The effect of treatment on median nerve conduction in patients with the carpal tunnel syndrome. Ann. phys

SLOWING of nerve conduction in patients with the carpal tunnel syndrome was first reported by Simpson in 1956. When the median nerve was stimulated at the wrist and the muscle response recorded from the abductor pollicis brevis, it was found that the latency of the muscle action potential was significantly increased, the abnormality being reversed by surgical division of the flexor retinaculum. In the same year that Simpson published his investigation of motor latency, Dawson (1956) described a method of recording action potentials from the median and ulnar nerves at the wrist when the sensory fibres in the fingers were stimulated. Small ring electrodes were wrapped round the fingers to stimulate digital nerve fibres, and nerve action potentials were recorded by means of surface electrodes placed over the median or ulnar nerve trunks just above the wrist. Using this technique, it was subsequently shown by Gilliatt and Sears (1958) that median nerve action potentials might be delayed or lost altogether in patients with the carpal tunnel syndrome. These observations suggested that the examination of nerve conduction could provide an accurate and objective method of assessing the degree of nerve damage in patients with the carpal tunnel syndrome. It was therefore decided to study a group of patients both before and after surgical division of the flexor retinaculum in order to discover whether abnormalities of nerve conduction would resolve completely after surgery, and, if so, after what interval. For this purpose it wa