Arteriovenous Fistulas (AVF) & Cavernous Carotid Fistulas (CCF)
An arteriovenous fistula (AVF) in the brain is an abnormal connection between an artery and a vein found in the tissue that covers the brain and spinal cord. Unlike an arteriovenous malformation (AVM)—which patients are born with—an AVF is an acquired lesion, or developed later in life. The two main kinds of AVFs are dural AVFs (dAVF) and carotid-cavernous fistulas (CCF).
Dural Arteriovenous Fistula (dAVF): One of the layers of the membranes that cover the brain is called the dura mater. An abnormal connection between blood vessels that involve this covering is called a dural fistula, which can occur in any part of the brain covering. A dAVF often involves the transverse-sigmoid sinus (behind the ear) and sagittal sinus. Patient reports of hearing a continuous “swooshing” noise that coincides with their heartbeat (called a bruit) are common. Other symptoms include pain behind the ear, headaches and neck pain.
Cavernous Carotid Fistula (CCF): CCFs occur behind the eye and almost always cause visual symptoms due to diversion of blood flow to the eye and consequent increase in eye pressure. Symptoms can include eye swelling, decreased visual acuity, redness of the eye, congestion of the eye, droopy eyelid and pain of the eye. Patients also might report hearing a “swooshing” noise.
There are two categories of CCFs: direct and indirect. A direct CCF has connections between the carotid artery and the veins of the cavernous sinus, usually due to trauma or ruptured aneurysm. An indirect CCF is an abnormal connection in which small arterial branches supply the veins and usually occurs spontaneously. Both types of CCFs threaten vision as well as eye movement, and both can result in major stroke.
Endovascular embolization is used to treat dAVF and CCF. Embolization is a minimally invasive endovascular technique that consists of placing a microcatheter from the femoral artery inside the fistula (abnormal connection) and injecting an embolic agent under x-ray guidance to occlude, or fill, the irregular blood vessels. This treatment re-directs blood flow to the normal, healthy part of the brain and seals off the abnormal connection stealing blood flow. For those patients who experience a “swooshing” noise, the sealing off of this fistula will provide immediate relief from this noise with successful embolization.