An arteriovenous malformation (AVM) is a tangle of abnormal formed blood vessels connecting arteries and veins. Arteries are responsible for taking oxygen-rich blood from the heart to brain, while veins carry the oxygen-depleted blood back to the lungs and heart. When an AVM disrupts this process, tissues may not get enough oxygen and cause the arteries and veins to rupture. If the location of the AVM is in the brain and ruptures, it can cause bleeding on the brain. Most people with arteriovenous malformation experience no symptoms at all. If symptoms do occur they consist of headaches, dizziness, seizures, and sensations such as numbness and tingling. Brain AVMs occur in less than 1% of the population. There is no known cause to AVMs.