Agenesis, Left Internal Carotid Artery

Findings:

AP left subclavian and lateral left common carotid arteriograms show no opcification of the left interal carotid artery, with the left MCA and branches showing hemodilution from cross filling and antegrade PCOM flow. The axial CT shows absence of the left carotid canal.

Differential diagnosis:

None except congenital absence of left ICA for the CT appearance. Lack of ICA opacification on arteriogram may be due to congenital absence of the vessel versus aquired occlusion which may be due to many causes but typically atherosclerotic disease or dissection.

Discussion:

Congenital absence of the internal carotid is a rare vascular anomaly, seen in less than 0.01% of patients. The absence of the osseous carotid canal distinguishes from an aquired occlusion.

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