Carpal Tunnel Syndrome; Ultrasonographic and Electrodiagnostic Studies.

We studied thirteen hands of ten patients with carpal tunnel syndrome to elucidate the relationship between the degree of median nerve compression and distal motor latency. All patients underwent ultrasonographic and electrodiagnostic studies prior to operation. Intracarpal thickness of two portions of median nerve, proximal (A) and distal (B) to the position of carpal transverse ligament, were measured by ultrasonography, and the median nerve compression ratio was given by B/A. It was demonstrated that, in proportion to the degree of median nerve compression, there was a significant increase in distal motor latency of the damaged nerve.