Accessory nerve stimulation: motor response of the sternocleidomastoid muscle.
OBJECTIVE
The aim of this study is to describe a method for recording compound muscle action potential (CMAP) from the sternocleidomastoid (SCM) in response to accessory-nerve stimulation.


METHODS
Fifty-four subjects were included. Accessory nerve was stimulated at neck in two different positions; CMAPs were recorded with surface electrodes. Motor amplitude, area, duration, distal latency and intensity of stimulation at different sites were evaluated.


RESULTS
CMAPs were evoked in every subject. We did not observe interside differences or variations related to age. Stimulation behind SCM evoked CMAPs with slightly shorter latencies and with less stimulus intensity.


CONCLUSIONS
CMAPs of the SCM can be easily obtained by accessory nerve stimulation at the neck; this method allows a better determination of the accessory nerve lesion site. In addition, this method can be useful in the evaluation of patients with amyotrophic lateral sclerosis.
Pinto
S
S
Neuromuscular Unit, Faculty of Medicine, Institute of Molecular Medicine, University of Lisbon, Lisbon, Portugal.
de Carvalho
M
M
D000055:Accessory Nerve / Q000502:physiology*; D000200:Action Potentials / Q000502:physiology; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004558:Electric Stimulation; D004566:Electrodes; D004576:Electromyography; D004594:Electrophysiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009334:Neck Muscles / Q000294:innervation / Q000502:physiology*