Variation in the origin and branching pattern of the musculocutaneous nerve and accessory head of the biceps brachii muscle

Ricardo E. ESPARRAGOZA, Ana E.

Abstract

Anatomical variants interesting the musculocutaneous nerve (MCN) have been described and classified. It is less common find association of variations about origin and branching pattern of the MCN and the presence of accessory head of biceps brachii muscle. During routine dissection of the right upper limb on an adult male cadaver, we observed the MCN constituting a third root of median nerve, which originated after. The MCN passed anterior to the coracobrachialis muscle, without piercing it, after supplying branches for the long and short heads of biceps and continued in two branches rounding the accessory head of biceps brachii muscle; these two branches subdivided into roots that originated the nerves of brachialis muscle and lateral cutaneous nerve of forearm. Accessory head of biceps had dual origin. The presence of accessory heads of biceps is associated with variations of the MCN. Knowledge of these variations is useful to clinical practice.