Right aortic arch with aberrant left subclavian artery and anomalous Circle of Willis supply

Right aortic arch (RAA) anomalies are rare congenital vascular malformations with a prevalence of 0.01% to 0.1% in the general population. These anomalies are often associated with congenital cardiac abnormalities, though many individuals remain asymptomatic and are diagnosed incidentally. However, cerebrovascular anomalies associated with RAA have not been previously reported. We present the case of a 23-year-old male with an incidental finding of a Type II RAA variant characterized by an aberrant left subclavian artery and an unusual, complex configuration of the Circle of Willis (CoW). This CoW anomaly includes an absent right internal carotid artery, an absent left vertebral artery, and unique collateralization pathways. Despite the variant anatomy, the patient has remained neurologically asymptomatic. No underlying genetic abnormalities were detected during further investigation with a chromosomal analysis. This case highlights the novel association between RAA and anomalies of the CoW, emphasizing the importance of detailed cerebrovascular imaging in patients with RAA. Since an anomalous CoW is inherently associated with an increased risk of cerebrovascular accidents and poorer outcomes, information on cerebrovascular anatomy can facilitate proactive risk factor monitoring, and is valuable for surgical/neuro-interventional planning when indicated.