Absence of musculocutaneous nerve associated with a third head of biceps brachii muscle and entrapment of ulnar nerve.

Variations in the formation of the brachial plexus and in the course of its branches are not as uncommon as was once thought. A description of the abnormalities and complexities of the anatomy of the upper arm is very important with regard to surgical approaches. This case study reports a combined absence of musculocutaneous nerve associated with a third head of biceps brachii muscle in the left upper arm of an adult male cadaver. Moreover, the left ulnar nerve is entrapped within the substance of the medial head of the triceps muscle. The clinical implications, as well as the possible clinical symptoms resulting from these anomalies are discussed.