De novo aneurysm: case reports and literature review.

Background And Importance: Formation of cerebral de novo aneurysms (CDNAs) is rare, and the pathogenesis remains obscure. We analyzed factors involved in formation of CDNAs and suggest guidelines for follow-up of patients.

Clinical Presentation: We retrospectively reviewed intracranial aneurysms at our institute and published reports from 1964 to 2008. Eleven patients were found with CDNAs, and 138 patients were collected from the published literature. We assessed the clinical characteristics, such as sex, size, and site of CDNA, past history, and time to occurrence of CDNAs. Of 11 patients, 10 were female and 1 was male; the mean age of the first onset was 53 years (range, 25-69 years). The mean time between first aneurysms and CDNAs was 10.6 years (range, 3-29 years). The most common site of occurrence was anterior circulation. One patient experienced contralateral occurrence, and 2 patients changed from anterior to posterior circulation CDNAs. Six (54.5%) patients had a history of arterial hypertension. Results from analysis of the whole series from the literature revealed that the risk of rupture increased with a previous history of hemorrhage. Contralateral occurrence of CDNAs was related to previous location, and multiplicity, whereas the occurrence of anterior to posterior changes of CDNAs and shorter interval only correlated with an older age group.

Conclusion: Although the formation of CDNAs is rare, several factors may contribute to its occurrence. Female patients with a history of arterial hypertension were at a higher risk for CDNA occurrence. We recommend follow-up imaging studies within 10 years after the initial aneurysms; therefore, at least 50% of CDNAs can be found before rupture.