Vestibular evoked myogenic potentials in multiple sclerosis: a comparison between onset and definite cases.

Patients affected with multiple sclerosis (MS) frequently suffer from vestibular disorders due to vestibulospinal involvement. The vestibulospinal reflexes in these subjects can be well investigated through vestibular evoked myogenic potentials (VEMPs). Evoked by the acoustic stimulation of the saccular macula and mediated by the vestibulocollic reflex pathway, they are recorded using surface electromyographic electrodes from the ipsilateral sternocleidomastoid muscle tonically contracted. Abnormal findings (e.g., absence of response, prolonged latencies) disclose a lesion anywhere in the pathway. We examined VEMPs in 19 patients with definite MS (5 men, 14 women; age range, 31-59 years; mean age, 45 years) and compared them to VEMPs in 10 subjects with onset MS (2 men, 8 women; age range, 24-35 years; mean age, 29 years). VEMPs in definite MS subjects were abnormal in 14, absent (on the left side only) in 1, and normal in the remaining 4. In patients with onset MS, VEMPs were abnormal in 6. These results suggest that latencies of vestibulospinal reflexes can be remarkably delayed in MS at different stages of disease, whereas vestibulospinal involvement is more frequent in definite cases. To date, no study has yet investigated different VEMPs involvement at different stages of MS.