Anatomical variation: median nerve formation - a case vignette.

Variations in the arrangement and distribution of brachial plexus and its branches in the infraclavicular part are common and have been reported by several investigators since the 19th century. These variations are significant for the neurologists, surgeons, anesthetists and the anatomists. During routine anatomical dissection of the right axilla and infraclavicular region of a 45-year-old male cadaver, the medial root of the median nerve was found to receive a supplementary branch from the medial aspect of the terminal portion of the lateral cord of brachial plexus and the branch was passing infront of the axillary artery from lateral to medial side. The median nerve was formed by joining of the lateral and medial roots from the lateral and medial cords of brachial plexus, infront of brachial artery, lower down, at the junction of upper one-third and lower two-third of the arm, instead in the axilla. This variation could be one of the cause of pressure symptom which occurs on the axillary artery and also the injury which occurs on the lateral cord or upstream to the lateral cord, which may sometimes lead to an unexpected presentation of weakness of forearm flexors and thenar muscles.