Computational fluid dynamics analysis of bypass surgery for a giant internal carotid artery aneurysm

Giant intracranial aneurysms are complex and associated with a greater risk of rupture than smaller aneurysms, requiring unique and patient-specific surgical solutions. A giant terminal internal carotid artery aneurysm was surgically managed by a vascular bypass between the internal maxillary artery and the middle cerebral artery using a radial artery graft. This bypass enabled blood flow through the external carotid artery (ECA), as the internal carotid artery was ligated. The present study performs a computational fluid dynamics based assessment of the hemodynamic factors resulting in a successful outcome. The flow domain of interest is extracted from the computed tomography-angio images at two different intervals-before the surgery and after the surgery at t=3 months. An intermediate stage is constructed to reflect the immediate post-surgery ( t=0) situation. Numerical simulations are performed using OpenFOAM solver for the non-Newtonian and patient-specific in-flow conditions. Different hemodynamic indicators such as time-averaged magnitude of wall shear stress ( |WSS|<overline>), oscillatory shear index (OSI), and relative residence time (RRT) are derived from the spatiotemporal velocity and pressure data. After the bypass surgery at t=0, the flow facilitated through ECA resulted in a reduction of |WSS|<overline> compared to the pre-surgery. Post-surgery ( t=0), the region of low |WSS|<overline> and high RRT is observed to be responsible for the thrombosis of the aneurysm. Moreover, the present simulation suggests that after three months of surgery, an improvement in values of |WSS|<overline> and the reduction in variation of OSI exemplify hemodynamic stability.