Dural Arteriovenous Fistulas

Dural arteriovenous fistulae (DAVF) are rare, abnormal connections between arteries and veins in a protective membrane on the outer layer of the brain and spine, called the dura. These abnormal blood vessels divert blood from the normal paths. If the volume of diverted blood flow is large, tissue downstream may not receive an adequate blood and oxygen supply. An unusually heavy blood flow also can lead to aneurysms or ruptures in the veins. This condition can be caused by head trauma, infection, surgery or blood clots in the brain, called thrombosis, or may be a congenital or birth defect.

Dural arteriovenous fistula (DAVF) are a heterogeneous collection of conditions that share arteriovenous shunts from dural vessels. They make up 10-15% of all cerebral vascular malformations. They typically have multiple feeders and are usually acquired. Idiopathic origin, trauma, and previous craniotomy are possible etiopathogenic explanations, however they most frequently occur as a result of neovascularisation induced by previously thrombosed dural venous sinus (typically transverse sinus).

Symptoms:

The symptoms of DAVFs vary depending on the location of DAVF. Headache is one of the non-specific symptoms that could be associated with all types of DAVFs. Although DAVFs can occur in any part of the location where the dura mater exists, DAVFs are commonly found in cavernous sinus (behind the eye) and transverse / sigmoid sinus (behind the ear, back of your head). Patients with DAVFs behind the eye (cavernous DAVFs) usually complain of decreased vision and redness / congestion / swelling of the eye. Patients with DAVFs behind the ear (transverse / sigmoid DAVFs) frequently hear a pulsating noise (tinnitus) due to the fast blood flow going through the fistulas. All types of DAVFs can cause stroke-type symptoms and seizures. Brain hemorrhage is the most serious presentation of DAVFs and can cause permanent disability and death.

Diagnosis:

• Cerebral Angiography — This X-ray exam shows the structure of blood vessels and is the most important test in diagnosing DAVF. A harmless dye, visible on X-rays, is injected into an artery that supplies blood to the brain. As the dye flows through blood vessels to the brain, it will show any obstructions or leaks.
• Computed Tomography (CT) Scan — During this test, X-ray beams are used to create a 3-D image of the brain and may help identify any bleeding or hemorrhage. For more precise images of blood vessels, the cerebral angiography and magnetic resonance angiography (MRA) are performed.