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May also be called: Brain AVM, AVM – Cerebral, Spinal AVM

An arteriovenous malformation (ar-TEER-ee-oh-VEE-nus mal-for-MAY-shun), or AVM, is a tangle of blood vessels that have an abnormal connection between the arteries and the veins.

More to Know

Arteries carry red, oxygen-rich blood from the heart to all parts of the body. Once the body parts have used the oxygen, veins carry the blue, oxygen-poor blood back to the heart. A network of tiny capillaries connects the arteries and veins. The capillaries are one of the most important parts of the circulatory system. They deliver nutrients and oxygen to the cells and remove waste products such as carbon dioxide. When someone has an AVM, it means the capillaries are missing in a small tangle of arteries and veins. The artery and vein become connected directly, causing blood to flow more quickly in these areas.

AVMs typically form when a baby is still a fetus, and doctors don’t know the cause. They can be found anywhere in the body, but they’re usually only a problem if they affect the brain or spinal cord (brain AVMs). Over time, a brain AVM can weaken the walls of the arteries or veins because blood is flowing so fast. This can lead to bleeding into the surrounding tissue. A brain AVM can also cause less oxygen to reach brain and spinal tissue because it flows through so fast that the oxygen can’t transfer to the tissue. The condition can also put pressure on the brain or spinal cord. This can cause headaches, seizures, muscle weakness or paralysis, and a range of neurologic issues, from dizziness to problems with vision and coordination.

Most brain AVMs cause no symptoms and are only discovered during treatment for another condition. However, a small percentage can cause serious and even life-threatening problems, such as strokes, brain damage, and bleeding in the brain. Whether and how to treat an AVM is decided on a case-by-case basis and depends on a person’s age, the location and size of the AVM, and whether a person has had bleeding in the brain. AVMs can often be removed through surgery. Other treatments for brain AVMs include procedures that block the arteries in the AVM to stop blood flow.

Keep in Mind

Most arteriovenous malformations aren’t a health concern. Only about 1 in 10 people with a brain AVM will have symptoms that may require treatment. Treatment is often successful if the AVM is diagnosed and treated before it can cause any neurologic damage. Damage that has already been done usually can’t be reversed.

All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.

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