van der Kamp LT, Rinkel GJE, Verbaan D, et al. - In this cohort study involving 312 patients (223 [71%] were women; mean [SD] age, 61 [12] years) with aneurysms with growth, a rupture occurred in about 1 of 25 aneurysms within 1 year after growth detection. The triple-S risk prediction model can be used to estimate the absolute risk of rupture during the initial period following growth detection.

• During a total of 864 aneurysm-years of follow-up, 25 (7.6%) of these aneurysms ruptured.

• At 6 months, the absolute risk of rupture was 2.9%, 4.3% at 1 year, and 6.0% at 2 years.

• Size (7 mm or larger hazard ratio, 3.1), shape (irregular hazard ratio, 2.9), and site (middle cerebral artery hazard ratio, 3.6; anterior cerebral artery, posterior communicating artery, or posterior circulation hazard ratio, 2.8) were all predictors of rupture in multivariable analysis.

• The 1-year risk of rupture in the triple-S (size, site, shape) prediction model ranged from 2.1% to 10.6%.