Click-evoked cervical myogenic potential in humans

Colebatch and Halmagyi (1992) reported that human average evoked myogenic potential in response to clicks shows a characteristic short- latency positivity-negativity, and that this is abolished by selective vestibular neurectomy. Therefore, this click-evoked myogenic potential is thought to be due to vestibulo-collic reflex, and expected to respond to a new vestibular test. We have examined this response in healthy normal subjects and patients with neurotological disease since 1994, and will discuss these cases to evaluate the significance of this test. In normal subjects, the myogenic potential to the click in the unilateral car, whose peak latency of positive and negative wave were averaged at 13.6 and 23.0 msec, respectively, was found ipsilaterally. In addition, averaged threshold of the potential was 87 dB. Wave form and peak latency of myogenic potential were similar on each side. In patients with profound hearing loss and normal caloric response, the myogenic potential was present. However, in patients with moderate hearing loss and no caloric response, the myogenic potential was lost. These findings suggest that the click-evoked short-latency myogenic potential may originate not from the cochlear but vestibular end organ.