Variations in brachial plexus with respect to concomitant accompanying aberrant arm arteries

Variations in the brachial plexus are the rule rather than the exception. This fact is of special interest for the anesthetist when planning axillary block of brachial plexus.

167 cadaver arms were evaluated for variations in brachial plexus, with focus on the cords of the plexus, the loop of the median nerve, and the course of the median, musculocutaneous, ulnar, axillary and radial nerves. In addition, concomitant arterial variations were recorded.

In 167 arms, variations were detected in 60 cases (36%). With 46 arms (28%) most variations concern the median nerve, followed by 13 cases (8%) which involved the musculocutaneous nerve. Ulnar, axillary and radial nerve variations were rare, amounting to 1.2% for each nerve. In median nerve conditions with a shifted loop of median nerve (12%), a hidden position of the loop or a hidden course of the beginning median nerve (8%) and a doubled loop of median nerve (17%) were observed. In musculocutaneous nerve conditions with a non-perforated coracobrachialis (1.8%), a doubled origin of the nerve (1.2%) and a giving back of branches to the median nerve (1.8%) were noted. Variations in ulnar, axillary and radial nerves concerned lower than normal diameters.

It must be stressed that cases which showed a hidden position or a doubled expression of the loop of the median nerve, a hidden course of its beginning and variable interconnections between musculocutaneous and median nerves are of special interest for anesthetists and surgeons. Hence, it is important to note that variations of arm arteries can be associated with brachial plexus variations. For example, a common trunk of axillary artery followed by a hidden loop and course of the median nerve may result in incomplete axillary block of brachial plexus.