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, and the affected arteries and veins 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.

An arteriovenous malformation can develop anywhere in your body but occurs most often in the brain or spine. Read more about brain arteriovenous malformation.

The cause of AVMs is not clear. Most people are born with them, but they can occasionally form later in life. They are rarely passed down among families.

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

Arteriovenous malformation care at Mayo Clinic