Vestibular Evoked Myogenic Potential: Recording Methods and Clinical Application

Only a few tests can evaluate the function of the saccule and inferior vestibular nerve. Vestibular-evoked myogenic potentials (VEMP) are inhibitory potentials recorded in the contracting muscles, usually in the sternocleidomastoids (SCM), when sound stimuli are applied. A disynaptic pathway originating in the saccule is known to mediate VEMP. The main pathway of saccule-induced inhibitory postsynaptic potentials to ipsilateral SCM motoneurons seems to be the medial vestibulospinal tract which descends within the medial longitudinal fasciculus. VEMP have been applied to determine saccular function in many disorders involving the peripheral vestibular apparatus. However, the characteristics and the diagnostic values of VEMP require further exploration in central vestibulopathies. In this review, the basic principles and recording methods of VEMP are overviewed. We will also review VEMP responses found in central as well as peripheral vestibular disorders. Despite several issues that need further elucidation, such as the exact neural pathway mediating VEMP, aging effects on VEMP, and normalization of the muscle contraction during the recording, VEMP allows us exclusive information on the function of saccule and its neural pathway, which cannot be provided by other vestibular function tests.