Analysis of rupture during follow-up of unruptured aneurysm

Shinya Koyama, Mizuho Inoue, Hiroki Uchida, Kuniyasu Niizuma, Atsushi Saito, Hiroyuki Kon, Tatsuya Sasaki, Michiharu Nishijima

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)523-529
Number of pages7
JournalNeurological Surgery
Issue number6
Publication statusPublished - 2015 Jun 1


  • Risk factor
  • Subarachnoid hemorrhage
  • Unruptured cerebral aneurysm


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