PHASES Score for Prediction of Intracranial Aneurysm Growth

Growth of an intracranial aneurysm occurs in around 10% of patients at 2-year follow-up imaging and may be associated with aneurysm rupture. We investigated whether PHASES, a score providing absolute risks of aneurysm rupture based on 6 easily retrievable risk factors, also predicts aneurysm growth.

In a multicenter cohort of patients with unruptured intracranial aneurysms and follow-up imaging with computed tomography angiography or magnetic resonance angiography, we performed univariable and multivariable Cox regression analyses for the predictors of the PHASES score at baseline, with aneurysm growth as outcome. We calculated hazard ratios and corresponding 95% confidence intervals (CI), with the PHASES score as continuous variable and after division into quartiles.

We included 557 patients with 734 unruptured aneurysms. Eighty-nine (12%) aneurysms in 87 patients showed growth during a median follow-up of 2.7 patient-years (range 0.5-10.8). Per point increase in PHASES score, hazard ratio for aneurysm growth was 1.32 (95% CI, 1.22-1.43). With the lowest quartile of the PHASES score (0-1) as reference, hazard ratios were for the second (PHASES 2-3) 1.07 (95% CI, 0.49-2.32), the third (PHASES 4) 2.29 (95% CI, 1.05-4.95), and the fourth quartile (PHASES 5-14) 2.85 (95% CI, 1.43-5.67).

Higher PHASES scores were associated with an increased risk of aneurysm growth. Because higher PHASES scores also predict aneurysm rupture, our findings suggest that aneurysm growth can be used as surrogate outcome measure of aneurysm rupture in follow-up studies on risk prediction or interventions aimed to reduce the risk of rupture.