Multiple unilateral variations in medial and lateral cords of brachial plexus and their branches
During routine dissection for medical undergraduate teaching programme, standard skin incisions were made to expose the region of the right axilla and arm of a 58-year-old male cadaver. The pectoralis major and minor muscles were reflected laterally after detaching them from their origins, to expose the axillary neurovascular structures.\nThe lateral cord was giving off 2 LPNs-superior lateral pectoral nerve (SLPN) and inferior lateral pectoral nerve (ILPN) (). SLPN was seen to pierce the clavipectoral fascia and enter the pectoralis major muscle from its deep surface to supply it (comparable to a usual LPN). The ILPN was seen to arise from the lateral cord 1 mm distal to the origin of its superior counterpart and was observed to pierce the pectoralis minor muscle 5 mm inferior to its superior border.\nThe MPN was given off from the medial cord of brachial plexus as usual. The length of the main trunk was 3 cm and it divided into two branches-a cranial branch (branch 1) entering the lower part of pectoralis minor and a caudal branch (branch 2) which was seen to supply pectoralis major without piercing pectoralis minor ().\nThe MCN branched as usual from the lateral cord of brachial plexus but it did not pierce CB muscle (). Instead, it descended medial to the CB giving 4 branches (b1, b2, b3, and b4) and further pursued a normal course placed between biceps and brachialis. The first branch, b1, which was a short transverse branch to CB, was given off 2 cm distal to the origin of MCN and 4 cm from the coracoid process. It was seen to split into two before supplying CB. One centimeter distal to the origin of b1, a long oblique branch (b2) was given again to CB which disappeared within its substance to reappear again, posterior to the branch b3 and rejoining the main trunk of MCN caudal to b3. A third branch (b3) was given to BB, 6.2 cm caudal to origin of b2. The fourth branch (b4) was given to BB and brachialis as a common trunk at the same point where b2 rejoined the main trunk.\nThe MN was formed as usual by the union of MR and LR of MN arising from the medial and lateral cords of brachial plexus respectively. The MR of MN crossed the 3rd part of axillary artery from medial to lateral side to unite with the LR of MN which was 1 cm in length. In addition two neural communications were observed connecting the lateral and medial cords (). The cranial communication (* in ) was arising from the lateral cord 3 cm proximal to the origin of LR of MN and the caudal communication (# in ) was arising 1 mm distal to the cranial intercordal neural communication. Both the communications were seen running obliquely downwards and medially, anterior to the axillary artery and joining the medial cord. The cranial communication was bifurcating into two branches before joining the medial cord.\nFurthermore, ulnar nerve was seen to arise by two roots from the medial cord-root "a" and root "b" (). Root "b," 1 cm in length, arose at the level of intercordal neural communication and root "a," 2.5 cm in length, arose higher up in relation to the 2nd part of axillary artery. Both these roots joined to form the main trunk of the ulnar nerve.\nThe arterial pattern and the relations of axillary artery to the nerves were found to be normal. No such variation was observed in the left brachial plexus.