A novel classification for posterior communicating artery aneurysms in the presence of fetal posterior cerebral artery: A registry-based study.

Background and objectivesFetal posterior cerebral artery (fPCA) is a common anatomical variant where the P1 segment is hypoplastic or absent, and the posterior communicating artery supplies the posterior cerebral artery (PCA) territory. Aneurysms in this setting often form at the internal carotid artery (ICA)-posterior communicating artery junction and are poorly defined. This study introduces a novel classification to address the fPCA variant, treatment challenges, and outcomes.MethodsThis registry-based study included fPCA aneurysms treated endovascularly at the Medical University of South Carolina (2013-2024). Aneurysms are classified into type-1 (shared neck with ICA and fPCA), type-2 (neck arises from ICA, and fPCA originates from the aneurysm), and type-3 (neck originates entirely from fPCA). Aneurysm type, treatment strategy, and outcomes were compared.ResultsForty fPCAs, consisting of 20 type-1, 15 type-2, and five type-3 aneurysms, were analyzed. For type-1 aneurysms, recurrence on admission was higher (40%,  = 0.03, V = 0.34 [95% CI: 0.22-0.56]). In addition, maximum diameter ( = 0.02, η = 0.17) and neck size (= 0.001, η = 0.32) were larger in type-2 aneurysms. Treatment modalities included coiling alone (55%), stent-assisted coiling (17.5%), and flow diversion (FD) (27.5%). All coil-alone treatments were performed in newly presented ruptured aneurysm cases ( < 0.01,  = 0.57). FD was mainly used in aneurysm recurrence (54.5%), with adequate occlusion in all patients at one-year follow-up. The lowest occlusion rate was seen in type-2 (86.7% vs. 96%,  = 0.54, RR = 0.3 [95% CI: 0.03-3.03]) in one-year follow-up.ConclusionA personalized approach is needed to improve outcomes, particularly in wide-neck bifurcation fPCA aneurysms. Endovascular treatment should be individually adapted to each type to achieve optimal outcomes.