Palmaris profundus and carpal tunnel syndrome: is it really a palmaris muscle?

Abstract

The palmaris profundus (PP) is a variable muscle present in the flexor muscle region of the forearms. Its implication in the etiopathogenesis of carpal tunnel syndrome has been discussed in the literature. We present a case of a PP with a characteristic morphology, associated with a bifid median nerve (MN), found during surgery for a recurrence of carpal tunnel syndrome in a 51-year-old female patient. The PP muscle was first described with this morphology by Frohse in 1908. Initially, this muscle was considered an anatomical variation of the palmaris longus, but since 1984 the existence of both muscles has been observed in the same forearm, so the PP is considered an accessory muscle. Some authors associate the existence of a PP with compression of the median nerve in the carpal tunnel. Others, however, argue that it may be an aggravating factor but not the primary cause, or simply a casual finding during surgery. We believe that this tendon is not the primary cause of compression of the MN, but it can aggravate the situation in case of a reduced canal due to any other cause, so we recommend surgeons to resect it if it is found. Furthermore, based on the embryological origin of the forearm muscles, we believe that this PP could actually be the radio-carpal, radio-palmar or short radial forearm muscle described as early as the 19th century.