The Prevalence of Unruptured Cerebral Aneurysms in Okinoerabu: A Japanese Hospital-Based Study

Background: Unruptured cerebral aneurysms (UCAs) might lead to a poor outcome. However, the previously reported prevalence of UCAs in Japan ranges widely. Method: The objects of this retrospective and hospitalbased study were adult residents of Okinoerabu, a small island in Japan. We performed the examination of the brain with 1.5-Tesla MR angiography (MRA) from December 2017 to May 2018 at Okinoerabu Tokushukai Hospital. We estimated the prevalence of UCAs and investigated the characteristics of UCAs. Results: Thirty UCAs were found in 27 of 356 persons. 3 persons had multiple UCAs. The overall prevalence was 7.6% (Men 7.3%; Women 7.8%). Except for one person, UCAs were identified in those over 50 years old and women in 5th decade showed the highest prevalence (14.3%). More than half of UCAs located in the internal carotid artery (ICA, 56.7%). Most UCAs had a maximum diameter less than 4.9 mm (93.3%). Conclusion: The overall prevalence of UCAs in Okinoerabu was comparatively high on Okinoerabu. The characteristics of UCAs were as follows: over 5th decade, in ICA, and smaller than 4.9 mm.