Preliminary observation of the relationship between intraoperative electrophysiologic testing and surgical outcome of carpal tunnel release

Objective To explore a reliable predicator of surgical outcomes of carpal tunnel release(CTR)by exploring the changes of pre-and intraoperative median nerve-abductor pollicis brevis compound muscle action potential(CMAP).Methods Fifteen patients with carpal tunnel syndrome were involved in the study.Electrophysiologic examination was carried out to record CMAP of abductor pollicis brevis muscle at following moments:before CTR right after brachial plexus block,immediate after CTR and tourniquet release,1minute,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 toumiquet release(P<0.05),while not much difference was seen after 5 minutes.While:both the latency and amplitude of CMAP were greatly improved(P<0.05),the improvement of amplitude had more statistical significance(P<0.01).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 electrophysiologic examination at least 5 minutes after tourniquet release. Key words: Carpal tunnel syndrome; Electromyography; Action potentials