Also known as a cerebral aneurysm or intracranial aneurysm, a brain aneurysm bulges out of a weakened spot in an artery wall. The weakening results from an abnormal loss of the tissue making up the muscular layer of the artery. If that weak area ruptures, blood flows into the brain cutting off oxygen to brain cells, a situation that can cause permanent disability or even be fatal.
While cerebral aneurysms may occur anywhere in the brain, most develop in the arteries in front. There are three types of brain aneurysm:
- Saccular aneurysm – sometimes called a berry aneurysm because of its round shape with a narrow stem.
- Dissecting aneurysm –a tear along the artery, usually caused by injury that allows blood to flow between the three layers of the artery wall; the aneurysm may bulge out of the wall or into the artery reducing blood flow.
- Fusiform aneurysm – a bulge on the entire circumference of the artery, generally related to atherosclerosis, the hardening of the artery walls
In about 90 percent of cases, a brain aneurysm is small, causes no symptoms and is less likely to rupture. The risk of a rupture is greater if the diameter of the aneurysm is larger than 10 millimeters (less than 1/2 inch), is located in the back area of the brain, and if the person has experienced a rupture before.