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Myogenic potentials generated by a click-evoked vestibulocollic reflex
J G Colebatch1, G M Halmagyi, N F Skuse
1Department of Neurology, Prince of Wales Hospital, Randwick, Sydney, Australia.
Journal of Neurology, Neurosurgery, and Psychiatry
|February 1, 1994
Summary
Vestibular evoked myogenic potentials (VEMPs) from neck muscles reflect vestibular nerve activity. These potentials, specifically the p13-n23 response, are linked to the saccule and vestibular afferents, not hearing.
Area of Science:
- Neuroscience
- Otolaryngology
- Vestibular System Research
Background:
- Electromyograms (EMGs) provide insights into muscle activation.
- Auditory stimuli can elicit responses in non-auditory muscles.
- The role of vestibular and cochlear afferents in neck muscle responses is not fully elucidated.
Purpose of the Study:
- To investigate the origin of early and late electromyogram responses in sternomastoid muscles evoked by auditory clicks.
- To differentiate the contributions of vestibular and cochlear pathways to these evoked potentials.
Main Methods:
- Surface electromyograms (EMGs) were recorded from sternomastoid muscles.
- Averaged EMGs were elicited by brief auditory clicks at varying intensities.
- Responses were analyzed in normal subjects and patients with vestibular nerve section or sensorineural hearing loss.
Main Results:
- A consistent early biphasic potential (p13-n23) occurred at 8.2 ms latency, primarily from ipsilateral vestibular afferents.
- Later potentials (n34, p44) were generated bilaterally and were independent of vestibular nerve integrity.
- The amplitude of responses correlated with tonic muscle activation.
Conclusions:
- The early p13-n23 response is proposed to originate from vestibular afferents, likely from the saccule.
- This vestibular-mediated response is transmitted via a rapid pathway to neck muscles.
- Later potentials (n34, p44) are likely cochlear in origin, independent of the vestibular nerve.