Electrophysiologic studies of the median nerve and its palmar cutaneous branches after nerve grafting.

Electromyography (EMG) and nerve conduction studies were performed on a patient with an incomplete lesion of the median nerve involving the motor fibers to the thenar muscles, the palmar cutaneous branches, and the sensory fibers to the index finger. The studies were done before, and 13 weeks, 16 weeks, and one year after grafting. The preoperative electrodiagnostic evaluation showed abnormalities involving the median motor fibers and the palmar cutaneous branch. Electromyography of the opponens pollicis and abductor pollicis brevis before surgery showed severe active denervation. Thirteen weeks after nerve grafting, the median motor distal latency was prolonged and the amplitude of the evoked potential of the median motor and index finger digital sensory nerves were decreased. At 16 weeks, both the latency and amplitude showed improvement, as did EMG of the affected muscles. One year later, the electrophysiologic findings were normal except for a slightly prolonged median motor distal latency. Clinical and functional improvement after grafting correlated well with the electrophysiologic findings. We conclude that EMG and nerve conduction studies are useful tools for following the progression of recovery after nerve grafting.