Ulnar neuropathy and dystonic flexion of the fourth and fifth digits: clinical correlation in musicians

Peripheral nerve lesions are sometimes associated with focal dystonia. We diagnosed ulnar neuropathy in 28 of 73 (40%) cases of occupational cramp in musicians. Focal slowing of ulnar conduction across the elbow was identified in 15 of 19 (79%) patients using the near nerve technique and in 5 of 17 (29%) patients using surface recording. Ulnar neuropathy was present in 24 of 31 (77%) cases with flexion dystonia of the fourth and fifth digits and only 4 of the remaining 42 (10%) cases with other patterns of focal dystonia. Focal dystonia improved in 13 of 14 patients whose ulnar neuropathy improved and appeared or worsened in 2 patients following ulnar nerve injury. These data, together with our recent observation of a dystonic pattern of antagonist bursting in patients with isolated ulnar neuropathy (Muscle Nerve 1995, 18:606-611), suggest that ulnar neuropathy may initiate or sustain a specific dystonia, flexion of the fourth and fifth digits, by inducing a central disorder of motor control.