A Case of the Bilateral Duplicate Palmaris Longus Muscles Coupled with the Palmaris Profundus Muscle

The palmaris longus muscle is one of the most variable muscles in human anatomy. During a routine anatomical dissection for medical students at Tottori University, we found duplicate palmaris longus muscles in the bilateral forearms together with the palmaris profundus muscle in the right forearm. The bilateral aberrant palmaris longus muscles were observed at the ulnar side of the palmaris longus muscle and their distal tendons were attached to the flexor retinaculum. The palmaris profundus muscle found in the right forearm was located at the radial side of the flexor digitorum superficialis muscle. The proximal tendon was originated from the anterior surface in the middle of the radius, while the distal tendon coursed radial to the median nerve through the carpal tunnel, finally inserting into the distal part of the flexor retinaculum. Both the palmaris longus and aberrant palmaris longus muscles were innervated by the median nerve. The palmaris profundus muscle was presumably supplied by the median nerve.