A Rare Variation of the Axillary Nerve Formed as Direct Branch of the Upper Trunk.

The brachial plexus has a complex anatomical structure from its origin in the neck and through its course in the axillary region. Knowledge of variations of the brachial plexus has important clinical applications especially in relation to trauma and surgical procedures of upper limb. The present study has reported a rare variation of the brachial plexus where the "axillary nerve" arising as a direct branch from the upper trunk instead from the posterior cord. Once the "axillary nerve" was given off, the remaining superior trunk had joined with the anterior division of middle trunk in the formation of the lateral cord. The posterior cord was formed by the union of posterior divisions of the middle and inferior trunks. The "axillary nerve" has given off braches to subscapularis, latissimus dorsi, deltoid and teres minor muscles while having given a "communicating branch" for the posterior cord. The current report indicates an anatomical variation not documented so far which may help in planning safe surgical procedures in this region and to explain unusual resulting complications.