Background: The cervical vestibular evoked myogenic potential (cVEMP) is recorded from the sternocleidomastoid
muscle (SCM) and represents a stimulus-evoked attenuation of electromyographic (EMG)
activity following activation of the saccule and inferior vestibular nerve. In addition
to the cVEMP, it is possible to record a biphasic response from the infraorbital region
following stimulation that is identical to that used to record the cVEMP. This response
is known as the ocular VEMP (oVEMP). The peripheral vestibular origins of the oVEMP
elicited with air conduction remain controversial as some investigators argue the
response originates from the saccule and others argue that the response emanates from
the utricle. We review several lines of evidence and present several case studies
supporting the contention that the oVEMP to air conduction stimulation derives its
peripheral origins predominately from the utricle and superior vestibular nerve.
Purpose: To review the current evidence regarding the peripheral origins of the oVEMP. Further,
a purpose of this report is to present case studies illustrating that the cVEMP and
oVEMP to air conduction stimulation may vary independently of one another in patients
with peripheral vestibular system impairments.
Research Design: A collection of case studies illustrating three common patterns of abnormality observed
in patients complaining of vertigo seen in a tertiary care referral center.
Study Sample: Retrospective analysis of data from three patients complaining of dizziness and/or
vertigo who have undergone vestibular function tests.
Results: Each case report illustrates a different pattern of abnormality of caloric, cVEMP,
and oVEMP tests results from three patients with a vestibular nerve section, superior
vestibular neuritis, and Ménière's disease, respectively.
Conclusions: We have shown that the cVEMP and oVEMP can vary independent of one another, and in
that way, provide topological information about the sites of impairment. We feel that,
with caloric, oVEMP, and cVEMP tests, it is possible to augment the diagnostic information
we are able to provide regarding the location, or locations, of vestibular system
impairment. These findings suggest that air conduction oVEMPs measure a part of the
peripheral vestibular system different from that measured by cVEMPs, perhaps the utricle,
and similar to that measured by caloric testing, the superior portion of the vestibular
nerve.
Key Words
Calorics - saccule - utricle - vestibular evoked myogenic potential
