Arteriovenous Fistula (AVF)Procedures
What is an AVF?
A dural AVF is an abnormal connection between arteries and veins within the tissue that lines the space of the brain (the dura). There are many hypotheses as to why these occur, but it is most typically thought to result from an abnormal response by the body to a clot that forms in a vein. Once the arteries form a fistula with a vein or veins, blood gets immediately shunted from the high pressure arterial system into the low pressure venous system. There is a spectrum of severity, ranging from the shunted blood flowing in a physiologic venous pattern, to reversal of the normal blood flow with pressurization of the fine veins of the brain. The latter is a worrisome development as it places patients at a significant risk of having a brain bleed.
What are the symptoms of an AVF?
While these lesions may be entirely asymptomatic, the most characteristic presentation is pulsatile tinnitus - a rhythmic whooshing sound from the turbulent blood flow of the fistula that propagates through the bone of the skull. A wide variety of additional symptoms may be seen depending on the location of the fistula and the brain structures affected.
How is a dural AVF diagnosed?
The diagnosis of a dural AVF is often suggested on a CT or MRI scan of the blood vessels of the brain. This is then further confirmed with a diagnostic cerebral angiogram, which demonstrates the dynamic blood flood of the fistula and its fine anatomic detail.
How is a dural AVF treated?
The current gold standard for treatment of dural AVFs is endovascular embolization. There are a number of different endovascular devices, techniques and materials that can be applied to best treat a given lesion depending on its specific configuration. A dural AVF may be treated through the artery, through the vein, or even both. Once access to the fistula is obtained, it is closed with coils and/or a glue-like substance called Onyx, eliminating the abnormal communication.