Bifid median nerve: case report

Abstract

In the article a rare case of abnormal anatomical structure of the median nerve in a patient with carpal tunnel syndrome is described: a high bifurcation of the median nerve.

A 67-year-old woman complained of periodic intense nocturnal pain and numbness of 1-3 fingers of her left hand. During clinical examination Phalen’s wrist flexion and wrist extension tests, Hoffmann-Tinel, postural provocation, median nerve compression, and the “tourniquet” tests were positive. Allen's test was negative. There was no atrophy of the thenar muscles, the strength of palmar abduction of the thumb was comparable to that of the right hand. Sensitivity of the fingers was unchanged. Based on the history and clinical examination, a diagnosis of idiopathic carpal tunnel syndrome of the left hand was made. Open carpal tunnel release, mesoepineurolysis of the median nerve, and tenosynovectomy were performed. Intraoperatively, it was found that from the proximal edge of the wound, the trunk of the median nerve was split into two parts, which were reconnected in the area of the exit from the carpal tunnel, forming a “loop” like structure. An hourglass deformity was also noted on both branches of the median nerve. The radial branch of the split nerve was visually thicker than the ulnar branch. Postoperatively, pain and numbness of 1-3 fingers resolved completely.

The median nerve bifurcation is extremely difficult to detect preoperatively. In the case of a traumatic complete anatomical injury to the median nerve, one should make sure that this structural anomaly is absent, and if there is a bifurcation of the nerve, an extended revision should be performed and a suture should be placed on both damaged branches.

During surgical treatment of carpal tunnel syndrome, it is advisable to check whether the bifurcated nerve runs through a single canal rather than two separate canals. In the latter case, it is necessary to influence both canals during operative or conservative treatment.