Sonographic evaluation of the median nerve at the wrist

Received March 23, 2001, from the Department of Radiology, University of Michigan Hospitals, Ann Arbor, Michigan. Revision requested April 30, 2001. Revised manuscript accepted for publication June 4, 2001. Address correspondence and reprint requests to David A. Jamadar, MB, BS, Radiology, TC 2910, University of Michigan Hospitals, 1500 E Medical Center Dr, Ann Arbor, MI 48109-0326. onography is now used to evaluate many disorders of the musculoskeletal system.1 One such example is evaluation of the median nerve in carpal tunnel syndrome.2 Sonographic findings such as median nerve enlargement immediately proximal to the carpal tunnel and bowing of the flexor retinaculum have been described in these patients.2 A correct diagnosis relies on accurate identification of the median nerve and an understanding of the osseous landmarks delineating the carpal tunnel. The presence of multiple closely approximated linear echogenic structures at the volar wrist makes identification of the median nerve difficult; differentiation from the palmaris longus tendon and other tendons may occasionally prove challenging. We present a technique that allows reliable identification of the median nerve at several locations in the distal forearm and wrist by using the real-time capability of sonography. Median nerve pathologic characteristics are also described.