Aberrant arrangement of the musculocutaneous and median nerves in the thoracic limbs of a mixed-breed dog cadaver.

Abstract

In the left thoracic limb of a male cadaver (adult mixed-breed dog), the median nerve (MN) after departing from the common median/ulnar nerve (UN) trunk received two branches. One from the lateral thoracic nerve (LTN) and the other from the musculocutaneous nerve (MCN). These both passed cranial to the axillary artery at the level of the lateral thoracic artery and joined the median nerve. Thus, in the proximal brachium, the axillary artery was cradled by this union, similar to the ansa axillaris of large animals and similar formations reported in human and non-human primates. In the distal brachium, the communicating branch ran unusually from the MN to the MCN on the left, and in both directions on the right. Awareness of such anatomical variations of the terminal branches of the brachial plexus (BP) in addition to the embryonic and evolutionary aspects can be useful in explaining neuroarterial signs with unknown origin, as those reported in human medicine.