We have described a rare triple variation of the musculocutaneous nerve: atypical and late origin, and the unusual location of the nerve in the upper arm. Musculocutaneous nerve does not derive from the lateral cord of the brachial plexus, but from the median nerve 5-6 cm distally from the point of its formation, then it does not penetrate through coracobrachial muscle, but runs between it and biceps muscle, sending branches for its both heads. Then the nerve runs laterally and distally between biceps muscle and brachial muscle, following its typical movement to the lateral side of the arm. In its course the nerve derives motor branches to the coracobrachial, brachial and biceps muscles. Then the nerve pierces the deep fascia on the tendon of the biceps muscle and continues as the lateral cutaneous nerve of the forearm.
Variations in separation and placement of the branches of the lateral cord of the brachial plexus are frequent and important for clinical practice and must be well known and studied.
Knowledge not only for typical but also for atypical anatomy of the arm would substantially reduce errors in surgery of these areas and possible complications with bad results for patient and society.
In the available literature we did not encounter a description of low origin of musculocutaneous nerve, like our case, although some authors mention a possible variability in the origin of this nerve.
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