Overview

An arteriovenous malformation (AVM) is an abnormal tangle of blood vessels connecting arteries and veins, which disrupts normal blood flow and oxygen circulation.

Arteries are responsible for taking oxygen-rich blood from the heart to the brain. Veins carry the oxygen-depleted blood back to the lungs and heart.

When an AVM disrupts this critical process, the surrounding tissues may not get enough oxygen. Also, because the tangled blood vessels that form the AVM are abnormal, they can weaken and rupture. If the AVM is in the brain and ruptures, it can cause bleeding in the brain (hemorrhage), stroke or brain damage.

The cause of AVMs is not clear. They're rarely passed down among families.

Once diagnosed, a brain AVM can often be treated successfully to prevent or reduce the risk of complications.