Abstract
Background and purposes : In clipping surgery for aneurysmal subarachnoid hemorrhage, the aneurysmal bleb is often conformed as the rupture point. Moreover, aneurysmal blebs have been identified as a factor for increased risk of rupture. We investigate possible associations between the hemodynamics and the formation of blebs in cerebral aneurysms. Methods : A patient with a growing aneurysmal bleb was selected for this study. Computational fluid dynamics simulations were performed under pulsatile flow conditions for the bleb model and the bleb cut model which was constructed by virtually removing the bleb. Results : Normalized wall shear stress (NWSS), gradient oscillatory number (GON), oscillatory shear index (OSI) and static pressure (SP) in the bleb formation area were higher than those in the aneurysmal dome. The aneurysm formation indicator (AFI) in the bleb formation area was similar to AFI in the aneurysmal dome. Wall shear stress gradient (WSSG) in the bleb formation area was smaller than WSSG in the aneurysmal dome. The specific parameter for bleb formation area was SP. Bleb growing states lead to reduction of OSI, NWSS, OSI and GON. In visualizations of flow structures, a high-flow jet impacted the bleb formation area. Conclusions : These results suggest that aneurysmal blebs are formed by damage caused by static pressure and the aneurysmal wall inflow jet based on the endothelial dysfunction.
