PALMARIS BREVIS SPASM SYNDROME

Palmaris brevis spasm syndrome is a rare and benign condition of local ised muscular hyperactivity. In five men, the hypothenar eminence unde rwent spontaneous, irregular, tonic contractions of the palmaris brevi s muscle. An EMG showed spontaneous high frequency discharges of norma l motor units, without evidence of neuropathy or of nerve compression. This syndrome resembles other restricted muscle hyperactivity syndrom es although there are some differences. Curiously, the palmaris brevis muscle is not under voluntary control. The mechanism of the syndrome could be an ephaptic transmission possibly secondary to the transient and repeated stretching of the ulnar nerve superficial branch. In one patient a root compression was the probable origin.