Focal Aneurysm Wall Enhancement in Vessel Wall Imaging as a Surrogate Marker for Predicting Aneurysm Instability.

Background: The establishment of a risk stratification method for unruptured intracranial aneurysms (UIAs) remains an interdisciplinary challenge. The present study attempted to identify unstable UIAs using magnetic resonance vessel wall imaging in prospective data sets. Hemodynamic parameters in unstable UIAs were also examined to clarify the mechanisms by which segmented aneurysm wall enhancement (AWE) affects longitudinal morphological changes. Methods: Patients with UIAs who underwent contrast-enhanced vessel wall imaging between 2017 and 2022 and were followed up for more than 6 months were included. Two readers independently rated AWE patterns (no, focal, and circumferential AWE) on vessel wall imaging and morphological changes on time-of-flight magnetic resonance angiography. Computational fluid dynamics studies were performed on unstable UIAs to evaluate the hemodynamic features of evolved or ruptured points in aneurysm walls. Results: Aneurysm growth was observed in 13 of 114 UIAs in the present study during a median follow-up of 34 months. Of the 13 growing UIAs, their AWE patterns were as follows: no AWE in 6 and focal AWE (FAWE) in 7 UIAs. Univariable Cox regression analysis showed that aneurysm size and FAWE were associated with aneurysm growth. On multivariable Cox regression analysis, FAWE (hazard ratio, 4.59 [95% CI, 1.29-16.3]; Conclusion: FAWE may be associated with aneurysm growth and rupture during follow-up. A comprehensive analysis of nonenhanced areas of UIAs with FAWE using vessel wall imaging and computational fluid dynamics provides insights into the mechanisms underlying aneurysm instability.