Dural arteriovenous fistulas
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A rare medical condition called dural arteriovenous fistula (dAVF) refers to the improper linking of an artery and a vein within the dura mater, the tough outer covering of the brain or spinal cord. Arteriovenous fistulas, which are abnormal connections between arteries and veins, may develop in other parts of the body as well, but in this case, they occur in the brain or spinal cord.
The presence of dAVF in a parent does not increase the likelihood of a child developing the condition. Typically, dAVFs manifest in individuals between the ages of 50 and 60, and they are not typically hereditary.
Although certain dAVFs have recognized origins, it’s believed that dAVFs involving large brain veins typically develop as a result of a venous sinus in the brain becoming congested or blocked.
The standard treatments for dAVF involve endovascular surgery or stereotactic radiosurgery, both of which are aimed at blocking the blood supply to the dAVF. However, in cases where these treatments are ineffective, surgery may be required to disconnect or remove the dAVF.
dAVFs can be categorized as low- or high-risk.
- Low-risk dAVFs. This causes drainage into the brain’s veins while maintaining drainage in the dura in the venous sinuses.
- High-risk dAVFs. This increases pressure in the cortical veins in the brain, increasing the risk of hemorrhage or symptoms similar to a stroke.
Symptoms
While some individuals with dAVFs may be asymptomatic, others may experience symptoms that can be categorized as either aggressive or benign.
Intracerebral hemorrhage or neurological consequences of nonhemorrhagic neurological deficits (NHNDs) can both cause aggressive dAVF symptoms.
According on the location and amount of the hemorrhage, bleeding in the brain frequently results in an acute headache with varied degrees of neurological impairment.
An NHND, in contrast, frequently manifests symptoms specific to its location and normally develops more gradually over days to weeks.
These aggressive signs may appear as:
- Seizures
- Dementia
- Parkinsonism
- Weakness
- Falling
- Tingling sensation or feeling of being burnt
- Headaches, nausea, and vomiting brought on by increased pressure.
- Incoordination
- Problems in walking
- Speech difficulties
- Facial aches
- Apathy
- Failure to thrive
Hearing problems, such as pulsatile tinnitus, a bruit behind the ear, are examples of additional dAVF symptoms. Other symptoms of dAVFs may include visual disturbances such as:
- Bulging of the eye
- The lining of the eye is swollen
- Paralysis of the eye
- Vision problem
- Cavernous sinus syndrome.
Rarely, venous hypertension can cause progressive dementia.
If you experience any signs or symptoms that appear strange or alarm you, schedule a doctor’s appointment.
If you encounter any seizure symptoms or signs that could be a sign of a brain hemorrhage, such as:
- Extreme headache that occurs all of a sudden
- Nausea or vomiting
- Visual loss or double vision
- Problem with balance
- One-sided body numbness or weakness
- Issues understanding or speaking clearly
Causes
Although some are the consequence of known causes such traumatic head injury (or traumatic AV fistula), infection, prior brain surgery, venous thrombosis, or tumors, the majority of dural arteriovenous fistulas are unclear in their origin. According to the majority of experts, one of the brain’s venous sinuses, which carry circulating blood from the brain back to the heart, gradually narrows or becomes blocked in most cases when dAVFs involving the larger brain veins occur.
Risk factors
Those who are genetically susceptible to venous blood clots (vein thrombosis) are among the risk factors for dAVFs. This could involve irregularities in blood clotting, which could raise the possibility of venous sinus occlusion or obstruction.
Those with dAVFs are typically affected in their late middle years (roughly from 50 to 60 years old). However, dAVFs can also happen to people who are younger, such as children.
Recent studies suggest a potential association between the development of dAVFs and benign meningeal tumors.
Diagnosis
Your doctor might advise having diagnostic imaging (radiology) tests if you exhibit any of the warning signs or symptoms of a dural arteriovenous fistula. These might apply to dural arteriovenous fistulas and include:
- Initial imaging. Cross-sectional images from magnetic resonance imaging (MRI) and non-contrast head computer tomography (CT) are frequently used in initial evaluation.
- CT head scans. These tests can detect both actual bleeding—which may be brought on by a dAVF but take place elsewhere in the brain’s venous system—and fluid accumulation brought on by increased cortical vein blood pressure.
- MRIs. With the use of these images, it is possible to define the size and location of a dAVF, find any microhemorrhages (extremely minute bleeding areas), and assess the significance of any aberrant blood vessel structures connected to the fistula itself.
- Angiography. The most accurate and conclusive method for diagnosing dAVF is still catheter-based cerebral angiography, commonly known as digital subtraction angiography. It is essential to figure out:
- The structure of the fistula blood vessel
- The presence of cardiovascular disease
- The amount and location of the fistulae
- The affected vein’s dilatation and extension
- The narrowing or obstruction of dural sinus
- The structure of the external carotid arteries, including any branches that lead to the dura
It may also be necessary to do superselective angiography to locate the point at which the feeding dural arteries and the draining vein’s insertion meet.
Treatment
The standard treatment for dural arteriovenous fistula involves surgery to either disconnect or block the abnormal connection between the artery and vein.
- Endovascular procedures. With the aid of X-ray imaging, your doctor may perform an endovascular procedure in which they put a long, thin tube (catheter) into a blood vessel in your leg or groin and thread it through blood vessels to the dural arteriovenous fistula.
In order to block the aberrant blood vessel connection, your doctor inserts the catheter into the blood vessel that supplies the dAVF and releases coils or a glue-like substance.
- Stereotactic radiosurgery. Your doctor will perform stereotactic radiosurgery to block the aberrant blood vessel link using finely focused radiation. The dAVF is destroyed by the fistula’s blood channels closing shut due to the strong radiation dose administered to it. The linear accelerator (LINAC), gamma knife, and proton beam therapy are among the various technological platforms employed in dAVF stereotactic radiosurgery.
- dAVF surgery. You could require dAVF surgery if stereotactic radiosurgery or an endovascular technique are not viable options for you. To disconnect the dAVF, stop the blood supply, and eliminate the fistula, surgery may be performed.
