Cerebral Arteriovenous Fistulas
To understand what arteriovenous dural fistulas are, we first need to explain some simple concepts. The human brain is covered by 3 membranes (meninges) that overlap one another, the outermost of which is called the dura mater.
Blood leaves the heart and enters the brain through the arteries and leaves the brain to return to the heart through the veins. The veins that drain the brain progressively join together to form large venous channels (dural sinuses) that lie within the dura mater.
A dural arteriovenous fistula is a direct communication between an artery and a vein or between an artery and a dural sinus. Such communication is dangerous because arteries work in high pressure regimes and veins in low pressure regime. This can lead to dilatation of the veins and even rupture causing intracranial bleeding.
Dural arteriovenous fistulas constitute 10 to 15% of all cerebrovascular malformations and can theoretically occur anywhere in the dura mater, although they are more common behind the eyes (carotid-cavernous fistulas) or behind the ears (transverse sinus fistulas/ sigmoid).
Most of them are diseases acquired throughout life and the main risk factors are a history of cerebral venous thrombosis, neurosurgery and head trauma.
The symptoms are diverse and basically depend on the location of the fistula and whether there has been intracranial bleeding (a more serious complication).
These include manifestations associated with increased pressure within the skull (headaches, nausea, vomiting, and vision changes), loss of strength and sensation in limbs, seizures, behavioral changes, and pulsatile tinnitus (tinudus) in the ears.
Cerebral catheterization (cerebral arteriography) remains the gold standard for diagnosing and defining treatment for dural arteriovenous fistulas.
Less invasive exams such as magnetic resonance angiography of the skull and/or angiotomography of the skull are able to make the diagnosis, in the vast majority of cases, but do not provide the details visualized in cerebral arteriography and are not able to define the best treatment modality.
The treatment modalities for dural arteriovenous fistulas are: conservative treatment (observation), endovascular treatment (embolization) and open surgery (microsurgery). The chosen modality will depend on the type of fistula, its location and the symptoms presented by the patient.
Endovascular treatment is currently the most indicated, with good results and a low rate of complications, they are performed via the artery or via the venous route through the use of various embolic materials that will occlude anomalous communications between arteries and veins.
How is a Cerebral Arteriovenous Fistula diagnosed?
The diagnosis of a cerebral arteriovenous fistula is made through several exams, such as computed tomography of the skull, magnetic resonance imaging of the brain and cerebral arteriography, the latter being the most important when it is desired to evaluate the lesion in detail and define the best form of treatment. there.
Why do Arteriovenous Fistulas appear?
Most DAVF are acquired. Predisposing factors are dural sinus thrombosis, head trauma, neurosurgery.
What are the possible complications of a Cerebral Arteriovenous Fistula?
Intracranial bleeding related to cerebral arteriovenous fistulas is the most serious complication, which can lead to severe and permanent neurological sequelae or even death. The bleeding rate will depend on the anatomical characteristics of the fistula and its location.
Other symptoms such as headache, seizures, altered cognition, altered vision and balance may also occur.
