Anatomical variations of the median nerve distribution and communication in the arm.

Anatomical variations of peripheral nerves constitute a potentially important clinical and surgical issue. The aim of this work is to study the variations of the median nerve in the arm with respect to its branching pattern and distribution as well as its possible communication with the musculocutaneous and/or ulnar nerves. Sixty arms pertaining to 30 preserved human cadavers, ranging in age from 30 to 67 years, were dissected in pursuit of this aim. In one limb out of 60 (1.7%) the median nerve gave off muscular branches to the brachialis muscle as well as a branch from its lateral root to supply both heads of the biceps brachii muscle. Concomitantly the musculocutaneous nerve was absent. The same limb demonstrated a branch from the lateral cord of the brachial plexus supplying the coracobrachialis muscle. Three limbs (5%) showed a communicating branch between the median and the musculocutaneous nerves. These observations should be considered when a high median nerve paralysis is shown to originate in the axilla or proximal arm in a patient presenting with weakness of forearm flexion and supination. Similarly, it can explain weakness of the arm flexor muscles in thoracic outlet syndrome with median nerve affection.