Intracranial arterial fenestration

Last revised by Dr Mohamed Saber on 25 Apr 2021

Intracranial arterial fenestration refers to segmental duplication of the intracranial arteries. They may be contrasted to arterial duplication, which consists of two distinct vessels with separate origins and no downstream convergence. They are rare anomalies, felt to result from incomplete fusion of primitive embryologic vessels. 

Fenestration is the luminal division of the vessel into two separate and parallel channels which rejoin distally 1. Each channel has distinct endothelial and muscularis layers, may be differently sized, and may share adventitial layer depending on degree of embryological fusion 3. Although a fenestration is usually of considered to be of minimal significance, there is an association with aneurysm formation near proximal part of fenestration 2. This is hypothesized to be secondary to focal defects in media layer near sites of channel divergence/convergence 4,5.

Fenestration is more common in the posterior circulation. The rate of fenestrations based on published angiographic series has been much lower than that at cadaveric series. Reported incidence of intracranial fenestration on imaging series is 3:

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Cases and figures

  • Case 1: fenestrated ACA bilateral
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  • Case 2: fenestrated left vertebral
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  • Case 3: complex Acom fenestration
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  • Case 4: fenestrated left vertebral
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  • Case 5: left A2 segment fenestration
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  • Case 6: MCA
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  • Case 7: ACOM
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