The prevalence of incidental intracranial aneurysms in general population, in families with one, and in families with two or more known subarachnoid hemorrhage cases

Introduction: The overall outcome of the aneurysmal subarachnoid hemorrhage (SAH) has not changed during the last decades; half of the patients die. In East Finland the incidence of aneurysmal SAH is among the highest in the world. The aim of our study was to estimate the prevalence of incidental I.A.S. in East Finland in the age group 30 years or older in three different groups: 1. General population 2. First-degree relatives in families with one known aneurysmal SAH case (sporadic cases), and 3. First-degree relatives in families with two or more known aneurysmal SAH cases (familial cases). Methods: Prospective forensic autopsy study was carried out to estimate the prevalence of incidental las in general population in East Finland. During the routine forensic autopsy study the Circle of Willis was studied for las by forensic doctors. Patients with previous SAH or in whom ruptured IA was found to be the reason for death were excluded from this study. In families with one or more known las cases, magnetic resonance angiography (MRA) was used as a preliminary screening method of IAs, followed by intra-arterial digital subtraction angiography (ia-DSA) to verify suspected aneurysms. Results: In general population (5.0%) incidental las cases were found. In families with one known aneurysmal SAH case prior to screening (3.8%), and in families with two or more known aneurysmal SAH cases prior to screening (8.7%) incidental las cases were found. The age and gender adjusted prevalence rates were 4.3% (95% Cl 3.5-5.0%), 4.5% (95% Cl 2.8-5.2%), and 9.3% (95% Cl 8.3-10.0%), respectively. Conclusions: For the first time the prevalence of incidental las has been studied in three different risk groups in the defined geographical area. Our result confirms earlier reports, that in familial cases asymptomatic first-degree relatives have an increased risk for las compared to the other study groups. Screening and preventive treatment of las should be focused only in familial cases.