Delayed vestibular evoked responses to the eyes and neck in a patient with an isolated brainstem lesion

Objective: Two recently described tests of the vestibular system, vestibular evoked myogenic potentials (VEMPs) and ocular vestibular evoked myogenic potentials (OVEMPs), test the descending and ascending vestibular brainstem pathways, respectively. We describe a case of a patient in whom these investigations localised the lesion and suggested its nature. Methods: VEMPs (to clicks and short duration galvanic stimulation) and OVEMPs (to clicks) were recorded. Results: Click- and galvanic-evoked VEMPs were delayed on the left side (by similar to 5-6 ms), and click-evoked OVEMPs were similarly delayed (by similar to 4 ms) following left-sided stimulation. Repeat testing 21 months later showed partial resolution. Conclusions: The observed delays in evoked potentials suggested a demyelinating lesion. Furthermore, the similarity in delayed responses to neck and extraocular muscles was suggestive of a lesion at the root entry zone of the vestibulocochlear nerve. Significance: VEMPs and OVEMPS may thus provide information about the location and nature of lesions affecting central vestibular pathways. (C) 2007 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.