Carpal tunnel: MR imaging. Part II. Carpal tunnel syndrome.

The magnetic resonance (MR) images of 14 wrists of patients with carpal tunnel syndrome (CTS) were studied. Four general findings visible regardless of the cause of CTS included swelling of the median nerve, best evaluated at the level of the pisiform bone; flattening of the median nerve, most reliably judged at the hamate level; palmar bowing of the flexor retinaculum, best visualized at the level of the hamate bone; and increased signal intensity of the median nerve on T2-weighted images. Findings related to cause were tendon sheath edema in traumatic tenosynovitis, synovial hypertrophy in rheumatoid tenosynovitis, a ganglion cyst, and excessive amount of fat within the carpal tunnel, a persistent median artery, and a large adductor pollicis muscle. Knowledge of these findings may permit more rational choice of treatment. In four cases in which symptoms persisted after surgery, findings valuable in explaining or predicting the failure included incomplete incision of the flexor retinaculum, excessive fat within the carpal tunnel, persistent neuritis of the median nerve, and development of neuromas.