Unruptured Intracranial Aneurysms

Abstract

Backgrounds and Purpose-The authors evaluated the incidence of rupture of unruptured intracranial saccular aneurysm during observation. Methods-Between January 2003 and December 2006, a total of 419 patients with 529 unruptured intracranial saccular aneurysms were observed without treatment. The mean follow-up duration was 905.3 days. Aneurysm size was measured by 3-dimensional CT angiography. Clinical and 3-dimensional CT angiography follow-up were obtained every 6 months. Results-Nineteen aneurysms ruptured during observation resulting in a 1.4% rupture rate per year. A history of subarachnoid hemorrhage (hazard ratio, 7.3; 95% CI, 2.5 to 21.2), posterior circulation aneurysm (hazard ratio, 2.9; 95% CI, 1.1 to 8), and large size were significant independent predictors for aneurysm rupture. Conclusions Clinical Materials and MethodsFrom January 2003 through December 2006, a total of 419 patients with 529 UIAs were referred to our institution. Patient information and clinical presentation is summarized in Table 1.Size of the UIAs was measured by 3-dimensional CT angiography (Sensation16, Siemens, Germany). Based on the findings of 3-dimensional CT angiography, all UIAs were classified into the following categories: small (S; 0 to 4.9 mm in diameter), medium/ small (MS; 5 to 9.9 mm in diameter with small neck (0 to 3.9 mm), medium/wide (MW; 5 to 9.9 mm in diameter) with a wide neck (Ͼ4 mm), large (L; Ͼ10 mm), and giant (G; Ͼ25 mm). These aneurysms were followed by 3-dimensional CT angiography every 6 months.Data were analyzed using the biomedical data package statistical program (Version 7.0; BMDP Statistical Software, Inc, University of California, Los Angeles, Calif). Categorical variables were compared using the Fisher exact 2-tailed test, the Pearson 2 test, or the test for determining linear trend. Continuous variables were compared among groups by using the Mann-Whitney U test or the Student t test. For life-table analysis and Cox proportional hazards regression model, each patient was followed to the time of subarachnoid hemorrhage (SAH), death due to causes other than SAH, or to the last possible follow-up contact. The average annual incidence of SAH was calculated by determining the number of first-event SAH divided by the number of person-years of follow-up. Cumulative rates of SAH were estimated using the Kaplan-Meier product-limit method. ResultsNineteen aneurysms ruptured during the follow-up period. The annual incidence of SAH was 1.4% during observation. Incidence of rupture was strongly correlated with aneurysm size. The annual rupture rate by size classification was 0.8% (S), 1.2% (M), 7.1% (L), and 43.1% (G), respectively. Details of ruptured aneurysms under conservative observation are summarized in Table 2.In patients with a history of SAH, the hazard ratio (HR) was 7.3 (95% CI, 2.5 to 21.2, PϽ0.001). Particularly in S-sized UIAs, 2 of 8 (25%) were associated with a history of SAH. The risk of rupture in S-sized UIAs with a history of SAH was 5.5 (95% CI, 0.9 to 32.4) compared with patients ...

Quantifying Intracranial Aneurysm Wall Permeability for Risk Assessment Using Dynamic Contrast-Enhanced MRI: A Pilot Study

“…The largest prospective study to date on unruptured IAs, the International Study of Unruptured Intracranial Aneurysms (ISUIA), indicated lower rupture rates than previously suspected. 2 However, multiple subsequent reports challenged these findings, 3,4 thus further complicating management decisions. The exact pathogenesis and pathoevolution of IAs is largely unknown, with only a fraction of IAs progressing to rupture annually (Ͻ2%), suggesting potential differences in the pathobiology of ruptured-versus-unruptured IAs.…”

Complement system becomes activated by the classical pathway in intracranial aneurysm walls

“…2 Known risk factors for IA rupture and SAH include smoking, hypertension, previous rupture, female gender, excessive alcohol abuse and family history, but these explain only part of the IA disease. 3,4 Inflammation and its key component complement activation precede IA rupture. Inflammatory cell infiltration and deposits of the activation products of the terminal complement pathway can be found in unruptured IAs.…”

Justification of Unruptured Intracranial Aneurysm Repair: A Single-Center Experience

“…Recent large studies also reported relatively low rupture rates for small UIAs. 3,4 Since the publication of these studies, the management strategy for UIAs has tended to be conservative. However, larger UIAs, which are associated with a higher risk for rupture, usually benefit from preventive treatment.…”