An arteriovenous malformation (AVM) is a condition where a group of tangled, abnormal blood vessels affect how blood flows between your arteries and veins. AVMs are most commonly found in the brain and spinal cord, but can also occur in other parts of the body.
Normally, arteries carry oxygen-rich blood from the heart to the body's tissues, and veins return the blood back to the heart and lungs. Tiny blood vessels called capillaries help with this process by slowing blood flow and allowing oxygen to reach nearby tissues. But in an AVM, the capillaries are missing, so blood moves too quickly from arteries to veins without delivering oxygen where it's needed. This can lead to tissue damage and, over time, may cause the AVM to grow larger.
Many people with an AVM in the brain or spinal cord don’t have noticeable symptoms. However, in some cases, the abnormal blood vessels can weaken and rupture, causing bleeding in the brain (a hemorrhage), which can lead to a stroke or other serious complications. AVMs are often found by chance during tests for other health conditions.
AVM symptoms can develop at any age, but they are most often noticed in a person’s 20s or later. Because AVMs cause gradual damage over time, symptoms tend to appear as people get older. If no symptoms have developed by the late 40s or early 50s, the AVM is usually stable and less likely to cause problems. In some cases, pregnancy can trigger new or worsening symptoms due to increased blood volume and blood pressure.
The first signs of an arteriovenous malformation often show up after bleeding occurs. Along with bleeding, symptoms may include:
Other symptoms that may happen include:
If you experience any severe symptoms or if they come on suddenly, don't wait—call 911 or go to the emergency room right away. Symptoms like an intense headache, suddenly passing out or losing the ability to move can be signs of a serious problem, like bleeding in the brain, which could be caused by an AVM or other conditions.
Even if you do not have these symptoms, it's a good idea to talk to your healthcare provider if you have risk factors for AVMs or if there's a history of neurological conditions in your family. Catching an AVM early and staying on top of your health can help prevent complications and guide the right treatment.
The exact cause of AVMs is not fully understood. Most of the time, AVMs are congenital, meaning a person is born with them, but they can also develop shortly after birth or later in life. While AVMs can sometimes run in families, it's more common for other inherited conditions to increase the risk of developing an AVM.
