Definition of Malformation, arteriovenous (AVM)
Malformation, arteriovenous (AVM): An arteriovenous malformation (AVM) is a congenital disorder (one present at birth) of blood vessels in the brain, brainstem, or spinal cord that is characterized by a complex, tangled web of abnormal arteries and veins connected by one or more fistulas (abnormal communications).
The AVM has no capillary bed of its own and the fistulas in the AVM permit high-speed, high-flow shunting of blood from the arterial to the venous side of the circulation. This shunting causes low blood pressure (hypotension) in the arterial vessels feeding the AVM and neighboring areas of the brain that they normally supply with blood.
AVMs typically cause problems before the age of 40. The most common symptoms of AVM include hemorrhaging (bleeding), seizures, headaches, and neurological problems such as paralysis or loss of speech, memory, or vision. The frequency of hemorrhage in various series ranges from 30-82%. AVM rupture accounts for 2% of all strokes.
There are three general forms of treatment for AVM:
Most people (perhaps 80% or more) with AVMs never experience problems due to them. However, AVMs that hemorrhage can lead to serious neurological problems, and sometimes death.Source: MedTerms™ Medical Dictionary
Last Editorial Review: 6/14/2012
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