A variation in the formation of the median nerve: communicating branch between the musculocutaneous and median nerves in man.

We encountered variation in the formation of the median nerve in a 66-year-old male cadaver during dissection of the upper extremity of 20 adult cadavers. The dissections were made at the Department of Cellular Biology and Anatomy, Louisiana State University Medical Center. The median nerve was formed by fusion of four branches, three of them coming from the lateral cord and one from the medial cord. The normal radix from the lateral cord followed a very close oblique course over the axillary artery. The first unusual radix to the median nerve had an anastomoses from the musculocutaneous nerve to the median nerve in the proximal part of the left arm. The second unusual radix also came from the musculocutaneous nerve after it had pierced the coracobrachialis muscle and then joined with the median nerve. These kinds of variations are vulnerable to damage in radical neck dissection and other surgical operations of the axilla and upper arm. The communicating branch can be explained on the basis of its embryologic development and also ought to be distinguished from the other nerve variations in the upper extremity. The aim of this paper is to provide additional information for the classification of previously found communications between the musculocutaneous and median nerves.