Analysis of rupture during follow-up of unruptured aneurysm

Object: To elucidate clinical aspects of ruptured aneurysms, we retrospectively investigated associations between risk factors and ruptured and unruptured cases during conservative management. Methods: Two hundred and twenty-nine patients with 291 unruptured cerebral aneurysms treated between 2000 and 2012 were analyzed. Mean duration of observation was 62 months (1183.4 person-years). We investigated the following six risk factors : history of subarachnoid hemorrhage ; multiplicity; location of aneurysms ; aneurysm size ≤5 mm ; bleb or irregular forms ; and follow-up period <1 year. Results: Twenty-two aneurysms in 22 patients (19 women ; 86.4%) ruptured during this study. The annual rate of rupture was 1.86%. In ruptured cases, mean age was 66.7 years. According to univariate analysis, aneurysm size ≥5 mm (p = 0.000), bleb or irregular form (p = 0.006) and duration of observation <1 year (p = 0.000) were significantly associated with aneurysmal rupture. In multivariate analysis of these factors, aneurysm size ≥5 mm (p = 0.0188 ; odds ratio (OR), 3.4 ; 95% confidence interval (Cl), 1.2-9.7) and duration of observation <1 year (p = 0.006 ; OR, 5.0 ; 95% CI, 1.6-14.9) represented independent risk factors for aneurysm rupture. Conclusions: The results of this study were almost the same as those of the UCAS Japan study. In addition, duration of observation <1 year was a risk factor for aneurysm rupture. When we decide on surgical treatment after considering factors such as aneurysm size, form, and surgical risk, surgery should be performed as soon as possible.