What Arteriovenous Malformations (AVMs) and Dural Arteriovenous Fistulae (DAVF) Are
Brain Arteriovenous malformations (AVMs) and dural arteriovenous malformation (DAVF) are abnormalities of blood vessels, resulting in an abnormal connection between arteries and veins. AVMs are the result of one or more large arteries connecting directly to one or more veins through a network of vessels called a “nidus.” They can occur anywhere in the body, but the majority is found in the brain and spine. These typically have arterial supply from the larger intracranial vasculature (anterior, middle and posterior cerebral arteries, and vertebral arteries), They may cause symptoms, or be asymptomatic.
There may be a rupture in a supplying artery, vein or the nidus, which causes hemorrhaging. Hemorrhaging in the brain may result in a stroke. While the risk of rupture is low, it increases over time (the average risk is 2-4% per year). Consequently, treatment of AVMs in otherwise healthy people is recommended.
Dural Arteriovenous malformations (DAVF) are a form of malformation where the shunt develops within the dural venous channels. In contrast to AVMs, dural fistulae are usually acquired, whereas AVMs are developmental. These lesions have also been referred to as dural arteriovenous malformations (DAVM). This entity accounts for roughly 10-15% of all intracranial arterio-venous shunting lesions. Most are located in proximity to the large venous channels near the skull base (i.e.: transverse sinus, sigmoid sinus). Another feature that distinguishes these from AVMs is the arterial supply. DAVF in almost all cases will have direct arterial supply from the external carotid branches (meningeal arterial branches).
There are certain characteristics of an AMV or DAVF that may predict the risk of hemorrhage. Often such features can be assessed by non-invasive imaging (MRI). Typically, a cerebral angiogram will be required to accurately assess theses features and to plan treatment.