Serial SFEMG studies of orbicularis oculi muscle after the first administration of botulinum toxin

Serial single fiber electromyography (SFEMG) examinations of orbicularis oc uli muscle in patients with blepharospasm or hemifacial spasm treated with botulinum toxin injections were performed. The aim of the study was to eval uate the impairment of neuromuscular transmission, to follow reinervation a fter botulinum toxin administration and to find out whether there was a rel ationship between SFEMG parameters and clinical symptoms. Examinations were performed before injection, during early and late remission of symptoms, a nd after recurrence of the involuntary movement. Severe impairment of neuro muscular transmission, as revealed by increased jitter and increased presen ce of abnormal potential pairs and pairs with blocking, was found in early remission, but fiber density remained unchanged when compared with pretreat ment values. In late remission, increased fiber density was registered for the first time. The recurrence of involuntary movements was related to the further increase of fiber density and tendency to normalization of jitter p arameters. The study therefore suggests that formation of new neuromuscular junctions and their functional maturation is responsible for muscle recove ry after botulinum toxin administration, Eur J Neurol 6:461-467 (C) 1999 Li ppincott Williams & Wilkins.