A brain aneurysm is a ballooning-out of the wall of an artery in the brain. Often this wall is weakened by disease, injury or an abnormality present at birth. Aneurysms are often caused or made worse by high blood pressure. They aren't always life-threatening, but serious consequences — such as a stroke — can result if one bursts in the brain. This is called a hemorrhagic (or bleeding) stroke.

When a blood vessel on the brain's surface ruptures and bleeds into the space between the brain and the skull (but not into the brain tissue itself), it's called a subarachnoid hemorrhage.

How is an aneurysm detected?

Several imaging techniques, such as X-ray angiography, MRI (magnetic resonance imaging) or computed tomography (CT), are used to detect aneurysms. An aneurysm may be small and not cause symptoms. A doctor will want to check it regularly to see if it's enlarging. Symptoms of an aneurysm depend on where it's located. Aneurysms in the brain can cause impaired vision and headaches. The larger an aneurysm becomes, the more likely it is to burst.

How is an aneurysm treated?

Brain aneurysms are generally treated surgically. A metal clip is secured around the base of the aneurysm. Another type of treatment involves 'packing' the aneurysm with microcoils (small, flexible wire coils). These are delivered and inserted into the aneurysm using a catheter.

For stroke information, call the American Stroke Association at 1-888-4-STROKE.

If you or someone you know has a brain aneurysm or has had a hemorrhagic stroke, call 1-888-4-STROKE and ask for the Stroke Family Support Network.

Related AHA and ASA publications:

• Stroke: Are You at Risk? (also in Spanish on ASA Web site)
• Warning Signs of Stroke (Quick and Easy Reading) (also in Spanish on ASA Web site)
• Sheets from Let's Talk About Stroke kit

Related AHA Scientific Statements:
Aneurysm