Duplication of the internal carotid artery and segmental aplasia of the vertebral arteries.

The internal carotid artery mainly supplies the brain. As the internal carotid artery contributes to the formation of the cerebral arterial circle, its variations are relevant in imaging, interventional radiology, and surgery. Knowledge of these variations is important for vascular anastomosis in free flap reconstruction and in arterial ligatures for haemostasis. During a cadaveric cervical dissection, a duplicated left internal carotid artery was incidentally observed in the carotid triangle of the neck. The internal carotid branches were dissected up to their distribution to the brain. The two branches of the left internal carotid artery penetrated into the base of the skull by the carotid canal and the foramen magnum, respectively. With the right internal carotid artery, they formed the cerebral arterial circle. The basilar artery was formed by the branch of the left internal carotid artery entering the skull by the foramen magnum. The right internal carotid artery and the two branches of the left internal carotid gave rise to all of the arteries of the cerebral arterial circle. The vertebral arteries did not contribute to its formation. This duplication of the internal carotid arteries is rare, as the literature does not describe any case of vertebral artery aplasia replaced by an internal carotid artery.