Carpal Tunnel Syndrome Caused by Anomalous Lumbrical Muscle

• Published in: Orthopedics & Traumatology Vol. 49; no. 3; pp. 880 - 882
• Main Authors: Hara, Kouji, Matsuzaki, Akio
• Format: Journal Article
• Language: English
• Published: West-Japanese Society of Orthopedics & Traumatology 2000
• Subjects: abnormal lumbrical muscle; carpal tunnel syndrome; median nerve; multiple crush; pronator syndrome
• ISSN: 0037-1033; 1349-4333
• DOI: 10.5035/nishiseisai.49.880

A rare case of carpal tunnel syndrome caused by an anomalous lumbrical muscle, associated with ipsilateral pronator syndrome, is reported. An 18-year-old male was operated on for left carpal tunnel syndrome and pronator syndrome. Upon division of the transverse carpal ligament, very slight changes due to compression could be seen on the surface of the median nerve and an abnormal muscle was seen on the medial side of the median nerve. The muscle arose from the radial aspect of the flexor profundus tendon to the index finger and the distal margin of the origin was 2cm proximal to the transverse crase of the wrist but portions more proximal of the origin and insertion of the muscle could not be identified. On traction of this muscle, the metacarpo-phalangeal joint of index finger was flexed. In the proximal forearm, the median nerve was compressed by abnormal accessory insertion of the brachialis muscle, bicipital aponeurosis and hypertrophied humeral head of the pronator teres muscle. We assume that the carpal tunnel syndrome was caused not only by the abnormal lumbrical muscle but also by the compression in the proximal forearm (multiple crush).