Low Prevalence of Fetal-Type Posterior Cerebral Artery in Patients with Basilar Tip Aneurysms

Abstract

BACKGROUND: Basilar tip aneurysms (BTA) are multifactorial in origin, with luminal forces playing a major role in their formation. Considering the reduced hemodynamic stress on the basilar apex in the fetal-type posterior cerebral artery (fPCA), we hypothesize that BTA should be less common in patients with this variant. OBJECTIVE: To investigate, in a retrospective case-control study, the frequency of fPCA in patients with and without BTA. MATERIALS AND METHODS: We collected clinical and imaging data from consecutive patients with BTA undergoing catheter angiography between July 2010 and July 2015, and from a randomly selected, age- and sex-matched non-BTA control population from our prospective database. Anatomical variants of the distal basilar artery region were assessed in the two groups and compared using parametric and non-parametric tests. RESULTS: Fifty-nine BTA cases and 337 controls were included. fPCA was present in 3% of patients with BTA and 23% in the control group (p<0.001; OR=0.11, 95% CI 0.03 to 0.48). Basilar tip disposition was cranial in 49% of BTA and 63% of non-BTA cases (p=0.04; OR=0.57, 95% CI 0.33 to 0.99); a caudal disposition was found in 24% and 6% of cases, respectively (p<0.001; OR=4.65, 95% CI 2.21 to 9.80). CONCLUSIONS: We found a statistically significant association between the absence of fPCA and BTA. Our findings underline the importance of hemodynamic stress in the formation of intracranial aneurysms, and suggest that fPCA is a protective variant for formation of BTA.