Dural arteriovenous fistula
Encyclopedia
A dural arteriovenous fistula (DAVF), also called a dural arteriovenous malformation (DAVM), is an abnormal direct connection (fistula
) between a meningeal
artery
and a meningeal vein
or dural venous sinus
.
Classification of dural arteriovenous malformations or fistulas, groups into three types based upon their venous drainage:
The distinction between Types Ia and Ib is somewhat specious as there is a rich system of meningeal arterial collaterals. Type I dural fistulas are often asymptomatic, do not have a high risk of bleeding and do not necessarily need to be treated.
s which can bleed. Type II fistulas need to be treated to prevent hemorrhage. The treatment may involve embolization
of the draining sinus as well as clipping or embolization of the draining veins.
Fistula
In medicine, a fistula is an abnormal connection or passageway between two epithelium-lined organs or vessels that normally do not connect. It is generally a disease condition, but a fistula may be surgically created for therapeutic reasons.-Locations:Fistulas can develop in various parts of the...
) between a meningeal
Meninges
The meninges is the system of membranes which envelopes the central nervous system. The meninges consist of three layers: the dura mater, the arachnoid mater, and the pia mater. The primary function of the meninges and of the cerebrospinal fluid is to protect the central nervous system.-Dura...
artery
Artery
Arteries are blood vessels that carry blood away from the heart. This blood is normally oxygenated, exceptions made for the pulmonary and umbilical arteries....
and a meningeal vein
Vein
In the circulatory system, veins are blood vessels that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...
or dural venous sinus
Dural venous sinuses
The dural venous sinuses are venous channels found between layers of dura mater in the brain...
.
Classification
The BordenJonathan Borden
Jonathan Alan Borden is an American neurosurgeon who developed the Borden Classification of Dural Arteriovenous Fistulas. He has been involved in internet based telemedicine applications and is an editor of the RDDL specification for XML Namespaces....
Classification of dural arteriovenous malformations or fistulas, groups into three types based upon their venous drainage:
- Type I: dural arterial supply drains anterograde into venous sinus.
- Type II: dural arterial supply drains into venous sinus. High pressure in sinus results in both anterograde drainage and retrograde drainage via subarachnoid veins.
- Type III: dural arterial supply drains retrograde into subarachnoid veins.
Type I
Type I dural arteriovenous fistulas are suppied by meningeal arteries and drain into a meningeal vein or dural venous sinus. The flow within the draining vein or venous sinus is anterograde.- Type Ia – simple dural arteriovenous fistulas have a single meningeal arterial supply
- Type Ib – more complex arteriovenous fistulas are supplied by multiple meningeal arteries
The distinction between Types Ia and Ib is somewhat specious as there is a rich system of meningeal arterial collaterals. Type I dural fistulas are often asymptomatic, do not have a high risk of bleeding and do not necessarily need to be treated.
Type II
The high pressure within a Type II dural AV fistula causes blood to flow in a retrograde fashion into subarachnoid veins which normally drain into the sinus. Typically this is because the sinus has outflow obstruction. Such draining veins form venous varices or aneurysm
Aneurysm
An aneurysm or aneurism is a localized, blood-filled balloon-like bulge in the wall of a blood vessel. Aneurysms can commonly occur in arteries at the base of the brain and an aortic aneurysm occurs in the main artery carrying blood from the left ventricle of the heart...
s which can bleed. Type II fistulas need to be treated to prevent hemorrhage. The treatment may involve embolization
Embolization
Embolization is a non-surgical, minimally-invasive procedure performed by an interventional radiologist and interventional neuroradiologists. It involves the selective occlusion of blood vessels by purposely introducing emboli.-Therapeutic applications:...
of the draining sinus as well as clipping or embolization of the draining veins.