An arteriovenous malformation (AVM) is a tangle of blood vessels. It can develop anywhere in the body, but it presents the most risk when it occurs in the brain or spinal cord. An AVM can result in damage to nearby tissues and bleeding.

While bleeding is the first manifestation of an AVM in 50% of people, many people have no symptoms. Often, people learn they have an AVM during tests for other conditions.

The goal of treatment for AVMs is to prevent bleeding. If treatment is necessary, doctors may recommend surgery, radiosurgery, or both to destroy it.

This article examines the symptoms, causes, diagnosis, treatment, and complications of an arteriovenous malformation. It also discusses when to get help and suggests sources of support.

A cut-out photo of the lower half of a person's face with tangled rope above it to represent an ateriovenous malformation.Share on Pinterest

An AVM is a tangle of blood vessels that creates abnormal blood flow between arteries and veins. While AVMs most frequently occur in the brain or spinal cord, they can affect any part of the body.

Arteries carry oxygen-rich blood to body tissues, and veins return low oxygen blood to the heart. Usually, tiny blood vessels known as capillaries connect the arteries to the veins. But in an AVM, blood from the arteries flows directly into veins without passing through capillaries.

This “shortcut” means capillaries cannot deliver blood to nearby cells and tissues. This can reduce their supply of oxygen, which may result in cells becoming damaged or dying.

The increased amount of blood circulating in the AVM can also result in high blood pressure and weakness in the vessel walls. This can lead to:

  • an aneurysm, which is a bulge in the wall of a blood vessel that may burst
  • microbleeding, which is a small amount of bleeding that can result in dementia over time
  • massive bleeding, which can cause a stroke

Brain AVMs are uncommon, affecting less than 1% of the general population. They occur more frequently in males.

Bleeding is the first symptom of an AVM in approximately 50% of people with the condition. However, many people have no symptoms.

About 12% of people with an AVM have symptoms of varying severity that may include:

  • headaches
  • new onset seizures
  • dizziness
  • muscle weakness or paralysis
  • visual disturbances
  • loss of coordination
  • language problems
  • difficulty in performing organizational tasks
  • abnormal sensations, such as:
    • tingling
    • numbness
    • spontaneous pain
  • dementia
  • confusion
  • hallucinations
  • memory problems

Scientists do not fully understand the causes of AVMs. It is possible AVMs sometimes develop during embryonic or fetal development.

Both before and after birth, the body produces angiogenic factors, which are chemicals that stimulate the formation of new blood vessels. Researchers have found changes in the chemical structure of angiogenic factors in some people with AVMs. However, it is unclear how these changes result in negative effects on blood vessel structure.

There is also evidence to suggest that injuries to the brain or spinal cord can cause AVMs. Rarely, certain inherited conditions can lead to AVMs. Examples of these include hemorrhagic telangiectasia and Wyburn-Mason syndrome.

Doctors can sometimes diagnose an AVM by listening for a bruit. A bruit is a whooshing, rhythmic sound that stems from the rapid flow of blood through an AVM.

Doctors also use imaging tests to make a diagnosis. Cerebral angiography, or cerebral arteriography, offers the most accurate pictures of blood vessel structure in AVMs. Sometimes, a doctor may need to use other tests, such as a:

  • CT scan, which shows the presence of bleeding in the brain
  • MRI scan, which reveals subtle changes in brain tissue
  • transcranial Doppler ultrasound, which detects the presence of bleeding and can diagnose medium to large AVMs
  • magnetic resonance angiography, which measures the velocity and pattern of blood flow through AVMs, along with the flow of cerebrospinal fluid through the brain and spinal cord

Treatment for an AVM depends on its location and how much at risk a person is from bleeding or other complications.

Treatment for AVMs in the brain usually focuses on preventing bleeding and rupture. Occasionally, intervention goals also include controlling seizures and stabilizing progressive neurological deficits that the AVM has caused.

Medications can reduce symptoms, such as seizures or headaches. However, to stop the AVM causing further problems, doctors have to destroy it or stop blood from circulating around it. Doctors may do this via the following methods:

  • Conventional surgery removes the central part of the AVM while causing as little harm as possible to surrounding tissues. Doctors may consider this if the AVM is relatively small and is close to the surface rather than in a deep region.
  • Endovascular embolism involves a doctor creating an artificial blood clot in the center of an AVM to stop blood from flowing around it. It does not destroy the AVM, so doctors may use it with surgery or radiosurgery to decrease blood flow through the AVM.
  • Radiosurgery is an approach for treating small, unruptured AVMs. A doctor focuses a beam of radiation directly on the AVM, which damages the walls of the blood vessels making up the lesion. Over the following months, the blood vessels that received the radiation gradually deteriorate and close.

If the AVM is in a location that is hard to reach or target with treatments, doctors may suggest conservative management using only medications.

One of the most serious complications of an AVM is bleeding. According to the American Stroke Association, a person with an AVM in the brain has around a 1–3% risk of bleeding per year.

If an AVM in the brain bleeds, the risk of permanent brain damage is 20–30%. The likelihood of death from each bleed ranges from 10–15%, notes the association.

Other complications include swelling or atrophy of the surrounding area.

A person should seek immediate medical attention if they or someone else suddenly experiences:

  • a severe headache
  • weakness in arms or legs
  • balance problems
  • attention and memory problems
  • seizure
  • vision problems

An AVM diagnosis can be worrying. For people who have symptoms, it can have a significant impact on their quality of life.

However, there are things people can do to take care of their mental and physical health, such as:

  • Avoiding strenuous exercise: People who are taking medications for their AVM may need to avoid strenuous exercise that could raise blood pressure. A doctor can advise on which exercises to avoid.
  • Avoiding certain medications: People with an AVM need to avoid medications that could increase the risk of bleeding, such blood thinners.
  • Learning about AVMs: Understanding AVMs and their effects can be empowering. It can help give a realistic sense of AVM risks. It can also help with explaining what an AVM is to others.
  • Seeking support: People may wish to talk with a counselor or therapist about their diagnosis. A support group, such as the AVM Survivors Network, may also help.

An arteriovenous malformation (AVM) is a tangle of blood vessels that causes blood to flow directly from arteries to veins, bypassing capillaries. This can lead to less oxygen getting to cells and tissues, high blood pressure, and bleeding.

Confirming a diagnosis may involve imaging scans, such as cerebral angiography. This imaging scan provides the most accurate view of AVM blood vessel structure.

Treatment may include medications to manage symptoms, but the most effective treatments are either surgery or focused radiation to prevent bleeding.