Using Computational Fluid Dynamics Analysis to Characterize Local Hemodynamic Features of Middle Cerebral Artery Aneurysm Rupture Points

OBJECTIVE: Although rupture of cerebral aneurysms typically occurs at the fragile wall at the apex or pole, some aneurysms rupture through the body or the neck. The purpose of this study was to clarify the association between aneurysm rupture points and hemodynamic features through the use of computational fluid dynamics (CFD) analysis. METHODS: Twelve ruptured middle cerebral artery bifurcation aneurysms were analyzed by 3-dimensional computed tomographic angiography and CFD. Rupture points were evaluated on intraoperative videos by 3 independent neurosurgeons. Wall shear stress (WSS) was calculated at the rupture point, aneurysm dome, and parent artery. Intra-aneurysmal flow patterns were evaluated with cross-sectional velocity vector planes that included the rupture points. RESULTS: The mean WSS at the rupture point (0.29 Pa) was significantly lower than that at the dome (2.27 Pa) and the parent artery (8.19 Pa) (P < .01). All rupture points were located within the area of WSS <= 11.2% of the WSS at the parent artery. WSS at the rupture point was correlated with the minimum WSS at the dome (r = 0.64, P < .05), but not with aneurysm size (r = 0.26) or the aspect ratio (r = 0.16). Flow patterns revealed that all rupture points were located in lower-velocity area, which was associated with complex flow patterns and/or deviating necks. CONCLUSIONS: This study highlights the relationship between the local hemodynamic features and the rupture points observed during the microsurgical clipping. CFD may determine a rupture point of aneurysms using the feature of markedly low WSS.