Digital nerve conduction in the carpal tunnel syndrome after mechanical stimulation of the finger.

Abstract

Conduction velocities of volleys in the digital nerves of 21 patients with carpal tunnel syndrome were comparedwith those of 29 control subjects. These volleys were initiated by stimulating peripheral mechanoreceptore by means of a light tap on the finger nail. In the patients with carpal tunnel syndrome the conduction velocity was from 17 m/sec. to 55 m/sec. (mean 33m/sec.) as compared with the control range of 40 m/sec. to 67 m/sec. (mean 51.8 m/sec). Contrasted with findings in controls was the evidence of rapid dispersion of the volley over short conduction distance along the finger in patients with carpal tunnel syndrome. In 4 of these patientt, a progressive increase in conduction velocity was apparent following surgical division of the flexor retinaculum at the wrist. In addition it was found that ischemia slowed sensory as well as motor conduction. The nerve fibers contributing to the action potential, were not uniirmly affected by ischemia where as reduction in temperature brought about a uniform slowing of the conduction velocity. At low temperatures the amplitude of the compound action potential following both electrical and mechanical stimulation was slightly greater.