Focal hand dystonia in a patient with thoracic outlet syndrome

A patient affected by thoracic outlet syndrome, with aninvolvement of the left lower primary trunk due to a rudimentarycervical rib, developed a severe hand dystonia on the same side. Thedystonic posture was characterised by a flexion of the wrist with thefingers curled into the palm. Polygraphic recordings performed on the left flexor digitorum superficialis (FDS4) and extensor digitorum superficialis (EDC4) muscles, during a repetitive tapping task of thefourth digit, showed a loss of well formed bursts without a clearsilent period along with long duration bursts of cocontraction inantagonistic muscles. The study of reciprocal inhibition between forearm flexor and extensor muscles showed a reduced amount of inhibition in both the disynaptic and the later presynaptic phase ofinhibition. The patient underwent an operation with resection of thecervical rib. Twelve hours after the operation the patient experienceda significant improvement of the hand dystonia; the distonia haddisappeared completely by two months with a progressive normalisationof reciprocal inhibition.