According to the usual description in most anatomy texts,
the median nerve in the forearm passes between the 2 heads
of pronator teres. It continues distally between flexor
digitorum superficialis and profundus almost to the
retinaculum. Muscular branches leave the nerve near the
elbow and supply all superficial muscles of the anterior part
of the forearm except flexor carpi ulnaris. Many variations
of the median nerve in the forearm have been reported
(Urban & Krosman, 1992). The palmaris profundus is also
a rare anomaly of the forearm (Dyreby & Engber, 1982). It
originates from the radial side of the common flexor tendon
in the proximal forearm and inserts into the undersurface of
the palmar aponeurosis. The origin of palmaris profundus
may be close to the median nerve and its branches, and may
be involved in compressive neuropathy of the anterior
interosseous nerve. Its tendon crossing through the carpal
canal has been implicated in the carpal tunnel syndrome
(reviewed by Lahey & Aulicino, 1986). In some cases,
palmaris profundus was found enclosed in a common fascial
sheath with the median nerve (Stark, 1992; Sahinoglu et al.
1994). To indicate its close association with the median
nerve, the palmaris profundus was also named ‘musculus
comitans nervi mediani’ (Sahinoglu et al. 1994). This article
reports an unusual loop of the median nerve encircling an
anomalous palmaris profundus in the forearm, which, to the
best of our knowledge, has not been previously described.