Short Tone Burst–Evoked Myogenic Potentials on the Sternocleidomastoid Muscle

Outcome measures: Sound-evoked myogenic potentials in response to STBs were recorded with surface electrodes over each SCM. Responses evoked by STBs in patients were compared with responses evoked by clicks. Results: In all normal subjects, STBs (0.5, 1, and 2 kHz) evoked biphasic responses on the SCM ipsilateral to the stimulated ear; the same was true for clicks. Short tone bursts of 0.5 kHz evoked the largest responses, while STBs of 2 kHz evoked the smallest. In patients with vestibulocochlear disorders, responses to STBs of 0.5 kHz were similar to responses evoked by clicks. Thirty (88%) of the 34 affected ears demonstrated the same results with 0.5-kHz STBs and with clicks. Responses were present in patients with total or near-total hearing loss and intact vestibular function. Conversely, patients with preserved hearing but with absent or severely decreased vestibular function had absent or significantly decreased myogenic potentials evoked by STBs.