Congenital Anomalies and Variations of the Carotid and Vertebral Arteries: A Case-Based Imaging Review.

The carotid and vertebral arteries are critical components of the cerebral circulation, supplying the brain and spinal cord. Their embryologic development involves complex transformations of the aortic arches, paired dorsal aortae, and cervical intersegmental arteries. Congenital anomalies and variations involving their origin, course, and branching patterns are relatively common and are increasingly recognized using modern imaging. While many of these variants are incidental, some carry important clinical implications, particularly in contexts of stroke imaging, head and neck surgery, and neurointerventional procedures. This article reviews the embryologic development of the carotid and vertebral arterial systems, highlights normal and variant anatomy, and presents a case-based, illustrated overview of these congenital anomalies. Emphasis is placed on key findings utilizing computed tomography angiography (CTA), magnetic resonance angiography (MRA), and catheter angiography. Particular attention is given to structural and pathway variations, including vessel agenesis or hypoplasia, the aberrant internal carotid artery within the temporal bone, abnormal branching patterns, fenestrations, and persistent fetal anastomoses (such as the primitive trigeminal, hypoglossal, and proatlantal intersegmental arteries). Ultimately, familiarity with these anomalies, their embryological origins, and their distinct imaging characteristics is essential for ensuring accurate interpretation and avoiding diagnostic pitfalls and procedural complications.