Rupture risk increases after aneurysm growth is detected

Rupture occurred in one of 25 aneurysms within 1 year of intracranial aneurysm growth detection, according to results of a cohort study published in JAMA Neurology.

“Although the relative risk of rupture after detection of growth is increased, the absolute risk of rupture after detection of aneurysm growth is unknown,” Laura T. van der Kamp, MD, of the department of neurology and neurosurgery at the University Medical Center Utrecht Brain Center in the Netherlands, and colleagues wrote. “This absolute risk is pivotal for consultation with patients after detection of growth of the aneurysm because the risk of rupture needs to be weighed against the risk of treatment complications. The purpose of this multicenter cohort study was to determine the absolute risk of rupture of an aneurysm after detection of growth on follow-up imaging and to develop a prediction model for rupture based on predictors of rupture.”

The researchers analyzed data of patients aged 18 years or older from 15 international cohorts who had follow-up imaging for one or more untreated unruptured intracranial aneurysms with growth observed at follow-up imaging and with 1 day or longer of follow-up after growth. They excluded fusiform or arteriovenous malformation-related aneurysms. After excluding patients with no aneurysm growth detected or with less than 1 day of follow-up after growth detection, van der Kamp and colleagues included 312 patients (71% women; mean age, 61 years) with 329 aneurysms with growth, defined as 1 mm or greater increase in one direction at follow-up imaging.

Aneurysm rupture served as the primary outcome. The researchers used the Kaplan-Meier estimate at 6 months, 1 year and 2 years after initial growth to determine the absolute risk for rupture. Further, they identified predictors of rupture after growth detection using Cox proportional hazards regression.

Results showed 25 (7.6%) detected aneurysms ruptured during 864 aneurysm-years of follow-up. The researchers noted an absolute risk for rupture after growth of 2.9% (95% CI, 0.9-4.9) at 6 months, 4.3% (95% CI, 1.9-6.7) at 1 year and 6% (95% CI, 2.9-9.1) at 2 years. Rupture predictors included size (7 mm or larger HR = 3.1; 95% CI, 1.4-7.2), shape (irregular HR = 2.9; 95% CI, 1.3-6.5) and site (middle cerebral artery HR = 3.6; 95% CI, 0.8-16.3; anterior cerebral artery, posterior communicating artery or posterior circulation HR = 2.8; 95% CI, 0.6-13), according to multivariable analyses. The prediction model, called the triple-S because of its inclusion of size, site and shape, the 1-year risk for rupture ranged from 2.1% to 10.6%.

“Our triple-S prediction model can be used by physicians and patients as a starting point for discussing the pros and cons of preventive aneurysm treatment,” van der Kamp and colleagues wrote. “If it is decided to continue follow-up imaging, it seems reasonable to repeat imaging at a short interval, but actual data on the optimal time interval are lacking and should be gathered in future studies. Future data collection and studies are also needed to validate the prediction model.”