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Brain & Nervous System Health Center

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Brain Aneurysm - Topic Overview

What is a brain aneurysm?

A brain (cerebral) aneurysm is a bulging, weak area in the wall of an artery that supplies blood to the brain. In most cases, a brain aneurysm causes no symptoms and goes unnoticed. In rare cases, the brain aneurysm ruptures, releasing blood into the skull and causing a stroke.

When a brain aneurysm ruptures, the result is called a subarachnoid hemorrhage. Depending on the severity of the hemorrhage, brain damage or death may result.

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The most common location for brain aneurysms is in the network of blood vessels at the base of the brain called the circle of Willis.

What causes a brain aneurysm?

A person may inherit the tendency to form aneurysms, or aneurysms may develop because of hardening of the arteries (atherosclerosis) and aging. Some risk factors that can lead to brain aneurysms can be controlled, and others can't. The following risk factors may increase your risk for an aneurysm or, if you already have an aneurysm, may increase your risk of it rupturing:

  • Family history. People who have a family history of brain aneurysms are more likely to have an aneurysm than those who don't.
  • Previous aneurysm. People who have had a brain aneurysm are more likely to have another.
  • Gender. Women are more likely to develop a brain aneurysm or to suffer a subarachnoid hemorrhage.
  • Race. African Americans are more likely than whites to have a subarachnoid hemorrhage.
  • High blood pressure. The risk of subarachnoid hemorrhage is greater in people who have a history of high blood pressure.
  • Smoking. In addition to being a cause of high blood pressure, the use of cigarettes may greatly increase the chances of a brain aneurysm rupturing.

What are the symptoms?

Most brain aneurysms cause no symptoms and may only be discovered during tests for another, usually unrelated, condition. In other cases, an unruptured aneurysm will cause problems by pressing on areas in the brain. When this happens, the person may suffer from severe headaches, blurred vision, changes in speech, and neck pain, depending on what areas of the brain are affected and how bad the aneurysm is.

Symptoms of a ruptured brain aneurysm often come on suddenly. If you have any of the following symptoms or notice them in someone you know, call 911 or other emergency services right away:

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