Anatomical variations of the cords of brachial plexus and the median nerve.

The variations in formation, location, and courses of the cords of brachial plexus and the median nerve were studied in both axillae of 172 cadavers. The total prevalence of variation was 12.8% (CI, 7.6-17.4) and it was found in 13.2% (CI, 7.5-18) of male and in 10.7% (CI, -0.6-19.6) of female cadavers. These variations were divided into three groups. The first group was abnormal location of the cords, which was either posterolateral or anteromedial in relation to the axillary artery in 2.3% (CI, 0.1-4.5) cadavers. The lateral cord and the medial root of the median nerve had received communicating branches from the posterior cord in most of the cases of this group. The second group was absence of the posterior cord in 3.5% (CI, 0.7-6.1) of cadavers. The lateral and medial cords of this group were connected with the communicating branches, which had a course in front of the axillary artery. The third group was abnormal formation and course of the median nerve in 7% (CI, 3.1-10.6) of cadavers. In all cases of this group the medial root received communicating branch/branches either from the lateral or posterior cord. In eight (4.7%) cadavers, both roots of the median nerve were joined on medial side of the axillary artery to form a median nerve, which traveled medial to the artery. In four (2.3%) cadavers the roots of the median nerve did not join and both traveled separately anteromedial to the axillary and brachial arteries. This study indicates that all three cords and median nerve vary considerably in levels of origin, location and course in relation to the axillary artery and these variable cases were joined with the communicating branch/branches. The observed variations are of anatomical and clinical interest. These kinds of variations are more prone to injury in radical neck dissection and in other surgical operation of the axilla.