Introduction to DAVF

What is a dural arteriovenous fistula?

A dural arteriovenous fistula (DAVF) is an abnormal connection between the arteries and veins of the brain.

Normally a fine network of microscopic capillaries connects arteries and veins in all tissues including the brain. Capillaries assist in slowing down the blood flow between arteries and veins. A DAVF is a tangle of feeding arteries and draining veins in the brain that have abnormal connections which bypass the normal capillaries. The word “dura” refers to the membrane covering the brain and spinal cord. The high pressure blood flowing from arteries directly into thinner walled draining veins or venous sinuses results in a risk of brain haemorrhage (bleeding). This abnormal blood flow between arteries and veins is called a shunt. DAVF can vary in size, between a few millimetres to several centimetres and can occur anywhere in the dura directly outside of the brain or spinal cord.

The exact cause of a dural arteriovenous fistula (DAVF) is often unknown. In most cases, DAVFs are not inherited but are thought to develop after events such as blood clots in the brain’s large draining veins (venous thrombosis), head injury, brain surgery, or infection.

DAVFs are classified by risk. High-grade fistulas carry a significant chance of bleeding into or around the brain, especially if bleeding has occurred before, and this can have serious consequences. Low-grade fistulas have little or no risk of bleeding.

Some patients have no symptoms, and the DAVF may be found incidentally on a CT or MRI scan. However, even when discovered by chance, further investigation is usually needed to assess potential risk.