Glycerol affects vestibular evoked myogenic potentials in Meniereʹs disease

Objectives: to show that abnormal vestibular evoked myogenic potentials on the sternocleidomastoid muscle (SCM) in patients with unilateral Meniereʹs disease are caused by endolymphatic hydrops. Subjects: six normal volunteers and 17 patients with unilateral Meniereʹs disease were examined. Methods: click-evoked myogenic potentials were recorded with surface electrodes over each SCM. Responses evoked by clicks recorded after oral administration of glycerol (1.3 g/kg body weight) were compared with those recorded before administration. Results: the change rate of the p13–n23 amplitude was calculated. The mean+standard deviation (S.D.) of the change rate was 3.52+14.6% in normal subjects. On the unaffected side of patients the change rates were within the normal range (within the mean±2S.D.) in 13 patients, and three ears showed significant decrease. Only one ear showed significant increase. On the affected side, five ears showed significant increase of the amplitude while two ears showed significant decrease after oral administration of glycerol. Effects on evoked myogenic potentials were independent of those on pure tone hearing. Conclusion:vestibular evoked myogenic potentials in some patients with unilateral Meniereʹs disease were improved by oral administration of glycerol. This result suggests that abnormal vestibular evoked myogenic potentials in patients with unilateral Meniereʹs disease could result from endolymphatic hydrops.