Arteriovenous Malformation (AVM)
What is an Arteriovenous Malformation?
An arteriovenous malformation (AVM) is an abnormal tangle of blood vessels. This defect, which can occur anywhere in the central nervous system, causes blood to flow directly from arteries to veins through an abnormal passageway called a fistula instead of through capillaries. Generally speaking, there are three ways an AVM can damage the brain or spinal cord:
- Arteries and veins in an AVM can rupture, causing bleeding in the brain or spinal cord (hemorrhage)
- The amount of oxygen delivered to adjacent brain and spinal tissues is reduced, causing them to deteriorate or malfunction, producing seizures or neurological deficits
- An AVM can compress or displace parts of the brain or spinal cord
Arteriovenous Malformation (AVM) Symptoms
Symptoms can vary depending on the severity and location of the arteriovenous malformation, or they may never appear at all.
Symptoms of a neurological AVM may include:
- Muscle weakness or paralysis
- Problems with balance and coordination (ataxia)
- Pain or unusual sensations throughout your body, such as tingling or numbness
- Visual disturbances such as loss of part of the visual field
- Inability to control eye movement
- Problems understanding language (aphasia)
- Memory deficits
- Mental confusion, hallucinations, or dementia
AVMs share symptoms with other conditions. Imaging tests by a medical professional are needed to diagnose an AVM.
Arteriovenous Malformation (AVM) Treatments
Treatment depends on the size, location, and symptoms of the arteriovenous malformation. Your doctor may recommend one or a combination of the following treatments:
- Surgery – The arteriovenous malformation is removed from the brain using microsurgical techniques that close the abnormal feeding arteries, separate the tangle from the adjacent brain, and cut the veins draining the AVM.
- Endovascular embolization – In this minimally invasive technique, a catheter is guided through the network of arteries until the tip reaches the site of the AVM. Various branches of the AVM are then plugged with a material such as glue or polymer cast. Embolization is usually used as a precursor to surgery to reduce the blood flow through the AVM.
- Radiosurgery – In this noninvasive procedure, focused beams of radiation are targeted at the AVM and, over the course of 2-3 years, the arteries respond by scarring and closing down. Radiosurgery can be curative or can shrink an AVM down to a size that is more favorable for surgery. Gamma Knife and Cyberknife radiosurgeries are offered at Barrow.
How common are arteriovenous malformations?
An estimated 300,000 Americans are affected by arteriovenous malformations of the brain and spinal cord (neurological AVMs), but only about 12 percent of the affected population will have symptoms.
Who gets arteriovenous malformations?
Arteriovenous malformations are equally common among men and women of all races and ethnicities. They are believed to be congenital (existing at birth), but they can enlarge over time and cause symptoms at any age.
Pregnancy can sometimes cause a sudden onset or worsening of symptoms because of cardiovascular changes, such as increases in blood volume and blood pressure.
How are arteriovenous malformations diagnosed?
Most arteriovenous malformations are detected through diagnostic imaging, such as a CT or MRI scan. Angiography, an imaging technique that involves the injection of a special dye, may be used to get a better look at the AVM.
Because most people with AVMs experience few symptoms, these abnormalities are often discovered during treatment for an unrelated disorder.
What is the survival rate for an arteriovenous malformation?
Some people with AVMs will never experience hemorrhage in their lifetime. Of those who do have bleeds, 90 percent survive. However, depending on the severity and location of the rupture, these individuals may have some degree of disability.
Can a cerebral arteriovenous malformation cause personality changes?
No, a dormant cerebral arteriovenous malformation usually does not cause personality changes. However, being diagnosed with an AVM and weighing the treatment options can be an emotional process. When an AVM bleeds, the injury to the brain may cause emotional and mood changes. These individuals may also struggle to cope with disabilities and other life changes.
What causes an arteriovenous malformation to rupture?
In AVMs, blood flows directly from arteries to veins without the buffer of capillaries. Arterial pressure is too high for veins to accommodate due to their thinner walls, which can weaken the blood vessels and cause rupture. Researchers are studying other possible factors in AVM rupture.
Can an arteriovenous malformation cause dementia?
No, the presence of an AVM does not cause dementia. However, a hemorrhagic stroke caused by an AVM can cause problems with memory.
Does an arteriovenous malformation show up on MRI?
Yes, magnetic resonance imaging is the most common way AVMs are detected. Since only about 12 percent of people with AVMs develop symptoms, AVMs are often discovered by accident when imaging is done for an unrelated concern.
Can an arteriovenous malformation go away on its own?
No, an AVM cannot go away on its own. However, it can be removed with surgery, sealed off with endovascular embolization, or reduced in size with radiosurgery.