Distal chronic spinal muscular atrophy involving the hands.

Six patients with a 10 to 30 year history of slowly progressive wasting and weakness of the small muscles of the hands have been studied. In all patients the abnormal neurological signs were largely confined to the hands and there was no clinical nor radiological evidence of peripheral nerve, nerve root or central nervous system disease. Detailed electrophysiological studies established that the muscle wasting was due to chronic partial denervation. Motor and sensory conduction studies were normal. These patients represent a benign form of chronic spinal muscular atrophy largely localised to the small muscles of the hand.