Congenital Variants and Anomalies of the Aortic Arch

A practical radiology review of Congenital Variants and Anomalies of the Aortic Arch, focused on imaging findings, differential diagnosis, reporting points, and high-yield teaching pearls.

Embryology

• 4th arch → definitive aortic arch
• 5th arch → normally regresses (persistence = rare anomaly)
• 6th arch → ductus arteriosus / ligamentum arteriosum
• 22q11.2 deletion → favors 4th arch regression (Type B IAA, RAA)

Key imaging clue

• Arch sidedness = bronchus crossed (not vessel origin!)
• Vascular ring may be “invisible” if atretic → look for indirect signs:
• Distorted subclavian
• Kommerell diverticulum
• Ductal dimple opposite arch