Galvanic-evoked myogenic responses in patients with an absence of click-evoked vestibulo-collic reflexes.
OBJECTIVE
To show that galvanic-evoked responses on the sternocleidomastoid muscle (SCM) are useful for differentiating labyrinthine lesions from retro-labyrinthine lesions in patients with an absence of click-evoked vestibulo-collic reflexes.


METHODS
We studied the average responses in the unrectified electromyographic (EMG) activities of the SCM to galvanic stimulation (3mA, 1ms). The cathodal electrode was on the mastoid, and the anodal electrode was on the forehead. Twenty-two healthy subjects and 28 patients with vestibular disorders were studied. All of the 28 patients showed the unilateral absence of vestibulo-collic reflexes evoked by 95dBnHL clicks on the affected side.


RESULTS
In healthy subjects mastoid-forehead galvanic stimulation produced a positive-negative biphasic EMG response at short latency on the SCM ipsilateral to the cathodal electrode. All patients with labyrinthine lesions showed biphasic EMG responses even in the affected side. In contrast, almost all patients with retro-labyrinthine lesions (16/18) showed no response or a decreased response on the affected side.


CONCLUSIONS
These results suggest that galvanic-evoked myogenic responses on the SCM may be useful in the differential diagnosis of labyrinthine lesions from retro-labyrinthine lesions in patients with an absence of vestibulo-collic reflexes evoked by clicks.
Murofushi
Toshihisa
T
Department of Otolaryngology, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Tokyo 113-8655, Japan. toshi-tky@umin.ac.jp
Takegoshi
Hideki
H
Ohki
Masafumi
M
Ozeki
Hidenori
H
D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D004576:Electromyography; D018159:Endolymphatic Hydrops / Q000503:physiopathology*; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009334:Neck Muscles / Q000294:innervation / Q000502:physiology*; D009464:Neuroma, Acoustic / Q000503:physiopathology*; D010037:Otolithic Membrane / Q000502:physiology; D012018:Reflex / Q000502:physiology; D014725:Vestibular Nerve / Q000503:physiopathology*