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

In 1959 Sears showed that it is possible to record from human digital nerves the afferent volleys evoked by the physiological stimulus of a light tap on the fingernail. Subsequently, Bannister and Sears (1962) used the technique in studying the recovery of nerve conduction in a patient with acute idiopathic polyneuritis. This method of initiating volleys by stimulating peripheral mechanoreceptors has been employed in the present investigation to determine the conduction velocity of volleys in the digital nerves of control subjects and of patients with the carpal tunnel syndrome. It is known that in this condition there is slowing of motor conduction (Simpson, 1956; Thomas, 1960) and of sensory conduction (Gilliatt and Sears, 1958) across the compressive lesion at the wrist, but measurements of the conduction velocity in the digital nerves distal to the lesion have not previously been made. A brief account of this work has already been published (McLeod, 1965).