Estimating the annual rate of de novo multiple aneurysms: three statistical approaches.

Object: Individuals with unruptured intracranial aneurysms experience a higher rate of rupture if their history includes another aneurysm that has previously bled. The authors used systematic review and metaregression to estimate the annual rate of development of second de novo aneurysms after subarachnoid hemorrhage.

Methods: This investigation included studies in which more than 300 patients with intracranial aneurysms were described, and in which the age of the patients and the proportion with multiple aneurysms were documented. Studies describing delayed follow-up angiography that was performed after treatment of aneurysms were also reviewed. Twenty studies were included in a between-study analysis. The univariate odds ratio (OR) for multiple intracranial aneurysms per year of age was 1.085 (95% confidence interval [CI] 1.015-1.165); this value was calculated using a hierarchical model for between-study heterogeneity. Five studies were included that provided age stratification. The estimated OR for multiple intracranial aneurysms per year was 1.011 (95% CI 1.005-1.018). Four follow-up studies were available.

Conclusions: According to the three different approaches (study-level, patient-level, and follow-up analyses), the estimated annual rates of development of de novo aneurysms were 1.62% (95% CI 0.28-3.59%), 0.28% (95% CI 0.12-0.49%), and 0.92% (95% CI 0.64-1.25%), respectively. The estimated annual rate of development of second de novo aneurysms ranged from 0.28 to 1.62%.