Morphological Analysis of Cerebral Artery Fenestrations and Their Correlation with Intracranial Aneurysms

Fenestrations of cerebral arteries are congenital variants that develop when primitive vessels fuse incompletely. An association between the incidence of aneurysm and a fenestrated artery has been noted in the radiological literature. However, technical limitations of radiological studies may hamper visualization of small fenestrations and aneurysms. We sought to analyze a large, postmortem collection of human brains to assess the association between aneurysm formation and the presence of fenestrations.This study included 333 formalin-fixed brains. The arachnoid was dissected under a microscope, the cerebral arteries were completely exposed, and fenestrations and aneurysms were identified and measured. For each specimen, age, sex, and all vascular abnormalities and variations were recorded for analysis.Fenestrations were present in 41% of the specimens, and 37% of these were multiple. Fenestrations were 3.1 ± 2.5 mm long and most commonly occurred in the anterior communicating artery (63%). Aneurysms were present in 8% of the specimens, usually in the anterior communicating artery or the middle cerebral artery. An aneurysm correlated with a fenestration was detected in 2% of all specimens (n = 4) and was not statistically significant (P = 0.18).Fenestrations of the intracranial arteries are a common anatomical finding. They are present most often in the anterior communicating artery. Most aneurysms were detected in the anterior communicating artery and middle cerebral artery. We conclude that the existence of an aneurysm in a fenestrated artery is an incidental, rather than causal, relationship.