A dural arteriovenous fistula (DAVF) is an abnormal direct connection between arteries and veins within the tough membrane that covers the brain or spinal cord. Unlike arteriovenous malformations, which are tangled knots of vessels embedded in brain tissue, DAVFs sit in the dural membrane itself and draw their blood supply from arteries that feed that membrane.1PubMed. Intracranial dural arteriovenous fistula: a comprehensive review of the history, management, and future prospective Most are acquired rather than present from birth, and their behavior ranges from a harmless nuisance producing a rhythmic whooshing sound in your ear to a dangerous lesion that can cause brain hemorrhage or progressive dementia.
What Causes a Dural Arteriovenous Fistula
The majority of DAVFs develop in adulthood, and the strongest known trigger is cerebral venous thrombosis, a blood clot forming inside one of the brain’s venous sinuses. When a sinus clots, normal blood drainage from the brain is disrupted, and the body responds by recruiting new tiny arterial channels through the dura to reroute blood flow. Over time, some of these channels enlarge into a fistula. A study of 55 patients found that about 60% of those with both a DAVF and venous thrombosis had the clot present at the time the fistula was diagnosed, while 7% had thrombosis before the fistula appeared and a third developed clotting during follow-up. In the vast majority of cases, the clot sat in the same sinus as the fistula or in one right next to it.2American Journal of Neuroradiology. Association between Dural AVFs and Cerebral Venous Thrombosis
Other conditions linked to DAVF formation include prior surgery near the skull base, head trauma, ear infections, and anything that raises pressure inside the venous sinuses. Pregnancy and conditions that make blood more likely to clot can also contribute. That said, many patients have no clear precipitating event, and the fistula is discovered incidentally or after symptoms gradually emerge. Research into whether anticoagulant therapy after venous thrombosis prevents fistula formation has so far turned up very low rates of new DAVF development regardless of the blood thinner used, suggesting these lesions remain uncommon even in high-risk populations.3PubMed. Dural Arteriovenous Fistulae After Cerebral Venous Thrombosis
How Symptoms Show Up
The symptoms of a DAVF depend almost entirely on where the fistula is and, more importantly, how the blood drains out of it. Many people with low-risk fistulas notice only one thing: pulsatile tinnitus, a rhythmic whooshing or buzzing in the ear that beats in time with the pulse. The transverse-sigmoid sinus junction, which sits just behind the ear, is the most common fistula location to produce this symptom.4PubMed Central. Pulsatile tinnitus with a dural arterio-venous fistula diagnosed by computed tomography-angiography While pulsatile tinnitus has many possible causes, a DAVF is one of the few that is both identifiable on imaging and treatable.
Fistulas located near the cavernous sinus, the venous chamber behind each eye, tend to produce eye-related problems. These can include a bulging eye, swollen and red conjunctiva, double vision, and rising pressure inside the eye that mimics glaucoma. One reported case involved a 66-year-old woman with headache, orbital swelling, and a protruding eye, all caused by an indirect fistula draining into the cavernous sinus.5PubMed Central. Home-Based Therapy Utilizing Intermittent Manual Compression of the Carotid Artery and Internal Jugular Vein in the Management of Carotid-Cavernous Fistula If the pressure stays elevated long enough, vision loss can become permanent, which makes early recognition important.
Perhaps the most insidious presentation is cognitive decline. When a DAVF causes blood to back up into the brain’s deep venous system, it can produce widespread venous congestion that looks, on examination and imaging, a lot like Alzheimer’s disease or another progressive dementia. Two patients described in the literature presented with dementia as their primary symptom. After the fistula was closed with an endovascular procedure, their cognitive function returned to baseline.6PubMed Central. Dementia caused by dural arteriovenous fistulas reversed following endovascular therapy This is one of the rare genuinely reversible causes of dementia, which makes it worth thinking about whenever someone’s cognitive decline follows an unusual pattern or progresses unusually fast.
Why Venous Drainage Determines the Danger
The single most important factor in predicting how a DAVF will behave is the pattern of venous drainage. The classification systems used by neuroradiologists all revolve around one question: does the fistula drain into a normal dural venous sinus, or does it push blood backward into cortical veins that sit on the brain’s surface? The drainage pattern seen on vascular imaging correlates directly with symptom severity and the risk of hemorrhage.7PubMed Central. Intracranial dural arteriovenous fistulas: classification, imaging findings, and treatment
Low-grade fistulas drain into a sinus the way blood is supposed to flow. These tend to cause only benign symptoms like pulsatile tinnitus or mild headache, and many never progress. High-grade fistulas redirect blood into cortical veins, which are thin-walled vessels not designed to handle arterial pressure. That reflux raises the risk of hemorrhage, seizures, and the progressive neurological decline described above. Among patients with high-grade fistulas, those who had the worst symptoms also had the most compromised drainage: a single draining direction, narrowing of the draining vein, no alternative route for normal brain blood to exit, and stagnation of blood visible on angiography.8Journal of Neurosurgery. Cerebral venous drainage in patients with dural arteriovenous fistulas: correlation with clinical presentation
This is why two people with the same diagnosis can have wildly different experiences. One person’s DAVF may be nothing more than an annoying sound in the ear, while another’s is a ticking clock that requires urgent treatment. The drainage pattern, not the fistula’s size or location alone, is what determines which camp you fall into.
How DAVFs Are Diagnosed
Catheter-based digital subtraction angiography (DSA) remains the gold standard for diagnosing intracranial DAVFs. It involves threading a catheter through an artery in the groin up to the head and injecting contrast dye while taking rapid X-ray images. The result is a real-time movie of blood flow through every arterial feeder, the fistula itself, and the venous drainage, which is the information doctors need to plan treatment.
Magnetic resonance angiography (MRA) is less invasive and increasingly used as a screening tool. For spinal DAVFs, a meta-analysis found that MRA actually had higher sensitivity than DSA for detecting the fistula, picking it up in about 98% of cases compared with 86% for DSA. However, DSA provided better overall accuracy for pinpointing the exact vertebral level of the fistula, information that is essential for surgical planning.9PubMed. Evaluating the diagnostic accuracy of magnetic resonance angiography versus digital subtraction angiography for spinal dural arteriovenous fistulas: a systematic review and meta-analysis In practice, MRA is often used first to confirm suspicion and localize the general area, with DSA following for detailed treatment mapping.
CT angiography also plays a role, particularly for detecting DAVFs behind the ear that present as pulsatile tinnitus, where it can catch the abnormal vessels feeding into the sigmoid sinus. Standard MRI of the brain can raise suspicion when it shows dilated veins or unexplained swelling in brain tissue, but it cannot define the fistula’s feeding arteries or drainage well enough to guide treatment.
Endovascular Embolization
The primary treatment for most DAVFs is endovascular embolization, a catheter-based procedure in which a liquid or glue-like substance is injected directly into the fistula to block it. The interventionalist navigates a microcatheter through the arterial feeders or, in some cases, through the venous side, and delivers an embolic agent that hardens inside the abnormal connection and shuts it down.
The most widely used embolic material for years has been Onyx, a copolymer that solidifies on contact with blood. In one series of 25 patients, complete closure of the fistula was achieved in a single session in 84% of cases, with only one recurrence at one-year follow-up.10PubMed Central. Embolization of cranial dural arteriovenous fistulae with ONYX: Indications, techniques, and outcomes Onyx has a long track record, but it creates imaging artifacts on CT and MRI afterward, and during long injections its visibility under X-ray can temporarily diminish. Newer agents called Squid and PHIL were developed to address these drawbacks.11PubMed Central. Glue, Onyx, Squid or PHIL? Liquid Embolic Agents for the Embolization of Cerebral Arteriovenous Malformations and Dural Arteriovenous Fistulas
A systematic review and meta-analysis of these newer agents found complete occlusion rates of about 91% for DAVFs overall, with Squid achieving roughly 93% and PHIL about 86%. Permanent complication rates from the procedure were around 3% for fistulas, substantially lower than for brain arteriovenous malformations treated with the same materials.12PubMed Central. Safety and efficacy of newer liquid embolic agents Squid and PHIL in endovascular embolization of cerebral arteriovenous malformations and dural arteriovenous fistulas: A systematic review and meta-analysis A multi-institutional study of Onyx embolization reported major cerebral complications in about 4% of patients.13Journal of NeuroInterventional Surgery. Onyx embolization for dural arteriovenous fistulas: a multi-institutional study These are not trivial numbers, and they underline why low-grade fistulas producing only minor symptoms are sometimes watched rather than treated.
Radiosurgery and Open Surgery
When endovascular embolization cannot fully close a fistula or when the anatomy makes catheter access difficult, two other options come into play. Stereotactic radiosurgery (SRS), most commonly Gamma Knife, delivers a focused beam of radiation to the fistula site. It does not work immediately: the radiation gradually causes the abnormal vessels to scar and close over months to years. A meta-analysis of over 700 treated fistulas found a complete obliteration rate of about 69%, with symptom improvement in roughly 97% of patients. The risk of hemorrhage after the procedure was low, around 1%, and permanent neurological complications occurred at a similar rate.14PubMed. Stereotactic Radiosurgery for Dural Arteriovenous Fistulas: A Systematic Review and Meta-Analysis and International Stereotactic Radiosurgery Society Practice Guidelines
The obliteration rate climbs with time. One study reported that while only about half of fistulas were closed at three years, the rate reached 80% by five years. Fistulas without cortical venous drainage responded much better, with an 86% obliteration rate, compared to 47% for those with cortical drainage.15Journal of neurosurgery. Role of Gamma Knife surgery in the treatment of intracranial dural arteriovenous fistulas The delay in closure is the main limitation: for aggressive, high-grade fistulas that are hemorrhaging or causing rapid neurological decline, waiting years for radiosurgery to take effect is not safe. These cases typically need embolization or surgery first, with radiosurgery reserved as a follow-up to mop up any residual fistula.
Open microsurgery involves a craniotomy and direct disconnection of the abnormal draining veins from the fistula. It tends to be highly effective when it can be performed, and carries no latency period. Surgery is generally reserved for cases where endovascular treatment has failed or is not technically feasible.16PubMed Central. Surgical Treatment of Dural Arteriovenous Fistula: A Case Report and Literature Review In practice, most centers use a combination approach: attempt embolization first, add surgery or radiosurgery if the fistula persists.
Spinal Dural Arteriovenous Fistulas
Not all DAVFs sit inside the skull. Spinal DAVFs are a distinct entity that forms along the nerve roots of the spinal canal, typically in the lower thoracic or lumbar region. Instead of causing tinnitus or eye problems, they produce a slowly worsening syndrome of leg weakness, numbness, difficulty walking, and problems with bladder and bowel control.17PubMed Central. Myelopathy caused by spinal dural arterio-venous fistula after first lumbar vertebral body fracture – a case report The mechanism is venous congestion: arterialized blood flows backward through the spinal veins and raises pressure around the spinal cord, gradually damaging it.
The biggest problem with spinal DAVFs is misdiagnosis. Their slow progression and the overlap of their symptoms with far more common conditions like spinal stenosis, disc disease, and peripheral neuropathy means the fistula is often not suspected until significant damage has accumulated.18Cerebrovascular Neurosurgery. Spinal Dural Arteriovenous Fistula Presenting with Myelopathy Diagnostic delays of a year or more are common, and by the time treatment occurs, some of the spinal cord injury may be irreversible. If you or someone you know has progressive leg weakness and bladder problems without a clear spinal structural cause, a spinal DAVF is worth raising with the medical team.
Treatment for spinal DAVFs mirrors the intracranial approach: endovascular embolization or surgical disconnection. Both are effective, though surgical ligation has historically had slightly higher long-term cure rates for spinal lesions.
Can a DAVF Close on Its Own
A small number of DAVFs do resolve without any treatment. A systematic review identified several factors that promote spontaneous closure, including stasis of blood flow within the fistula, damage to the lining of the vessel walls, and the presence of thrombosis in the draining sinus.19Journal of Medical Imaging and Interventional Radiology. Predictive factors for spontaneous resolution of dural arteriovenous fistulas: a systematic review In some cases, the same process that created the fistula, progressive venous clotting, ends up shutting it down. Manual compression of the carotid artery and jugular vein has even been used to encourage this process in select cavernous sinus fistulas, avoiding the need for an invasive procedure.5PubMed Central. Home-Based Therapy Utilizing Intermittent Manual Compression of the Carotid Artery and Internal Jugular Vein in the Management of Carotid-Cavernous Fistula
Spontaneous resolution is most likely in low-grade fistulas that drain only into a venous sinus and have no cortical venous reflux. It is unpredictable and cannot be relied upon for high-grade fistulas, where the risk of hemorrhage or neurological deterioration while waiting is too high. Conservative follow-up with serial imaging is a reasonable strategy for some benign fistulas, but it requires close monitoring to ensure the drainage pattern does not change over time.
Pediatric DAVFs
DAVFs in children are rare and behave differently from the adult form. A study of 43 pediatric patients found that roughly equal numbers had adult-type fistulas and infantile-type fistulas, with the infantile form requiring more rounds of treatment, achieving lower cure rates, and carrying a worse prognosis.20Stroke and Vascular Neurology. Paediatric intracranial dural arteriovenous fistulas: clinical characteristics, treatment outcomes and prognosis About two-thirds of patients in that series achieved complete fistula closure by the end of treatment, and the overall complication rate from endovascular procedures was around 9%. Infantile-type DAVFs can present with heart failure in newborns because the high-flow fistula diverts so much blood that the heart struggles to keep up, a dramatically different presentation from the tinnitus and eye symptoms seen in adults.
Life After Treatment
Closing a DAVF resolves the immediate vascular problem, but recovery is not always complete, especially for spinal fistulas. A quality-of-life study of patients treated for spinal DAVFs found that their scores on a standardized health questionnaire were significantly lower than the general population across every measured category. Physical functioning and the ability to carry out daily roles were particularly affected. Persistent walking difficulty, bladder problems, and chronic pain all contributed to reduced quality of life even after the fistula itself had been successfully treated.21PubMed. Health-related quality of life in patients with spinal dural arteriovenous fistulae
The prognosis depends heavily on how much damage accumulated before treatment. For intracranial DAVFs that caused only pulsatile tinnitus or mild eye symptoms, closing the fistula typically resolves the complaint. For those that caused cognitive decline, the reversibility is often remarkable, as the case reports of dementia resolving after embolization illustrate. But for spinal fistulas that caused cord damage, or intracranial fistulas that bled, the deficits present at the time of treatment tend to improve only partially. This is one of the strongest arguments for early diagnosis: the damage a DAVF causes is progressive, and earlier treatment preserves more function. Rehabilitation after treatment, particularly physical therapy for gait impairment and occupational therapy for any cognitive deficits, plays an important role in maximizing recovery.