Short-latency EMG potentials elicited by head taps in sternocleidomastoid muscles: a study on normal human subjects and patients with central or vestibular lesions.

The aim of the present study was to determine whether a tap on the forehead evokes a vestibulospinal reflex in sternocleidomastoid muscles in normal human subjects and patients with central or vestibular lesions. While first positive-negative short-latency EMG potentials with a mean positive potential peak of about 12 ms and a mean negative potential peak of about 17 ms were found in the bilateral sternocleidomastoid muscles in normal subjects, they disappeared or were attenuated in patients with central or peripheral vestibular lesions.