Long-term Outcome of Unruptured Cerebral Aneurysms

BACKGROUND: The frequency at which unruptured cerebral aneurysms are detected has increased due to advances in low- or non-invasive diagnostic techniques. Despite the recent improvements in surgical and medical management of aneurysmal subarachnoid hemorrhages, however, the overall case-fatality rate of this disease is still high. To reduce it, the natural history of unruptured cerebral aneurysms should be better understood. METHODS: The subjects consisted of 156 patients with unruptured cerebral aneurysms who had been admitted to the Department of Surgical Neurology, Jichi Medical School Hospital or Jichi Medical School Ohmiya Medical Center, Japan, between January 1989 and December 1998. All of the patients were classified according to the process by which aneurysms had been detected. The expected number of deaths was calculated by using age- and sex-specific mortality rates obtained from the vital statistics. A standardized mortality ratio and 95% confidence interval were calculated by using the expected and observed numbers of deaths. RESULTS: The standardized mortality ratios differed among the groups according to the process of detecting aneurysms. The incidence rate of rupture of unruptured cerebral aneurysms was 1.3 per 100 person-years. The annual rupture rate of unruptured cerebral aneurysms was higher than previously reported. The survival rate of the group that underwent surgical treatment for unruptured cerebral aneurysms was higher than that of the untreated group. CONCLUSIONS: The annual rupture rate of unruptured cerebral aneurysms may be higher than previously reported.