Table Of Content⋅
Toshihisa Murofushi Kimitaka Kaga
Vestibular Evoked Myogenic Potential
Its Basics and Clinical Applications
PR.indd I 11/19/2008 9:35:32AM
⋅
Toshihisa Murofushi Kimitaka Kaga
Vestibular Evoked Myogenic
Potential
Its Basics and Clinical Applications
Toshihisa Murofushi, M.D., Ph.D. Kimitaka Kaga, M.D., Ph.D.
Professor Director
Department of Otolaryngology National Institute of Sensory Organs
Teikyo University School of Medicine National Tokyo Medical Center
University Hospital, Mizonokuchi 2-5-1 Higashigaoka, Meguro-ku,
3-8-3 Mizonokuchi, Takatsu-ku, Tokyo 152-8902, Japan
Kawasaki 213-8507, Japan
Library of Congress Control Number: 2008938811
ISBN 978-4-431-85907-9 Springer Tokyo Berlin Heidelberg New York
e-ISBN 978-4-431-85908-6
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Preface
The vestibular labyrinth consists of fi ve compartments: the lateral, anterior, and
posterior semicircular canals, the utricule, and the saccule. At the beginning of
the twentieth century, Robert Bárány proposed the caloric test as a clinical test of
the lateral semicircular canal. This test enabled clinicians to assess the individual
lateral semicircular canal function easily by using the simple method of irrigating
the external ear canal with cold or warm water and observing the induced nystag-
mus. We believe that the caloric test was a breakthrough in the fi eld of
vestibular research. However, as far as the other compartments were concerned,
there was no simple clinical test equal to the caloric test for the lateral semicircular
canal function.
At the end of the twentieth century, the vestibular evoked myogenic potential
(VEMP) test was proposed as a new method for assessing the individual saccule
function. This test has some unique attributes. First, it uses sound stimulation, even
though it is a test of the vestibular system. This appears to be a contradiction neu-
rophysiologically. As a result, in its early stages there were controversies concern-
ing the origin of the responses. However, such controversies have been overcome
by basic neurophysiological studies and clinical studies. Above all, sound sensitiv-
ity of the saccular afferents shown in cats and guinea pigs with single-unit recording
methods became the main supporting evidence. Nowadays, VEMP is one of the
routine clinical tests for balance disorder.
Second, the sternocleidomastoid muscle (SCM), the conventional recording
site of VEMP, is itself special. While saccular afferents project onto the ipsi-
lateral motoneurons of the SCM, they do not project onto the contralateral
motoneurons of the SCM. This fact enables us to assess the individual saccule
function easily. Third, the VEMP test provides totally different information than
the caloric test does. Whereas the VEMP test is a test of the otolith organs, the
caloric test is a test of the semicircular canals; and whereas the VEMP test is a
test of the inferior vestibular nerve, the caloric test is a test of the superior
vestibular nerve. Evidently, these two, the caloric test and the VEMP test, can
coexist.
V
VI Preface
This book is a review of VEMP studies. Readers will obtain full knowledge
of the principles of the elicited response, methods of recording, and clinical
applications. We hope to generate more interest among clinicians and scientists
in VEMP and to provide greater knowledge of vestibular disorders through this
publication.
19 October 2008
Toshihisa Murofushi, Kimitaka Kaga
Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V
Part I. Introduction Toshihisa Murofushi . . . . . . . . . . . . . . . . . . . . . . . . 1
Part II. Basics Toshihisa Murofushi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Overview of the Vestibular System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Sound Sensitivity of the Vestibular End-Organs and Sound-Evoked
Vestibulocollic Refl exes in Mammals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Recording and Assessing VEMPs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
VEMP Variants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Part III. Clinical Applications Toshihisa Murofushi . . . . . . . . . . . . . . 47
Meniere’s Disease and Related Disorders: Detection of Saccular
Endolymphatic Hydrops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Vestibular Neuritis (Neurolabyrinthitis) and Other Peripheral
Vestibulopathies: Detection of Inferior Vestibular Nerve Damage . . . . . 60
Superior Canal Dehiscence Syndrome and VEMPs:
Detection of Hypersensitivity of the Vestibular System to Sound . . . . . . 73
Migraine-Associated Vertigo and VEMPs: Detection of Vestibular
Signs in a Common but Unclear Entity . . . . . . . . . . . . . . . . . . . . . . . . . . 78
Acoustic Neuroma and Other Cerebellopontine Angle Tumors:
Detecting a Neoplasm in the Cerebellopontine Angle . . . . . . . . . . . . . . . 83
Disorders of the Central Nervous System and VEMPs:
Detecting Lesions in the Vestibulospinal Pathway . . . . . . . . . . . . . . . . . . 92
Part IV. Pediatric Applications Kimitaka Kaga . . . . . . . . . . . . . . . . . . 99
Neurootological Application of VEMP Recording During Infancy
and Childhood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
VII
Part I
Introduction
Introduction
Vestibular evoked myogenic potentials (VEMP) are responses in the muscles,
especially cervical muscles such as the sternocleidomastoid muscle (SCM), to
sound, vibration, or electrical stimulation (Fig. 1). Because it seemed that VEMP
could be used for clinical tests of the vestibular end-organs, especially the saccule,
it attracted the interest of clinicians and scientists. There had been no other clinical
test of the saccule that was applicable at common clinics. Now much has been
published about VEMP, and many clinicians use this test. VEMP is one of the most
important advances in clinical neurophysiology of the vestibular system.
Prior to the availability of VEMP in its present form [1], other tests had been
proposed, such as using inion responses [2, 3] (Fig. 2), which tried to measure
potentials evoked by sound as a test of the vestibular system. However, tests relying
on these responses were not widely used at clinics. VEMP in its present form,
utilizing biphasic myogenic potentials on the SCM, were fi rst reported in 1992 by
Colebatch and Halmagyi, who reported that VEMP responses on the affected side
disappeared after unilateral vestibular nerve section despite preservation of hearing
[1, 4] (Fig. 3). Colebatch et al. reported in 1994 that VEMP could be recorded in
a patient with bilateral near-total hearing loss [4]. Since that report, clinical and
basic studies concerning VEMP have been further developed. These later studies
clarifi ed that the major vestibular end-organ which responds to sound is the saccule,
and that signals are conveyed via the inferior vestibular nerve [5–11]. Details are
given in the chapters that follow. Here, we want to emphasize that the progress
achieved in this fi eld was brought about by the collaboration of scientists and
clinicians.
Vestibular Evoked Myogenic Potential: Its Basics and Clinical Applications. 3
Toshihisa Murofushi and Kimitaka Kaga
doi: 10.1007/ 978-4-431-85908-6_1, © Springer 2009
4 Vestibular Evoked Myogenic Potentials
n23
n34
p44
p13
(cid:2)
click
100 mV
10 msec
Fig. 1. A typical waveform of vestibular evoked myogenic potentials (VEMP) in a healthy
subject
Fig. 2. A typical waveform of inion responses. An active electrode was placed on the nasion and
a reference electrode was on the mastoid. 70dBnHL clicks were presented binaurally; 150
responses were averaged. (From [3], with permission)
