Inflow Angle Impacts Morphology, Hemodynamics, and Inflammation of Side-wall Intracranial Aneurysms

Background Aneurysm inflow angle has been shown to be associated with hemodynamic changes by computational fluid dynamics. However, these studies were based on single aneurysm model and were limited to side-wall aneurysms. Purpose To investigate the association between inflow angle and morphology, hemodynamic, and inflammation of intracranial side-wall and bifurcation aneurysms. Study type Prospective. Population A total of 62 patients (aged 58.34 +/- 12.39, 44 female) with 59 unruptured side-wall aneurysms and 17 unruptured bifurcation aneurysms were included. Field strength/sequence A 3.0 T; 3D fast field echo sequence (TOF-MRA); free-breathing, 3D radio-frequency-spoiled, multi-shot turbo field echo sequence (4D-flow MRI); 3D black-blood T1-weighted volumetric turbo spin echo acquisition sequence (T-1-VISTA) Assessment Two neuroradiologists assessed the inflow angle and size for intracranial aneurysms in 3D space with TOF-MRA images. The average and maximum inflow velocity (Vavg-IA, Vmax-IA), blood flow (Flow(avg-IA), Flow(max-IA)), and average wall shear stress (WSSavg-IA) for aneurysms were assessed from 4D-flow MRI in regions of interest drawn by two neuroradiologists. The aneurysmal wall enhancement (AWE) grades between precontrast and postcontrast T-1-VISTA images were evaluated by three neuroradiologists. Statistical tests Kruskal-Wallis H test, chi(2) test, Pearson's correlation coefficient, scatter plots and regression lines, multivariate logistic regression analysis (partial correlation r) were performed. A P < 0.05 was considered statistically significant. Results The WSSavg-IA (0.52 +/- 0.34 vs. 0.27 +/- 0.22) and AWE grades (1.38 +/- 1.04 vs. 2.02 +/- 0.68) between the two inflow angle subgroups of side-wall aneurysms were significantly different. The aneurysm size (r(s) = 0.31), WSSavg-IA (r(s) = -0.45), and AWE grades (r(s) = 0.45) were significantly correlated with inflow angle in side-wall aneurysms. While in bifurcation aneurysms, there were no significant associations between inflow angle and size (P = 0.901), Vavg-IA (P = 0.699), Vmax-IA (P = 0.482), Flow(avg-IA) (P = 0.550), Flow(max-IA) (P = 0.689), WSSavg-IA (P = 0.573), and AWE grades (P = 0.872). Data conclusion A larger aneurysm size, a lower WSS and a higher AWE grade were correlated with a larger inflow angle in side-wall aneurysms. Evidence Level 3 Technical Efficacy Stage 2

Automated summary

This study investigated the association between inflow angle and morphology, hemodynamic, and inflammation of intracranial side-wall and bifurcation aneurysms. The results showed a significant correlation between inflow angle and aneurysm size, wall shear stress, and aneurysmal wall enhancement in side-wall aneurysms, while no significant associations were found in bifurcation aneurysms.