Health A-Z

Medical Content Created by the Faculty of the
Harvard Medical School

Intracranial Aneurysms

What Is It?

Arteries are tunnels that blood travels through to get from the heart to various parts of the body. An aneurysm is a bulge in an artery, similar to the bulge that appears at a weak spot of a hose, where the water pressure pushes out to create a bubble. Like the hose bubble, the area of an artery where an aneurysm appears is weak and has the potential to burst.

Aneurysms most frequently occur in the arteries that bring blood to the brain. Brain aneurysms are also known as intracranial aneurysms or berry aneurysms (because most of the time they look like little round berries). They occur in up to 6% of people. In general, most brain aneurysms are small, rarely cause symptoms and have a very low risk of rupture.

Women are more likely than men to develop brain aneurysms. A family history of aneurysm increases your risk of having one, as does being older than 50, currently smoking cigarettes, having high blood pressure, and using cocaine. About 20% of people with one brain aneurysm will have at least one more.

A number of inherited conditions also increase the chance of having an aneurysm, including:

• Polycystic kidney disease

• Ehlers-Danlos syndrome

• Neurofibromatosis

• Pseudoxanthoma elasticum

• Hereditary hemorrhagic telangiectasia

• Alpha₁-antitrypsin deficiency

• Coarctation of the aorta

• Fibromuscular dysplasia

• Pheochromocytoma

• Klinefelter's syndrome

• Tuberous sclerosis

• Noonan's syndrome

• Alpha-glucosidase deficiency

If a brain aneurysm does rupture, the consequences can be life threatening. The risk of rupture is higher with larger aneurysms. Those that are one-fourth of an inch (10 mm) or smaller are generally at low risk of rupture.