Arteriovenous Malformation

Arteriovenous malformations (AVMs) are tangles of blood vessels that cause abnormal artery-to-vein connections. Most occur in your brain and spinal cord, but they can happen anywhere in your body. Some people have symptoms; others only have symptoms after an event like a brain bleed. Surgery to remove the AVM is a cure. Other treatments can be highly successful, as well.


Arteriovenous Malformation (AVM)

What is an arteriovenous malformation (AVM)?

An arteriovenous malformation (AVM) is an abnormal tangle (like a bird’s nest) of blood vessels. The tangle is made of arteries that would normally supply brain tissue and veins that would normally drain brain tissue.


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How exactly do arteries and veins normally connect and what happens when they don’t properly connect?

Blood moves through your body within an organized closed circuit of blood vessels. Your arteries carry oxygen-rich blood from your heart to your brain and to the rest of your body’s organs and tissues. Your veins return oxygen- and nutrient-depleted blood and waste products from tissues back to your heart and lungs. The exchange takes place in your capillaries, where the smallest blood vessel units of arteries and veins connect with each other. This is how normal blood circulation works

If you have an AVM, this “bridge” of capillaries between your arteries and veins is missing. The malformation can begin anywhere along the vascular tree, from the arterial (arteries) side to the arterial-capillary and the venous (veins) side.

The force of the blood flow from your arteries brings a lot of pressure to the AVM. Veins have weak walls and can’t always adjust to the pressure of blood flow. If your veins can’t handle the blood pressure, it might burst and bleed, which can cause significant health problems.

What is a brain arteriovenous malformation (AVM)?


Brain AVMs are AVMs that develop anywhere within your brain tissue or on the surface of your brain. AVMs most commonly occur in your brain, brainstem and spinal cord.

Do arteriovenous malformations (AVMs) occur in other areas of the body?

We have about 100,000 miles of blood vessels in our bodies. So, it’s possible for arteriovenous malformations (AVMs) to form anywhere in your body — on your face, arms or legs, and in your tissues and organs like your heart, liver, lungs, genital or reproductive tract. These AVMs are called peripheral arteriovenous malformations.


How common are arteriovenous malformations (AVMs)?

Arteriovenous malformations are rare. They’re present in about 1 in 100,000 people.

Who gets an arteriovenous malformation (AVM)?

Anyone can be born with an AVM. They’re mainly discovered in younger people from age 20 to 40. Risk of symptoms is highest between ages 40 and 50. AVMs happen in an equal number of males and females.

How do arteriovenous malformations (AVMs) cause harm?

AVMs cause harm in the following ways:

  • Bleeding. Bleeding into surrounding tissue can cause permanent damage. If significant bleeding occurs, it can result in death.
  • Pressing on and displacing anatomical parts. An abnormal connection results in more blood in your veins. Veins can get big and press on nearby tissue. This not only prevents oxygenation, but it will also impact draining through your lymphatic system.
  • Depleting tissues of needed oxygen. Because there’s no capillary bridge between arteries and veins, oxygen and nutrients don’t get to the tissue where there’s an AVM. The tissue and nerve cells at that site can die.

Are arteriovenous malformations dangerous?

They can be. The greatest danger is bleeding (hemorrhage). If you feel a sudden, severe headache (“worst in your life”), call 911. You might have a bleeding brain AVM. About 2.2% of unruptured brain AVMs and 17% of previously ruptured AVMs burst (rupture) every year.

Symptoms and Causes

What causes an arteriovenous malformation (AVM)?

Scientists aren’t sure what causes arteriovenous malformations. They believe they develop during pregnancy, so you’re born with an AVM (they’re congenital). Some cases have been reported in people with head trauma or certain infections. Only in rare cases are AVMs thought to be hereditary (run in families).

What are the symptoms of arteriovenous malformations?

You may or may not have symptoms if you have an arteriovenous malformation. Up to 15% of people with AVMs don’t have symptoms. Often, the first sign you have an AVM is after it bleeds.

Brain AVM: If you have a brain AVM and it leads to a blood vessel bleed (rupture), it can cause a stroke and brain damage. About 50% of people with a brain AVM have a brain bleed (hemorrhage) as their initial symptom.

AVMs can irritate the surrounding tissue, causing neurologic symptoms, including:

  • Seizures with or without loss of consciousness.
  • Headache. (The nature of pain, duration, frequency and severity vary from person to person.)
  • Muscle weakness or complete paralysis.
  • Nausea and vomiting.
  • Numbness or tingling sensation.
  • Dizziness.
  • Problems with movement, speech, memory, thinking, balance or vision.
  • Mental confusion, hallucinations or dementia.

Spinal cord AVM: If you have a spinal cord AVM, symptoms include:

  • Back pain (can be sudden and severe) or weakness in your lower body (hips) and legs to your toes.
  • Muscle weakness or paralysis in your body areas of the affected nerves.

AVMs in other locations: If you have AVMs in other locations in your body (other than your brain and spine), you may or may not have symptoms depending on their size and the significance of the location. General symptoms may include:

  • Shortness of breath during exertion.
  • Coughing up blood (if the AVM is in your lungs).
  • Abdominal pain.
  • Black stools/poop (if the AVM is in your digestive tract).
  • Lumps on arms or legs or on your trunk.
  • Pain and swelling.
  • Muscle weakness or paralysis.
  • Numbing or tingling sensation.
  • Sores or open ulcers on your skin.

Diagnosis and Tests

How are arteriovenous malformations (AVMs) diagnosed?

Your healthcare provider will ask you about your symptoms and conduct a physical exam. They’ll sometimes listen for a bruit, which is a rapid blood flow sound heard in arteries and veins when an AVM is present.

Imaging tests used to detect arteriovenous malformations include:

  • Magnetic resonance imaging (MRI).
  • Computed tomography.
  • Catheter angiography. A tube, called a catheter is inserted into an artery in your groin and moved to the area to be investigated. Dyes and X-rays are used to view details of your blood vessels.
  • Ultrasound. Uses sound waves to produce pictures.

Brain imaging tests for suspected brain AVMs may include:

  • Cerebral magnetic resonance angiography (MRA). Uses magnetic field and radio waves to produce detailed pictures of your blood vessels in and around your brain.
  • Computed tomography angiography (CTA). Uses X-rays to see detailed pictures of your blood vessels.
  • Transcranial Doppler ultrasound. Uses sound waves to determine the speed of blood flow through your brain.

Because many AVMs don’t cause symptoms, some are only discovered during an imaging test for another condition (such as injuries, vision problems or headaches) or after they bleed and cause symptoms.

What are the complications of arteriovenous malformations (AVMs)?

Complications of brain AVMs include:

  • Brain bleed/stroke.
  • Seizures.
  • Aneurysm. This is a balloon-like bulge in the walls of any of the blood vessels feeding into or around the AVM (arteries, veins the AVM itself). They develop because of a structural weakness in your blood vessel walls. Aneurysms develop in about 50% of all brain and spinal cord AVMs.
  • Brain damage that affects thinking, mental processing, memory or understanding speech.
  • Coma and death, especially from a large bleed in your brain.

Management and Treatment

What are the treatments for arteriovenous malformations (AVMs)?

Treatment choices depend on the type, size and location of the AVM, risk of AVM rupture, your symptoms, your age and your general health. Ideally, the goal of treatment is to reduce the chance of bleeding or make it permanently go away. Surgery on your brain and spinal cord is serious, with risks including complications and death. Each person, and each person’s AVM, is unique and there aren’t any perfect decision-making tools in all cases. In general, though, treating an arteriovenous malformation as soon as possible is usually the best way to avoid serious complications.

One or more of these approaches might be tried:

  • Surgery to remove the AVM. Surgery involves making a small incision near the AVM, sealing the surrounding arteries and veins so they don’t bleed, then surgically removing the AVM. Blood flow is redirected to normal blood vessels. Surgery is a cure of this condition.
  • Embolization. In this procedure, a catheter is inserted into an artery in your groin and moved to the location of the AVM. Once there, a glue-like substance, coils or other substance is released into the AVM, which slows or stops the blood flow through the AVM. This approach is used when the AVMs are large and have a lot of blood flow through them. This way, they can be more easily removed with less risk of bleeding if surgery is performed immediately afterward. Embolization can also slow blood flow to reduce rupture if surgery isn’t immediately performed.
  • Gamma knife radiosurgery. This approach uses highly focused beams of radiation that slowly shrink, scar and dissolve an AVM over a few years or make the AVM easier to remove with surgery.

What happens if these standard treatment approaches can’t be tried?

AVMs can be complicated. There may be times when the AVM might be located in an area where the dangers of surgery or other treatments are of greater concern and pose a greater risk than doing nothing at all. If this is the case, your healthcare team may choose to carefully monitor your AVM with imaging tests over time. If the AVM begins showing signs of change, indicating an increased risk of bleeding, treatment may be considered at that time. Each person and each arteriovenous malformation is unique. Your healthcare team will talk to you and your family about your particular situation and the best way to approach your AVM.

What happens after brain surgery for an arteriovenous malformation (AVM)?

You’ll have a brain scan to make sure the AVM has been completely removed or destroyed. You’ll also have a short hospital stay (a few days) and undergo some short-term rehabilitation.

If you have the gamma knife treatment, you’ll have scans from time to time to see if the AVM is shrinking.

What medications are used to help treat arteriovenous malformations?

Medications can be given to relieve some of the symptoms of AVMs. These include:

  • Anti-seizure medications.
  • Pain relievers for headache and back pain.

What are the risks of arteriovenous malformations (AVMs)?

The biggest risk of having an AVM is that it might bleed. If the AVM is in your brain, a brain bleed causes a stroke, brain damage or seizures. Because these areas are enclosed, AVMs can also press on and displace parts of your brain and spinal cord.

AVMs reduce the amount of oxygen in the areas in which they exist. A reduced oxygen level damages tissue.


Can arteriovenous malformations (AVMs) be prevented?

No, AVMs can’t be prevented because researchers believe they’re congenital, meaning you’re born with them. But if you develop any of the symptoms listed in this article, see your healthcare provider right away. Responding quickly to developing symptoms is the best approach.

Outlook / Prognosis

What outcome can I expect if I have an arteriovenous malformation (AVM)?

Each person’s AVM is a unique situation. If you’ve had surgery and your AVM has been successfully removed, you’re cured of this condition.

The outcome of other AVM treatments is very good, but there are many variables, including:

  • Location.
  • Size.
  • Type of AVM.
  • Your age and general health.

Your healthcare team can best discuss your AVM and the likely expected outcome.

If you have an arteriovenous malformation and don’t get treatment, there’s a 2.2% chance it will burst.

Living With

When should I seek emergency care?

If you experience a sudden, severe headache (“worst in my life”), seizures, weakness in your arms or legs, vision problems, balance problems or memory and attention problems, call 911. These are signs of a life-threatening emergency. This could be a brain bleed.

Do all arteriovenous malformations (AVMs) eventually bleed?

No. Some arteriovenous malformations never cause a bleed and may not even cause symptoms or any health problems your entire life. Some are only discovered during an imaging test for another reason or after death during an autopsy.

AVMs can cause other health issues other than bleeds. Some AVMs that grow and become large can press on an area of tissue and cause tissue damage, nerve cell damage and other cell damage in that area. If large enough and in a vital area, the lack of the capillaries between your arteries and veins can cause a lack of oxygen, nutrients and waste exchange in tissue in this area. This can lead to tissue death.

Can arteriovenous malformations (AVMs) be fatal?

Yes, unfortunately, they can be. How deadly or severe an arteriovenous malformation might be depends on its size and location. A massive bleed from a ruptured AVM in your brain can be fatal. However, some people have AVMs and never have any symptoms or health problems.

Does the location of pain in my head indicate the location of an arteriovenous malformation (AVM)?

Not necessarily. It may, but most often, the location you feel headache pain isn’t specific to the area of the AVM.

Does a pregnant person with arteriovenous malformations (AVMs) have an increased risk?

Because of the increase in blood volume and blood pressure that comes with pregnancy, being pregnant with an AVM can increase the risk of an AVM bleed. In some people, the changes brought on by pregnancy can cause the sudden appearance or worsening of AVM symptoms.

How do arteriovenous malformations (AVMs) affect children?

AVMs can cause small changes in your child’s ability to learn, or cause behavioral changes. These changes might happen before more obvious symptoms develop when your child is older (if symptoms develop).

Do brain bleeds from arteriovenous malformations (AVMs) always can significant brain damage?

No. Some very small brain bleeds, called microbleeds, cause limited damage and few symptoms. But over time, many microbleeds can increase the risk of dementia and impair thinking functions.

What’s the difference between an arteriovenous malformation, aneurysm, hemangioma, cavernous malformation and fistula?

An aneurysm is a weakened, ballooned-out area in an artery. It most commonly forms at the point where two arteries branch. An aneurysm can develop as a complication of an AVM.

Hemangiomas are vascular (blood vessel) malformations that are visible on the skin. They’re also known as a strawberry mark. They aren’t dangerous and don’t require treatment.

Cavernous malformations are a type of vascular lesion. Unlike an AVM, they’re filled with slow-moving blood that’s usually clotted. They can leak but usually don’t leak as severely as AVMs and are often don’t cause symptoms.

A fistula is a general term for an abnormal connection of blood vessels. Arteriovenous fistulas are found in the tissue that covers your brain and spinal cord (the dura mater or arachnoid). AVMs are found inside the tissues of your brain.

A note from Cleveland Clinic

An arteriovenous malformation (AVM) is a serious medical condition. Some people have no symptoms of an AVM until they have a bleeding event. AVMs are mostly found in your brain and spinal cord, but can be present anywhere in your body. The decision to treat an AVM depends on many factors, including consideration of the risk that an AVM may bleed and result in significant or even life-threatening damage if left untreated (especially if located in your brain). Available treatments are highly effective. Your healthcare team will discuss with you the details of your AVM — its size and location — and other factors to develop treatment options that are best for you.

Medically Reviewed

Last reviewed by a Cleveland Clinic medical professional on 02/27/2022.

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