Intraoperative changes in motor nerve conduction latency in carpal tunnel syndrome.

A prospective study of 47 patients with 51 hands treated for carpal tunnel syndrome by surgical release of the deep transverse carpal ligament was performed using intraoperative motor nerve conduction latency measured over a standard distance across the carpal tunnel both before and after release of the ligament. The results of intraoperative conduction latencies indicated a dramatic and immediate reduction in the conduction latency across the carpal canal in all but seven patients, two of whom had diabetes. When the results were subjected to statistical analysis, they were significant (P is equal to 0.00001). Although further studies are indicated, these data suggest that a rapidly reversible mechanical or metabolic block, such as ischemia in the segment of the median nerve, may be responsible for the symptoms of carpal tunnel syndrome.