Abstract WP225: Fetal-Type Posterior Cerebral Artery: A Not So Benign Anatomical Variant?

Introduction: The fetal-type of the posterior cerebral artery (ftPCA) is a remnant of the embryonic cerebral vasculature and describes a predominant supply of the PCA territory by a branch of the internal carotid artery. It is usually considered a benign anatomical variant with a prevalence ranging between 3% and 40%. Given the larger supply of the brain parenchyma by the anterior circulation in this variant, ftPCA is often associated with a hypoplastic basilar artery and thus a reduced vertebrobasilar blood flow. Hypothesis: Attenuated blood flow through the vertebrobasilar system in patients with a ftPCA is associated with an increased risk of infratentorial ischemic stroke. Methods: We prospectively analyzed 625 consecutive acute stroke patients from our comprehensive stroke center. Cerebral MRI was used to identify stroke location. PCA territory blood supply was classified in 5 subcategories using CT or MRI angiography: 1) total ftPCA (i.e. complete supply via PCOM); 2) predominant ftPCA; 3) balanced PCA (supply via PCOM and P1); 4) predominant P1, and 5) complete P1 supply. Variants 1) and 2) were considered ftPCA for further analysis. We compared the frequencies of anterior, posterior, infratentorial, and multiple territories strokes between patients with and without ftPCA. Results: There were 215 patients (34%) with ftPCA. Patients with ftPCA were significantly more likely to suffer from an infratentorial stroke than those without the ftPCA variant (20% vs 12.2%, P = 0.009). In contrast, anterior, posterior, and multiple territories stroke did not differ between groups. When posterior territory strokes were attributed to the corresponding P1 or PCOM supply, there was no difference in the frequency of vertebrobasilar stroke (i.e. infratentorial plus P1-PCA) between patients with and without ftPCA (P=0.864). Mean cross sectional area of the basilar artery was significantly lower in patients with ftPCA compared to those without ftPCA (6.6mm2 vs. 9.7mm2, P<0.001). Conclusion: Fetal-type PCA is associated with a higher frequency of infratentorial stroke and a lower cross sectional area of the basilar artery. Possibly, hemodynamic factors influence infratentorial stroke risk in patients with ftPCA.