Dural Arteriovenous Fistulas

Overview

Dural arteriovenous fistulas (dAVFs) are abnormal connections between an artery and a vein in the tough covering over the brain or spinal cord (dura mater). In this rare condition, abnormal passageways between arteries and veins (arteriovenous fistulas) may occur in the brain, spinal cord or other areas of your body.

Dural AVFs tend to occur later in life (50 to 60 years of age), and they're not typically passed on genetically — children aren't more likely to develop a dAVF simply because their parent has.

Although some dAVFs stem from known causes, it's thought that dAVFs involving large brain veins usually form due to narrowing or blockage of one of the brain's venous sinuses, which normally 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, you may need surgery to disconnect or remove the dAVF.

Symptoms

Some people with a dAVF may not have any symptoms. However, noticeable symptoms can be characterized either as aggressive or benign.

Aggressive dAVF symptoms can result either from bleeding in the brain (intracerebral hemorrhage) or from neurological effects of nonhemorrhaging neurological deficits (NHNDs).

Bleeding in the brain often causes a sudden headache with varying degrees of neurological disability related to the location and size of the hemorrhage.

By contrast, an NHND usually develops more gradually, over days to weeks, and typically produces symptoms related to its location.

These aggressive symptoms can include:

• Difficulty walking, falls
• Seizures
• Speech or language issues
• Facial pain
• Dementia
• Parkinsonism
• Coordination issues
• Burning or prickling sensations
• Weakness
• Apathy
• Failure to thrive
• Symptoms related to increased pressure such as headaches, nausea and vomiting.

Other dAVF symptoms can include hearing issues, such as a bruit behind the ear, also known as pulsatile tinnitus. Other symptoms include vision problems such as:

• Visual deterioration
• Eye bulge
• Swelling in the eye lining
• Eye-related palsies
• Cavernous sinus syndrome.

In rare cases, progressive dementia may occur due to venous hypertension.

When to see a doctor

Make an appointment with a doctor if you develop any signs or symptoms that seem unusual or that worry you.

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

• Sudden, severe headache
• Nausea
• Vomiting
• Weakness or numbness on one side of the body
• Difficulties in speaking or understanding speech
• Loss of vision
• Double vision
• Balance difficulties

Causes

Most dural arteriovenous fistulas have no clear origin, although some result from identifiable causes such as traumatic head injury (or traumatic AV fistula), infection, previous brain surgery, venous thrombosis or tumors. Most authorities think that dAVFs involving the larger brain veins usually arise from progressive narrowing or blockage of one of the brain's venous sinuses, which route circulated blood from the brain back to the heart.

Risk factors

Genetic risk factors for dAVFs include those predisposed to blood clots in the vein (vein thrombosis). This may include abnormalities in the way the blood clots, which may increase the risk for a blockage or narrowing (occlusion) of the vein sinuses.

Most frequently, dAVFs affect people in their late-middle years (roughly from 50 to 60 years old). However, dAVFs can occur in younger age groups as well, including in children.

Recent evidence does suggest that benign meningeal tumors may also be associated with the development of dAVFs.

Diagnosis

If you have signs or symptoms of a dural arteriovenous fistula, your doctor may recommend that you undergo diagnostic imaging (radiology) tests. For dural arteriovenous fistulas, these may include:

• Initial imaging. Initial evaluation typically includes cross-sectional imagery from noncontrast head computerized tomography (CT) and magnetic resonance imaging (MRI).
• CT head scans. These tests can show fluid buildup caused by heightened cortical vein blood pressure as well as actual bleeding, which may be caused by a dAVF but occur elsewhere in the brain's venous system.
• MRIs. These images can establish the shape and extent of a dAVF, detect any micro-hemorrhages (very small bleed locations), and determine the impact of any abnormal blood vessel structures related to the fistula itself.
• Angiography. Catheter-based cerebral angiography (also known as digital subtraction angiography) is still the most reliable and definitive tool on dAVF diagnosis. 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
  • Fistula blood vessels' structure
  • Whether cardiovascular disease is also present
  • How much narrowing or blockage has occurred in the dural sinus
  • Whether any affected veins are dilated and to what extent

Superselective angiography may also be required to identify the area of convergence of the feeding dural arteries and the origin of the draining vein.

Treatment

Treatment for dural arteriovenous fistula generally involves surgery to block or disconnect the fistula.

Dural arteriovenous fistula surgery

• Endovascular procedures. In an endovascular procedure, your doctor may insert a long, thin tube (catheter) into a blood vessel in your leg or groin and thread it through blood vessels to the dural arteriovenous fistula using X-ray imaging.

  Your doctor inserts the catheter into the blood vessel that leads to the dAVF and releases coils or a glue-like substance to block the abnormal connection in the blood vessels.

• Stereotactic radiosurgery. In stereotactic radiosurgery your doctor uses precisely focused radiation to block the abnormal connection in the blood vessels. The high dose of radiation delivered to the fistula causes blood vessels to close off, destroying the dAVF. The different types of technology used to perform dAVF stereotactic radiosurgery include the linear accelerator (LINAC), 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 your 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 medications, 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 accompanies 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 doctor may want to ask questions of someone who has witnessed them, as it's common not to be aware of everything that happens when you experience one.

Write down questions to ask your doctor.

Preparing a list of questions will help you make the most of your time with your doctor. List your questions from most important to least important in case time runs out. Most of these would be covered during your visit. Some examples of good questions to ask your doctor 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 to ask your doctor, don't hesitate to ask questions during your appointment at any time that you don't understand something.

What to expect from your doctor

Your doctor is also likely to ask you a number of questions:

• When did you first begin experiencing symptoms (for example, hearing or vison problems, seizures, speech issues, palsies, or other symptoms)?
• Do your symptoms come and go (intermittent) 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 to:

• Avoid excessive alcohol consumption
• Avoid nicotine usage
• Get enough sleep
• Reduce stress