Arteriovenous Malformation
An arteriovenous malformation (AVM) is an abnormal tangle of blood vessels that directly connects arteries to veins, bypassing the normal capillary system. This congenital vascular abnormality can occur anywhere in the body but most commonly affects the brain and spinal cord, creating a high-risk condition due to potential rupture and bleeding.
What is it?
An arteriovenous malformation (AVM) is a congenital abnormality where arteries connect directly to veins without the normal intervening capillary network. In a healthy vascular system, arteries carry oxygen-rich blood at high pressure, which then passes through tiny capillaries where oxygen and nutrients are exchanged with tissues, before the blood returns through low-pressure veins. In an AVM, this high-pressure arterial blood flows directly into veins, creating abnormal stress on the vessel walls and surrounding tissue.
Brain AVMs occur in approximately 1 per 100,000 people and are typically present from birth, though they usually become symptomatic between ages 20-40. The risk of hemorrhage (bleeding) from a brain AVM is approximately 2-4% per year, with potentially devastating consequences including stroke, permanent neurological damage, or death. AVMs can also cause symptoms without bleeding, including seizures (in 20-25% of patients), headaches, and progressive neurological problems due to “vascular steal” phenomenon, where the AVM diverts blood flow away from normal brain tissue.
Important to Know
Brain AVMs are serious conditions requiring evaluation by a specialized neurovascular team. Treatment decisions are complex and must weigh the risk of hemorrhage against the risks of treatment. Options include surgical resection (physically removing the AVM), endovascular embolization (blocking blood vessels feeding the AVM using catheters), stereotactic radiosurgery (focused radiation to gradually close the AVM), or a combination of these approaches. Some small, asymptomatic AVMs in low-risk locations may be managed with careful observation. The Spetzler-Martin grading system helps assess AVM complexity and surgical risk. Factors influencing treatment decisions include AVM size, location, patient age, previous hemorrhage, and symptoms. Early detection and appropriate management are crucial for optimizing outcomes.