Aberrant axillary artery descending deep beneath the brachial plexus.

An aberrant axillary artery that descended deep beneath the brachial plexus during its course was observed. The artery passed between the lateral and medial cords, as would an ordinary axillary artery, but further passed between the posterior divisions forming the posterior cord. The axillary artery turned medially to emerge from the lower border of the medial cord and finally ran as an ordinary artery. The aberrant axillary artery is judged to reach deeper to the brachial plexus, because it penetrated the posterior division of the brachial plexus from superficial to deep. It is possible to account for the formation of this artery as one of the combinations of the ordinary axillary artery and its branches, with the positional relationships between the brachial plexus.