A cerebral aneurysm is an abnormal swelling of a blood vessel wall inside the brain.

What is going on in the body?

A cerebral aneurysm is an area where a blood vessel in the brain weakens. As a result, the vessel wall balloons out. This results from defects in the elastic layer of the blood vessel wall. Aneurysms usually form where arteries branch. The vessel wall is sometimes weaker at this branch. When pulsating blood pushes this area of weakness outward, an aneurysm forms. Over time, the aneurysm may balloon and thin the wall so much that it ruptures.

What are the causes and risks of the condition?

Aneurysms are often congenital. That means a person is born with them. As the person gets older, the aneurysm may get larger. High blood pressure and atherosclerosis, also known as hardening of the arteries, can further weaken the blood vessel walls. This may lead to an aneurysm, particularly in the elderly. Although rare, sometimes an aneurysm can be caused by an infection in the blood. The infection can lodge in the vessel wall and weaken it.

The first rupture of an aneurysm may lead to stroke, permanent disability, or death. Recurring bleeding and blood vessel spasm may also lead to death.