Fetal-type posterior cerebral artery (fPCA): association with posterior communicating artery aneurysm rupture and treatment outcomes, with practical surgical risk-mitigation strategies.

BACKGROUND

The fetal-type posterior cerebral artery (fPCA) is a circle of Willis variant in which the posterior cerebral artery (PCA) territory is supplied mainly by the internal carotid artery (ICA) through a dominant posterior communicating artery (PComA), with a hypoplastic or absent ipsilateral P1 segment. This carotid dependence alters collateral reserve and the hemodynamics of the ICA-PComA junction, with consequences for aneurysm formation, rupture, and procedural safety.

METHODS

We performed a narrative review. We searched PubMed/MEDLINE and Scopus for English-language studies on fPCA and PComA aneurysm formation, rupture, and microsurgical, endovascular, and revascularization outcomes, prioritizing cohort series, comparative studies, and quantitative reports. This is a narrative synthesis and not a systematic review or meta-analysis.

RESULTS

fPCA is overrepresented among patients with PComA aneurysms, with a prevalence on the aneurysmal ICA of about 42% versus 19% contralaterally (odds ratio [OR] 3.04), and the association is specific to the ICA-PComA location (OR 2.76). Its effect on rupture is less consistent: fPCA is an independent predictor in some series (OR 2.10) and on radiomic analysis (OR 3.85) but not in others, with a pooled unadjusted OR of 1.57 (95% CI 1.13-2.19) in meta-analysis. Flow diversion achieves complete occlusion in only about 42-44% of fPCA-associated aneurysms versus 78-82% without fPCA.

CONCLUSIONS

fPCA is an anatomic modifier of both aneurysm risk and treatment. Preservation of the dominant PComA trunk is the unifying surgical and endovascular principle. Heterogeneous definitions limit cross-study comparison, and standardized reporting of complete versus partial fPCA is needed.