English

Abstract

The present case report describes one of the rare unilateral variations in the formation of median nerve by the union of three roots, twin (two) roots given off by the lateral cord and one root given off by the medial cord encountered in the right upper arm of an adult male cadaver during the pro-section hours. From the lateral cord which was seen lateral to the third part of axillary artery the musculocutaneous nerve and the twin lateral roots were seen arising very close to each other. The musculocutaneous nerve coursed laterally to innervate the coracobrachialis muscle. The origin of twin lateral roots was just medial to the origin of musculocutaneous nerve. The first lateral root which emerged proximal to the shoulder and united with the medial root and formed the median nerve was labeled as LR - 1, the second lateral root which fused with the already formed median nerve was labeled as LR - 2, In fact the second lateral root LR - 2, and the musculocutaneous nerve had a common point of origin seen as small bulge. The second lateral root LR - 2, was slightly thicker in its diameter and longer in course than the first root LR - 1 and it maintained its individual identity for about 3.5 cm before merging with the median nerve lying antero-lateral to it. The median nerve was seen forming anterior to the third part of axillary artery which continued as brachial artery. The knowledge of the formation, course and distribution with all the possible variations is an essential pre- requisite for traumatologists, neurologists, surgeons performing shoulder arthroscopy by anterior gleno-humeral portal and shoulder reconstructive surgeries, neuro-surgeons