Delayed Repair of Severed Thenar Branch with Transligamentous Variation after Open Carpal Tunnel Release.

A 49-year-old female patient with carpal tunnel syndrome at both hands was performed open carpal tunnel release. 4 months later, on the left hand, severance of the thenar branch was found by electromyography. On the 138th day, re-exploration was performed for direct nerve repair. During exploration, we identified the transligamentous variation of recurrent motor branch. Direct nerve repair was successful. At 6 months after direct repair, the nerve function began to return. At 2 years after direct repair, the nerve function has almost returned. There are some variations on the recurrent motor branch. And we overlooked transligamentous variation when we perform more decompression around the median nerve. It is important that recognize variations of thenar branch when we perform carpal tunnel release for not occurrence of severance of thenar branch.