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