Comparison of the Prevalence of Ruptured and Unruptured Cerebral Aneurysms in a Poor Urban Minority Population

Background: Most ruptured cerebral aneurysms are small (< 7mm). Evidence suggests low rupture rates for such lesions (< 1% per year). Population studies demonstrate a prevalence rate of 3.2%. This study simultaneously estimates the prevalence of aneurysms in a single geographic population while reporting the observed rate of aneurysmal subarachnoid hemorrhage (aSAH) in the same geographic region composed of a poor urban minority demographic. Methods: This is an institutional review board-approved, Health Insurance Portability and Accountability Act of 1996-compliant retrospective study performed between 2005 and 2011 at a single center. Part 1 used the electronic medical record to identify all patients with a magnetic resonance angiography demonstrating a cerebral aneurysm. Part 2 used the electronic medical record to identify all patients from the same geographic area presenting with aSAH during the study period. Results: A total of 11,160 subjects had a magnetic resonance angiography from the study area. In this group, 422 intradural cerebral aneurysms were incidentally discovered. Ninety-one percent were less than 10 mm (mean 5.49, standard deviation 4.6). Twenty-one percent were aneurysms of the anterior communicating artery complex. Fourteen percent were of posterior communicating artery origin. A total of 237 patients had aSAH. Ninety-two percent of the aneurysms were less than 10mm (mean 6 mm, standard deviation 3.2 mm). Both groups were composed of poor urban minority patients. Conclusions: The observed annual rate of rupture of small anterior circulation aneurysms in this study was .06%-.15% per year. The extrapolated population prevalence of such aneurysms (4.0%-1.5%) may explain the observed rate of rupture of these small aneurysms in a poor urban minority population.