Cerebral Arteriovenous Fistula
Cerebral arteriovenous fistulas (AVF) are abnormal connections between arteries and veins. Normally, arteries carry blood away from the heart to different parts of the body, and you can feel a pulse in an artery because they have high pressure in them. Larger arteries branch into smaller and smaller branches until they get down to tiny branches called capillaries, and that is where the oxygen and nutrients are exchanged with the tissues in your body. The blood is then returned from the tissues in veins. The veins have very low pressure, and you cannot feel a pulse in a vein.
You can get high pressure in the veins, and that can backup the system and lead to bleeding or other problems—because the veins cannot handle high pressure. In the case of an AVF, arteries are connected directly to veins, and when this occurs in the brain it can potentially be a life-threatening problem.
Signs and Symptoms
Symptoms of cerebral arteriovenous fistulas are dependent on their size and location. Some AVFs do not cause symptoms.
AVFs are commonly associated with the following symptoms:
- Bruit or pulsatile tinnitus: a “whooshing” sound in one ear that follows your heartbeat
- Swelling or redness in one or both eyes when fistulas develop in the cavernous sinus behind the eye
- Difficulties with memory or concentration
Fistulas, if growing too fast or not identified soon enough, can lead to increased pressure in the veins of the brain. This increased pressure makes the chance of seizure or stroke greater.
Fistulas can occur after trauma, but many times they happen spontaneously for no known reason. Some people have no symptoms at all.
Many other conditions can cause the same symptoms, so it is important to check with your doctor for an accurate diagnosis. Only a doctor experienced in recognizing the exact combination of symptoms that indicate an AVF can make a firm diagnosis.
Diagnosis of an AVF starts with a physical exam and medical history. Other procedures and tests may be needed to diagnose, including: angiography , magnetic resonance imaging ( MRI ) or CT scans. Sometimes a fistula will be seen on an MRI or a CT scan, but the gold standard to find a fistula is with angiography.
If you have a fistula, there are four different ways it can be treated.
- Observation This is recommended when there does not appear to be high pressure in the veins, and the patients have minor or no symptoms.
- Radiation treatment This is generally not recommended unless the other options are not effective because radiation does not lead to an immediate cure of the fistula, and it may take many years for it to go away after the treatment.
- Embolization A catheter is placed in the arteries or veins, and then the catheter is “snaked” all the way up to where the fistula is located. A special glue is then injected to shut down the fistula from the inside. The advantage of this is you do not have to have surgery on your head, but there are some fistulas that embolization cannot cure.
- Fistula disconnection surgery This is done using anesthesia, with the patient completely asleep. The hair is parted and not shaved, and an incision is made depending on the location of the fistula. A window is made in the bone, and the same bone is put back at the end. Using a microscope, the fistula is located. The fistulas are usually on the surface of the brain and it is rarely required to enter into any brain tissue. Once the fistula is located, metal clips are placed on it to shut it down. If all of the abnormal connections are shut down, then the fistula is cured at that time. Usually, an angiogram is done during the surgery to make sure that the fistula is completely gone. At that point, everything is closed. After surgery, patients will spend at least one night in intensive care. After that, they will move to the regular floor and usually within a few days they are going home. Sometimes a final angiogram is done before they are sent home to obtain a clear image of the brain following surgery. If the patient had weakness or confusion before surgery or developed weakness or confusion after surgery, they may need some rehabilitation before they go home.