| My moms mother had a massive aerotic anerusim. My dads sister had a cranial... But an aneurism by definition is a weak bit in a vien or artery that may burst.
Here is a link
and here is a snippet from that link:
CAUSES
Any condition that causes arterial walls to weaken or deteriorate can result in an aneurism. The most common culprits are atherosclerosis and high blood pressure. Penetrating wounds and infections can also lead to an aneurism. Some types, such as berry aneurisms, are the result of congenital, or inherited, weakness in artery walls.
Research has shown smoking and a high fat diet may cause or worsen this problem.
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My grandma's aneurism tho aeortic actually wasn't chest level it was fartherdown and distended her belly. My cousin(the ant that had the cranial aneruisms eldest child) had an aeortic aneurism farther up into his sternum(chestplate). He died at 19 when it "snapped" as back then they didn't have the graft surgery to replace sections that are weak with donated tissue or bits from other parts of the body.(or even synthetic I think they have now). There are artiers in numerous places in the body. Whats in your head when aneurisms occur isn't arteries they are capillaries afik. I've had a stroke from severe sunstroke and it's amazing what the body can recover from given the chance... Btw that link lists some symptoms of aneurisms. | 
