cVEMP morphology changes with recording electrode position but single motor unit activity remains constant
Abstract
Cervical vestibular evoked myogenic potentials (cVEMPs) recorded over the lower quarter of the sternocleidomastoid (SCM) muscle in normal subjects may have opposite polarity to those recorded over the midpoint. It has thus been suggested that vestibular projections to the lower part of SCM might be excitatory rather than inhibitory. We therefore tested the hypothesis that the SCM muscle receives both inhibitory and excitatory vestibular inputs. We recorded cVEMPs in 10 normal subjects with surface electrodes placed at multiple sites along the anterior (sternal) component of the SCM muscle. We compared several reference sites: sternum, ipsilateral and contralateral earlobes and contralateral wrist. In five subjects, single motor unit responses were recorded at the upper, middle and lower parts of the SCM muscle using concentric needle electrodes. The surface cVEMP had the typical positive-negative polarity at midpoint of the SCM muscle. In all subjects, as the recording electrode was moved toward each insertion point, p13 amplitude became smaller and p13 latency increased, then the polarity inverted to a negative-positive waveform (n1-p1). Changing the reference site did not affect reflex polarity. There was a significant short-...Continue Reading
References
Motor unit excitability changes mediating vestibulocollic reflexes in the sternocleidomastoid muscle
Citations
Related Concepts
Related Feeds
Cardiac Conduction System
The cardiac conduction system is a specialized tract of myocardial cells responsible for maintaining normal cardiac rhythm. Discover the latest research on the cardiac conduction system here.