Vertebrobasilar junction fenestration with dumbbell-shaped aneurysms formation: computational fluid dynamics analysis.

We report 8 rare cases of paired ANs involving fenestrated vertebrobasilar junction and demonstrate the flow patterns of the paired ANs by qualitative CFD analysis in 5 cases. Two-dimensional and 3-dimensional angiographic features of 8 cases were reviewed. Nine patient-specific geometries of CFD models in 5 cases were created for flow analysis. All 8 cases had 2 ANs, one large and the other small, projecting to the opposite sides at the proximal end of fenestrated vertebrobasilar junction. The different angiographic findings between right VA and left VA suggested the different hemodynamic characteristics of the respective VAs. Computational fluid dynamics analysis also demonstrated that the inflows of these paired ANs were different between right VA and left VA. Flow simulations by CFD were consistent with angiographic findings. Intrinsic wall defects at fenestrated vertebrobasilar junction and specific hemodynamic stresses from 2 inflows may contribute to the formation of a pair of dumbbell-shaped ANs.