What Is Dural Arteriovenous Fistula?
A dural arteriovenous fistula is the abnormal connection of vessels (the vein and the artery) in the hard covering above the brain or spinal cord (dura mater). It is an abnormal pathway between arteries and veins that can occur in the spinal cord, brain, or other areas of the body. It is not passed through genetically, but it can occur later in life in middle-aged people.
What Can Cause Dural Arteriovenous Fistula?
Most of the dural arteriovenous fistulas do not have an exact origin, although some result from identifiable causes such as infection, traumatic head injury, tumors, or previous brain surgery. Most experts think that dAVFs, including the larger brain veins, usually occur from the blockage of one of the brain's venous sinuses or progressive narrowing, which will track circulated blood from the brain back to the heart. An arteriovenous fistula can also occur if individuals have a piercing injury, such as a stab wound or gunshot, on the part of the body where an artery and vein are present adjacent to each other. Arteriovenous fistula can also be congenital.
What Are the Signs and Symptoms of Dural Arteriovenous Fistula?
The signs and symptoms of dural arteriovenous fistulas include:
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Headache.
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Tinnitus: Most patients with dAVFs will complain of a whooshing sound near the ear, and others explain it as a high-pitched ringing sound.
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Eye Symptoms: A few patients may develop pain behind the eye, eye swelling, eye redness, diminished vision, and even double vision when the abnormal artery-vein association is near the eye.
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Brain Hemorrhage: Certain patients can develop bleeding inside the brain. Patients at risk have dAVF that drains abnormal and high-pressure artery blood flow directly into the brain's veins. This is a serious situation known as cortical venous drainage (CVD). Symptoms indicative of brain hemorrhage include sudden-onset headache, vomiting, nausea, weakness, decreased level of consciousness, numbness, and speech trouble.
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Seizures: Patients with CVD will also develop seizures.
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Cognitive Decline: Patients with longstanding, untreated dAVFs can develop mental deterioration with symptoms similar to madness.
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Balance Difficulties.
Aggressive dAVF Symptoms: Aggressive dAVF can result from neurological effects like non-hemorrhaging neurological deficits (NHNDs) or bleeding in the brain (intracerebral hemorrhage). Bleeding in the brain can cause a sudden headache with varying degrees of neurological incapacity related to the hemorrhage's location and size.
Benign dAVFs Symptoms: Benign dAVFs can have both vision and hearing problems. The vision problems include eye bulge, visual deterioration, eye-related palsies, swelling in the eye lining, cavernous sinus syndrome, and hearing problems, including pulsatile tinnitus.
What Are the Types of Dural Arteriovenous Fistula?
The pattern of venous drainage defines the type of dAVF and its risk for bleeding. The types of dural arteriovenous fistula are:
Type I: Dural arterial supply will drain anterograde into the venous sinus.
Type II: Dural arterial supply will drain into the venous sinus. The high pressure in the sinus will result in retrograde drainage and anterograde drainage via the subarachnoid veins.
Type III: Dural arterial supply will drain retrograde into the subarachnoid veins.
What Are the Locations of Dural Arteriovenous Fistula?
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Transverse or sigmoid sinus.
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Cavernous sinus (indirect carotid-cavernous fistula).
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Superior sagittal sinus.
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Straight sinus.
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Anterior cranial fossa.
Who Is at Risk of Developing Dural Arteriovenous Fistula?
Dural arteriovenous fistula is more prevalent in females than males. However, the risk of hemorrhage from DAVF is higher in males. People of age between 50 and 60 typically develop the symptoms of this condition. However, diagnoses of the illness have still been made in different age groups.
Blood clots in veins are one of the risk factors for dural arteriovenous fistula. Recent findings indicate a possible link between the emergence of dAVFs and benign meningeal malignancies.
How to Diagnose Dural Arteriovenous Fistula?
To diagnose dural arteriovenous fistula, initial imaging tests like head CT (computed tomography) and brain MRI (magnetic resonance imaging) are taken.
1. CT: Contrast CT angiography can be used to diagnose the dural arteriovenous fistula. It can show the fluid buildup created by the increased cortical vein blood pressure and the actual bleeding.
2. MRI: Brain MRI can confirm the shape and extent of a dAVF, detect any micro-hemorrhages, and define the impact of every abnormal blood vessel structure linked to the fistula itself.
3. Cerebral Angiography: Catheter-based cerebral angiography, also known as digital subtraction angiography, is the most reliable and definitive tool for dAVF diagnosis. It is essential for defining:
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The number and location of the fistulae.
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Anatomy of the external carotid arteries, the dura, and any branches between them.
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The presence of cardiovascular disease.
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The total number of narrowing or blockages occurred in the dural sinus.
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The dilatation of any affected veins and their extent.
Superselective angiography is required to recognize the area of convergence of the feeding dural arteries and the draining vein's origin.
How to Treat Dural Arteriovenous Fistula?
The doctor will tailor the treatment decisions depending on the dAVF's location, presence or absence of CVD, severity, type of symptoms, and treatment risk. Treatment options for dAVFs include:
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Observation - If a patient has a dAVF without CVD and the symptoms are moderate, observation is often the recommended choice.
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Endovascular Embolization - This procedure includes passing a small catheter from a blood vessel from the groin up into the AVF, where glue or other material is injected into the abnormal vessel. It is the most common treatment done for dAVF and is often curative.
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Surgery - Open surgery and direct ligation or resection of the dAVF are given for a small subset of dAVFs when embolization is not secure or curative.
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Radiosurgery - When both surgery and embolization fail, a radiosurgery technique that precisely focuses radiation beams onto the dAVF can cause it to shrink over time.
What Are the Complications of Dural Arteriovenous Fistula?
The major complications of the dural arteriovenous fistula include:
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Infection.
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Hydrocephalus (when fluid accumulates in the skull and swells the brain).
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Cerebrospinal fluid leak.
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Stroke (brain attack).
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Cranial nerve palsy (when the ability to function is lost along one of the 12 sets of nerves).
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Severe blood loss.
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Hemorrhage (bleeding from an injured blood vessel).
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Subdural hemorrhage (a build-up of blood resulting from head injury or other factors in the subdural space).
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Subarachnoid hemorrhage (blood within the brain's subarachnoid region).
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Intracerebral hemorrhage (the result of blood abruptly rushing into brain tissue, damaging the brain).
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Venous congestion (a medical problem that occurs when blood in the legs pools instead of flowing normally.) or hypertension (increased blood pressure) and edema (swelling).
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Intracranial hypertension (if the pressure of the cerebrospinal fluid increases excessively in the area surrounding the brain).
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Spinal myelomalacia (the spinal cord's deterioration, which results in neurological impairment).
Conclusion:
A dural arteriovenous fistula is a condition that can bring about cognitive, neurological, and ear problems. Preventing it is not always possible since the causes are not known. Seeking prompt treatment can help in reducing the risk of complications. Reach out to a healthcare provider as soon as possible if one has any of the symptoms to rule out the disease.
