Dural Arteriovenous Fistula (DAVF) — Symptoms, Diagnosis, Risk and Treatment

Most readers benefit from reviewing the Quick Summary together with the sections on Symptoms, Venous Drainage and Risk, and Treatment Options. Other sections provide deeper clinical context and decision-making insight.

What Is a Dural Arteriovenous Fistula

Dural arteriovenous fistula (DAVF) is an abnormal direct connection between arteries and veins located in the dura mater (the outer covering of the brain). In many DAVFs, the abnormal connection is not a single channel but a network of small arterial feeders within the dura that converge into a venous sinus or vein. Because blood flows directly from arteries into veins (especially the venous sinus), pressure rises in the venous system. This can make it harder for blood to drain normally from the brain, leading to a “back-up” of blood, and may result in brain swelling, reduced blood flow (ischemia), or bleeding.

DAVFs can occur:

• in the brain (cranial DAVF)
• along the spine (spinal DAVF)

Cranial DAVFs are more common than spinal ones and their clinical significance depends entirely on which dural venous sinus is involved. These sinuses are the „main highways“ for blood leaving the brain, and the location of the abnormal arterial shunt determines how that blood pressure is redistributed. The most frequent site is the transverse–sigmoid sinus region, accounting for approximately 60–65% of all cases. These sinuses are located at the back and sides of the head (the occipital and region behind the ear), where the brain’s drainage system is most robust. Another common location is the cavernous sinus, situated behind the eyes (orbits), which surrounds the internal carotid artery and several cranial nerves. Less frequent but clinically critical sites include the tentorial sinus, located within the dural fold separating the cerebrum from the cerebellum, and the anterior fossa (ethmoidal region) at the very front of the skull base above the nose. Finally, fistulas can occur in the superior sagittal sinus, which runs along the top of the head from front to back. Identifying the specific location is the first step in diagnosis, as each site has a different anatomical relationship to the brain’s surface veins and determines the potential for dangerous venous reflux.

Image: Cranial DAVFs are most commonly located in the transverse–sigmoid sinus region (approximately60-65% of cases), followed by the cavernous sinus (around 20–30%), while other locations such as the tentorium, superior sagittal sinus, and anterior cranial fossa are less common (each typically around 5–10%).

The exact cause of DAVFs is not fully understood. They are considered acquired lesions, most commonly developing in adults in their 40s–60s, and are rare in children. Venous sinus thrombosis and prior trauma are frequently implicated as potential triggers, likely leading to venous hypertension and the formation of abnormal arteriovenous shunts within the dura.

This page focuses primarily on cranial DAVFs, with a separate section on spinal DAVFs below.

Image: Most common DAVF location between the dural artery and the dural venous sinus (transverse sinus)

Pathophysiology — Venous Hypertension and Congestion in DAVF

The key problem in dural arteriovenous fistulas is not the arterial inflow itself, but impaired venous drainage.

Arterial blood is shunted directly into the venous system and may lead to:

• increased venous pressure — direct inflow of arterial blood raises pressure in the veins
• reduced normal venous outflow — higher venous pressure makes it harder for blood to drain normally
• chronic venous congestion — persistent back-up of blood in the veins over time, leading to impaired circulation

This results in venous hypertension, which is the central mechanism of symptoms and complications. If the blood flow through the fistula is low—particularly in cases where the shunt involves a dural vein rather than a major venous sinus—these venous drainage disturbances may not develop. Such fistulas often remain stable over time without further progression or clinical worsening.

In cranial DAVFs, if venous drainage disturbances appear:

• abnormal venous drainage may reverse into cortical veins — a phenomenon known as cortical venous reflux
• elevated venous pressure leads to dilation and weakening of cortical veins, making them prone to rupture and intracranial hemorrhage (intracerebral, subdural or subarachnoid)
• Impaired venous outflow may reduce normal drainage of blood from the brain, resulting in a back-up of blood in the veins (venous congestion), which can lead to swelling (edema) and reduced oxygen supply to brain tissue (ischemic changes).

In spinal DAVFs if venous drainage disturbances appear:

• Venous congestion affects the spinal cord — impaired venous drainage leads to a build-up of blood in the spinal veins, increasing pressure and making it harder for the spinal cord to receive normal blood flow.
• Leads to chronic ischemia and progressive neurological decline — over time, reduced oxygen supply damages the spinal cord, resulting in gradually worsening symptoms such as leg weakness, difficulty walking, sensory loss, and bladder or bowel dysfunction.

Symptoms of DAVF

If there is no disturbance in the brain’s venous drainage, many dural AV fistulas remain asymptomatic and may be discovered incidentally on imaging. In such cases, they can often simply be monitored over time.

Common symptoms include:

• pulsatile tinnitus — a rhythmic “whooshing” sound caused by turbulent blood flow, most often in transverse or sigmoid sinus fistulas (the occipital and region behind the ear), transmitted through adjacent bone structures
• headache — related to venous hypertension and impaired cerebral venous drainage
• visual disturbances — particularly in cavernous sinus fistulas, due to orbital venous congestion
• seizures — may occur as a result of cortical irritation caused by venous congestion or ischemia
• cognitive changes — including slowed thinking or confusion, often due to chronic venous congestion
• neurological deficits — such as weakness or speech problems, typically caused by venous ischemia or intracranial hemorrhage
• intracranial hemorrhage — may present suddenly with severe symptoms, especially in high-risk fistulas with cortical venous reflux

Pulsatile Tinnitus — Hearing Blood Flow in AV Fistula

Pulsatile tinnitus is one of the most common and characteristic symptoms.

Patients typically describe:

• a rhythmic “whooshing” sound
• synchronized with the heartbeat
• often louder at night or in quiet environments

This symptom is most commonly associated with fistulas located in the transverse sinus (occipital region) and the sigmoid sinus (mastoid region, behind the ear).

It occurs because turbulent blood flow is transmitted to nearby structures and becomes audible.

Headache or Seizures and DAVF — When Is It the Cause?

Headache or seizures without a clear cause on MRI should raise suspicion for a dural arteriovenous fistula (DAVF), especially when symptoms are atypical, progressive, or associated with pulsatile tinnitus or fluctuating neurological findings. Small or complex DAVFs may not be visible on standard imaging and may require more detailed studies such as MRA, CTA, or DSA.

On the other hand, if a DAVF is incidentally detected in a patient with headache or seizures, it must be confirmed that it is truly the cause of symptoms. In headache, this is often not straightforward, as headache is very common and frequently related to primary disorders such as migraine or tension-type headache. A DAVF is more likely to be relevant if there are associated features such as pulsatile tinnitus, atypical or progressive symptoms, or signs of venous hypertension on imaging.

In patients with seizures, it is important to determine whether the DAVF is actually responsible for cortical irritation, venous congestion, or ischemic changes that could trigger epilepsy. This requires correlation between imaging findings (especially cortical venous reflux, edema, ischemic changes, or hemorrhagic lesions), the anatomical location of the DAVF, the clinical seizure pattern, and EEG findings. A DAVF is more likely to be epileptogenic when the vascular lesion and its secondary brain changes involve the same cortical region from which seizures appear to arise. Not all detected DAVFs are epileptogenic, and some may represent incidental findings.

When Is a Dural AV Fistula Dangerous

The risk of complications depends primarily on the pattern of venous drainage.

Low-risk DAVFs:

• drain into dural venous sinuses
• do not involve cortical veins

High-risk DAVFs:

• show cortical venous reflux, where arterial blood flows retrogradely into cortical veins instead of normal venous drainage
• this leads to arterialization of cortical veins, with increased flow and pressure within the venous system
• progressive venous hypertension causes dilation and weakening of vein walls, making them prone to rupture
• as a result, there is a significantly increased risk of intracranial hemorrhage and neurological deterioration

This classification is commonly described using systems such as Borden or Cognard, but the key clinical concept is simple: The presence of abnormal cortical venous drainage determines the risk. In higher-grade DAVFs with cortical venous reflux, the annual risk of hemorrhage is about 8%, and the annual risk of new neurological deficits is about 7%.

Symptoms of the Most Common Cranial DAVF Locations

Transverse and Sigmoid Sinus DAVF

These are the most common locations, with the fistula typically situated at the junction of the transverse and sigmoid sinuses.

Typical features:

• pulsatile tinnitus — the most common presentation, often unilateral and synchronous with the heartbeat
• audible bruit in the occipital region, sometimes detectable on examination
• symptoms may initially be limited to tinnitus, especially in low-risk fistulas without cortical venous reflux

However, in more advanced or high-risk cases:

• neurological deficits may occur due to impaired venous drainage (venous congestion — build-up of blood in the veins), leading to reduced blood flow (ischemia) and resulting in focal deficits such as visual disturbances and cognitive changes
• seizures can develop as a result of cortical venous hypertension
• intracranial hemorrhage may occur, particularly when cortical venous reflux is present

Cavernous Sinus (Carotid–Cavernous Fistula)

These fistulas have a distinct clinical presentation due to their effect on the orbit and cranial nerves. They are most commonly caused by trauma.

Typical features:

• red eye due to venous congestion
• protrusion of the eye (proptosis)
• double vision (diplopia) caused by cranial nerve dysfunction
• pulsatile noise, sometimes perceived by the patient

These symptoms result from venous congestion in the cavernous sinus and orbital veins.

Important considerations:

Cavernous sinus fistulas may be dural (indirect) or direct high-flow fistulas

• indirect (dural) fistulas are often less aggressive and may present mainly with ocular symptoms
• direct fistulas, typically involving the internal carotid artery within the cavernous sinus, represent a high-flow lesion and may lead to rapid symptom progression

The severity depends primarily on venous drainage patterns and flow dynamics, rather than location alone

Diagnosis — MRI, MRA, CTA and Angiography

MRI and MRA (MR angiography) as well as CTA (CT angiography) may suggest the diagnosis.

Findings may include:

• dilated veins — enlarged veins due to increased pressure and abnormal blood flow
• signs of venous congestion — impaired venous drainage with build-up of blood in the veins
• brain edema — swelling of brain tissue caused by venous hypertension and reduced circulation

In spinal DAVF:

• spinal cord edema — swelling of the spinal cord due to chronic venous congestion
• serpiginous flow voids — tortuous, abnormal vessels around the spinal cord seen as dark, snake-like structures on MRI

However, the gold standard is:

Digital Subtraction Angiography (DSA)

This is the gold standard. DSA is a minimally invasive imaging technique performed under local anesthesia, often with light conscious sedation to ensure the patient is comfortable and relaxed. A neuro-radiologist inserts a thin catheter, typically through a puncture in the femoral artery (in the groin) or the radial artery (in the wrist). The catheter is then carefully navigated through the major blood vessels up to the arteries supplying the brain. Once positioned, a contrast agent is injected. This substance allows high-resolution, real-time X-ray images to visualize the blood flow, which clearly outlines the arteries and identifies DAVFs, and other vascular pathologies such as AVMs and aneurysms.

This allows:

• precise identification of the fistula
• evaluation of venous drainage
• assessment of hemorrhage risk

Treatment Options for DAVF

Treatment depends on symptoms and venous drainage pattern.

Options include:

• observation (in low-risk cases)- Approximately 20–40% of DAVFs, typically those without cortical venous reflux, may be managed conservatively with observation and regular follow-up.
• endovascular treatment
• microsurgical disconnection
• radiosurgery

In more complex cases, a combination of therapeutic methods is used.

Treatment is generally recommended:

• if the fistula has caused hemorrhage
• if cortical venous reflux is present
• if symptoms are progressive

In contrast:

• asymptomatic DAVFs without cortical venous reflux may be managed conservatively, with regular clinical and imaging follow-up
• these lesions are generally considered low-risk, although a small proportion may change over time and therefore require reassessment

Endovascular treatment is the most commonly used approach and is successful in approximately 70–90% of cases, depending on location and anatomy. This procedure involves navigating microcatheters through the blood vessels to reach the site of the fistula and closing the abnormal connection.

The goal is not only to eliminate the abnormal arteriovenous shunt, but to disconnect the pathological venous drainage.

This can be done:

• transarterial approach — by injecting liquid embolic agents (Onyx or glue) to penetrate and seal the fistulous connection, ideally reaching the venous side
• transvenous approach — treatment is performed from the venous side by targeting the venous end of the fistula, including the fistulous point, draining vein, or the involved venous sinus. This may involve selective occlusion of the fistula or complete occlusion of the affected sinus segment. In advanced DAVFs (especially transverse–sigmoid) the sinus is often already functionally excluded from normal drainage, so sinus occlusion is commonly performed, in a substantial proportion of high-grade cases (approximately 50–70%).
• combined approach — where both arterial and venous routes are used in the same procedure or in staged treatments, particularly in complex fistulas with multiple feeders or difficult anatomy

Whenever possible, normal venous drainage is preserved, but in many high-grade DAVFs the involved sinus can be safely sacrificed because it no longer serves normal cerebral venous outflow.

Image: Schematic illustration of an occipital dAVF and its management via combined transarterial and transvenous endovascular occlusion.

In cases where a fistula has caused intracranial hemorrhage, emergency surgery may be required to remove the hematoma and relieve pressure on the brain. During the same procedure, an attempt may be made to identify and disconnect the fistula, particularly if it is surgically accessible. However, this is not always possible. If the fistula cannot be definitively treated during surgery, it is subsequently managed using endovascular techniques.

Definitive treatment requires closure of the arteriovenous shunt itself. This is most commonly achieved through endovascular embolization, but in some cases microsurgical treatment is used as a primary approach, particularly when endovascular access is not feasible or is unlikely to be effective, such as in anterior cranial fossa DAVFs.

The choice between endovascular and surgical treatment is made by a multidisciplinary team, typically including neurosurgeons and interventional neuroradiologists, based on the location of the fistula, venous drainage pattern, and overall risk profile, in order to prevent further bleeding or neurological deterioration.

Spinal Dural Arteriovenous Fistula — A Frequently Missed Cause of Progressive Leg Weakness

Spinal DAVF is a separate but related condition.

It is caused by abnormal shunting in the dura surrounding spinal nerve roots, leading to venous congestion of the spinal cord.

Typical features:

• progressive weakness
  • thoracic lesions — weakness of the legs (paraparesis), often with gradual deterioration of walking ability
  • cervical lesions — weakness may involve both arms and legs (quadriparesis), sometimes with hand clumsiness
• difficulty walking — typically due to progressive myelopathy and spasticity
• sensory disturbances
  • thoracic lesions — sensory level on the trunk and lower limbs
  • cervical lesions — involvement of upper limbs, often with numbness or loss of fine sensation in the hands
• worsening with physical activity — symptoms may fluctuate or worsen due to increased venous congestion

This condition is often misdiagnosed as:

• spinal stenosis
• peripheral neuropathy

Delayed diagnosis can lead to permanent deficits. Spinal DAVFs are treated by either endovascular embolization or, more definitively, by surgical disconnection of the fistulous draining vein to eliminate the abnormal shunt and relieve venous hypertension.

Prognosis After Treatment

Outcome depends on:

• early diagnosis — recognizing the condition before significant damage occurs
• prompt treatment after diagnosis — starting treatment without delay to prevent progression
• type of venous drainage — especially the presence of cortical venous reflux, which increases risk

Cranial DAVF:

• good outcome when treated early
• higher risk if cortical venous reflux is present
• pulsatile tinnitus often improves or resolves after treatment
• neurological deficits or seizures may improve if caused by venous congestion and edema
• recovery is less complete if prolonged venous hypertension has led to ischemic brain damage

Spinal DAVF:

• improvement possible if treated early
• delayed diagnosis may lead to irreversible ischemic damages

Why Specialist Opinions May Differ in DAVF

Interpretation of Venous Drainage and Cortical Venous Reflux

The presence or absence of cortical venous reflux often determines whether observation is safe or treatment is required. Specialist recommendations for Dural Arteriovenous Fistula may differ even when based on the same imaging findings. This does not necessarily indicate error, but rather reflects the complexity of the condition. One of the most important sources of disagreement is the interpretation of venous drainage patterns, especially regarding the presence and clinical significance of cortical venous reflux, which directly determines the risk of hemorrhage and neurological deterioration.

Variation in Perceived Risk and Timing of Treatment

Variation in perceived risk is another key factor. Some specialists may recommend earlier intervention, while others may favor observation in borderline cases, particularly when imaging findings are not clearly high-risk. These differences arise from how each specialist weighs the risk of hemorrhage or neurological deterioration against the risks associated with treatment.

Differences in Treatment Experience and Strategy

Recommendations may also differ based on treatment experience. Centers with strong endovascular expertise may prefer embolization, while others may recommend surgery in selected cases. These differences often reflect familiarity with specific techniques and expected outcomes in different anatomical situations.

Anatomical Complexity of DAVF

DAVFs often show anatomical complexity, including multiple arterial feeders, partial thrombosis, or unusual venous pathways, which can influence decision-making and the feasibility of different treatment approaches.

Patient-Specific Factors

Patient-specific factors such as age, symptoms, comorbidities, and tolerance of procedural risk also play an important role in determining the most appropriate management strategy.

Why Different Recommendations Are Often Reasonable

In practice, these differences often represent reasonable clinical judgment rather than conflicting standards.

For this reason, obtaining a second opinion can be particularly valuable when the diagnosis is uncertain, when treatment options differ, or when the risks and benefits are not clearly understood.

Frequently Asked Questions About Dural Arteriovenous Fistula (DAVF)