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. 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.

  1. Family history. People with a family history of brain aneurysms are twice as likely to have an aneurysm as those who don't.
  2. Previous aneurysm. About 20% of patients with brain aneurysms have more than one.
  3. Gender. Women are twice as likely to develop a brain aneurysm or suffer a subarachnoid hemorrhage as men.
  4. Race. African-Americans have twice as many subarachnoid hemorrhages as whites.
  5. Hypertension. The risk of subarachnoid hemorrhage is greater in people with a history of high blood pressure (hypertension).
  6. Smoking. In addition to being a cause of hypertension, the use of cigarettes may greatly increase the chances of a brain aneurysm rupturing.