Dural arteriovenous fistula

Dural arteriovenous fistula (DAVF) is a rare, abnormal connection between an artery and a vein within the protective covering of the brain (the dura mater). Unlike most arteriovenous malformations, DAVFs involve only the vessels within the dura mater and do not affect the brain tissue directly. However, they can lead to significant complications due to the abnormal blood flow and pressure they introduce into the venous system of the brain.

Etiology

The exact cause of DAVFs is not well understood, but they may result from a combination of genetic predisposition and environmental factors. In some cases, DAVFs have been associated with a history of head injury, sinus surgery, or infections. They can also occur spontaneously without any identifiable cause.

Pathophysiology

In a healthy individual, arteries carry oxygen-rich blood from the heart to the brain, and veins carry oxygen-depleted blood back to the heart. In a DAVF, this normal flow is disrupted. An abnormal connection forms between a dural artery and a dural vein or a venous sinus, leading to increased pressure and abnormal blood flow within the venous system. This can result in venous hypertension, venous congestion, and reduced cerebral perfusion, potentially causing brain damage or hemorrhage.

Symptoms

Symptoms of DAVFs can vary widely depending on their location and the degree of venous hypertension. Common symptoms include:

• Pulsatile tinnitus (a whooshing sound in the ear)
• Headache
• Eye symptoms (such as redness, vision loss, or eye bulging)
• Neurological deficits (such as weakness or numbness in a limb)
• Seizures

In severe cases, DAVFs can lead to intracranial hemorrhage, which is a life-threatening condition requiring immediate medical attention.

Diagnosis

The diagnosis of DAVFs typically involves a combination of clinical evaluation and imaging studies. Magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) can provide detailed images of the brain's blood vessels, but digital subtraction angiography (DSA) is considered the gold standard for diagnosing DAVFs. DSA offers the most detailed view of the blood vessel architecture and the specific characteristics of the fistula.

Treatment

Treatment options for DAVFs depend on their location, severity, and the symptoms they cause. The main goals of treatment are to eliminate the abnormal connection and to restore normal blood flow. Treatment options include:

• Endovascular embolization: A minimally invasive procedure in which materials are injected through a catheter to block the abnormal blood vessels.
• Surgery: In some cases, surgical removal of the fistula may be necessary.
• Stereotactic radiosurgery: A form of radiation therapy that focuses high-powered x-rays on a small area to close off the fistula.

Prognosis

The prognosis for individuals with DAVFs varies. With appropriate treatment, many patients can expect a good outcome and resolution of symptoms. However, untreated DAVFs can lead to serious complications, including stroke, brain damage, and death.

See Also

• Arteriovenous malformation
• Cerebral angiography
• Intracranial pressure
• Stroke