Exploring Anatomical Variations: A Case Study of an Aortic Arch and Left Superior Intercostal Artery Variants with Clinical Considerations

Background: In its usual pattern, the aortic arch has three branches, namely, from right to left, brachiocephalic trunk, left common carotid artery, and left subclavian artery. Normally, as one of the branches off the left subclavian artery, the costocervical trunk gives off the left superior intercostal artery. The aim of this case is to describe a variation in the aortic arch wherein the left common carotid artery branches from the brachiocephalic trunk, with an additional rare finding of the left superior intercostal artery branching directly from the left subclavian artery.

Case Information: As part of the cadaveric anatomy laboratory requirement of the Cardiopulmonary System Course (MEDE7615), our group performed a dissector-directed study of the thoracic cavity of a 67-year-old female donor to the UNTHSC Willed Body Program. Upon removal of the anterior part of the rib cage and subsequent exposure of the mediastinum and its contents, a variation in the branching pattern of the aortic arch in the superior mediastinum was dissected, cleaned, and identified. Following dissection of the aortic arch and its branches, we observed variations in the aortic arch and left superior intercostal artery. In this donor, the left common carotid artery branched from the brachiocephalic artery. This created only two vessels off the aortic arch rather than the three typically seen. We also observed that, on the left side, the superior intercostal artery branched directly from the subclavian artery and not from the costocervical trunk of the subclavian artery. This variant placed the left superior intercostal artery in a position more inferior and posterior in the upper part of the left pleural cavity.

Conclusion: Awareness of the aortic arch and left superior intercostal artery variations are clinically relevant to ensure prevention of potential surgical errors and ambiguity when viewing radiologic images.