Stratification of outcome for surgically treated unruptured intracranial aneurysms.

Abstract

The combination of low anticipated rupture rates for many unruptured aneurysms, better delineation of treatment risks, and the availability of alternative modalities of treatment have led to heightened scrutiny of the surgical management of unruptured intracranial aneurysms. Most reports to date have provided aggregate data concerning surgical treatment risks. This study was performed to better delineate risk estimates for the surgical treatment of patients with unruptured intracranial aneurysms according to a patient's risk profile with regard to age, aneurysm location, and aneurysm size. We studied 493 patients who were treated with surgical clipping of 604 unruptured saccular aneurysms. Information regarding aneurysm size, location, patient age, and 6-month or greater outcome were gathered prospectively from 1992 to 1999. Multivariate analysis was performed to identify independent risk factors for outcome. On the basis of the model, risk stratification curves were generated. In our series, the mean patient age was 53 years, and the mean lesion size was 8.8 mm. Lesion locations included the internal carotid artery (n = 259, 43%), the middle cerebral artery (n = 174, 28%), the anterior cerebral artery (n = 99, 17%), and the vertebrobasilar artery (n = 67, 11%). Multivariate analysis revealed that aneurysm size (beta = 0.122, P < 0.001), patient age (beta = 0.0308, P < 0.05), and vertebrobasilar location (beta = 1.37, P = 0.0080) were independently associated with high risk of poor outcome or death. Small aneurysms in the anterior circulation in young patients carry a very low treatment risk (approximately 1%), and treatment in elderly individuals (ages 70 years and older) with large lesions (greater than 10 mm), carries a significant risk of poor outcome (5% in the anterior circulation, 15% in the posterior circulation). The nomograms generated by this study should be particularly useful in discussing with patients the risks and benefits of surgical treatment of unruptured aneurysms.