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Friday, December 15th 2006

Explaining AVMs

Last night, as has been all over the news (and this blog), South Dakota Senator Johnson bled into his brain from an arteriovenous malformation. An NIH Doc on NPR explains ateriovenous malformations.

What is arteriovenous malformation (AVM)?

An AVM is a cluster of abnormally formed blood vessels. In medical images, it looks like a tangle of arteries and veins. About 300,000 people in the U.S. have these malformations, but most AVMs never cause any symptoms. The malformations can occur in various places around the body, however, those in the brain or spinal cord can cause the most widespread damage, because they affect the central nervous system.

AVMs disrupt the normal system used to provide oxygen to the brain. Ordinarily, arteries deliver oxygenated blood to the brain and veins return it to the heart and lungs. But in an AVM, blood that should be in an artery can flow through a vein. When that happens, part of the brain may not get enough oxygen. Also, veins are not meant to handle the high pressures and fast blood flow of arteries. So they may expand or even rupture, causing bleeding in the brain.

How do you treat it?

There are several different approaches. The idea is to get rid of the tangle. Surgeons can open up the brain and actually cut out the problem area. Another approach is radio-surgery, which uses gamma rays to eliminate the tangle. Or doctors can thread a small tube through the arteries and inject a glue-like substance that closes off the blood vessels.

The problem is that it may not be possible to eliminate the tangle of veins and arteries without disrupting blood flow to an important area of the brain. So not all AVMs can be safely eliminated.

What kind of recovery can be expected?

AVM is serious. A patient is most likely to do well if doctors can eliminate the malformation before it has caused brain damage. In this case, a patient can recover very quickly.

But if the AVM has already caused brain damage, recovery is similar to a stroke. It can take months or years. And the recovery may never be complete.

Also, all the procedures used to eliminate an AVM carry risks of their own. The surgery itself can cause brain damage or cause a stroke.

AVMs can be ablated surgically, here’s the brain-surgery.com page on some options for this.