[Electrophysiological diagnosis of neurogenic thoracic outlet syndrome]

The neurogenic thoracic outlet syndrome includes the symptoms caused by the compression of the brachial plexus at some point between the interscalene triangle and the inferior border of the axilla. Five patients diagnosed as having neurogenic thoracic outlet syndrome were examined. We determinated clinical and electrophysiological features which lead to thoracic outlet syndrome diagnosis. The clinical features included paresthesia and pain along the inner part of the arm, forearm and hand. Diminished sensation was rare. Muscle weakness was usual and muscle atrophy was associated in severe cases. The association with a lower cervical rib was useful. Electrodiagnostic studies always showed abnormalities. Electromyographic studies showed a reduced recruitment pattern of motor unit activation in intrinsic hand muscles. The medial antebrachial cutaneous nerve action potential amplitude was low. Nerve conduction studies also showed loss of amplitude of the ulnar sensory and median motor responses.