Anterior interosseous nerve syndromes. Diagnostic methods and alternative treatments.

Electromyographic and nerve conduction studies on 46 normal controls (12 men and 34 women, aged 9 to 67 years) are compared with findings in seven patients (three men and four women, aged 9 to 60 years) with the anterior interosseous nerve (AIN) syndromes, including two patients with bilateral involvement (the first such reported cases, to our knowledge). Routine motor and sensory nerve conduction studies of the radial, median, and ulnar nerves show no difference between controls and patients. In 46 normal controls (84 different AIN studies), the latency and duration of the evoked action potential from elbow to pronator quadratus was 5.1 msec +/- 0.9 (95% confidence interval) and 3.6 msec +/- 1.1 (95% confidence interval), respectively. Five of the seven patients had abnormal latencies from elbow to pronator quadratus while all showed prolonged duration of the action potential. Electromyographic abnormalities of the pronator quadratus, flexor pollicis longus, and flexor digitorum profundi, as well as delayed motor latencies and prolonged duration of the evoked potential of the AIN from elbow to pronator quadratus provide sufficient information to diagnose the AIN syndrome. Surgical exploration may not be necessary unless there is evidence of a penetrating injury, significant entrapment, or certain fractures.