During the dissection of an 83-year-old male cadaver, two bulbous origins of the aortic arch branches were noticed. The right divided into the brachiocephalic trunk and the left common carotid artery, and the left divided into the left vertebral and left subclavian arteries. A scalenus minimus muscle and a proximally split anterior scalene muscle divided the left interscalene triangle into four compartments through which the roots of the brachial plexus and the subclavian artery exited separately through each compartment. Variations like this could make the clinical distinction of aortic arch syndrome from thoracic outlet syndrome difficult, particularly, when the subclavian artery is involved and complicates the approach to structures in the interscalene triangle. Surgeons, radiologists, anesthesiologists and others involved in these areas should be cognizant of such variations in order to make the correct diagnosis, apply the appropriate procedure and institute the proper treatment for a better clinical outcome.
