Abstract TMP13: Thin Wall Regions Of Intracranial Aneurysms Are Associated With High Wall Shear Stress

Abstract

Background: Intra-saccular hemodynamics play a key role in the pathobiological remodeling of the intracranial aneurysm (IA) wall. Evaluating the relationship between hemodynamic forces at the aneurysm wall and wall presentation can help us understand the complex processes of dysregulated vascular remodeling that occurs during IA natural history. Hypothesis: We hypothesized that greater hemodynamic insult, i.e., high wall shear stress (WSS) and high wall shear stress divergence (WSSD), results in endothelial damage and loss of internal elastic lamina, which presents as thin, translucent regions on interoperative imaging. Methods: From digital subtraction angiography images of 15 patients with IAs, aneurysm and surrounding vessels were segmented. Computational fluid dynamics (CFD) simulations were performed using generic boundary conditions for all the patients. Aneurysm walls were identified from 2D intraoperative images of IAs taken during clipping, and wall regions were classified as thick regions (white), normal (purple-crimson), and thin/translucent (red), using a semi-supervised machine learning algorithm. 2D wall classifications were mapped onto the 3D geometries for statistical analysis of differences between average hemodynamic properties across wall regions. Results: On an average, more than 30% of IA sac was visible on the 2D intra-operative image. Of the n =15 IAs, n =8, n =5 and n =2 showed pre-dominantly thick, thin, and normal wall types respectively. Average WSS and WSSD were significantly higher at thin regions of IAs as compared to both normal and thick regions. Thin wall regions also tended to co-locate with significantly lower RRT as compared to the thick and normal regions. Conclusion: Thin wall regions observed on intra-operative images of IAs are associated with greater hemodynamic insult (higher WSS and WSSD) and higher flow velocity (lower RRT).