Anatomical Variation of the Brachial Plexus: An Ancillary Nerve of the Middle Trunk Communicating with the Radix of the Median Nerve

Purpose: Variations in brachial plexus anatomy are common. As such, the knowledge of variations is essential for surgeons and anesthesiologists to decrease the risk of iatrogenic injuries. Moreover, brachial plexus variations often co-exist with aberrant vasculature. The median nerve is formed from contributions by the lateral and medial cords. This case report details a unique variant in the formation of the median nerve. Methods: The anatomical variant presented was identified during an upper-limb dissection of an adult cadaver.Results: The anatomical variant presented demonstrates a bifurcation of the middle trunk of the brachial plexus that coalesces to the radix of the median nerve. Although prior studies have demonstrated median nerve brachial plexus variations, the aforementioned variant arises directly from the middle trunk and communicates directly with the median nerve, while previously mentioned variants often connect to the medial or lateral cords. Conclusion: The communicating branch between the anterior division of the middle trunk and radix of the median nerve represents a unique and uncommon anatomical variation.