Galvanic stimulation evokes short-latency EMG responses in sternocleidomastoid which are abolished by selective vestibular nerve section

Abstract

Objective: To describe vestibulocollic responses in sternocleidomastoid (SCM) evoked by transmastoid galvanic (DC) stimulation. Methods: We studied the averaged responses in the unrectified EMG of SCM to transmastoid galvanic stimulation (5 mA/2 ms) and also to 100 dB clicks. Two patients with Meniere's disease were studied both before and after unilateral selective vestibular nerve section. Results: Transmastoid galvanic stimulation produced a positive-negative biphasic EMG response at short latency in the SCM ipsilateral to the side of cathode placement, which resembled that which followed vestibular activation by loud clicks (p13/n23). Selective unilateral vestibular nerve section abolished this galvanic-evoked response. Conclusions: Galvanic-evoked vestibulocollic responses can be recorded in SCM. This is a new method of studying vestibular reflex function which may have application in the clinical assessment of vestibular disorders.