[Study of click-induced vestibule-sternocleidomastoid reflex recorded with surface electromyography]

The otolithic organs serve to control posture and maintain the visual objective during linear accelerations. Recent experimental research in man and animals has suggested that it may be possible to explore the function of these organs by studying the vestibule-sternocleidomastoid reflex induced by high intensity clicks. The aim of the present work was to identify the parameters which are most reproducible in normal subjects and, therefore, best suited to this purpose. The instrument normally used to study evoked auditory potentials (ERA) was used to perform an electromyographic recording at the surface of the sternocleidomastoid muscle (SCM) and then average the electromyographic response to short clicks (0.1 ms) introduced through the headphones. In normal subjects clicks at an intensity of 85-100 dB HL evoked a reproducible electromyographic response in the venter of the SCM muscle with an average latency of 8.75 ms. The latency parameter proved to present the most suitable characteristics for possible clinical use. The possibility of using this method to study human vestibular lesions is certainly enticing although further research is needed to better characterize the precise site of origin for the vestibule-sternocleidomastoid reflex.