Association between flow patterns of the posterior cerebral arterial circle and basilar-tip aneurysms

The Cerebral arterial circle presents multiple individual anatomical configurations which are of the highest importance regarding the pathological processes for intracranial aneurysms development. Previous studies highlighted the importance of geometry and especially arterial bifurcations leading to aneurysms development. The primary objective of this study was to determine whether a flow pattern asymmetry of the P1 segments of the posterior cerebral arteries was associated with a higher risk of basilar tip aneurysm.

Two different populations were retrospectively reviewed. The first population, without aneurysm, for which TOF MRI sequences were reviewed. The second population with patients harboring basilar tip aneurysms for whom cerebral angiograms were reviewed. We retrospectively analyzed the flow contribution and symmetry of the two right and left P1 segments of the posterior cerebral arteries and the two posterior communicating arteries (Pcomm). We analyzed the association and risk factors for basilar tip aneurysm.

The anatomical and flow configurations of P1 and Pcomm have been reviewed in 467 patients without aneurysms and 35 patients with aneurysms. We identified a significant association between the flow pattern asymmetry of the P1 segments and the presence of a basilar tip aneurysm (OR = 2.12; IC95% = [1.01-4.36]; p = 0.04). We also confirmed that the male gender was protective against aneurysm (OR = 0.45; IC95% = [0.194-0.961]; p = 0.04).

Non-modal basilar tip bifurcation and flow asymmetry of P1 segments are associated with an increased risk of basilar tip aneurysm. These findings highlight the importance of analyzing MRI-TOF of the posterior configuration of the Cerebral arterial circle to potentially refine the aneurysms risk prediction.