Arteriovenous malformation or AVM is an abnormal connection between veins and arteries, usually congenital. This pathology is widely known because of its occurrence in the central nervous system, but can appear in any location.An AVM lacks the dampening effect of capillaries on the blood flow; it also causes the surrounding area to be deprived of the functions of the capillaries - removal of CO2 and delivery of nutrients to the cells. The resulting tangle of blood vessels, often called a nidus has no capillaries and abnormally direct connections between high-pressure arteries and low-pressure veins. It can be extremely fragile and prone to bleeding.
Symptoms of AVM vary according to the location of the malformation. Roughly 88%of people affected with AVM are asymptomatic; often the malformation is discovered as part of an autopsy or during treatment of an unrelated disorder ; in rare cases its expansion or a micro-bleed from an AVM in the brain can cause epilepsy, deficit or pain.
The most general symptoms of a cerebral AVM include headache and epilepsy, with more specific symptoms occurring that normally depend on the location of the malformation and the individual. Such possible symptoms include:
* Difficulties with movement or coordination, including muscle weakness and even paralysis;
* vertigo (dizziness);
* Difficulties of speech (dysarthria) and communication, such as aphasia;
* 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.
AVMs may occur in isolation or as a part of another disease (e.g. Von Hippel-Lindau disease or hereditary hemorrhagic telangiectasia).Treatment can be symptomatic, or it can involve surgery or radiation therapy.Ebolization, that is, cutting off the blood supply to the AVM with coils or particles or glue introduced by a radiographically guided catheter, can be used in addition to either, but is rarely successful in isolation except for in smaller AVMs.