What is an Arteriovenous Malformation?
Arteriovenous Malformation (AVM)
An arteriovenous malformation, or AVM, is a tangle of abnormal blood vessels that forms during development. Normally, arteries carry blood to the body’s tissues through tiny vessels called capillaries, and veins carry it back to the heart. In an AVM, arteries connect directly to veins without capillaries in between, so blood bypasses the surrounding tissue. AVMs can occur anywhere in the body, but they are most common in the brain and spinal cord (1).
An AVM can bleed. Call 911 right away for a sudden, severe headache, a seizure, sudden weakness or numbness, vision loss, trouble speaking, confusion or severe unsteadiness.
How Common Are AVMs?
About 1 in 100,000 people are newly diagnosed with an AVM each year, and about 10 in 100,000 people have one. AVMs don’t appear to be linked to any particular ethnic or racial group, and men and women are affected equally (2).
What Are the Symptoms of an AVM?
Many AVMs cause no symptoms and are found only when imaging is done for another reason. Others cause headaches, seizures or weakness in part of the body. More serious symptoms can include severe headache, weakness, numbness or paralysis, vision loss, trouble speaking, confusion and severe unsteadiness.
An AVM can also rupture and bleed into the brain (a hemorrhage), causing stroke-like symptoms such as vision changes, loss of feeling on one side of the body, headaches and weakness on one side of the body. Symptoms most often begin between ages 10 and 40 (1). During pregnancy, symptoms may get worse because blood volume and blood pressure increase.
What Causes an AVM?
AVMs are thought to result from an error in how blood vessels form before birth. No environmental risk factors have been identified for AVMs in the brain. They usually aren’t inherited, though about 5% appear to be linked to genetic changes (2).
What Happens in the Brain With an AVM?
The brain is made of many types of cells. The ones we usually think of as brain cells are neurons. To survive, neurons need a constant blood supply to deliver oxygen and glucose.
An AVM can affect this blood supply in two main ways. Because blood rushes through the AVM instead of the surrounding tissue, nearby brain areas may not get all the blood they need. And if the AVM bleeds, the bleeding and pressure can damage brain tissue. When brain cells don’t get enough oxygen, a chain reaction called the ischemic cascade can follow. The cell’s energy production fails, and a flood of a brain chemical called glutamate pushes neurons to fire faster than they can keep up with. This produces damaging molecules called free radicals and lets calcium rush into the cell, breaking down its proteins and eventually killing the neuron.
The walls of blood vessels can also break down from enzymes released by damaged cells. This can damage the blood-brain barrier and cause brain swelling, which can lead to further injury (3).
Seizures occur in about 15% to 40% of people with an AVM, as nerve cells near the tangle of vessels become less healthy and less stable (2).
How Is an AVM Diagnosed?
Several types of imaging can diagnose an AVM, including CT, MRI and CT or MR angiography. Cerebral angiography, in which dye is injected into the blood vessels and X-ray images are taken, is often used to map an AVM in detail (2).
How Is an AVM Usually Treated?
Treatment may or may not be recommended, depending on the AVM’s size and location and the risks and benefits of treatment. Options can include microsurgery, endovascular embolization, which blocks the AVM from inside the blood vessels, and focused radiation (radiosurgery), alone or in combination (2).
How the NeuroRescue Program Can Help
Our care is designed to work alongside your neurologist, neurosurgeon and interventional team, never in place of them. Please don’t change or stop any medication without talking with your prescriber.
Our history and exam process has led us to suspect AVMs that were not yet diagnosed, and in those cases we referred patients for imaging to confirm the diagnosis. When an AVM is found, we coordinate care with the appropriate vascular and interventional providers. There is nothing we can do about the AVM itself. But there are often functional problems we may be able to help with, and many people come to us for neurological rehabilitation after their AVM has been treated with embolization, surgery or radiosurgery.
One important idea in recovery from brain injuries like these is called diaschisis. Nerve cells need three main things to stay healthy: glucose, oxygen and activity. They need ongoing stimulation to keep making the proteins and other parts they need to stay healthy and work well. When an AVM or bleeding cuts off a brain area’s supply of oxygen and glucose, many of its nerve cells can be lost.
No one can bring back nerve cells that have been lost. But the lost cells usually aren’t the only reason for the symptoms after a brain injury.
That’s where diaschisis comes in. Each nerve cell receives signals from thousands of other nerve cells, and that input helps keep it active and healthy. When nerve cells are lost in a stroke, other nerve cells they connected to, even in areas with a normal blood supply, can lose that input. Those cells may become less active, lose endurance and tire easily, even though they still get plenty of glucose and oxygen (4).
These weakened but still-living nerve cells need the right amount of activity. Too little activity can leave them underused, while too much can overwhelm them. But if we can find another pathway that feeds into these cells, and activate it at a level they can handle, it may help rebuild function in the affected areas.
This idea guides our approach to rehabilitation after brain injuries, including those from an AVM. We use detailed testing to look not only at which areas are damaged, but also at which systems are still working but weakened. We look for pathways we can use to support those weakened systems, and we adjust how much and how often we stimulate them so they’re challenged without being overwhelmed. Then we choose therapies based on what your nervous system needs, with the goal of helping you recover as much function as possible.
Electrical stimulation. Gentle electrical stimulation of the nerves through the skin, called repetitive peripheral sensory stimulation, can stimulate the brain through the nerves of the body. It has been studied for improving movement in people with weakness on one side after brain injury from a stroke (5).
Light therapy. Photobiomodulation uses low-level laser and LED light. It has been studied as a way to support nerve cell energy and function after strokes and other blood vessel injuries in the brain (6, 7).
Transcranial magnetic stimulation. TMS uses magnetic pulses to stimulate specific areas of the brain. It has been studied for restoring movement and for chronic pain after injury to the brain’s motor areas (8, 9). Safety screening is especially important with an AVM, and TMS should not be applied directly over an AVM (10). At our clinic, TMS is provided by our psychiatric mental health nurse practitioner, who will carefully evaluate whether it may be appropriate and safe for you.
Balance and vestibular therapy. Balance problems are common with brain injuries, including those from an AVM, and they raise the risk of falls and head injuries. Reducing fall risk is a priority in our care. Vestibular therapy has been shown to help improve balance after a stroke (11).
Vision and eye movements. Vision is often affected by an AVM or by bleeding or surgery in the brain. People may have trouble mapping their surroundings and their body, keeping their eyes steady on a target, following moving objects or handling busy visual environments, and some lose part of their field of vision. We use visual exercises and rehabilitation tailored to your needs, an approach supported by research (12). Certain eye movement exercises have also been studied for supporting thinking and executive function (13), and one study found improvements in brain wave activity and symptom scores after a brain injury (14).
Constraint-induced movement therapy. Sometimes the best way to help a weak arm is to limit use of the stronger arm while doing intensive practice with the weaker one. This approach can help improve movement over time (15).
Mirror therapy. Mirror therapy uses a mirror image of your stronger limb to give your brain a different picture of the weaker limb during movement exercises (16). It has also been studied in a virtual reality environment (17), and we use our Virtualis system for this.
Mirror therapy. Mirror therapy uses a mirror image of your stronger limb to give your brain a different picture of the weaker limb during movement exercises (16). It has also been studied in a virtual reality environment (17), and we use our Virtualis system for this.
Physical exercise and soft tissue therapies can also help, and joint manipulation has been studied for improving movement after brain injury (18). Any hands-on care, including adjustments, is used only when appropriate, gentle and cleared as safe for your situation.
The therapies we recommend are always chosen based on your testing, exam findings and the guidance of your medical team.
How the NeuroRescue Program Works
Your NeuroRescue Program begins with your Discovery Day. We start with a detailed history of your condition and your life on a timeline. This helps us understand the factors that may have contributed to where you are now, and identify related conditions that may be making it harder to move forward.
We measure how your visual, vestibular and balance systems are working through computerized analysis of your eye movements, inner ear reflexes and balance under different conditions. Our testing includes videonystagmography and saccadometry to measure several types of eye movements, the video head impulse test to measure inner ear reflexes, and CAPS computerized posturography to assess your balance under different sensory conditions. We also use NeuroSensoryMotor Integration testing to evaluate hand-eye coordination and cognition, and Virtualis testing to assess dynamic eye tracking and your perception of vertical in a virtual reality environment.
We combine this with a thorough physical and neurological exam of your sensory, motor, autonomic and cognitive systems. We also review any relevant lab work, imaging and prior testing, and integrate it with our findings.
Together, this helps us understand which parts of your nervous system are working well, which are struggling, and how quickly they tire. We use that information to design your personal NeuroRescue Program, aimed at improving function in the systems that need support and helping them work together. Our testing also helps us decide when to push and when to let you rest.
Our goal is to help you regain as much function and confidence as possible, so you can do more of what matters to you.
Your Next Step
Living with an AVM, or recovering from one, can be frightening and exhausting. Recovery can continue long after treatment, and you don’t have to do it alone. To find out if the NeuroRescue Program is right for you, contact one of our patient care coordinators to schedule your Discovery Day.
It’s never too late to take the next step.
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