Severance of the thenar branch of the median nerve as a complication of carpal tunnel release.

Loss of thenar motor function was noted in two patients who were seen after surgical release for carpal tunnel syndrome. Both patients were clinically and electromyographically found to have denervation of the thenar muscles. The severed motor branch was identified, isolated, and repaired at reexploration (5 months and 14 months after surgery). Thenar function eventually returned in both patients.