Aneurysms
This is a weak spot on an artery that has bulged out. The walls of an aneurysm can burst because they are thin and weak from being stretched. Some people are born with an aneurysm; others may develop one during their lifetime. Some factors that increase the risk of developing an aneurysm are smoking, high blood pressure, a family history of aneurysms and using illegal drugs.
Arteriovenous Malformation (AVM)
An arteriovenous malformation (AVM) is an abnormal tangle of blood vessels connecting arteries and veins.
Arteries are responsible for taking oxygen-rich blood from the heart to the brain. Veins carry the oxygen-depleted blood back to the lungs and heart.When an AVM is present, the affected arteries and veins can weaken and rupture. If the AVM is in the brain and ruptures, it can cause bleeding in the brain (hemorrhage), stroke or brain damage.
The cause of AVMs is not clear. Most people are born with them, but they can occasionally form later in life.