Arteriovenous malformation

Overview
Arteriovenous malformation or AVM is a congenital disorder of the connections between veins and arteries in the vascular system. 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.

Epidemiology
An estimated 300,000 Americans have AVMs, of which 12% (approximately 36,000) will exhibit symptoms that differ greatly in severity.

Pathophysiology
Arteries and veins are part of the human cardiovascular system. Normally, the arteries in the vascular system carry oxygen-rich blood at a relatively high pressure. 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. Capillaries successively join together, one upon the other, to form the veins that carry blood away at a relatively low pressure. The heart acts to pump blood from the low pressure veins to the high pressure arteries.

If the capillary bed is thought of as a sponge, then an AVM is the rough equivalent of inserting a tangle of drinking straw|flexible soda straws from artery to vein through that sponge. On an arteriogram, an AVM 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 and bypasses the capillary bed.

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. This bleeding can be catastrophic if it occurs in the brain, the lung or the gastrointestinal tract.

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:


 * Difficulties with movement or coordination, including muscle weakness and even paralysis;
 * vertigo (dizziness);
 * Difficulties of speech (dysarthria) and communication, such as alogia;
 * Difficulties with everyday activities, such as apraxia;
 * Abnormal sensations (numbness, tingling, or spontaneous pain);
 * Memory and thought-related problems, such as confusion, dementia or hallucinations.

Presentation
AVMs can occur in various parts of the body including the brain (see cerebral arteriovenous malformation), spleen, lung, kidney, spinal column, and liver. 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.

Diagnosis
AVMs can occur in various parts of the body


 * brain, causing a cerebral arteriovenous malformation
 * spleen
 * lung
 * kidney
 * spinal cord
 * liver
 * intercostal space
 * iris
 * spermatic cord

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.

Pons: Arteriovenous malformation


Brain: Arteriovenous malformation


Treatment
Treatment can be symptomatic, or it can involve surgery or radiation therapy.

It can also be carried out via in interventinal radiography procedure using a glue to cut off the blood supply to the AVM.

Research directions
The optimal management of AVMs remains an ongiong topic of clinical research. .