Impact of aging-induced hemodynamic variations on rupture risk in terminal MCA aneurysms: A computational study

This study aims to investigate the influence of aging-induced flow waveform variations on hemodynamic parameters associated with rupture risk in terminal saccular aneurysms of the Middle Cerebral Artery (MCA), using patient-specific Computational Fluid Dynamics (CFDs) analysis. Two male patients — one with a ruptured MCA aneurysm and one with an unruptured aneurysm — were selected for comparison. Age-specific inlet velocity waveforms corresponding to four age groups (20–39, 50–59, 60–69 and 70–79 years) were applied to simulate physiological blood flow. Hemodynamic parameters, including Wall Shear Stress (WSS), Oscillatory Shear Index (OSI), Time-Averaged Wall Shear Stress (T-AWSS) and intra-aneurysmal velocity were evaluated and compared across age conditions and aneurysm types. The ruptured aneurysm exhibited consistently higher mean and maximum values of WSS, OSI and T-AWSS across all age groups, with strong flow impingement and focused high-shear regions. Aging resulted in increased flow oscillation and peak shear stress, particularly in the ruptured case. In contrast, the unruptured aneurysm demonstrated lower and more spatially diffuse hemodynamic stresses, with minimal variation across aging profiles. Despite its larger volume, it maintained a stable intra-aneurysmal flow environment with reduced rupture-associated stress markers. Hemodynamic parameters associated with aneurysm rupture risk are strongly influenced by both aneurysm geometry and age-specific flow conditions. Elevated and persistent high shear and oscillatory stresses in the ruptured aneurysm suggest a dominant role of local flow dynamics over aneurysm size alone. These findings support the integration of age-adjusted waveform data in CFD-based patient-specific aneurysm risk assessments for improved clinical decision-making.