[Simulation study on parent artery occlusion therapy for basilar head giant aneurysms: hemodynamic efficacy of additional bypass on enhancing aneurysmal thrombosis].

Parent artery occlusion therapy has been used as an alternative for directly untreatable basilar head giant aneurysms. However, some aneurysms still require additional technique to further induce intraaneurysmal stagnation and thrombosis. Using a hydraulic model, half-life of the dye in the model aneurysm was measured as an index of the intraaneurysmal stagnation. The ratio of diameters (D1, D2) of the two posterior communicating arteries (PCom) is defined as diameter ratio (DR) (D1/D2, D1 < D2). Occlusion therapy was simulated in 4 different sites. The most distal site was at the distal BA (Type A) and the most proximal site at the bilateral VA (Type D). The additional technique investigated was bypass placement to the P2 segment of the posterior cerebral artery (PCA) on the smaller PCom side. The half-life was 2.5 +/- 0.2 (mean +/- 2SD) sec before occlusion. Occlusion therapy significantly increased the half-life depending on the occlusion site and DR values with the maximum values of infinite in Type A and 25 sec in Type D. Placement of the bypass decreased the tangential flow volume to the aneurysmal neck, and increased the time markedly in Types A and B, considerably in Type C and slightly in Type D. Parent artery occlusion therapy has been considered less beneficial for patients with a diameter ratio of less than 0.70 since aneurysmal stagnation depends on the diameter ratio. Bypass placement additional to the occlusion therapy is very useful in enhancing the aneurysmal stagnation, which would make those patients indicated for the therapy.