Vertigo

Springer-Verlag London Ltd.

Thomas Brandt

Vertigo Its Multisensory Syndromes

2nd Edition

Springer

Professor Thomas Brandt, FRCP Neurologische Klinik, Klinikum Großhadern, Ludwig-Maximillians-Universität, Marchioninistraße 15,81377 Munich, Germany

ISBN 978-0-387-40500-1

British Library Cataloguing in Publication Data Brandt, Thomas Vertigo: its multisensory syndromes. - 2nd ed.

1. Vertigo 2. Diagnosis, Differential. I. Title 616.8'41 ISBN 978-0-387-40500-1 ISBN 978-1-4757-3801-8 (eBook) DOI 10.1007/978-1-4757-3801-8

Library of Congress Cataloging-in-Publication Data A catalog record for this book is available from the Library of Congress

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Preface to the Second Edition

This monograph has been written for clinicians who are involved in the management of the dizzy patient and for scientists with a particular interest in the multi-sensorimotor mechan­isms that subserve spatial orientation, motion perception, and ocular motor and postural con­trol. Special emphasis has been put on making the correct diagnosis, and detailed recommendations have been given for specific treatments.

The second edition has resulted in an almost completely new book due to the dramatic expansion in the 1990s of our understanding of vestibular function and dis orders. A few rele­vant examples include the novel concept of canalolithiasis, as opposed to cupulolithiasis, both of which are established causes of typical posterior and horizontal canal benign paroxysmal positioning vertigo; familial episodic ataxia land II have been identified as inherited chan­nelopathies; otolithic syndromes were recognized as a variety separate from semicircular canal syndromes; several new central vestibular syndromes have been described, localized, and attributed to vestibular pathways and centres; a new classification based on the three major planes of action of the vestibulo-ocular reflex is available for central vestibular syn­dromes; and the mystery of the location and function of the multisensory vestibular cortex is slowly being unravelled.

This book differs from other clinical textbooks in that it is not divided into two parts: anatomy and physiology, on the one hand, and disorders, on the other. Introductory chapters on several aspects of vestibular syndromes, their diagnosis, and their management are fol­lowed by sections and chapters that focus on the description of specific dis orders. Anatomy and physiology are discussed only when relevant for the understanding of the mechanism.

Although there are many experts in the field who know better than I particular diseases of their interest, I nevertheless ventured on the writing of this interdisciplinary book alone for two reasons: first, to make the reader's usage easier by a uniform presentation and second, to improve my own competence in treating the dizzy patient by studying the research of others. The central focus of the book is on the patient who because of complaints that are typical of different disorders is frequently shuttled between neurologists, otolaryngologists, internists, and psychiatrists.

Preface to the First Edition

Vertigo consists of a variety of syndromes which are surprisingly easy to diagnose and can, in most cases, be treated effectively. However treatment requires an interdisciplinary approach to the patient which is unusual for clinicians who have usually been trained to specialise in a particular area. Sensorimotor physiology is the key to an understanding of the pathogenesis of vertigo; careful history-taking and otoneurological examination are the key to diagnosis.

The book is organised in sections covering the major sub divisions of vertigo, including peripherallabyrinthine disorders (Meniere's disease, vestibular neuritis, perilymph fistulas), central vestibular dis orders (vestibular epilepsy, downbeat/upbeat nystagmus), positional, vascular, traumatic and familial vertigo, vertigo in childhood and vertigo related to drugs. Sections are further subdivided into chapters covering particular aspects, for example the chapter on migraine and vertigo in the section on vascular vertigo. There is a full description ofthe clinical features and diagnostic procedures for each disease (with summarising tables), and special emphasis is placed on the relationship between management and the underlying pathological mechanisms.

Most diseases are referred to in several different sections in order to facilitate the differen­tial diagnosis of conditions with similar signs and symptoms. The section on vertigo arising from multisensory interaction covers non-vestibular syndromes such as visual vertigo and cervical vertigo and, more importantly, the psychogenic vertigo syndromes; the latter are the third commonest cause of vertigo in patients seen by neurologists.

This book will contribute to an improvement in diagnosis and management in patients suf­fering from vertigo and disequilibrium. A further dem an ding goal of this book is to establish a platform from which physiologists and clinicians may launch cooperative research concern­ing the intriguing mechanisms of spatial orientation, oculomotor and postural control and ultimately to aid patients with vertigo.

Acknowledgements

I am indebted to many people for helping with this second edition. I want first to thank Judy Benson, who not only conscientiously undertook the language editing of the manuscript but also as an attentive reader, unburdened by a medical background, gave valuable impulses for resolving ambiguities and unclarities. Michael Strupp, an experienced colleague in our Dizziness Unit, made himself indispensable. He critically read the entire manuscript, made important suggestions for improvement, and drew my attention to missing details and rele­vant references. Thanks are also due to MicheIe Seiche, who carefully cross-checked citations in the text and typed and proofed the references.

I wish to express my special thanks to my colleagues in the Dizziness Unit for the stimulat­ing daily discussions on which a large part of our clinical experience is based, in particular Marianne Dieterich, who heads the clinical research group on ocular motor and vestibular disorders.

I am grateful for the constructive cooperation I enjoyed with Springer-Verlag London, in particular Christopher GreenweIl. I also sincerely thank the rest of the staff of Springer-Verlag for their efforts to meet our pressing deadlines. Last, but certainly not least, I want to express my gratitude to my family for their understanding during the ordeal, above all to my wife Birgit, who knowing how important this project was to me, gave it her full support, deferring her own interests and wishes for the sake of its completion.

Contents

Glossary .............................................................. xxiii

Seetion A Vertigo: symptoms, syndromes, dis orders .................. 1

1 Introduction 3

The "vestibular" vertigo syndromes ................................ 3 Signs and symptoms ........................................... 4 The mismatch concept ......................................... 4

The vestibulo-ocular reflex (VOR) ................................. 5 Neuronal network of the VOR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 VOR mediation of perception and postural adjustments ............ 9 Vestibulocollic reflex ........................................... 10

Vestibulospinal reflexes ........................................... 10 Vestibular falls .................................................. 13

Peripheral vestibular falls ....................................... 14 Vestibular neuritis: contraversive rotational vertigo with

ipsiversive falls ............................................ 14 Benign paroxysmal positioning vertigo (BPPV): forward falls

produced by canalolithiasis of the posterior semicircular canal " 15 Meniere's drop attacks (Tumarkin's otolithic crisis) .............. 15 Otolith Tullio phenomenon: contraversive ocular tilt

reaction (OTR) and fall. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Bilateral vestibulopathy with predominant forward and

backward falls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Central vestibular falls ......................................... 15

Vestibular epilepsy with contraversive vertigo and falls ........... 15 Thalamic astasia with contraversive or ipsiversive falls? ........... 16 Ocular tilt reaction: ipsiversive in caudal, contraversive in

upper brainstem lesions .................................... 16 Lateropulsion in Wallenberg's syndrome: ipsiversive falls and

adjustments of perceived vertical ............................ 16 Downbeat nystagmus syndrome with backward falls ............. 16

Vestibular autonomie regulation ................................... 16 Neuroanatomie substrates ...................................... 18

References ........................................................ 19

xii Contents

2 Approaching the patient 23

Dizziness and light-headedness .................................. 23 Attacks of (rotatory) vertigo, episodic vertigo ..................... 23 Sustained (rotatory) vertigo ..................................... 24 Positional/positioning vertigo ................................... 26 Oscillopsia .................................................... 26 Vertigo associated with auditory dysfunction ...................... 27 Dizziness or to-and-fro vertigo and postural imbalance ............. 27

Semicircular canal vertigo and mixed canal-otolith vertigo ............ 28 Otolithic vertigo ................................................. 29 Paroxysmal vertigo .............................................. 29 Neuro-ophthalmological and otoneurological evaluation .............. 34

References ........................................................ 47

3 Management of the dizzy patient .................................... 49

Antivertiginous and antiemetic drugs .............................. 49 Surgical treatment ............................................... 51 Vestibular exercises and physical therapy for vestibular rehabilitation .. 52

Quantitative effects of balance training on postural sway in normal subjects ............................................. 52

Balance training in vestibular disorders ........................... 53 Plasticity of the vestibular system: central compensation and

sensory substitution for vestibular deficits ...................... 55 Terms and definitions of plasticity and central compensation ........ 55 Vestibular compensation and its multiple mechanisms .............. 56 Transmitters of the vestibulo-ocular reflex and drug-modulated

compensation ............................................... 58 Substitution of vestibular function ............................... 60

References ........................................................ 61

Section B Vestibular nerve and labyrinthine dis orders ............... 65

4 Vestibular neuritis ................................................. 67 The clinical syndrome ............................................ 67

Vertigo and posture ............................................ 68 Eye movements ................................................ 69 Caloric testing ................................................ 69 MR imaging .................................................. 70 Natural course ................................................ 71 High-frequency defect ofVOR in permanent peripheral

vestibular lesion ............................................. 71 Differential diagnosis .......................................... 72

Aetiology and pathomechanism ................................... 73 Pathomechanism .............................................. 73 Vestibular neuritis - a partial unilateral vestibular loss ............. 73 Viral or vascular aetiology? ..................................... 75

Historical discussion ......................................... 75 Arguments for viral aetiology ................................. 75

Contents xiii

Site of the lesion 76 Management .................................................... 76

References ........................................................ 79

5 Meniere's disease .................................................. 83

The clinical syndrome ............................................ 83 Attacks ....................................................... 83 Auditory symptoms and signs in the vertigo-free interval ........... 84 Vestibular function in the vertigo-free interval ..................... 85 Imaging ...................................................... 85 Differential diagnosis .......................................... 85

Natural course. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Aetiology and pathomechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

Endolymphatic hydrops ........................................ 86 Aetiology ..................................................... 87

Delayed endolymphatic hydrops ............................... 88 Vascular hypothesis .......................................... 88 Psychosomatic hypothesis .................................... 89

Pathophysiology of attacks and progressive dysfunction . . . . . . . . . . . . . 89 Management .................................................... 90

Attacks ....................................................... 90 Attack-free interval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91 Intratympanic gentamicin therapy ............................... 91 Surgical treatments: nondestructive or destructive . . . . . . . . . . . . . . . . . . 92

Non-destructive ............................................. 92 Destructive ................................................. 93

Pragmatic therapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 Vestibular drop attacks (Tumarkin's otolithic crisis) .................. 94

References ........................................................ 95

6 Perilymph fistulas (PLF) ............................................ 99

The clinical syndromes ........................................... 99 Semicircular canal type of PLF . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 100 Otolith type of PLF ............................................ 100 How maya perilymph fistula be identified? ........................ 101

Pressure fistula tests ........................................ " 101 Vascular fistula tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 101 Imaging techniques (CT, MRI) ................................ 102 Electronystagmography ...................................... 102 Hearing tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 102 Exploratory tympanotomy ................................... 102 Other proposed tests ......................................... 102

Differential diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 102 Aetiology and pathomechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 102

Experimental perilymph/endolymph fistulas and endolymphatic hydrops .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 104

Management .................................................... 105

xiv Contents

Conservative treatment ......................................... 105 Surgical treatment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 106

Tullio phenomenon .............................................. 106 Experimental history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 106 Clinical history ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 107 Clinical types of Tullio phenomena . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 107

Otolith Tullio phenomenon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 107 Why does otolith Tullio phenomenon manifest with

paroxysmal ocular tiIt re action (OTR)? ....................... 108 Vestibulospinal reflexes tested as part of the Tullio phenomenon ..... 108 Management .................................................. 111

Fistula of the anterior semicircular canal ............................ 112 References ........................................................ 113

7 Peripheral vestibular paroxysmia (disabling positional vertigo) . . . . . . . . .. 117

The clinical syndrome ............................................ 117 Case reports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 118

Vertigo ..................................................... 120 Auditory symptoms and tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 120 Other associated symptoms ................................... 120 Electronystagmography ...................................... 121 Subjective visual vertical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 121 Posturography. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 121

Differential diagnosis .......................................... 121 Aetiology and pathomechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 122 Management .................................................... 122

Uncertainties in the diagnosis and treatment of vestibular paroxysmia ................................................. 123

AIternating episodes of vestibular nerve paroxysmia and failure . . . . . . .. 124 References ........................................................ 125

8 Bilateral vestibulopathy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 127

The clinical syndrome ............................................ 127 Diagnosis ..................................................... 128 Associated symptoms and differential diagnosis . . . . . . . . . . . . . . . . . . .. 129

Aetiologies and pathomechanisms ................................. 129 Idiopathic BVF .............................................. 132

Spatial orientation: vestibulo-ocular and vestibulospinal reflexes ..... 135 Management ..................... , .............................. 137

References ........................................................ 139

9 Miscellaneous vestibular nerve and labyrinthine dis orders ............. 143

Imaging of the labyrinth and vestibular nerve . . . . . . . . . . . . . . . . . . . . . . .. 143 Congenital causes ................................................ 143 Infectious causes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 145

Herpes zoster oticus .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 146 Acute otitis media. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 149

Contents xv

Specific infections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 151 Cholesteatoma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 151

Autoimmune inner ear disorders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 151 Cogan's syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 154

How to monitor activity in Cogan's syndrome ................... 155 Tumours ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 155

References ........................................................ 165

Section C Central vestibular disorders ............................... 167

10 Vestibular dis orders in (frontal) roll plane ............................ 175

The clinieal syndrome ............................................ 176 Topographie diagnostie rules .................................... 178 Ocular tilt reaction (OTR) ....................................... 179

Mechanism of OTR .......................................... 180 OTR and perceived tilt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 181 Two types of OTR: the medullary "ascending" VOR-OTR and the

mesencephalie "descending" integrator-OTR . . . . . . . . . . . . . . . . . .. 181 Aetiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 184 Natural course and management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 185

Skew deviation (skew-torsion sign) ............................... 185 Skew torsion: a vestibular brainstem sign of topographie

diagnostic value ........................................... 186 Different types of skew deviation .............................. 186 Alternating skew deviation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 187 Natural course. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 188

Perceived vertieal (subjective visual vertical) . . . . . . . . . . . . . . . . . . . . . .. 189 Historieal reports on SVV tilts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 189 SVV tilt - a vestibular sign? ................................... 189 svv tilt versus room tilt illusion ............................... 190 SVV tilts in central vestibular versus peripheral ocular

motor lesions ............................................. 192 Thalamic and cortical astasia associated with SVV tilts ........... 192

Torsional nystagmus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 193 Three-dimensional modelling of statie vestibulo-ocular brainstem syndromes .......................................... 194

References .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 195

11 Vestibular dis orders in (sagittal) pitch plane. . . . . . . . . . . . . . . . . . . . . . . . . .. 199

Downbeat nystagmus (vestibular downbeat syndrome) . . . . . . . . . . . . . . .. 199 The clinical syndrome .......................................... 199

Nystagmus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 200 Oscillopsia and impaired motion perception .................... 200 Postural imbalance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 201

Aetiology and pathomechanism .................................. 201 Pathomechanism and site ofthe lesions ......................... 201 Aetiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 203

xvi Contents

Management .................................................. 204 Upbeat nystagmus (vestibular upbeat syndrome) ..................... 205

The clinieal syndrome .......................................... 206 Nystagmus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 206 Oscillopsia, motion perception, and spatial orientation . . . . . . . . . . .. 206 Postural imbalance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 207

Aetiology and pathomechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 207 Pathomechanism and site of the lesions . . . . . . . . . . . . . . . . . . . . . . . .. 207 Aetiology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 208

Management .................................................. 209 References ........................................................ 211

12 Vestibular disorders in (horizontal) yaw plane ......................... 215

Horizontal nystagmus as a sign of vestibular tone imbalance in the yaw plane ............................................... 215

Combined VOR dysfunction in more than one plane of action .......... 217 References ........................................................ 217

13 Vestibular cortex: its locations, functions, and dis orders ................ 219

Multiple vestibular cortex areas .................................... 219 No primary vestibular cortex .................................... 219 The parieto-insular vestibular cortex (PIVC) . . . . . . . . . . . . . . . . . . . . . .. 220

Multimodal sensorimotor vestibular cortex function and dysfunction . .. 221 Spatial hemineglect, a cortical vestibular syndrome? ................ 224 Paroxysmal room-tilt illusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 224 Self-motion perception: the mechanism of reciprocal inhibitory

visual-vestibular interaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 225 References ........................................................ 230

14 Vestibular epilepsy ................................................ 233

The vestibular seizure ............................................ 234 Rotatory seizure ("volvular epilepsy") ............................ 234 Differential diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 234 Management .................................................. 235

Epileptic nystagmus .............................................. 235 Vestibular versus visual (optokinetie) seizures ....................... 237 "Vestibulogenic epilepsy" ......................................... 237

References ........................................................ 238

15 Miscellaneous central vestibular dis orders ............................ 241

Central brainstem/cerebellar lesions mimicking vestibular neuritis or peripheral vestibular failure .................................... 241 Paroxysmal central vertigo ........................................ 242 Central vestibular falls without vertigo . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 243 Central vestibular syndromes in multiple sclerosis . . . . . . . . . . . . . . . . . . .. 244 Vestibular syndromes and brain tumours . . . . . . . . . . . . . . . . . . . . . . . . . . .. 244 Metabolie disorders of the vestibular system .. . . . . . . . . . . . . . . . . . . . . . .. 245

References ........................................................ 245

Contents xvii

Seetion D Positional and positioning vertigo ......................... 247

16 Benign paroxysmal positioning vertigo ............................... 251

The clinical syndrome ............................................ 252 Positioning nystagmus ......................................... 253

Vertigo and posture .............................................. 254 Natural course . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 256 Differential diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 256

Pathomechanism and aetiology .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 257 Pathomechanism ............................................... 257

Peripheral or central vestibular dysfunction? .................... 257 The traditional view of cupulolithiasis . . . . . . . . . . . . . . . . . . . . . . . . .. 257 Arguments for canalolithiasis ................................. 259 Unilateral mimicking bilateral BPPV ........................... 261

Aetiology ..................................................... 264 Management .................................................... 265

Positional exercises and liberatory manreuvres . . . . . . . . . . . . . . . . . . . .. 265 Surgical procedures ............................................ 269

Singular neurectomy ......................................... 269 Plugging of the posterior semicircular canal . . . . . . . . . . . . . . . . . . . .. 269

Horizontal semicircular canal BPPV (h-BPPV) ....................... 269 The clinical syndrome .......................................... 270

Atypical h-BPPV with apogeotropic positional nystagmus ......... 270 Natural course. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 271 Aetiology and pathomechanism .................................. 271

Transition of canalolithiasis to cupulolithiasis ................... 274 Reversible ipsilateral caloric hypoexcitability .. . . . . . . . . . . . . . . . . .. 275

Management .................................................. 278 Anterior semicircular canal BPPV (a-BPPV) ......................... 279

References ........................................................ 280

17 Positional nystagmus/vertigo with specific gravity differential between cupula and endolymph (buoyancy hypothesis ) ................ 285

Positional alcohol vertigo/nystagmus (PAN) ......................... 286 Positional "heavy water" nystagmus ................................ 287 Positional glycerol nystagmus. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 287 Positional nystagmus with macroglobulinaemia (Waldenström's

disease) ...................................................... 288 References ........................................................ 288

18 Central positional vertigo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 291

Positional downbeating nystagmus ................................. 291 Central positional nystagmus ...................................... 292 Central paroxysmal positional/positioning vertigo and

paroxysmal positioning vomiting ................................ 293 Transient vertebrobasilar ischaemia ................................ 296

Rotational vertebral artery occlusion ............................. 296

xviii Contents

Head (neck)-extension vertigo ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 297 Bending-over vertigo ............................................. 298

References ........................................................ 298

Seetion E Vascular vertigo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 301

19 Stroke and vertigo ................................................. 307

Strokes causing peripheral and central vestibular disorders ............ 307 Anterior inferior cerebellar artery and the internal auditory artery ..... 308 Vertebral artery and posterior inferior cerebellar artery ... . . . . . . . . . . .. 309

Wallenberg's syndrome ......................................... 309 Basilar artery and paramedian pontine and mesencephalic arteries ..... 312

Vestibular syndromes in roll plane ............................. 312 Vestibular syndromes in pitch plane ............................ 314

Thalamic infarctions ............................................. 314 Cortical infarctions ............................................... 315

Cortical rotational vertigo ....................................... 318 References ........................................................ 322

20 Migraine and vertigo ............................................... 325

Migraine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 326 The clinical syndrome . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 326

Aetiology and pathomechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 326 Management .................................................. 327

Basilar migraine (BM) and "vestibular migraine" . . . . . . . . . . . . . . . . . . . .. 329 The clinical syndrome .......................................... 329

Diagnosis of BM with episodic vertigo ("vestibular migraine") . . . .. 332 Pathomechanisms of vertigo, motion sickness and ocular ........... 333

motor deficits Origin of vertigo in migraine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 333 Motion sickness-like symptoms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 334 Ocular motor deficits in the symptom-free interval

indicate permanent brainstem or cerebellar dysfunction ........ 335 Benign paroxysmal vertigo in childhood .......................... 335 Benign paroxysmal torticollis in infancy .......................... 336 Benign recurrent vertigo ....................................... 337 Dizziness and vertigo as facultative symptoms in migraine

apart from BM ............................................ ,. 337 Association of migraine with other vertigo disorders? . . . . . . . . . . . . . .. 337

References ........................................................ 338

21 Hyperviscosity syndrome and vertigo ................................ 341

The clinical syndrome ............................................ 341 Aetiology and pathomechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 341 Management .................................................... 341

References ........................................................ 342

Section F Traumatic vertigo ......................................... 343

22 Head and neck injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 347

Traumatic otolith vertigo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 349 References ........................................................ 349

23 Vertigo due to barotrauma .......................................... 351

Alternobaric vertigo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 351 Blast injury . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 352 Decompression sickness .......................................... 352

Management .................................................. 352 Round and oval window fistula caused by barotrauma ................ 353

References ........................................................ 354

24 Iatrogenic vestibular disorders ...................................... 355

Intratympanic gentamicin in Meniere's disease: desired and undesired effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 355

Quinine: reversible and irreversible side effects ...................... 356 Vertebral artery dissection due to chiropractic neck manipulation . . . . .. 356 Surgically induced vestibular dysfunction ........................... 356 Iatrogenic benign paroxysmal positioning vertigo .................... 357 Vestibular loss associated with chronic noise-induced hearing loss . . . . .. 357

References ........................................................ 358

Section G Hereditary vestibular disorders and vertigo in childhood ... 361

25 Familial periodic ataxia/vertigo (episodic ataxia) ...................... 365

The clinical syndromes ........................................... 366 Episodic ataxia associated with "interictal" myokymia (type EA-1) .... 366 Episodic ataxia associated with "interictal" nystagmus (type EA-2) .... 367 Differential diagnoses .......................................... 369

Aetiology and pathomechanism .................................... 370 Episodic ataxia type 1, a potassium channelopathy .................. 370 Episodic ataxia type-2, a cerebral calcium channelopathy . . . . . . . . . . .. 370 Effects of acetazolamide and the pathomechanism of EA ............ 372

Management .................................................... 372 References ........................................................ 373

26 Vertigo in childhood ............................................... 375

Benign paroxysmal vertigo of childhood and basilar migraine ......... 376 Motion sickness ................................................. 376 Vestibular neuritis ............................................... 376 Meniere's disease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 377 Perilymph fistulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 377 Unilateral or bilateralloss of vestibular function ..................... 377 Hereditary dis orders causing peripheral vestibular failure ............. 378 Central vestibular syndromes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 379

References ........................................................ 379

xx Contents

Section H Vertigo, dizziness, and falls in the elderly 383

27 Vertigo, dizziness, and falls in the elderly ............................. 385

Physiological ageing of the vestibular system ........................ 385 Age-related changes in eye movements and vestibulo-ocular reflexes.. 385 Age-related changes in postural sway and balance .................. 386

Cautious senile gait and "highest-Ievel gait dis orders" . . . . . . . . . . . . . . . .. 386 Falls in the elderly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 388 Dizziness in the elderly ........................................... 389

References ........................................................ 391

Section I Drugs and vertigo ......................................... 393

28 Drugs and vertigo ................................................. 395

Ototoxic agents .................................................. 395 Cerebellar intoxication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 397 Drugs and eye movements ........................................ 400

References ........................................................ 402

Section J Non-vestibular (sensory) vertigo syndromes ................. 405

29 Visual vertigo: visual control of motion and balance ................... 409

Circularvection and linearvection: optokinetically induced perception of self-motion ......................................... 409

Psychophysics of circularvection ................................. 411 Visual-vestibular interaction: functional significance of

visual and vestibular cortices .................................. 413 Rollvection-tilt: optokinetic graviceptive mismatch ................. 414

Visual pseudo-Coriolis effect and pseudo-Purkinje effect .............. 416 Optokinetic motion sickness ...................................... 417 Physiological height vertigo and postural balance .................... 418

Physical prevention of physiological height vertigo ................. 422 Licence for workers at heights? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 422 The "visual cliff" phenomenon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 422

Vision and posture ............................................... 423 Moving visual scenes ........................................... 424 Visual acuity .................................................. 424 Near vision and eye-object distance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 425 Visual contral of fore-aft versus lateral body sway .................. 426 Visual stabilisation in the dark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 426 Flicker illumination ............................................ 426 Visual field .................................................... 427 Eye movements, oculomotor dis orders, and postural balance. . . . . . . .. 428 Nystagmus with oscillopsia impairs balance ....................... 428 Extraocular muscle paresis impairs locomotion and balance ......... 429

Oscillopsia ...................................................... 430 Oscillopsia is smaller than retinal image slip: deficient

vestibulo-ocular reflex ....................................... 431

Contents xxi

Acquired ocular oscillations with oscillopsia . . . . . . . . . . . . . . . . . . . . . .. 432 Physiologieal impairment of motion perception with moving eyes .. .. 433 Normal (physiologieal) inhibitory interactions between

self-motion and object-motion perception . . . . . . . . . . . . . . . . . . . . . .. 435 Pathologieal (adaptive?) binocular impairment of motion

perception caused by monocular external eye muscle paresis . . . . . .. 435 Oscillopsia and motion perception in congenital nystagmus ......... 435

References ........................................................ 436

30 Somatosensory vertigo ............................................. 441

Cervical vertigo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 441 Functional significance of neck afferents and neck reflexes. . . . . . . . . .. 442

Spatial orientation ........................................... 442 Neck reflexes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 443 Cervico-ocular reflex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 443 Central pathways ............................................ 443

Ataxia and nystagmus in experimental cervical vertigo . . . . . . . . . . . . .. 444 Clinieal evidence for cervieal vertigo? . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 444

Hypothetieal mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 445 Differential diagnosis ........................................ 446

Arthrokinetie nystagmus and self-motion sensation .................. 446 Other forms of nystagmus induced by non-vestibular stimulation .... 447 Postural imbalance with sensory polyneuropathy ................... 447

References ........................................................ 449

Section K Psychogenic vertigo ...................................... 453

31 Psychiatrie dis orders and vertigo .................................... 455

Organic versus psychiatrie morbidity ............................. 456 Vestibular dysfunction secondary to psychiatrie dis orders and

psychiatrie disorders secondary to vestibular dysfunction ......... 456 How can psychogenic vertigo be diagnosed? ....................... 457

Panic dis order ................................................... 458 Criteria for panic attack (DSM-IV 1994) ........................... 459

Agoraphobia .................................................... 459 Criteria for agoraphobia ........................................ 459

Epidemiology ............................................... 459 Management ................................................ 460

Acrophobia ...................................................... 460 Psychotherapy for acrophobia and agoraphobia .................... 461

Psychogenic disorders of stance and gait ............................ 461 Criteria for psychogenie disorders of stance and gait . . . . . . . . . . . . . . .. 462

Management ................................................ 463 References ........................................................ 466

32 Phobie postural vertigo

The clinieal syndrome

469

469

xxii Contents

Aetiology and hypothetical mechanism ............................. 470 Hypothetical mechanism: A disturbance of space constancy

due to decoupling of the efference-copy signal? . . . . . . . . . . . . . . . . . .. 471 Body sway in PPV .............................................. 472 PPV: A panic disorder? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 473 Differential diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 475

Course and treatment ............................................. 475 References ........................................................ 478

Section L Physiological vertigo ...................................... 481

33 Motion sickness ................................................... 485

The clinical syndrome ............................................ 485 Nausea and vomiting ............................................. 485 Labyrinth function and motion sickness ............................ 487 The sensory conflict theory (visual-vestibular mismatch) . . . . . . . . . . . . .. 487

Vestibular hyperexcitability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 489 Incidence and susceptibility ....................................... 490 Management: physical and medical prevention ....................... 491

Physical prevention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 491 Visual prevention of motion sickness in vehicles ................... 491 Medical prevention ............................................ 491

Space sickness ................................................... 492 References ........................................................ 493

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 497

Glossary

Acrophobia: fe ar of heights; when "physiologieal height vertigo" induces a conditioned phobie re action characterised by a dissociation of the objective and the subjective risk of falling.

Adaptation: the adjustment of a sensory system to its environment or the process by whieh this ability is achieved.

Agoraphobia: fear of wide open spaces or public places with excess anxiety, dizziness and postural imbalance.

Alternobaric vertigo: transient vertigo due to pressure changes in the middle ear whieh primarily affects divers and aircrew.

Antiemetics: drugs that control nausea and vomiting by acting on the medullary vom­iting centre, the chemoreceptor trigger zone, or the gastrointestinal tract itself.

Antivertiginous drugs: vestibular suppressants, including anticholinergics, antihista­mines, and benzodiazepines, which are used for symptomatic relief of distressing vertigo, nausea and vomiting by downregulating vestibular excitability.

Arthrokinetic nystagmus: a purely somatosensory nystagmus and illusion of self-motion with passive movements of the limbs in stationary subjects.

Barotrauma: signs and symptoms associated with exposure to alterations in ambient pressure, either an increase (diving, pressure chamber, explosions) or a decrease (fly­ing, altitude chamber), e.g. decompression sickness.

Basilar migraine: migrainous attacks with aura signs and symptoms within the ver­tebrobasilar territory.

Benign paroxysmal positioning vertigo (BPPV): most common form of vertigo caused by canalolithiasis of the posterior semicircular canal, less often of the horizontal or ante­rior semicircular canal.

Benign paroxysmal vertigo in childhood (BPV): recurrent episodie vertigo in childhood as a migraine equivalent. .

Benign recurrent vertigo (BRV): recurrent episodie vertigo as a migraine equivalent in adults.

Bilateral vestibular failure (BVF): bilateralloss of vestibular function with unsteadiness of gait in the dark and oscillopsia associated with head movements.

Buoyancy hypothesis: positional nystagmus and/or vertigo with specific gravity differ­ential between cupula and endolymph (e.g. positional alcohol nystagmus, positional heavy water nystagmus).

Canalolithiasis: benign paroxysmal positioning vertigo and nystagmus caused by free­floating heavy debris (otoconia) within the posterior or horizontal semicircular canal.

xxiv Glossary

Canal plugging: surgical plugging of single semicircular canals for treating canalolithi­asis in rare cases of benign paroxysmal positioning vertigo.

Cawthorne-Cooksey exercises: vestibular exercises for rehabilitation and promotion of vestibular compensation.

Cervical vertigo: to-and-fro vertigo and unsteadiness of gait induced by stimulation of, or lesions in, neck afferents.

Cireularveetionllinearveetion: optokinetically induced perception of apparent self­motion.

Cogan's syndrome: auto immune disease of young adults with interstitial keratitis and audio-vestibular symptoms.

Coriolis effeet: spatial disorientation (with nausea) through cross-coupled accelera­tions, when the head is undergoing a rotation about one axis and is tilted about a sec­ond axis.

Cortical astasia: lateral postural imbalance (lateropulsion) and tilts of perceived vertical with acute unilaterallesions of the parieto-insular vestibular cortex.

Cupulolithiasis: benign paroxysmal positional vertigo and nystagmus caused by heavy debris settled on the cupula of the semicircular canal, transforming it from a trans­ducer of angular acceleration into a transducer of linear acceleration.

Delayed endolymphatic hydrops: acquired types of endolymphatic hydrops which are sometimes separated from "idiopathic" Meniere's disease.

Dix and Hallpike manoeuvre: positioning of patients with benign paroxysmal positioning vertigo into a head-hanging position with the head turned.

Dizziness and light-headedness: typical presyncopal symptoms with orthostatic hypoten­sion or cardiac arrhythmias, which also occur with hyperventilation syndrome, panic attacks, metabolic hypoglycaemia, or drug intoxication.

Downbeat nystagmus: central disorder of the vertical vestibulo-ocular reflex in pitch plane with downbeat nystagmus, oscillopsia and fore-aft postural imbalance.

Endolymphatic hydrops: enlargement and distortion of the endolymphatic compart­ment due to insufficient fluid resorption in the endolymphatic sac or from blockage of the endolymphatic duct.

Epileptic nystagmus: ictal nystagmus induced by occipital or temporo-parieto-occipital epileptogenic foci involving the vestibular, visual, or ocular motor cortices.

Falls in the elderly: significantly increased risk of falls with increasing age because of multimorbidity and ageing.

Familial episodie ataxia type 1 (EA-l) or type 2 (EA-2): inherited channelopathies which manifest as recurrent ataxia with or without vertigo.

Fixation suppression of the vestibulo-ocular reflex: suppression of vestibular nystagmus during head acceleration by voluntary fixation of a stationary target.

Gait-ignition failure: inability to initiate and sustain locomotion with start-and-turn hesitation, shuffling, and freezing, but relatively normal gait once locomotion is initi­ated.

Habituation: the simplest form of learning with gradual adaptation to a stimulus or the environment, e.g. habituation to motion sickness stimuli on a ship within days.

Head-extension vertigo: physiological to-and-fro vertigo with head extension, particu­larIy with the eyes closed or when standing on an unstable support.

Glossary xxv

Height vertigo: physiological "distance vertigo" through visual destabilisation of pos­tural balance when the distance between the subject's eye and the visible stationary surroundings becomes critically large.

Hyperviscosity syndrome and vertigo: pathological hyperviscosity of the blood associated with polycythemia, hypergammaglobulinaemia, or Waldensträm's macroglobuli­naemia which may cause venous obstruction of the peripherallabyrinth.

Lateropulsion: irresistible lateral falls of patients with acute caudal brainstem lesions (e.g. Wallenberg's syndrome), vestibular thalamic lesions (thalamic astasia), or vestibular cortex lesions ("pusher syndrome").

Liberatory manouevres: rapid positionings of patients with benign paroxysmal posi­tioning vertigo (Brandt-Daroff exercises, Semont's manoeuvre, Epley's manoeuvre) designed to free the semicircular canal of the heavy dot formed during canalolithia­sis.

Mal de debarquement syndrome: persisting sensations of swinging, swaying, unsteadi­ness and disequilibrium experienced after sea travel immediately upon disembark­ing.

Meniere's disease: endolymphatic hydrops with the dassic triad of fluctuating hearing loss, tinnitus and episodic vertigo.

Mismatch concept: motion sickness or vertigo generated by an acute sensorimotor con­flict (mismatch between the converging sensory inputs or between the expected and actually perceived sensory pattern).

Mondini dysplasia: malformation of the membranous and osseous labyrinth with com­bined auditory and vestibulary loss.

Motion sickness: distressing syndrome with nausea and vomiting induced by unfamil­iar body accelerations in vehides to which the person has not adapted or by intersen­sory mismatch involving conflicting visual and vestibular stimuli.

Neural integrator or gaze-holding function: neural process that integrates velo city to posi­tion in order to hold gaze steady at the end of an eye movement in an eccentric posi­tion of the orbit when elastic forces tend to return it to primary position.

Ocular tilt reaction: disorder of the vestibulo-ocular reflex in roll; eye-head synkinesis consisting of lateral head tiIt, skew deviation, and ocular torsion; VOR-OTR with pon­tomedullary lesions of the vestibular nudei, which subserve the vestibulo-ocular reflex; integrator-OTR with lesions of the rostral midbrain integration centre for eye­head co ordination in roll plane.

Optokinetic motion sickness: symptoms of motion sickness when viewing large moving visual scenes (simulator sickness).

Oscillopsia: apparent movement of the visual scene due to involuntary retinal slip in patients with acquired ocular oscillations or deficient vestibulo-ocular reflex.

Otolithic vertigo: otolith dysfunction causing non-rotatory, to-and-fro vertigo associated with head acceleration and unsteadiness of gait, oscillopsia, perceived tiIt and ocular deviation.

Ototoxic agents: drugs and substances that transiently or permanently damage the cochlea or the vestibular labyrinth.

Paroxysmal dysarthria/ataxia: non-epileptic manifestation of paroxysmal attacks in mul­tiple sderosis by ephaptic activation of adjacent demyelinated axons.

xxvi Glossary

Perilymph fistula: rupture of the otie capsule, usually at the oval or the round window, whieh causes perilymph leakage and abnormal transfer of pressure changes.

Phobie postural vertigo: frequent psychosomatie postural vertigo with unsteadiness of gait distinguishable from agoraphobia and acrophobia.

Pitch: sagittal plane of action of the vestibulo-ocular reflex with nead extension or flexion about the binaural horizontal y-axis.

Plastieity of the vestibular system: mechanisms including habituation and readjustment to new environmental conditions or central compensation and sensory substitution for vestibular deficits.

Positional alcohol nystagmus (PAN): direction-changing, positional nystagmus and ver­tigo as a result of alcohol intoxieation, secondary to specific gravity differential between cupula and endolymph (buoyancy hypothesis).

Positional vertigo: vertigo induced by changes in head position relative to the gravita­tional vector; in positioning vertigo head movement rather than head position is the precipitating factor.

Positioning vomiting: vestibulo-autonomie central positioning vomiting due to lesions between the vestibular nuclei and the archicerebellar vermis.

Pressure fistula test: also known as the Hennebert sign; when pressure changes within the external auditory canal evoke ocular deviation, nystagmus, oscillopsia, vertigo, or postural imbalance in patients with perilymph fistula.

Purkinje effect: tumbling sensation of turning about an off-vertical body axis when the head is tilted during a post-rotational semicircular canal response.

Ramsay Hunt syndrome: herpes zoster otieus.

Roll: frontal plane of action of the vestibulo-ocular reflex with head motion in roll about the line of sight (x-axis).

Room-tilt illusion: transient upside-down vision or 90° tilt due to an acute vestibular tone imbalance whieh elicits a transient cortieal mismatch between the visual and vestibular 3D-coordinate maps.

Rotational vertebral artery occlusion: transient ischemic attacks with vertigo, nystagmus, and ataxia secondary to vertebral artery compression with rotation al head motion.

Rotatory vertigo: vertigo occurring with acute unilateral peripheralloss of vestibular function, pontomedullary brainstem lesions near the vestibular nuclei, or paroxysmal stimulation of these structures.

Scheibe syndrome: cochleo-saccular malformation with sparing of the semicircular canals and the utricle.

Semicircular canal vertigo: typieal signs and symptoms of which are rotational vertigo and deviation of perceived straight-ahead, spontaneous vestibular nystagmus with oscillopsia, postural imbalance with Romberg fall, and nausea and vomiting if severe.

Senile gait: cautious gait of older people.

Simulator siekness: motion sickness elicited in high-fidelity visual simulators or virtual environment systems.

Skew deviation (skew-torsion sign): vertical misalignment of the visual axes due to a grav­ieeptive vestibular tone imbalance in roll plane.

Space constancy mechanism: adequate perception of a stable world despite visual motion stimulation, eye-head motion, or locomotion.

Glossary xxvii

Space sickness: motion sickness in microgravitational environments elicited by head movements.

Spatial hemineglect: impairment of focal visuo-spatial attention toward the contralater­al side of lesions of the inferior parietallobule or frontal premotor cortex, also involv­ing the vestibular system.

Thalamic astasia: lateral postural imbalance (lateropulsion) in acute vestibular thalamic lesions without motor weakness, sensory loss, or cerebellar signs.

Traumatic otolithic vertigo: traumatic dislocation of otoconias resulting in unequalloads on the macular beds and causing transient head motion intolerance (oscillopsia and postural imbalance).

Tullio phenomenon: pathological sound-induced vestibular signs and symptoms in patients with perilymph fistula.

Tumarkin's otolithic crisis: vestibular drop attacks in Meniere's disease.

Upbeat nystagmus: central dis order of the vertical vestibulo-ocular reflex in pitch with upbeat nystagmus, oscillopsia, and postural imbalance.

Vascular fistula test: test for bilateral compression of the jugular vein which causes eye movements or vertigo in patients with perilymph fistula.

Vestibular atelectasis: collapse of the walls of the ampulla and utricle with unilateral or bilateral vestibular dysfunction.

Vestibular compensation: central readjustment of a lesion-induced vestibular tone imbalance; it consists of multiple processes for perceptual, vestibulo-ocular, and vestibulospinal readjustments, which have different time courses and occur at differ­ent sites in the brain and spinal cord.

Vestibular cortex: multiple multisensory temporoparietal cortex areas including the parieto-insular vestibular cortex, areas 2v, 3aV, 6, and 7.

Vestibular drop attacks: sudden falls due to vestibulospinalloss of postural tone caused by inadequate otolithic stimulation in Meniere's disease.

Vestibular epilepsy: episodic vertigo secondary to focal discharges from the vestibular cortex.

Vestibular exercises: physical therapy for vestibular rehabilitation to readjust vestibulo­ocular and vestibulospinal reflexes or to promote central habituation so as to prevent motion sickness.

Vestibular falls: peripheral or central vestibular dysfunction causing irresistible or unexpected falls.

Vestibular neurectomy: transeetion of the vestibular nerve in rare cases of intractable labyrinthine vertigo, particularly in severe cases of Meniere's disease.

Vestibular neuritis (VN): acute partial unilateral vestibular loss due to inflammation of the vestibular nerve with rotatory vertigo, nystagmus, postural imbalance, nausea and vomiting.

Vestibular paroxysmia (disabling positional vertigo): paroxysmal vertigo, oscillopsia, tin­nitus and postural imbalance due to neurovascular cross-compression of the VIIIth nerve.

Vestibular substitution: process by which parts of the missing vestibular inputs for, e.g. perceptual, ocular motor, and postural control are substituted by vision or cervical proprioception.

xxviii Glossary

Vestibulo-autonomie regulation: functions involving respiratory and cardiovascular con­tral with changes in body position, affective and emotional responses with body accelerations, nausea and vomiting, and modulation of sleep.

Vestibulocollie reflex (VCR): a three-neuron reflex arc from vestibular afferents to neck motor neurons to stabilise the head position in space.

Vestibulogenic epilepsy: variety of seizures induced by vestibular stimulation or dys­function.

Vestibulo-ocular reflex (VOR): a three-neuron reflex arc that serves to hold constant the direction of gaze in space during head movements by moving the eyes in the direc­tion opposite to that of the head with a velocity and amplitude wh ich compensate for the head motion.

Vestibulospinal reflexes: phasic and tonic reflexes that stabilise head and upright posture in relation to gravity via mediation of lateral vestibulospinal, medial vestibulospinal, and reticulospinal tracts.

Visual cliff phenomenon: innate visual depth avoidance without former experience of falling off edges.

Visual vertigo: spatial disorientation, misperception of motion, and postural imbalance induced by unusual visual stimulation or visual dysfunction.

Volvular epilepsy: rare ratatory seizures characterised by paroxysmal repetitive walking in small circles.

Wallenberg's syndrome: dorsolateral medullary infarction with involvement of the vestibular nuclei causing lateropulsion of the eyes and the body.

Yaw: horizontal plane of action of the vestibulo-ocular reflex with head rotations about the vertical z-axis.