Arteriovenous malformation or AVM in the majority of cases is a congenital disorder consisting of a connection between veins and arteries, this pathology is universally known because of its occurrence in the central nervous system, but can appear in any location.
The genetic transmission patterns of AVM -if any- are unknown, and AVM is not generally thought to be an inherited disorder, unless in the context of a specific hereditary syndrome.
Signs and symptoms
Symptoms of AVM vary according to the location of the malformation. Roughly (88% -needs citation) AVM are asymptomatic; often the malformation is discovered as part of an autopsy
or during treatment of an unrelated disorder (called in medicine an incidental finding), rarely its expansion or a micro-bleed from it, could cause epilepsy, deficit or elicit pain.
The most general symptoms include headache and epilepsy, with more specific symptoms occurring that normally depend on the location of the malformation and the individual. Other possible symptoms include:
Arteries and veins are part of the human cardiovascular system
. Normally, the arteries in the vascular system carry oxygen-rich blood. Structurally, arteries divide and sub-divide repeatedly, eventually forming a sponge-like capillary bed
. Blood moves through the capillaries, giving up oxygen and taking up waste products from the surrounding cells (CO2). Capillaries successively join together, one upon the other, to form veins that carry blood away. The heart acts to pump blood through arteries and uptake the venous blood.
If the capillary bed is thought of as a sponge, then an AVM is the rough equivalent of jamming a tangle of flexible soda straws from artery to vein through that sponge. On arteriogram films AVM formation often resemble a tangle of spaghetti noodles. This tangle of blood vessels forms a relatively direct connection between high pressure arteries and low pressure veins.
The result is a collection of blood vessels with abnormal connections and no capillaries. This collection, often called a nidus, can be extremely fragile and prone to bleeding.
AVMs can occur in various parts of the body
AVMs may occur in isolation or as a part of another disease (e.g. Von Hippel-Lindau disease or hereditary hemorrhagic telangiectasia).
This bleeding can be devastating, particularly in the brain. It can cause severe and often fatal strokes. If detected before a stroke occurs, usually the arteries feeding blood into the nidus can be closed off, ensuring the safety of the patient.
Treatment can be symptomatic, or it can involve surgery or radiation therapy.
An estimated 300,000 Americans
have AVMs, of which 12% (approximately 36,000) will exhibit symptoms that differ greatly in severity.
Society and culture
Cases in fiction
Despite many years of research, the central question of whether to treat AVMs has not been answered. All treatments, whether involving surgery or drugs, have risks and side-effects. Therefore it might be better in some cases to avoid treatment altogether and simply accept a small risk of coming to harm from the AVM itself. This question is currently being addressed in clinical trials.