Cerebral aneurysm size and hemodynamic instability: A computational approach to rupture risk prediction

Cerebral aneurysms are focal dilations of brain arteries that pose a high risk of rupture, yet the underlying hemodynamic mechanisms are poorly understood. This study employs computational fluid dynamics to simulate the hemodynamic environment of aneurysms having varying sizes under identical boundary conditions. Three idealized aneurysm models (small, medium, and large) were analyzed in terms of wall shear stress (WSS), velocity and pressure distribution, and intra-aneurysmal flow patterns. A physiological inlet velocity profile was applied to replicate realistic pulsatile blood flow over a full cardiac cycle, including systolic and diastolic phases. The results demonstrate that larger aneurysms experience more complex and disturbed flow, lower WSS, and greater regions of flow recirculation that are strongly associated with increased rupture risk. Notably, WSS around the aneurysm neck was higher during early systole than at peak systole and that is likely due to rapid flow acceleration during the onset of the cardiac cycle. This localized elevation in early systolic WSS near the neck may contribute to wall degradation and increased vulnerability to rupture. On the contrary, arterial segments without aneurysmal dilation exhibited WSS patterns that followed classical hemodynamic behavior, with maximum WSS occurring at peak systole due to the predominance of developed, high-velocity flow. These findings emphasize the importance of incorporating both temporal flow dynamics and spatial variability in WSS regarding aneurysm risk assessment, rather than relying solely on aneurysm size or static metrics.