What is an Arteriovenous Malformation?

Jul 27

Arteriovenous malformation (or AVM) is a developmental issue involving blood vessels. It usually appears as a tangle of arteries and veins. Arteries usually supply blood to tissue via smaller vessels called capillaries, whereas veins return blood from tissue to the heart. In AVM, the arteries feed directly into the veins and do not supply blood to the tissue. They can occur anywhere in the body, but are present most commonly in the brain or spinal cord (1).

How Common are Arteriovenous Malformations?

New cases of AVMs detected annually appear in approximately 1 in 100,000 people. Its prevalence in the population is estimated at about 10 per 100,000. It does not appear to be associated with any particular ethnic or racial groups. Males and females are equally affected (2).

What are the Symptoms of an Arteriovenous Malformation?

AVMs are often asymptomatic and go unnoticed until another medical reason warrants imaging of the affected area. Other times, AVMs may cause headaches, seizures or weakness in one part of the body as they put pressure on intracranial structures. More serious symptoms that may present include severe headache, weakness, numbness or paralysis, vision loss, difficulty with speech, confusion and severe unsteadiness.

AVMs may also rupture, causing intracranial bleeds (hemorrhage) that result in stroke-like symptoms. Some symptoms that may be experienced as a result of this intracranial bleeding are visual disturbances, loss of sensation on one half of the body, headaches or migraines, and hemiparesis. Symptoms may begin to present anywhere between the ages of 10-40 (1). If present during pregnancy, women may experience more intense symptoms as their blood pressure naturally increases due to changes in blood volume.

What Causes an Arteriovenous Malformation?

It is suspected that AVM are a result from an error in embryonic or fetal development. There have not been any environmental risk factors identified for neurological AVM. They are usually not inherited from parents to offspring, but 5% of them do appear to be a result of genetic mutation (2).

What Happens in the Brain with Arteriovenous Malformations?

The brain is composed of many cell types. The ones we usually think of as brain cells are called neurons, which are the primary functional units of the brain. In order to survive, all neurons need a constant supply of blood to provide oxygen and glucose.

This blood supply is disrupted during AVM. This can lead to an ischemic cascade, where energy production within neurons that depends on the availability of oxygen starts to fail. This leads to a sudden release of glutamate, a neurotransmitter chemical that causes neurons to fire faster than their metabolic machinery can sustain. The result of this process is the production of many damaging free radicals, calcium rushing in and triggering the breakdown of proteins in the neuron, and ultimately death of the neuron.

Blood vessel walls can also break down from the release of cellular enzymes that destroy connective tissue. This can lead to breakdown of the blood-brain barrier and cerebral swelling, which can create secondary brain injuries (4).

Seizures are present in 15-40% of individuals with AVM as neurons near the blood vessel tangle become unhealthy and less stable (2).

How are Arteriovenous Malformations Usually Diagnosed?

A number of types of imaging studies can be used to diagnose AVM. The current gold standard for diagnosis is CT angiography, but regular CT scans or MRIs may also be used (2).

How are Arteriovenous Malformations Usually Treated?

Surgical removal may or may not be recommended for AVM, depending on estimated risks and benefits. This could include any combination of microsurgery, endovascular embolization and radiosurgery to address the issue (2).

How is the NeuroRescue Program Different?

We have identified several AVMs through our history and examination process, leading to referral for imaging to confirm the diagnosis. When an AVM has been identified, we coordinate care with the appropriate vascular and interventional providers. There is nothing that we can directly do about the AVM itself. That said, there are a number of functional issues that we can usually help to remediate in the presence of a vascular malformation. In many other cases, patients come to us for neurological rehabilitation after their AVMs have been embolized or surgically repaired.

One of the fundamental problems seen in AVM is what is called a diaschisis. Neurons need 3 main things to survive: glucose, oxygen, and activation. Neurons need to be continuously stimulated in order for them to continue replicating all of the protein and cellular components they need to survive and keep firing efficiently. When someone has an AVM, neurons that are supplied by the involved blood vessel are deprived of glucose and oxygen. Unfortunately, most of these will die off unless blood flow is restored.

There is nothing that we or anyone else can do to bring back the neurons that have been lost. However, the dead neurons are usually not entirely responsible for the symptoms seen as a result of AVM.

This is because of the diaschisis phenomenon. Each neuron receives activation signals from an average of 10,000 other neurons. This input will either excite or inhibit the neuron, but either way, the presence of this activation causes it to keep replicating protein and stay healthy. If the neuron is outside of the vascular distribution of an AVM, it may still be affected if enough of the neurons that activate it are lost. When neurons die from AVM, the neurons that they stimulate, even though they have a different blood supply and are not directly affected by AVM, will undergo diaschisis and start to break down. They will lose endurance, will not be able to sustain high rates of firing, and will tend to fatigue and fail. This will be the case even though they still have a normal supply of glucose and oxygen.

If these remaining fragile neurons affected by diaschisis are not properly activated, they will ultimately die off. If they are overstimulated and caused to fire at a rate that they cannot withstand, they will also be lost.

However, if another neuron or pathway that supplies input to the fragile cells can be found, and these can be stimulated to activate the damaged neurons at a rate that they can withstand, they can be used to rebuild the function in the injured cells (19).

This is exactly the basis of all of our NeuroRescue rehabilitation therapies. We use cutting edge neurodiagnostic technologies and examination procedures to not only identify what areas of your system are damaged, but also what systems are still present but impacted by diaschisis. We identify pathways that we can harness to rebuild the function of the fragile systems. We determine the exact frequency and intensity of stimulation of these pathways that leads to positive plastic changes without overstimulation. We then employ several of a vast array of therapies, chosen specifically for the unique needs of your system, to maximize your functional recovery.

Our therapies are constantly evolving, and are on the cutting edge of neurorehabilitation. Everything we do for rehabilitation is supported by the latest neuroscience research.

We use a wide array of neurostimulation strategies in restoring function lost from AVM. Electrical therapies can be harnessed to stimulate neurons in the brain through the peripheral nervous system. There are many different kinds of currents and applications that we employ, but these are collectively known as repetitive peripheral sensory stimulation. RPSS has been demonstrated to be effective in restoring function in patients suffering from AVM hemiparesis (5).

Photobiomodulation is another form of neurostimulation, using low level laser and LED light frequencies to help rebuild endurance and metabolic function in neurons after ischemic brain damage. We use several different types of laser and LED systems for AVM rehabilitation. Research shows that these can be very helpful to improve function in vascular injuries (6,7).

We regularly use transcranial magnetic stimulation (or TMS), which is an extremely effective form of neurostimulation in the treatment of AVM. TMS uses an MRI-strength magnet to apply a focused beam of electromagnetic energy through the skull and directly to the injured areas of the brain. This treatment is safe, with minimal rare side effects, as long as the location of the AVM is not directly under the magnet (8). More importantly, it is extremely effective for helping people manage chronic pain and restore motor function after damage to the motor cortex, sometimes seen with AVM (9,10). We have such great success with our TMS treatment that we installed our second TMS unit this year.

It is extremely common that people with AVM can develop balance difficulties. This greatly increases the risk of injury from falls, including further traumatic brain injuries. We go to great lengths to ensure that all of our patients have their fall risk reduced through precise vestibular therapy, which is part of every NeuroRescue program. Vestibular therapy has been shown to be very effective to improve balance after AVM (11).

Vision can very commonly be impaired by an AVM. It is common for people to develop difficulty visually mapping their world, holding their eyes still on targets, following moving objects, and processing complicated visual environments. In many cases, an entire visual field can be lost through damage to visual pathways. We use several types of visual exercises and rehabilitation to help resolve these difficulties, tailored to the unique needs of the patient. The effectiveness of visual therapies has solid support in neuroscience literature (12).

Specific types of eye movement exercises have been shown to be helpful in not only restoring visual function, but also in restoration of cognitive and executive function. Specific eye movement therapies have been shown help with cognitive retraining (13), and have demonstrated significant improvement in brainwaves and reduction in symptom scales (14).

We also use a number of unique therapies to help your brain remap your body and restore movement patterns affected by AVM. Sometimes the best way to restore movement in a paretic limb is to constrain the movement of the opposite limb while engaging in high intensity motor retraining exercises. Movement constraint therapy can be very helpful to restore motor function over time (15). Using different visual representations of the impaired limb by mirroring the good limb while engaging in movement exercises can be very helpful as well (16). Mirror therapy is particularly helpful when employed in a virtual reality environment (17), and we regularly see rapid changes in motor function when using our Virtualis VR system. And physical exercises and soft tissue rehabilitation techniques can be helpful once central neurological function has been addressed. In particular, joint manipulation can often lead to significant improvement in motor function (18).

How Does the NeuroRescue Program Work?

We design your unique NeuroRescue Program to be among the most comprehensive diagnostic and therapeutic protocols available today. We create individual NeuroRescue Programs based on a comprehensive analysis of every relevant neurological system and pathway, using gold-standard, cutting edge neurodiagnostic technologies and examination procedures and state-of-the-art therapies.

We begin with your Discovery Day, wherein we perform a comprehensive history of not only your condition, but also of your life on a timeline. This allows us to dive deeply into your case and see all of the factors that led to where you are now. It helps us uncover hidden problems and associated conditions that may be making it difficult for you to move your recovery forward.

Our examination allows us to identify the areas and pathways of your brain that have been directly and indirectly affected by your AVM. We do this by precisely quantifying the function of your visual, vestibular, and proprioceptive systems through computerized analysis of your eye movements, your inner ear reflexes, and your balance in a host of different sensory conditions.

We employ technologies including Videooculography and Saccadometry to measure several classes of eye movements. We use Video Head Impulse Testing to measure the function of your inner ear, and Computerized Dynamic Posturography to assess your balance in different sensory conditions.

We use NeuroSensoryMotor Integration testing to evaluate hand-eye coordination and cognition, and Virtualis testing to assess dynamic eye tracking and perception of vertical in a virtual reality environment.

We combine all of this with a comprehensive physical and neurological examination of your sensory, motor, autonomic, and cognitive systems. We review any relevant laboratory testing, radiological imaging, and prior neurodiagnostic testing, and integrate that information with our findings.

We use this information to identify which parts of your nervous system are working properly, which systems are struggling, and the precise point at which your systems fatigue.

We can then design a NeuroRescue Program that is unique and specific to your brain, and yours alone. Your NeuroRescue Program works to rejuvenate and reintegrate the damaged neurons and pathways in your central nervous system. It works to improve energy, endurance, and functional capacity within your involved fragile systems.

We use our technologies and procedures to not only see what we need to address, but also when it is time to stop and let you rest. We address your impaired neurological function from multiple angles of therapy, and provide metabolic support to improve neurological recovery.

While we cannot bring back neurons that have been lost, your NeuroRescue Program allows us to take the pathways that remain and maximize their efficiency and endurance. And by focusing on the integration of systems, we can do more than just get pathways working better, we can get them working together again. This gives us our best opportunity to get your AVM symptoms under control, and return you to living a healthy, vibrant, and fulfilling life.

Your Next Best Step:

Living with an AVM can be challenging, but there is hope for recovery. To see if the NeuroRescue Program is right for you, contact one of our patient care coordinators to schedule your Discovery Day.

And remember, it’s never too late to start getting better.