Version July 2025
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What are arteriovenous malformations? —
Arteriovenous malformations, or "AVMs," are clumps of abnormal blood vessels. People can have AVMs in different places in their body. This article is about AVMs in the brain.
AVMs in the brain are rare and usually form before a person is born. Many times, they do not cause any symptoms. But in some people, they do cause serious symptoms or problems. These can happen if an AVM pushes on the brain or keeps part of the brain from getting enough oxygen. An AVM can also sometimes tear open and bleed into the brain. This happens because the blood vessels in an AVM are not as strong as normal blood vessels. A severe bleed in the brain can cause brain injury and death.
What are the symptoms of an AVM? —
Many AVMs do not cause any symptoms. People often find out they have one when their doctor does a test for another reason.
When AVMs do cause symptoms, they can cause:
●Seizures – These are waves of abnormal electrical activity in the brain. They can make you pass out, or move or behave strangely.
●Symptoms of a stroke – A stroke is when a part of the brain is damaged because of a problem with blood flow. A stroke can cause:
•The face to look uneven or droop to 1 side
•Weakness or numbness in 1 or both arms – For example, 1 arm might drift down if a person tries to hold both arms out.
•Trouble speaking, or speech that sounds strange
•Sudden, severe headache
●Headaches – Sometimes, an AVM is found when a person with headaches gets an imaging test to try to find the cause. (Imaging tests, like an MRI and CT scan, create pictures of the brain.) It is not always clear whether the AVM is the cause of the headaches, since headaches happen in many people who do not have an AVM.
Is there a test for an AVM? —
Yes. Doctors can do different tests to check for an AVM. Tests can include:
●CT or MRI scan of the brain
●CT angiography ("CTA") or magnetic resonance angiography ("MRA") – These use special types of CT and MRI scans to create pictures of the blood vessels in the brain. Doctors use a dye injection in CTA, and sometimes in MRA. The dye is a chemical that makes blood vessels show up on the test more clearly.
●Cerebral angiography – This shows how blood flows through the blood vessels in the brain. The doctor puts a thin tube into a large blood vessel in the body, usually one in the leg. Then, the doctor moves the tube up into the neck. When the tube is in place, they inject a dye into the tube and take X-rays. The dye shows up on the X-rays.
How is an AVM treated? —
Treatment depends on different factors, including:
●Whether your AVM is bleeding or not
●How big your AVM is, and where it is in your brain
●Whether you have symptoms from your AVM
If your AVM is not bleeding or causing symptoms, your doctor will talk with you about whether it needs to be treated. Not all AVMs need to be treated, especially if they are not bleeding or causing symptoms.
There are benefits and downsides to treating AVMs that are not bleeding or causing symptoms. The main benefit is that treatment can prevent a future bleed in the brain. The main downside is that the treatments can cause their own problems. For example, surgery can cause a seizure, stroke, or brain swelling or bleeding.
If your AVM is causing seizures, your doctor will give you anti-seizure medicines. These can help prevent more seizures.
AVMs that cause bleeding usually need treatment. The different treatments for an AVM include:
●Surgery to remove the AVM
●Radiosurgery – This is not surgery. It involves getting radiation (high doses of X-rays) in the area of the AVM. Over time, the radiation makes the AVM less likely to bleed. This treatment usually takes a few years to work.
●Embolization – This is a procedure done during cerebral angiography. The doctor puts a material into the blood vessel that brings blood to the AVM. The material blocks off the blood vessel. Sometimes, this procedure only blocks off part of the blood vessel and then doctors do surgery or radiosurgery to treat the rest.
What if I want to get pregnant? —
Talk with your doctor. They might recommend treating your AVM before you try to get pregnant.
When should I call the doctor? —
Call for an ambulance (in the US and Canada, call 9-1-1) right away if you have symptoms of a stroke, such as:
●Drooping of 1 side of the face
●Weakness or numbness in 1 or both arms
●Trouble speaking
●A sudden, severe headache
You should also call your doctor or nurse right away if you have a seizure or pass out.
Patient education: Intracerebral hemorrhage (The Basics)
Patient education: Stroke (The Basics)
Patient education: Seizures (The Basics)
Patient education: Headaches in adults (The Basics)
Patient education: Headaches in children (The Basics)
Patient education: Hemorrhagic stroke treatment (Beyond the Basics)
Patient education: Stroke symptoms and diagnosis (Beyond the Basics)
Patient education: Seizures in adults (Beyond the Basics)
Patient education: Seizures in children (Beyond the Basics)
Patient education: Headache causes and diagnosis in adults (Beyond the Basics)
Patient education: Headache in children (Beyond the Basics)
