This is part of our House MD Project series.
Click here to read the connection to the episode (spoiler alert!)
Danger level: High
What is it?
Arteriovenous malformation (or AVM for short) is a defect in the blood vessels causing an abnormal connection between veins and arteries.
Who gets it?
AVM isn’t very common, and not much data exists about who gets it. It is known, though, that in the United States about 300,000 people have it.
It usually occurs in young adults, even though the origin of the disease goes back to being a fetus.
What causes it?
To understand what AVM is, you first need to understand the basics of blood vessels in the body.
Our circulatory system (the system through which blood is delivered to organs in the body) is composed mainly of arteries and veins. Arteries (appearing red in the drawing below) carry oxygen-rich blood to our organs. Arteries divide into smaller and smaller arteries until the become the smallest blood vessels, called capillaries.
Capillaries join together and form veins (appearing blue in the drawing). The veins’ role is to take up waste products from the organs.
In AVM, defects in the circulatory system cause direct connections between arteries and veins, without the capillaries in between. When these happen in our nervous system (the brain or the spinal cord), 3 things can happen that lead to problems:
1. Hemorrhage – Due to the defect, blood can spill from the vessels to the surrounding area, including the brain (if the AVM is in the brain).
2. Seizures – Again, if the AVM is in the brain.
3. Neurological defect – A defect in the brain or spinal cord functions can happen and advance over months and years. This is what happened on the House episode.
Why does these happen? No one knows for sure. It may be because the area with the AVM “steals” blood from the normal blood vessels. Or because the AVM presses on the area outside of it.
(Remember that AVMs can occur anywhere in the body. In this article we deal with the nervous system simply because the House episode showed an example of this location).
How does it feel?
Most people don’t even know they have AVM, since no symptoms appear.
When they do appear, symptoms can include persistent headaches or seizures. If the AVM bleeds, it can cause a very severe headache and a stroke or even death.
When the AVM presses the surrounding area it can cause neurological problems depending on the area of the brain or spinal cord it’s located at. In the House episode, for example, it caused paralysis.
How is it discovered?
A CT scan or an MRI are used to discover AVMs. An angiography (a technique used to image the inside of blood vessels) of the area can also be used.
An angiography showing AVM in the brain. Photo by Dr Marina-Portia Anthony
How is it treated?
AVMs are treated by a surgery, by irradiation of the AVM, or by a process called embolization. In embolization, the doctor plugs the AVM by inserting a coil or glue that will block off the area.
What happens after treatment?
Without treatment, 2-4% of AVMs will bleed each year. Treatment should stop these complications from happening.
The bottom line – How do I avoid it?
Since you are born with AVMs, there is no known way you can avoid it.
This video shows how dangerous AVMs can be through the story of Amit, who had headaches which were first thought to be flu-related:
httpv://www.youtube.com/watch?v=IZGxW9RQQzk
What next?
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