Risk of Rupture of Unruptured Intracranial Aneurysms in Relation to Patient and Aneurysm Characteristics

Abstract

Background and Purpose-We updated our previous review from 1996 on the risk of rupture of unruptured intracranial aneurysms, aiming to include the newly published articles. Methods-We reviewed all studies from our former meta-analysis and performed a Medline search for new studies published after 1996. We calculated overall risks of rupture for studies with a mean follow-up time of Ͻ5, 5 to 10, and Ͼ10 years. Relative risks (RR) were calculated by comparing the risk of rupture in patients with and without potential risk factors. We aimed to perform multivariable analyses of the different risk factors with meta-regression analysis. Results-We included 19 studies (10 new) with 4705 patients and 6556 unruptured aneurysms (follow-up 26 122 patient-years). The overall rupture risks were 1.2% (follow-up Ͻ5 years), 0.6% (follow-up 5 to 10 years), and 1.3% (follow-up Ͼ10 years). In the univariable analysis, statistically significant risk factors for rupture were age Ͼ60 years (RR 2.0; 95% confidence interval [CI], 1.1 to 3.7), female gender (RR 1.6; 95% CI, 1.1 to 2.4), Japanese or Finnish descent (RR 3.4; 95% CI, 2.6 to 4.4), size Ͼ5 mm (RR 2.3; 95% CI, 1.0 to 5.2), posterior circulation aneurysm (RR 2.5; 95% CI, 1.6 to 4.1), and symptomatic aneurysm (RR 4.4; 95% CI, 2.8 to 6.8). Meta-regression analysis yielded implausible results. Conclusions-Age, gender, population, size, site, and type of aneurysm should be considered in the decision whether to treat an unruptured aneurysm. Pooled multivariable analyses of individual data are needed to identify independent risk factors and to provide more reliable risk estimates for individual patients.

The Merits of Endovascular Coil Surgery for Patients with Unruptured Intracranial Aneurysms

“…In patients with unruptured aneurysms, the decision whether to treat is often clear. According to Marieke et al 21) , characteristics that increase the risk of aneurysm rupture include posterior circulation localization, size ＞5 mm, and symptoms other than those related to SAH. Based on the available literature, we believe that patients with unruptured aneurysms and the following characteristic should be treated : SAH from another aneurysm, symptomatic aneurysm, aneurysm larger than 10 mm in diameter, and aneurysms between 6 and 9 mm in diameter if the patient is young or middle-aged 8) .…”

“…Clipping of unruptured aneurysms is associated with a mortality of 2.6% and a morbidity of 10.9% 21) . For surgical clipping of proximal ICA and posterior circulation aneurysms, aggressive surgical manipulation is needed, including exposure of the cervical ICA and a skull base approach.…”

“…The management of UIAs remains controversial because of incomplete and conflicting data concerning the natural history of these lesions and the risks associated with their repair 21) . The standard method of treatment for intracranial aneurysms is surgical clipping 14) .…”

Managing Unruptured Aneurysms: The Ethical Solution to the Dilemma

“…Two thousand participants are equally allocated to observation versus coiling. Observed patients suffer no initial morbidity, but present a poor outcome from ruptures at a rate of 0.8%/year (1.2%/year with 70% morbidity/mortality) 3 , for a total of 76 at 10 years. The endovascular group has an initial poor outcome (mRS >2) of 3% 11 and a rate of yearly events of 0.1% (0-0.2%; this is the main test for coiling, whether it holds on the long run), for a total of Worse, a trial lumping clipping and coiling forbids any comparison between clipping and observation, or coiling and observation.…”

“…From 1966 to 2005, our literature reported on 4705 patients with UIAs; only 2517 have been followed prospectively 3 . There was no Randomized Controlled Trial (RCT).…”