rupture that would suggest an irreversible injury. Historically, the most commonly utilized imaging study was CT myelography. CT myelography is most useful in the detection of nerve root avulsions as opposed to nerve ruptures. We have shown that the sensitivity of CT myelography for nerve ruptures is only 58.3% as opposed to 72.2% for nerve root avulsions.22 CT myelograms can be difficult to interpret and there is even debate as to the diagnostic criteria that should be used in order to diagnose an avulsion. The two most commonly used diagnostic criteria are the presence of a pseudomeningocele versus the presence of a pseudomeningocele with absent nerve rootlets. There are mixed data regarding which of these diagnostic criteria is better. Tse et al compared these two criteria for diagnosis and found a sensitivity of 73 and 68% for pseudomeningocele versus pseudomeningocele with absent rootlets, respectively. Regardless of the criteria, this would suggest that CT myelography is not highly sensitive for detection of nerve root avulsions. However, CT myelography is highly specific. Regardless of the diagnostic criteria, Tse et al reported a specificity of 96%.23 Chow and colleagues had previously reported a significant improvement in specificity using pseudomeningocele with absent rootlets (98%) versus pseudomeningocele alone (85%).24 Tse and colleagues may not have found a similar increase due to the high proportion of Narakas grade III/IV injuries in their patient cohort. By including more patients with C8 and T1 injuries, they were more likely to have a high percentage of patients with avulsion injury. In their study, 18 of 19 pseudomeningoceles also had absent rootlets.23 If their study population had been more heterogeneous with regard to injury level and severity, they may have

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Neonatal Brachial Plexus Palsy: Clinical Presentation and Assessment observed a similar increase in specificity using pseudomeningocele with absent rootlets as the diagnostic criteria. Nevertheless, there is no consensus as to which diagnostic criteria should be used. It is clear, however, that CT myelography is poor at detecting nerve ruptures and only moderately sensitive but highly specific for the detection of nerve root avulsions. Other disadvantages of CT myelography include the invasive nature of the procedure, the risks associated with instillation of intrathecal contrast, and exposure to ionizing radiation. An alternative to CT myelography is MR myelography. MR myelography compares favorably to CT myelography with similar sensitivity and specificity, 68 and 96%, respectively.23 MR myelography offers significant advantages over CT myelography including the noninvasive nature of the procedure, lack of intrathecal contrast administration, and lack of exposure to ionizing radiation. However, some of the difficulties plague MR myelography. There remains a need for consensus criteria for diagnosing a nerve root avulsion. In addition, similar to CT myelography, MR myelography does not image the distal nerves, making it an imaging modality most appropriate for examining for avulsions rather than nerve ruptures. Given the significant advantages of MR myelography combined with a comparable sensitivity and specificity, we now utilize MR myelography instead of CT myelography in the evaluation of patients with NBPP. Neither CT nor MR myelography images the extraforaminal nerve roots well. For visualization of this component of the brachial plexus, we utilize ultrasound. Ultrasound is most useful in the evaluation of the upper and middle trunks. It is less reliable in the evaluation of the lower trunk. We demonstrated that the sensitivity for detection of a neuroma was 84% for the upper and middle trunks compared to only 68% for the lower trunk. Ultrasound can also offer information about the proximal extent of the injury. Ultrasound can be used to evaluate the serratus anterior and rhomboid muscles for evidence of atrophy. Atrophy in these muscles suggests a proximal injury, unlikely to be suitable for nerve graft repair. When we find atrophy in these muscles, we proceed with nerve transfer.25 Ultrasound is currently our diagnostic modality of choice for evaluation of the extraforaminal components but as MR neurography continues to improve, it remains possible that it will replace ultrasound. MR neurography is improving and has been tested for its ability to evaluate the brachial plexus with some success.26,27,28 However, to this point, it has not been evaluated in NBPP patients and thus its utility remains unclear.

18.4 Electrodiagnostics The last method of evaluation of NBPP patients is electrodiagnostic studies. In adults, electrodiagnostics are a mainstay of evaluation and supplement the physical examination in localizing the injured segments of the

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brachial plexus. Electrodiagnostics, however, are plagued with difficulties in neonates. Electromyography can be difficult to interpret in neonates and often the findings are discordant with clinical findings. For example, one would expect to find a loss of motor unit potentials and the presence of denervation activity in the setting of an upper trunk injury with a paralyzed biceps. However, it is not uncommon to find both the presence of motor unit potentials and absence of denervation activity in the setting of a paralyzed biceps. Five reasons for these discordant findings have been suggested by Malessy and colleagues: (1) inadequacy of the clinical examination, (2) overestimation of the number of motor unit potentials, (3) luxury innervation, (4) central motor disorders, and (5) abnormal nerve branching.29 Despite these difficulties, we do still routinely obtain these studies as we do believe they provide useful information. While an experienced electromyographer is useful in interpreting these studies, we have found that the interrater reliability is extremely high.30 We use electrodiagnostic studies in a complementary way to CT/MR myelography. Electrodiagnostic studies do a poor job of detecting nerve root avulsions. In our previous study, we found a sensitivity of only 27.8%. Contrary to CT/MR myelography, electrodiagnostic studies are most useful in detecting nerve ruptures. The sensitivity of electrodiagnostics for nerve ruptures confirmed intraoperatively was 92.8%.22 Electrodiagnostics can also be useful when used in a sequential fashion to detect spontaneous recovery. Oftentimes, electrodiagnostic evidence of recovery precedes evidence by physical examination. Despite this, when making decisions about operative intervention, we always rely on the physical examination evidence over the electrodiagnostic studies.

18.5 Surgical Assessment Once the assessment is complete, we are left with the task of determining for whom to recommend surgical intervention. There are currently no consensus guidelines upon which to base this decision. Historically, most base the decision to operate on the degree of spontaneous recovery by 3 months of age. Gilbert et al previously demonstrated that when biceps function failed to recover spontaneously by 3 months, the motor outcomes at 5 years of age were poor.31,32 For this reason, most use the 3-month time point as the crucial time point for evaluation. Michelow and colleagues later added data to potentially support a more delayed decision when they showed that utilizing absent biceps function at 3 months to predict long-term biceps recovery, the prediction is incorrect 12% of the time. By incorporating assessment of multiple movements at 3 months into an overall score, the percentage of incorrect predictions can be reduced to 5%.33 The main issue is that some patients will go on to develop biceps function between 3 and 6 months though

Neonatal Brachial Plexus Palsy: Clinical Presentation and Assessment

University of Michigan NBPP Treatment Pathway

0 months (New patient) History and physical Physiotherapy

1 month History and physical Physiotherapy Electrodiagnostics

YES biceps function YES biceps MUAPs

3 months

*NO biceps function NO biceps MUAPs

Physiotherapy egrity US for shoulder integrity

6 months

Clinical examination MRI/US Physiotherapy

Yes Hand-to-mouth

6 months

NO Hand-to-mouth

Nerve surgery *For flail arm, surgery at 3 months

Continue physiotherapy Expectant management

Fig. 18.2 This is the treatment pathway utilized at the University of Michigan when determining management of patients presenting with neonatal brachial plexus palsy (NBPP). MRI, magnetic resonance imaging; MUAP, motor unit action potential; US, ultrasound.

the significance of this recovery is uncertain. There are data to argue that recovery during this time period is not clinically significant as patients developing biceps function after 5 months of age have been shown to have improved outcomes with operative versus nonoperative management.34,35 Based on all of these data, assessment at either the 3- or 6-month time point has become the norm. What is being balanced in this decision is the improved outcomes that occur by operating earlier versus the possibility of unnecessary surgery if some patients will go on to recover at later time points obviating the need for surgery. Some very specific tests have been proposed to be administered at these time points to determine the need for operative management, particularly for upper trunk injuries. Two such examples are the towel test and the cookie test. In the towel test, a towel is placed over the infant’s face. The infant is then observed for the ability to remove the towel with the affected arm.36 In the cookie test, the infant is given a small cookie and observed for the ability to get the cookie into his/her mouth with the

humerus held at the infant’s side.37 The University of Michigan NBPP treatment pathway is shown in ▶ Fig. 18.2. We incorporate imaging studies, electrodiagnostics, and the physical examination including the principle of the cookie test in order to make an assessment on the need for surgery by 6 months of age.

References [1] Hoeksma AF, Ter Steeg AM, Dijkstra P, Nelissen RG, Beelen A, de Jong BA. Shoulder contracture and osseous deformity in obstetrical brachial plexus injuries. J Bone Joint Surg Am. 2003; 85-A(2): 316–322 [2] Hoeksma AF, ter Steeg AM, Nelissen RG, van Ouwerkerk WJ, Lankhorst GJ, de Jong BA. Neurological recovery in obstetric brachial plexus injuries: an historical cohort study. Dev Med Child Neurol. 2004; 46(2):76–83 [3] van der Sluijs JA, van Ouwerkerk WJ, de Gast A, Wuisman PI, Nollet F, Manoliu RA. Deformities of the shoulder in infants younger than 12 months with an obstetric lesion of the brachial plexus. J Bone Joint Surg Br. 2001; 83(4):551–555 [4] Moukoko D, Ezaki M, Wilkes D, Carter P. Posterior shoulder dislocation in infants with neonatal brachial plexus palsy. J Bone Joint Surg Am. 2004; 86-A(4):787–793

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Neonatal Brachial Plexus Palsy: Clinical Presentation and Assessment [5] Saifuddin A, Heffernan G, Birch R. Ultrasound diagnosis of shoulder congruity in chronic obstetric brachial plexus palsy. J Bone Joint Surg Br. 2002; 84(1):100–103 [6] Kon DS, Darakjian AB, Pearl ML, Kosco AE. Glenohumeral deformity in children with internal rotation contractures secondary to brachial plexus birth palsy: intraoperative arthrographic classification. Radiology. 2004; 231(3):791–795 [7] Terzis JK, Vekris MD, Okajima S, Soucacos PN. Shoulder deformities in obstetric brachial plexus paralysis: a computed tomography study. J Pediatr Orthop. 2003; 23(2):254–260 [8] Waters PM, Smith GR, Jaramillo D. Glenohumeral deformity secondary to brachial plexus birth palsy. J Bone Joint Surg Am. 1998; 80(5): 668–677 [9] Malessy MJ, Pondaag W. Nerve surgery for neonatal brachial plexus palsy. J Pediatr Rehabil Med. 2011; 4(2):141–148 [10] Pondaag W, Malessy MJ, van Dijk JG, Thomeer RT. Natural history of obstetric brachial plexus palsy: a systematic review. Dev Med Child Neurol. 2004; 46(2):138–144 [11] Hudić I, Fatusić Z, Sinanović O, Skokić F. Etiological risk factors for brachial plexus palsy. J Matern Fetal Neonatal Med. 2006; 19(10): 655–661 [12] Okby R, Sheiner E. Risk factors for neonatal brachial plexus paralysis. Arch Gynecol Obstet. 2012; 286(2):333–336 [13] Ouzounian JG. Risk factors for neonatal brachial plexus palsy. Semin Perinatol. 2014; 38(4):219–221 [14] Weizsaecker K, Deaver JE, Cohen WR. Labour characteristics and neonatal Erb’s palsy. BJOG. 2007; 114(8):1003–1009 [15] Zuarez-Easton S, Zafran N, Garmi G, Nachum Z, Salim R. Are there modifiable risk factors that may predict the occurrence of brachial plexus injury? J Perinatol. 2015; 35(5):349–352 [16] Foad SL, Mehlman CT, Ying J. The epidemiology of neonatal brachial plexus palsy in the United States. J Bone Joint Surg Am. 2008; 90(6): 1258–1264 [17] Hoeksma AF, Wolf H, Oei SL. Obstetrical brachial plexus injuries: incidence, natural course and shoulder contracture. Clin Rehabil. 2000; 14(5):523–526 [18] Curtis C, Stephens D, Clarke HM, Andrews D. The active movement scale: an evaluative tool for infants with obstetrical brachial plexus palsy. J Hand Surg Am. 2002; 27(3):470–478 [19] Mallet J. [Obstetrical paralysis of the brachial plexus. II. Therapeutics. Treatment of sequelae. Priority for the treatment of the shoulder. Method for the expression of results]. Rev Chir Orthop Repar Appar Mot. 1972; 58:1, 166–168 [20] van der Sluijs JA, van Doorn-Loogman MH, Ritt MJ, Wuisman PI. Interobserver reliability of the Mallet score. J Pediatr Orthop B. 2006; 15(5):324–327 [21] Dy CJ, Garg R, Lee SK, Tow P, Mancuso CA, Wolfe SW. A systematic review of outcomes reporting for brachial plexus reconstruction. J Hand Surg Am. 2015; 40(2):308–313

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[22] Vanderhave KL, Bovid K, Alpert H, et al. Utility of electrodiagnostic testing and computed tomography myelography in the preoperative evaluation of neonatal brachial plexus palsy. J Neurosurg Pediatr. 2012; 9(3):283–289 [23] Tse R, Nixon JN, Iyer RS, Kuhlman-Wood KA, Ishak GE. The diagnostic value of CT myelography, MR myelography, and both in neonatal brachial plexus palsy. AJNR Am J Neuroradiol. 2014; 35(7):1425–1432 [24] Chow BC, Blaser S, Clarke HM. Predictive value of computed tomographic myelography in obstetrical brachial plexus palsy. Plast Reconstr Surg. 2000; 106(5):971–977, discussion 978–979 [25] Somashekar DK, Di Pietro MA, Joseph JR, Yang LJ, Parmar HA. Utility of ultrasound in noninvasive preoperative workup of neonatal brachial plexus palsy. Pediatr Radiol. 2016; 46(5):695–703 [26] Oudeman J, Coolen BF, Mazzoli V, et al. Diffusion-prepared neurography of the brachial plexus with a large field-of-view at 3 T. J Magn Reson Imaging. 2016; 43(3):644–654 [27] Andreou A, Sohaib A, Collins DJ, et al. Diffusion-weighted MR neurography for the assessment of brachial plexopathy in oncological practice. Cancer Imaging. 2015; 15:6 [28] Upadhyaya V, Upadhyaya DN, Kumar A, Gujral RB. MR neurography in traumatic brachial plexopathy. Eur J Radiol. 2015; 84(5):927–932 [29] Malessy MJ, Pondaag W, van Dijk JG. Electromyography, nerve action potential, and compound motor action potentials in obstetric brachial plexus lesions: validation in the absence of a “gold standard”. Neurosurgery. 2009; 65(4) Suppl:A153–A159 [30] Spires MC, Brown SM, Chang KW, Leonard JA, Yang LJ. Interrater reliability of electrodiagnosis in neonatal brachial plexopathy. Muscle Nerve. 2017; 55(1):69–73 [31] Gilbert A, Brockman R, Carlioz H. Surgical treatment of brachial plexus birth palsy. Clin Orthop Relat Res. 1991(264):39–47 [32] Gilbert A, Pivato G, Kheiralla T. Long-term results of primary repair of brachial plexus lesions in children. Microsurgery. 2006; 26(4): 334–342 [33] Michelow BJ, Clarke HM, Curtis CG, Zuker RM, Seifu Y, Andrews DF. The natural history of obstetrical brachial plexus palsy. Plast Reconstr Surg. 1994; 93(4):675–680, discussion 681 [34] Waters PM. Obstetric Brachial Plexus Injuries: Evaluation and Management. J Am Acad Orthop Surg. 1997; 5(4):205–214 [35] Waters PM. Comparison of the natural history, the outcome of microsurgical repair, and the outcome of operative reconstruction in brachial plexus birth palsy. J Bone Joint Surg Am. 1999; 81(5):649–659 [36] Bertelli JA, Ghizoni MF. The towel test: a useful technique for the clinical and electromyographic evaluation of obstetric brachial plexus palsy. J Hand Surg [Br]. 2004; 29(2):155–158 [37] Borschel GH, Clarke HM. Obstetrical brachial plexus palsy. Plast Reconstr Surg. 2009; 124(1) Suppl:144e–155e

The Neonatal Brachial Plexus Lesion: Surgical Strategies

19 The Neonatal Brachial Plexus Lesion: Surgical Strategies W. Pondaag and M.J.A. Malessy Abstract Good results can be obtained with nerve reconstructive surgery of severe neonatal brachial plexus lesions (NBPL). Criteria for surgery differ among surgical teams, none of which have a strong scientific basis. The exception is impaired hand function, which is generally considered an absolute indication for surgery. The applied nerve repair techniques consist of grafting after neuroma resection and transfer. A supraclavicular exposure will suffice for a proper reconstruction in the majority of the infants. Donor nerves for transfers are additionally exposed if indicated. The severity of the NBPL lesion of each clinically involved spinal nerve is assessed on the basis of magnetic resonance imaging myelography, intraoperative inspection of the status of nerve continuity, neuroma formation, and selective electrical stimulation. The primary goal of nerve repair is restoration of hand grasp function. The second priority is restoration of elbow flexion, the third is the restoration of shoulder movements, and the fourth is extension of the elbow, wrist, and fingers. The surgical repair strategy depends upon the number of available viable proximal spinal nerve stumps for grafting, the cross-sectional area of the stumps, and the availability of donor nerves for neurotization. Delay of repair, the length of grafts, the amount of scarring, the viability of the proximal stump, and the complexity of functions to be restored determine functional recovery after reconstruction. Nerve repair in selected cases of NBPL can significantly improve the functional level of the arm to a level that would probably not have been reached through spontaneous regeneration and conservative treatment. Keywords: neonatal brachial plexus lesion, nerve repair surgery, grafting, transfer

19.1 Introduction The neonatal brachial plexus lesion (NBPL) is caused by traction during delivery.1,2 Incidence varies from 1.6 to 2.9 per 1,000 births in prospective studies.3,4 Spontaneous recovery may occur depending on the severity of the traction injury. Although neurapraxia and axonotmesis eventually see complete recovery, neurotmesis and root avulsion result in permanent loss of arm function. Fortunately, most children show good spontaneous recovery. The natural history of NBPL, however, has never been studied systematically. The percentage of children with residual deficits is estimated at 20 to 30%.5 The upper part of the brachial plexus, which includes spinal nerves C5,

C6, and the superior trunk, is affected in the vast majority of infants. Upper plexus lesions present with extended arm in internal rotation and adduction without elbow flexion and supination. This is caused by a paralysis of the infraspinatus and supraspinatus muscles in combination with the loss of deltoid and biceps muscle functions. Hand function is additionally impaired in approximately 15% of patients when spinal nerves C8 and T1 are involved.3,6,7 The extent of neural damage after NBPL can be assessed only by evaluation of recovery in the course of time, because nerve lesions of different severity initially present with the same clinical features. At present, most authors advise surgical exploration at a preset age if spontaneous recovery is considered to be insufficient by that time.8,9,10,11,12 Commonly applied nerve repair techniques consist of nerve grafting after neuroma resection and nerve transfer in the case of root avulsion.9,12,13,14,15,16

19.2 Selection for Surgery In the Leiden Nerve Center, the Netherlands, surgery for NBPL is rarely performed before 3 months of age, but it is almost always done before the age of 7 months. In selecting infants for surgery, all cases of neurotmesis or avulsion are identified using the criteria discussed next. Infants are selected for surgery when external shoulder rotation and elbow flexion with supination remain paralytic after a 3- to 4-month period to await spontaneous recovery.17 Impaired hand function is an absolute indication for nerve surgery as soon as the infant turns 3 months old.18 If there is doubt about the quality of shoulder and elbow joint movements, surgical exploration is performed in the hope that errors would consist of not finding neurotmesis or avulsion during surgery rather than letting such lesions go without surgical treatment. Preoperative ancillary investigations in all patients consist of ultrasound of diaphragm excursions to assess phrenic nerve function and MRI myelography under general anesthesia to detect root avulsions.19,20

19.3 Surgical Exposure 19.3.1 Supraclavicular Exposure The surgical approach to NBPL inevitably begins in the supraclavicular region for exploration of the proximal brachial plexus. In the vast majority of patients, the supraclavicular exposure alone will suffice for a proper nerve repair and reconstruction. Surgery is performed under general anesthesia without the use of muscle

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The Neonatal Brachial Plexus Lesion: Surgical Strategies blocking agents. The supraclavicular brachial plexus is exposed in the posterior triangle of the neck. Appropriate positioning of the patient is extremely important to facilitate the operation: the patient is supine, and the head is turned toward the opposite direction with the neck in gentle extension. The head is supported by a silicone ring, where the contralateral ear is placed in the recess of the ring; the nonaffected shoulder is positioned caudally to avoid compressing the cervical vascular structures. Neck extension is encouraged by placing a folded cotton cloth at the level of the lower cervical spine and upper thoracic spine in order to support the plane of the brachial plexus parallel to the floor; avoid narrowing the costoclavicular space with an excessively thick folded cloth. The affected arm lies completely in the sterile field and is supported as close as possible to the edge of the operating table in 0-degree abduction during exploration and in 45 degrees of abduction during nerve repair. For easier access to the dorsal aspect of the legs for the harvesting of sural nerve grafts, the length of the operating table is reduced as much as possible. The lower part of the face, neck, shoulder, chest, and legs are prepared for surgery. A linear incision just lateral to the sternocleidomastoid muscle is made approximately 0.5 cm (in case the lower plexus is affected as well) to 1.5 cm (for upper plexus lesions) above and parallel to the clavicle. The platysma is incised perpendicular to its fibers, and a generous subplatysmal dissection is performed. The external jugular vein is often encountered and must be retracted or ligated when necessary. The position of the spinal accessory nerve is relatively superficial as it courses from the posterior aspect of the sternocleidomastoid muscle (two-thirds of the distance from the sternum to the mastoid) toward its insertion in the trapezius. Identification of the spinal accessory nerve along its course is crucial to preserve trapezius function or to use its terminal branches as donor for nerve transfer. An intraoperative nerve stimulator can be used to identify and confirm the course of the spinal accessory nerve. The lateral margin of the sternocleidomastoid muscle is identified, with its sternal and clavicular heads. The lateral aspect of the clavicular head is released to facilitate exposure. The supraclavicular nerves (sensory nerves branches of the ansa cervicalis, C2–C4) are identified along their superficial cranial–caudal course. These nerves are likewise preserved for anatomical landmarks, or used as donors for sensible extraplexal to intraplexal transfers in total plexus lesions21 and, occasionally, for potential donors for nerve graft material. The supraclavicular nerves are followed proximally until the C4 spinal nerve root is identified. The cervical fascia/scalene fat pad is released parallel to the sternocleidomastoid starting at the level of C4 in a cranial to caudal direction; at the retroclavicular level, the dissection of the fat pad turns 90 degrees lateral and parallel to the clavicle. The resulting cervical fascia/scalene fat pad can be mobilized for the

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exploration, then replaced at closure to cover the nerve grafts and nerve coaptation sites after the reconstruction. The cervical fascia/scalene fat pad should be preserved as much as possible, that is, coagulation should be avoided, as it may contribute to the revascularization of nerve grafts and may provide the optimal environment for the nerve elements. The thoracic duct should be preserved or ligated to avoid chyle leakage if the fat pad is released to expose the left supraclavicular brachial plexus. The transverse cervical artery and vein running parallel to the clavicle ventral to the BP elements are retracted or ligated. The omohyoid muscle is identified between the superficial and the deep cervical fascia along its course toward the suprascapular notch, and it can be tagged and retracted. Note that preserving this muscle to identify the suprascapular notch can facilitate the identification of the suprascapular nerve, especially in patients whose anatomy is distorted by trauma. After the C4 spinal nerve root has been identified, its branch to the phrenic nerve is followed. The phrenic nerve is dissected along its length on the ventral aspect of the anterior scalene muscle. One should carefully mobilize the phrenic nerve to preserve the function of the diaphragm, which is especially important to infant respiration. Four pointers to facilitate the safe identification of the phrenic nerve follow. (1) The phrenic nerve cannot always be macroscopically seen directly because it may be covered by the deep transverse cervical fascia; the transparency of this fascia varies depending on its thickness and any scar present. Nerve stimulation to identify the course of the phrenic nerve from medial to lateral over the surface of the anterior scalene muscle is extremely helpful and is, in our opinion, indispensable. (2) the phrenic nerve origin can be located at the caudal aspect of C4; the phrenic nerve usually originates from C3 and C4; often there is a connecting branch from C4–C5.22 Traction to the brachial plexus may result in a concurrent traction injury of the phrenic nerve via this connection. (3) The artery and vein that are adjacent to the phrenic nerve should not be identified erroneously as the nerve. (4) The authors have occasionally encountered a separate auxiliary phrenic nerve at higher cervical levels. The phrenic nerve courses lateral to medial toward the diaphragm, while the contents of the plexus and the surrounding nerves course from medial to lateral. As the phrenic nerve approaches the lateral edge of the anterior scalene, the C5 spinal nerve root emerges; this is a reliable location for the identification of the C5 nerve root. The phrenic nerve is completely neurolyzed in its trajectory ventral to the anterior scalene muscle to allow gentle medial retraction without significant traction. In some patients, the phrenic nerve may be adherent to the neuroma of C5. Some neuroma scar tissue should deliberately left on the phrenic nerve instead of dissecting flush on the phrenic nerve and remove all the C5 neuroma in order to maximize preservation of diaphragmatic

The Neonatal Brachial Plexus Lesion: Surgical Strategies function. Resection or partial resection of the anterior scalene muscle is always performed to allow for optimal exposure of the proximal, intraforaminal part of the spinal nerve roots. A pseudomeningocele that extends extraforaminally may be encountered during such proximal exposure. Extraforaminal expansion of cells should be preoperatively identified on MRI. Following the C5 root distally leads to the upper trunk, and following the upper trunk proximally will lead to the C6 spinal nerve root. The C6 spinal nerve root is located caudal and dorsal to the C5 spinal nerve root. The anterior tubercle of C6 can be very prominent (Chassaignac’s tubercle). The C7, C8, and T1 spinal nerve roots are sequentially more caudal and dorsal. A transverse cervical artery and vein cross the C7 spinal nerve root and can be ligated. Following the C7 spinal nerve distally will reveal the middle trunk. The C8 and T1 spinal nerves combine quickly to form the lower trunk, which is adjacent to the subclavian vessels. The roots of the lower trunk surround the first rib; therefore, care should be taken to avoid injury to the pleura. Special attention should be given to the vertebral artery, as in proximal dissection it runs unprotected at the level of the roots C8/T1 before it enters the vertebral canal in the lateral mass of C7.23 The next step is to identify the suprascapular nerve and the divisions of the upper trunk. The upper trunk can be seen to “split” into three separate structures—from lateral to medial, the suprascapular nerve, the posterior division, and the anterior division.24,25 The suprascapular nerve originates from the lateral aspect of the upper trunk and normally follows a slightly oblique cranial– caudal course toward the suprascapular notch (the omohyoid also attaches at the suprascapular notch). Caudal displacement of the superior trunk will alter the trajectory of the suprascapular nerve to a more horizontal direction. It may be necessary to extend the surgical exposure to the retroclavicular region to improve exposure of the distal stumps. To facilitate adequate exposure, the retroclavicular space can be easily expanded by suspension of the clavicle by retraction using a Penrose drain or gauze passed immediately underneath the clavicle (▶ Fig. 19.1).26 Suspension of the clavicle additionally facilitates the proximal dissection of the lower roots when indicated. Should a more extensive exposure be necessary, a clavicle osteotomy may be considered, although the authors have never done so and managed well without so far.

19.3.2 Infraclavicular Exposure Infraclavicular extension of the lesion in NBPL is quite rare. It may be indicated to explore donor nerves for transfers originating from the infraclavicular brachial plexus. The infraclavicular brachial plexus is exposed through the deltoideopectoral groove. A linear incision is

Fig. 19.1 To facilitate adequate exposure, the retroclavicular space can be easily expanded by suspension of the clavicle by retraction using a Penrose drain or gauze passed immediately underneath the clavicle.26 Suspension of the clavicle additionally facilitates the proximal dissection of the lower roots when indicated.

made from the clavicle toward the axilla, overlying the deltoideopectoral groove. The cephalic vein is visualized within the groove, and it can be retracted laterally or ligated. If needed, a portion of the pectoralis major muscle can be detached from the inferior surface of the clavicle and from the humerus. The cuff of tendon from the humerus is tagged to facilitate later repair. The pectoralis major muscle is retracted caudally and the deltoid laterally, revealing the underlying coracoid process with its muscle attachments. Blunt dissection will separate the pectoralis minor from the coracobrachialis and the surrounding tissues. Once the pectoralis minor tendon has been isolated, it may be divided with later reapproximation, but usually muscle retraction will suffice. The infraclavicular brachial plexus elements lie immediately dorsal and caudal to the pectoralis minor. When the arm is at or lower than the plane of the shoulder, the most superficial structures are the lateral cord with its lateral branch leading to the musculocutaneous nerve and its medial branch leading to the median nerve. The medial cord may be identified medial and slightly posterior to the axillary artery, and the lateral branch of the medial cord will lead to the median nerve (the medial branch continues down the arm as the ulnar nerve). Exposure of the posterior cord and its axillary and radial nerve branches is best accomplished in the region lateral and posterior to the axillary artery, in contrast to the medial posterior course, which is frequently and erroneously depicted in schematic anatomical drawings.27 The axillary nerve branches from the posterior cord runs through the quadrilateral space above the latissimus dorsi and teres major tendons; this nerve can be identified more easily by externally rotating the humerus.

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The Neonatal Brachial Plexus Lesion: Surgical Strategies

19.3.3 Exposure and Technique for Nerve Transfers If nerve transfers are indicated,28 the donor nerves must be exposed. It is imperative that donor nerves have normal function; direct electrical stimulation intraoperatively can assess their function and aid in their identification. The spinal accessory nerve (SAN) is a commonly employed donor nerve for neurotization to the suprascapular nerve (SSN) for restoration of shoulder function. The SAN can be located as it approaches and enters the anterior surface of the trapezius muscle as described earlier. The nerve gives off a proximal branch to the superior part of the trapezius muscle, which must be kept intact. The SAN is mobilized, then transected as distally as possibly. The proximal stump is then passed through the cervical fascia/scalene fat pad to allow for the direct coaptation with the SSN. The caliber of the SAN usually corresponds well to that of the SSN. Alternatively, a dorsal approach can be applied to perform a SAN to SSN transfer.29 Theoretically, this transfer carries the advantage that the nerve coaptation is performed closer to the target muscle, leading to shorter recovery time. A proper comparison between both techniques has not yet been performed. Another commonly used donor nerve is the medial pectoral nerve (MPN)21; it is used for nerve transfer to the musculocutaneous nerve (MCN) for restoration of elbow flexion. The MCN can be identified in its course dorsal to the pectoralis major and minor muscles. Generally, the MPNs can be reached by retracting the pectoralis major muscle cranially through an incision in the lower part of the deltopectoral groove, which further extends distally over the proximal medial bicipital groove. The MPN originates from the medial cord, and its function remains intact in C5–C6 or C5–C6–C7 lesions.30 Intraoperative nerve stimulation is indispensable step for the identification of the MPNs since small vessels simulate their appearance and course. There are usually two individual MPN branches, and they should be cut as distally as possible, then coapted to the MCN. The total cross-sectional area of the MPN branches is usually less than that of the MCN. If so, the epineurium of the MCN is opened approximately 270 degrees and subsequently the perineurium is opened and the cross-sectional diameter of the individual fascicles is assessed. Subsequently, the MCN fascicle with a diameter comparable to the MPNs is cut and a direct coaptation is made between the MCN fascicle and the MPNs. Usually, more than half of the MCN can be covered with the MPN donor. Another nerve transfer technique for restoration of elbow flexion uses intercostal nerves (ICNs) as donors and the MCN as recipient. The technique for ICN transfer in adults has been described previously.31 The same surgical technique is applied in infants with NBPL. Either ICN 3 to 5 or 4 to 6 are exposed by means of an undulating, skin

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incision over the ipsilateral chest: the incision starts at the anterior axillary line at the inferior border of the pectoralis major muscle and continues beneath the nipple, extending medially to the costosternal junction. The inferior part of the pectoralis major muscle is shifted upward, with partial detachment of its sternal insertion if necessary. The rib attachments of the serratus anterior muscle usually remain intact. The main branch of the ICN is identified halfway in its ventral course between the external and internal interosseus intercostal muscle by means of blunt dissection in the muscle fiber direction and dissected free over its entire anterior course. Care should be taken to keep the periosteum of the ribs intact in order to avoid rib cage deformities during growth. ICN motor responses are assessed by using electrical nerve stimulation. If feasible, sensory branches are identified by their course toward the skin and left intact after they have been interfascicularly dissected from the main nerve. The three ICNs are then transected as close as possible to the sternum to obtain sufficient length for direct coaptation to the MCN and are tunneled to the axilla. The infraclavicular and intercostal wounds remain separated from each other by an area of intact skin at the anterior axilla, facilitating wound closure and healing. In female infants, if the anatomical localization of sensory innervation to the nipple is uncertain, the third ICN is left untouched to preserve at least partial sensation to the breast. The MC nerve is cut proximally after freeing it from the lateral cord until fascicular intermingling is encountered. No attempt is made to identify the motor branches within the MC nerve. However, the epineurium of the MCN is carefully dissected at the site of the stump in order to perform a targeted coaptation of the ICNs to the MCN fascicles. Before coaptation, the infant’s arm is abducted 90 degrees. The ICNs are coapted to the centrally located MC nerve fascicles by means of fibrin glue. Other nerve transfer techniques have been described in literature using the phrenic nerve as donor, or an isolated fascicle of the ulnar or median nerve, or an intact nerve in an end-to-side fashion.32 The use of the phrenic nerve at an early age might carry the risk of pulmonary problems in the immediate postoperative period lasting to adulthood, so it is not employed in our center. The authors do not routinely use the ulnar nerve fascicle to MCN (biceps muscle branch) transfer nor the median nerve fascicle to the MCN (brachialis muscle branch) transfer, as alternative options as described earlier have always sufficed. The technique and results in NBPL have extensively been described.33,34,35 These techniques theoretically carry potential risks for hand function, although this has not been investigated systematically. Some authors employ the triceps branch to axillary nerve transfer for augmentation of shoulder function, but large series have not been published yet. The end-to-side option is not reliable enough for routine use.32 The use of the hypoglossal nerve as donor was abandoned after it

The Neonatal Brachial Plexus Lesion: Surgical Strategies became apparent that volitional control after reinnervation does not restore. The reinnervated muscle contracts only when the tongue is pushed against the hard palate. Consequently, when patients talk or eat, they cannot move the limb.36,37 Much less is known about the quality of central control following transfer of the contralateral C7 spinal nerve in NBPL infants. Therefore, the authors have not used the contralateral C7 spinal nerve as a donor so far.38,39 This transfer might be a salvage option in those rare cases with avulsion of all five roots.

19.4 Assessment of the Severity of the Lesion The severity of the NBPL lesion of each clinically involved spinal nerve is assessed. A distinction is made between axonotmesis, neurotmesis, and root avulsion on the basis of (1) inspection of the status of nerve continuity at the intraforaminal level in combination with presence or absence of root filaments on MRI myelography; (2) the extent and location of neuroma formation; and (3) selective electrical stimulation of all of the involved spinal nerves using a bipolar forceps in combination with a 2.5-Hz pulse generator with increasing voltage (maximum 6 V). Intraoperative nerve action potential (NAP) and compound motor action potential (CMAP) recordings did not add to the decision-making during surgery in infants with NBPL in our experience.40 Systematically recording from damaged nerves and control nerves of the upper brachial plexus showed statistically significant differences between normal, axonotmesis, neurotmesis, or root avulsion groups. For the individual patient, however, a clinically useful cut-off point for NAP and CMAP recordings to differentiate between avulsion, neurotmesis, axonotmesis, and normal could not be found. The sensitivity for an absent NAP or CMAP was too low for clinical use. A spinal nerve root is considered avulsed when the nerve at the intraforaminal and juxtaforaminal level exhibits root filaments, the dorsal root ganglion is visible, neuroma formation is absent, and there are no muscle contractions after direct stimulation. During surgery for NBPL, it is unusual to find the avulsed nerve completely out of its foramen; it remains often attached with a pseudocontinuity, which is lost as one progressively dissects further proximally into the foramen. For this reason, it is indispensable to perform a very proximal dissection, with adequate resection of the anterior scalene muscle. These findings usually correspond with the absence of root filaments on MRI or CT myelography. Avulsions are found quite frequently; even in supposedly simple C5–C6 lesions, radiological examination showed a root avulsion or partial avulsion in 11/26 of patients.41 Avulsed roots are cut as proximally as possible. When the dorsal root ganglion can be morphologically identified, it is dissected from the ventral root and removed. After confirmation by frozen section of the presence of ganglion cells, it is cer-

tain that the distal stump consists only of the ventral root. This ventral root can be the target for nerve grafting, or the ventral root can be attached to a qualitatively good nerve stump directly without a nerve graft. A spinal nerve is considered neurotmetic when the following features are present: a normal appearance at the intraforaminal level, a clear increase of the cross-sectional diameter at the juxtaforaminal level (▶ Fig. 19.2), abundant epineurial fibrosis, loss of fascicular continuity, and increased consistency and increase of the length of the nerve elements with concomitant distal displacement of the trunk divisions. Electrical stimulation of the spinal nerve proximal to the neuroma may cause weak muscle contractions that are detectable with palpation but are not strong enough to move the limb. Resection of neurotmetic tissue is performed, and the proximal and distal stumps are prepared for nerve reconstruction. After resection of the neuroma, the proximal and distal stumps are examined with frozen section histology. The quality of the proximal stump is evaluated by the percentage of myelination, and corresponds with outcome.42 Additionally, amount of scar tissue and architecture of the proximal and distal stumps are evaluated, to decide whether further resection is indicated.43 A spinal nerve is considered axonotmetic when neurolysis reveals no substantial increase of the cross-sectional diameter, only limited epineurial fibrosis, and intact fascicular continuity. Furthermore, on C5 stimulation, abduction with movement of the limb and some external rotation should be present, and on C6 stimulation, elbow flexion against gravity with supination should be found. Axonotmetic nerves are left in situ because spontaneous nerve regeneration is in process, although as yet clinically not clearly apparent. Axonotmesis is confirmed by the occurrence of good spontaneous recovery after at least 2 years of follow-up.

19.5 Principles Underlying Strategies for Surgical Reconstruction The primary goal of nerve repair in patients with NBPL is restoration of hand grasp function, when indicated. The second priority is restoration of elbow flexion; the third is the restoration of shoulder movements; and the fourth is extension of the elbow, wrist, and fingers. The surgical repair/reconstruction strategy depends on the number of available viable proximal spinal nerve stumps for grafting, the cross-sectional area of the stumps, and the availability of donor nerves for neurotization. The resultant functional outcome is determined by integrity of the specific surgical connections made between proximal and distal stumps. For the purposes of the discussion of surgical strategies, the most common lesions are divided as shown in ▶ Table 19.1.

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The Neonatal Brachial Plexus Lesion: Surgical Strategies

Fig. 19.2 Supraclavicular exploration of the left brachial plexus with neurotmesis of the superior trunk. Surgery was performed at the age of approximately 5 months. (a) Phn, phrenic nerve. C5, spinal nerve C5; ST neuroma, neurotmetic superior trunk. (b) Resection of neuroma. C5, spinal nerve C5; C6, spinal nerve C6; ADST, anterior division superior trunk; PDST, posterior division superior trunk; SSN, suprascapular nerve. (c) Reconstruction: grafting C6-ADST, C5-PDST, and SSN.

Table 19.1 Different neonatal brachial plexus lesion types Group lesion Group 1

N C5, C6 N C5, Av C6 Av C5, C6

Group 2

N C5, C6, C7 N C 5, C6, Av C7 N C5, Av C6, C7 N C5, C6, AV C7, C8 N C5, Av C6, C7, C8

Group 3

N C5, C6, C7, Av C8, T1 N C5, C6, Av C7, C8, T1 N C5, Av C6, C7, C8, T1 Av C5, T1

Abbreviations: Av, avulsion; N, neurotmesis; T1, thoracic nerve 1.

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In the majority of NBPL lesions, nerve traction has resulted in neurotmesis of the upper and/or middle trunk. The classic approach to these lesions is to resect the neuroma and bridge the deficit with autologous nerve grafts. Recently, in adult brachial plexus lesions, the use of nerve transfers has become more popular, as results are at least equal to traditional nerve grafting, or may be superior.44 Advantages of this strategy consist of a shorter distance to the target muscle resulting in quicker recovery, and shorter operating time. The strategy to perform nerve transfers without exploring the brachial plexus, however, carries a number of drawbacks. The first is that it is not logical to leave a repairable lesion in place, and repairs only part of the functions of the superior trunk with nerve transfers. For instance, recovery of elbow flexion may be regained by a fascicular ulnar transfer to the biceps branch of the MCN, but by nerve

The Neonatal Brachial Plexus Lesion: Surgical Strategies reconstruction at the brachial plexus level additionally the brachialis muscle, the brachioradialis muscle, and the superior pectoral muscle are reinnervated, and sensation to the thumb is restored. Moreover, results of nerve grafting at adequate timing has led to very satisfying results in NBPL patients (contrary to adults, in whom nerve reconstruction results are modest—except for elbow flexion), which diminishes the drive to seek surgical alternatives. At present, only small series have been published or presented with relatively short follow-up.45,46 Nerve transfers can only be applied if the ulnar nerve function is intact, and in case of a triple transfer the radial nerve. The use of the SAN partially sacrifices trapezius muscle function, which may have an effect on scapula stabilization. All in all, the authors do not favor sole application of distal transfers for routine use. It may be a viable option in infants who were referred late, as delayed nerve grafting beyond the age of 12 to 18 months is assumed to lead to declining results.

19.5.1 Group 1: C5, C6/Upper Trunk Lesions C5, C6/upper trunk lesions comprise the lesions in the majority of NBPL patients. Three different types of C5, C6 lesions are observed clinically. In type 1, neurotmetic lesions of C5, C6/upper trunk are present. Since hand grasp function is essentially normal, the first priority of surgical intervention is restoration of elbow flexion, followed by reanimation of shoulder movements. The most

common lesion observed intraoperatively is a C5, C6/ upper trunk neuroma-in-continuity.47 The neuroma should be resected and nerve repair using sural nerve grafts is performed (▶ Fig. 19.2). At 4 to 5 months of age, the gap between the proximal and distal stumps is usually 2.5 to 3.5 cm, necessitating the harvest of the sural nerves from both legs. The authors always harvest sural nerves endoscopically using three small horizontal incisions, allowing for improved cosmesis; the length of each harvested nerve is usually 11 to 13 cm (▶ Fig. 19.3). Endoscopic harvesting of the sural nerve is facilitated by attaching the leg with sticky tape in a vertical position on a 90-degree iron bar. The usual strategy for nerve repair includes the use of one graft from C5 to SSN (placed at the rostroventral quadrant of the proximal stump of C5),25 two grafts from C5 to the posterior division of the upper trunk, and four grafts from C6 to the anterior division of the upper trunk. Depending on the size of the proximal stumps and the availability of nerve graft, an alternate strategy may involve a SAN to SSN transfer. Our results indicate that no difference in external rotation exists between nerve repair and nerve transfer to the SSN, which has been confirmed by other surgeons.48,49 A more extensive form of the type 1 lesion exists when extension of the wrist and fingers are decreased in the first few months of life. Intraoperative findings include a partial neurotmetic/axonotmetic lesion at C7 in addition to the neurotmetic lesions of C5 and C6. Palpable muscle contractions in the triceps muscle are present with direct C7 spinal nerve stimulation. Therefore, C5, C6/upper trunk are repaired as described earlier, and C7 is neurolyzed.

Fig. 19.3 Sural nerves are harvested endoscopically. Three small (1.5–2 cm.) horizontal incisions are made in the skin line at the level of the lateral malleolus, midcalf and popliteal fossa. This technique has low percentage of wound infections and provides minimal scars. The length of each harvested nerve is usually 11 to 13 cm. (a) Endoscopic harvesting of the sural nerve is facilitated by attaching the leg with sticky tape in a vertical position on a 90-degree iron bar. (b) Surgeons’ perspective forms dorsal aspect of the right lower leg. Surgical speculum in situ. Scoop in left hand, surgical instrument in right hand, sural nerve visible on TV screen. (c) Completely dissected sural nerve.

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19.5.2 Group 2: C5, C6, C7, (C8) Lesions

Fig. 19.4 Supraclavicular exploration of the left brachial plexus with avulsion C5, C6, breech delivery. Surgery was performed at the age of approximately 4 months. Pseudomeningoceles of C5 and C6 on magnetic resonance myelography. Note the absence of neuroma formation. Direct C5 and C6 stimulation did not evoke muscle contractions. Diagnosis: root avulsion of C5 and C6. Reconstruction: transfer accessory nerve to suprascapular nerve and medial pectoral nerve to half of the cross-sectional area of musculocutaneous nerve. C5 and C6 spinal nerves were left in situ. C5, spinal nerve C5; C7, spinal nerve C6. The spinal nerve C6 cannot be seen from this angle and is located below C5. ADST, anterior division superior trunk; PDST, posterior division superior trunk; Phn, phrenic nerve; SSN, suprascapular nerve; ST, superior trunk.

In the second type of C5, C6/upper trunk lesions, surgical exploration reveals a neurotmetic lesion of C5 and a nerve root avulsion of C6. In this circumstance, the authors perform the following reconstruction for the shoulder: graft repair from C5 to the posterior division of the upper trunk, SAN to SSN transfer. The C6 root is continuous proximally to the neural foramen and has an essentially normal appearance, occasionally punctuated by slimmer nerves as the likely result of demyelination. For elbow flexion and supination, the anterior root filaments of the avulsed C6 root can be transferred to the caudal aspect of C5 with direct coaptation.21 The MPN transfer to MCN can be added considered in addition. The intraplexal transfer of the anterior root filaments of C6–C5 will then only contribute to brachioradialis muscle reinnervation. Factors that determine this decision are cross-sectional area of posterior division of superior trunk and sural nerve grafts, quality of anterior root filaments C6, and coaptation site to C5. In type 3, both C5 and C6 roots are avulsed, and this injury usually results from a breech presentation at birth (▶ Fig. 19.4).50,51 Neither root is useful for nerve repair/ reconstruction (▶ Fig. 19.3). In these instances, the C5 and C6 roots are left untouched in their foramen and nerve transfers are the most viable option: our patients undergo a SAN to SSN transfer combined with an MPN to MCN transfer.

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Patients in Group 2 retain useful preoperative finger grasp function, so restoration of hand function is not a goal of surgical intervention. However, in this group, elbow, wrist, and finger extension are impaired with in addition to minimal or absent elbow flexion and shoulder movements. Group 2 lesions can be divided into four types (▶ Table 19.1). In type 1, a neurotmetic lesion of C5, C6, and C7 is present. Intraoperative findings include C5, C6/upper trunk neuroma-in-continuity coupled with a C7/middle trunk neuroma. The repair is performed in a stepwise fashion. (1) The C5, C6/upper trunk neuroma is resected. (2) The sural nerves are then harvested from both legs to determine the quantity and quality of nerve graft. (3) Based on the availability of graft material, the C7 neuroma is either resected or undergoes extensive neurolysis unless graft material can be harvested from other sites (superficial branch of the radial nerve and/or medial/lateral supraclavicular nerves). The authors opt for neurolysis only if some fascicular continuity is seen within the neuroma. (4) The nerve repair strategy is similar to that for patients in Group 1 described earlier, with the addition of C7/middle trunk repair. In type 2, a C5, C6/upper trunk neuroma-in-continuity along with a C7 nerve root avulsion is present (▶ Fig. 19.5). The upper trunk neuroma is resected. The avulsed C7 root is transected as proximally as possible. If the dorsal root ganglion can be morphologically identified (and confirmed by the microscopic presence of dorsal root ganglion cells), it is dissected from the ventral root and resected. An intraplexal nerve transfer is then performed with direct coaptation from the caudal aspect of the C6 proximal stump to the C7 ventral root filaments. When direct coaptation to C6 is technically impossible, the C7 ventral root can be the target for nerve grafting from the caudal aspect of the proximal C6 nerve stump. For sensory restoration, a direct coaptation of the medial supraclavicular nerve (arising from C4) to the postganglionic sensory part of the C7 root can be performed to innervate the C7 dermatome in the hand. The C5, C6/ upper trunk repair is undertaken as above. Types 3 and 4 are rare. Type 3 consists of C5/upper trunk neuroma-in-continuity with C6, C7 avulsion, and type 4 includes the C8 nerve root avulsion injury. The authors reconstruct type 3 and 4 injuries via (1) graft repair from C5 to the posterior division of the superior trunk, (2) direct coaptation of the ventral root filaments of C6 to the caudal aspect of the proximal C5 nerve stump, and (3) SAN to SSN transfer. The C7 and C8 roots are left in place. If in type 3 lesions, the C5 proximal nerve stump can only accommodate the posterior division of the upper trunk, the C6 and C7 remain untouched and MPN to MCN transfer is performed to restore elbow

The Neonatal Brachial Plexus Lesion: Surgical Strategies

Fig. 19.5 Supraclavicular exploration of the right brachial plexus with neurotmesis C5, C6, and avulsion C7. Surgery was performed at the age of approximately 4 months. (a) Av C7, avulsed C7; C5, spinal nerve C5; C6, spinal nerve C6; Phn, phrenic nerve; ST neuroma, neurotmetic superior trunk; SSN, suprascapular nerve (note its undulating course due to neurotmetic elongation of the superior trunk following the traction lesion). (b) Resected neuroma, dissected root C7. ADST, anterior division superior trunk; Af C7, anterior root filaments C7; PDST, posterior division superior trunk; Pf C7, dorsal root filaments and ganglion C7. Reconstruction: direct coaptation of C7 to C6, grafting C6-ADST, C5-PDST, and SSN transfer supraclavicular medial nerve to postganglionic C7.

flexion. For type 4 lesions, the authors use C5 only for graft repair to the anterior division of the upper trunk.

19.5.3 Group 3: C5, C6, C7, C8, T1 Lesions (Pan-Plexopathy) The infants suffering Group 3 lesions present with a flail arm. Our first priority is the restoration of hand function, followed by elbow flexion and shoulder movements.18 Selection of the distal targets for reinnervation are key to the strategy of nerve repair/reconstruction. Fortunately, complete nerve root avulsion in Group 3 patients is extremely rare. Usually, C5 and C6 suffer postganglionic neurotmetic lesions and C7, C8, and T1 suffer avulsions. Therefore, C5 and C6 proximal stumps are available as donors for graft repair to restore C8, T1, and lower or middle trunk functions. If possible, divide the C8 and/or T1 roots into their respective motor and sensory parts at the neural foramen without violating the vertebral artery. Direct coaptation of the C6 proximal stump to the motor portion of C8 (and T1 if possible) is then performed to restore hand function. For restoration of sensory function, the supraclavicular nerves can be directly coaptated to the postganglionic sensory portions of C8 and/or T1. Graft repair from the remaining part of C6 to the anterior division of the upper trunk and from the C5 proximal stump to the posterior division of the upper trunk is performed, followed by SAN to SSN transfer. The C7 root can either remain in place or the supraclavicular nerves can be coapted to C7 to augment sensory function to the hand. When only one proximal stump is available as a donor for nerve repair/reconstruction, it is used entirely for restoration of hand function. Restoration of elbow

flexion is achieved with ICN transfer to MCN, and restoration of shoulder movement is achieved via a SAN to SSN transfer.

19.5.4 Postoperative Care After nerve repair/reconstruction, the infant’s upper body is placed in a prefabricated cast to limit movement of the head and affected arm for 2 weeks. Patients undergo clinical examinations at our outpatient clinic at specific ages. Active and passive ranges of motion are recorded in degrees, and motor function by the Medical Research Council (MRC) grading system. In addition, the Mallet score52 is recorded for assessment of shoulder function, and the Raimondi hand score is recorded for assessment hand function.53

19.6 Results of Nerve Surgery 19.6.1 Factors That Affect Functional Recovery after Nerve Repair Several factors play a role in functional recovery after nerve repair. These include delay of repair, length of graft, scarring, viability of the proximal stump, and the complexity of functions to be restored. Following nerve repair, the routing of axons at the coaptation site during the outgrowth is random.54 Two factors determine whether functional connections are made. First, axons that successfully crossed the coaptation site may end up in the perineurial supportive tissue between the fascicle

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The Neonatal Brachial Plexus Lesion: Surgical Strategies bundles and grafts. Second, axons may not end up in their original fascicles due to a fascicular mismatch between proximal and distal stumps. This may lead to sensory axons that end up in motor pathways. Furthermore, motor axons with antagonistic central programs may mix due to the misrouting. For instance, axons for flexion and extension may end up in the same nerve that leads to nonfunctional contraction. The fascicular mismatch between proximal and distal stump increases when more nerve tissue is lost due to the lesion. The consequence is that misrouting of axons will increase with gap distance and graft length. Nerve grafting inevitably involves two coaptation sites. The implication is that the phenomena described above will take place twice, both at the proximal and distal coaptation site. Nerve regeneration is far less when the nerve lesion is located proximally, as is the case in BP lesions, as compared to distal lesions. A major reason is that it takes time for axons to elongate over a significant distance to reach the end organ with, as a consequence, a long denervation time. The primary cause of the poor recovery after long-term denervation is a profound reduction in the number of axons that successfully regenerate through the deteriorating intramuscular nerve sheaths. Muscle force capacity is further compromised by the incomplete recovery of muscle fibers from denervation atrophy.55 The success of nerve transfers close to the target end organ is based on time reduction for axons to reach the end organ and thereby reduce the secondary end-organ changes.33

19.6.2 Shoulder Function The results of nerve repairs to improve shoulder function have been published in a number of series, and at first glance it can be concluded that global shoulder function recovery is good.10,56,57,58,59 Our surgical results on external rotation were disappointing, as only 20% of patients were able to perform true glenohumeral external rotation of more than 20 degrees.48 In contrast to this disappointing result of true external rotation, functional evaluation showed that 87% of patients could reach their mouth and 75% of children could reach the back of their head. This illustrates the great ability of the infants to compensate their limited true external rotation by thoracoscapular movements. The outcome of accessory nerve SAN to SSN transfer and nerve grafting from C5 to the SSN in our study was similar. The age at surgery or extent of the lesion had no effect on outcome. A weakness of the study was that the patient characteristics of the two treatment groups proved to be different. In the nerve transfer group, the lesion was more extensive than in the nerve grafting group. This is logical, because in more severe lesions with multiple avulsions, proximal nerve stumps are used to restore other functions, and the SAN to SSN transfer is the only option for reviving external rotation. The equivalence of both surgical options has recently been con-

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firmed by others.49 A strategy was recently proposed to restore external rotation in a subcategory of infants who had spontaneous recovery of elbow flexion, but no recovery of shoulder external rotation.60,61 An SAN to SSN transfer was performed while the superior trunk (and other parts of the brachial plexus) was left intact. As a rule, the patients who were surgically treated with isolated SAN to SSN transfer were older than patients in our series: the mean age of surgery was 22 months. The results showed that 4 months after surgery around three quarters of the patients demonstrated an improvement in active external rotation of at least 20 degrees, and the vast majority had external rotation beyond the sagittal plane with the arm in adduction after 2 years.61 Others found a mean external rotation with the arm in adduction of 30 degrees.60 Certain items concerning this late nerve repair strategy remain to be addressed: (1) the reported remarkable short postoperative interval in which external rotation recovered, (2) the influence of the neurological evaluation method, and (3) possible bias due to splinting or concurrent subscapular release surgery.62 Further study is required in order to determine whether late SAN to SSN transfer is indeed a valuable technique. The disadvantages of partial sacrifice of trapezius muscle function on scapula stabilization are difficult to evaluate, especially at the young age. It is of particular interest whether this technique is reliable and superior to latissimus dorsi/teres major tendon transfer.63

19.6.3 Hand Function The objective of nerve surgical treatment of the infant with a flail arm, the most severe form of NBPL, is to establish use of the affected hand to assist in bimanual activity. Combined with good elbow flexion, strong finger flexion is mandatory for a supportive role in the bimanual execution of daily-life tasks. Restoration of hand function through nerve reconstruction is feasible in infants with NBPL. The authors analyzed their surgical strategy to reanimate hand function and outcome in 33 patients with a flail arm.18 Results after 3 years of follow-up were investigated in 16 infants. Of these 16 patients, 13 had complete discontinuity of the C7, C8, and T1 spinal nerves. Analysis showed that 69% of these 13 gained a functional assisting hand (defined as Raimondi grade 3 or more). Importantly, the recovery of hand function could be attributed solely to the nerve reconstruction. Supported by the results, the authors feel that all effort should be made to restore hand function. In infants, it is the primary goal of surgery. Our strategy to maximize nerve outflow to the hand is not shared by a few authors, who seem reluctant to cut and reconstruct nerve elements contributing to hand function.64,65 Our study was the first that proved beyond any doubt that functional hand reanimation can be achieved, solely on the basis of nerve reconstruction. Prior to our publication, another study

The Neonatal Brachial Plexus Lesion: Surgical Strategies reported that useful restoration of hand function can be achieved.66 However, in this study, results of nerve surgery and of secondary procedures on muscles and/or tendons were combined. It is, therefore, not possible to assess the contribution of nerve surgery to the end result. In addition, the condition of complete discontinuity of C7–C8–T1 was not applied in this series. Following our report, a number of articles addressing the nerve surgical results of hand function restoration were published.56,65, 67,68,69 The surgical strategy applied by the majority of surgeons appears to be similar to ours and the same conclusion was reached. In Birch’s series of 47 patients, 57% regained Raimondi ≥ 4 and even 93% Raimondi ≥ 3.70 Restoration of hand function is feasible and should, if indicated, be given priority over and above other functions.

19.6.4 Elbow Flexion The authors investigated the result of biceps recovery following grafting or transfer in our consecutive series of 416 patients (418 brachial plexus reconstructions) operated between 1990 and 2009. Biceps recovery of MRC grade 3 or better was achieved in 95.5% of patients. Nerve transfers for biceps recovery are employed in the case that nerve grafting is not a viable option due to the severity of the lesion, specifically the presence of root avulsion. Two most frequently employed techniques are ICN transfer or MPN transfer to the MCN. In our series, biceps muscle force MRC 3 or more was gained in 88% of patients.71 The MPN transfer proved better than the ICN transfer (92% vs. 82% reached biceps MRC ≥ 3) although this was not statistically significant. The indication for the ICN–MCN transfer, however, differs from the indication for an MPN–MCN transfer. A prerequisite for the application of an MPN–MCN transfer is that preferably spinal nerves C7–T1 are intact, but at least C8–T1 are intact. In the ICN–MCN transfer group, 11 of 17 patients had a global lesion. The only treatment option, therefore, was an extraplexal–intraplexal nerve transfer. The difference in results may reflect the fact that in the ICN–MCN transfer group, the more severe lesion types were present; otherwise, it might indicate that the pectoral nerve shows intrinsically better potential as donor. Our results compare well to those of others regarding these nerve repairs.13,15,72 Whether a normal function of C7 is mandatory to obtaining a successful result following nerve transfer of the pectoral nerves is a matter for discussion. When the spinal nerve C7 is involved in the traction lesion, loss of the C7 axons results in lower axon content of the pectoral nerves. Intraoperative nerve stimulation is, therefore, an indispensable step toward assessing the function of the MPNs. Only when forceful contractions of the pectoral muscle can be elicited on direct stimulation can the nerve be used for transfer. If contractions are weak, an alternative donor nerve should be favored.

19.6.5 Evaluation of Outcome A proper comparison of results of surgical procedures or surgical strategies between different surgical teams appears to be difficult. Almost all authors use a different scoring system to evaluate their outcome: in a recent systematic review, 59 different evaluation methods were found in 217 articles.73 Thus, the outcome from different centers cannot be pooled and analyzed. In adults, the MRC grading74 of volitional force is often used to express results. This score is, however, dependent on children’s cooperation as it depends on grading muscle force against resistance. An additional drawback is that total failures (M0), near-total failures (M1), and normal function (M5) are rare. Hence, the MRC grading will mostly be M2, M3, or M4. Such a three-way outcome measure is a small basis for statistical analysis to detect factors that might influence results. The same limitation accounts for the Mallet score. It was originally designed as a single score of 1 to 5 to rate shoulder function, but its five different components could be employed for specific research questions.52 A total failure (Mallet 1) is very unusual, as is normal function (Mallet 5) after nerve repair. This implies that outcomes are usually Mallet 2, 3, and 4, which have limited discriminating capacity. The Mallet score was simplified as the Gilbert shoulder score (ranging from 1 to 6), which includes only two components: abduction and external rotation.75 This score has not been used often since its introduction. An alternative approach is to express the results as range of motion instead of force with the advantage that the execution of a motion is easier to assess in children than muscle force (as in the MRC gradation). This method has its own drawbacks. External rotation, for instance, can be assessed in degrees of motion with the arm in adduction or with the arm in abduction. The two methods will produce a different outcome. Because such subtle but important details of the applied evaluation are frequently not reported in articles, it is not possible to compare or pool results from different centers. Another drawback is that the range of active motion also depends on the passive range of motion of the joint. Frequently, the presence of contractures is not reported. An evaluation system for grading muscle function based on joint motion is the Active Movement Scale (AMS), which expresses motion on a 7-point scale.8 Such an approach has the advantage that a 7-point system statistically discriminates better than the three-way MRC or Mallet gradation. The AMS has been validated by its originators.76 The difficulty is that in various articles, joint movements were summated to form a combined limb score, or that means were calculated for motion scores. Such sum scores and means make it difficult to visualize the related clinical picture. The creators overcome this problem themselves by dichotomizing between useful and nonuseful function in key articles, which in turn limits statistical analysis.68 As a positive

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The Neonatal Brachial Plexus Lesion: Surgical Strategies exception, the Raimondi Hand Score is used by most authors to evaluate functional outcome of hand function.53 Apart from neurological examination, functional scores were proposed for evaluation of NBPL. The Assisting Hand Assessment (AHA) was designed for children with a unilateral impairment to evaluate how a child makes use of his/her affected hand in bimanual activity performance.77 Its use has been validated, but the drawback in the AHA is that scoring is time-consuming, as the investigation comprises evaluation of video recordings of various tasks. Thus, it is not applicable in the routine outpatient clinic setting. Such video recording, however, allows for blinding of the investigator for the applied treatment strategy, and also allows scoring by an independent reviewer. Thus, it could be a powerful research tool, but there is currently no general consensus or support. An alternative is the Pediatric Outcomes Data Collection Instrument, which is a patient/parent-derived outcome scale based on a 114-item questionnaire, designed to assess global function, as well as upper-extremity function, mobility, physical/sports activity, comfort/pain, and happiness.78 This patient-based outcome measure evaluates the function of the limb in daily life, and not only neurological function during a visit to the clinic. It has been shown to correlate with neurological performance.78 A more recent development in measuring outcome is application of the International Classification of Functioning, Disability and Health (ICF) model, a model that was developed by the World Health Organization. The aim is to provide a universally accepted description of functioning in various health conditions. Currently, ICF Core Sets have been or are being developed for more than 20 health conditions, including neurological traumas and musculoskeletal diseases like traumatic brain injuries, spinal cord injuries, osteoarthritis, and low back pain. The development of an ICF score set for NBPL is currently in progress.79

19.7 Conclusion An NBPP lesion is not an uncommon birth injury, and 20 to 30% of infants with this condition may have incomplete spontaneous recovery. As a consequence, functional disability remains, which might affect their upper-limb function for the rest of their life. The level of function loss depends on the extent of the nerve lesion. Selection for nerve surgical treatment is difficult and requires experience, as does nerve reconstructive surgery. Good results with this surgery have been obtained, significantly improving the functional level of the arm to a level that would probably not have been reached through spontaneous regeneration and conservative treatment. Specialized centers with a multidisciplinary approach are probably best suited for the treatment of infants affected by NBPP.

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References [1] Clark LP, Taylor AS, Prout TP. A study on brachial birth palsy 1861. Am J Med Sci. 1905; 130(4):670–707 [2] Metaizeau JP, Gayet C, Plenat F. Brachial plexus birth injuries. An experimental study. Chir Pediatr. 1979; 20(3):159–163 [3] Bager B. Perinatally acquired brachial plexus palsy: a persisting challenge. Acta Paediatr. 1997; 86(11):1214–1219 [4] Dawodu A, Sankaran-Kutty M, Rajan TV. Risk factors and prognosis for brachial plexus injury and clavicular fracture in neonates: a prospective analysis from the United Arab Emirates. Ann Trop Paediatr. 1997; 17(3):195–200 [5] Pondaag W, Malessy MJ, van Dijk JG, Thomeer RT. Natural history of obstetric brachial plexus palsy: a systematic review. Dev Med Child Neurol. 2004; 46(2):138–144 [6] Jacobsen S. Occurrence of obstetrical injuries to the brachial plexus on the islands of Lolland and Falster 1960–1970. Nord Med. 1971; 86 (42):1200–1201 [7] Sjöberg I, Erichs K, Bjerre I. Cause and effect of obstetric (neonatal) brachial plexus palsy. Acta Paediatr Scand. 1988; 77(3):357–364 [8] Clarke HM, Curtis CG. An approach to obstetrical brachial plexus injuries. Hand Clin. 1995; 11(4):563–580, discussion 580–581 [9] Gilbert A, Tassin JL. Surgical repair of the brachial plexus in obstetric paralysis. Chirurgie. 1984; 110(1):70–75 [10] Laurent JP, Lee R, Shenaq S, Parke JT, Solis IS, Kowalik L. Neurosurgical correction of upper brachial plexus birth injuries. J Neurosurg. 1993; 79(2):197–203 [11] Pondaag W, Malessy MJ. The evidence for nerve repair in obstetric brachial plexus palsy revisited. BioMed Res Int. 2014; 2014:434619 [12] Terzis JK, Papakonstantinou KC. Management of obstetric brachial plexus palsy. Hand Clin. 1999; 15(4):717–736 [13] Blaauw G, Slooff AC. Transfer of pectoral nerves to the musculocutaneous nerve in obstetric upper brachial plexus palsy. Neurosurgery. 2003; 53(2):338–341, discussion 341–342 [14] Kawabata H, Kawai H, Masatomi T, Yasui N. Accessory nerve neurotization in infants with brachial plexus birth palsy. Microsurgery. 1994; 15(11):768–772 [15] Kawabata H, Shibata T, Matsui Y, Yasui N. Use of intercostal nerves for neurotization of the musculocutaneous nerve in infants with birth-related brachial plexus palsy. J Neurosurg. 2001; 94(3):386– 391 [16] Piatt JH, Jr. Neurosurgical management of birth injuries of the brachial plexus. Neurosurg Clin N Am. 1991; 2(1):175–185 [17] Malessy MJ, Pondaag W, Yang LJ, Hofstede-Buitenhuis SM, le Cessie S, van Dijk JG. Severe obstetric brachial plexus palsies can be identified at one month of age. PLoS One. 2011; 6(10):e26193 [18] Pondaag W, Malessy MJ. Recovery of hand function following nerve grafting and transfer in obstetric brachial plexus lesions. J Neurosurg. 2006; 105(1) Suppl:33–40 [19] Chow BC, Blaser S, Clarke HM. Predictive value of computed tomographic myelography in obstetrical brachial plexus palsy. Plast Reconstr Surg. 2000; 106(5):971–977, discussion 978–979 [20] Walker AT, Chaloupka JC, de Lotbiniere AC, Wolfe SW, Goldman R, Kier EL. Detection of nerve rootlet avulsion on CT myelography in patients with birth palsy and brachial plexus injury after trauma. AJR Am J Roentgenol. 1996; 167(5):1283–1287 [21] Malessy MJ, Pondaag W. Neonatal brachial plexus palsy with neurotmesis of C5 and avulsion of C6: supraclavicular reconstruction strategies and outcome. J Bone Joint Surg Am. 2014; 96(20):e174 [22] Yan J, Horiguchi M. The communicating branch of the 4th cervical nerve to the brachial plexus: the double constitution, anterior and posterior, of its fibers. Surg Radiol Anat. 2000; 22(3–4):175–179 [23] Tubbs RS, Salter EG, Wellons JC, III, Blount JP, Oakes WJ. The triangle of the vertebral artery. Neurosurgery. 2005; 56(2) Suppl:252–255, discussion 252–255

Manual of Peripheral Nerve Surgery | 25.07.17 - 10:02

The Neonatal Brachial Plexus Lesion: Surgical Strategies [24] Arad E, Li Z, Sitzman TJ, Agur AM, Clarke HM. Anatomic sites of origin of the suprascapular and lateral pectoral nerves within the brachial plexus. Plast Reconstr Surg. 2014; 133(1):20e–27e [25] Siqueira MG, Foroni LH, Martins RS, Chadi G, Malessy MJ. Fascicular topography of the suprascapular nerve in the C5 root and upper trunk of the brachial plexus: a microanatomic study from a nerve surgeon’s perspective. Neurosurgery. 2010; 67(2) Suppl Operative: 402–406 [26] Tse R, Pondaag W, Malessy M. Exposure of the retroclavicular brachial plexus by clavicle suspension for birth brachial plexus palsy. Tech Hand Up Extrem Surg. 2014; 18(2):85–88 [27] Hanna A. The SPA arrangement of the branches of the upper trunk of the brachial plexus: a correction of a longstanding misconception and a new diagram of the brachial plexus. J Neurosurg. 2016; 125(2): 350–354 [28] Tse R, Kozin SH, Malessy MJ, Clarke HM. International Federation of Societies for Surgery of the Hand Committee report: the role of nerve transfers in the treatment of neonatal brachial plexus palsy. J Hand Surg Am. 2015; 40(6):1246–1259 [29] Bahm J, Noaman H, Becker M. The dorsal approach to the suprascapular nerve in neuromuscular reanimation for obstetric brachial plexus lesions. Plast Reconstr Surg. 2005; 115(1):240–244 [30] Aszmann OC, Rab M, Kamolz L, Frey M. The anatomy of the pectoral nerves and their significance in brachial plexus reconstruction. J Hand Surg Am. 2000; 25(5):942–947 [31] Malessy MJ, Thomeer RT. Evaluation of intercostal to musculocutaneous nerve transfer in reconstructive brachial plexus surgery. J Neurosurg. 1998; 88(2):266–271 [32] Pondaag W, Gilbert A. Results of end-to-side nerve coaptation in severe obstetric brachial plexus lesions. Neurosurgery. 2008; 62(3): 656–663, discussion 656–663 [33] Liverneaux PA, Diaz LC, Beaulieu JY, Durand S, Oberlin C. Preliminary results of double nerve transfer to restore elbow flexion in upper type brachial plexus palsies. Plast Reconstr Surg. 2006; 117(3):915– 919 [34] Noaman HH, Shiha AE, Bahm J. Oberlin’s ulnar nerve transfer to the biceps motor nerve in obstetric brachial plexus palsy: indications, and good and bad results. Microsurgery. 2004; 24(3):182–187 [35] Oberlin C, Béal D, Leechavengvongs S, Salon A, Dauge MC, Sarcy JJ. Nerve transfer to biceps muscle using a part of ulnar nerve for C5-C6 avulsion of the brachial plexus: anatomical study and report of four cases. J Hand Surg Am. 1994; 19(2):232–237 [36] Blaauw G, Sauter Y, Lacroix CL, Slooff AC. Hypoglossal nerve transfer in obstetric brachial plexus palsy. J Plast Reconstr Aesthet Surg. 2006; 59(5):474–478 [37] Malessy MJ, Hoffmann CF, Thomeer RT. Initial report on the limited value of hypoglossal nerve transfer to treat brachial plexus root avulsions. J Neurosurg. 1999; 91(4):601–604 [38] Chuang DC, Mardini S, Ma HS. Surgical strategy for infant obstetrical brachial plexus palsy: experiences at Chang Gung Memorial Hospital. Plast Reconstr Surg. 2005; 116(1):132–142, discussion 143–144 [39] Lin H, Hou C, Chen D. Contralateral C7 transfer for the treatment of upper obstetrical brachial plexus palsy. Pediatr Surg Int. 2011; 27(9): 997–1001 [40] Pondaag W, Van der Veken LPAJ, Van Someren PJ, van Dijk JG, Malessy MJ. Intraoperative nerve action and compound motor action potential recordings in patients with obstetric brachial plexus lesions. J Neurosurg. 2008; 109(5):946–954 [41] Steens SC, Pondaag W, Malessy MJ, Verbist BM. Obstetric brachial plexus lesions: CT myelography. Radiology. 2011; 259(2):508–515 [42] Malessy MJ, van Duinen SG, Feirabend HK, Thomeer RT. Correlation between histopathological findings in C-5 and C-6 nerve stumps and motor recovery following nerve grafting for repair of brachial plexus injury. J Neurosurg. 1999; 91(4):636–644 [43] Murji A, Redett RJ, Hawkins CE, Clarke HM. The role of intraoperative frozen section histology in obstetrical brachial plexus reconstruction. J Reconstr Microsurg. 2008; 24(3):203–209

[44] Garg R, Merrell GA, Hillstrom HJ, Wolfe SW. Comparison of nerve transfers and nerve grafting for traumatic upper plexus palsy: a systematic review and analysis. J Bone Joint Surg Am. 2011; 93(9):819–829 [45] Ghanghurde BA, Mehta R, Ladkat KM, Raut BB, Thatte MR. Distal transfers as a primary treatment in obstetric brachial plexus palsy: a series of 20 cases. J Hand Surg Eur Vol. 2016; 41(8):875–881 [46] O'Grady K, Power H, Olson J, et al. Functional Outcomes of Nerve Grafting and Triple Nerve Transfers For Upper Trunk Obstetrical Brachial Plexus Injuries. Scottsdale, AZ: ASPN; 2016 [47] van Vliet AC, Tannemaat MR, van Duinen SG, Verhaagen J, Malessy MJ, De Winter F. Human Neuroma-in-Continuity Contains Focal Deficits in Myelination. J Neuropathol Exp Neurol. 2015; 74(9):901–911 [48] Pondaag W, de Boer R, van Wijlen-Hempel MS, Hofstede-Buitenhuis SM, Malessy MJ. External rotation as a result of suprascapular nerve neurotization in obstetric brachial plexus lesions. Neurosurgery. 2005; 57(3):530–537, discussion 530–537 [49] Tse R, Marcus JR, Curtis CG, Dupuis A, Clarke HM. Suprascapular nerve reconstruction in obstetrical brachial plexus palsy: spinal accessory nerve transfer versus C5 root grafting. Plast Reconstr Surg. 2011; 127(6):2391–2396 [50] Geutjens G, Gilbert A, Helsen K. Obstetric brachial plexus palsy associated with breech delivery. A different pattern of injury. J Bone Joint Surg Br. 1996; 78(2):303–306 [51] Ubachs JM, Slooff AC, Peeters LL. Obstetric antecedents of surgically treated obstetric brachial plexus injuries. Br J Obstet Gynaecol. 1995; 102(10):813–817 [52] Mallet J. Obstetrical paralysis of the brachial plexus. II. Therapeutics. Treatment of sequelae. Priority for the treatment of the shoulder. Method for the expression of results. Rev Chir Orthop Repar Appar Mot. 1972; 58 Suppl 1:1, 166–168 [53] Raimondi P. Evaluation of results in obstetric brachial plexus palsy. The hand. Presented at the International Meeting on Obstetric Brachial Plexus Palsy, Heerlen, the Netherlands; 1993 [54] Pan YA, Misgeld T, Lichtman JW, Sanes JR. Effects of neurotoxic and neuroprotective agents on peripheral nerve regeneration assayed by time-lapse imaging in vivo. J Neurosci. 2003; 23(36):11479–11488 [55] Fu SY, Gordon T. Contributing factors to poor functional recovery after delayed nerve repair: prolonged denervation. J Neurosci. 1995; 15(5, Pt 2):3886–3895 [56] Birch R, Ahad N, Kono H, Smith S. Repair of obstetric brachial plexus palsy: results in 100 children. J Bone Joint Surg Br. 2005; 87(8):1089– 1095 [57] Gilbert A, Brockman R, Carlioz H. Surgical treatment of brachial plexus birth palsy. Clin Orthop Relat Res. 1991(264):39–47 [58] Kawabata H, Masada K, Tsuyuguchi Y, Kawai H, Ono K, Tada R. Early microsurgical reconstruction in birth palsy. Clin Orthop Relat Res. 1987(215):233–242 [59] Waters PM. Comparison of the natural history, the outcome of microsurgical repair, and the outcome of operative reconstruction in brachial plexus birth palsy. J Bone Joint Surg Am. 1999; 81(5):649–659 [60] Schaakxs D, Bahm J, Sellhaus B, Weis J. Clinical and neuropathological study about the neurotization of the suprascapular nerve in obstetric brachial plexus lesions. J Brachial Plex Peripher Nerve Inj. 2009; 4:15 [61] van Ouwerkerk WJ, Uitdehaag BM, Strijers RL, et al. Accessory nerve to suprascapular nerve transfer to restore shoulder exorotation in otherwise spontaneously recovered obstetric brachial plexus lesions. Neurosurgery. 2006; 59(4):858–867 [62] Malessy MJA, Spinner RJ. Comment on: accessory nerve to suprascapular nerve transfer to restore shoulder exorotation in otherwise spontaneously recovered obstetric brachial plexus lesions. Neurosurgery. 2006; 59(4):868–869 [63] Duijnisveld BJ, van Wijlen-Hempel MS, Hogendoorn S, et al. Botulinum toxin injection for internal rotation contractures in brachial plexus birth palsy: a minimum 5-year prospective observational study. J Pediatr Orthop. 2016 [64] Dumont CE, Forin V, Asfazadourian H, Romana C. Function of the upper limb after surgery for obstetric brachial plexus palsy. J Bone Joint Surg Br. 2001; 83(6):894–900

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Manual of Peripheral Nerve Surgery | 25.07.17 - 10:02

The Neonatal Brachial Plexus Lesion: Surgical Strategies [65] El-Gammal TA, El-Sayed A, Kotb MM, et al. Total obstetric brachial plexus palsy: results and strategy of microsurgical reconstruction. Microsurgery. 2010; 30(3):169–178 [66] Haerle M, Gilbert A. Management of complete obstetric brachial plexus lesions. J Pediatr Orthop. 2004; 24(2):194–200 [67] Kirjavainen M, Remes V, Peltonen J, Rautakorpi S, Helenius I, Nietosvaara Y. The function of the hand after operations for obstetric injuries to the brachial plexus. J Bone Joint Surg Br. 2008; 90(3):349–355 [68] Lin JC, Schwentker-Colizza A, Curtis CG, Clarke HM. Final results of grafting versus neurolysis in obstetrical brachial plexus palsy. Plast Reconstr Surg. 2009; 123(3):939–948 [69] Terzis JK, Kokkalis ZT. Outcomes of hand reconstruction in obstetric brachial plexus palsy. Plast Reconstr Surg. 2008; 122(2):516–526 [70] Birch R. Brachial plexus injury: the London experience with supraclavicular traction lesions. Neurosurg Clin N Am. 2009; 20(1):15–23, v [71] Pondaag W, Malessy MJ. Intercostal and pectoral nerve transfers to re-innervate the biceps muscle in obstetric brachial plexus lesions. J Hand Surg Eur Vol. 2014; 39(6):647–652 [72] Wellons JC, Tubbs RS, Pugh JA, Bradley NJ, Law CR, Grabb PA. Medial pectoral nerve to musculocutaneous nerve neurotization for the treatment of persistent birth-related brachial plexus palsy: an 11-year institutional experience. J Neurosurg Pediatr. 2009; 3(5):348–353 [73] Sarac C, Duijnisveld BJ, van der Weide A, et al. Outcome measures used in clinical studies on neonatal brachial plexus palsy: a system-

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[74] [75] [76]

[77]

[78]

[79]

atic literature review using the International Classification of Functioning, Disability and Health. J Pediatr Rehabil Med. 2015; 8(3):167– 185, quiz 185–186 O’Brien MD. Aids to the Examination of the Peripheral Nervous System. London: Bailliere Tindall; 1988 Gilbert A. Brachial plexus injuries. London: Martin Dunitz; 2001 Curtis C, Stephens D, Clarke HM, Andrews D. The Active Movement Scale: an evaluative tool for infants with obstetrical brachial plexus palsy. J Hand Surg Am. 2002; 27(3):470–478 Krumlinde-Sundholm L, Holmefur M, Kottorp A, Eliasson AC. The assisting hand assessment: current evidence of validity, reliability, and responsiveness to change. Dev Med Child Neurol. 2007; 49(4): 259–264 Bae DS, Waters PM, Zurakowski D. Correlation of pediatric outcomes data collection instrument with measures of active movement in children with brachial plexus birth palsy. J Pediatr Orthop. 2008; 28 (5):584–592 Duijnisveld BJ, Saraç C, Malessy MJA, Vliet Vlieland TP, Nelissen RGHH, ICF Brachial Plexus Advisory Board. Developing core sets for patients with obstetric brachial plexus injury based on the International Classification of Functioning, Disability and Health. Bone Joint Res. 2013; 2(6):116–121

Lumbosacral Plexus Injuries

20 Lumbosacral Plexus Injuries Debora Garozzo Abstract Lumbosacral plexus lesions usually occur in pelvic traumas and are generally associated with massive lifethreating injuries. Due to the severity of the general situation, during the acute phase they remain undiagnosed in more than 50% of cases. These injuries are mostly due to compression and root avulsions are present in less than 25% of cases. Spontaneous recovery occurs in about 70% of cases, although restitutio ad integrum is often unlikely and sequelae ranging from minor deficits (e.g., hallux extensor or gluteus medius deficits) to a permanent foot drop are common. In spite of the high rate of spontaneous recovery, there are devastating injuries where surgical treatment is the only hope to partially restore the proximal function in the lower limb, allowing the patient to regain independent standing and walking instead of remaining confined to a wheelchair. Differently from the brachial counterpart, a direct and complete access to the lumbosacral plexus is impossible; moreover, given its hidden position in the pelvis, the sacral plexus is difficult to expose and surgery is usually burdened by a high rate of complications and often results in poor outcomes. This certainly explains the reluctance of peripheral nerve surgeons to give surgical indications for these injuries. In recent times, nerve transfers have revived the interest toward lumbosacral plexus surgery, but further evidence is required to establish the validity of such techniques for functional restoration in the lower limb.

posttraumatic lumbosacral plexus injuries (LSPIs) are detected on admission or during the early stage of hospitalization. As they generally occur in severe traumas and patients are often unconscious or uncooperative, the massive life-threatening lesions capture the physicians’ attention and these injuries can easily go unnoticed. Moreover in such circumstances, a thorough neurological examination can be extremely difficult and functional deficits can be simply considered the consequence of the concomitant bone injuries.2,3,4 The traumatic event is often clearly related with the injury pattern, affecting its prognosis and outcome.3,4 In more than 60% of cases, the injury occurs during a car crash. Remaining trapped in the vehicle, the patient sustains a pelvic crush that generally causes compression injuries of the lumbosacral plexus.3,4 LPSIs due to motorcycle accidents are far less common3,4 as well as those occurring during traumas after from falling from high, such as in work accidents (e.g., falling from a scaffold) or suicidal attempts; all these events imply high kinetic energy, mostly resulting in traction injuries.3,4 LSPIs due to gunshot are uncommon (▶ Fig. 20.1), probably because they are often lethal; on the contrary, iatrogenic injuries (after hip arthroplasty or pelvic and abdominal surgery) are frequently encountered.3,4 During breech delivery, an LSPI can occur, but it is extremely rare (▶ Fig. 20.2).3,4

Keywords: lumbosacral plexus, root avulsions, foot drop, nerve transfers, pelvic trauma, sacroiliac joint separation, sacral fracture

Bilateral lumbosacral plexus impairment of different severity can be encountered.3,4,5 Four injury patterns are usually described: lumbar plexus injury, lumbosacral trunk injury, sacral plexus injury, and complete LSPI (see ▶ Table 20.1). Sacral plexus injuries and lumbosacral trunk injuries are statistically predominant.2,3,4 In sacral injuries and total palsies, the neurological presentation may include loss of sphincter control, sexual disturbances, and severe, excruciating pain. These symptoms should always raise a red flag as they are associated with root avulsions.3,4 As LPSIs are sustained in severe pelvic traumas, fractures, and dislocations concomitant, endopelvic organs and vascular injuries are usually found. Bone injuries occur in more than 90% of patients.2,3,4 All kinds of pelvic fractures can be encountered, yet some are statistically prevalent and correlated with the typology of causative mechanism (see ▶ Table 20.1). In particular, note that it is clearly stated in the literature that sacroiliac joint separations are regularly associated with root avulsions.2,3,4

20.1 Epidemiology and Causative Mechanisms Described in the medical literature as late as in the 1960s,1 posttraumatic injuries of the lumbosacral plexus have received less attention than other nerve lesions, particularly their brachial counterpart. This dearth of information seems related with their presumed rarity; although no precise statistical data are available on their real incidence, it is generally assumed that they occur in 1% of pelvic traumas. Yet in recent years, it has been emphasized that they might simply remain undiagnosed and their real incidence could be between 40 and 52% of pelvic ring traumas.2 Apparently, less than 50% of

20.2 Clinical Pictures

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Lumbosacral Plexus Injuries

Fig. 20.1 Clinical examples of lumbosacral plexus injuries. (a) Sequelae of obstetrical lumbosacral plexus palsy due to breech delivery in a 5-year-old boy. (b) Sequelae of sacral plexus palsy in a 32-year-old man after gunshot injury.

Fig. 20.2 Sacral fracture responsible of sacral root compression in the foramina.

Injuries of endopelvic organs (extraperitoneal bladder rupture, intestinal perforation of the terminal sigmoid colon or rectum) and vascular injuries (gluteal or iliac artery/vein rupture with retroperitoneal bleeding) are, respectively, detected in 30 and 10% of these patients3,4 and may require urgent treatment.

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20.3 Management LSPIs should always be suspected in pelvic traumas. Early electromyogram (EMG) has been recently suggested in order to overcome the limits of the neurological examination during the acute phase.6

Lumbosacral Plexus Injuries Table 20.1 Clinical presentation according to injury patterns Injury patterns

Motor impairment

Sensory loss

Remarks

Lumbar plexus injury

Iliopsoas, quadriceps, hip adductors

Anterior, medial, and lateral surfaces of the thigh and medial aspect of the lower leg

Iatrogenic injuries are common Femoral fractures in 50% of cases No avulsions Spontaneous recovery mostly occurs

Lumbosacral trunk injury

Glutei, peronei, tibialis anterior and posterior, extensor digitorum, and hallucis longus

Mainly L5 dermatome

The most frequent injury pattern No avulsions High rates of spontaneous recovery

Sacral plexus injury

Glutei, hamstrings, peronei, gastrocnemius, tibialis anterior and posterior, extensor digitorum, and hallucis longus

Buttock and perineum, posterior surfaces of thigh and calf, anterolateral aspect of the lower leg, sole of foot

The second most frequent clinical presentation High incidence of sacral fractures Possibility to detect lower roots avulsions

Complete lumbosacral plexus injury

All the above

All the above

High incidence of sacroiliac joint dislocation Possibility to detect roots avulsions

In sacral fractures allegedly associated with neurological complications, early traction (limiting the rise of the hip bone and the lateral fragment of the aileron) and surgical realignment reduce the compression and clearly favor neurological recovery.2 In gunshot injuries, the missile wound should receive immediate treatment in order to avoid complications, specially infections. On the suspicion of a posttraumatic LSPI, investigations to assess the extension and severity of the nerve damage should be prescribed with the main purpose of revealing the presence of root avulsions. Although electrodiagnostic studies performed 3 to 4 weeks after the traumatic event can distinguish between neuroapraxia and more severe forms of nerve damage, it must be noted that information provided by such techniques is inferred but not directly demonstrated. Thus, imaging is the core of the diagnostic assessment. Three-dimensional (3D) magnetic resonance imaging (MRI) should be considered the first choice of investigation.7 It offers high diagnostic accuracy and is not invasive as myelo-CT (computed tomography). It can also reveal muscle denervation in correlation with signal intensity chances.7 Nowadays, it is generally accepted that the absence of pseudomeningoceles does not exclude avulsions and vice versa (intact roots have been visualized inside them). However, these bulky, mushroom-like images subsequent to the dural tear occurring when the roots are violently pulled out from the spinal cord are still fundamental in the diagnostic assessment of plexual injuries. Pseudomeningoceles need a few weeks to form; therefore, neuroradiological studies are conveniently performed 3 to 4 weeks after the trauma. Apparently avulsions are found in less than 25% of LSPIs and only in sacral plexus and complete LSPIs; L5 and S1 are the most frequently avulsed roots, whereas the upper roots are never found avulsed.3

Once the diagnostic assessment is accomplished, a peripheral nerve surgeon should evaluate whether the injury is amenable of spontaneous recovery or if surgery should be offered to the patient. Regardless of the indication for surgery or conservative treatment, early and intensive physiotherapy is strongly recommended to prevent muscle degeneration and joint stiffness. If needed, specific braces should be prescribed. Severe pain is often reported. In addition to the sequelae of bone injuries, it is often the consequence of deafferentation following root avulsions. Pain management is of paramount importance. Severe and uncontrolled pain is detrimental, strongly limiting or making physiotherapy impossible and completely disrupting the patient’s quality of life. Adequate pain control usually requires a multidisciplinary approach and should encompass medical therapy (e.g., tricyclic antidepressants, opiates, and pregabalin), physical treatments, and psychological counseling. Mirror visual feedback treatment (effective in chronic pain of central origin) could possibly have a role, but no experience is presently available in these cases. The importance of psychological issues has clear evidence. When patients are reintegrated into socially and professionally active lives, pain control is more easily achieved. Nevertheless, it must be admitted that in severe deafferentation pain, treatment is often ineffective and surgical options (e.g., drezotomy) must be taken in account. Sildenafil is also offered to patients with impaired sexual functions.

20.4 Natural History Spontaneous recovery of LSPIs occurs in 50 to 70% of cases, usually starting 8 months after the trauma.3 Average time of recovery is 18 months but can occasionally last up to 36 months. The low rate of avulsions does not

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Lumbosacral Plexus Injuries seem to be the only explanation for this frequent favorable evolution. The lumbosacral plexus is known to present anatomical variations, with extradural or intradural anastomosis and extradural nerve root divisions. Collateral sprouting from healthy or less severely injured neighboring nerves could contribute to the recovery.5 Follow-up shows that complete, spontaneous recovery seems the rule in lumbar plexus injuries associated with femoral fractures along with the reabsorption of the hematoma that forms around the fracture as well in those cases associated with a hematoma in the psoas.3 When caused by traction of self-retraining retractors, iatrogenic injuries also present favorable evolution.3 For the remaining patterns, when no avulsions are detected, spontaneous recovery also occurs in high percentage. However, complete restitutio ad integrum is unlikely and minor sequelae (e.g., hallux extensor and gluteus medius deficits) are common.2,3,4 In some cases, spontaneous recovery may only involve the sciatic medial trunk with a permanent foot drop.2,3,4

20.5 Indication for Surgery In LSPIs where neuroradiological exams reveal multiple avulsions, surgery should be promptly advocated, being the only expendable option not only to regain partial function, but also to relieve pain. Yet it must be admitted that early exploration and repair of LSPIs is not realistic. These patients are generally late referral cases for the consistent delay in diagnosis or the need to postpone the nerve repair after concomitant injuries have been treated. When the diagnostic assessment rules out avulsions, if a neurotmesis is not deemed a likely event, conservative treatment may be initially offered; however, if no signs of spontaneous recovery appear clinically or at EMG within 5 to 8 months after the traumatic event, indication for surgery should be given. In long-dating injuries, nerve surgery has unfavorable outcome and functional restoration can be achieved by tendon transfers. Such procedures can be applied also in case of inadequate recovery after nerve repair, provided that a donor muscle is expendable (M4 or more). Transposition always implies a reduction in muscle strength and if the muscle to be transposed is already flabby or weak, the procedure is doomed to fail.

20.6 Main Principles in Repair Strategy Differently from the brachial plexus, easily and completely explored via an anterior approach, a complete exposure of the lumbosacral plexus is not possible via a single approach. Root transections, contusions, or avul-

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sions require a posterior approach, whereas the lumbar plexus is explored via an anterior approach. Given its hidden position in the pelvis, access to the sacral plexus requires a multidisciplinary approach and encompasses a high rate of complications. On the other hand, surgical outcome has clearly proved remarkably unfavorable in comparison with the brachial counterpart. All this has resulted in a nihilistic attitude toward lumbosacral plexus surgery. Even in cases not amenable of spontaneous recovery, most surgeons refrained from giving an indication for surgery. In more recent times, in the wave of the enthusiasm aroused by the favorable outcome of nerve transfers in brachial plexus injuries, lumbosacral plexus surgery is going through a rebirth of interest. A few reports have been published prompting peripheral nerve surgeons to resume and further develop it. In order to counterbalance such tendency, it must be honestly admitted that the surgical series reported in the literature are statistically not significant, mostly being just case reports with successful outcome. Moreover, nerve transfer often imply the sacrifice of a donor nerve whose value must be carefully assessed in the economy of the general function of the limb. For instance, in a case of a complete palsy where the obturator nerve has been spared, its choice as a donor nerve involves the loss of the adductors necessary when the patient moves from the bed to the wheelchair. In evaluating the repair strategy in LSPIs, the surgeon must have a clear vision of the advantage that the surgery could actually offer, the adjunctive deficit/s and its/their role on the overall situation according to the donor/s chosen for the possible nerve transfers as well as having a correct idea of the level and the extension of the nerve injury in planning the repair strategy.5,7 In complete LSPIs, it must be considered that surgical reinnervation may require more than one procedure.5,7 It must be stated as preliminary remark that distal functional restoration of the lower limb is not possible, but also not necessary. Even a complete palsy of the foot does not impair standing and walking. Surgery aims and may only restore proximal muscles (iliopsoas, glutei muscles, and quadriceps) which control hip and knee stability and leg flexion/extension, basic requirements to allow independent standing and walking instead of being confined to a wheelchair.5,7 In lumbar plexus injuries, the goal of surgery is to restore iliopsoas and quadriceps; this can be achieved by direct repair of the femoral nerve or, when this may turn out technically impossible, by nerve transfers. Concerning the latter, a transfer from the obturator nerve (generally spared in most lumbar plexus injuries) to the femoral nerve is the technique of choice by most surgeons.7,8,9 Alternatively, some authors5,10 have attempted to transfer the 10th and 11th intercostal nerves to the intraabdominal femoral nerve.

Lumbosacral Plexus Injuries Intradural nerve root ruptures

Intradural repair of ventral roots

a) With possibility to retrieve both stumps at intradural exploration b) With retrival of intradural proximal root stump and extradural distal stump

Intradural-extradural root repair with interposition graft

Ipsilateral or contralateral intradural root transfers with interposition grafts Root avulsions Ipsilateral-extradural extraplexual nerve transfers with interposition graft a) With available distal stumps b) Without distal stumps Nerve transfers

Intrapelvic injuries

Intrapelvic repair

Fig. 20.3 Flowchart showing a synopsis of the repair when applied in nerve reconstruction for LSPIs.

In long-dating lumbar plexus injuries or when femoral nerve reinnervation is impossible or fails, knee extension can be restored by tendon transfer, usually employing a combination of the biceps femoris and semitendinosus muscles.11 In sacral plexus injuries, hip stability is the main goal of surgery. Intradural repair of ruptured ventral sacral roots is rare and the surgeon usually resorts to other techniques such as homolateral or contralateral root transfer to the distal root stumps or to the gluteal nerves. Alternatively a femoral nerve to the gluteal nerves/medial sciatic trunk can be considered.5,7 In total palsy, surgery should be focused on restoring iliopsoas, glutei muscles, and quadriceps, and the choice on the expandable repair strategies is dependent on the presence of root avulsions.5,7 As previously pointed out, spontaneous recovery may be associated with sequelae varying from impairment of toe dorsiflexion or gluteal medius weakness to foot drop. Tendon transfers may contribute to improve hip stability (e.g., vastus lateralis muscle transfer or ventral transposition of the gluteus maximus to completely paralyzed gluteus medius)11 or can restore foot dorsiflexion (tibialis tendon transfer).7 ▶ Fig. 20.3 schematically shows a synopsis of the repair strategies applied in nerve microreconstruction according to the different kinds of LSPIs.

References [1] Finney LA, Wulfman WA. Traumatic intradural lumbar nerve root avulsion with associated traction injury to the common peroneal nerve. Am J Roentgenol Radium Ther Nucl Med. 1960; 84:952–957 [2] Tonetti J, Cazal C, Eid A, et al. Neurological damage in pelvic injuries: a continuous prospective series of 50 pelvic injuries treated with an iliosacral lag screw. Rev Chir Orthop Repar Appar Mot. 2004; 90(2): 122–131 [3] Garozzo D, Zollino G, Ferraresi S. In lumbosacral plexus injuries can we identify indicators that predict spontaneous recovery or the need for surgical treatment? Results from a clinical study on 72 patients. J Brachial Plex Peripher Nerve Inj. 2014; 9(1):1 [4] Garozzo D. Trauma to lumbosacral plexus. In: Fessler R, Sekhar L eds. Atlas of Neurosurgical Techniques. New York, NY: Thieme; 2016:870–880 [5] Lang EM, Borges J, Carlstedt T. Surgical treatment of lumbosacral plexus injuries. J Neurosurg Spine. 2004; 1(1):64–71 [6] Weis EB, Jr. Subtle neurological injuries in pelvic fractures. J Trauma. 1984; 24(11):983–985 [7] Garozzo D, Ferraresi S. Approach to lumbosacral plexus. In: Fessler R., Sekhar L, eds. Atlas of Neurosurgical techniques. New York, NY: Thieme; 2016:903–911 [8] Campbell AA, Eckhauser FE, Belzberg A, Campbell JN. Obturator nerve transfer as an option for femoral nerve repair: case report. Neurosurgery. 2010; 66(6) Suppl Operative:375–, discussion 375 [9] Tung TH, Chao A, Moore AM. Obturator nerve transfer for femoral nerve reconstruction: anatomic study and clinical application. Plast Reconstr Surg. 2012; 130(5):1066–1074 [10] Zhao S, Beuerman RW, Kline DG. Neurotization of motor nerves innervating the lower extremity by utilizing the lower intercostal nerves. J Reconstr Microsurg. 1997; 13(1):39–45 [11] Penkert G, Fansa H. Peripheral nerve lesions. Nerve surgery and secondary reconstructive repair. Springer; 2004:164–166

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21 Facial Nerve Palsy: Indications and Techniques of Surgical Repair Stefano Ferraresi Abstract A peripheral facial nerve palsy may be the consequence of different clinical problems. This chapter will purposely exclude the congenital cases. They are a very particular subset of these palsies and recognize different strategies, including free flaps, the discussion of which goes far beyond the scope of this chapter. Among the facial palsies also we would exclude the Bell’s and the Ramsay Hunt zoster palsies. Especially the last ones are usually more severe, and in selected cases they can attain a surgical indication, but the full range of possible treatments, including botulin toxin, free flaps or boost neurotizations is very variable and difficult to classify. Therefore, object of the treatise will be all the conditions in which the facial nerve may be potentially interrupted, severely scarred or compressed, thus requiring a surgical exploration aimed at repair of the nerve. The conditions encountered are the following: ● Injury of the facial nerve at the extracranial level. ● Injury of the facial nerve at the intratemporal level (skull base fracture and special tumours). ● Iatrogenic injury of the facial nerve in the cerebellopontine angle: under these conditions usually the proximal stump of the nerve is not available. ● Special cases, namely, nuclear peripheral nerve palsies at the level of the brainstem, are a very rare occurrence and the correct treatment is uncertain. Keywords: facial nerve palsy, skull base tumours, hypoglossal nerve, intratemporal translocation, facio-facial cross-face, geniculate ganglion, masseteric nerve, House– Brackmann score, temporal bone fracture, temporalis muscle

21.1 Introduction Generally speaking, the ideal method to restore the function of the facial muscles is a facio-facial suture, when suitable proximal and distal stumps of the facial nerve are at hand. The patients submitted to this kind of repair show the best aesthetical and functional results. They may reach a good to excellent House–Brackmann grade (I, II, or III) depending on several factors (age, timing of repair, distance from the brainstem, direct suture vs. graft) and their recovery is the only one potentially able to show a static, voluntary, and emotional response of the face.1,2,3,4 In the vast majority of the facial nerve cases, however, the proximal stump is not available, usually because it is

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lost at the brainstem, as it happens after complex skull base surgery. Under these conditions, the technique more frequently used is a nerve transfer with a donor nerve different from the facial nerve. All the possible options will be critically analyzed in terms of choice of the donor and, for each donor nerve, the different nuances of repair will be elucidated. Any subheading will report the number of operated cases; this is not to discuss in detail the clinic of each patient treated, but just to give an idea of the distribution of this pathology through a 20-year period in a dedicated neurosurgical setting.

21.2 Surgical Techniques and Results 21.2.1 Extracranial Nerve Repair (10 Cases) An injury in the extracranial portion of the facial nerve must be repaired with a facial-to-facial approach. The only exception to repair is represented by the malignant tumours of the face, where the necessity of full clearance may discourage the preservation of useful distal stumps, and when the recovery is strongly jeopardized by local factors (severe scarring, radiotherapy). In these cases, one may recur to a secondary dynamic temporalis transfer, for example, the one popularized by D. Labbè.5 Excluding tumours in the face, we are usually dealing with stab or knife wounds, iatrogenic injuries, and, rarely, gunshot injuries (▶ Fig. 21.1). In these cases, the exploration and retrieval of the injured stumps may be a painstaking task, but very often it is a matter of ability and luck directly depending on the surgeon's experience. The authors strongly make a plea for those cases, rare, of stab wounds in the region of the tragal pointer, where a proximal stump is no longer present. Due to the possibility that different specialists may be involved in such cases, there is a consistent risk of resorting to an extrafacial nerve transfer, like the hypoglossal, to treat these lesions. One must always bear in mind that the best results come from a facio-facial nerve repair. Therefore, for these cases, the correct solution is only one: a dissection of the temporal bone to reach a good proximal stump followed by a graft repair. Any other solution would unduly lower the quality of the recovery.

Facial Nerve Palsy: Indications and Techniques of Surgical Repair ● ●

● ●

Accessory nerve spinofacial anastomosis (1 case). Hypoglossal nerve (42 cases: 28 jump-graft technique + 14 intratemporal translocation). Masseteric nerve (9 cases). Mixed neurotizations (2 cases).

As a matter of fact only the last three are used nowadays. The facio-facial cross-face is very seldom planned, while the spinofacial is only anecdotical and is no longer used.

Facio-Facial Cross-Face (4 Cases)

Fig. 21.1 Gunshot injury to the face—birdshots—attempt at suicide.

21.2.2 Intracranial Repair with Proximal Stump Available (3 Cases) In course of skull base approaches (transotic, infratemporal type B, translabyrinthine, geniculate ganglion tumours), the surgeon may be in the condition of a straightforward repair of the facial nerve. Either with a direct suture or with a graft, the nerve may be “suspended in the air,” with the possibility of mobilization of the coapted stumps. If there is enough space, the author recommends protecting the suture with a sleeve of vein covered with fibrin glue and containing the two extremities sutured with Nylon 9–0. From time to time, in course of cerebellopontine angle (CPA) tumors operated by the retrosigmoid route, the proximal stump of the facial nerve may be localized at the brainstem, but the distal stump into the IAC (internal auditory canal) is absent. Under these circumstances, a sural nerve graft may be sutured, in a second stage, to the distal extracranial facial nerve. This procedure is, for the above-mentioned reasons, preferable to a transfer done with a different nerve. This intracranial–extracranial repair is a very rare occurrence, but it gives good results and it is worth doing (Dott’s technique).6

21.2.3 Nerve Transfers When the Proximal Stump Is Unavailable (58 Cases) The possible donors historically used7,8,9,10 to supply a facial nerve without proximal stump are the following: ● Facio-facial cross-face (4 cases).

This was a potentially very promising technique,11 because of the theoretical possibility of an emotional response offered by the contralateral sound face. A redundant branch of the normal facial nerve, usually found in the nasolabial fold area, acts as a donor. A sural nerve graft is then passed subcutaneously across the upper lip, if possible using a bifurcation to cover the two main branches to the orbicularis of the eye and of the mouth. The problem with this technique, which gives very poor results, is manifold. The author has seen 0/4 useful results and the same disappointing results are also shared by many of the author’s colleagues committed to facial nerve surgery. In spite of an accurate search, it is very difficult to find a powerful donor with enough axons to cover the whole contralateral paralyzed face. The relative length of the graft, in our cases ranging from 12 to 15 cm, is probably another important obstacle, and so it is the time interval between injury and referral, often too long. To overcome this aspect, a variant of the technique has been forwarded by Terzis,12 and is called “the babysitting technique.” It consists of a two-stage procedure: as a first step, an hypoglosso-facial anastomosis is performed, and a graft, sutured to a donor branch of the contralateral normal facial nerve, is left loose in the face, in the vicinity of the recipient. Approximately 1 year later, after the recovery warranted by the hypoglossal nerve, the recipient facial nerve is cut and re-sutured to the distal stump of the graft formerly left free and innervated by the contralateral normal facial nerve branch. This last technique, however, has several limitations: one is the difficulty to move around the scar of the first surgery without damaging the graft and the recipient branches, and the second concerns the opportunity to abort a favorable reinnervation in favor of an unknown result which, far from being guaranteed, also has never been convincingly demonstrated. Presently we do not ordinarily plan a facio-facial crossface, but still we like very much the theoretical possibilities of this procedure. In very early referrals (few days after a facial nerve section), after accurate informed consent, this treatment is considered. Early referrals are always very rare, partly for a lack of coordination among

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Facial Nerve Palsy: Indications and Techniques of Surgical Repair the neurosurgical centers but more often because, in many patients, the anatomical preservation of part or of the entire facial nerve discourages an early reinnervation, entrusting these patients to the physical therapy and to an endless sequence of electromyographies.

Spino-Facial Anastomosis (1 Case) As to the authors’ experience, this technique works, at least in the only case that the authors had the possibility to operate about 20 years ago. This was a patient with an acoustic tumour who had been formerly operated in the tongue area, with a partial damage to the hypoglossal nerve, while the use of the masseteric nerve was not yet popular. The technique gives a satisfactory result concerning the resting tone and symmetry.13 At activation of the shoulder, the face dyskinesias are not much disfiguring in themselves, being not so different from the first cases of hypoglosso-facial anastomosis, but the combination with the provoking movement of the shoulder appears rather awkward. In choosing this type of nerve transfer, it is paramount to interrupt only a portion of the accessory nerve, lest the trapezius muscle be paralyzed.

Hypoglossal-Facial Anastomosis (42 Cases) When the proximal stump is lost. this is by far the oldest and most popular technique ever used to reinnervate the facial nerve.14,15,16 The literature is rich of articles dealing with this issue and this because the surgical technique has evolved with time.17,18,19,20,21,22 The main debates are related to the quantity of axons useful for reinnervation (i.e., the percentage of donor nerve that should be interrupted) and the need for a graft. In the last 15 years, a few authors dedicated their attention to avoid the grafting procedure, analyzing different

techniques of intratemporal translocation and rerouting of the recipient facial nerve.23,24,25 At the beginning, the entire hypoglossal nerve was cut and anastomosed to the denervated facial nerve. This entailed a heavy impairment of tongue function which in turn added to the difficulty in chewing due to the facial nerve palsy. Anatomically this is a nonsense, because the square section of the facial nerve is half of the hypoglossal nerve. Then, in turn, it means an excess of motor axons that, far from being necessary to reanimate the facial muscles, provoke disfiguring mass movements in the reanimated muscles. A successful and modern evolution of this transfer has been prompted by M. May,26 who introduced and popularized the so-called jump-graft procedure.

21.2.4 Hypoglossal-Facial Jump Graft (28 Patients) This is a nerve transfer vehiculating via a graft a few axons of the hypoglossal nerve, taken after the emission of the descending branch (to be sure to select powerful motor axons) and directed to the main trunk of the facial nerve identified at the tragal pointer, which acts as recipient (▶ Fig. 21.2). Practically, through a single incision going from the helix to the angle of the mandible, one first identifies the facial nerve at the exit of the stylomastoid foramen checking its functionality. Then one goes lateral and below the mandible where the digastric muscle is found, elevated, and retracted medially with a stitch passed in the tendon. This helps isolate the hypoglossal nerve while crossing the external carotid artery. Normally there is no need to interrupt any arterial branch, while some secondary lingual vein can be ligated to gain the access. The hypoglossal nerve is stimulated after the takeoff of the descending branch and the epineurium is opened. About one-fourth of the nerve is sectioned. A V-shaped

Fig. 21.2 Hypoglossal-facial jump graft with the greater auricular nerve.

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Fig. 21.4 Palpebral sling pedicled from the temporalis muscle.

No one had serious problems with the tongue, although an occasional slight hypotrophy ensued. This depends on the quantity of axons interrupted in the hypoglossal nerve. Fig. 21.3 Result of an hypoglossal jump graft—good reanimation despite advanced age.

small area distal to the interrupted fascicles is removed and a space is created to lodge the graft, cut slantingly and ready to receive the hypoglossal donor axons. The graft is about 5 cm long and can be either found locally, namely, the greater auricular nerve (GAN) of the vagus, or taken from the sural nerve. There is no difference in terms of results between the two options, but the first is preferable, to have the whole surgery done with only one incision. To harvest a good length of the GAN, some more experience is required. One must pay attention from the very beginning of the incision, because the GAN could be inadvertently damaged. The authors have operated 28 patients with this technique and had very good results (▶ Fig. 21.3). Among them, 25 attained a useful HB score (usually III H-B, due to the obvious dyskinesias). Dyskinesias are normally tolerated although, from time to time, they can be disfiguring and require the use of the botulinum toxin. The 3 patients who did not have results, however, were operated later than 18 months after the facial nerve palsy. This time limit, according to our experience, should not be overcome. The early signs of a positive result (a good recovery of symmetry at rest) start on average at about 7 to 8 months after surgery. The eye must be treated separately, with a gold weight or, better, a platinum chain weight, or using a temporalis muscle sling27 (▶ Fig. 21.4).

21.2.5 Hypoglossal-Facial Intratemporal Translocation (14 Patients) Independently from other authors,23,24,25,28,29,30 the interposition of a graft was also avoided and an intratemporal facial nerve dissection in the fallopian canal was performed with the aim to retrieve more proximally the facial nerve. The main problem with this procedure is the relative shortness of the facial nerve stump, even after rerouting of the intratemporal segment, and much attention must be paid to reach without tension the donor hypoglossal nerve (▶ Fig. 21.5). A rule was set that the facial nerve must be skeletonized in the submiddle fossa area, up to the second genu of the facial nerve, where it turns in the facial recess, near the lateral semicircular canal. The rerouting procedure must be very delicate, not to damage the facial nerve where it is devoid of epineurium in the fallopian canal. Then an important obstacle is found at the digastric ridge, where the myofascial connecting fibers are very tough to dissect. Once the facial nerve is out of the stylomastoid foramen, its first branch to the retroauricular muscle is cut. Then the distal stump, now mobilized, is tunneled to reach the area of the hypoglossal loop. Not rarely, the hypoglossal nerve lies far too medial, and it is of paramount importance to progressively approximate, by means of epineurial Tsuge 4–0 stiches, the two nerves, donor and recipient, to have a coaptation without tension.

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Facial Nerve Palsy: Indications and Techniques of Surgical Repair In failures, of course, one can still resort to either free flaps or muscle transfer procedures.27,34,35

Masseteric-Facial Anastomosis (9 Patients)

Fig. 21.5 Intrapetrous facial direct translocation with direct suture (see the masseteric nerve in the upper left insert; the XII nerve, with its descending branch, in the upper right insert).

The authors discovered that there is no need to severely interrupt the hypoglossal nerve.31,32 A small opening in the epi- and endoneurium is enough to place the extremity of the recipient facial nerve, with a very limited if any interruption of the descending hypoglossal motor axons. In 2006, a refinement of this technique was published33 demonstrating the possibility of excellent results by this way, with a well-balanced result and almost no dyskinesias. The authors had 100% good results that were classified H-B II/III because no patient required attenuation of the dyskinesias with botulin toxin. The tongue was absolutely normal and in half the cases a good function of the orbicularis oculi was attained so that the palpebral weight could be removed. Obviously, as already stated earlier in this chapter, the emotional response to laughing or crying is excluded and in extreme conditions (jokes, strong emotions) the deficit appears, in spite of the best possible rehabilitation of the face. The time needed to recover a good muscle tone with symmetry at rest, on average, was 5 months after surgical repair, with peaks as early as 3 months. This can extend the indication to nerve surgery to the late referrals (18–24 months), but this is a delicate issue and good and reliable results cannot be anticipated with certainty. However, due to the safety of the procedure and the lack of additional incisions to harvest a graft, one can dare a little bit more in late cases.

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In the continuous effort to ensure an emotional response, the authors attempted a new procedure, namely, the direct masseteric–facial nerve transfer. The use of the masseteric nerve is not new. Goldberg et al36 and Manktelow et al,37 respectively, identified this nerve as a powerful donor for a free flap. They recommended its use in Mobius congenital cases and for smile reconstruction in adults. A specific use of the motor nerve to the masseter for direct neurotization of the facial nerve has also been described by Spira,38 Bermudez et al,39 Coombs et al,40 and Faria et al.41 However, if the surgery is done in the extracranial portion of the facial nerve, as reported in the ongoing experiences, it still requires the interposition of a graft. The authors have operated on two patients using a graft in the extracranial area, but the results were worse than the hypoglossal-facial jump graft. In the other patients, the authors performed a mastoid submiddle fossa approach with intratemporal translocation. The entire procedure was also named petrofacial–masseteric nerve transfer. The isolation of the masseteric nerve requires an incision parallel to the upper root of the zygoma. The masseter muscle is progressively detached from the zygomatic arch in a posterior to anterior direction. In proximity of the medial tendon, after traversing the masseter muscle in full thickness, in the deep postero-inferior part of the zygoma, the masseteric vessels and the nerve are emerging and the nerve can be isolated and prepared. The distal anatomy of the masseteric nerve in this area shows a bifurcation with further division in other small branches. At the beginning of the experience, one is tempted to harvest only one branch, with the objective of saving some part of the masseter muscle. This is not necessary because none of the operated patients complained of difficulty in chewing and, moreover, the square section of the entire masseteric nerve matches ideally to the recipient facial nerve. The nuances of this technique are the same concerning the intratemporal translocation, including the section of the retroauricular branch at the exit of the stylomastoid foramen (▶ Fig. 21.6). The difference concerns the relative ease with which the donor and the recipient nerves can be coapted and no Tsuge approximating sutures are necessary. The selection of the patients, however, must be more accurate for another reason. After skull base surgery, the hypoglossal nerve is almost never involved. Often, on the contrary, the trigeminal

Facial Nerve Palsy: Indications and Techniques of Surgical Repair nerve lies in the area of the tumour and sometimes it is heavily manipulated. If a patient has a reduced sensation in the face and/or an hypotrophic temporal and masseter muscles, he or she may not be an ideal candidate for this procedure (▶ Fig. 21.7). On three occasions, the authors had to stop and revert to an hypoglossal-facial translocation because the masseteric nerve showed a very weak response even at a 3-mA setting of the nerve stimulator. In a normal response, a powerful contraction of the masseter muscle can be evoked at 0.3-mA stimulation and this is the prerequisite now expected to go on with the operation. The results of this procedure are very good, with H-B II and III (▶ Fig. 21.8).

Fig. 21.6 Facial nerve after mastoid dissection (see the stump of the sectioned retroauricular nerve near the number 3 in the ruler).

On two occasions, the authors were able to get the reinnervation of the frontalis muscle, a target they never obtained in the past (▶ Fig. 21.9). However, also with this technique, the emotional response is bypassed even though the static and volitional results are fully targeted.

Mixed Techniques (2 Cases) On particular occasions, a mixed type of neurotization is attempted.42 The authors have limited but definite experience with the double transfer: the masseteric nerve for the upper face and the hypoglossal for the lower face. Who are the candidates for this type of nerve transfer? Those in whom, for various reasons, it is preferable not to open the mastoid area and, more extensively, the retroauricular area. We are dealing mainly with severe adhesions due to mastoid infections or CSF (cerebrospinal fluid) leaks, particularly if they required a specific treatment as reoperations, prolonged spinal external drain, or prolonged antimicrobial therapy. When the anatomy of the facial nerve consists of a short main extramastoid trunk, dividing into long primary branches bearing few and late distal arborizations, there is a good possibility to perform a direct suture in the upper face via a masseteric-facial transfer. In the lower part, very rarely a direct hypoglossal-facial transfer is possible but, if not, it is likely that the graft will be very short. The results are good at rest; the volitional control requires some more re-education due to the double transfer, while the emotional response remains utopic (▶ Fig. 21.10).

Fig. 21.7 Masseteric-facial translocation— fair result: the masseter nerve had a suboptimal strength.

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Fig. 21.8 Good result of masseteric-facial direct anastomosis with intratemporal translocation.

Fig. 21.9 Recovery of the frontalis muscle (massetero-facial intratemporal translocation).

21.2.6 Timing of Repair

Fig. 21.10 Mixed reinnervation: masseteric nerve transfer to the upper face and hypoglossal nerve to the lower face.

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As a general rule, if we are sure that the nerve is interrupted, the sooner the repair is done, the better. A classic vexing question that with the refinement of the microsurgical techniques poses not so rarely is the complete facial nerve palsy with anatomical preservation of the facial nerve. In acoustic neuromas, particularly, the consultation of the surgical report is of paramount importance to plan the later therapeutic strategy. At a 6-month interval, 50% of the patients show some sign of recovery either clinically or at electromyogram (EMG). A further 25% will start to reinnervate between 6 and 9 months after the iatrogenic injury. After 9 months, the recovery of single cases is anecdotical, and the bad news is that the 25% left will never recover. In anatomically preserved facial nerves maintaining no response at EMG, our current attitude is to perform surgery after 1 year, trying our best not to go too far beyond the 18th month, to maximize the results. For the sake of truth, the intrapetrosal translocation of the facial nerve, allowing a direct suture, has shifted this time limit of some 3 to 4 months. In selected cases, nerve surgery was performed 2 years after the nerve damage, but this extreme deadline, however, is not recommended, because the results are definitely poorer.

Facial Nerve Palsy: Indications and Techniques of Surgical Repair

21.2.7 Facial Nerve Paralysis after Skull Base Fracture (82 Cases) Two modalities of facial nerve palsy occur after a severe trauma with fracture of the skull base: the early paralysis and the delayed. The delayed palsy is a very particular event since it can occur up to 20 days after the trauma. Its physiopathology has not been cleared yet. In general, the nerve surgeon can be of help after a nerve severance, or neurotmesis, while an axonotmetic injury must recover spontaneously. Due to the above-mentioned considerations, the authors never pose an indication to surgery in delayed facial nerve palsies. In a series of 42 patients, 5% of interruption or severe damage with disruption of the facial nerve was found among patients with early paralysis.43 This occurred very often with a transverse fracture of the petrous bone passing through the otic capsule, with severe vestibular symptoms and deafness. Delayed palsies or early facial palsies showing signs of quick recovery, on the opposite, were more associated with a longitudinal fracture of the petrous bone, not traversing the fallopian canal. Electroneurography (ENoG) shows a moderate to severe damage in relationship with longitudinal and transverse fractures of the petrous bone, respectively. The authors recommend surgery by the end of the third month from the traumatic event in those patients with an early complete paralysis and no signs of muscle reinnervation, if a transverse petrous bone fracture, no response at ENoG, and severe damage to the vestibular and auditory nerves occur at the same time. The presence of a longitudinal fracture and the absence of otic symptomatology, even with the same patterns at ENoG and EMG, invite delaying of surgery for 9 months, if absence of any sign of recovery is confirmed.

21.2.8 Nuclear Peripheral Palsy (4 Cases) These are very special and baffling cases. The facial nerve palsy is undoubtedly of the peripheral type, in spite of the integrity of the facial nerve. The typical cases are posterior fossa midline tumors, like ependymomas (three cases) and one patient of sphenopetroclival meningioma who had a spasm in a perforator of the basilar artery with resultant bulbopontine alternating syndrome and facial nerve palsy of the peripheral type. Often, due to the particular nature of the disease, some nuclear cells survive and ensure an emotional response in spite of very weak movements of the face. There is not enough experience and a definite timing cannot be fixed. Many of these cases, moreover, are late referrals. Generally speaking, the authors tend to preserve the valuable

Fig. 21.11 Labbé technique. Distal insertion of the temporalis muscle at level of the coronoid process of the mandible. It will be anchored to the orbicularis oris.

emotional response, although very feeble, to which they add a temporalis muscle transfer done with the Labbé procedure.44 In this technique, the posterior part of the temporalis muscle is detached from the calvarium and the distal extremity of the muscle is harvested from the coronoid process of the mandible (▶ Fig. 21.11). The temporalis muscle may be so mobilized toward the lower face, passing under the zygomatic arch, with preservation of the neurovascular pedicle. The distal tendon is appropriately attached to the modiolus of the orbicularis oris and the mobility of the transfer is double-checked during surgery with the nerve stimulator. This procedure works well enough and leaves untouched the residual function of the facial nerve. On some occasions, an ephaptic reinnervation of the temporalis muscle with offspring microbranches from the neighboring facial nerve has been reported.45

21.3 Conclusion ●

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The three pillars of facial nerve recovery are the following: static, volitional, and emotional. The best quality of results, due to the presence of emotional recovery, is when the facial nerve is repaired anatomically, that is, from the proximal stump of the facial nerve to its distal stump. Prerequisite of the coaptation is the absence of tension at the suture line. If necessary, a graft may be interposed without prejudicing the result. If the proximal nerve is unavailable, one must resort to a nerve transfer with a donor different from the facial nerve. The most frequently employed is the hypoglossal nerve. The hypoglossal nerve has been variably used during time. The best available techniques are the jump-graft

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technique, which requires a pure extracranial approach, and the intratemporal translocation, which requires expertise in temporal bone dissection. Both of them avoid any interference with the function of the tongue. The intratemporal translocation does not need a graft and shortens the time due for the reinnervation; its results, however, do not differ significantly from the jump-graft technique. Both techniques afford very good results.29,46 The masseteric nerve transfer, when the trigeminal nerve is fully intact, is more than a promising technique and yielded some of the best results that the authors ever had, in particular, the recovery of the frontalis muscle. The emotional response, however, still cannot be reached. Despite the fascination of a possible emotional response, the contralateral facio-facial cross-face technique gives very disappointing results. We do not say in absolute terms that it cannot work, but strong requisites are the selection of a sizable redundant donor branch in the sound side of the face and a very short interval between nerve damage and repair. Generally speaking, if the nerve is interrupted, the sooner the repair, the better. When the decision to repair is not clear or strongly debated, such as with anatomical preservation of the facial nerve after acoustic neuroma surgery, the authors undertake a reconstructive surgery at 1 year and only if the EMG has shown no recovery in the meantime. In fractures of the skull base, the association of a complete palsy of the early type, no response at EMG/ENoG, transverse fracture of the petrous bone, and the involvement of the vestibule-auditory functions prompt early exploration of the nerve course in the fallopian canal. Longitudinal fractures of the petrous bone and a normal inner ear function advise waiting for signs of reinnervation at EMG for about 6 to 9 months. Posttraumatic facial nerve palsies of the delayed type have an obvious nerve in continuity and are no longer explored. Peripheral facial nerve palsies at the brainstem, of the nuclear type, are rare and experience is scanty. However, considerable prudence is required before cutting and reinnervating a nerve which is certainly in continuity and has a potential for reinnervation.

References [1] Guntinas-Lichius O, Straesser A, Streppel M. Quality of life after facial nerve repair. Laryngoscope. 2007; 117(3):421–426 [2] Guntinas-Lichius O, Streppel M, Stennert E. Postoperative functional evaluation of different reanimation techniques for facial nerve repair. Am J Surg. 2006; 191(1):61–67 [3] House JW, Brackmann DE. Facial nerve grading system. Otolaryngol Head Neck Surg. 1985; 93(2):146–147 [4] Twerski AJ, Twerski B. The emotional impact of facial paralysis. In: May M, ed. The Facial Nerve. New York, NY: Thieme Inc; 1986:788–794

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[5] Labbè D, Bussu F, Iodice A. A comprehensive approach to long-standing facial paralysis based on lengthening temporalis myoplasty. Acta Otorhinolaryngol Ital. 2012; 32(3):145–153 [6] Dott NM. Facial paralysis; restitution by extra-petrous nerve graft. Proc R Soc Med. 1958; 51(11):900–902 [7] Brenner E, Schoeller T. Masseteric nerve: a possible donor for facial nerve anastomosis? Clin Anat. 1998; 11(6):396–400 [8] Fournier HD, Denis F, Papon X, Hentati N, Mercier P. An anatomical study of the motor distribution of the mandibular nerve for a masseteric-facial anastomosis to restore facial function. Surg Radiol Anat. 1997; 19(4):241–244 [9] May M. Anatomy of the facial nerve for the clinician. In: May M, ed. The Facial Nerve, New York, NY: Thieme Inc; 1986:21–61 [10] Tubbs RS, Loukas M, Shoja MM, et al. The nerve to the mylohyoid as a donor for facial nerve reanimation procedures: a cadaveric feasibility study. J Neurosurg. 2007; 106(4):677–679 [11] Anderl H. Reconstruction of the face through cross-face-nerve transplantation in facial paralysis. Chir Plastica (Berlin). 1973; 2 (1):17–45 [12] Terzis JK. The “baby-sitter” principle: experience and results in 25 cases. In: Stennert ER, Kreutzberg GW, Michel O, Jungehülsing M, eds. The Facial Nerve. Berlin: Springer; 1994:S393 [13] Coleman CC, Walker JC. Technic of anastomosis of the branches of the facial nerve with the spinal accessory for facial paralysis. Ann Surg. 1950; 131(6):960–968 [14] Arai H, Sato K, Yanai A. Hemihypoglossal-facial nerve anastomosis in treating unilateral facial palsy after acoustic neurinoma resection. J Neurosurg. 1995; 82(1):51–54 [15] Donzelli R, Motta G, Cavallo LM, Maiuri F, De Divitiis E. One-stage removal of residual intracanalicular acoustic neuroma and hemihypoglossal-intratemporal facial nerve anastomosis: technical note. Neurosurgery. 2003; 53(6):1444–1447, discussion 1447–1448 [16] Fernandez E, Pallini R, Palma P, Lauretti L. Hypoglossal-facial nerve anastomosis. J Neurosurg. 1997; 87(4):649–650, author reply 650– 652 [17] Arndt S, Maier W, Schipper J, Ridder GJ. Reanimation of facial nerve after skull base surgery by anastomosis with the ansa of the hypoglossal nerve. Otolaryngol Head Neck Surg. 2004; 131(8):267 [18] Asaoka K, Sawamura Y. Hypoglossal-facial nerve side-to-end anastomosis. J Neurosurg. 1999; 91(1):163–164 [19] Cusimano MD, Sekhar L. Partial hypoglossal to facial nerve anastomosis for reinnervation of the paralyzed face in patients with lower cranial nerve palsies: technical note. Neurosurgery. 1994; 35(3):532– 533, discussion 533–534 [20] Hammerschlag PE. Facial reanimation with jump interpositional graft hypoglossal facial anastomosis and hypoglossal facial anastomosis: evolution in management of facial paralysis. Laryngoscope. 1999; 109(2, Pt 2) Suppl 90:1–23 [21] Luxford WM, House JR III. Hypoglossal facial anastomosis. In: Brackmann DE, Shelton C, Arriaga MA, eds. Otology & Neurotology. Philadelphia, PA: WB Saunders Comapny; 1994:742–747 [22] Mori K, Nakao Y, Yamamoto T, Okuma Y, Osada H, Esaki T. Partial (one-third) side-to-end hypoglossal-facial anastomosis ensures facial reanimation without tongue dysfunction. Neurosurg Q. 2007; 17: 180–184 [23] Atlas MD, Lowinger DSG. A new technique for hypoglossal-facial nerve repair. Laryngoscope. 1997; 107(7):984–991 [24] Darrouzet V, Guerin J, Bébéar JP. New technique of side-to-end hypoglossal-facial nerve attachment with translocation of the infratemporal facial nerve. J Neurosurg. 1999; 90(1):27–34 [25] Sawamura Y, Abe H. Hypoglossal-facial nerve side-to-end anastomosis for preservation of hypoglossal function: results of delayed treatment with a new technique. J Neurosurg. 1997; 86(2):203– 206 [26] May M, Sobol SM, Mester SJ. Hypoglossal-facial nerve interpositional-jump graft for facial reanimation without tongue atrophy. Otolaryngol Head Neck Surg. 1991; 104(6):818–825 [27] Rubin LR. Temporalis and masseter muscle transposition. In: May M, ed. The Facial Nerve, New York, NY: Thieme Inc; 1986:665–679

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Facial Nerve Palsy: Indications and Techniques of Surgical Repair [28] Godefroy WP, Malessy MJA, Tromp AAM, van der Mey AGL. Intratemporal facial nerve transfer with direct coaptation to the hypoglossal nerve. Otol Neurotol. 2007; 28(4):546–550 [29] Martins RS, Socolovsky M, Siqueira MG, Campero A. Hemihypoglossalfacial neurorrhaphy after mastoid dissection of the facial nerve: results in 24 patients and comparison with the classic technique. Neurosurgery. 2008; 63(2):310–316, discussion 317 [30] Rebol J, Milojković V, Didanovič V. Side-to-end hypoglossal-facial anastomosis via transposition of the intratemporal facial nerve. Acta Neurochir (Wien). 2006; 148(6):653–657, discussion 657 [31] Koh KS, Kim J, Kim CJ, Kwun BD, Kim SY. Hypoglossal-facial crossover in facial-nerve palsy: pure end-to-sideanastomosis technique. Br J Plast Surg. 2002; 55(1):25–31 [32] Viterbo F, Teixeira E, Hoshino K, Padovani CR. End-to-side neurorrhaphy with and without perineurium. Sao Paulo Med J. 1998; 116(5): 1808–1814 [33] Ferraresi S, Garozzo D, Migliorini V, Buffatti P. End-to-side intrapetrous hypoglossal-facialanastomosis for reanimation of the face. Technical note. J Neurosurg. 2006; 104(3):457–460 [34] Asato H, Harii K, Takushima A. Smile reconstruction using one-stage transfer of the latissumus dorsi muscle. Op Techn Plast Reconstr Surg. 1999; 6(3):197–203 [35] Harii K. Microneurovascular free muscle transplantation for reanimation of facial paralysis. Clin Plast Surg. 1979; 6(3):361–375 [36] Goldberg C, DeLorie R, Zuker RM, Manktelow RT. The effects of gracilis muscle transplantation on speech in children with Moebius syndrome. J Craniofac Surg. 2003; 14(5):687–690 [37] Manktelow RT, Tomat LR, Zuker RM, Chang M. Smile reconstruction in adults with free muscle transfer innervated by the masseter motor

[38]

[39] [40]

[41]

[42] [43]

[44]

[45]

[46]

nerve: effectiveness and cerebral adaptation. Plast Reconstr Surg. 2006; 118(4):885–899 Spira M. Anastomosis of masseteric nerve to lower division of facial nerve for correction of lower facial paralysis. Preliminary report. Plast Reconstr Surg. 1978; 61(3):330–334 Bermudez LE, Nieto LE. Masseteric-facial nerve anastomosis: case report. J Reconstr Microsurg. 2004; 20(1):25–30 Coombs CJ, Ek EW, Wu T, Cleland H, Leung MK. Masseteric-facial nerve coaptation–an alternative technique for facial nerve reinnervation. J Plast Reconstr Aesthet Surg. 2009; 62(12):1580–1588 Faria JCM, Scopel GP, Ferreira MC. Facial reanimation with masseteric nerve: babysitter or permanent procedure? Preliminary results. Ann Plast Surg. 2010; 64(1):31–34 Klebuc MJA. Facial reanimation using the masseter-to-facial nerve transfer. Plast Reconstr Surg. 2011; 127(5):1909–1915 Ferraresi S, May M, et al. Unpublished – oral presentation at the International Conference on Recent Advances in Neurotraumatology. Riccione, Italy September 8–11, 1996 Labbé D, Hamel M, Bénateau H. Lengthening temporalis myoplasty and transfacial nerve graft (VII-V). Technical note. Ann Chir Plast Esthet. 2003; 48(1):31–35 Rubin LR. Rehanimation of the paralyzed face using the contiguous facial muscle technique. Op Techn Plast Reconstr Surg. 1999; 6(3): 167–173 Campero A, Socolovsky M. Facial reanimation by means of the hypoglossal nerve: anatomic comparison of different techniques. Neurosurgery. 2007; 61(3) Suppl:41–49, discussion 49–50

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Benign Peripheral Nerve Tumors

22 Benign Peripheral Nerve Tumors José Fernando Guedes-Corrêa, Francisco José Lourenço Torrão, Jr., and Daniel Barbosa Abstract Mass growth involving peripheral nerves, trunks, and plexus often represents peripheral nerve tumors (PNT). Benign peripheral nerve tumor (BPNT) is a heterogeneous group comprising the majority of PNT. Benign peripheral nerve sheath tumors (BPNSTs) most often include schwannomas and neurofibromas. They can appear spontaneously or related to different types of neurofibromatosis. Benign tumors of nonneural sheath origin are less common masses that also affect peripheral nerves. Clinical presentation of PNT can be asymptomatic or rely on pain, neurological deficits, and unspecific symptoms related to mass effect. Magnetic resonance imaging is the main imaging modality for the diagnosis, evaluation, and treatment planning. Clinical and imaging characteristics can point toward the diagnosis of a benign or malignant tumor. Biopsies should be avoided for suspected BPNT. Definitive diagnosis can only be obtained after surgical excision. Treatment decision must take into account whether the mass is symptomatic or not and the risk of malignancy. Surgical excision is the safest option in cases of symptomatic or asymptomatic growing PNT. Operative techniques for the excision of a probable BPNT should consider mass location and size, as well as the possibility of malignancy. Microsurgical technique and intraoperative identification of functional nerve fibers with electrical stimulation are always mandatory. Complete surgical resection without damaging functional fascicles is the goal. Most patients report significant pain relief and improvement of sensory motor deficits after surgery. Nevertheless, development or worsening of pain and neurological deficits can occur at follow-up. Recurrence rates may vary according to different types of BPNT and predisposing conditions. Keywords: peripheral nervous system, brachial plexus, lumbosacral plexus, peripheral nervous system neoplasms, neurofibromatosis, schwannoma, neurofibroma

22.1 Introduction Mass growth in close proximity to peripheral nerves can represent a peripheral nerve tumor (PNT). These relatively uncommon masses can be either a benign (as schwannoma and neurofibroma) or a malignant PNT.1 They often appear spontaneously but also related to neurofibromatosis type 1 (NF1), type 2 (NF2), or schwannomatosis.2,3,4 In this chapter, we will focus on the benign masses, which comprehend the overwhelming majority of PNT.5,6 Benign PNT (BPNT) represents a heterogenic group of

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lesions. Those neoplasms can also be intrinsic (benign peripheral nerve sheath tumor [BPNST]) or extrinsic (benign tumors of nonneural sheath origin) to the nerve sheath.1,7 In a series of 213 neurogenic masses, 190 (89.2%) were benign PNST and 23 (10.8%) were malignant peripheral nerve sheath tumors (MPNST).8

22.2 Types and Nomenclature Different types of PNT can present different characteristics. BPNST are more commonly reported than nonneurogenic masses.9,10,11 In this chapter, we will discuss the subtypes of BPNST and benign tumors of nonneural sheath origin.

22.2.1 Benign Peripheral Nerve Sheath Tumors Schwannoma Schwannomas (formerly called neurilemmomas) are the most common type of PNT in patients without NF1.2,5,6,11 They are typically well-circumscribed, encapsulated masses of neoplastic Schwann cell origin.12 These tumors arise from a single nerve root or peripheral nerve fascicle and grow in an eccentric fashion, progressively displacing uninvolved fascicles together with adjacent structures.13 Schwannomas are characterized by degenerative changes and variable admixture of compact spindle cellular (Antoni A) areas and hypocellular, microcystic loose (Antoni B) areas, rich in macrophages and collagen fibers.6,12,14 Distinct palisades with a fibrillary core (Verocay bodies) are usual features.15 Although previously reported, intralesional axons are frequently not expected to be present.16 These tumors typically show diffuse, strong expression of S100 protein by immunohistochemistry.12,13 In most cases, schwannomas occur sporadically as solitary masses (▶ Fig. 22.1). However, they are also seen as part of complex disorders as NF2, schwannomatosis, Carney complex, and a syndrome characterized by multiple schwannomas, nevi, and vaginal leiomyomas.3,17,18,19 These tumors are not related with NF1. The association of schwannomas with NF2 and schwannomatosis will be discussed separately. The main pathologic variants include cellular, melanotic, and plexiform schwannomas.12 Cellular schwannomas are relatively uncommon tumors composed mostly of Antoni A areas with increased mitotic activity, and occasional locally destructive behavior.12,13 They lack Verocay bodies and show only small very focal areas with Antoni B pattern (less than 10% of total tumor area).12

Benign Peripheral Nerve Tumors

Fig. 22.1 Schwannoma of the right sciatic nerve. (a) Surgical view of the tumor in situ. (b) Surgical specimen. (c) Surgical cavity.

Melanotic schwannomas are rare, distinct subtypes of schwannomas characterized by marked accumulation of melanin in neoplastic cells, associated melanophages, and epithelioid cells with variable sized nuclei.12 They usually do not present Verocay bodies, microcysts, or a wellformed capsule.12,15 Other melanin-producing neoplasms appear as main differential diagnosis. The presence of psammomatous melanotic schwannomas (a subtype with round, laminated bodies of calcium called psammoma bodies) has to be taken into account, since it is listed as one of the major diagnostic criteria for Carney complex (a rare multiple neoplasia syndrome).4 Unlike other schwannomas, these subtype can undergo malignant transformation.14 Plexiform schwannomas are a rare, less circumscribed subtype usually composed of Antoni A areas.12 They are defined by a plexiform intraneural growth pattern often with multinodularity.12,13 There is a weak association between this subtype and schwannoma predisposing syndromes (e.g., NF2, schwannomatosis).12 As opposed to plexiform neurofibromas, they do not undergo malignant degeneration. Degenerative changes such as nuclear pleomorphism, blood vessel hyalinization, hemorrhage, cystic changes, focal necrosis, and calcifications can be observed in longstanding schwannomas, referred to as “ancient schwannomas.”14

Schwannomas, NF2, and Schwannomatosis NF2 is an autosomal-dominant genetic syndrome with a birth incidence around 1 in 25,000.20 Individuals with this disorder are predisposed to present multiple tumors of the nervous system.17 These patients have higher risk to develop multiple schwannomas involving spinal roots, plexuses, or peripheral nerves in association with bilateral vestibular tumors.18 BPNST associated with NF2 rarely, if ever, undergo malignant transformation.

Schwannomatosis is the third major distinct form of NF, characterized by multiple nonintradermal schwannomas in the absence of the typical bilateral vestibular schwannomas typically observed in NF2.19 The overwhelming majority of patients with this condition present one or more peripheral nerve schwannoma. They represent an important percentage of all individual undergoing schwannoma resections.3 Although previously reported in a small number of patients, there is still need for more data to understand the risk of malignant transformation in patients with schwannomatosis.21

Neurofibroma Neurofibromas are among the most common types of PNST.6,9 They originate from Schwann cells lineage and have either a well-demarcated intraneural or a diffuse infiltrative growth pattern.12 These tumors are composed of constitutive elements of a normal nerve (Schwann cells, fibroblasts), and perineurial-like cells, intercalated with nerve fibers, embedded in a myxoid matrix.13,15 Single or multiple nerve fascicles that enter and leave the tumor can be identified.2 The fact that they present axons with the tumor is important to distinguish them from schwannomas.2 Although there are several cases associated with NF1, a great proportion of neurofibromas occur sporadically.2,6 The association of neurofibromas with NF1 will be discussed separately. According to architectural growth patterns, neurofibromas are divided in localized, diffuse, plexiform, and massive soft-tissue neurofibromas.12 The most common are localized cutaneous neurofibromas, small nodular masses arising from small cutaneous nerve.12,15 Localized intraneural neurofibromas are deeper, focal, lesions that may involve major peripheral nerve or plexus and result typically in fusiform expansion of the nerve trunk.12 On the other hand, a plaquelike enlargement, usually in the head

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Benign Peripheral Nerve Tumors Although it rarely occurs in solitary neurofibromas, malignant transformation of neurofibromas are not uncommon in patients with NF1.26 MPNST are aggressive tumors known to arise from peripheral nerves or a preexisting PNST, especially plexiform neurofibromas with invasive or displacing growth pattern.12 Possibly due to this association MPNST appear in 2 to 5% of NF1 patients, compared to only 0.001% of the healthy population.23,27

Perineurioma

Fig. 22.2 Plexiform neurofibroma of the median nerve in a patient with neurofibromatosis type 1.

and neck region, characterizes the second subtype, diffuse neurofibromas.6,15 Plexiform neurofibromas are nondiscrete multinodular, tortuous, elongated masses characterized by the involvement of multiple adjacent nerve fascicles or components of a nerve plexus12,15 (▶ Fig. 22.2). Their gross appearance has been described as resembling a “bag of worms.”6 Rarely seen as sporadic lesions, they have potential for malignant transformation.12 Histologically, an admixture of areas resembling the two previously cited subtypes of neurofibromas can be often observed.12 Massive softtissue neurofibromas represent a very rare subtype characterized by large size, diffuse infiltration of soft-tissue and skeletal muscle, usually causing regional or singlelimb enlargement.13 The two last cited neurofibroma subtypes are almost always associated with NF1.15 A more pronounced fascicular growth with increased cellularity (characteristic of cellular neurofibroma) and degenerative cytological atypia are unusual features shown by atypical neurofibromas or neurofibroma with ancient change, often raising the suspicion for malignant tumors.12,15 Glandular differentiation, metaplastic bone, and presence of melanin pigment are other very rare morphological findings reported in neurofibromas.12

Neurofibromas and Neurofibroma Type 1 NF1 is an autosomal-dominant genetic disorder with full penetrance and a birth incidence of approximately 1 in 2,600 to 3,000 individuals.22 Patients diagnosed with NF1 present substantially higher risk of developing different types of neurofibromas.2,23 Furthermore, the presence of two or more neurofibromas of any type or one plexiform neurofibroma is included in the NIH (National Institutes of Health) diagnostic criteria for this syndrome (of which two clinical feature are necessary and sufficient for the diagnosis).24 In a whole body imaging study, plexiform tumors were revealed in 40% of the NF1 patients.25

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The PNT comprised of perineurial cells are called perineurioma. These are uncommon, benign tumors that can mimic a number of benign and malignant soft-tissue lesions.28 Perineuriomas have not been associated with NF but can be the source of an MPNST.29 Immunohistochemical and/or ultrastructural confirmation of perineurial cell differentiation are necessary for the diagnosis of such neoplasms. They are positive for epithelial membrane antigen (EMA) and claudin-1 and negative for S100 and neurofilaments, indicating their perineurial cell origin.28 The immunoreactivity for EMA and lack of immunoreactivity for S100 allows the distinction of perineurial cells, which normally surround the nerve fascicles within a nerve, contrary to schwannomas. They can be classified in two main forms: a rare intraneural perineurioma or a relatively more common extraneural soft-tissue perineurioma.12 Intraneural perineuriomas seem to affect most often individuals in the second or third decades and appear as fusiform masses along the path of large nerves.28 They can be accompanied by neurological deficit and/or mass effect. On the contrary, extraneural soft-tissue perineuriomas are usually asymptomatic and seem to occur typically in middleaged adults, with a slight preference for females.28

Hybrid Nerve Sheath Tumors Hybrid nerve sheath tumors represent a rare entity bearing features of more than one histologic type of nerve sheath tumor (▶ Fig. 22.3).30 They can be either solitary or multiple, as well presented by patients with other types of PNST. The most common type is a hybrid schwannoma/ perineurioma.30 Immunohistochemistry with double staining for different proteins can reveal parallel layers of alternating S100 and EMA-positive cells with no coexpression of antigens by the same cell.31 The size of these tumors has been reported to be up to 17.5 cm.31 They usually arise in the dermis and subcutis and occur in a wide anatomical distribution, although they typically occur at the extremities.31 Hybrid nerve sheath tumors, especially hybrid neurofibroma/schwannomas, are common in patients with schwannomatosis and have also shown association with NF1 or NF2.32

Benign Peripheral Nerve Tumors

Fig. 22.3 Hybrid neurofibroma/schwannoma of the right sciatic nerve. (a) Magnetic resonance imaging. (b) Surgical view of the tumor.

Dermal Nerve Sheath Myxoma

Hemangioblastoma

In many contexts, this tumor type has been conflated with neurothekeomas due to ill-defined pathological criteria and unclear determination of specific cell origin in the past. Currently, dermal nerve sheath myxomas are established as an uncommon benign neoplasm, significantly rarer than neurothekeomas. Dermis and subdermis are involved by this type of tumor, which also present a peripheral fibrous border and abundant myxoid matrix. Schwann cells appear to be predominant.33 In immunohistochemical staining, dermal nerve sheath myxoma are positive for S100 and GFAP, which indicates their Schwann cell origin.33 Axons only appear scattered. Due to these features, nerve sheath myxomas are suspected to be related to schwannomas. Dermal sheath myxomas are typically solitary, superficial, painless, multinodular masses in the 0.5- to 2.5-cm size range and located in the distal extremities.33 They can grow slowly over several years and present a peak incidence in the fourth decade.

Hemangioblastomas are rarely seen involving proximal nerve roots or peripheral nerves. The literature on peripheral nerve hemangioblastomas is limited to a few cases.35 Although this type of tumor is commonly associated with Von Hippel–Lindau syndrome, most cases seems to be sporadic. They tend to grow outward beyond the surface of the epineurium from which they arise. Similarly to central hemangioblastomas, pathology consists of neoplastic vacuolated stromal cells within interspersed, highly developed capillary blood vessels.35 Due to the vascular nature of hemangioblastomas, the risk of significant blood loss at surgery is increased for these tumors.35 For this reason, they should not be omitted in the differential diagnosis.

Ganglioneuroma Ganglioneuromas are rare tumors that arise from sympathetic ganglion cells. They are large, slow-growing, encapsulated tumors histologically consisting of mature ganglion cells (neurons), axons, satellite cells, Schwann cells, and fibrous stroma.13 As opposed to schwannomas and neurofibromas, the tumor is not generated by Schwann cells, but by neurons (in fact, their axons). More frequent in young females, such masses can occur anywhere along the sympathetic chain. Mediastinum, retroperitoneum, and adrenal glands are common locations.34 Although usually asymptomatic, they can also be related to specific complains due to local mass effect. Malignant transformation has been reported in some cases.

22.2.2 Benign Tumors of Nonneural Sheath Origin Several different types of benign masses of nonneural sheath origin can affect peripheral nerves. In this chapter, we will discuss the characteristics of desmoid tumors and neurothekeomas, which are the most commonly reported neoplasms of this kind.36,37

Desmoid Tumor Also known as aggressive fibromatosis, desmoid tumors rarely affect nerves.38 This usually happens by secondary involvement.38 These neoplastic masses are often firm masses of fibrous tissue.36 Muscle or muscle fascia are usually the origin site of these infiltrative tumors.7 They are often painful masses, usually affecting proximal and truncal areas.36 Whenever these tumors involve nerves, focal sensorimotor deficits can occur.36

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Benign Peripheral Nerve Tumors

Neurothekeoma The name “neurothekeoma” is used to designate superficial tumors of variable pathology involving small cutaneous nerves. As opposed to nerve sheath myxomas, cellular neurothekeomas have negative S100 staining, which indicates they are not of Schwann cell origin.37 These two distinct clinical entities were inappropriately considered to be of the same type in the past. Additionally, they are negative for EMA, indicating they are not of perineurial cell origin either. These tumors occur in the dermis and are composed of nests and bundles of epithelioid to spindled cells.37 No well-defined encapsulation can be observed. In contrast to nerve sheath myxomas, neurothekeomas have a predilection for the upper limbs and head and neck of pediatric and young adult females.37

22.3 Clinical Presentation The clinical presentation of PNT ranges from an asymptomatic mass growth to unspecific signs and symptoms related to local mass effect, involvement of surrounding tissues, or direct nerve invasion.5,39 More specific clinical presentations can be observed in the setting of NF1, NF2, or schwannomatosis.3,4,18 The first step is the assessment for any feature that may indicate whether the mass can represent a PNT (▶ Fig. 22.4). Together with a location in the surrounding areas of peripheral nerves or plexus, the presence of Tinel’s sign can point toward this diagnosis. In several published series, prevalence of a positive Tinel’s sign in nerve tumors ranged from 25 to 97%.2,5 In our experience, around 95% of the patients with PNT present a positive Tinel’s sign. Although it is clear that such feature cannot be used for the suspicion of different subtypes of PNT, our

Fig. 22.4 Plexiform neurofibroma presenting as a right axillary lump on an NF1 patient. It is also possible to observe the scar from the incisional biopsy performed elsewhere prior to the referral to our service.

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experience is in agreement with some authors suggesting that Tinel’s sign is extremely useful to raise the differential diagnosis of a PNST on clinical examination.5,10 Clinical presentation of PNT may also have specific features according to the different types.1,5 The most significant differences can be noted when comparing the signs and symptoms of benign and malignant PNT.40 Although there is no reliable clinical criteria for the distinction between benign and malignant PNT, several characteristics pointing toward one or another diagnosis must be taken into account in order to guide the therapeutic management.8 Even though this may vary according to tumor location and patient’s profile, BPNT are often less symptomatic.5 Sometimes, these tumors are incidentally found during the clinical investigation or imaging of patients with unspecific or nonrelated conditions.41 In other cases, the clinical presentation of a BPNT can be only a lump, without any other symptom.2 Pain is the most common complaint for both benign and malignant PNT.11,42 However, further description of this symptom may provide hints about the diagnosis.5 For example, pain at rest is rare at benign tumors, but almost always present in cases of malignancy. In the same way, nocturnal and/or severe pain may argue against the diagnosis of BPNT. Also, rapidly intensified pain is not usually observed in benign masses. Sensory-motor deficit is another important finding that can be present in 5 to 84% of PNST.2,6,10,11 However, it becomes evident that further investigation is needed when we take a look at the variability in the prevalence of this symptom in different series. Despite the fact that some deficits can be present in BPNT, significant neurological deficits are not common in cases of BPNT.1,5 Sudden enlargement of a known benign lesion together with acute development of neurological deficits may be an indicator of possible malignant transformation in a patient with NF.23 Most commonly, BPNT is slow growing, painless, smaller than 5 cm, and present a regular shape.8 Such masses usually do not evidence hard consistency on palpation.23 Subcutaneous hemorrhage, which can rarely appear in some cases of PNT, may not be observed in cases of BPNT.43 When a possible PNT is detected, imaging examinations are necessary to confirm this diagnosis and to try to identify other signs of malignancy. Later, it will be important to investigate the combination of clinical and imaging features of those masses in order to check for possible surgical indications.

22.4 Imaging (Magnetic Resonance Imaging) Magnetic resonance imaging (MRI) is the most important imaging modality for the diagnosis, evaluation, and surgical planning of PNT.2,44 Over the last decades, several MRI

Benign Peripheral Nerve Tumors

Fig. 22.5 T2-weighted contrast-enhanced magnetic resonance imaging of a benign peripheral nerve sheath tumors (neurofibroma) of the sciatic nerve in a 45-year-old female. It is a homogeneous mass, not adherent and with no neural tissue invasion.

features have been demonstrated useful for the characterization of tumorlike conditions and the distinction between different types of PNT.40,45 Still, the imaging of schwannomas and neurofibromas is similar, which prevents the distinction between those tumors. Both malignant PNT and BPNT can present in variable sizes. However, benign masses are significantly associated with smaller size. Median lesion size for BPNT ranges from 2.7 to 5.0 cm, against tumor sizes from 7.5 to 9.9 cm for MPNST.2,46 Mean size for BPNT and malignant PNT varies from 3.4 to 5.5 cm and from 7.2 to 10 cm, respectively.2,47,48 Chhabra et al defined 6.1 cm as the optimal cut-off value of PNT size for predicting malignancy.45 In our experience, the majority of benign tumors were less than 5 cm, in contrast to what was observed in the majority of malignant tumors.8 MRI can accurately determine the relationship between the PNT and the adjacent structures (▶ Fig. 22.5).49 BPNT are usually not adhered to other tissues, nor located deeper than fascial planes.40 Absence of perilesional edema and/or invasion of adjacent tissue is also related to benign tumors.45,50 In their series, Ogose et al reported geographic central enhancement to be present only in BPNT.5 Studies concerning possible relations of peripheral enhancement and specific types of PNT presented conflicting results.45,46 MRI scans of PNT can present T1 and T2 signal heterogeneity.44 Heterogeneity on T1-weighted images has been reported by Wasa et al as useful in the differentiation of neurofibromas and MPNST in patients with NF1.46 Imaging of BPNT usually does not present necrosis/cystic change or hemorrhage and such characteristics can also point toward a different diagnosis.46,48

22.5 Electrodiagnostic Testing Despite indicating which nerve structures are involved, electrodiagnostic studies with electromyography and

nerve conduction testing do not play an important role in the evaluation of PNT.51 Even though such testing may provide some information regarding nerve function, they do not help in the distinction between benign and malignant masses. On the other hand, intraoperative electrophysiological monitoring is essential to distinguish functional neural tissues during the surgical resection and will be further discussed in the “Operative Techniques”’ section.

22.6 Biopsy Efficacy and necessity of preoperative invasive diagnostic procedures such as biopsies for the distinction between BPNT and malignant PNT are questionable.52 Furthermore, our experience corroborates with those who emphasized how biopsies can be dangerous to BPNT.30 Levi et al demonstrated that patients who underwent preoperative PNT biopsy had a significantly higher risk for sensory loss or motor deficits after subsequent tumor resection.2 Compared to those who were not biopsied, the odds ratio for developing neurological deficits in patients with a PNT who were biopsied was 2.7 (p < .001).2 In the literature, it has been reported that even graft repair can be required for nerves after they had undergone a biopsy.53 Several patients report an increase of pain after the biopsy.30 It is worth mentioning that the visualization of nerve fascicles when the biopsy is taken is currently not possible in the overwhelming majority of the settings. Thus, biopsies of PNT might cause to unintentional axonal damage that may lead to neuropathic pain.42 Moreover, even after MRI-guided percutaneous biopsy of a PNT, worsening of neuropathic pain has been reported as a possible complication.54 In highly specialized settings, computed tomography (CT) guided core needle biopsies of 41 cases of PNTs induced temporary

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Benign Peripheral Nerve Tumors pain exacerbation post biopsy in only 12% of the cases.55 However, it is still unclear whether factors like tumor size contributed to this low complication rate or if this can be solely contributed to the use of CT guidance. In the future, with the introduction of the newest imaging techniques such as diffusion tensor imaging, the possibility of a better visualization of the nerve fascicle bundles in relation to the tumor might further improve the safety and efficacy of biopsy procedures.56 The high possibility of inducing fibrosis formation is another factor that should be taken into consideration before requesting a biopsy. Whenever a BPNT is highly likely, we should be reluctant regarding the performance of such invasive procedure. The later surgical resection may become technically more demanding since intraneural fibrosis and hemorrhage cause obscuration of tissue planes, which can also lead to higher surgical complication rates.2 These deleterious effects have to be taken into account each time a biopsy in a PNT is considered. Biopsies of PNT should not be performed prior to expert consultation and imaging examinations. Especially if a biopsy is taken from a tumor that potentially is a BPNT, these iatrogenic effects may cause lifelong complaints in patients who could have undergone complete tumor excision with low risks of pain or neurological deficits. Whenever malignancy is suspected, four-quadrant biopsy can be indicated.

22.7 Approach to Treatment Despite the importance of mass preoperative diagnosis for therapeutic decision and surgical planning, difficulties in distinguishing different types of neoplasm prior to the surgery have been reported for a long time. The definitive diagnosis of a PNT regarding malignancy can only be obtained after surgical excision and pathological analysis. Therefore, treatment decision must take into account some major factors: whether the mass is symptomatic or asymptomatic and whether clinical or imaging features related to a differential diagnosis of malignant tumor types are present.

22.7.1 Asymptomatic The management of asymptomatic PNT in patients with or without NF1 is still subject of discussion. The most important and widely accepted fact in this regard is that every case has to be interpreted individually. Didactically, patients with asymptomatic PNST can be divided in four groups. The first two groups consist of patients with NF1: (1) patients with NF1 and multiple stable lesions and (2) patients with NF1 and one or more growing lesions. The other two groups are formed by patients without NF1: (3) patients with neither visible nor palpable mass incidentally found in imaging

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examinations and (4) patients presenting visible or palpable masses. Clinical surveillance and MRI scans every 6 months are the only indications for Groups 1 and 3. On the other hand, surgical excision and follow-up are recommended for Groups 2 and 4. Surgery also must be considered as the safest option in case of enlargement of the masses in patients from Groups 1 and 3. In both patients with or without NF1, progressive enlargement of the mass is the main indicator for the surgical excision of the PNST, since it can lead to a symptomatic presentation. Increase of metabolic activity as shown by PET scans can be used as a possible indication for surgery. Also, the presence of NF1 should be taken into account, since this clinical condition increases the odds for the development of malignancy. The most important aspects regarding treatment decision for asymptomatic PNT can be summarized as follows: ● Surgery allows palpable asymptomatic PNST to be safely removed for cosmetic purpose and to improve quality of life. ● Surgical excision is the safest option in cases of asymptomatically growing PNT in patients with or without NF1. ● Surgery is also the safest option for those masses presenting clinical or MRI features pointing toward a differential diagnosis of malignancy. The delay of this intervention can lead to more severe presentations of the disease. ● Periodic clinical and MRI surveillance are the only indications for nonvisible and nonpalpable asymptomatic PNST incidentally found during investigation of patients with NF1 or nonrelated conditions (e.g., trauma).

22.7.2 Symptomatic Surgical excision of a symptomatic tumor can lead to complete resolution of the symptoms without any new complains in most cases of BPNT. Therefore, this is the recommended treatment approach following referral to a specialist consultation and imaging examinations. Such interventions should be performed in centers with expertise in peripheral nerve surgery.

22.8 Operative Techniques Operative techniques for the excision of a probable BPNT should consider specially the location and size of the mass, as well as the possibility of malignancy.1 Nevertheless, some basic principles in BPNT surgery must be followed judiciously. ● Surgical incision should be planned to allow access to the proximal and distal normal segments of the affected nerve. This will allow the surgeon to work initially in normal anatomical area nerves and progressively address the lesion.

Benign Peripheral Nerve Tumors ●

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A 360-degree release of the tumor area should be performed, taking care not to twist or stretch the nerve trunk. Cottonoids moistened with warm saline solution can be used to protect the nerve during the dissection of circumscribed elements under magnification. The affected segment can be released with movements of tweezers and scissors, parallel to the nerve. Vessel loops are passed in the proximal and distal segments without nerve traction. Next, inspection of the mass surface is realized under the microscope. Frequently, it is possible to visualize groups of fascicles being eccentrically displaced or scattered in the capsular tissue. Using electrical nerve stimulator, a careful mapping of functional nerve fibers is realized near the tumor equator, usually in its point of greater diameter. A “silent” region showing no response to electrical stimulation should be identified. This “silent” area is the window through which the surgeon will be able to penetrate and systematically separate the capsule and the tumor. An initial opening of 0.5-cm length is made longitudinally to the tumor surface with an insulin needle or a no. 11 blade. After opening, microscissors and microforceps are used to slowly expose the lesion, with the separation of the fascicles. Electrical stimulation is used extensively during this phase of the operation. Complete isolation of the lesion from nerve fascicles can often be achieved. It is important to note that the dissection should be directed to the tumor poles to expose its fascicle of origin, which should be sectioned to allow a complete tumor excision.

Therefore, two main factors must be taken into account as part of the strategy for the surgical management of any peripheral nervous system neoplasm: (1) microsurgical technique is mandatory and (2) intraoperative electrical stimulation for intraoperative mapping of functional nerve fibers is mandatory. Intraoperative monitoring should also be considered to assist resection of PNT since it appeared to reduce the risk of postoperative neurological deficit, particularly in neurofibromas.2 Tumor location is the key determinant of the surgical planning. Careful evaluation of imaging studies may help distinguish the anatomical relationship of the mass with the adjacent structures. The surgical approaches may vary for tumors accordingly to its location in the brachial plexus or lumbosacral plexus.9,57

22.8.1 Brachial Plexus Identification and dissection of brachial plexus tumors follow the same previously described principles for PNT surgery. Nonetheless, some points deserve special attention in those cases: ● Anterior supraclavicular approach can be used for the excision of tumors involving roots and trunks. For

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lesions involving the cords and those extending from the cords to the nerves, the infraclavicular approach can be used. The surgical access should be wide, and large masses often require combined supraclavicular and infraclavicular approaches. The posterior approach is used to access spinal nerves at an intraforaminal level, C8–T1 roots, and the lower trunk. It is also a good option in cases when the patient carries severe scarring after an anterior to the plexus. In the supraclavicular approach, the incision follows the posterior edge of the sternocleidomastoid muscle, then tangent to the clavicle and follows toward the deltopectoral groove, allowing for the correct exposition of the plexus. The infraclavicular approach is done in the classical way, and, before the section of the pectoralis minor muscle, finger palpation can be used to detach the adjacent tumor. For large tumors, distal plexual elements should be assessed before directing the dissection toward the mass. The relation of the tumor with the adjacent arteries must also be taken into account. The relationship of the mass and the subclavian vessels must be analyzed in the imaging exams. If the tumor is mostly situated above the line from the sternal notch to the spine, it probably can be resected by the supraclavicular approach, without the need for thoracotomy, even in larger tumors affecting the inferior trunk. All neural elements must be identified with electrical stimulation, dissected, and protected before complete resection of the lesion. As mentioned earlier, electrical stimulation is mandatory. Piecemeal tumor excision is recommended. Possible complications are vascular injuries, phrenic nerve palsies, and lymphatic fistulas.

22.8.2 Lumbosacral Plexus (or Pelvic Plexus) The surgical technique for lumbosacral plexus tumors (LPSTs) also follows the aforementioned principles for PNT surgery. Some special aspects should be taken into account for the treatment of lesions in this location: ● The relationship of the tumor, the sacroiliac articulation, and major blood vessels plays a crucial role in the evaluation of the best method to access the lesion. The approach to the retroperitoneum should be performed by the general surgery team.57 Thereafter, the neurosurgical team proceeds with the approach to the LSP. ● Different approaches and techniques can be used for the surgical excision of LSPTs. ● The anterior transabdominal approach (also known as Pfannenstiel) can be used for tumors affecting lower plexual levels (L5–S1/S2). Patients should be placed in a supine position. A median infraumbilical, paramedia, or Pfannenstiel incision is performed, the peritoneum is opened, and the abdominal viscera are moved away

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Fig. 22.6 Lateral retroperitoneal approach. (a) Surgical positioning. (b) Surgical view of the lumbosacral plexus tumor.

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from the surgical field. This approach allows visualization of pelvic vascular structures and the ureter. Medially to the common iliac artery, a vertical incision is performed to open the posterior peritoneum. Using digital palpation, the tumor can be located. The prerectal approach (also known as modified Pfannenstiel) is recommended for lesions deep in the ischiorectal fossa and can be accessed with this variant of the anterior transabdominal approach. Patients should be placed in supine position with both legs stretched laterally. The surgeon will work in between the legs. As the lesions in the inferior rectal fossa originate from L5–S1–S2 roots, the surgical field should be considerably deep. The lateral retroperitoneal approach (also known as lumbotomy) allows access to levels T12–L4/L5. Patients should be placed in lateral decubitus (▶ Fig. 22.6). The incision will be performed between the 12th rib and the iliac crest, followed by the dissection and medial retraction of the muscles and the peritoneum. After the psoas major muscle is visualized, divulsion along it is performed under the microscope, with special care to identify and protect the ureter. The mass subjacent to the muscle can be felt with digital palpation and progressively exposed. The dorsal approach is useful in the management of lesions in the upper lumbar plexus (T12–L1). Patients should be placed in the prone position. The spinal apophysis will be located with the help of X-ray guidance and the dorsal incision will be performed over it. The paravertebral muscles are dissected, followed by a partial laminectomy and facetectomy. A wide foraminotomy can help the surgeon to gain access to the proximal nerve roots. Microscopic dissection in the surroundings of the spinal canal should follow. After identification of a “silent area” on the mass surface with intraoperative electrical stimulation, the surgeon should proceed with piecemeal resection.

22.9 Surgical Outcome Whenever possible, complete surgical resection with resolution of pain and preservation or improvement of neurological functions is the goal.2 Following surgical excision, patients with PNT in all locations usually report significant pain relief and improvement of sensory motor deficits.1,10 Nevertheless, there is always a risk for the development of new postsurgical pain or neurological deficits. Evidence has shown that the duration of symptoms before surgery is associated with both pain and neurological deficits after intervention.11 Surgical complications can occur specifically related to tumor location and surgical technique.2 A higher proportion of postoperative morbidity has been reported in a series of tumors in the brachial and pelvic plexus.1,11,58 The surgical outcome of PNT will be further discussed according to the histological diagnosis.

22.9.1 Surgical Outcome of Benign Tumors of Neural Sheath Origin Schwannomas Complete resection is possible in the majority of the cases of schwannoma (▶ Fig. 22.7).1,10 Theoretically, surgical excision of schwannomas allows enucleation with preservation of the associated nerve. Resection of at least part of an identifiable nerve is usually unnecessary.2 However, simple enucleation may not be possible for a few cases of large tumors.2 The incidence of new postoperative neurological deficits or pain is limited. Sensory deficits is the most typical complain.2,11 Only in very specific cases, nerve graft repair is required in order to improve the outcome.10 Careful excision of schwannomas usually leads to total or partial resolution of pain with unchanged or improved

Benign Peripheral Nerve Tumors

Fig. 22.7 Surgical excision of a tibial nerve schwannoma.

motor function.9,10 Recurrence is rare and normally associated with schwannomatosis.

Neurofibromas Resection of at least part of an identifiable nerve seems more likely in cases of neurofibromas.2 Some authors report higher rates of intentional subtotal excisions aiming to preserve function.2,10 Similarly to schwannomas, surgical removal of neurofibromas harbors a considerable risk of development or worsening of neurological deficits or pain. The most common complaint is sensory deficit.2 Cases of extended damage can require nerve graft repair.10 Nevertheless, most patients benefit from surgery with complete or partial resolution of pain and preserved or improved preoperative function.1,2 Local recurrence is not common.2

Neurofibromas and NF1 There are still divergences in the literature concerning whether there is a significant difference in the surgical outcome between patients with and without NF1.11 Some authors reported a greater likelihood of new or worse pain and neurological deficits in such patients.1,2 Dissection of neurofibromas in NF1 can be more technically demanding and total excision may be not possible in several cases of plexiform neurofibromas.9 In most cases, surgical excision can lead to reversal of symptoms with good neurological outcome, eliminating the risk of malignant transformation of these masses.1,2,11,59 Even after subtotal removal of large plexiform neurofibromas, partial or complete resolution of pain can often be observed and nerve function is sometimes preserved or improved after surgery.9 Notwithstanding, since the underlying clinical condition cannot yet be treated, tumor recurrence is more common in cases of NF1.

Perineurioma Residual neurological deficit may occur after surgical excision due to the course of axons through the tumor. Importantly, resection can prevent malignant degeneration. Recurrence of perineuriomas is uncommon.28

Hybrid Nerve Sheath Tumor Normally these tumors can be completely removed with good outcome.30 However, in some cases they can show infiltrative margins. Hybrid schwannoma/perineurioma subtypes rarely recur.31 Schwannomatosis or NF is often underlying cases of hybrid neurofibroma/schwannoma.32 Such clinical conditions cannot yet be treated and are more related to recurrence of hybrid nerve sheath tumors.

Dermal Nerve Sheath Myxoma Recurrence is common after surgical resection, sometimes even with multiple tumors.33 Nonetheless, there is no evidence of malignant degeneration of these lesions.

Ganglioneuromas Given the large size and involvement of adjacent structures, total excision may not always be possible, especially when the capsule is adherent to important structures. Notwithstanding, surgical treatment aims to relief the symptoms related to mass effect and diminish the risk of malignant transformation.34 Postoperative autonomic dysfunction and recurrence seem uncommon.34

Hemangioblastoma These tumors can bleed extensively during surgical removal. The outcome may depend on the relation between nerve fascicles and the abnormal vascular tissue

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Benign Peripheral Nerve Tumors removed. When complete resection is accomplished, recurrence is unlikely.35

22.9.2 Outcomes of Operative Benign Tumors of Nonneural Sheath Origin Desmoid Tumor They are locally and regionally infiltrative, which hampers resection. Total excision is difficult and sometimes may require sacrifice of the nerve, leading to focal sensorimotor deficits, which can be improved with nerve grafting.38 In some cases, total resection may not be appropriate since it can lead to great damage to the brachial plexus and adjacent structures.7 Desmoid tumors are frequently recurrent.38

Neurothekeoma Since these tumors are initially believed to be something else (e.g., a schwannoma), normally they are treated by surgical excision. Even following incomplete excision, they rarely recur.37

22.10 Conclusion BPNT represents a group of important clinical entities in peripheral nerve surgery. Special care has to be taken anytime a PNT diagnosis is possible. The management of these neoplasms may differ from that applied to sarcomas and other soft-tissue tumors. Although BPNT usually does not present potential for malignant degeneration, the final histopathological diagnosis of the mass can only be realized after surgical excision. Moreover, individuals with tumor predisposing conditions warrant increased surveillance for the development of masses with possible malignant features. In most cases of symptomatic tumors or asymptomatic growing masses, surgical excision will be the safest treatment option. Microsurgical technique and intraoperative mapping of the nerve fascicles are always mandatory. BPNT treated in specialized centers often present good outcome. In cases of PNT related to systemic syndromes as NF1, NF2, and schwannomatosis, although tumor resection is accomplished successfully, the disease always remains.

References [1] Kim DH, Murovic JA, Tiel RL, Kline DG. Operative outcomes of 546 Louisiana State University Health Sciences Center peripheral nerve tumors. Neurosurg Clin N Am. 2004; 15(2):177–192 [2] Levi AD, Ross AL, Cuartas E, Qadir R, Temple HT. The surgical management of symptomatic peripheral nerve sheath tumors. Neurosurgery. 2010; 66(4):833–840

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[3] Gonzalvo A, Fowler A, Cook RJ, et al. Schwannomatosis, sporadic schwannomatosis, and familial schwannomatosis: a surgical series with long-term follow-up. Clinical article. J Neurosurg. 2011; 114(3): 756–762 [4] Rodriguez FJ, Stratakis CA, Evans DG. Genetic predisposition to peripheral nerve neoplasia: diagnostic criteria and pathogenesis of neurofibromatoses, Carney complex, and related syndromes. Acta Neuropathol. 2012; 123(3):349–367 [5] Ogose A, Hotta T, Morita T, et al. Tumors of peripheral nerves: correlation of symptoms, clinical signs, imaging features, and histologic diagnosis. Skeletal Radiol. 1999; 28(4):183–188 [6] Gabhane SK, Kotwal MN, Bobhate SK. Morphological spectrum of peripheral nerve sheath tumors: a series of 126 cases. Indian J Pathol Microbiol. 2009; 52(1):29–33 [7] Kim DH, Murovic JA, Tiel RL, Moes G, Kline DG. A series of 146 peripheral non-neural sheath nerve tumors: 30-year experience at Louisiana State University Health Sciences Center. J Neurosurg. 2005; 102(2):256–266 [8] Guedes-Corrêa JF, Barbosa DAN. Critical correlation between clinical presentation, imaging and type of peripheral nerve sheath tumors: a surgical approach. World Neurosurg. 2015; 84(2):598 [9] Kim DH, Murovic JA, Tiel RL, Moes G, Kline DG. A series of 397 peripheral neural sheath tumors: 30-year experience at Louisiana State University Health Sciences Center. J Neurosurg. 2005; 102(2): 246–255 [10] Artico M, Cervoni L, Wierzbicki V, D’Andrea V, Nucci F. Benign neural sheath tumours of major nerves: characteristics in 119 surgical cases. Acta Neurochir (Wien). 1997; 139(12):1108–1116 [11] Vetrano IG, Lucarella F, Dalolio M, et al. The importance of predicting factors in the surgical outcome of peripheral nerve sheath tumors. J Neurol Surg A Cent Eur Neurosurg. 2014; 75(2):104–109 [12] Rodriguez FJ, Folpe AL, Giannini C, Perry A. Pathology of peripheral nerve sheath tumors: diagnostic overview and update on selected diagnostic problems. Acta Neuropathol. 2012; 123(3):295–319 [13] Skovronsky DM, Oberholtzer JC. Pathologic classification of peripheral nerve tumors. Neurosurg Clin N Am. 2004; 15(2):157–166 [14] Coulon A, Milin S, Laban E, Debiais C, Jamet C, Goujon JM. Pathologic characteristics of the most frequent peripheral nerve tumors. Neurochirurgie. 2009; 55(4–5):454–458 [15] Le Guellec S. Nerve sheath tumours. Ann Pathol. 2015; 35(1):54–70 [16] Nascimento AF, Fletcher CD. The controversial nosology of benign nerve sheath tumors: neurofilament protein staining demonstrates intratumoral axons in many sporadic schwannomas. Am J Surg Pathol. 2007; 31(9):1363–1370 [17] Antinheimo J, Sankila R, Carpén O, Pukkala E, Sainio M, Jääskeläinen J. Population-based analysis of sporadic and type 2 neurofibromatosis-associated meningiomas and schwannomas. Neurology. 2000; 54 (1):71–76 [18] Evans DG. Neurofibromatosis 2. Bilateral acoustic neurofibromatosis, central neurofibromatosis, NF2, neurofibromatosis type II. Genet Med. 2009; 11(9):599–610 [19] MacCollin M, Chiocca EA, Evans DG, et al. Diagnostic criteria for schwannomatosis. Neurology. 2005; 64(11):1838–1845 [20] Asthagiri AR, Parry DM, Butman JA, et al. Neurofibromatosis type 2. Lancet. 2009; 373(9679):1974–1986 [21] Carter JM, O’Hara C, Dundas G, et al. Epithelioid malignant peripheral nerve sheath tumor arising in a schwannoma, in a patient with “neuroblastoma-like” schwannomatosis and a novel germline SMARCB1 mutation. Am J Surg Pathol. 2012; 36(1):154–160 [22] Lammert M, Friedman JM, Kluwe L, Mautner VF. Prevalence of neurofibromatosis 1 in German children at elementary school enrollment. Arch Dermatol. 2005; 141(1):71–74 [23] Ferner RE, Gutmann DH. International consensus statement on malignant peripheral nerve sheath tumors in neurofibromatosis. Cancer Res. 2002; 62(5):1573–1577 [24] Gutmann DH, Aylsworth A, Carey JC, et al. The diagnostic evaluation and multidisciplinary management of neurofibromatosis 1 and neurofibromatosis 2. JAMA. 1997; 278(1):51–57

Manual of Peripheral Nerve Surgery | 25.07.17 - 10:02

Benign Peripheral Nerve Tumors [25] Plotkin SR, Bredella MA, Cai W, et al. Quantitative assessment of whole-body tumor burden in adult patients with neurofibromatosis. PLoS One. 2012; 7(4):e35711 [26] Valeyrie-Allanore L, Ismaïli N, Bastuji-Garin S, et al. Symptoms associated with malignancy of peripheral nerve sheath tumours: a retrospective study of 69 patients with neurofibromatosis 1. Br J Dermatol. 2005; 153(1):79–82 [27] Amirian ES, Goodman JC, New P, Scheurer ME. Pediatric and adult malignant peripheral nerve sheath tumors: an analysis of data from the surveillance, epidemiology, and end results program. J Neurooncol. 2014; 116(3):609–616 [28] Rankine AJ, Filion PR, Platten MA, Spagnolo DV. Perineurioma: a clinicopathological study of eight cases. Pathology. 2004; 36(4):309–315 [29] Hirose T, Scheithauer BW, Sano T. Perineurial malignant peripheral nerve sheath tumor (MPNST): a clinicopathologic, immunohistochemical, and ultrastructural study of seven cases. Am J Surg Pathol. 1998; 22(11):1368–1378 [30] De Sousa ACS, Chimelli L, Guedes-Correa JF. Abstracts of the XVIII International Congress of Neuropathology, Rio de Janeiro, Brazil, September 14 to 18, 2014. Brain Pathol. 2014; 24 Suppl 1:1–103 [31] Hornick JL, Bundock EA, Fletcher CD. Hybrid schwannoma/perineurioma: clinicopathologic analysis of 42 distinctive benign nerve sheath tumors. Am J Surg Pathol. 2009; 33(10):1554–1561 [32] Harder A, Wesemann M, Hagel C, et al. Hybrid neurofibroma/schwannoma is overrepresented among schwannomatosis and neurofibromatosis patients. Am J Surg Pathol. 2012; 36(5):702–709 [33] Fetsch JF, Laskin WB, Miettinen M. Nerve sheath myxoma: a clinicopathologic and immunohistochemical analysis of 57 morphologically distinctive, S-100 protein- and GFAP-positive, myxoid peripheral nerve sheath tumors with a predilection for the extremities and a high local recurrence rate. Am J Surg Pathol. 2005; 29(12):1615– 1624 [34] Modha A, Paty P, Bilsky MH. Presacral ganglioneuromas. Report of five cases and review of the literature. J Neurosurg Spine. 2005; 2(3): 366–371 [35] Rasulic L, Samardzic M, Bascarevic V, Micovic M, Cvrkota I, Zivkovic B. A rare case of peripheral nerve hemangioblastoma—case report and literature review. Neurosurg Rev. 2015; 38(1):205–209, discussion 209 [36] Siqueira MG, Tavares PL, Martins RS, et al. Management of desmoidtype fibromatosis involving peripheral nerves. Arq Neuropsiquiatr. 2012; 70(7):514–519 [37] Hornick JL, Fletcher CD. Cellular neurothekeoma: detailed characterization in a series of 133 cases. Am J Surg Pathol. 2007; 31(3):329– 340 [38] Ferraresi S, Garozzo D, Bianchini E. Aggressive fibromatosis (desmoid tumor) of the radial nerve: favorable resolution. Case report. J Neurosurg. 2001; 95(2):332–333 [39] Ramcharan R, Midha R. Clinical presentation and physical examination. Neurosurg Clin N Am. 2004; 15(2):125–132 [40] Furniss D, Swan MC, Morritt DG, et al. A 10-year review of benign and malignant peripheral nerve sheath tumors in a single center: clinical and radiographic features can help to differentiate benign from malignant lesions. Plast Reconstr Surg. 2008; 121(2):529–533 [41] Aggarwal G, Satsangi B, Shukla S, Lahoti BK, Mathur RK, Maheshwari A. Rare asymptomatic presentations of schwannomas in early adoles-

[42]

[43] [44]

[45]

[46]

[47]

[48]

[49]

[50]

[51]

[52]

[53]

[54]

[55]

[56]

[57]

[58] [59]

cence: three cases with review of literature. Int J Surg. 2010; 8(3): 203–206 Sughrue ME, Levine J, Barbaro NM. Pain as a symptom of peripheral nerve sheath tumors: clinical significance and future therapeutic directions. J Brachial Plex Peripher Nerve Inj. 2008; 3:6 Bijos PB, Guedes-Corrêa JF. Plexo Braquial. Rio de Janeiro: DiLivros; 2011 Van Herendael BH, Heyman SR, Vanhoenacker FM, et al. The value of magnetic resonance imaging in the differentiation between malignant peripheral nerve-sheath tumors and non-neurogenic malignant soft-tissue tumors. Skeletal Radiol. 2006; 35(10):745–753 Chhabra A, Soldatos T, Durand DJ, Carrino JA, McCarthy EF, Belzberg AJ. The role of magnetic resonance imaging in the diagnostic evaluation of malignant peripheral nerve sheath tumors. Indian J Cancer. 2011; 48(3):328–334 Wasa J, Nishida Y, Tsukushi S, et al. MRI features in the differentiation of malignant peripheral nerve sheath tumors and neurofibromas. AJR Am J Roentgenol. 2010; 194(6):1568–1574 Li CS, Huang GS, Wu HD, et al. Differentiation of soft tissue benign and malignant peripheral nerve sheath tumors with magnetic resonance imaging. Clin Imaging. 2008; 32(2):121–127 Varma DG, Moulopoulos A, Sara AS, et al. MR imaging of extracranial nerve sheath tumors. J Comput Assist Tomogr. 1992; 16(3): 448–453 Stull MA, Moser RP, Jr, Kransdorf MJ, Bogumill GP, Nelson MC. Magnetic resonance appearance of peripheral nerve sheath tumors. Skeletal Radiol. 1991; 20(1):9–14 Demehri S, Belzberg A, Blakeley J, Fayad LM. Conventional and functional MR imaging of peripheral nerve sheath tumors: initial experience. AJNR Am J Neuroradiol. 2014; 35(8):1615–1620 Bhattacharyya AK, Perrin R, Guha A. Peripheral nerve tumors: management strategies and molecular insights. J Neurooncol. 2004; 69 (1–3):335–349 Resnick JM, Fanning CV, Caraway NP, Varma DG, Johnson M. Percutaneous needle biopsy diagnosis of benign neurogenic neoplasms. Diagn Cytopathol. 1997; 16(1):17–25 Schoeller T, Huemer GM, Shafighi M, Gurunluoglu R, Wechselberger G, Piza-Katzer H. Microsurgical repair of the sural nerve after nerve biopsy to avoid associated sensory morbidity: a preliminary report. Neurosurgery. 2004; 54(4):897–900, discussion 900–901 Carrino JA, Khurana B, Ready JE, Silverman SG, Winalski CS. Magnetic resonance imaging-guided percutaneous biopsy of musculoskeletal lesions. J Bone Joint Surg Am. 2007; 89(10):2179–2187 Pianta M, Chock E, Schlicht S, McCombe D. Accuracy and complications of CT-guided core needle biopsy of peripheral nerve sheath tumours. Skeletal Radiol. 2015; 44(9):1341–1349 Cage TA, Yuh EL, Hou SW, et al. Visualization of nerve fibers and their relationship to peripheral nerve tumors by diffusion tensor imaging. Neurosurg Focus. 2015; 39(3):E16 Guedes-Corrêa JF, Basílio-de-Oliveira CA, Santos M, de Amorim RMP, Megali R. Lumbosacral plexus tumors. Report of two cases and literature review. Arq Bras Neurocir. 2008; 27(3):96–101 Dafford K, Kim D, Reid N, Kline D. Pelvic plexus tumors. Neurosurg Focus. 2007; 22(6):E10 Donner TR, Voorhies RM, Kline DG. Neural sheath tumors of major nerves. J Neurosurg. 1994; 81(3):362–373

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23 Malignant Peripheral Nerve Sheath Tumors Jennifer Hong, Jared Pisapia, Paul J. Niziolek, Viviane Khoury, Paul Zhang, Zarina Ali, Gregory Heuer, and Eric L. Zager Abstract Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive, soft-tissue sarcomas that originate from or differentiate into nerve structures. Although these tumors are rare, they are clinically challenging to treat with a 5-year survival of 50%. Patients with neurofibromatosis type 1 (NF1) and previous radiation exposure are at higher risk for development of MPNST. We review the epidemiology, radiology, pathology, pathogenesis and cancer genetics, workup, treatment, and prognosis of these tumors in this chapter. Keywords: malignant peripheral nerve sheath tumor, MPNST, neurofibromatosis type 1, surgical resection, chemotherapy, radiation therapy, prognosis

23.1 Introduction Malignant peripheral nerve sheath tumors (MPNSTs) are rare, aggressive soft-tissue sarcomas that arise from or differentiate toward cells of the peripheral nerve sheath. The term MPNST was instituted by the World Health Organization (WHO) in 2002 to unite historically splintered terminology including “neurofibrosarcoma,” “malignant schwannoma,” “neurogenic sarcoma,” and “malignant neurolemma.”1 The diversity of pseudonyms for MPNST reflects the varied histopathology and behavior seen in these tumors. Arthur Purdy Stout (1885–1967) first characterized peripheral nerve sheath tumors including MPNST in 1935.2 He identified the Schwann cell as the progenitor of the majority of MPNST3; however, MPNSTs have been reported to contain histologically diverse cell types including rhabdomyoblast, fibroblasts, and perineurial cells, leading some to speculate that there may be multiple cell types of origin.4 MPNSTs are further subclassified into three categories, based on their clinical presentation: sporadic, neurofibromatosis type 1 (NF1) associated, and radiation induced (RT). Current evidence suggests that each subgroup of MPNST appears to have a distinct presentation and prognosis.

23.2 Epidemiology MPNSTs account for 3 to 10% of soft-tissue sarcomas,5,6,7 resulting in an overall incidence of 1.46 per 106 people per year.8,9 The incidence appears to be slightly higher in men with an M:F ratio reported in large series between 1:1 and 2:1.10,11,12,13,14 Based on analysis of the Surveillance, Epidemiology, and End Results (SEER) database, among racial groups, there is statistically significant

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lower incidence in Asian or pacific islanders compared to Caucasians, with a trend toward increased incidence in African Americans.9 Overall, the incidence of MPNST is greatest in the seventh decade of life (▶ Fig. 23.1a). The most common age at diagnosis is between 20 and 50 years,5,15,16,17 with less than 10 to 20% of tumors diagnosed in the first two decades of life.10 Although MPNSTs comprise a small portion of sarcomas in adults, they are among the most common nonrhabdomyosarcomatous soft-tissue sarcomas in children.10,18

23.2.1 Neurofibromatosis Type 1 NF1 is an autosomal dominant neurocutaneous genetic syndrome caused by mutation of the Neurofibromin gene on chromosome 17. It was initially described by Friedrich von Recklinghausen in 1882.19 Patients may present with multiple neurofibromas and classic skin and eye findings of café au lait spots, axillary freckling, and Lisch nodules. Patients with NF1 are at much higher risk for developing MPNST, and they have an estimated cumulative lifetime risk of up to 10%.20 In addition, MPNSTs are 18-fold more likely to occur in NF1 patients with an internal plexiform neurofibroma than those without one.21 MPNSTs arise approximately one decade earlier in patients with NF1 with a peak incidence between age 20 and 30 years (▶ Fig. 23.1b).5,11,15,16,22,23 Histologically, background of preexisting neurofibroma is usually seen in association with MPNST. NF1-associated MPNSTs account for 20 to 50% of all MPNSTs in large case series.4,5,11,12,13,14,15,16,24,25

23.2.2 Previous Radiation Approximately 10% of MPNSTs are diagnosed in areas that were sites of previous radiation fields in the treatment of previous malignancies.12,14,15,22,24 These tumors occur between 4 and 41 years after radiation exposure,4,5,26 and account for only 4% of radiation-induced sarcomas.22

23.3 Clinical Presentation MPNSTs commonly present as asymptomatic enlarging masses, or with pain, neurologic deficits, or paresthesias. Patients with NF1 are more likely to have larger tumors, pain with presentation, or sudden change in known neurofibromas.15,16,22 Routine total body imaging of patients with NF1 is recommended to monitor and survey for malignant transformation, which evolves in 10% of plexiform neurofibromas.27 Although MPNSTs are usually solitary, 5 to 19% of patients have metastases at the time of diagnosis.15,24 There have also been rare reports of patients presenting with multiple primary MPNSTs.5

Malignant Peripheral Nerve Sheath Tumors

Fig. 23.1 (a) Incidence of malignant peripheral nerve sheath tumor (MPNST) by age group extracted from SEER database 1973–2009. Brackets equal the 95% confidence interval for each group. (Reproduced with permission from Bates et al.9) (b) Distribution of age at presentation for MPNST in patients with NF1 (VR) versus sporadic tumors (NVR). (Reproduced with permission from Ducatman et al. 1986.5)

Anatomic sites of MPNST are diverse. They most frequently occur in the proximal extremities, followed by the trunk, then head and neck.12,14,16,25 Commonly involved sites include the sciatic nerve, spinal nerve roots, brachial plexus, lumbosacral plexus, and other peripheral nerves. Rarely, MPNST can be seen in the pancreas, thyroid, prostate, breast, mediastinum, cervix, mesentery, liver, and other visceral organs.22 In one large series, patients with NF1 were observed to have more axial MPNST, whereas sporadic tumors were more likely to present in the limbs; however, this is not a well-established fact.25

23.4 Radiology Magnetic resonance imaging (MRI) is the dominant modality for workup of soft-tissue lesions including

MPNST. Metabolic characterization of soft-tissue lesions with 18F fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) is performed to detect malignancy and metastases. Other imaging modalities such as CT and ultrasound (US) may be performed to identify soft-tissue lesions; however, they do not offer the same degree of lesion characterization compared to MRI and PET/CT.

23.4.1 Magnetic Resonance Imaging MRI is the imaging modality of choice for soft-tissue lesions because of its superior soft-tissue contrast. On MRI, MPNSTs are typically spindle-shaped, large tumors, longitudinally oriented along the distribution of a known peripheral nerve with intratumoral lobulation and poorly defined borders.28,29,30 With respect to signal intensity,

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Malignant Peripheral Nerve Sheath Tumors MPNSTs are typically hypointense on T1-weighted sequences, hyperintense on T2-weighted sequences, and peripherally enhance with contrast, although hemorrhagic tumors can demonstrate mixed signal in these sequences (▶ Fig. 23.2 and ▶ Fig. 23.3).28 MPNSTs do not

exhibit the “target sign” seen in benign neurofibromas.28,31 Other imaging findings concerning malignancy include large size,28,30,32 eccentricity to the nerve,28 intratumoral lobulation,28,33 peritumoral edema,28,34,35 irregular margins,28,35 and peripheral enhancement.28 MRI is not able to

Fig. 23.2 Positron emission tomography (PET)/computed tomography (CT) and magnetic resonance imaging (MRI) appearance of malignant peripheral nerve sheath tumor (MPNST). A 42-year-old male with NF1 with a large left buttock MPNST. (a) Low-dose CT images revealed a large complex mass in the left buttocks measuring up to 15 cm with a hypodense center suggestive of central necrosis. (b) Axial PET/CT fused images demonstrate increased peripheral fluorodeoxyglucose (FDG) uptake in the lesion in keeping with viable tumor. There is no FDG uptake in the central hypodense regions in keeping with central necrosis. (c) Sagittal PET/CT fused image. (d) T2-weighted MRI demonstrates the heterogeneous appearance of the large left buttock MPNST. (e) Postcontrast T1 fat-saturated image demonstrates peripheral irregular enhancement corresponding to the viable FDG-avid regions with central nonenhancing necrotic region.

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Malignant Peripheral Nerve Sheath Tumors

Fig. 23.3 Magnetic resonance imaging appearance of a right thigh malignant peripheral nerve sheath tumor with rhabdomyosarcoma, a “triton tumor,” in a 33-year-old female with neurofibromatosis type 1. (a) Sagittal short tau inversion recovery (STIR) sequence demonstrates a large heterogeneous predominantly hyperintense lesion corresponding to the expected location of the sciatic nerve in the lower thigh. Peritumoral edema is seen at the proximal aspect of the lesion (white arrowhead). There is subcutaneous soft-tissue edema in the lower thigh as well. (b) Sagittal T1 sequence demonstrates a predominantly hypointense lesion with areas of heterogeneity likely reflecting blood products/ necrotic debris. A “tail sign” is seen at the proximal aspect of the lesion representing continuity with the sciatic nerve (white arrow).

accurately grade tumors. One large series reported a 62.5 to 81.3% sensitivity and 94.1 to 100% specificity for MRI to accurately differentiate malignant from benign nerve sheath tumors;35 however, another large series found that MRI was discordant from the final pathology in 51% of patients, albeit in that series approximately half of the MRI studies were inconclusive.30

23.4.2 Positron Emission Tomography/Computed Tomography Much recent work has focused on determining the utility of PET/CT in diagnosing malignancy as MPNSTs demonstrate increased FDG uptake (▶ Fig. 23.2). Several groups have reported that the maximum standardized uptake value (SUVmax) is significantly higher in MPNSTs versus benign tumors,36,37,38,39 although the cut-off values were highly variable and included false-positives. Many clinicians choose a SUV threshold of 2.5 to select patients for close follow-up and a value of 3.5 to recommend biopsy.40 Some groups have advocated using the tumor/liver (T/L) SUVmax41 or SUVmax/LiverSUVmean35 ratios for increased specificity and sensitivity. MPNSTs have also been shown to have higher total lesion glycolysis (TLG), and metabolic tumor volume (MTV) compared to benign tumors—a

combination of these factors resulted in 90 to 100% sensitivity and 52.2 to 82.6% specificity for MPNST in one study, leading the authors to conclude that PET/CT and MRI are complementary approaches.35 PET/CT is helpful for identifying lesions to biopsy in patients with multiple tumors, correctly predicting 17 out of 18 tumors as malignant in one series.41 Lastly, PET/CT has been shown to be valuable in staging of patients with MPNST (upstaging or downstaging patients from conventional imaging), surveillance for recurrence, and also prognosis. Patients who have decreasing SUVmax > 30%, TLG, and MTV had significantly higher rates of overall survival in one study from MD Anderson.42

23.4.3 Computed Tomography MPNSTs appear as isodense solid or heterogeneous complex masses on CT (▶ Fig. 23.2 and ▶ Fig. 23.4). If contrast is administered, the solid components will enhance and may be heterogeneous, reflecting intrinsic tumor heterogeneity or necrosis. This CT appearance is nonspecific and either further imaging (MRI and/or PET) or tissue sampling is required. Once a diagnosis of MPNST is obtained, CT of the chest without intravenous contrast is the current American College of Radiology recommended study to assess for pulmonary metastases.43

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Malignant Peripheral Nerve Sheath Tumors

Fig. 23.4 Ultrasound and magnetic resonance imaging (MRI) appearance of an axillary malignant peripheral nerve sheath tumor (MPNST). A 38-year-old female presented with a left axillary mass and targeted ultrasound of the left axillary lesion was performed. Gray scale (a) and Doppler (b) ultrasound demonstrate a mildly heterogeneous hypoechoic circumscribed lesion with minimal internal vascularity. Subsequent ultrasound-guided biopsy revealed an MPNST. MRI of the axillary lesion was performed and STIR (short tau inversion recovery; [c]) sequence demonstrates an oval heterogeneous axillary lesion. Postcontrast T1 fat-saturation sequence (d) demonstrates heterogeneous peripheral-dominant enhancement with central nonenhancing cystic and/or necrotic areas.

23.4.4 Ultrasound US is most commonly used to guide biopsies of suspected MPNST. On US imaging, MPNST can appear as fusiform, heterogeneous hypoechoic lesions, sometimes with cystlike regions (▶ Fig. 23.4).31,44 Although there are no definitive sonographic criteria for malignancy, the “string” or “tail” sign—as with MRI—is suggestive of a peripheral nerve sheath tumor when continuity of the mass is seen with a peripheral nerve.45 Internal vascularity can sometimes be seen in the solid components on Doppler imaging, as is typical of solid tumors.

23.5 Pathology A sarcoma is defined as an MPNST if the tumor arises from a peripheral nerve, or arises from a pre-existing nerve sheath tumor (neurofibroma). In patients with NF1, the diagnosis of MPNST is often straightforward as tumors typically arise from pre-existing plexiform neurofibromas, but this is not always clear for sporadic and radiation-induced cases. Because of the diverse morphologic features, and the lack of specific histologic features of peripheral nerve sheath differentiation in sporadic tumors, demonstration of immunohistochemical or ultrastructural features that suggest Schwann cell or peripheral nerve sheath differentiation are required for the diagnosis.8 Nevertheless, differentiating these MPNSTs

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from other soft-tissue sarcomas can be challenging. The WHO/Fédération Nationale des Centres de Lutte Contrele Cancer (FNCLCC) grading system is used to classify tumors as low or high grade (▶ Table 23.1).

Table 23.1 Grading schema for malignant peripheral nerve sheath tumor (World Health Organization [WHO]/French Federation of Cancer Centers Sarcoma Group [FLNCC]) Tumor differentiation Score 1: sarcomas closely resembling normal adult mesenchymal tissue Score 2: sarcomas for which histological typing is certain Score 3: Embryonal and undifferentiated sarcomas, sarcomas of doubtful type, synovial sarcomas, osteosarcomas, primitive neuroectodermal tumor (PNET)

Histological grade Grade 1: total score 2–3 Grade 2: total score 4–5 Grade 3: total score 6–8

Mitotic count Score 1: 0–9 mitoses per 10 HPFa Score 2: 10–19 mitoses per 10 HPF Score 3: > 20 mitoses per 10 HPF Tumor necrosis Score 0: no necrosis Score 1: less than 50% tumor necrosis Score 2: greater than 50% tumor necrosis Source: Data from Jo and Fletcher.1 aHPF: high power field, measures 0.1734 mm2.

Malignant Peripheral Nerve Sheath Tumors

23.5.1 Gross Examination MPNSTs are fusiform, fleshy, tannish white masses that usually cause thickening of the parent nerve (▶ Fig. 23.5a). On cut section, areas of necrosis and hemorrhage may be seen, as well as fibrous and firm regions, depending on grade (▶ Fig. 23.5b). MPNSTs typically have a pseudocapsule in contrast to benign nerve sheath tumors that are fully encapsulated.46

23.5.2 Microscopic Examination Hematoxylin and eosin (H&E) section is standard for MPNST evaluation (▶ Fig. 23.6). Cells are spindle-shaped and arranged in a whorling and/or fascicular pattern with irregular “buckled” nuclei and variable nuclear palisading, similar to fibrosarcoma (▶ Fig. 23.6a). Variable degree of nuclear pleomorphism is commonly seen. Geographic necrosis with perivascular preservation are typically present in high-grade tumors (▶ Fig. 23.6b).8 Mitotic figures and atypical mitotic forms are seen. In addition, under low magnification, regions of dense cellular fascicles

interdigitate with myxoid areas resulting in a “marbled” appearance. Extensive perineural and intraneural spread as well as other evidence of local invasion must be present. Focal area of lower grade lesion or neurofibroma is commonly seen in tumors arising in NF1 patients.

23.5.3 Immunohistochemistry S-100 protein, a marker for mature Schwann cells, is frequently present, although some studies report that as many as 50% of tumors lack S-100 due to dedifferentiation.47 Additionally, S-100 is a very nonspecific marker that is also highly expressed in melanomas and clear cell sarcomas and variably in other tumors. Therefore, the absence or presence of S-100 expression itself is not sufficient to make a diagnosis or exclude the diagnosis. Other markers of neurogenic origin include Sox10, Leu-7, and myelin basic protein.48 Similarly, none of these markers are specific for MPNST. Once a nerve sheath origin has been established, markers for cellular proliferation can be analyzed to assess for grade and malignancy.20 Ki-67, p53, VEGF,

Fig. 23.5 Gross appearance of malignant peripheral nerve sheath tumor (MPNST). (a) Excised MPNST from femoral nerve. (b) Cut gross specimen. Note grayish, fleshy appearance and regions of necrosis.

Fig. 23.6 Hematoxylin and eosin (H&E) staining of various malignant peripheral nerve sheath tumor (MPNST) subtypes. (a) Typical appearance of MPNST with spindle-shaped cells arranged in whorling and fascicular patterns at × 10 magnification. (b) Areas of geographic necrosis in a typical MPNST at × 5 magnification. (c) Epithelioid MPNST. Note the large, polygonal cells with central nuclei and prominent nucleoli at × 10 magnification. (d) Malignant triton tumor at × 20 magnification. Note the striated cells that appear similar to muscle fibers.

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Malignant Peripheral Nerve Sheath Tumors pMEK, and MIB-1 staining are all reported to be significantly higher in MPNST compared to benign nerve tumors.24,49 A greater than 5% staining with MIB-1 (Ki-67) was reported in a high-grade tumor,49,50 while greater than 25% was associated with significantly lower survival in one study.51 Increased p53 labeling or decreased S-100 labeling was also associated with poor prognosis on multivariate analysis in another study.24 Lack of Ini1 (SMARCB1) expression is seen in a subset of MPNST.52

expression profile of downregulation of SOX10, CNP, PMP22, and NGFR (markers of Schwann cell differentiation) and overexpression of SOX9 and TWIST1 (markers of neural crest stem cells). It is not known whether the pathogenesis of sporadic, RT-induced, or NF1-associated MPNSTs are distinct.

23.5.4 Pathologic Subtypes of MPNST

Patients presenting with suspected MPNST should undergo a thorough history and physical examination. Particular attention should be paid to a family history of NF1, or other tumor syndromes. Skin findings consistent with NF1 should be documented, and the patient and his or her family should be referred to genetic counseling if diagnostic criteria are met. The utility of core needle biopsies in workup of MPNST is debated. Because resection of MPNST may require sacrifice of functional nerve, some surgeons advocate for needle biopsies prior to definitive surgery. However, sampling error may lead to underdiagnosis, and tumor cells may be spread along the needle trajectory, leading other surgeons to prefer open biopsy or initial radical resection if suspicion for MPNST is high. A third approach is a staged procedure in which an initial resection is undertaken while preserving the tumor capsule. If malignancy is seen on final pathology, the patient is returned to the operating room in short order for definitive resection.20 Once the diagnosis of MPNST has been established, accurate staging is essential for directing treatment. The American Joint Committee on Cancer (AJCC) staging criteria have been used to study MPNST (▶ Table 23.2).

Epithelioid MPNSTs are composed of large polygonal cells with central nuclei and prominent nucleoli (▶ Fig. 23.6c). They typically demonstrate high levels of S-100 staining, and are not observed in association with NF1.53 A subset of these tumors lack INI expression.52 Malignant triton tumors are MPNSTs that express mesenchymal differentiation with rhabdomyoblastoma components embedded in the tumor (▶ Fig. 23.6d). They are reactive with Desmin, Myoginen, and MyoD1 markers, frequently associated with NF1, and carry a poor prognosis.54 Chondrosarcomatous and osteosarcomatous elements may also be present. Glandular MPNSTs are tumors that contain welldifferentiated glands. Cells are cuboidal or columnar and may contain mucin. Glandular MPNSTs are strongly associated with NF1 and also carry a poor prognosis.55

23.6 Pathogenesis and Cancer Genetics Mutations in the NF1 gene and subsequent hyperactivation of Ras-mediated signaling pathways regulating proliferation, migration, and survival are thought to be the initiating event in MPNST tumorigenesis.22 In patients with NF1, at least one allele is inactivated, but the loss of the second copy of NF1 is sufficient to cause plexiform neurofibroma and is always seen in MPNST. This is not sufficient to cause malignant transformation—multiple other genetic alterations must accumulate including mutations in the p16, p19, p53, and retinoblastoma (Rb) pathways.56 Numerical or structural aberrations of chromosomes 1 and 12 are frequently seen in MPNST, but the downstream effects of these changes are unknown.56 Germline analysis of NF1 patients has revealed a 1.5-Mb microdeletion in the NF1 gene, which is present in 5 to 10% of individuals and leads to a greater number of neurofibromas at an early age, lower mean IQ, and substantially higher risk for the development of MPNST.57 Gene expression data identified upregulation of MMP13, PDGFRα, and fibronectin in an MPNST compared to a plexiform neurofibroma from the same patient.58 Further studies using many tumor specimens have uncovered an

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23.7 Workup and Evaluation

23.8 Treatment Surgical resection remains the mainstay of treatment for MPNST. Despite many advances in the field of medicine at large, current adjuvant treatments for MPNST have failed to significantly improve survival, and they are not standardized or studied systematically. There is a great need for finding an effective therapy target for MPNST.

23.9 Surgery Similar to other soft-tissue sarcomas, surgery is the primary curative modality for MPNT. The goal of resection is gross total removal of the tumor with histologically negative margins. Surgical results are graded according to the Intergroup Rhabdomyosarcoma Study (IRS) group criteria59 (▶ Table 23.3a) or on a scale from R0 to R2 (▶ Table 23.3b). The likelihood of R0 resection or gross total resection (GTR) depends on the location of the tumor and varies from 95% in the extremities to 20% in the paraspinal region.60 When peripheral nerves in the extremities are involved, GTR can typically be accomplished with a

Malignant Peripheral Nerve Sheath Tumors Table 23.2 Grading of malignant peripheral nerve sheath tumors American Joint Committee on Cancer (AJCC) system Primary tumor (T) ● TX: primary tumor cannot be assessed ● T0: no evidence of primary tumor ● T1: tumor 5 cm or less in greatest dimension ○ T1a: superficial tumor ○ T1b: deep tumor ● T2: tumor more than 5 cm in greatest dimension ○ T2a: superficial tumor ○ T2b: deep tumor

Stage grouping Stage I

T1a,1b,2a,2b

N0

M0

G1

Stage II

T1a,1b,2a

N0

M0

G2–3

Stage III

T2b

N0

M0

G2–3

Stage IV

Any T

N1

M0

Any G

Any T

N0

M1

Any G

Regional lymph nodes (N) NX regional lymph nodes cannot be assessed N0 no regional lymph node metastasis N1a regional lymph node metastasis Distant metastasis (M) MX distant metastasis cannot be assessed M0 no distant metastasis M1 distant metastasis Histologic grade (G) GX grade cannot be assessed G1 well differentiated G2 moderated differentiated G3 poorly differentiated G4 poorly differentiated or undifferentiated (four-tiered systems only) Source: Data from American Joint Committee on Cancer. aPresence of positive nodes (N1) is considered Stage IV.

Table 23.3 Resection grading for malignant peripheral nerve sheath tumors (a) Intergroup Rhabdomyosarcoma Study (IRS) group Group

Extent of disease

Group I

Localized disease, excised

○ Group Ia

Confined to site of origin

○ Group Ib

Infiltrative, beyond site of origin; negative lymph nodes

Group II

Total gross resection with regional disease spread

○ Group IIa

Localized tumor with microscopic residual disease

○ Group IIb

●

●

○ Group IIc

● ●

Regional disease with positive lymph nodes, excised No microscopic residual disease Regional disease with positive lymph nodes Grossly resected with microscopic residual disease

Group III

Gross residual disease

○ Group IIIa

Localized or regional disease, Biopsy

○ Group IIIb

Localized or regional disease, resection (debulking of more than 50% of tumor)

Group IV

Distant metastasis

(b) R system R0

Microscopic tumor free margins

R1

Microscopic tumor at margins

R2

Macroscopically incomplete

Source: Data from Maurer et al.59

limb-sparing approach. Rates of amputation range from 7.4 to 10%, usually occurring at a secondary salvage operation in the context of tumor recurrence or to obtain negative surgical margins.4,6,12,16 Wide resection of MPNST is usually accomplished by en bloc excision of the tumor along with its parent nerve. This can result in significant functional loss, which is difficult to predict, particularly if the tumor originates in the brachial or lumbosacral plexus.61,62 Patients should be counseled regarding loss of function prior to surgery, and both surgeon and patient should confirm acceptance of potential disability. Nerve grafting is not routinely recommended following surgery for MPNST. The proximal nerve is typically not amenable to grafting and the natural history of the disease often does not allow sufficient time for successful reinnervation to occur, although there are exceptions.63

23.9.1 Chemotherapy Due to the rarity of MPNST, data regarding the utility of chemotherapy are limited; there are no phase II or phase III trials specifically addressing MPNST. Many chemotherapy regimens for MPNST are extrapolated from experience in soft-tissues sarcomas. Doxorubicin alone or in combination with ifosfamide comprises first-line therapy in large, unresectable or metastatic MPNST, and has demonstrated the most activity against MPNST.64,65 Second-line therapy is poorly defined and includes a

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Malignant Peripheral Nerve Sheath Tumors combination of cyclophosphamide, vincristine, Adriamycin, and dacarbazine (CYADIC), Gemcitabine/Docetaxel, or Carboplatin/Etoposide.22,64 Only a minority of patients receive chemotherapy. In single institution series, 6 to 50% of patients were treated with chemotherapy with the majority of trials reporting less than a quarter of patients treated.11,12,13,14,15,16,24,25,66,67 Outcomes for chemotherapy alone are rarely systematically reported, but they appear to be favorable in children and young adults.10,68 In one large pediatric series of patients treated between 1975 and 1998, an overall response rate of 45% was observed with neoadjuvant chemotherapy, with 11 patients whose disease was rendered resectable following treatment.10 NF1 patients had significantly lower response rates than patients with spontaneous MPNST (17.5 vs. 55.3%), and patients who responded to chemotherapy had significantly better 5-year survival than those who did not. In a pooled analysis of 12 European Organization for Research and Treatment of Cancer (EORTC) trials, a response rate of 21% was observed in adults.64 Most experts recommend chemotherapy for high-risk patients with large (> 5 cm), unresectable or metastatic MPNST.22 However, the utility of chemotherapy needs to be further investigated with prospective, histologydriven, multi-institutional trials.

23.9.2 Radiation Therapy Radiation therapy (XRT) has been shown to delay local recurrence in MPNST in a single study, but does not affect rates of overall survival.4,69 In contrast to chemotherapy, nearly half of patients receive some form of XRT alone, or in conjunction with surgery, with doses ranging from 12.5 to 90 Gy.4,5,12,13,14,24,25,69 Several modalities of radiation have been described, from intraoperative radiation to brachytherapy implanted at the time of surgery, to conventional postoperative external beam therapy or proton therapy. Similar to chemotherapy for MPNST, little data exist to support the use of XRT. Nevertheless, it is recommended by the Oncology Consensus Group policy for uniform treatment of MPNST, and should certainly be considered in the case of incomplete resection.70 In patients with NF1, XRT must be administered cautiously because of the known propensity to trigger malignant transformation in neurofibromas within the radiation field.

23.9.3 Neoadjuvant Therapy The optimal timing of chemotherapy and radiation therapy is not well studied. With respect to chemotherapy, there are reports of reduction of tumor burden by neoadjuvant therapy such that GTR was able to be accomplished in 11 children, and histologic complete response in a single adult patient with advanced MPNST.10,71 With

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respect to radiation therapy, neoadjuvant treatment is recommended if the location, size, and distribution of tumor makes a GTR unlikely (e.g., along a major neurovascular bundle), or if remote tissue flaps or skin grafts are anticipated for wound healing after surgery.20

23.10 Prognosis MPNSTs behave aggressively and have poor survival rates. Tumor cells readily invade fascial planes, which results in frequent local recurrence as well as metastases.72,73 Overall survival has not increased over time, likely due to the lack of effective adjuvant therapies.

23.10.1 Overall Survival In large clinical series with greater than 100 patients, approximately half of all patients with MPNST are alive at 5 years and one-third of patients are alive at 10 years after diagnosis (▶ Table 23.4). Many groups have attempted to identify negative prognostic factors; however, their findings are often conflicting, perhaps due to the retrospective nature of studies and the inherent heterogeneity of patients and tumors (▶ Table 23.4). In particular, the prognostic value of NF1 status has been widely debated. Several studies have found no relationship between NF1 and survival, including a meta-analysis of over 1,800 patients,11,13,14,15,24 whereas other large series have found decreased survival in patients with NF1.4,5,10,12,16,67 Two groups have observed improved survival over time for NF1 patients (25% at 5 years between 1980 and 1996 vs. 55% between 1997 and 2010), suggesting that the discrepancy may be due to distinct observational periods.13,74 On multivariate analysis, higher grade, larger tumors, and positive margins are consistently associated with decreased survival.4,10,12,14,15,16,24,25

23.10.2 Disease Free Survival, Local and Distant Recurrence MPNSTs very often recur both at the site of resection and at locations distant from the primary tumor (▶ Table 23.4). Local recurrence rates range from 27 to 53%,4,14 and occur at a median of 8 to 11 months following surgery.10,24 Tumors can recur in as many as 66% of patients after GTR,14 even after amputation.15 These are among the highest recurrence rates seen in soft-tissue sarcomas.75 Metastatic disease is the principal cause of mortality in patients with MPNST. Metastases most commonly present in the lungs (30–67%), followed by lymph nodes, brain, liver, and bone in no particular order.4,5,10,11,12,15,24 Uncommon sites of metastasis include the adrenals, kidneys, diaphragm, and other sites in the abdomen and retroperitoneum.5,12,24 Risk factors for metastasis include large primary tumor size, higher tumor

Table 23.4 Overall survival at 5 and 10 years after diagnosis, rates of recurrence and prognostic factors in case series reporting greater than 100 patients n

Time period

institutions

%NF1

% RT

5-year survival %

10-year survival %

% local recurrence

Mean or median time to recurrence (months)

% metastatic recurrence

Mean or Median time to metastasis (months)

UV negative prognostic factures

MV negative prognostic factors

Ducatman et al., 19865

120

1912– 1983

Mayo Clinic

52

11

OS 34, NF1 16, S 53

OS 22, NF1 19, S 38

NF1 45, S 38

Means NF1 13.3, S 32.2

NF1 24, S 16

NF1 19.3, S 75.1

NF1, tumor size > 5 cm, extent of resection, location not in extremities

NR

Wong et al., 19984

134

1975– 1993

Mayo Clinic

24

10

OS 52

OS 34

53, worse in post-rad MPNST

Median 10

40

Median 20.6

Larger tumor size, location not in extremities, NF1, + margin, radiation, high grade, mitotic rate > 6, presence of necrosis, use of brachytherapy

prior XRT, positive margins

Carli et al., 200510

167 pediatric

1975– 1998

Multiple in Germany, Italy

17

NR

OS 51.1

OS 43.4

51

Median 11

14

Median 16

STR, tumor invasiveness, size > 5 cm, NF1, location not in extremity, age > 1

STR, size > 5 cm, tumor invasiveness, NF1, location not in extremity

Anghileri et al., 200611

205

1976– 2003

Instituto Nazionale per lo Studio de la Cura dei Tumor, Milan, Italy

22.4

NR

OS 60.1, RT 54.8, NF1 56.1, S 61.1

OS 56.7, RT 50.8, NF1 45.6, S 60.2

27.3 5-yr, 28.8 10-yr

NR

26.2 at 5-yr, 28.7 at 10-yr

Median 13

Tumor size > 4 cm, location not in extremity, recurrent presentation

NR

Zou et al., 200924

140

1986– 2006

MD Anderson Cancer Center

51.4

15

OS 38.7 RT 47.3, NF1 34.8, S 42.3

OS 26.4, RT 25.9, NF1 23.8, S 28.5

36

Median 8

41

Median 12

tumor > 10 cm, negative S100 stain gin

tumor > 10 cm, negative S100 stain gin

Stucky et al., 201112

175

1985– 2010

Mayo Clinic

32

10

OS 60, NF1 54, S 75

OS 54

37

NR

65

NR

NF1, tumor > 5 cm, high grade tumors, chemo, local recurrence

high grade, size > 5 cm, truncal location, local recurrence

Porter et al 200925

123

1979– 2002

3 sites in England

27

NR

OS 51, NF1 32, S 60

NR

GTR 6, STR 30

NR

NR

NR

Sciatic plexus, volume > 200,

Volume > 200, NF1

Kolberg et al., 201313

179

1970– 2011

Norway, Sweden, Italy

35

NR

OS 46, NF1 45, S 47

NR

NR

NR

NR

NR

high grade, larger size, metastatic disease, not in remission

205

(continued)

Malignant Peripheral Nerve Sheath Tumors

Authors, year

206 Authors, year

n

Time period

institutions

%NF1

% RT

5-year survival %

10-year survival %

% local recurrence

Mean or median time to recurrence (months)

% metastatic recurrence

Mean or Median time to metastasis (months)

UV negative prognostic factures

MV negative prognostic factors

LaFemina et al., 201314

105

1982– 2011

Memorial Sloan Kettering Cancer Center

40

13

NR

NR

27.6 at 3 yr, 66% with GTR

NR

34 at 3-yr

NR

larger size, + margins

larger size (> 10 cm), + margins

Fan, Yang, Wang 201467

146

TianJin, China

11.6

NR

OS 57

O 51

48.6

NR

26

NR

NF1, tumor size, increase staging, surgery, + P53 and MDM2 staining

none for either PFS or OS

Valentin et al., 201516

353

1990– 2013

12 sites in France

39

3.6

OS 59.4

NR

NR

NR

NR

NR

NF1, not in extremity, deep, high grade, locally advanced, STR, no XRT

deep tumor, grade III, locally advanced, STR

Watson et al., 201615

1 28/289

1990– 2014

MD Anderson Cancer Center

51

9

OS 52

OS 42

37, 3 pts after amp

Median 12

47

Median 16

RT tumor, no XRT, male sex, nonepitheliod or triton tumor, deep location, chemo, tumor > 10 cm

tumor > 10 cm, + margins, truncal location, + margins, local recurrence and metastases

Abbreviations: DSS, disease specific survival; GTR, gross total resection; MV, multivariate; NF1, neurofibromatosis-1 associated; NR, not reported; OS, overall survival; PFS, progression free survival; RT, radiation induced; S, sporadic; STS, subtotal resection; UV, univariate; yr, years.

Malignant Peripheral Nerve Sheath Tumors

Table 23.4 (continued) Overall survival at 5 and 10 years after diagnosis, rates of recurrence and prognostic factors in case series reporting greater than 100 patients

Malignant Peripheral Nerve Sheath Tumors grade, and positive margins.11,12,24 Two histologic features have been associated with development of metastatic disease—perineurial type tumors and negative staining for S100—but these have not been broadly validated.4,24

23.10.3 Low-Grade MPNST Low-grade MPNSTs (WHO I) are an uncommon subcategory of MPNST, comprising only 3.8% of all MPNST in one large series.15 Their behavior is distinct from high-grade MPNST, and they have much better overall survival as well as progression free survival in small single institution case series. In the largest published cohort of 23 patients, no patients died from their tumor with a median follow-up of 47 months.76 Furthermore, local recurrence only occurred in 3 patients, despite microscopically positive margins in 18 patients. In all reported low-grade MPNST patients to date, no metastases were observed even at long follow-up intervals.15,50 Given these results, low-grade MPNSTs appear to have an indolent course and may be treated more conservatively, sparing patients debilitating or disfiguring operations. Adjuvant therapy is generally not indicated.

23.10.4 Pediatric MPNST Survival for pediatric patients with MPNST is also poor. The largest pediatric series to date reported a 5-year overall survival of 51% and a 10-year overall survival of 37% for 167 children treated between 1975 and 1998 in Europe.10 Progression free survival was 37.2% at 5 years and 34.5% at 10 years, with a median time to recurrence of 11 months. Multivariate analysis identified tumor size greater than 5 cm, International Rhabdomyosarcoma Study group resection grade of III or IV, tumor invasiveness, presence of NF1, and truncal location to be negative prognostic factors. Interestingly, in this cohort, patients with NF1 were less likely to respond to chemotherapy. In a 156-patient SEER data-based study, median overall survival was 50 months, with localized disease and surgery identified as positive prognostic factors in multivariate analysis,9 thereby reinforcing the tenet that surgical resection is the preferred treatment modality, and that early detection is crucial to improved survival.

23.10.5 Postradiation MPNST Radiation (RT) induced MPNSTs comprise a minority of tumors (3.6–10% in large series4,5,12,14,15,16,24); thus, the experience in patients with these tumors is limited. In two studies, RT-induced MPNSTs had lower overall survival compared to NF1 or sporadic tumors (49% RT vs. 60% NF1 vs. 66% sporadic at 3 years), and was found on univariate analysis to be associated with poor prognosis.4,14 RT-induced tumors behaved more aggressively and were more likely to recur locally.14 This may be due to a combi-

nation of factors: difficult location of tumor limiting complete excision, suboptimal adjuvant radiation therapy due to previous radiation exposure, and tumor biology. In another large series, history of radiation exposure was not found to be a negative prognostic factor.24

23.11 Conclusion MPNSTs are rare, aggressive, soft-tissue sarcomas that have poor prognoses, with approximately 50% of patients surviving at 5 years after diagnosis. Risk factors include NF1 syndrome and prior radiation exposure. MRI and PET/CT are the mainstay of imaging diagnosis. Surgery remains the only curative treatment modality. Early diagnosis and screening in patients at high risk for MPNST is therefore critical.

References [1] Jo VY, Fletcher CD. WHO classification of soft tissue tumours: an update based on the 2013 (4th) edition. Pathology. 2014; 46(2):95– 104 [2] Stout AP. The peripheral manifestation of the specific nerve sheath tumor (neurilemoma). Am Cancer. 1935; 24:751–796 [3] Murray MR, Stout AP, Bradley CF. Schwann cell versus fibroblast as the origin of the specific nerve sheath tumor: Observations upon normal nerve sheaths and neurilemomas in vitro. Am J Pathol. 1940; 16(1):41–60, 17 [4] Wong WW, Hirose T, Scheithauer BW, Schild SE, Gunderson LL. Malignant peripheral nerve sheath tumor: analysis of treatment outcome. Int J Radiat Oncol Biol Phys. 1998; 42(2):351–360 [5] Ducatman BS, Scheithauer BW, Piepgras DG, Reiman HM, Ilstrup DM. Malignant peripheral nerve sheath tumors. A clinicopathologic study of 120 cases. Cancer. 1986; 57(10):2006–2021 [6] Vauthey JN, Woodruff JM, Brennan MF. Extremity malignant peripheral nerve sheath tumors (neurogenic sarcomas): a 10-year experience. Ann Surg Oncol. 1995; 2(2):126–131 [7] Lewis JJ, Leung D, Woodruff JM, Brennan MF. Retroperitoneal softtissue sarcoma: analysis of 500 patients treated and followed at a single institution. Ann Surg. 1998; 228(3):355–365 [8] Weiss SW, Goldblum JR. Enzinger and Weiss’s Soft Tissue Tumors. St. Louis, MO: Mosby, Inc.; 2001 [9] Bates JE, Peterson CR, Dhakal S, Giampoli EJ, Constine LS. Malignant peripheral nerve sheath tumors (MPNST): a SEER analysis of incidence across the age spectrum and therapeutic interventions in the pediatric population. Pediatr Blood Cancer. 2014; 61(11):1955–1960 [10] Carli M, Ferrari A, Mattke A, et al. Pediatric malignant peripheral nerve sheath tumor: the Italian and German soft tissue sarcoma cooperative group. J Clin Oncol. 2005; 23(33):8422–8430 [11] Anghileri M, Miceli R, Fiore M, et al. Malignant peripheral nerve sheath tumors: prognostic factors and survival in a series of patients treated at a single institution. Cancer. 2006; 107(5):1065–1074 [12] Stucky CC, Johnson KN, Gray RJ, et al. Malignant peripheral nerve sheath tumors (MPNST): the Mayo Clinic experience. Ann Surg Oncol. 2012; 19(3):878–885 [13] Kolberg M, Høland M, Agesen TH, et al. Survival meta-analyses for > 1800 malignant peripheral nerve sheath tumor patients with and without neurofibromatosis type 1. Neuro-oncol. 2013; 15(2): 135–147 [14] LaFemina J, Qin LX, Moraco NH, et al. Oncologic outcomes of sporadic, neurofibromatosis-associated, and radiation-induced malignant peripheral nerve sheath tumors. Ann Surg Oncol. 2013; 20(1):66–72 [15] Watson KL, Al Sannaa GA, Kivlin CM, et al. Patterns of recurrence and survival in sporadic, neurofibromatosis Type 1-associated, and

207

Manual of Peripheral Nerve Surgery | 25.07.17 - 10:03

Malignant Peripheral Nerve Sheath Tumors

[16]

[17]

[18] [19] [20] [21]

[22]

[23]

[24]

[25]

[26]

[27]

[28]

[29]

[30]

[31]

[32]

[33]

[34]

[35]

[36]

208

radiation-associated malignant peripheral nerve sheath tumors. J Neurosurg. 2016; 126(1):1–11 Valentin T, Le Cesne A, Ray-Coquard I, et al. Management and prognosis of malignant peripheral nerve sheath tumors: The experience of the French Sarcoma Group (GSF-GETO). Eur J Cancer. 2016; 56:77–84 Amirian ES, Goodman JC, New P, Scheurer ME. Pediatric and adult malignant peripheral nerve sheath tumors: an analysis of data from the surveillance, epidemiology, and end results program. J Neurooncol. 2014; 116(3):609–616 Neville H, Corpron C, Blakely ML, Andrassy R. Pediatric neurofibrosarcoma. J Pediatr Surg. 2003; 38(3):343–346, discussion 343–346 von Recklinghausen F. Uber die multiplen Fibrome der Haut und ihre Beziehung zu den multiple Neuromen. Berlin: Hirschwald; 1882:138 Gupta G, Maniker A. Malignant peripheral nerve sheath tumors. Neurosurg Focus. 2007; 22(6):E12 Tucker T, Wolkenstein P, Revuz J, Zeller J, Friedman JM. Association between benign and malignant peripheral nerve sheath tumors in NF1. Neurology. 2005; 65(2):205–211 Grobmyer SR, Reith JD, Shahlaee A, Bush CH, Hochwald SN. Malignant peripheral nerve sheath tumor: molecular pathogenesis and current management considerations. J Surg Oncol. 2008; 97(4):340–349 Cashen DV, Parisien RC, Raskin K, Hornicek FJ, Gebhardt MC, Mankin HJ. Survival data for patients with malignant schwannoma. Clin Orthop Relat Res. 2004(426):69–73 Zou C, Smith KD, Liu J, et al. Clinical, pathological, and molecular variables predictive of malignant peripheral nerve sheath tumor outcome. Ann Surg. 2009; 249(6):1014–1022 Porter DE, Prasad V, Foster L, Dall GF, Birch R, Grimer RJ. Survival in malignant peripheral nerve sheath tumours: a comparison between sporadic and neurofibromatosis type 1-associated tumours. Sarcoma. 2009; 2009:756395 Foley KM, Woodruff JM, Ellis FT, Posner JB. Radiation-induced malignant and atypical peripheral nerve sheath tumors. Ann Neurol. 1980; 7(4):311–318 McGaughran JM, Harris DI, Donnai D, et al. A clinical study of type 1 neurofibromatosis in north west England. J Med Genet. 1999; 36(3): 197–203 Yu YH, Wu JT, Ye J, Chen MX. Radiological findings of malignant peripheral nerve sheath tumor: reports of six cases and review of literature. World J Surg Oncol. 2016; 14:142 Zhang Z, Deng L, Ding L, Meng Q. MR imaging differentiation of malignant soft tissue tumors from peripheral schwannomas with large size and heterogeneous signal intensity. Eur J Radiol. 2015; 84 (5):940–946 Karsy M, Guan J, Ravindra VM, Stilwill S, Mahan MA. Diagnostic quality of magnetic resonance imaging interpretation for peripheral nerve sheath tumors: can malignancy be determined? J Neurol Surg A Cent Eur Neurosurg. 2016; 77(6):495–504 Iannicelli E, Rossi G, Almberger M, et al. Integrated imaging in peripheral nerve lesions in type 1 neurofibromatosis. Radiol Med (Torino). 2002; 103(4):332–343 Mautner VF, Friedrich RE, von Deimling A, et al. Malignant peripheral nerve sheath tumours in neurofibromatosis type 1: MRI supports the diagnosis of malignant plexiform neurofibroma. Neuroradiology. 2003; 45(9):618–625 Van Herendael BH, Heyman SR, Vanhoenacker FM, et al. The value of magnetic resonance imaging in the differentiation between malignant peripheral nerve-sheath tumors and non-neurogenic malignant soft-tissue tumors. Skeletal Radiol. 2006; 35(10):745–753 Pilavaki M, Chourmouzi D, Kiziridou A, Skordalaki A, Zarampoukas T, Drevelengas A. Imaging of peripheral nerve sheath tumors with pathologic correlation: pictorial review. Eur J Radiol. 2004; 52(3): 229–239 Broski SM, Johnson GB, Howe BM, et al. Evaluation of (18)F-FDG PET and MRI in differentiating benign and malignant peripheral nerve sheath tumors. Skeletal Radiol. 2016; 45(8):1097–1105 Benz MR, Czernin J, Dry SM, et al. Quantitative F18-fluorodeoxyglucose positron emission tomography accurately characterizes periph-

[37]

[38]

[39]

[40]

[41]

[42]

[43]

[44]

[45]

[46] [47]

[48]

[49]

[50]

[51]

[52]

[53]

[54]

[55]

eral nerve sheath tumors as malignant or benign. Cancer. 2010; 116 (2):451–458 Ferner RE, Golding JF, Smith M, et al. [18F]2-fluoro-2-deoxy-Dglucose positron emission tomography (FDG PET) as a diagnostic tool for neurofibromatosis 1 (NF1) associated malignant peripheral nerve sheath tumours (MPNSTs): a long-term clinical study. Ann Oncol. 2008; 19(2):390–394 Solomon SB, Semih Dogan A, Nicol TL, Campbell JN, Pomper MG. Positron emission tomography in the detection and management of sarcomatous transformation in neurofibromatosis. Clin Nucl Med. 2001; 26(6):525–528 Cardona S, Schwarzbach M, Hinz U, et al. Evaluation of F18-deoxyglucose positron emission tomography (FDG-PET) to assess the nature of neurogenic tumours. Eur J Surg Oncol. 2003; 29(6):536–541 Urban T, Lim R, Merker VL, et al. Anatomic and metabolic evaluation of peripheral nerve sheath tumors in patients with neurofibromatosis 1 using whole-body MRI and (18)F-FDG PET fusion. Clin Nucl Med. 2014; 39(5):e301–e307 Brahmi M, Thiesse P, Ranchere D, et al. Diagnostic accuracy of PET/ CT-guided percutaneous biopsies for malignant peripheral nerve sheath tumors in neurofibromatosis type 1 patients. PLoS One. 2015; 10(10):e0138386 Khiewvan B, Macapinlac HA, Lev D, et al. The value of 18F-FDG PET/ CT in the management of malignant peripheral nerve sheath tumors. Eur J Nucl Med Mol Imaging. 2014; 41(9):1756–1766 Roberts CC, Kransdorf MJ, Beaman FD, et al. ACR appropriateness criteria follow-up of malignant or aggressive musculoskeletal tumors. J Am Coll Radiol. 2016; 13(4):389–400 Rafailidis V, Kaziani T, Theocharides C, Papanikolaou A, Rafailidis D. Imaging of the malignant peripheral nerve sheath tumour with emphasis on ultrasonography: correlation with MRI. J Ultrasound. 2014; 17(3):219–223 Reynolds DL, Jr, Jacobson JA, Inampudi P, Jamadar DA, Ebrahim FS, Hayes CW. Sonographic characteristics of peripheral nerve sheath tumors. AJR Am J Roentgenol. 2004; 182(3):741–744 Woodruff JM. Pathology of the major peripheral nerve sheath neoplasms. Monogr Pathol. 1996; 38:129–161 Bhattacharyya AK, Perrin R, Guha A. Peripheral nerve tumors: management strategies and molecular insights. J Neurooncol. 2004; 69 (1–3):335–349 Wick MR, Swanson PE, Scheithauer BW, Manivel JC. Malignant peripheral nerve sheath tumor. An immunohistochemical study of 62 cases. Am J Clin Pathol. 1987; 87(4):425–433 Zhou H, Coffin CM, Perkins SL, Tripp SR, Liew M, Viskochil DH. Malignant peripheral nerve sheath tumor: a comparison of grade, immunophenotype, and cell cycle/growth activation marker expression in sporadic and neurofibromatosis 1-related lesions. Am J Surg Pathol. 2003; 27(10):1337–1345 Yamaguchi U, Hasegawa T, Hirose T, et al. Low grade malignant peripheral nerve sheath tumour: varied cytological and histological patterns. J Clin Pathol. 2003; 56(11):826–830 Watanabe T, Oda Y, Tamiya S, Kinukawa N, Masuda K, Tsuneyoshi M. Malignant peripheral nerve sheath tumours: high Ki67 labelling index is the significant prognostic indicator. Histopathology. 2001; 39(2):187–197 Jo VY, Fletcher CD. Epithelioid malignant peripheral nerve sheath tumor: clinicopathologic analysis of 63 cases. Am J Surg Pathol. 2015; 39(5):673–682 Laskin WB, Weiss SW, Bratthauer GL. Epithelioid variant of malignant peripheral nerve sheath tumor (malignant epithelioid schwannoma). Am J Surg Pathol. 1991; 15(12):1136–1145 Stasik CJ, Tawfik O. Malignant peripheral nerve sheath tumor with rhabdomyosarcomatous differentiation (malignant triton tumor). Arch Pathol Lab Med. 2006; 130(12):1878–1881 Galatian AA, Crowson AN, Fischer RJ, Yob EH, Shendrik I. Malignant peripheral nerve sheath tumor with glandular differentiation in a patient with neurofibromatosis type 1. Am J Dermatopathol. 2013; 35(8):859–863

Manual of Peripheral Nerve Surgery | 25.07.17 - 10:03

Malignant Peripheral Nerve Sheath Tumors [56] Carroll SL. The challenge of cancer genomics in rare nervous system neoplasms: malignant peripheral nerve sheath tumors as a paradigm for cross-species comparative oncogenomics. Am J Pathol. 2016; 186 (3):464–477 [57] De Raedt T, Brems H, Wolkenstein P, et al. Elevated risk for MPNST in NF1 microdeletion patients. Am J Hum Genet. 2003; 72(5):1288– 1292 [58] Holtkamp N, Mautner VF, Friedrich RE, et al. Differentially expressed genes in neurofibromatosis 1-associated neurofibromas and malignant peripheral nerve sheath tumors. Acta Neuropathol. 2004; 107 (2):159–168 [59] Maurer HM, Beltangady M, Gehan EA, et al. The Intergroup Rhabdomyosarcoma Study-I. A final report. Cancer. 1988; 61(2):209–220 [60] Baehring JM, Betensky RA, Batchelor TT. Malignant peripheral nerve sheath tumor: the clinical spectrum and outcome of treatment. Neurology. 2003; 61(5):696–698 [61] Rawal A, Yin Q, Roebuck M, et al. Atypical and malignant peripheral nerve-sheath tumors of the brachial plexus: report of three cases and review of the literature. Microsurgery. 2006; 26(2):80–86 [62] Huang JH, Zaghloul K, Zager EL. Surgical management of brachial plexus region tumors. Surg Neurol. 2004; 61(4):372–378 [63] Spiliopoulos K, Williams Z. Brachial plexus reconstruction following resection of a malignant peripheral nerve sheath tumor: case report. Neurosurgery. 2011; 69(1):E245–E250, discussion E250 [64] Kroep JR, Ouali M, Gelderblom H, et al. First-line chemotherapy for malignant peripheral nerve sheath tumor (MPNST) versus other histological soft tissue sarcoma subtypes and as a prognostic factor for MPNST: an EORTC soft tissue and bone sarcoma group study. Ann Oncol. 2011; 22(1):207–214 [65] Clark JW. Chemotherapy for soft tissue sarcomas. Med Health R I. 1997; 80(1):37–38

[66] LaFemina J, Chou JF, Gönen M, et al. Hepatic arterial nodal metastases in pancreatic cancer: is this the node of importance? J Gastrointest Surg. 2013; 17(6):1092–1097 [67] Fan Q, Yang J, Wang G. Clinical and molecular prognostic predictors of malignant peripheral nerve sheath tumor. Clin Transl Oncol. 2014; 16(2):191–199 [68] Sordillo PP, Helson L, Hajdu SI, et al. Malignant schwannoma: clinical characteristics, survival, and response to therapy. Cancer. 1981; 47 (10):2503–2509 [69] Kahn J, Gillespie A, Tsokos M, et al. Radiation therapy in management of sporadic and neurofibromatosis type 1-associated malignant peripheral nerve sheath tumors. Front Oncol. 2014; 4:324 [70] Ferner RE, Gutmann DH. International consensus statement on malignant peripheral nerve sheath tumors in neurofibromatosis. Cancer Res. 2002; 62(5):1573–1577 [71] Masui F, Yokoyama R, Soshi S, Beppu Y, Asanuma K, Fujii K. A malignant peripheral nerve-sheath tumour responding to chemotherapy. J Bone Joint Surg Br. 2004; 86(1):113–115 [72] Angelov L, Davis A, O’Sullivan B, Bell R, Guha A. Neurogenic sarcomas: experience at the University of Toronto. Neurosurgery. 1998; 43(1): 56–64, discussion 64–65 [73] Simon MA, Enneking WF. The management of soft-tissue sarcomas of the extremities. J Bone Joint Surg Am. 1976; 58(3):317–327 [74] Ingham S, Huson SM, Moran A, Wylie J, Leahy M, Evans DG. Malignant peripheral nerve sheath tumours in NF1: improved survival in women and in recent years. Eur J Cancer. 2011; 47(18):2723–2728 [75] Collin C, Godbold J, Hajdu S, Brennan M. Localized extremity soft tissue sarcoma: an analysis of factors affecting survival. J Clin Oncol. 1987; 5(4):601–612 [76] Bernthal NM, Putnam A, Jones KB, Viskochil D, Randall RL. The effect of surgical margins on outcomes for low grade MPNSTs and atypical neurofibroma. J Surg Oncol. 2014; 110(7):813–816

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Index Note: Page numbers set bold or italic indicate headings or figures, respectively.

A Abductor digiti minimi, in ulnar nerve innervation 33 Abductor pollicis brevis, in anterior interosseous nerve innervation 29 Abductor pollicis longus, in anterior interosseous nerve innervation 38, 39 Accessory obturator nerve, in lumbar plexus 44 Active Movement Scale (AMS) 151 Adductor pollicis, in ulnar nerve innervation 34 Age, of patient, as prognostic factor 90 Allografts 78 – See also Grafting, nerve Amplitude, in electroneurography 51, 51 Amyloidoma 72 Anatomy, nerve – in electrodiagnostics 48 – in lower limb 10, 10, 11–14 – in nerve injuries 19 – in upper limb 1–8 Anterior interosseous group 27, 29 Anterior interosseous nerve palsy 31 Anterior interosseous nerve syndrome 107, 108 Anterior tarsal tunnel 119 Arcade of Fröhse 36–37 Assisting Hand Assessment (AHA) 166 Autografts 77, 77, 78 – See also Grafting, nerve Axillary nerve, in brachial plexus anatomy 8, 8 Axonotmesis – in electrodiagnostics 60 – in MRI 60, 60–61 – in peripheral nerve injury grading 19 Axons, in electrodiagnostics 48, 48

B Bell’s palsy 174 Biceps brachii, in musculocutaneous nerve innervation 24, 26 Biopsy, in peripheral nerve tumors 189 Birth injury, to sciatic nerve 45 Blunt trauma – lacerations in 87 – timing of repair in 85, 87 Brachial plexus 24 – See also Thoracic outlet syndrome (TOS) – anatomic variants 1

210

– – – – – – – –

anatomy 1, 1, 2–3, 3, 4, 4, 5–8 axillary nerve in 8, 8 collateral branches of 2–3 dorsal scapular nerve in 2 in gunshot wounds 98–99, 99, 101 infraclavicular 3, 3 long thoracic nerve in 2 medial cutaneous nerve of arm in 3 – medial cutaneous nerve of forearm in 3 – medial pectoral nerve in 4 – median nerve in 5, 5, 6 – phrenic nerve in 2 – portions of 1 – radial nerve in 4, 4, 5 – spinal nerves and 1, 2 – subscapular nerve in 4 – subscapular nerves in 4 – supraclavicular 1, 2 – suprascapular nerve in 2, 3 – sympathetic nervous system and 2 – terminal branches of 4, 4, 5–8 – thoracodorsal nerve in 4 – traumatic lesions of –– closed 135 –– imaging in 137 –– location of injury in 136, 136 –– mechanisms of injury 135 –– open 135 –– pain in 137 –– physical evaluation in 137, 137 –– seven seventies rule in 136 –– surgery for ––– approach in 141 ––– extraplexual neurotization and 142 ––– grafting in 141, 143 ––– injury pattern and 142, 146 ––– neurotization in 145 ––– outcomes with 147 ––– plexoplexal neurotization in 142 ––– reinnervation priorities in 141 ––– repair strategies in 141, 143 –– types 135 – trunks in 1, 2, 2 – tumors in, benign 191 – ulnar nerve in 6, 6, 7 Brachialis branch to median nerve transfer, in brachial plexus trauma 145 Brachialis, in musculocutaneous nerve innervation 25 Brachioradialis 24, 36–37, 37 Brachioradialis palsy 40

C Carpal tunnel syndrome (CTS) 31 – clinical presentation of 105

– complications in treatment of 107 – endoscopic carpal tunnel release for 106 – in MRI 62 – in ultrasound 66 – open carpal tunnel release for 106, 106 – surgical strategy for 106, 106, 107 – timing of treatment of 105 Carpal tunnel, in median nerve anatomy 6 Cervical ribs, thoracic outlet syndrome and 129 Chassaignac’s tubercle 157 Cheiralgia paresthetica 112 Chemotherapy, in malignant peripheral nerve sheath tumors 203 Children, see Pediatric patients Collagen nerve tubes 80 Common fibular nerve, in sacral plexus 16 Common peroneal nerve, see Peroneal nerve – in closed injuries 43 – in fibula, injury of 45 – in popliteal fossa, injury of 45 – in sacral plexus 44 – in sacral plexus anatomy 15 – laceration 21 – symptoms of injury to 45 Compartment syndrome 22 Complications, in carpal tunnel syndrome surgery 107 Compression injury 20 – electrodiagnostics in 52 – in MRI 62, 62, 63 – in ultrasound 66, 67 – of femoral nerve 122, 123 – of genitofemoral nerve 122 – of iliohypogastric nerve 122 – of ilioinguinal nerve 122 – of lateral femoral cutaneous nerve 121 – of obturator nerve 124, 124 – of peroneal nerve 117, 118 – of pudendal nerve 124, 125 – of saphenous nerve 123 – of sciatic nerve 45, 115, 116 –– in pelvis 45 – of tibial nerve 120 – recurrent, in ultrasound 66, 67 – timing of repair in 87 Computed tomography (CT) – in malignant nerve sheath tumors 198, 199 – myelography, in neonatal brachial plexus palsy 151 Corachobrachialis, in musculocutaneous nerve innervation 24

CTS, see Carpal tunnel syndrome (CTS) Cubital tunnel syndrome (CUTS) 35 – anterior transposition for 110, 110 – clinical presentation of 109 – electrodiagnostics in 109 – in situ decompression for 109, 110 – in ultrasound 66, 67 – medial epicondylectomy for 111 – surgical strategies for 109, 110 – timing of treatment of 109 CUTS, see Cubital tunnel syndrome (CUTS) Cyclosporine 79

D Deep fibular nerve, in sacral plexus 16 Deep subgluteal syndrome, see Piriformis syndrome Demyelination, in electrodiagnostics 48 Dermal nerve sheath myxoma 187, 193 Desmoid tumor 187, 194 Dorsal cutaneous nerve 34 Dorsal scapular nerve, in brachial plexus anatomy 2

E EDS, see Electrodiagnostics (EDS) Elbow – in neonatal brachial plexus surgery 165 – in ulnar nerve clinical findings 35 – radial nerve entrapment at 111, 112 – ulnar nerve entrapment at 109, 110 Electrical injuries 22, 23 Electrodiagnostics (EDS) – amplitude in 51, 51 – anatomy in 48 – axonal damage in 48 – axonotmesis in 60 – demyelination in 48 – electrodes in 49, 49, 50 – F-wave in 51 – H-reflex in 51 – in compression injury 52 – in cubital tunnel syndrome 109 – in neonatal brachial plexus palsy 152 – in peripheral nerve tumors 189 – in piriformis syndrome 116 – in preoperative evaluation 49, 49, 50–52

Index – in thoracic outlet syndrome 139 – latency in 51, 51 – neuropraxia in 60 – neurotmesis in 60 – pathophysiology in 48 – physiology in 48 – recording equipment in 49 – registry errors in 52 – stimulator in 49 – traction injury in 53 Electromyography – in preoperative evaluation 51 – neurogenic pattern on 52 – registry errors in 52 Electroneurography, in preoperative evaluation 49, 50 endoscopic carpal tunnel release for 106–107 Entrapment, see Compression injury Epineural fibrosis, in ultrasound 66, 67, 71 Epineural grafts, in nerve tubes 80 Examination – in malignant peripheral nerve sheath tumors 201, 201 – in neonatal brachial plexus palsy 150 – of median nerve 26, 27–30, 31 – of musculocutaneous nerve 24, 24, 25–26 – of radial nerve 36, 37–39, 40 – of ulnar nerve 31, 32–35, 35 Extensor carpi radialis brevis 37, 37 Extensor carpi radialis longus 36– 37, 37 Extensor carpi ulnaris 38 Extensor digitorum communis, examination of 38 Extensor indicis 39 Extensor pollicis longus 38, 39 Extraplexual neurotization, in brachial plexus trauma 142

F F-wave 51 Facial nerve palsy – congenital 174 – extracranial nerve repair in 174 – facio-facial cross-face in 175 – facio-facial suture in 174 – hypoglossal-facial anastomosis in 176 – hypoglossal-facial intratemporal translocation in 177, 178 – hypoglossal-facial jump graft in 176, 176, 177 – in gunshot wounds 174, 175 – in skull base fracture 181 – intracranial nerve repair in 175 – masseteric-facial anastomosis in 178, 179–180 – mixed techniques with 179, 180 – nerve transfers in 175 – nuclear peripheral palsy in 181, 181

– spino-facial anastomosis in 176 – surgical techniques in 174 – timing of repair in 180 Facio-facial cross-face, in facial nerve palsy 175 Facio-facial suture 174 Fascicular disruption 20, 20 Femoral group, in lumbar plexus anatomy 11, 12–14 Femoral nerve – anatomy 46 – clinical exploration of 13 – closed injury of 46 – compression injury of 122, 123 – in lumbar plexus anatomy 13, 44 – level of injury in 91 – motor disability with 47 – open injuries of 46 – surgical approach to 14 – symptoms of involvement of 46 Fibular head, common peroneal nerve injury in 45 Fibular neck, common peroneal nerve injury in 45 Fibular nerve – clinical exploration of 16 – deep 16 – in sacral plexus 16 – superficial 16 – surgical approach to 16 Flexor carpi radialis, in median nerve innervation 27, 28 Flexor carpi ulnaris, in ulnar nerve innervation 32, 33 Flexor digiti minimi, in ulnar nerve innervation 33 Flexor digitorum profundis – in anterior interosseous nerve innervation 28, 29 – in ulnar nerve innervation 32, 33 Flexor digitorum superficialis – in anterior interosseous nerve innervation 27 – in median nerve innervation 27, 28 Flexor pollicis brevis – in anterior interosseous nerve innervation 29, 29 – in ulnar nerve innervation 34 Flexor pollicis longus – in anterior interosseous nerve innervation 27–28, 29 – in ulnar nerve innervation 34 Forearm group 32, 33 Fractures – ,timing of repair in 85 – in lumbosacral plexus injury 169 – skull base, facial nerve paralysis in 181 Froment’s sign 109

H-reflex 51 Hand – intrinsic muscles of 33, 34 – neonatal brachial plexus palsy and 164 – sensory innervation in 40 Hemangioblastoma 187, 193 Hip arthroplasty, obturator nerve injury in 46 Hip, sciatic nerve injury in 45 Horner’s syndrome – brachial plexus anatomy and 2 – brachial plexus trauma and 136 Hypoglossal-facial anastomosis, in facial nerve palsy 176 Hypoglossal-facial intratemporal translocation, in facial nerve palsy 177, 178 Hypoglossal-facial jump graft, in facial nerve palsy 176, 176, 177 Hypothenar group 32, 33

G

I

Ganglioneuroma 187, 193 Genitofemoral nerve

Iliohypogastric nerve – compression injury of 122

– compression injury of 122 – in lumbar plexus anatomy 11, 44 Gilliatt-Sumner hand 124, 129 Gluteal region, sciatic nerve injury in 45 Grafting, nerve – autografts in 77, 77, 78 – fish mouthing in 77, 78 – immunosuppression in 79 – in brachial plexus trauma repair 141, 143 – in facial nerve palsy 176, 176, 177 – major histocompatibility complex matching in 79 – sural nerve in 78 Gunshot wounds – brachial plexus in 98–99, 99, 101 – clinical characteristics in 99 – facial nerve palsy in 174, 175 – high velocity 98 – indications for surgery in 100 – low velocity 98 – lumbosacral plexus in 169, 170 – nerve lesion characteristics in 99 – prognosis with 101 – results with 101 – sciatic nerve in 98, 100 – timing of repair in 85, 87, 100 Guyon’s canal, in ulnar nerve anatomy 6, 31 Guyon’s syndrome – clinical presentation of 111 – in ultrasound 66 – surgical strategy for 111 – timing of treatment of 111

H

– in lumbar plexus anatomy 11, 11, 44 Ilioinguinal nerve – compression injury of 122 – in lumbar plexus anatomy 11, 44 Imaging, see Positron emission tomography (PET) – in axonotmesis 60, 60–61 – in brachial plexus traumatic lesions 137 – in carpal tunnel syndrome 62 – in entrapment neuropathies 62, 62, 63 – in lumbosacral plexus injury 171 – in neonatal brachial plexus palsy 151 – in neurofibroma 64 – in neurotmesis 60, 61–62 – in schwannoma 64 – in thoracic outlet syndrome 129, 130, 131, 138–139 – in tumors 62, 64 –– benign peripheral nerve 188, 189 –– malignant peripheral nerve 197, 199 Immunohistochemistry, in malignant peripheral nerve tumors 201 Immunosuppression, in nerve grafting 79 Inferior gluteal nerve, in sacral plexus 44 Inguinal group, in lumbar plexus anatomy 11 Injection injury 21, 22 – of sciatic nerve 45 – timing of repair in 86, 88 Intercostal nerves, as donor in brachial plexus grafting 143, 158 Intercostobrachial nerve, in anatomy 1 Intrinsic muscles of hand 33, 34 Ischemic injury, timing of repair in 86

K Kiloh-Nevin syndrome 107, 108

L Laceration 20, 21, 23 – in blunt trauma 87 – timing of repair in 86 Latency, in electroneurography 51, 51 Lateral antebrachial cutaneous nerve, as donor site in grafting 78 Lateral cutaneous nerve 25, 26 Lateral epicondyle group 37, 37 Lateral femoral cutaneous nerve – as donor site 78 – clinical exploration of 12

211

Index – compression injury of 121 – entrapment, in ultrasound 66 – in lumbar plexus anatomy 12, 44 – surgical approach to 12 Lateral musculocutaneous nerve, in lumbar plexus anatomy 13 Long thoracic nerve, in brachial plexus anatomy 2 Lower lateral cutaneous nerve to arm 39 Lower limb, see Lumbar plexus, Sacral plexus – clinical aspects of peripheral nerve lesions in 42, 43, 44 – lumbar plexus in 10, 10, 11–14 – lumbosacral plexus in 42, 43 – outcomes with 96, 97 – sacral plexus in 14, 14, 15 – ultrasound of compression neuropathies in 66, 67 Lumbar plexus 43, 44 – femoral group in 11, 12–14 – femoral nerve in 13 – genitofemoral nerve in 11 – iliohypogastric nerve in 11, 11 – ilioinguinal nerve in 11 – in lower limb anatomy 10, 10, 11–14 – inguinal group in 11 – lateral femoral cutaneous nerve in 12 – obturator nerve in 12 – surgical approach to 11 Lumbosacral plexus 42, 43 – injury –– clinical pictures of 169 –– complete 171 –– epidemiology of 169 –– fractures in 169 –– imaging in 171 –– in gunshot wounds 169, 170 –– lumbosacral trunk injury in 171 –– management of 170 –– mechanisms 169 –– motor impairment in 171 –– natural history in 171 –– pain in 171 –– patterns 169, 171 –– repair principles 172, 173 –– sacral plexus injury in 171 –– sensory loss in 171 –– surgical indications 172 – tumors in, benign 191, 192 Lumbricals 30, 30, 34, 34 Lymphoma 72

M Magnetic resonance imaging (MRI), see Imaging – axonotmesis in 60, 60–61 – carpal tunnel syndrome in 62 – entrapment neuropathies in 62, 62, 63 – lumbosacral plexus injury in 171

212

– neonatal brachial plexus palsy in 152 – neurofibroma in 64 – neurotmesis in 60, 61–62 – schwannoma in 64 – tumors in 62, 64 –– malignant peripheral nerve sheath 197, 199 Major histocompatibility complex (MHC) matching, in allografting 79 Malignant peripheral nerve sheath tumor (MPNST) 63 Mallet shoulder score 151 Martin-Gruber anastomosis 5, 30 Masseteric-facial anastomosis, in facial nerve palsy 178, 179–180 Medial antebrachial cutaneous nerve, as donor site in grafting 78 Medial cord-musculocutaneous transfer, in brachial plexus trauma 145 Medial cutaneous nerve of arm, in brachial plexus anatomy 3 Medial cutaneous nerve of forearm, in brachial plexus anatomy 3 Medial epicondylectomy, for cubital tunnel syndrome 111 Medial musculocutaneous nerve, in lumbar plexus anatomy 13 Medial pectoral nerve – as donor nerve in brachial plexus grafting 158 – in brachial plexus anatomy 4 Median nerve – anatomy 27 – clinical aspects in 26, 27–30, 31 – in brachial plexus anatomy 5, 5, 6 – level of injury in 91 – motor innervation 26, 28–30 – sensory innervation 30, 30 Meralgia paresthetica 121 MHC, see Major histocompatibility complex (MHC) Microscopic examination, of malignant peripheral nerve sheath tumors 201 Missile injuries, see Gunshot wounds Morton’s neuroma – in ultrasound 66 – tibial nerve in 121 Motor innervation – median nerve 26, 28–30 – radial nerve 36 – ulnar nerve 33–34 Motor nerve conduction studies, in preoperative evaluation 49, 50 Motor units, in electrodiagnostics 48 MPNST, see Malignant peripheral nerve sheath tumor (MPNST) MRI, see Magnetic resonance imaging (MRI) Musculocutaneous nerve – clinical aspects in 24, 24, 25–26 – in brachial plexus anatomy 7, 8

– level of injury in 91 – palsies 25 Myelin sheath, in electrodiagnostics 48

N NBPP, see Neonatal brachial plexus palsy (NBPP) Neoadjuvant therapy, in malignant peripheral nerve sheath tumors 204 Neonatal brachial plexus palsy (NBPP) – Active Movement Scale in 151 – assessment scale for 150–151 – avulsion in 159 – clinical assessment in 150 – CT myelography in 151 – electrodiagnostics in 152 – epidemiology of 149 – hand function after 164 – imaging in 151 – Mallet shoulder score in 151 – MR myelography in 152 – neurotmesis in 159, 160 – physical examination in 150 – risk factors for 149, 149 – shoulder function after 164 – surgery for –– exposure in 155, 157 –– group 1 160, 161, 162 –– group 2 160, 162, 163 –– group 3 163 –– infraclavicular exposure in 157 –– lesion assessment in 159 –– nerve transfers in 158 –– patient selection in 155 –– postoperative care in 163 –– principles of 159, 160 –– results of 163 –– supraclavicular exposure in 155, 163 –– sural nerve in 160, 161, 161 – surgical assessment of 152 – treatment pathway for 153 – ultrasound in 152 Nerve conduction studies, in preoperative evaluation 49, 50 Nerve repair – approach 74 – direct 75 – end-to-end 75 – end-to-side 76 – epineural 75 – evaluation in 74 – fascicular 76, 76 – grafting in –– autografts in 77, 77, 78 –– fish mouthing in 77, 78 –– immunosuppression in 79 –– in brachial plexus trauma 141, 143 –– major histocompatibility complex matching in 79 –– sural nerve in 78 – grouped fascicular 76

– in facial palsy 174–175 – nerve tubes in –– artificial conduits in 80 –– autologous conduits in 80 –– collagen 80 –– diameter of 79 –– epineural grafts in 80 –– polyglycolic acid in 80 –– polylactide-caprolactone polymer 80 –– technique with 79, 79 –– vein grafts in 80 – neurolysis in 75 – postoperative management in 81 – principles of 75 – timing of 74, 84 – tissue engineering and 81 Nerve transfers – in brachial plexus trauma 145 – in facial palsy 175 – in neonatal brachial plexus injury 158 Neurofibroma – in MRI 64 – outcomes with 193 – plexiform 186, 186, 188 – type 1 186 – types of 185 Neurofibromatosis type 1 (NF1) 196 Neurofibromatosis type 2 (NF2) 185 Neurolysis, in nerve repair 75 Neuropraxia – in electrodiagnostics 60 – in peripheral nerve injury grading 19 Neurothekeoma 188, 194 Neurotization, in brachial plexus trauma 142, 145 Neurotmesis – in electrodiagnostics 60 – in MRI 60, 61–62 – in neonatal brachial plexus lesion 159, 160 – in peripheral nerve injury grading 19–20 NF1, see Neurofibromatosis type 1 (NF1) NF2, see Neurofibromatosis type 2 (NF2)

O Obstetric injury, to sciatic nerve 45 Obturator nerve – anatomy 46 – clinical exploration of 13 – compression injury of 124, 124 – in lumbar plexus anatomy 12, 44 – injuries 46 – surgical approach to 13 Opponens pollicis, in anterior interosseous nerve innervation 29, 29

Index Outcomes – grading systems and 92, 92, 93– 94 – in benign peripheral nerve tumors 192 – in brachial plexus trauma reinnervation 147 – in dermal nerve sheath myxoma 193 – in desmoid tumors 194 – in ganglioneuroma 193 – in hemangioblastoma 193 – in hybrid nerve sheath tumors 193 – in lower extremity repair 97 – in neonatal brachial plexus lesion surgery 163 – in neurothekeoma 194 – in schwannoma 192 – in upper extremity repair 94, 94, 95–96, 96 – injury characteristics in 91, 91 – nerve characteristics in 90 – patient age and 90 – prognostic factors in 90 – rehabilitation and 92 – with gunshot wounds 101 – with perineuroma 193

P Paget-Schroetter syndrome 128 Pain – in brachial plexus trauma 137 – in lumbosacral plexus injury 171 Palmaris brevis, in ulnar nerve innervation 32 Palmaris longus, in median nerve innervation 27 Pectoral nerve, as donor in brachial plexus grafting 143, 158 Pediatric patients, malignant peripheral nerve sheath tumors in 207 Pelvis, sciatic nerve injury in 45 Perineuroma 186, 193 Peroneal nerve, see Common peroneal nerve – anatomy 42, 117 – compression injury of 117, 118 – in anterior tarsal tunnel 119 – level of injury in 91 – surgical strategies for 118, 118 PET, see Positron emission tomography (PET) Phrenic nerve – as donor in brachial plexus grafting 143, 158 – in brachial plexus anatomy 2 – in neonatal brachial plexus lesion surgery 156 Piriformis syndrome – conservative treatment of 116 – electrodiagnostics in 116 – pathologies in 115 – sciatic nerve anatomy and 14, 14 – surgical strategy for 116

PLCL, see Polylactide-caprolactone polymer (PLCL) Plexoplexal neurotization, in brachial plexus trauma 142 Polyglycolic acid nerve tubes 80 Polylactide-caprolactone polymer (PLCL) nerve tubes 80 Popliteal fossa, common peroneal nerve injury in 45 Positron emission tomography (PET), tumors in, malignant peripheral nerve sheath 198, 199 Posterior cutaneous nerve to arm 39 Posterior cutaneous nerve to forearm 40 Posterior femoral cutaneous nerve, in sacral plexus 44 Posterior interosseous nerve – examination 38 – in radial nerve anatomy 4, 36 – motor neuropathy with 41 – palsy 41 Posterior interosseous nerve syndrome 111, 112 Posterior tarsal tunnel syndrome 120 Postoperative care, in neonatal brachial plexus lesion repair 163 Preoperative evaluation – electrodiagnostics in 49, 49, 50– 52 – electromyography in 51 – electroneurography in 49, 50 – F-wave in 51 – H-reflex in 51 – motor nerve conduction studies in 49, 50 – sensory nerve conduction studies in 50, 50 – ultrasound in 68, 68, 69 Pressure injury 20 Prognostic factors 90 Pronator quadratus, in anterior interosseous nerve innervation 27–28, 29 Pronator teres – clinical findings 31 – in median nerve innervation 27, 28 Pronator teres syndrome 31, 108 Proximal forearm group 27, 28 Proximal soleal sling 120 Pudendal nerve, compression injury of 124, 125

Q Quadriceps nerve, in lumbar plexus anatomy 13 Quadriceps, in femoral nerve injury 46

R Radial nerve – anatomy 36

– clinical aspects of 36, 37–39, 40 – entrapment at elbow 111, 112 – in brachial plexus anatomy 4, 4, 5 – in Wartenberg’s syndrome 112 – level of injury in 91 – motor innervation 36 – sensory innervation 39, 39 Radiation injury 23 – timing of repair in 86 Radiation therapy – for peripheral nerve sheath tumors 204 – peripheral nerve sheath tumors after 196, 207 Radiology, see Imaging, Radiation therapy Ramsay Hunt zoster palsy 174 Recording equipment, in electrodiagnostics 49 Rehabilitation, outcome and 92 Repair, see Nerve repair Ribs, cervical, thoracic outlet syndrome and 129 Riche-Cannieu anastomosis 5, 30

S Sacral plexus 43, 44 – See also Lumbosacral plexus – in lower limb anatomy 14, 14, 15 – sciatic nerve in 14, 14, 15 – tibial nerve in 15, 15 Saphenous nerve – compression injury of 123 – in lumbar plexus anatomy 13 – lesions 46 Schwannoma 184, 185 – in MRI 64 – in tibial nerve 193 – in ultrasound 72 – outcomes with 192 Schwannomatosis 185 Schwann’s cells 48 Sciatic nerve – anatomy 42 – birth injury of 45 – clinical exploration of 15 – compression injury of 45, 115, 116 – in closed injuries 43 – in gluteal region, injury of 45 – in gunshot wounds 98, 100 – in hip, injury of 45 – in open injuries 43 – in pelvis, injury of 45 – in sacral plexus anatomy 14, 14, 15 – injection injury of 45 – lymphoma in 72 – obstetric injury of 45 – stretch injuries in 43 – surgical approach to 15 – terminal branches of 15 Sensory innervation – median nerve 30, 30 – radial nerve 39, 39

– ulnar nerve 34, 35 Sensory nerve conduction studies, in preoperative evaluation 50, 50 Short tau inversion recovery (STIR), axonotmesis in 60, 60–61 Shoulder dystocia 149 Shrapnel 43 Silicone nerve tubes 80 Skull base fracture, facial nerve paralysis in 181 Somsak’s procedure 145 Spinal accessory nerve, as donor in brachial plexus grafting 143, 158 Spino-facial anastomosis, in facial nerve palsy 176 Stab wounds, timing of repair in 85 – See also Laceration STIR, see Short tau inversion recovery (STIR) Sublimis arch syndrome 31 Subscapular nerve, as donor in brachial plexus grafting 143 Subscapular nerve, in brachial plexus anatomy 4 Superficial fibular nerve, in sacral plexus 16 Superficial peroneal nerve entrapment 120 Superficial sensory radial nerve 40 – as donor site 78 Superior gluteal nerve, in sacral plexus 44 Supinator syndrome, in ultrasound 66 Suprascapular nerve – in brachial plexus anatomy 2, 3 – in neonatal brachial plexus lesion surgery 157 Suprascapular nerve entrapment 112, 113 Sural nerve – as donor site in grafting 78 – entrapment 120 – in neonatal brachial plexus lesion surgery 160, 161, 161 Surgery, see Nerve repair Surgical approach – in brachial plexus tumors 191 – to femoral nerve 14 – to fibular nerve 16 – to lateral femoral cutaneous nerve 12 – to lumber plexus 11 – to obturator nerve 13 – to sciatic nerve 15 Sympathetic nervous system, brachial plexus and 2

T Tacrolimus 79 Thenar group 28, 29, 34, 34 Thermal injury 22 – timing of repair in 86 Thoracic outlet syndrome (TOS)

213

Index – – – – –

cervical ribs in 129 diagnosis of 128, 129–131 disputed neurogenic 128, 131 electrodiagnostics in 139 imaging in 129, 130, 131, 138– 139 – in literature 133 – in ultrasound 66 – neurogenic 128 – surgical approach in 129, 132 – surgical indications in 139 – true neurogenic 128 – vascular 128, 133 Thoracodorsal nerve, as donor in brachial plexus grafting 143 Thoracodorsal nerve, in brachial plexus anatomy 4 Tibial nerve – anatomy 42, 120 – clinical exploration of 16 – compression injury of 120 – in Morton’s neuroma 121 – in posterior tarsal tunnel syndrome 120 – in proximal soleal sling 120 – in sacral plexus 44 – in sacral plexus anatomy 15, 15 – level of injury in 91 – schwannoma 193 – surgical approach to 16 – symptoms of injury to 46 Tissue engineering, nerve repair and 81 TOS, see Thoracic outlet syndrome (TOS) Total hip arthroplasty, obturator nerve injury in 46 Traction injuries 19, 19, 20 – in electrodiagnostics 53 – in pelvis 45 – in sciatic nerve 43, 45 – timing of repair in 86, 87 Triceps group 37, 37 Triceps palsy 40 Tubes, nerve – artificial conduits in 80 – autologous conduits in 80

214

– – – – –

collagen 80 diameter of 79 epineural grafts in 80 polyglycolic acid in 80 polylactide-caprolactone polymer 80 – technique with 79, 79 – vein grafts in 80 Tumors – benign peripheral nerve –– as asymptomatic 188, 190 –– biopsy of 189 –– clinical presentation 188 –– dermal nerve sheath myxoma in 187, 193 –– desmoid tumors in 187, 194 –– electrodiagnostics in 189 –– ganglioneuroma in 187, 193 –– hemangioblastoma in 187, 193 –– hybrid nerve sheath tumors in 186, 187, 193 –– imaging in 188, 189 –– in brachial plexus 191 –– in lumbosacral plexus 191, 192 –– neurofibroma in 185, 193 –– neurofibromatosis type 2 in 185 –– neurothekeoma in 188, 194 –– nomenclature in 184 –– operative techniques with 190, 192–193 –– outcomes with 192 –– perineuroma in 186, 193 –– schwannoma in 184, 185, 192 –– schwannomatosis in 185 –– surveillance of 190 –– treatment approach in 190 –– types of 184, 188 – in MRI 62, 64 – in ultrasound 69, 72 – malignant peripheral nerve sheath –– chemotherapy for 203 –– clinical presentation of 196 –– epidemiology of 196, 197 –– epithelioid 202 –– glandular 202

–– –– –– –– –– –– –– –– –– –– –– –– –– –– –– –– –– –– –– –– ––

grading of 200, 203 gross examination in 201, 201 imaging in 197, 199 immunohistochemistry in 201 in CT 198, 199 in PET 198, 199 in ultrasound 200, 200 low-grade 207 microscopic examination of 201 neoadjuvant therapy in 204 pathology in 200, 200 pediatric 207 prognosis in 204, 205 radiation therapy as cause of 196, 207 radiation therapy for 204 recurrence of 204 staging of 202 subtypes of 202 surgery for 202, 203 survival in 204, 205 treatment of 202

U Ulnar nerve – amyloidoma in 72 – as donor site 78 – clinical aspects 31, 32–35, 35 – compression 35 – entrapment at elbow 109, 110 – in brachial plexus anatomy 6, 6, 7 – in Guyon’s syndrome –– clinical presentation of 111 –– in ultrasound 66 –– surgical strategy for 111 –– timing of treatment of 111 – level of injury in 91 – sensory innervation 34, 35 Ulnar-musculocutaneous nerve transfer, in brachial plexus trauma 145 Ultrasound, see Imaging – basic principles 65

– carpal tunnel syndrome in 66 – compression injury in 66, 67 – cubital tunnel syndrome in 66, 67 – in neonatal brachial plexus palsy 152 – in preoperative evaluation 68, 68, 69 – in trauma 68, 68, 69–70, 71, 71 – in upper limb, of compression neuropathies 66, 67 – intraoperative 68, 70, 71 – tendons vs. nerve in 65, 66 – transducer 65 – tumors in 69, 72 –– malignant peripheral nerve sheath 200, 200 Upper limb, see Brachial plexus – nerve anatomy in 1–8 – outcomes with 94, 94, 95–96 – ultrasound of compression neuropathies in 66, 67

V Variants, anatomic – of brachial plexus 1 – of median nerve 5 Vein grafts, as nerve tubes 80

W Wartenberg’s syndrome 112 Wave morphology, in electrodiagnostics 51 Wrist – Guyon’s syndrome in –– clinical presentation of 111 –– in ultrasound 66 –– surgical strategy for 111 –– timing of treatment of 111 – median nerve in, clinical aspects of 31 – ulnar nerve in, clinical aspects of 35