Hemodynamic findings associated with intraoperative appearances of intracranial aneurysms

Intracranial aneurysms can be classified into thick-walled aneurysms and thin-walled aneurysms according to their intraoperative appearances; previous publications have revealed that different kinds of intraoperative appearances were associated with intraoperative rupture and postoperative complications. Here, we tried to evaluate the association between hemodynamic features and aneurysm wall appearance using computational fluid dynamics (CFD) method. Forty-one consecutive patients with unruptured middle cerebral artery (MCA) bifurcation aneurysms were included in our study. Based on the appearances observed under the microscope, aneurysms were classified into two different types: thick-walled and thin-walled aneurysms. Preoperative computed tomographic angiography (CTA) was used for geometry reconstruction and CFD analysis. Morphological and hemodynamic parameters were compared between the two groups. Eighteen aneurysms were classified as thick-walled atherosclerotic ones according to their intraoperative appearances. Compared with thin-walled aneurysms, aneurysms with atherosclerotic changes had larger geometry parameters (aneurysm depth, maximum height, diameter, aspect ratio, size ratio), lower wall shear stress (WSS), and larger low WSS area ratio (LSAR). Thick-walled aneurysms characterized by atherosclerotic changes are associated with low WSS and larger LSAR. CFD may be a useful tool for discriminating the intraoperative appearance of cerebral aneurysms.