Arteriovenous Malformations

An arteriovenous malformation (AVM) of the brain is a rare, abnormal bundle of blood vessels. Arteries, which carry oxygen-rich blood to the brain, and veins, which ferry blood back to the heart after oxygen delivery, are typically connected by capillaries. When an AVM is present, the capillaries are missing, so blood flows directly from arteries to veins while bypassing areas of the brain. The blood vessels in an AVM are weak and at risk of enlarging over time. If that happens, they may burst, bleeding into the brain and depriving it of oxygen and nutrients. An AVM bleed is a potentially deadly medical emergency requiring immediate care.


The most common type of brain AVM is called a true AVM. This defect features abnormal connections between arteries and veins with no normal brain tissue in between. Other types include:

  • Dural fistula. This is an abnormal connection between blood vessels in the dura mater, the structure overlaying the brain. Dura fistulas can occur behind the eyes or ears or on top of the head.
  • Hemangioma. This is an abnormal tangle of blood vessels on the brain’s surface. Hemangiomas may also be found on the skin, particularly on the face.
  • Occult AVM. Also known as a cryptic AVM or cavernous malformation, this type of AVM deprives the brain of less blood than a true AVM. Frequent seizures may occur with an occult AVM.
  • Venous malformation. This is a group of defective veins with no arteries involved.


Many AVMs don’t cause symptoms and are diagnosed as part of diagnostic testing or treatment for other conditions. An AVM that has ruptured may cause:

  • An intense headache
  • Buzzing or ringing in the ears
  • Confusion
  • Difficulty speaking
  • Memory problems
  • Problems with balance or difficulty walking
  • Seizures

Some AVMs may cause symptoms that are the result of pressure on the brain, such as:

  • Dizziness
  • Numbness in certain parts of the body
  • Vision abnormalities
  • Weakness in certain parts of the face or body


This condition is typically present at birth and cannot be prevented.

Risk Factors

Experts don’t know why AVMs develop, but they are more common in males and, rarely, run in families.


  • Medical history and physical exam. If your cardiologist suspects an AVM, he or she will ask about your health history and any symptoms you may have experienced. Your cardiologist will also perform a physical exam.
  • Imaging exams. A CT scan or an MRI may show an AVM.
  • Cerebral angiogram. This test uses contrast dye sent through a catheter into an artery in the neck to allow your cardiologist to gauge blood flow in the brain using X-ray images. A cerebral angiogram can help your cardiologist find an AVM and determine what kind it is.


A ruptured AVM requires emergency treatment to manage the bleeding and seizures. Surgical options include:

  • Endovascular embolization, a catheter-based procedure in which a physician injects a substance into the AVM to cut off blood flow
  • Open surgery to remove the AVM
  • Stereotactic radiosurgery, a treatment in which high-energy radiation shrinks or destroys the defect

If the AVM has not ruptured, there are various treatment options that depend on a variety of factors, including whether symptoms are present, the AVM’s size, location and risk of rupture, and your overall health. Some patients may be candidates for open surgery, endovascular embolization or stereotactic radiosurgery. For other patients, especially those who do not have symptoms or who have an AVM in a difficult-to-reach part of the brain, lifestyle and medication changes may be best. These include taking medications to manage certain symptoms, such as seizures, not exercising too much and refraining from taking blood thinners.

Follow-up Care

  • If you underwent open surgery or endovascular embolization, you may need to stay in the hospital for a few days, depending on your overall health and whether the AVM bled prior to surgery. If you had stereotactic radiosurgery, you’ll likely be able to go home the same day.
  • Be sure to follow your cardiologist’s instructions for recovering at home, including activity restrictions.
  • Moving forward, whether you underwent surgery or are following a conservative treatment plan for your AVM, be sure to follow up regularly with your cardiologist for ongoing care and monitoring. If you experience any new or recurring symptoms, tell your cardiologist.