Variant palmaris profundus enclosed by an unusual loop of the median nerve

Abstract

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.

Palmaris profundus: One name, several subtypes, and a shared potential for nerve compression

“…5): (1) (Yoshida et al, 1983). In addition to these three origins, others have been described: common flexor origin (Sahinoglu et al, 1994), epimysium of the flexor pollicis longus (Yoshida et al, 1983;Chou et al, 2001), or of the palmaris longus (Sánchez Lorenzo et al, 1996). In both cases described herein, the palmaris profundus was arising from the flexor digitorum superficialis fascia (Fig.…”

“…We are unaware of previous MRI characterization of the relationship of the palmaris profundus tendon and the median nerve or the identification of a common sheath with imaging. One of our cases, although it demonstrated a bifid median nerve, did not have a split median nerve caused by the palmaris profundus; however, examples exist where the palmaris profundus tendon splits the median nerve in the forearm and wrist (Schuhl, 1991;Chou et al, 2001;Jones, 2006). Much to the senior author's surprise, a previously published (Spinner et al, 2000) clinical example of an anomalous palmaris longus tendon penetrating the median nerve in the distal forearm (Fig.…”

“…3 and 4). Review of the literature revealed that adherence of the median nerve to the palmaris profundus (Carstam, 1984;Floyd et al, 1990;Bauer and Trusell, 1992;Server et al, 1995) or a common sheath (Schuhl, 1991;Stark, 1992;Sahinoglu et al, 1994;Sánchez Lorenzo et al, 1996;Chou et al, 2001;Jones, 2006) is frequently described. This supports the nomenclature of the palmaris profundus proposed by Sahinoglu et al (1994), ''musculus comitans nervi mediani.''…”

Median nerve's loop in the arm penetrated by a superficial brachial artery: case report and neurosurgical considerations

“…Presence of MN's loop in the forearm enclosing the abnormal persistent median artery has been detected very occasionally in the literature, 6,7 whereas an unusual MN's ring at the upper forearm enclosing the aberrant palmaris profundus muscle has also been reported. 8 In few studies the existence of MN's palmar digital nerve loops penetrated by digital arteries has also been prescribed. Although, no so widely-known in the community of neurosurgeons, the aforementioned relationship between palmar digital nerve loops and digital arteries has been mentioned in a high prevalence as 67% 9 or 81%.…”

Palmaris Profundus Tendon Prohibiting Endoscopic Carpal Tunnel Release: Case Report

“…The origin of the palmaris profundus has been reported as "the deep fibro-osseous structures near the junction of the middle and proximal third of the palmar surface of the radius," 1 although variations of this relationship have been noted, including origination from the common flexor mass, the flexor pollicis longus muscle, and the palmar fascia (reversed muscle belly). 2,3 The tendinous portion passes distally through the carpal canal, typically volar to the median nerve, and inserts on the undersurface of the palmar aponeurosis. Although the true incidence of palmaris profundus is unknown, cadaveric dissection of 530 limbs noted this abnormality in only 1 extremity.…”