What are Arteriovenous Malformations

Arteriovenous malformations are tangles of abnormal blood vessels. Arteriovenous malformations can form wherever arteries and veins exist. However, the ones that form in the brain or spinal cord can have especially severe effects.

Blood flows through arteries, bringing oxygen from the heart to the brain. The veins carry blood away from the brain to smaller blood vessels. These blood vessels slow the blood flow and allow oxygen to be delivered to the surrounding tissues.

Arteries in arteriovenous malformations don’t follow this pattern. They dump blood directly into veins through a channel called a fistula, an abnormal tube-like opening. The blood flow through this fistula is extremely fast. The cause of arteriovenous malformations is unknown. However, researchers believe that they occur as a fetus is developing and the arteriovenous malformations are present when you are born.