An AVM rupture occurs when an arteriovenous malformation (AVM) ruptures and bleeds into the brain or surrounding tissues, reducing blood flow to the brain. An AVM is an abnormal tangle of blood vessels that irregularly connects arteries and veins, disrupting blood flow and oxygen circulation. The exact cause of cerebral AVM is unknown, but researchers believe most brain AVMs are present at birth and form during fetal development. Some people with a brain AVM experience signs and symptoms, such as headaches or seizures, while others may have no symptoms until they have a bleeding event. The biggest risk of having an AVM is that it might bleed, causing a stroke, brain damage, or seizures. Fewer than 4% of AVMs hemorrhage, but those that do can have severe, even fatal, effects. An AVM can be treated to prevent complications, such as brain damage or stroke. Treatment options include surgery, radiation therapy, and embolization.