What are Arteriovenous Malformations (AVM)?
Arteriovenous malformations, or AVMs, are irregular connections between arteries and veins. They can occur anywhere in the body but are most common in the brain and spinal cord. The greatest risk of an AVM is that it will rupture and cause a stroke.
Your arteries carry blood from your heart to the rest of your body. As the arteries move farther away from the heart, they branch off and get smaller. Very small arteries turn into capillaries that carry blood to your cells and tissues. As the capillaries leave the tissue, they empty into larger veins that carry blood back to the heart. An AVM is a tangle of blood vessels that bypasses the capillaries and connects the arteries directly to the veins.
At Penn Medicine, we have extensive experience managing cerebrovascular diseases like arteriovenous malformations. Our collaborative approach ensures you receive appropriate monitoring and timely treatments to lower your stroke risk caused by an AVM.
The Impact of Arteriovenous Malformations
An AVM can damage brain or spinal cord tissues through:
- Bleeding (hemorrhage): Because of the direct connection with arteries, blood pressure inside the veins of the AVM is higher than normal. This extra force can cause the wall of the vein to bulge (aneurysm) and, eventually, rupture and bleed. In the brain, this can cause a dangerous hemorrhagic stroke.
- Compression of the brain and spinal cord structures: AVMs can grow to over 2.5 inches. A large AVM pressing on the brain or spinal cord can cause a range of neurological symptoms. This pressure can also disrupt the flow of cerebrospinal fluid (CSF), a clear liquid that surrounds the brain and spinal cord. A buildup of CSF can lead to hydrocephalus or intracranial hypertension.
- Reduced blood flow: AVMs divert blood flow from brain and spinal cord tissues, leaving them deprived of oxygen and nutrients. As a result, the tissue may deteriorate or die, impairing normal function.
Arteriovenous malformations are rare. Doctors diagnose about 3000 new cases of AVM each year in the U.S.
What Causes Arteriovenous Malformations?
It is unclear what causes AVMs. Most doctors believe they develop during pregnancy and people are born with it (congenital). But AVMs rarely run in families, so it's unlikely you will pass the condition to your child.
Symptoms of Arteriovenous Malformations
Arteriovenous malformation symptoms vary based on their location and size. Some people do not have any symptoms, especially at a young age. People are usually in their mid-30s when symptoms first appear.
Symptoms may also appear or become worse during pregnancy. This occurs due to pregnancy-related increases in blood volume and blood pressure.
For many people with a brain AVM, a hemorrhage is their first sign. If the bleeding is severe, it can cause a stroke which is a life-threatening emergency. The main symptoms of a stroke include:
- Headache that is sudden and severe
- Nausea and vomiting
- Seizures
- Sensitivity to light or double vision
- Stiffness of the neck
- Loss of consciousness
If you experience these symptoms, call 911 immediately. Do not drive yourself to the hospital.
Other general arteriovenous malformation symptoms include:
- Confusion, hallucinations or dementia
- Headache
- Problems with memory, vision or speech
- Seizures
- Weakness or paralysis on one side of the body
Symptoms of AVMs in the spinal cord include:
- Muscle weakness, numbness or paralysis (the location depends on the affected nerves)
- Severe and sudden back pain
Vein of Galen Malformation
A vein of Galen malformation is an AVM in the vein of Galen, which lies deep in the brain. Symptoms occur at or shortly after birth. In some infants, the malformation leads to a rapid flow of blood to the heart that causes heart failure within the first few days of life.
Other symptoms in infants and children with vein of Galen malformations include:
- Developmental delays
- Headaches
- Hydrocephalus
- Prominent veins on the scalp and face
- Seizures
- Stroke
Many children with vein of Galen malformations do not survive past infancy. Children who receive treatment may have a good prognosis. Others may have long-term developmental problems.
Diagnosing Arteriovenous Malformations
To perform an AVM diagnosis, your doctor will ask about your symptoms and medical history and perform a physical exam. Some AVMs cause turbulent blood flow inside your blood vessels that causes a noise called a bruit. Your doctor may hear this noise through a stethoscope during the physical exam.
AVM diagnosis tests your provider may order to look at the blood vessels in your spine, neck and head include:
- CT and CT angiography (CTA): A CT scan combines X-rays taken from multiple angles to create a 3D image. A CTA is a CT scan of your blood vessels.
- MRI and MRI angiography (MRA): MRI uses radio waves and a magnetic field to take detailed pictures of your body. A MRA is a type of MRI that shows the details of your blood vessels.
If you have a known or suspected AVM, your doctor will likely perform a cerebral angiogram. This test helps your doctor assess your condition and plan for treatment. A thin tube (catheter) is inserted into a blood vessel into your groin or wrist. Your doctor advances the catheter to the neck or head and releases a contrast dye. Imaging taken after the release of dye highlights any abnormalities. In some cases, endovascular AVM treatment can occur right away during the during the angiography.
Arteriovenous Malformation Treatment at Penn Medicine
Specialists in our Neurology and Cerebrovascular Disease programs are highly skilled in a range of techniques to manage and treat AVMs. This expertise allows us to develop a personalized treatment plan.
If the AVM has not ruptured, your doctor will help you weigh the risks of possible hemorrhage vs the risks of treatment. Factors that may increase your risk of bleeding include:
- Pregnancy
- Size and location of the AVM
- Symptoms you are experiencing
- Your age and overall health
Your doctor my prescribe medications to help reduce symptoms, such as seizures and headaches. Surgical treatments for AVMs include:
- Endovascular embolization: This is a minimally invasive procedure. Your doctor inserts a catheter into a blood vessel and guides it to the AVM. Your doctor injects glue or another material to plug the AVM. Typically, this procedure occurs before AVM removal through microsurgery. By reducing blood flow, embolization can reduce the risk of complications during surgery.
- Microsurgery: Microsurgery involves removing a portion of the skull and using a surgical microscope and specialized tools remove the AVM. This treatment is most appropriate for AVMs located in the spinal cord and outer areas of the brain.
- Radiosurgery: This technique uses beams of radiation instead of open surgery to treat small, unruptured AVMs. At Penn, our experts use type of radiosurgery called Gamma Knife®. This state-of-the-art technology pinpoints the AVM and delivers bursts of energy to damage the blood vessels. Over a few months, the blood vessels deteriorate and close.
Doctors assess surgical risk using the Spetzler-Martin grading scale to determine the safest treatment. This scale estimates the risk of complications during microsurgery based on AVM size and the area of the brain involved. If your surgical risk is high, endovascular embolization and radiosurgery may be effective alternatives to microsurgery.
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