Bilateral multiple complex variations in the formation and branching pattern of brachial plexus

Abstract

Bilateral variations in the formation and branching of brachial plexus are extremely rare. Multiple bilateral variations in brachial plexus right from divisions to branching pattern were observed during the dissection in an adult male cadaver. Lateral and medial cord formation showed deviation from the usual pattern. Anterior division of upper trunk continued as lateral cord. Medial cord was formed by the union of anterior division of lower trunk and anterior division of middle trunk, thus receiving fibers from both the trunks. Anterior division of middle trunk bifurcated into upper and lower branches. We encountered two lateral roots bilaterally and two medial roots of median nerve on the left side with anomalous origin. There were three upper subscapular nerves on the left and two on the right side with variations in their origin. Anomalous origin of many other branches on both sides was encountered. It is extremely uncommon to find so many variations in one body and bilateral variations are still too rare. Understanding of such variations is clinically important for diagnosing unexplained clinical signs and symptoms as well as during nerve blocks and certain surgical procedures around the neck and proximal arm.