Dural arteriovenous fistulas (DAVFs) (see figure) are defined as direct shunts between arteries and venous sinuses or cortical veins with no transitional capillary network contained within the leaflets of the dura mater, the thick layer of the meninges that covers the brain. They are supplied by branches of the carotid and vertebral arteries before they penetrate the dura. This disease is principally an arteriovenous shunt, in which high-pressure arterial blood flows into a low-pressure venous system. Due to chronic high pressure, the veins over time become arterialized but as the veins are not made for high-pressure, they are at risk of bleeding.
DAVFs account for 10-15% of all intracranial vascular lesions, with 61-66% occurring in females. The mean age of presentation is 50 years. They account for 6% of supratentorial and 35% of posterior fossa vascular malformations.
The most common location, accounting for 63% of cases, is adjacent to the transverse sinus, with a slight left-sided predominance. The epicenter of these DAVFs is usually at the junction of the transverse and sigmoid sinuses. Other common locations are in the tentorium and posterior cavernous sinus. A common arterial supply is by the posterior meningeal branch of the vertebral artery. Patient symptoms depend on the location and pattern of venous drainage of the DAVF, the most common symptoms being pulsatile tinnitus, occipital bruit, headache, visual impairment, and papilledema.
The diagnostic test of choice is cerebral angiography. The Borden and Cognard classification systems stratify DAVFs based on severity, with the most significant marker of higher grade being venous drainage over the cortical surface of the brain, placing the patient at risk for bleeding.
Indications for intervention include neurologic dysfunction, hemorrhage, and refractory symptoms. Options for intervention include, surgery to close the arteriovenous shunt, endovascular embolization, and stereotactic radiosurgery.
With cases associated with significant bleeding, surgery is recommended to both close the DAVF and evacuate the bleeding.
The major complication of surgery is rapid blood loss. In the literature, surgery is more likely to offer permanent resolution of the DAVF than embolization.
Figure : Ruptured Dural Arteriovenous fistula (DAVF).
A: Axial non-contrasted CT head showing a left temporal intraparenchymal hematoma
B: Coronal non-contrasted CT head
C: Postoperative imaging after surgical evacuation of hematoma and closure of DAVF