Vestibular-evoked myogenic potentials as a test of otolith function.

OBJECTIVES To evaluate the use of 75 auditory clicks rather than the usual 100-256 for production of the vestibular-evoked myogenic potential (VEMP) response and to assess if the VEMP correlates with measures of cochlear function such as hearing loss (decibels on pure-tone testing) or auditory brainstem response (ABR). SUBJECTS AND METHODS Testing of the VEMP was carried out on 24 subjects: 7 normal individuals and 13 hard-of-hearing patients, 2 patients with known vestibular lesions, 1 with profound sensorineural hearing loss and 1 patient with unilateral acoustic neuroma prior to resection. The recording was performed using a conventional ABR machine. Using 75 refraction clicks as auditory stimuli, VEMP responses were measured from a surface electrode applied to the sternocleidomastoid muscle. The 75 responses were averaged. RESULTS A consistent unilateral biphasic response, the first negative and the second positive (nI, pII), was elicited from 39 of 40 ears (7 normal and 13 hard-of-hearing subjects with no known vestibular dysfunction). No statistical difference was found between the right and left ear responses for nI or pII wave latencies. Two patients with loss of peripheral vestibular function showed no VEMP responses on the affected side. The responses, however, were elicited bilaterally in a patient with congenital profound sensorineural hearing loss. In addition, ABR latencies did not correlate with VEMP latencies. CONCLUSION Clear VEMP responses were elicited by using only 75 auditory clicks. This shortens the testing time and facilitates the procedure for the tested subject. Our data also indicate that the VEMP is generated secondary to auditory stimulation of the vestibular end organs (specifically the saccule) and does not correlate with cochlear function.