Abstract WMP34: Multimodal Evaluation of Unruptured Intracranial Aneurysm Wall

Abstract

Background and Purpose: Recent studies have suggested that MR-vessel wall imaging (VWI) or computational fluid dynamics (CFD) could evaluate aneurysm wall features in unruptured intracranial aneurysms (UIAs). The combination of these modalities might be comprehensive and help better understanding of the pathophysiology of aneurysm wall. This study was performed to disclose the relationship between VWI and hemodynamic characteristics evaluated by CFD. Methods: From April 2017 through May 2019, a total of 36 microsurgically-treated UIAs preoperatively underwent VWI and CFD were reviewed. Three-dimensional T1-weighted fast spin-echo sequences were obtained before and after injection of contrast medium, and aneurysm wall enhancement (AWE) was evaluated. CFD was carried out using patient specific geometry models from three-dimensional CT angiography. Morphological variables, intraoperative inspection and hemodynamic parameters were statistically analyzed between enhanced and nonenhanced wall of UIAs. Fourteen UIAs were available for histopathological examination. Results: In morphological variables, maximum diameter and irregularity were associated with AWE (p=0.02, respectively). AWE lesions corresponded to intraoperatively inspected atherosclerotic lesions of UIAs (sensitivity, 0.90; specificity, 0.79). Among hemodynamic parameters, oscillatory velocity index that suggests the directional changes of the flow velocity was significantly higher in UIAs with AWE (p=0.02). Histopathologic studies revealed that wall thickening accompanied by atherosclerosis, neovascularization, and macrophage infiltration corresponded to AWE lesions, while UIAs without AWE demonstrated various histopathological findings such as myointimal hyperplasia or thinning wall with loss of mural cells and wall degeneration. Conclusions: Pathophysiology of AWE could be explained as atherosclerotic changes with inflammation presumably associated with aberrant flow conditions in irregular UIAs. VWI and CFD are complementarily valuable imaging techniques to understand an aneurysm wall pathophysiology.