Understanding dural arteriovenous fistulas (DAVF)
What is a DAVF?
Our bodies contain an enormous network of blood vessels called arteries and veins that transport blood throughout the body.
Arteries carry high-pressure, oxygen-rich blood from the heart to the rest of our organs, and our veins bring low-pressure, oxygen-depleted blood back to the heart. Essential to this circuit are smaller blood vessels called capillaries, which not only allow blood to pass from our arteries to our veins, but also help reduce the force at which blood enters the veins.
A small number of people have patches of missing capillaries, meaning some of their arteries connect directly to veins. This abnormal connection is called an arteriovenous fistula, or fistula for short.
Sometimes fistulas develop in a part of the body called the dura mater, which is the tough membrane that covers and protects the brain. A fistula found in the dura mater is known as a dural arteriovenous fistula, or DAVF.
Over time, as blood flows through a DAVF, it causes pressure to build up in the network of veins found within the dura mater and around the brain. The continuous pressure may cause one of the veins to rupture, allowing blood to leak into your brain. This is a life-threatening condition that requires immediate medical treatment.
What causes DAVFs?
Although the medical community has made significant advancements in diagnosing and treating DAVFs, it still hasn't discovered precisely what causes them.
Many researchers believe DAVFs develop following an injury (including surgery) or infection — meaning people who have this condition probably were not born with it, but acquired it during life. On average, people with a DAVF do not experience symptoms until they are age 50 or older.
What are the symptoms of a DAVF?
As pressure builds up in the veins located in and around the brain, it can cause gradual but worsening symptoms. These progressive symptoms vary by individual, depending on where in the dura mater the DAVF is located, and which downstream veins are affected. They include:
- ringing in the ears or a whooshing noise in your head, called a bruit, that seems to pulse with your heartbeat (these are common symptoms in people who have a DAVF behind an ear)
- eye problems, including redness and swelling, caused by increased pressure in the veins that lead to the eyes
If one of your veins hemorrhages, causing blood to leak into your brain, it may cause the following sudden symptoms:
- severe headache
- difficulty speaking
- weakness in an arm or leg
- unsteadiness and difficulty walking
- partial or complete vision loss
- nausea or vomiting
A vein hemorrhage can range in severity from a very small leak that causes limited damage, to a massive leak that can lead to hemorrhagic stroke or death if left untreated.
Generally speaking, bleeding in the brain is a potentially life-threatening condition that requires immediate medical treatment.
How are DAVFs diagnosed?
If your doctor suspects you have a DAVF due to your gradual or sudden symptoms, he or she will likely order one or more of the following tests:
- A computerized tomography (CT) scan captures cross-sectional, X-ray images of the head and can confirm whether a hemorrhage has occurred. Your doctor may pair this scan with a special dye injected into your blood stream, so he or she can observe how well blood is flowing in your brain. This is called CT angiography.
- A magnetic resonance imaging (MRI) scan captures 3-D images of your brain (including the dura mater), and can help confirm the precise location of the DAVF as well as any damage to nearby brain tissue. Your doctor may use a variation of this test, called MR angiography or MRA, which shows the blood vessels in your brain in greater detail.
- A cerebral angiogram is a minimally invasive test that combines X-rays and a special dye to see inside the blood vessels in your brain. It is the most conclusive diagnostic test for DAVF because it allows your doctor to evaluate blood flow in real time. It also provides more detailed images of the abnormal veins and arteries, which is important for treatment planning.
How are DAVFs treated?
If you've been diagnosed with a dural arteriovenous fistula, your doctor will create a treatment plan for you that is based on several factors, including the size and location of the DAVF (together with its potential for hemorrhage), whether there is evidence of past or current bleeding, the severity of your symptoms and your overall health.
Treatment options for DAVF are designed to close the abnormal connection between its arteries and veins, and include:
- Endovascular embolization is a minimally invasive procedure that does not require open brain surgery. During the procedure, a neurosurgeon threads a small, flexible tube called a catheter through the arteries (often starting in the groin area) until it reaches an artery that "feeds" the DAVF with blood. Once the catheter is in place, the neurosurgeon injects one of several materials called embolizing agents — these include tiny metal coils and glue-like substances — to reduce or block blood flow into the DAVF.
- Conventional or "open" surgery may be used if the DAVF cannot be easily reached with a catheter or successfully blocked with embolizing agents. During the procedure, a neurosurgeon first performs a craniotomy to temporarily remove a piece of the skull and gain access to the brain, then uses surgical tools to seal off and remove the DAVF.
- Radiosurgery uses radiation beams to damage, and eventually close, the blood vessels that make up the DAVF (despite what the name implies, it is not surgery in the traditional sense because the procedure does not require cutting or an incision). During the procedure, multiple beams of radiation are simultaneously aimed at the brain. The beams meet at the DAVF to deliver a single, massive dose of radiation.
DAVF care at Lyerly Neurosurgery
Since Lyerly Neurosurgery was founded in 1934, our physicians have cared for thousands of people who need treatment for a brain or spine condition.
Today our practice continues to build upon a legacy that blends compassion, safety and innovation. Our neurosurgeons provide the full spectrum of evidence-based care, including the latest minimally invasive procedures that can only be offered by neurosurgeons with advanced training and experience.
If you or a loved one has been diagnosed with a dural arteriovenous fistula, you'll find the care and support you need at Lyerly Neurosurgery. In partnership with Baptist Medical Center Jacksonville, our team provides emergency and preventive DAVF treatment, including endovascular embolization by specialists who are fellowship trained in endovascular neurosurgery.