Differentiating extradural head and neck arterial fenestrations from other intraluminal abnormalities.

Background And Purpose: Arterial fenestrations are a benign entity arising from a failure of fetal fusion. However, fenestrations in the head and neck may be misinterpreted as carotid webs or dissections. Given differences in clinical management, the differentiation of these entities is imperative. We aim to document the prevalence of these entities on CTA imaging and highlight imaging features for confident differentiation.

Materials And Methods: We retrospectively reviewed head and neck CTA studies performed at our institution over an 18-month period. The extradural common carotid, internal carotid, external carotid, and vertebral arteries were inspected for intraluminal abnormalities. These abnormalities were classified as fenestration, web, or dissection. Location and associated non-atherosclerotic calcification, pseudoaneurysm, or thrombosis were also documented.

Results: A total of 1800 head and neck CTAs were examined. Normal extradural arteries were seen in 1731 patients (1731/1800; 96.2 %). An intraluminal abnormality was evident in the remaining 69 patients (69/1800; 3.8 %). There were 16 carotid webs (16/1800; 0.9 %), 46 dissections (46/1800; 2.6 %), and 7 fenestrations (7/1800; 0.4 %). An associated non-atherosclerotic pattern of calcification was only identified in a single fenestration case (1/7; 14.3 %). Thrombosis was not identified in any fenestration case.

Conclusion: Arterial fenestrations of the extradural head and neck arterial vasculature are evident on 0.4 % of CTAs. It is important to differentiate these benign entities from carotid webs and arterial dissections. With the appropriate knowledge and interpretive tools, characteristic imaging findings on CTA can be used for reliable differentiation.