Unusual Relation of the Median Nerve with the Accessory Head of the Biceps Brachii Muscle: An Original Case Report

Abstract

SUMMARY:During the laboratory dissection of the brachial region and the arm, an abnormal relation of median nerve with the accessory head of biceps brachii muscle has been observed unilaterally on the right upper limb of a male cadaver. Whereas the short and long heads have their normal origin, additional-excess third head originated from the anteromedial surface of the superior part of the humerus. Some fibers of this accessory head on the medial side arise from the deep fascia surrounding the brachialis muscle. The fibers then cross the median nerve superficially before joining the third head which has inserted into a common tendon together with the long and short heads.To have information of such variations is of importance either for anatomists or clinicians especially for plastic surgeons in flap surgery. Case Report 562 tendon (Fig. 1). Some fibers of this accessory head on the medial side arose from the deep fascia surrounding the brachialis and crossed the median nerve superficially before joining the third head (Fig 2). After piercing the accessory head the median nerve descends over the brachialis muscle and enters to the forearm passing between the two heads of pronator teres in its usual course. This accessory head also inserted in to the common tendon with the long and short heads. It was observed that the accessory head was innervated by the muscular branches of musculocutaneous nerve as the main two heads. The vascular supply of this third head was also the brachial artery. Fig. 1. On the right side, biceps brachii is cut; long and short heads are reflected keeping the accessory head intact. The musculocutaneous nerve is pulled laterally. The accessory head of biceps brachii originates form the anteromedial surface of humerus, from the lateral side of the insertion of cracobrachialis muscle and inserts into the posterior aspect of the common biceps tendon. cbm: Coracobrachialis muscle, lbm: Long head of biceps brachii, sbm: Short head of biceps brachii, ah: Accessory head of biceps brachii, *: Medial fibers of the accessory head originating from the deep fascia of brachialis muscle, ≠: Common tendon of biceps brachii, bbm: Biceps brachii muscle, bm: Brachialis muscle, mn: Median nerve. 563 DISCUSSIONIt is well known that the biceps brachii muscle variations are not rare (Asvat et al.;Rodriguez-Niedenführ et al.;Bergman et al., 1984;Greig et al., 1952;Tamura, 1971). Some authors emphasize that the most frequent variations of biceps brachii was in the number of the bellies (Bergman et al., 2000). Supernumerary heads of the biceps brachii have been described as part of three-, four-, five or even seven headed biceps brachii (Swieter & Carmichael, 1980). However the three headed biceps brachii is the most commonly reported variation of the biceps brachii. It has been mentioned in the literature that the occasional presence of a third head varies according to the population from which the cadavers were sampled (Rodriguez-Niedenführ et al.). It has been stated that an accessory head had been observed i...

The term �Biceps Brachii�: A misnomer?

“…The long head arises from the supraglenoid tubercle and the short head from the tip of coracoid process along with coracobrachialis. Conjoint tendon of the long and short head gets inserted on the posterior aspect of radial tuberosity 1,2 . It is the most variant muscle of this region with 3, 4 and even 7 supernumerary heads.…”

Prevalencia de Cabeza Accesoria (Humeral) del Músculo Bíceps Braquial: Revisión de la Literatura

“…Las cabezas inferolaterales, las menos frecuentes y que se originan a nivel del tabique intermuscular lateral entre la inserción del músculo deltoides y el origen del músculo braquirradial o bien a nivel de la cresta supracondilea lateral. Por último las cabezas inferomediales, que son las más frecuentes y que se originan en la cara anteromedial del húmero, a continuación de la inserción del músculo coracobraquial, entre este músuclo y el origen del músculo braquial (Mas et al, 2006;Wahengbam et al, 2015). El caso presentado en este trabajo corresponde a este grupo.…”

Third Head of Biceps Brachii Muscle, Associated with Musculocutaneous and Median Nerve Bilateral Communication and with a Communicating Branch Between Median Nerve Roots

“…An accessory head of biceps brachii could cause an additional force or an unusual displacement of the fragments of the humerus after fracture (Mas et al, 2006). According Balasubramanian (2010), this third head of the biceps brachii would allow flexion of the elbow joint, irrespective of the position of the shoulder joint.…”