Computational Hemodynamic Investigations of Intracranial Aneurysm Pathophysiology in Identical Twins

Hemodynamic mechanisms of pathophysiology (i.e., generation and growth) of intracranial aneurysms (IA) in identical twins are still underdeveloped. To partially fill the knowledge gap and provide new insights for the aneurysm research community, we used an in-vitro validated computational fluid dynamics (CFD) method to distinguish hemodynamics (i.e., seven critical hemodynamic parameters) in three anatomical and five ablated neurovascular models from a rare pair of identical twins (i.e., Twin A and Twin B). CFD modeling results presented significant hemodynamic differences in the twins. However, they share the same genes, indicating that possible genetic mutation and environmental factors could influence neurovascular morphologies greatly, then further lead to various hemodynamic characteristics. After ablating IA sacs using a benchmarked pathway virtually, the regions of aneurysmal sac/bleb generation in the anterior cerebral artery (ACA) bifurcation register a locally high instantaneous wall shear stress of 52.9 and 70.1 Pa near the systolic peak in both Twin A and Twin B, respectively. A similar phenomenon can be discovered in performances of the other critical hemodynamic indicator, i.e., instantaneous wall shear stress gradient, with 571.1 Pa/mm for Twin A and 301.3 Pa/mm for Twin B due to aggressive blood impinging effects, leading to IA generation, respectively. Additionally, the fenestrated complex approaching the first-order ACA bifurcations in twin A could be a potential factor in assisting IA growth and rupture, via. causing abnormal instantaneous wall shear stress of 116.3 Pa, the associated gradient of 832.5 Pa/mm, and oscillatory shear index of 0.49. The bleb sac in twin B has high growth and rupture risks as the IA sac suffers relatively low instantaneous wall shear stress and high oscillatory shear index. Additionally, IA generation and growth can change blood flow rates in each connected artery in the cerebral artery system, then influence associated tissues and organs.