Diagnosis of an anomalous superficialis muscle in the palm by magnetic resonance imaging.

Anomalous muscles of the upper extremity are encountered occasionally and in most cases, identification has been made at operation. Plain radiographs do not visualize soft tissues well. Magnetic resonance imaging provides good definition of soft tissue structures. We report a case of an anomalous flexor digitorum superficialis muscle in the palm, that was seen initially as a mass associated with a previous injury and pain. Magnetic resonance studies showed the mass to be a muscle belly in the palm. Preoperative identification of anomalous muscles is possible with magnetic resonance imaging.