Natural history of untreated unruptured intracranial aneurysms in the elderly.

Background: The effect of age on risk of intracranial aneurysm rupture is not well understood. We investigated the clinical course of patients 65 years and older with conservatively managed unruptured intracranial aneurysms (UIA) and determined risk factors for rupture in this population.

Methods: We reviewed prospectively collected data on baseline characteristics and long-term follow-up for patients aged 65 years and older with an UIA that were initially managed with observation. The association between patient and aneurysmal characteristics and risk of rupture was performed using a multivariate Cox proportional hazard regression model.

Results: There were 214 patients (mean age: 74.7 years, SD: 6.0) included in our study. The median follow-up time was 3.7 years, with a cumulative follow-up time of 883.7 person-years. During the study period, seven patients (3.3%) received interventional treatment of their UIA and eight patients (3.7%) experienced aneurysmal subarachnoid hemorrhage, yielding an annual risk of rupture of 0.9%. All aneurysms that ruptured were at least 10 mm in size. Increasing patient age [unit relative risk (RR) 1.19, 95% CI: 1.07-1.36, P=0.002], larger aneurysmal size (unit RR 1.10, 95% CI: 1.02-1.17, P=0.021), and increasing PHASES Score (unit RR 1.62, 95% CI: 1.32-2.06, P<0.001) were associated with higher risk of rupture.

Conclusions: Our data do not suggest that UIA in older patients carry a high risk of rupture. A conservative approach appears justified in these patients, with the exception of selected patients with larger aneurysms (>10 mm in diameter) and low risk of interventional procedure.