Click음으로 유발된 전정-경반사의 근유발전위

Abstract

Background and Objectives: Click sound can evoke myogenic potentials in active sternocleidomastoid(SCM) muscle. These potentials are due to the activity of the vestibular rather than cochlear afferents, which produce very short latency inhibition of ipsilateral motor unit activity and is best detected by averaging the unrectified surface electromyogram(EMG) from the muscle. We investigated the click evoked vestibulocollic reflexes in neck muscles to find out the significance and relationship of latency and amplitude of myogenic potentials between two different methods of muscle activation. Methods: EMGs were recorded from surface electrode evoked by sound stimuli (95dB, 5/sec repetitive rate, 512 times) over SCM muscles on each side. Myogenic potential have two biphasic responses, which are termed P1, N1, P2 and N2 based on the polarity of their components. The subjects were 24 normal volunteers. Surface EMG activities from 12 subjects(Group I) were recorded by neck flexion to activate bilateral SCM muscles through the averaging runs(bilateral SCM muscle activation method). EMGs from another 12 subjects(Group II) were recorded by rotating head to the opposite side to activate SCM muscle throughout the procedure(unilateral SCM muscle activation method). The latencies and amplitudes of myogenic potential in the SCM muscle after stimulation were analysed and compared between each method. Results: The latencies(msec) of P1 and N1 were 11.2+2.4, 21.7+1.1 in Group 1, respectively and 13.3+2.4, 23.0±1.1 in Group 11, respectively. The amplitudes(μV) of P1-N1 were 38.7+8.1 in Group 1 and 33.2+8.1 in Group II. There was no significant difference in latencies and amplitudes of P1 and N1 between each group(p>0.05) and was no asymmetry of latency and amplitude in P1-N1 between each side. Conclusions: The myogenic potential was constantly evoked by click stimulation and we think it could be a simple method of examining vestibulocollic reflex.