Replacement of the medial and lateral cords of the brachial plexus by a common cord and its trifurcation into major branches

During routine dissection of the brachial plexus of an elderly female cadaver of Indian origin, an unusual variation was noted on the left side. The roots and trunks were formed as routinely described in textbooks. The upper and lower trunks, each divided into anterior and posterior divisions. However, the middle trunk divided into two branches, an upper and lower, each of which gave an anterior and posterior division. The four anterior divisions so formed fused to form a common cord, which replaced the medial and lateral cords. This common cord was observed lateral to the 2nd part of the axillary artery and trifurcated to form the musculocutaneous, median and ulnar nerves. Associated with this variation were other less striking variations of the brachial plexus and the axillary artery. Such a variant cord and its relationship to the axillary artery needs to be kept in mind while performing surgeries in this region.