Vestibular click-evoked myogenic potentials: sensitivity and factors determining abnormality in patients with multiple sclerosis.

Vestibular evoked myogenic potential (VEMP) assesses the sacculo-spinal pathway. The aim of our study was to examine sensitivity and factors determining abnormality of VEMP, indicative of brainstem dysfunction, in patients with multiple sclerosis (MS). Thirty healthy subjects and 30 MS patients were examined. All healthy subjects showed a normal biphasic response. Twelve of the 30 MS patients (40%) had abnormal recordings. There was a significant difference between MS patients and control subjects with respect to P13 latency (longer in the MS group) and P13-N23 amplitude (lower in the MS group). VEMP abnormalities were statistically significantly related to the presence of brainstem demyelinative lesions and a weaker correlation was found with disease duration. Clinical signs of vestibular dysfunction at any point during the course of the disease did not seem to affect the chances of obtaining abnormal VEMPs. Although the sensitivity of VEMP in detecting abnormality in MS patients is relatively low, its significance is evident in that it is the only electrophysiological method that is able to detect dysfunction in central vestibular pathways.