Short tone burst-evoked myogenic potentials on the sternocleidomastoid muscle: are these potentials also of vestibular origin?
OBJECTIVE
To show that short tone bursts (STBs) evoke myogenic potentials from the sternocleidomastoid muscle (SCM) that are of vestibular origin.


METHODS
Evoked potential activity was recorded from the SCMs of normal volunteers and from patients with vestibulocochlear disorders.


METHODS
This outpatient study was conducted at the Department of Otolaryngology, University of Tokyo, Tokyo, Japan.


METHODS
Nine normal volunteers and 30 patients (34 affected ears) with vestibulocochlear disorders were examined.


METHODS
Diagnostic.


METHODS
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.


CONCLUSIONS
Short tone bursts as well as clicks can evoke myogenic potentials from the SCM. Myogenic potentials evoked by STBs are also probably of vestibular origin.
Murofushi
T
T
Department of Otolaryngology, University of Tokyo, Japan. toshi-tky@umin.ac.jp
Matsuzaki
M
M
Wu
C H
CH
D000161:Acoustic Stimulation / Q000379:methods; D000328:Adult; D000368:Aged; D015834:Cochlear Diseases / Q000503:physiopathology; D004576:Electromyography / Q000379:methods / Q000706:statistics & numerical data; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009334:Neck Muscles / Q000502:physiology*; D012016:Reference Values; D015837:Vestibular Diseases / Q000503:physiopathology; D014725:Vestibular Nerve / Q000502:physiology*