Objective: Aneurysm wall enhancement (AWE) on 3D vessel wall MRI (VWMRI) has been suggested as an imaging biomarker for intracranial aneurysms (IAs) at higher risk of rupture. While computational fluid dynamics (CFD) studies have been used to investigate the association between hemodynamic forces and rupture status of IAs, the role of hemodynamic forces in unruptured IAs with AWE is poorly understood. The authors investigated the role and implications of abnormal hemodynamics related to aneurysm pathophysiology in patients with AWE in unruptured IAs.
Methods: Twenty-five patients who had undergone digital subtraction angiography (DSA) and VWMRI studies from September 2016 to September 2017 were included, resulting in 22 patients with 25 IAs, 9 with and 16 without AWE. High-resolution CFD models of hemodynamics were created from DSA images. Univariate and multivariate analyses were performed to investigate the association between AWE and conventional morphological and hemodynamic parameters. Normalized MRI signal intensity was quantified and quantitatively associated with wall shear stresses (WSSs) for the entire aneurysm sac, and in regions of low, intermediate, and high WSS.
Results: The AWE group had lower WSS (p < 0.01) and sac-averaged velocity (p < 0.01) and larger aneurysm size (p < 0.001) and size ratio (p = 0.0251) than the non-AWE group. From multivariate analysis of both hemodynamic and morphological factors, only low WSS was found to be independently associated with AWE. Sac-averaged normalized MRI signal intensity correlated with WSS and was significantly different in regions of low WSS compared to regions of intermediate (p = 0.018) and high (p < 0.001) WSS.
Conclusions: The presence of AWE was associated with morphological and hemodynamic factors related to rupture risk. Low WSS was found to be an independent predictor of AWE. Our findings support the hypothesis that low WSS in IAs with AWE may indicate a growth and remodeling process that may predispose such aneurysms to rupture; however, a causality between the two cannot be established.
Keywords: AComA = anterior communicating artery; AIC = Akaike information criterion; AR = aspect ratio (ratio of aneurysm dome height to neck width); AUC = area under the ROC; AWE = aneurysm wall enhancement; BNF = bottleneck factor (ratio of aneurysm dome to neck width); CFD = computational fluid dynamics; HW = height to width parameter (ratio of aneurysm height to width); IA = intracranial aneurysm; ICA = internal carotid artery; ISUIA = International Study of Unruptured Intracranial Aneurysms; MCA = middle cerebral artery; MRI-SIF = MRI–SI factor; NSI = nonsphericity index; OSI = oscillatory shear index; PComA = posterior communicating artery; ROC = receiver operating characteristic; SI = signal intensity; SPI = spectral power index; SR = size ratio (ratio of aneurysm size to average diameter of the parent arteries); VWMRI = vessel wall MRI; WSS = wall shear stress; WSS* = WSS normalized to the parent artery WSS; aneurysms; computational fluid dynamics; hemodynamics; vascular disorders; vessel wall MRI.