Hemimasticatory spasm secondary to biopercular syndrome.

A 45-year-old male patient was evaluated because of involuntary spasms in his right masseter muscle. Five years before, following an acute respiratory insufficiency which required endotracheal intubation, he had presented with dysarthria, bilateral (predominantly right) supranuclear facial and hypoglossal palsy, and inability to achieve tongue protrusion, difficulty in chewing and bilateral dystonia of the hands. At that time, the case of this patient was published because of the presence of bilateral asymmetrical hand dystonia associated with bilateral opercular lesions (Foix-Marie-Chavany syndrome) [18] ; he did not have HMS and was lost to follow-up. Six months after the first admission to hospital (4.5 years before the new evaluation), he developed a progressive clinical picture of sustained involunHemimasticatory spasm (HMS) is an infrequent condition that consists of involuntary sustained unilateral contractions of masticatory muscles. After the first description by Gowers in 1897 as ‘masticatory spasm’ [1] , at least 19 additional cases of HMS have been reported ( table 1 ) [2–17] , some of them associated with facial hemiatrophy [2, 3, 6, 7, 9, 11– 13] . The characteristic electromyographic (EMG) findings of HMS are irregular bursts of motor unit potentials lasting from seconds to minutes, which correlate clinically with the involuntary twitches or spasms of the masticatory muscles [4, 10, 13] . Involuntary spasms are selectively confined to the masseter, temporalis and, occasionally, medial pterygoid muscles. The pathophysiology of HMS is not well known. Some authors suggested a close similarity with hemifacial spasm [2, 5] and proposed that the spontaneous activity was generated in the trigeminal nerve fibers [2, 4] . On the other hand, other authors suggested the central nervous system, sympathetic ganglia or muscle dysfunction [3, 7] . Some reports support the trigeminal nerve dysfunction hypothesis, by which ectopic activity of motor fibers of the trigeminal nerve should cause decreased motor nerve conduction of the Received: April 4, 2007 Accepted: July 12, 2007 Published online: February 8, 2008