EMG SPIKE TRAINS OF SUCCINYLCHOLINE-INDUCED FASCICULATIONS IN MYALGICPATIENTS

Single spike activity from the surface electromyogram (EMG) of fascicu lations induced by succinylcholine (Sch) were studied from limb muscle s (biceps, triceps, anterior tibialis and gastrocnemius) in 100 female patients. About 2/3 of them (n = 72) also received nondepolarizing ne uromuscular pretreatment (atracurium or vecuronium). We observed from 20% of EMG records in the myalgic (but not in the nonmyalgic) patients , sustained spike trains (mean duration 1.47 s) that resembled motor u nits firing at physiologically high rates (mean 21.7 spikes/s). The fi nding reflects Sch's distal actions at the muscle spindle. The implica tions for myalgia and the possible involvement of micro damage at the extrafusal muscles are discussed.