Aberrant right subclavian and left vertebral arteries
An aberrant right subclavian artery arises as the last branch off a left-sided aortic arch and courses obliquely and superiorly behind the trachea and esophagus to resume its normal course. It is typically an isolated anomaly, represents one of the most common aortic arch branching anomalies, and affects up to 0.5% of the population, with a reported prevalence of 0.4–2%.
The so-called diverticulum of Kommerell was first described on an oesophagram of an asymptomatic patient with a left aortic arch and an aberrant right subclavian artery with a diverticulum at its origin, which produced mass effect on the esophagus. Interestingly, the aortic diverticulum occurs more frequently in patients with right aortic arch and aberrant left subclavian artery and is also referred to as a diverticulum of Kommerell in these instances. It may be congenital or secondary to atherosclerotic dilatation.
Other minor anomalies of aortic arch branching occur relatively frequently. The most frequent are: common origin of the right brachiocephalic artery and the left common carotid artery (so-called bovine arch) (25% prevalence) and aberrant origin of the left vertebral artery proximal to origin of the left subclavian artery, as seen in this case, (2.4–5.8% prevalence).