Methodological case study on saccular aneurysm initiation mechanisms using patient-specific models

A computational investigation of the hemodynamic mechanisms underlying saccular aneurysm (SA) initiation at the circle of Willis is presented. The study incorporates 3-dimensional patient-specific and idealized geometries, laminar flow, non-Newtonian blood rheology, fully coupled fluid–structure interaction, and physiologically realistic Windkessel-based boundary conditions. The developed methodology is validated against available experimental and analytical data. By integrating findings from previous studies, the work aims to provide a generalized assessment of aneurysm initiation and the associated hemodynamics. The significance of various parameters is evaluated by analyzing distinct SA at the anterior communicating and middle cerebral arteries. Vascular geometric abnormalities, such as absent or hypoplastic arterial segments, produced anatomical asymmetry and directed high mass flow rates toward the aneurysm ostium, leading to localized flow impingement and widespread wall shear stress regions. Both cases demonstrated elevated oscillatory shear index, large circumferential wall shear stress gradients, and persistently low aneurysm formation indicator, suggesting that these parameters function as supportive hemodynamic markers of aneurysm initiation. In contrast, vorticity and relative residence time exhibited case-dependent behavior. Overall, the findings suggest that a combination of vascular abnormalities and characteristic hemodynamic disturbances can be used to identify regions susceptible to aneurysm initiation.