The brain and spinal cord are surrounded by three protective layers called meninges. The outermost layer, the dura, is the strongest of the three. It is a double membrane with large channels that house a network of arteries and veins to manage blood flow. A dural arteriovenous fistula (DAVF) is an abnormal connection (fistula) between arteries and veins within the dura where blood often bypasses the capillaries that support local tissue. DAVF can occur in the brain (cranial DAVF) or the spinal cord (spinal DAVF), though cranial DAVF is much more common. They are grouped into three types based upon their venous drainage. The treatment modality depends on the anatomy and drainage of the DAVF.

DAVF is generally accepted to be an acquired condition with several common causes:

• dural sinus thrombosis (blocked dural sinuses)
• head injury
• infection
• open surgery

There is some evidence to suggest that cranial DAVFs are formed by increased release of angiogenic factors or by increased hypertension due to dural sinus thrombosis.

Risk factors are things associated with an increased chance of developing a disease or condition. There are no known congenital risks for developing DAVF. Age may be a factor and men experience DAVF five times more than women. Surgery, injury, infection or dural sinus thrombosis can lead to DAVF so these patients should be monitored.

Symptoms of DAVF vary depending on the location of the fistula:

Cranial DAVF

• Headache
• Proptosis (bulging of the eye)
• Glaucoma
• Tinnitus (whooshing or ringing sound in the ear)
• Cranial nerve dysfunction
• Seizure
• Hemorrhage
• Stroke-like symptoms
• Neurological decline

Spinal DAVF:

• Loss of limb sensation and/or function (can be sudden or progressive)
• Progressive bowel and/or bladder dysfunction
• Erectile dysfunction

Imaging is critical to the diagnosis of DAVF to properly locate and characterize it. Tests include:

Cranial:

• Cerebral angiography
• MR angiography
• MR venography

Spinal:

• Selective spinal angiography
• Spinal MRI
• · Contrast-bolus MR angiography

Treatment is dependent on the location of the vessels involved, the severity of symptoms, and the risk of hemorrhage.

• Observation (in low-risk cases)
• Endovascular embolization
• Gamma Knife surgery or radiation therapy
• Open surgery

Case Study

A 74-year-old man was transferred from an outside hospital to the Mount Sinai Medical Center with a large subarachnoid hemorrhage secondary to a ruptured DAVF of the anterior cranial fossa. He was allowed to recover for a few days and then underwent an angiogram with embolization with Dr. Aman Patel. Dr. Joshua Bederson performed a craniotomy to remove the DAVF. The patient had a very prolonged and difficult postoperative course, due to the effects of the initial bleed, and his ability to recover was uncertain. He was ultimately discharged to a nursing home.

At the nursing home, he made marked strides towards recovery. Almost a year after the bleed he was discharged and went to live with one of his children. He was functioning independently, caring for his grandchildren and beginning to resume most his normal activities. Other than some short-term memory loss, both he and his family believed that he had regained most of his preoperative cognitive functions. At his last visit he was planning a trip to his home country to spend the winter.