FOCAL HAND DYSTONIA IN A PATIENT WITH THORACIC OUTLET SYNDROME

A patient affected by thoracic outlet syndrome, with an involvement of the left lower primary trunk due to a rudimentary cervical rib, devel oped a severe hand dystonia on the same side. The dystonic posture was characterised by a flexion of the wrist with the fingers curled into the palm. Polygraphic recordings performed on the left flexor digitoru m superficialis (FDS4) and extensor digitorum superficialis (EDC4) mus cles, during a repetitive tapping task of the fourth digit, showed a l oss of well formed bursts without a clear silent period along with lon g duration bursts of cocontraction in antagonistic muscles. The study of reciprocal inhibition between forearm flexor and extensor muscles s howed a reduced amount of inhibition in both the disynaptic and the la ter presynaptic phase of inhibition. The patient underwent an operatio n with resection of the cervical rib. Twelve hours after the operation the patient experienced a significant improvement of the hand dystoni a; the distonia had disappeared completely by two months with a progre ssive normalisation of reciprocal inhibition.