Patients with unruptured intracranial aneurysms at the waiting list for intervention: risk of rupture.

Unruptured intracranial aneurysms are usually not managed on an emergency basis, although for patients, uncertainty and waiting can be stressful. We assessed the incidence of aneurysms rupturing during the initial period of awareness of having an aneurysm. We studied all patients visiting our service with an unruptured intracranial aneurysm between January 2000 and March 2013. For the exposure time (time between diagnosis and discussion of treatment plan, together with time on waiting list for treatment), we calculated incidence of aneurysmal rupture with corresponding 95 % confidence intervals. We compared this incidence with expected incidence (based on size and site for each aneurysm). 398 patients were included; five had aneurysmal rupture during the exposure time. The observed incidence of aneurysmal rupture during exposure time was 47/1,000 patient-years (95 % confidence interval 15-111); the expected incidence was 0.7/1,000. Our data suggest that the risk of aneurysmal rupture early after detection of unruptured aneurysms is higher than expected based on aneurysm characteristics.