Background: To investigate the impact of fetal-type posterior cerebral artery (fPCA) variant on morphological parameters of posterior communicating artery (PComA) aneurysms for rupture risk assessment.

Materials and methods: A total of 98 PComA aneurysms (62 ruptured and 36 unruptured) in 98 consecutive patients were reviewed. Morphological parameters were calculated including aneurysm size, aspect ratio (AR), size ratio (SR), dome-to-neck ratio (DN), bottleneck factor (BNF) and inflow angle. Performance of morphological parameters to discriminate rupture status were compared between aneurysms with or without fPCA.

Results: fPCA variant was determined in 39 (39.8%, 25 ruptured and 14 unruptured) lesions. The ruptured group revealed a significantly larger size (P=0.004), AR (P=0.003), SR (P=0.001), and inflow angle (P<0.001). For the aneurysms without fPCA, all morphological parameters were significantly different between ruptured and unruptured aneurysms (P<0.05); for the aneurysms with fPCA, only inflow angle (P=0.001) was significantly related with the rupture status. Multivariate analysis showed that SR (P=0.035 and P=0.011) and inflow angle (P=0.001 and P=0.028) were independent rupture risk factors for the total cohort and the aneurysms without fPCA; while only inflow angle (P=0.004) revealed to be independently related with rupture status of aneurysms without fPCA.

Conclusions: The performance of morphological parameters to discriminate rupture status were different between PComA Aneurysms with and without fPCA variants. Inflow angle might be a reliable predictor for rupture risk of PComA aneurysms.