Recovery of conduction velocity distal to a compressive lesion.

Nerve conduction studies have been carried out pre- and postoperatively on 26 hands of patients with a carpal tunnel syndrome. When examined six to eight weeks postoperatively, there had been no significant change in conduction velocity or action potential amplitude in the fingers distal to the compression. Velocity had increased over the carpal tunnel segment. When the patients were seen between 12 and 18 weeks postoperatively, velocity and amplitude had increased in the fingers. The group with marked electrical abnormalities had improved more than the group in which digital amplitude was originally within the control range. The improvement occurred too early to be due to regeneration after relief of compression. It is suggested that either maturation of regenerating fibres was delayed by the compression or a reversible change had occurred in surviving fibres.