A brain AVM (arteriovenous malformation) is an abnormal connection between arteries and veins. An AVM is usually congenital, meaning it dates to birth.
An AVM can develop anywhere in your body but occurs most often in the brain or spine. A brain AVM, which appears as a tangle of abnormal arteries and veins, can occur in any part of your brain. The cause isn't clear.
You may not know you have a brain AVM until you experience symptoms, such as headaches or a seizure. In serious cases, the blood vessels rupture, causing bleeding in the brain (hemorrhage). Once diagnosed, a brain AVM can often be treated successfully.
A brain AVM (arteriovenous malformation) may not cause any signs or symptoms until the AVM ruptures, resulting in bleeding in the brain (hemorrhage). However, some people with an AVM may have symptoms other than bleeding that are related to the AVM.
An AVM may also be detected on a brain scan performed for reasons unrelated to the AVM.
Symptoms of a brain AVM include:
A whooshing sound (bruit) that can be heard on examination of the skull with a stethoscope or may be audible if you have an AVM
Progressive weakness or numbness
Some people may experience more-serious neurological symptoms, depending on the location of the AVM, including:
Weakness, numbness or paralysis
Inability to understand others
Symptoms may begin at any age, but you're more likely to experience symptoms between ages 10 and 40. Brain AVM can damage brain tissue over time. The effects slowly build up, sometimes causing symptoms in early adulthood.
Once you reach middle age, however, brain AVMs tend to remain stable and are less likely to cause symptoms.
Some pregnant women may have worsened symptoms. However, it's not clear that pregnant women are at greater risk of an AVM bleeding. More research is needed to determine the risk during pregnancy.
When to see a doctor
Seek immediate medical attention if you notice any signs or symptoms of a brain AVM, such as seizures, headaches or other symptoms. A bleeding brain AVM is life-threatening and requires emergency medical attention.
A brain AVM is an abnormal connection between arteries and veins in your brain. Doctors believe that a brain AVM develops during fetal development. Why this occurs in some babies and not others is unknown.
Normally, your heart sends oxygen-rich blood to your brain through arteries, which branch into smaller arterioles and subsequently to the smallest blood vessels (capillaries). Oxygen is removed from blood in the capillaries and used by your brain.
The oxygen-depleted blood then passes into small venules and then into larger veins that drain the blood from your brain, returning it to your heart and lungs to get more oxygen.
If you have a brain AVM, blood passes directly from your arteries to your veins via abnormal vessels. This disrupts the normal process of how blood circulates through your brain.
Anyone can be born with a brain AVM, but these factors may be a risk:
Being male. AVMs are more common in males.
Having a family history. Cases of AVMs in families have been reported, but it's unclear if there's a certain genetic factor or if the cases are only coincidental. It's also possible to inherit other medical conditions that predispose you to having vascular malformations such as AVMs.
Complications of a brain AVM include:
Bleeding in the brain (hemorrhage). Walls of the affected arteries and veins may become thin or weak. An AVM puts extreme pressure on these walls because no capillaries are available to slow down the blood flow. This may result in bleeding into the brain (a hemorrhage).
A very small (microscopic) hemorrhage causes limited damage to surrounding tissues and is unlikely to produce noticeable symptoms. A larger hemorrhage, however, can cause brain damage. It is known as an intracerebral hemorrhage when bleeding occurs in the brain tissue.
Reduced oxygen to brain tissue. With an AVM, blood bypasses the network of capillaries and flows directly from arteries to veins. Blood rushes quickly through the altered path because blood isn't slowed down by channels of smaller blood vessels.
Surrounding brain tissues can't easily absorb oxygen from the fast-flowing blood. Without enough oxygen, brain tissues weaken or may die off completely. This results in stroke-like symptoms, such as difficulty speaking, weakness, numbness, vision loss or severe unsteadiness.
Thin or weak blood vessels. An AVM puts extreme pressure on the thin and weak walls of the blood vessels. A bulge in a blood vessel wall (aneurysm) may develop and become susceptible to rupture.
Brain damage. As you grow, your body may recruit more arteries to supply blood to the fast-flowing AVM. As a result, some AVMs enlarge, which displaces or compresses portions of the brain. This may prevent protective fluids from flowing freely around the hemispheres of the brain.
If fluid builds up, it can push brain tissue up against the skull (hydrocephalus).
A brain AVM may be diagnosed in an emergency situation, immediately after bleeding (hemorrhage) has occurred. It may also be detected after other symptoms prompt a brain scan.
But in some cases, a brain AVM is found during diagnosis or treatment of an unrelated medical condition. You may then be referred to a doctor trained in brain and nervous system conditions (neurologist or neurosurgeon).
Because there's often a lot to discuss, it's a good idea to arrive well-prepared for your appointment. Here are some tips to help you get ready for your appointment, and what to expect from your doctor.
What you can do
Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance.
Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
Make a list of all medications, vitamins and supplements that you're taking.
Ask a family member of friend to come with you, if possible. Sometimes it can be difficult to absorb all the information provided to you during an appointment. Someone who accompanies you may remember something that you forgot or missed.
Write down questions to ask your doctor. Don't be afraid to ask questions that may come up during your appointment.
Your time with your doctor is limited, so preparing a list of questions ahead of time will help you make the most of your time together. For brain AVM, some basic questions to ask your doctor include:
What are other possible causes for my symptoms?
What tests are needed to confirm the diagnosis?
What are my treatment options and the pros and cons for each?
What results can I expect?
What kind of follow-up should I expect?
What to expect from your doctor
Your neurologist is likely to ask about your symptoms, if any, conduct a physical examination and schedule tests to confirm the diagnosis.
The tests gather information about the size and location of the AVM to help direct your treatment options. He or she may ask:
When did you first begin experiencing symptoms?
Have your symptoms been continuous or occasional?
How severe are your symptoms?
What, if anything, seems to improve your symptoms?
What, if anything, appears to worsen your symptoms?
To diagnose a brain AVM, your neurologist will review your symptoms and conduct a physical examination.
Your doctor may order one or more tests to diagnose your condition. Radiologists trained in brain and nervous system imaging (neuroradiologists) usually conduct imaging tests.
Tests used to diagnose brain AVMs include:
Cerebral arteriography. Cerebral arteriography, also known as cerebral angiography, is the most detailed test to diagnose an AVM. The test reveals the location and characteristics of the feeding arteries and draining veins.
In this test, your doctor inserts a long, thin tube (catheter) into an artery in the groin and threads it to your brain using X-ray imaging. Your doctor injects dye into the blood vessels of your brain to make them visible under X-ray imaging.
Computerized tomography (CT) scan. A CT scan uses a series of X-rays to create a detailed image of your brain.
Sometimes a doctor injects dye through an intravenous tube into a vein so that the arteries feeding the AVM and the veins draining the AVM can be viewed in greater detail (computerized tomography angiogram).
Magnetic resonance imaging (MRI). An MRI, more sensitive than a CT scan in showing the AVM, uses powerful magnets and radio waves to create detailed images of your brain.
MRI also provides information about the exact location of the malformation, which is very important for determining treatment options.
Your doctor may inject dye to see the blood circulation in your brain (magnetic resonance angiogram).
There are several potential treatment options for brain AVM. Your doctor will determine the most appropriate treatment for your condition, depending on the size and location of the abnormal blood vessels.
Medications may also be used to treat related symptoms, such as headaches or seizures.
Other treatments may include:
Surgical removal (resection). Surgical treatment of a small brain AVM is relatively safe and effective. In this procedure, your neurosurgeon removes part of your skull temporarily to gain access to the AVM.
Your neurosurgeon, aided by a high-powered microscope, seals off the AVM with special clips and carefully removes it from surrounding brain tissue. Your surgeon then reattaches the skull bone, and closes the incision in your scalp.
Resection is usually done when the AVM can be removed with little risk of hemorrhage or seizures. AVMs that are in deep brain regions carry a higher risk of complications. In these cases, your doctor may recommend other treatments.
Endovascular embolization. In this procedure, your doctor inserts a long, thin tube (catheter) into a leg artery and threads it through blood vessels to your brain using X-ray imaging.
Your surgeon positions the catheter in one of the feeding arteries to the AVM, and injects small particles of a glue-like substance to block the artery and reduce blood flow into the AVM.
Endovascular embolization may be performed before other treatments to reduce the size of the AVM, before surgery to reduce the chance of bleeding during the procedure or alone as a treatment. In some large brain AVMs, endovascular embolization may reduce stroke-like symptoms by redirecting blood back to normal brain tissue.
Stereotactic radiosurgery. This treatment uses precisely focused radiation to destroy the AVM. The radiation causes the AVM vessels to slowly clot off in one to three years following the treatment.
This treatment is most appropriate for small AVMs and for those that haven't caused a life-threatening hemorrhage.
If you have few or no symptoms or if your AVM is in an area of your brain that's hard to treat, your doctor may prefer to monitor your condition with regular checkups.