I read with interest the article by Chan et al.1 They stated that there was a rare congenital anastomosis between the vertebral artery (VA) and internal carotid artery (ICA) with an absence of communication between the common carotid and cervical ICA. I, however, diagnose that there was an acquired occlusion of the ICA at its origin with a development of collateral circulation from the VA to the ICA via the ascending pharyngeal artery.

I am very interested in the diagnosis of the cerebral arterial variations.2 It is well known that the ascending pharyngeal artery sometimes arises from the proximal ICA.3 In the patient reported by Chan et al, the ascending pharyngeal artery was well visualized, but opacification of the ICA was faint and delayed. This suggests that there was not a direct anastomosis between the VA and ICA.

In patients with congenital absence of the ICA, the common carotid artery and the proximal external carotid artery are usually the same size. In the patient reported by Chan et al, the common carotid artery was definitely larger than the proximal external carotid artery. This fact suggests that there was an acquired occlusion of the ICA at its origin.

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