Objective: To explore a reliable predicator of surgical outcomes of carpal tunnel release (CTR) by exploring the changes of preoperative and intraoperative median nerve-abductor pollicis brevis compound muscle action potential (CMAP). Methods: Fifteen patients with carpal tunnel syndrome were involved in the study. Electrophysiology examination was carried out to record CMAP of abductor pollicis brevis muscle at following moments: before CTR; right after brachial plexus block; immediately after CTR and tourniquet release; 1 minute, 3 minutes, 5 minutes, and 7 minutes after tourniquet release. Statistics analysis was done to compare these parameters with preoperative values. Results: There were statistically significant changes in both amplitude and latency of the CMAP within 5 minutes after tourniquet release (P < .05) while not much difference was seen after 5 minutes. Both the latency and amplitude of CMAP greatly improved (P < .05). Moreover, the improvement of amplitude had more statistical significance (P < .01). Conclusion: CMAP amplitude is a better predictor than CMAP latency to evaluate the effectiveness of median nerve decompression. It is more reliable to carry out electrophysiology examination at least 5 minutes after tourniquet release.
