Unusual Variation of the Biceps Brachii with Possible Median Nerve Entrapment.

The biceps brachii is one of three muscles of the anterior compartment of arm. Variations of the biceps brachii are not rare. The most frequent is the existence of a third head called the humeral head by Le Double (1897) (Rodríguez-Vázquez et al., 1999). Our article is based on the unexpected result of a routine dissection class held for medical students. Dissection was performed according to the guidelines accepted by the anatomy department (Seichert, 1999). We describe a third (accessory) head of the biceps brachii. In addition of two regular heads, the third head originated together with the short head from the coracoid process and had three insertions on the humerus after enfolding the median nerve and the brachial artery. This particular variation is important from a clinical perspective as the third head may cause entrapment syndrome of the median nerve and hypoperfusion of the upper limb due to compression of the brachial artery.