Definition

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.

Causes

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.

Risks

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 five times more men experience DAVF than women. Surgery, injury, infection or dural sinus thrombosis can lead to DAVF so these patients should be monitored.

Symptoms

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

Diagnosis

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

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

Prevention

DAVF cannot be prevented but patients who are at risk because of infection, injury or surgery should be monitored or treated. For those at risk for dural sinus thrombosis anticoagulation therapy may be indicated.

Case Study

A 74 year old man was transferred from an outside hospital to MSMC 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 angiogram with embolization with Dr. Aman Patel. Dr. Joshua Bederson performed a craniotomy to remove the DAVF. He 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.

If you want to learn more about Dural Arteriovenous Fistulas call the Mount Sinai Department of Neurosurgery at 212-241-2377.

Images used with permission from Aman Patel, MD.