Gadolinium-Enhanced Aneurysm Wall Imaging and Risk of Intracranial Aneurysm Growth or Rupture.

Importance Recent longitudinal studies in patients with unruptured intracranial aneurysms (UIAs) suggested that aneurysm wall enhancement (AWE) on magnetic resonance imaging (MRI) predicts growth and rupture. However, because these studies were limited by small sample size and short follow-up duration, it remains unclear whether this radiological biomarker has predictive value for UIA instability. Objective To determine the 4-year risk of instability of UIAs with AWE and investigate whether AWE is an independent predictor of UIA instability. Design, Setting, and Participants Individual patient data were obtained from 3 prospective multicenter cohort studies conducted in 83 Chinese centers between January 2017 and December 2024. Included were patients aged 18 to 75 years with at least 1 asymptomatic, saccular UIA greater than or equal to 3 mm. Exposures All patients had 3-T MRI gadolinium-enhanced aneurysm wall imaging and computed tomography angiography (CTA) at baseline, and CTA at follow-up. Main Outcomes and Measures The primary outcome measure was aneurysm growth or rupture (instability) during follow-up. The absolute risk of aneurysm instability in UIAs with circumferential, focal, and no AWE was determined with Kaplan-Meier estimates at 4 years after baseline aneurysm wall imaging. Cox proportional hazards regression was used to investigate AWE as a potential predictor of instability. Results Of the 1453 patients who had baseline 3-T MRI aneurysm wall imaging, 41 patients were excluded because of loss to follow-up or no follow-up CTA, and 61 patients were excluded because of low-quality CTA. We included 1351 patients (median [IQR] age, 56 [48-63] years; 750 female [56%]) with 1416 UIAs and 4884 aneurysm-years of follow-up. Instability within 4 years occurred in 235 of 1416 UIAs (16.6%). The absolute cumulative risk of instability at 4 years was 36.8% (95% CI, 30.7%-43.0%) in UIAs with circumferential AWE, 17.2% (95% CI, 13.4%-21.1%) in UIAs with focal AWE, and 11.4% (95% CI, 11.9%-16.1%) in UIAs with no AWE. Circumferential AWE predicted 4-year instability (hazard ratio [HR], 3.80; 95% CI, 2.82-5.14) and after adjusting for size ratio, aneurysm location, aneurysm shape, and bifurcation configuration (adjusted HR, 2.21; 95% CI, 1.56-3.13). Conclusions and Relevance Within 4 years after baseline wall imaging, instability occurred in one-third of UIAs with circumferential AWE. These results suggest that MRI aneurysm wall imaging may be used for predicting the risk of aneurysm instability.