An Arterio-Venous Malformation, or AVM, is a defect in the circulatory system that likely occurs during prenatal development or soon after birth. In normal circumstances, body tissue is nourished by oxygenated blood in the capillaries. An AVM is an area that is missing capillaries, which means oxygenated blood is simply rerouted back to the heart without supplying nutrients to tissue.

AVMs can develop throughout the body, and often do not cause any significant symptoms. However, those that manifest in the brain or spinal cord can be especially problematic. About 36,000 of the estimated 300,000 Americans with AVMs do experience symptoms, some rather severe. While seizures and headaches are the most common effects, specific symptoms and their intensity vary greatly and depend primarily on the AVM’s location in the body. Symptoms may include:

  • muscle weakness or paralysis
  • loss of coordination
  • difficulties carrying out tasks that require planning
  • dizziness
  • visual disturbances
  • problems using or understanding language
  • abnormal sensations (such as numbness, tingling, or spontaneous pain)
  • memory deficits, mental confusion, hallucinations, or dementia


General symptoms, such as headaches and seizures, can often be treated with medication, but the definitive way to address an AVM is through surgery or focused irradiation therapy. Because there are many variables to consider, doctors carefully weigh the possible benefits against the risks for each individual case before deciding on surgery.


Research shows that between 2 and 4 percent of AVMs hemorrhage each year. While most are not even detected because they are not severe enough to cause significant neurological damage, some bleeding episodes are massive and can be fatal. It is therefore imperative that individuals diagnosed with an AVM are constantly monitored for signs of instability that may point to an increased risk for hemorrhage.