Bilateral absence of the musculocutaneous nerve: implications for humerus fracture and atypical median nerve palsy.

The absence of the musculocutaneous nerve represents a failure of the nerve to depart from the median nerve during early development. During a routine dissection of a 66-year-old white female cadaver, a bilateral absence of the musculocutaneous nerve was observed in the upper limbs. Muscles of the anterior flexor compartments of the arms including biceps brachii and brachialis were supplied by branches of the median nerve. The lateral cutaneous nerve of the forearm also branched from the median nerve. In a clinical case of a particularly high median nerve injury, a variation of an absent musculocutaneous nerve may not only result in typical median nerve palsy of the forearm and hand, but palsy in the arm that would manifest as deficiencies in both shoulder and elbow flexion as well as cutaneous sensory loss from the lateral forearm.