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What is Arteriovenous Malformation (AVM) and definition
Arteriovenous Malformation (AVM) is a congenital deformity in which an entanglement of arteries and veins forms. Rather than connecting into CAPILLARY BEDS that form between them, the arteries and veins in an arteriovenous malformation connect directly to one another. Veins lack the structure to accommodate the pressure BLOOD is under as it flows through the arteries and over time may become weakened and rupture.
The resulting bleeding can be life-threatening, depending on the size and location of the arteriovenous malformation. Most arteriovenous malformations are in the BRAIN, although an arteriovenous malformation can occur in other parts of the body. Though arteriovenous malformations are present at birth, many do not show symptoms until later in life, even adulthood.
The symptoms of AVM vary and often are vague, making diagnosis sometimes difficult. Cerebral AVMs (AVMs in the brain) may cause HEADACHE, seizures, and STROKE-like symptoms if they apply pressure to surrounding brain tissue or if they bleed. HEMORRHAGE in the brain can cause permanent damage to the brain, resulting in PARALYSIS, cognitive loss, or death. AVMs elsewhere in the body may cause PAIN or bleeding; hemorrhagic bleeding is life-threatening. COMPUTED TOMOGRAPHY (CT) SCAN and magnetic resonance angiography, which combines MAGNETIC RESONANCE IMAGING (MRI) with dye injected into the blood vessels, are the key diagnostic procedures to detect AVM.
Treatment depends on the size and location of the AVM and may include surgery to remove the web of blood vessels, injection of a substance to block the flow of blood through the AVM (embolization), or RADIOFREQUENCY ABLATION to close off the blood vessels. Treatment often carries significant risk of uncontrolled bleeding because of the unstable nature of the AVM, and sometimes the risk of attempting treatment is greater than the risk of leaving the AVM untreated. Treatment that successfully removes or seals the AVM ends the threat of hemorrhage.