Dr. Tigran Khachatryan, MD, PhD.

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Arteriovenous Malformations

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Understanding Arteriovenous Malformations (AVMs): A Patient Guide

What is an AVM?

An arteriovenous malformation (AVM) is an abnormal tangle of blood vessels that can happen anywhere in your body, though they are most common in the brain or spinal cord. To understand an AVM, it helps to know how blood usually flows: normally, your heart pumps blood through arteries (which carry oxygen) into tiny vessels called capillaries. These capillaries slow down the blood so your tissues can soak up oxygen before the blood travels back to the heart through veins. In an AVM, the arteries connect directly to the veins without those tiny capillaries in between. This creates a “high-pressure shunt” where blood rushes through far too quickly.

Why is this a problem?

Because the blood is moving so fast and under such high pressure, two main problems occur:
Oxygen Loss: The surrounding brain or spinal tissue doesn’t get the oxygen it needs because the blood “steals” it away before the tissue can absorb it.
Weakened Vessels: Veins are not built to handle the high pressure of arterial blood. Over time, this pressure causes the veins to stretch, weaken, and potentially burst or leak, which is called a hemorrhage.

Common Symptoms
Many people with an AVM have no symptoms at all and only find out they have one after a scan for a different health issue. However, when symptoms do occur, they can include:
Brain AVMs: Sudden, severe “worst headache of my life,” seizures, muscle weakness or numbness, vision problems, and trouble speaking or understanding others. Some people hear a “bruit,” which is a swishing or ringing sound in the ear caused by blood pulsing through the tangle.
Spinal AVMs: Sudden and serious back pain, weakness in the legs or arms, numbness, and difficulty with walking or bowel and bladder control.

What causes them?

The exact cause of AVMs is not fully known. Most experts believe they form while a baby is still growing in the womb. While you are usually born with them, they are generally not passed down through families, though there are rare exceptions.
How is it diagnosed?

If a doctor suspects an AVM, they will use imaging tests to see the blood vessels clearly:
CT Scan: A fast X-ray that can show if there is any bleeding in the brain.
MRI/MRA: Uses magnets to create a detailed picture of your brain or spine and the blood flow within them.
Angiogram: This is the most detailed test. A tiny tube (catheter) is threaded through a blood vessel in your leg up to the area being studied, where a special dye is injected to make the AVM show up clearly on X-rays.

Treatment Options

Your medical team will recommend a plan based on the AVM’s size, its location, and your risk of bleeding.
Observation: If the risk is low, your doctor may simply monitor you and provide medications to manage blood pressure or prevent seizures.
Endovascular Embolization: A doctor guides a tiny tube to the AVM and injects a “glue” or coils to block off the blood flow and shrink the tangle.
Stereotactic Radiosurgery (Gamma Knife): Highly focused radiation beams are aimed at the AVM to cause the vessels to scar and close over a period of 1 to 3 years.
Open Surgery: A surgeon removes a small piece of the skull (craniotomy) to physically take out the AVM. This offers an immediate cure if the entire tangle can be safely removed.

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Possible Complications

The most serious complication is a hemorrhage (bleeding), which can lead to a stroke or permanent brain and nerve damage. Large AVMs can also press against the brain or spine, causing seizures or a buildup of fluid in the head (hydrocephalus). Additionally, the high pressure can cause a bulge in a vessel wall, known as an aneurysm, which is also at risk of bursting.

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Summary

An arteriovenous malformation (AVM) is a rare, usually birth-related tangle of blood vessels that disrupts the normal flow of oxygen to the brain or spinal cord. By bypassing the body’s natural filtering system of tiny capillaries, these high-pressure connections can weaken veins over time, leading to symptoms like seizures, severe headaches, or even life-threatening bleeding. While the cause is often unknown, modern medicine offers several ways to manage or remove AVMs—including specialized surgery, radiation, or “gluing” the vessels shut—to prevent complications like stroke or permanent nerve damage.