Reversed palmaris longus muscle on MRI: report of four cases

Muscle anomalies around the wrist, in particular the palmaris longus muscle , may cause effort-related median nerve compression. A search of the medica l records at our university hospital between 1994 and 1999 revealed four pa tients with an effort-related median nerve compression due to a reversed pa lmaris longus muscle. Magnetic resonance imaging was used in the patient wo rk-up and showed an anomalous muscle in each case that had been missed init ially. All four patients were free of pain after simple excision of the ano malous muscle. Awareness of muscle anomalies at the wrist on MR imaging is essential in evaluating patients with nerve compressions at the wrist. The purpose of this article is to heighten this awareness in radiologists.