Seventeen genetic abnormalities that cause brain aneurysms. Intracranial aneurysm is a dilation of a blood vessel forming a fragile pocket. Rupture results in extremely severe hemorrhage. Researchers have examined the genome of more than 10,000 people suffering from aneurysms. 17 genetic abnormalities have been identified, notably involved in the functioning of the vascular endothelium. Source 1e.