Dural arteriovenous fistulas

Overview

Dural arteriovenous fistulas (dAVFs) are irregular connections between arteries and veins. They occur in the tough covering over the brain or spinal cord, known as the dura mater. The irregular passageways between arteries and veins are called arteriovenous fistulas, which can lead to bleeding in the brain or other serious symptoms.

Dural AVFs are rare. They tend to occur between ages 50 and 60. They are not typically genetic, so children are not more likely to develop a dAVF if their parent has one.

Although some dAVFs stem from known causes, most often the cause is not known. It's thought that dAVFs involving large brain veins form when one of the brain's venous sinuses narrows or becomes blocked. Venous sinuses are channels that route circulated blood from the brain back to the heart.

Treatment for dAVF usually involves an endovascular procedure or stereotactic radiosurgery to block the blood flow to the dAVF. Or surgery may be needed to disconnect or remove the dAVF.

Symptoms

Some people with dural arteriovenous fistulas (dAVFs) may not have symptoms. When symptoms occur, they may be characterized as benign or aggressive. An aggressive dAVF has more-serious symptoms.

Aggressive dAVF symptoms can result from bleeding in the brain, known as intracerebral hemorrhage. Bleeding in the brain often causes a sudden headache. It also may cause other symptoms based on the location and size of the hemorrhage.

Aggressive symptoms also may result from nonhemorrhagic neurological deficits (NHNDs), which can include seizures or changes in mental abilities. These symptoms usually develop more gradually, over days to weeks. Symptoms are typically related to the area of the brain affected.

Aggressive symptoms can include:

• Sudden headache.
• Trouble walking and falls.
• Seizures.
• Speech or language issues.
• Facial pain.
• Dementia.
• Slowed movement, stiffness and tremor, known as parkinsonism.
• Trouble with coordination.
• Burning or prickling sensations.
• Weakness.
• Lack of interest, known as apathy.
• Failure to thrive.
• Symptoms related to increased pressure, such as headaches, nausea and vomiting.

Other dAVF symptoms can include hearing issues. People with hearing symptoms may hear a rhythmic sound in the ear that occurs with the heartbeat, known as pulsatile tinnitus. Symptoms also may include trouble with vision, such as:

• Vision changes.
• Eye bulge.
• Swelling in the eye lining.
• Paralysis of a muscle in or around the eye.

Rarely, dementia may occur due to increased pressure in the blood vessels in the brain.

When to see a doctor

Make an appointment with your healthcare professional if you have any symptoms that are not usual or that worry you.

Seek medical help immediately if you experience a seizure or symptoms that suggest brain hemorrhage, such as:

• Sudden, severe headache.
• Nausea.
• Vomiting.
• Weakness or numbness on one side of the body.
• Trouble speaking or understanding speech.
• Loss of vision.
• Double vision.
• Trouble with balance.

Causes

Most dural arteriovenous fistulas (dAVFs) have no clear origin. But some result from a traumatic head injury, infection, previous brain surgery, blood clots in deep veins or tumors.

Most experts think that dAVFs involving larger brain veins occur from the narrowing or blockage of one of the brain's venous sinuses. The venous sinuses are channels in the brain that route circulated blood from the brain back to the heart.

Risk factors

Risk factors of dural arteriovenous fistulas (dAVFs) include being inclined to blood clots in the vein, known as vein thrombosis. Changes in the way the blood clots may increase the risk of a blockage or narrowing of the venous sinuses.

Most often, dAVFs affect people between ages 50 and 60. But they can occur in people at younger ages, including in children.

Research has found that noncancerous tumors found in the membranes that surround the brain and spinal cord may be associated with dAVFs.

Diagnosis

If you have symptoms of a dural arteriovenous fistula (dAVF), you may need imaging tests.

• CT scans. These tests can show fluid buildup caused by increased blood pressure in the brain. They also can show bleeding that may be caused by a dAVF.
• MRIs. MRI images can reveal the shape of a dAVF. An MRI also can detect very small bleeds. The test may determine the impact of any irregular blood vessel structures.
• Angiography. Catheter-based cerebral angiography, also known as digital subtraction angiography, is the most reliable tool to diagnose dAVF. It's essential for defining:
• How many fistulae exist and where.
• Anatomy of the external carotid arteries and any branches between them and the dura. Carotid arteries deliver blood to the brain and head.
• Fistula blood vessels' structure.
• Whether cardiovascular disease also is present.
• How much narrowing or blockage has occurred in the dural sinus.
• Whether any affected veins are dilated and to what extent.

Treatment

Treatment for a dural arteriovenous fistula (dAVF) involves a procedure to block or disconnect the fistula.

Dural arteriovenous fistula surgery

Procedures that can treat dAVF include:

• Endovascular procedures. In an endovascular procedure, a long, thin tube called a catheter is inserted into a blood vessel in your leg or groin. It is threaded through blood vessels to the dural arteriovenous fistula using X-ray imaging. Coils or a glue-like substance is released to block the connection in the blood vessels.
• Stereotactic radiosurgery. In stereotactic radiosurgery, precisely focused radiation blocks the irregular connection in the blood vessels. This causes blood vessels in the fistula to close off, destroying the dAVF. Different types of technology may be used in stereotactic radiosurgery. They include the linear accelerator, Gamma Knife and proton beam therapy.
• dAVF surgery. If an endovascular procedure or stereotactic radiosurgery aren't options for you, you may need dAVF surgery. Surgery may be performed to disconnect the dAVF or cut off the blood supply and remove the fistula.

Preparing for an appointment

What you can do

• Keep a detailed symptoms calendar. Each time a symptom occurs, write down the date and time, what you experienced and how long it lasted.
• Write down key personal information, including any major stresses or recent life changes.
• Make a list of all medicines, vitamins or supplements that you're taking.
• Take a family member or friend along. 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 missed or forgot.
• Bring along any recent brain scans in a CD to your appointment. Also, if you've experienced seizures, your healthcare professional may want to ask questions of someone who has witnessed them. It's common not to be aware of everything that happens during a seizure.

Write down questions to ask your doctor.

Preparing a list of questions will help you make the most of your time during your appointment. List your questions from most important to least important in case time runs out. Some examples of questions include:

General Questions

• Where is the fistula located?

Management and observation

• Will I need follow-up tests?
• If so, how often will I follow up with you?

Surgery to disconnect a fistula

• How long would you estimate I'd be in surgery?
• How long does surgery recovery usually take?
• How long should I plan to be in the hospital?

Surgical background

• How many dAVFs have you seen and how many have you treated?
• Does your institution have a cerebrovascular specialty practice?

In addition to the questions you've prepared, don't hesitate to ask others during your appointment at any time that you don't understand something.

What to expect from your doctor

Your healthcare professional is likely to ask you a number of questions:

• When did you first begin experiencing symptoms? For example, have you experienced hearing or vison problems, seizures, speech issues, paralysis, or other symptoms?
• Do your symptoms come and go or are they persistent?
• Do your symptoms seem to be triggered by certain events or conditions?

What you can do in the meantime

Certain conditions and activities can trigger seizures, so it may be helpful if you:

• Don't drink excessive amounts of alcohol.
• Don't use nicotine.
• Get enough sleep.
• Reduce stress.