The arteries are involved in taking oxygen-rich blood from the heart to the brain. Veins transport the deoxygenated blood back to the lungs and heart. A brain AVM causes disruption in this vital process.
An arteriovenous malformation may occur anywhere in your body, but it most commonly occurs in the brain or spine. Brain AVMs are rare and affect less than 1% of the population.
The cause of AVMs is unclear. Most of the time, it is present at birth, but they can occasionally develop later in life. They rarely run in families.
Some people with brain AVMs experience signs and symptoms, such as a headache or seizures.
AVMs are commonly identified during a brain scan done for another health issue or after the blood vessels burst and cause bleeding in the brain (hemorrhage).
Once diagnosed, a brain AVM is treated successfully to prevent complications, such as brain damage or stroke.
A brain AVM (arteriovenous malformation) may not cause any signs or symptoms until the AVM ruptures, resulting in bleeding in the brain (hemorrhage). In more than half of all brain AVMs, hemorrhage is the first sign.
But, in some people with brain AVM, signs and symptoms other than bleeding related to the AVM may occur:
In people without hemorrhage, signs and symptoms of a brain AVM may include:
A headache or pain in one side of the head
Muscle weakness or numbness on one side of the body
Some people may experience more serious neurological signs and symptoms, depending on the location of the AVM, including:
Weakness, numbness or paralysis
Difficulty in speaking
Confusion or inability to understand others
Symptoms may appear at any age but commonly develop between the ages 10 and 40. Brain AVMs can damage the brain tissue over time.
These effects slowly build up and cause symptoms in early adulthood. Once you are at middle age, however, brain AVMs tend to remain stable and rarely cause symptoms.
Some pregnant women may have serious symptoms due to changes in blood volume and blood pressure.
One severe type of brain AVM is called a vein of Galen defect that leads to signs and symptoms that appear soon or immediately after birth.
The major blood vessel involved in this type of brain AVM can cause fluid to build up in the brain and the head to swell.
Signs and symptoms include swollen veins that are visible on the scalp, seizures, failure to thrive and congestive heart failure.
When to see a doctor
Seek immediate medical attention if you see any signs or symptoms of a brain AVM, such as seizures, headaches or other symptoms.
A bleeding brain AVM can be fatal and requires emergency medical attention.
The exact cause of brain AVM is not known, but researchers believe that most brain AVMs form during fetal developmental stages.
Your heart sends oxygen-rich blood to your brain through the arteries.
The arteries reduce blood passing through a series of progressively smaller networks of blood vessels, ending with the smallest blood vessels (capillaries).
The capillaries slowly deliver oxygen through their thin, porous walls to the surrounding brain tissue.
The oxygen-depleted blood then passes into small blood vessels and then into larger veins that drain the blood from your brain, returning it to your heart and lungs to get more oxygen.
The arteries and veins in an AVM are devoid of this supporting network of smaller blood vessels and capillaries.
Instead, the abnormal connection results in quicker blood flow directly from your arteries to veins, bypassing the surrounding tissues.
4 Making A Diagnosis
A brain AVM is usually diagnosed in an emergency situation, soon after bleeding (hemorrhage) has occurred. It may sometimes 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).
As there is often a lot to discuss, it is a good idea to be well-prepared for your appointment. Here are some tips that help you get ready for your appointment, and what to expect from your doctor.
What you can do:
Be aware of your pre-appointment restrictions. At the time you make an appointment, always ask whether there is anything you need to do in advance.
Write down any symptoms you have, including those that may seem unrelated to the reason for your scheduled appointment.
Make a list of all your regular medications, vitamins and supplements.
Ask a family member or friend to accompany you, if possible. Sometimes, it can be difficult to remember all the information provided to you during an appointment. Someone who comes with you may remember something that you must have forgotten or missed.
Write down questions to ask your doctor. Do not hesitate to ask any questions that may come up during your appointment.
Your time with your doctor is likely to be brief, so prepare a list of questions in advance. For brain AVM, some basic questions to ask your doctor include:
What may be the other possible causes of my symptoms?
Which tests would be needed to confirm the diagnosis?
What are my treatment options and the advantages and disadvantages of each?
What results can I expect?
What kind of follow-up should I expect?
What to expect from your doctor
Your neurologist may ask you about your symptoms, if any, conduct a physical examination and order 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 or worsen your symptoms?
What you can do in the meantime
Avoid performing activities that may increase your blood pressure and put a strain on a brain AVM, such as heavy lifting or straining.
Avoid blood-thinning medications, such as warfarin.
To diagnose a brain AVM, your neurologist reviews your symptoms and conducts a physical examination.
Your doctor may order the following tests to diagnose your condition. Radiologists trained in brain and nervous system imaging (neuroradiologists) usually conduct imaging tests.
Cerebral arteriography: Cerebral arteriography, also called 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, which is very important to plan a treatment. In this test, your doctor will insert a long, thin tube (catheter) into an artery in the groin and thread 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 cross-sectional 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): MRI uses powerful magnets and radio waves to create detailed images of your brain. It is more sensitive than CT and can show very subtle changes in brain tissue associated with a brain AVM.
The exact location of the malformation and any related bleeding in the brain, which is important for determining treatment options. Your doctor may also inject dye to see the blood circulation in your brain (magnetic resonance angiogram).
There are different treatment options for brain AVM. The main objective of treatment is to prevent hemorrhage, but treatment to control seizures or other neurological complications also may be considered.
Your doctor will determine the most appropriate treatment for your condition, depending on your age, health, the size, and location of the abnormal blood vessels.
Medications also may be used to treat symptoms caused by the AVM, such as headaches or seizures.
Surgery is the most common treatment for brain AVMs. There are several surgical options for treatment of AVMs:
Surgical removal (resection): If the brain AVM has ruptured or is in an area that can easily be reached, surgical removal of the AVM through conventional brain surgery may be recommended.
In this procedure, your neurosurgeon removes a part of your skull temporarily to gain access to the AVM. With the help of a high-powered microscope, the surgeon seals off the AVM with special clips and carefully removes it from surrounding brain tissue.
The surgeon then attaches 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.
The catheter is positioned in one of the feeding arteries to the AVM, and an embolizing agent is injected, such as small particles, a glue-like substance, micro coils or other materials, to block the artery and reduce blood flow into the AVM.
Endovascular embolization is less invasive than traditional surgery. It may be performed alone, but is frequently used prior to other surgical treatments to make the procedure safer by reducing the size of the AVM or the likelihood of bleeding.
In some large brain AVMs, endovascular embolization may be used to reduce stroke-like symptoms by redirecting blood back to normal brain tissue.
Stereotactic radiosurgery (SRS): This treatment uses very precisely focused radiation to destroy the AVM. It is not a surgery in the literal sense as there is no incision.
Instead, SRS directs several highly targeted radiation beams at the AVM to damage the blood vessels and cause scarring. The scarred AVM blood vessels then slowly clot in one to three years following treatment.
This treatment is most appropriate for small AVMs that are difficult to remove with conventional surgery and for those that have not caused a life-threatening hemorrhage. If you have few or no symptoms or if your AVM is in an area of your brain that is hard to treat, your doctor may prefer to monitor your condition with regular checkups.
Potential future treatments
Researchers are studying ways to predict the risk of hemorrhage in people with brain AVM that better guides treatment decisions.
For example, high blood pressure within the AVM and hereditary syndromes associated with neurological issues may play a role.
Innovations in imaging technology, such as 3-D imaging, functional imaging, and brain tract mapping also are being evaluated and have the potential to improve surgical precision and safety in removing brain AVMs and preserving surrounding vessels.
In addition, ongoing advances in embolization, radiosurgery and microsurgery techniques are making previously inoperable brain AVMs more accessible and safer for surgical removal.
A diagnosis of a brain AVM can be frightening. It can make you feel as if you have lost control over your health. You can take certain steps to cope up with the emotions that accompany your diagnosis and recovery.
Consider trying to:
Try learning about brain AVM to make informed decisions about your care: Ask your doctor about the size and location of your brain AVM and how that affects your treatment options. As you know more about brain AVMs, you may become more confident in making treatment decisions.
Accept your emotions: Complications of brain AVM, such as hemorrhage and stroke, can cause emotional problems as well as physical ones. Recognize that emotion may be hard to control, and some emotional and mood changes may be caused by the injury itself as well as coming to terms with the diagnosis.
Keep friends and family close: Keeping your close relationships strong will help you during your recovery. Friends and family can provide the practical support you will need, such as accompanying you to doctors' appointments, and serving as an emotional support.
Find someone to talk with: Find a good listener who is willing to listen to you talk about your hopes and fears. This may be a friend or family member. The concern and understanding of a counselor, medical social worker, clergy member or support group also may be helpful.
Ask your doctor about support groups in your area: Or check your phone book, library or a national organization, such as the American Stroke Association or the Aneurysm and AVM Foundation.
7 Risks And Complications
Any person can be born with a brain AVM, but these are the risk factors:
Being male: AVMs occur most often in males.
Having a family history: Cases of AVMs running in families have been reported, but it is not clear whether there is a certain genetic factor or if the cases are only coincidental.
It is also possible to inherit other medical conditions that can predispose you to have vascular malformations such as AVMs.
Complications of a brain AVM include:
Bleeding in the brain (hemorrhage): An AVM exerts extreme pressure on the walls of the affected arteries and veins, causing them to become thin or weak. This may result in rupture of the AVM and bleeding into the brain (a hemorrhage).
This risk of a brain AVM bleeding ranges around 2% each year. The risk of hemorrhage may be higher for certain types of AVMs, or if you have experienced previous AVM ruptures.
Sometimes, hemorrhages associated with AVMs remain undetected as they cause no major brain damage or symptoms, but potentially life-threatening bleeding episodes may occur.
Brain AVMs account for about 2 percent of all hemorrhagic strokes each year and are often the cause of hemorrhage in children and young adults who experience brain hemorrhage.
Reduced oxygen to brain tissue: With an AVM, blood bypasses the network of capillaries and flows directly from arteries to veins. Blood flows quickly through the altered path because it is not slowed down by channels of smaller blood vessels.
Surrounding brain tissues cannot absorb oxygen from the fast-flowing blood. Without enough oxygen, brain tissues may weaken or die off completely. This results in stroke-like symptoms, such as difficulty in 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 (an aneurysm) may develop in a blood vessel wall, which becomes susceptible to rupture.
Brain damage: As you grow, your body may involve more arteries to supply blood to the fast-flowing AVM. As a result, some AVMs become bigger, displace or compress portions of the brain.
This may prevent protective fluids from flowing freely around the hemispheres of the brain. If fluid accumulates, it can push brain tissue up against the skull (hydrocephalus).
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