Dural Arteriovenous Fistulas: Symptoms, Types, Causes and Treatment

Dural arteriovenous fistulas (DAVFs) are rare but significant vascular abnormalities that can affect both the brain and spinal cord. Their impact on neurological health is often profound, but timely recognition and tailored treatment can dramatically improve outcomes. In this comprehensive article, we explore the symptoms, types, causes, and treatment options for DAVFs, drawing on the latest research for evidence-based guidance.

Symptoms of Dural Arteriovenous Fistulas

Dural arteriovenous fistulas can present with a wide array of symptoms, ranging from subtle sensory disturbances to severe neurological deficits. The clinical picture is influenced by the fistula's location (cranial vs spinal), venous drainage pattern, and the degree of venous hypertension or congestion produced by the abnormal connection. Many symptoms are nonspecific and can mimic other neurological conditions, making early diagnosis a challenge.

Initial	Progressive	Severe	Source
Gait disturbance	Leg weakness	Myelopathy/paralysis	2 4 9
Headache (migraine-like or not)	Sensory loss	Intracranial hemorrhage	5 6 13
Ocular symptoms	Sphincter dysfunction	Cranial nerve palsy	3 5 8
Pulsatile tinnitus	Micturition problems	Seizures, coma	3 8 13

Table 1: Key Symptoms

Common Presentations and Their Nuances

DAVFs can manifest differently depending on their cranial or spinal location:

• Spinal DAVFs most often cause progressive myelopathy. Patients typically are middle-aged or older men who develop gait disturbances, numbness, paresthesias (tingling), and leg weakness. Over time, bladder and bowel dysfunction may develop, and in severe cases, patients can become wheelchair-bound. The progression is usually slow and can be stepwise, with periods of worsening and stabilization. Early symptoms are often subtle, leading to delayed diagnosis—sometimes for over a year after onset 2 4 9.

• Cranial DAVFs present with a more diverse symptom profile. Headache is common, with its type often suggesting the fistula's location: migraine-like headaches are more frequent in non-carotid-cavernous DAVFs, while non-migraine headaches with ocular symptoms (such as double vision or eye pain) are typical of carotid-cavernous fistulas. Pulsatile tinnitus—where the patient hears a rhythmic noise matching their heartbeat—is another classic sign, especially with lesions near the transverse or sigmoid sinuses. When venous drainage involves cortical veins, patients are at higher risk of intracranial hemorrhage, seizures, or even rapid neurological decline 5 6 13.

Symptom Evolution and Severity

• Progressive Symptoms: Many patients experience a gradual worsening of symptoms. For spinal DAVFs, this typically means incremental loss of motor and sensory function in the lower extremities, often accompanied by increasing sphincter problems (urinary or bowel incontinence) 2 4.
• Aggressive Presentations: DAVFs with retrograde venous drainage (especially into cortical veins) carry a much higher risk of brain hemorrhage or rapid onset of severe neurological deficits, such as seizures or coma. These aggressive fistulas require urgent intervention to prevent permanent disability or death 6 12 13.
• Quality of Life: Despite the potential severity, up to 70% of patients with cranial DAVFs report little to no long-term impact on quality of life when appropriately treated 5.

Recognizing Red Flags

• For middle-aged men with ascending motor and sensory deficits, especially when combined with bladder disturbances, spinal dural AVF should be high on the differential diagnosis 2 4.
• Ocular symptoms plus headache should prompt consideration of a carotid-cavernous fistula 5.
• Any sudden-onset neurological decline or hemorrhage in someone with a known DAVF is an emergency 6 12.

Types of Dural Arteriovenous Fistulas

Understanding the various types of DAVFs is crucial for diagnosis, risk assessment, and treatment. Classification is typically based on location (cranial or spinal), angiographic features, and especially the pattern of venous drainage, which predicts clinical behavior and risk.

Location	Drainage Pattern	Risk	Source
Cranial (e.g. cavernous sinus, transverse/sigmoid sinus)	Sinus only (antegrade)	Low	7 13 16
Cranial (anterior fossa, tentorium, foramen magnum)	Cortical venous reflux	High	6 8 12
Spinal (thoracolumbar, cervical, sacral)	Perimedullary veins	Progressive myelopathy	1 2 9
Hypoglossal canal/lateral foramen magnum	Variable	Site-specific symptoms	3 8

Table 2: Major Types

Cranial DAVFs

• Sinus-Draining Fistulas (Type I): These fistulas drain only into a dural venous sinus with normal direction (antegrade) of blood flow. They are considered low risk for aggressive complications and often present with benign symptoms such as pulsatile tinnitus or mild headache 6 7 13.
• Cortical Venous Drainage (Types II-V): When the abnormal flow extends into cortical veins, the risk of hemorrhage and neurological injury increases dramatically. The Borden and Cognard classification systems are commonly used to stratify these risks, with higher types indicating more dangerous drainage patterns 6 7 12.
  • Type II: Sinus with reflux into the sinus or cortical veins.
  • Type III/IV: Direct cortical venous drainage, with or without venous ectasia (dilated, fragile veins).
  • Type V: Spinal venous drainage, often causing myelopathy 6.

Spinal DAVFs

• Classic Spinal DAVF: The most common spinal vascular malformation, usually found in the thoracolumbar region of older men. The abnormal connection is between a dural artery and a radicular vein near the nerve root. The resulting venous congestion leads to slowly progressive spinal cord dysfunction 1 2 9 10.
• Other Spinal Types: Less common forms can arise in the cervical or sacral regions, or even from cranial sources draining into spinal veins, leading to myelopathy at locations distant from the fistula 1 11.

Other Special Locations

• Hypoglossal Canal and Lateral Foramen Magnum DAVFs: These rare types can have unique symptoms depending on their venous drainage—ranging from tinnitus, ocular symptoms, cranial nerve palsy, to myelopathy or hemorrhage. Understanding their anatomy is key for treatment planning 3 8.

Causes of Dural Arteriovenous Fistulas

The origins of DAVFs are varied and not yet fully understood. What is known is that these are acquired lesions, most frequently developing in adulthood, and arise due to pathological changes in the dural blood vessels and venous sinuses.

Cause	Mechanism	Population	Source
Venous sinus thrombosis	Induces angiogenesis, abnormal shunt formation	Middle-aged adults	7 13 17
Venous hypertension	Promotes new vessel growth, shunt formation	Both sexes, age 50+	9 17
Trauma/infection/surgery	Direct vessel injury, inflammation	Variable	13 17
Congenital (rare)	Vascular malformation at birth	Young patients	1

Table 3: Causes and Mechanisms

Acquired vs. Congenital Origins

• Acquired Lesions: Most DAVFs are acquired rather than congenital. The majority develop in middle to later adulthood, often without any identifiable genetic predisposition 1 7 13.
• Congenital Forms: Rarely, especially in younger patients or children, DAVFs may arise from congenital vascular malformations. These are more typical for intradural (not dural) AVMs 1.

Role of Venous Sinus Thrombosis and Hypertension

• Venous Sinus Thrombosis: Clotting of a dural venous sinus can lead to local hypoxia and inflammatory changes, stimulating new blood vessel growth (angiogenesis). This can result in abnormal shunts between arteries and veins within the dura 7 13 17.
• Venous Hypertension: Increased pressure within venous sinuses or draining veins is thought to be a driving factor—again promoting vessel proliferation and abnormal connections 9 17.
• Other Factors: Trauma, infection, or prior neurosurgical procedures may contribute in some cases by causing direct vessel injury or chronic inflammation 13.

Pathophysiology: Why Symptoms Develop

• Cranial DAVFs: The main danger comes when abnormal blood flow is directed into fragile cortical veins, which are not designed to handle high pressure, leading to risk of hemorrhage or neurological injury 6 12.
• Spinal DAVFs: Here, the abnormal connection leads to venous congestion and hypertension in the spinal cord veins, causing chronic ischemia and progressive myelopathy 9 10 11.

Treatment of Dural Arteriovenous Fistulas

Timely and definitive treatment of DAVFs is essential to prevent irreversible neurological damage or catastrophic events like brain hemorrhage. The choice of therapy depends on the type, location, and drainage pattern of the fistula, as well as the patient’s symptoms and overall health.

Approach	Best For	Efficacy/Outcome	Source
Endovascular embolization	Most cranial DAVFs, some spinal	High cure rates, low morbidity	14 16 18
Microsurgical disconnection	Spinal DAVFs, inaccessible cranial	Excellent, especially for spinal	15 9
Stereotactic radiosurgery	Small/inaccessible cranial DAVFs	Good in selected cases	16 18
Conservative management	Benign, low-risk DAVFs	Selected, spontaneous regression possible	3 16

Table 4: Main Treatment Options

Endovascular Embolization

• Cranial DAVFs: Advances in catheter-based techniques have made endovascular embolization the first-line therapy for most cranial DAVFs. Using microcatheters, liquid embolic agents (such as Onyx) are delivered directly to the fistula, closing the abnormal connection. This approach boasts high cure rates and minimal risk, especially for fistulas with accessible feeding arteries or veins 14 16 18.
• Spinal DAVFs: Embolization can also be effective for spinal DAVFs, especially when the arterial feeder is accessible and the fistula can be completely occluded. However, recurrence rates are higher than with surgery, and repeat angiography is often needed 15.

Microsurgery

• Spinal DAVFs: Surgical disconnection of the draining vein is the gold standard and offers the highest rates of definitive cure. Surgery is favored when endovascular access is difficult or after failed embolization. Most patients experience stabilization or improvement in neurological symptoms post-surgery, with minimal morbidity 9 15.
• Cranial DAVFs: Surgery may be used when embolization is not feasible, especially in complex or inaccessible locations 16 18.

Stereotactic Radiosurgery

• Used for small, deep-seated, or surgically inaccessible cranial DAVFs. Radiation causes gradual closure of the abnormal vessels over months to years. It is less effective for rapidly progressive or hemorrhagic lesions, but useful for low-risk, residual fistulas 16 18.

Conservative Management

• Observation: Low-risk, asymptomatic DAVFs—such as those draining only into a venous sinus with no cortical involvement—may be managed with monitoring, as spontaneous regression can occasionally occur 3 16.
• Medical Management: Focuses on symptom relief and managing complications, but does not address the underlying fistula.

Outcomes and Prognosis

• Excellent Outcomes: When treated appropriately, the vast majority of patients stabilize or improve. For cranial DAVFs with cortical venous drainage, aggressive intervention has markedly reduced rates of hemorrhage and neurological decline 12 14.
• Spinal DAVFs: Gait and bladder function often improve after treatment, especially if intervention is not delayed. Severe, longstanding deficits may be less reversible 15.
• Complications: The combined risk of significant complications (death, stroke, hemorrhage) after treatment is low—typically 2–3%—when performed in experienced centers 12 15.

Conclusion

Dural arteriovenous fistulas are rare but treatable vascular lesions that can have serious neurological consequences if left unmanaged. Their impact and prognosis depend on their location, drainage pattern, and promptness of diagnosis and intervention.

Key Takeaways:

• Symptoms are variable and depend on the site and venous drainage pattern—ranging from mild sensory symptoms to paralysis or life-threatening hemorrhage 2 4 6 13.
• Types are classified by location (cranial versus spinal) and drainage (sinus only vs. cortical vs. spinal veins), which guides risk assessment and management 1 6 7.
• Causes are usually acquired—most often due to venous sinus thrombosis and hypertension, sometimes following trauma or surgery 7 13 17.
• Treatment options include endovascular embolization, microsurgery, radiosurgery, and, rarely, conservative monitoring. Early intervention offers the best chance for recovery and prevention of complications 14 15 16 18.

Early recognition and multidisciplinary management are vital for ensuring the best possible outcomes for patients with dural arteriovenous fistulas.