A brain AVM (arteriovenous malformation) is an abnormal connection between arteries and veins. An AVM is usually congenital, meaning it dates to birth.
An AVM can develop anywhere in your body but occurs most often in the brain or spine. A brain AVM, which appears as a tangle of abnormal arteries and veins, can occur in any part of your brain. The cause isn't clear.
You may not know you have a brain AVM until you experience symptoms, such as headaches or a seizure. In serious cases, the blood vessels rupture, causing bleeding in the brain (hemorrhage). Once diagnosed, a brain AVM can often be treated successfully.