Originating in the early 19th century, "Fenestra," a Latin word for "window," is used to describe a hole in an anatomical structure.[1][2] Its derivative, "fenestration," meaning the surgical creation of such an opening, has, however, been more widely used to describe a natural luminal separation in an artery.

Intracranial arterial fenestrations are reported to be more common at the anterior communicating arterial complex and basilar artery.[3]



This patient presented with diffuse Fisher grade 4 SAH in the basal cistern. The outside hospital's CTA reported left V4 dissection vs. aneurysm (though of poor quality). However, a repeat CTA at our institute suggested a fenestration (A). Vessel wall MRI also showed no significant contrast enhancement (B, C).

Diagnostic cerebral angiography confirmed a left V4 fenestration (D, E). No cause of the hemorrhage was found, suggesting perimesencephalic non-aneurysmal subarachnoid hemorrhage. (F): right PICA and left AICA are dominant.


This patient presented with a ruptured left MCA aneurysm. There is an incidentally seen small basilar artery fenestration near the origin of the right AICA. The VAs are co-dominant, thus presenting an interesting contrast dilution pattern in the BA.


This left ICA injection shows a small left M1 fenestration.

  1. Fenestra - Oxford Reference ↩︎

  2. Fenestra - Wikipedia ↩︎

  3. Cerebral Arterial Fenestrations - Daniel L. Cooke, Charles E. Stout, Warren T. Kim, Akash P. Kansagra, John Paul Yu, Amy Gu, Nicholas P. Jewell, Steven W. Hetts, Randall T. Higashida, Christopher F. Dowd, Van V. Halbach, 2014 ↩︎