A ten percent prevalence of asymptomatic familial intracranial aneurysms: preliminary report on 110 magnetic resonance angiography studies in members of 21 Finnish familial intracranial aneurysm families.

The population in eastern Finland has been stable for generations, causing a high degree of genetic isolation and providing excellent possibilities for follow-up studies. Of 91 families with familial intracranial aneurysms, 21 were randomly selected for prospective magnetic resonance angiography studies for intracranial aneurysms. Sixteen intracranial aneurysms were detected in 11 asymptomatic family members of a total of 110 studied. The prevalence of intracranial aneurysms among these familial intracranial aneurysm families is 10%, approximately 10 times higher than in the average population. Our findings suggest that family members of familial intracranial aneurysm families should be examined for intracranial aneurysms. Familial intracranial aneurysm may be a genetic disorder.