Arterio Venous Malformations
This web page is hosted by Melanie Torres
My son has an AVM and we are building a support group. Please
send me a note and watch this space for new developments. (We
will be adding a chat forum and some other ways to communicate.
Return to Cerebrovascular
An Arterio-Venous Malformation, or AVM is an abnormal collection of blood
vessels. Normally, red oxygenated blood is pumped by the heart through branching
tubes called arteries to the brain where it enters a fine network of tiny
vessels called capillaries. It is in these capillary beds where the blood
nourishes the tissues. Blue, deoxygenated blood then passes back to the heart
back through branching thin walled tubes called veins.
Arterial-Venous-Malformations are areas that lack the tiny Capillaries. The
location of the connection between the artery and the vein is called the shunt.
The area of tissue is called a nidus of the AVM. An AVM can be thought of as a
"Short Circuit" where the blood does not go to the tissues but is
pumped through the shunt and back to the heart without ever giving nutrients to
We don't know what causes most AVMs. People are born with AVMs, although they do
not appear to inherit them from their parents nor do they give them to their
children. It appears that AVMs may be caused by a rupture or clotting of a blood
vessel that happens during development before one is born. It is usually not
associated with either other maldevelopments or with other AVMs.
Usually, patients do not know they have an AVM. A number of the patients with
AVMs have seizures or persistent headaches. An AVM can put additional strain on
the blood vessels and the surrounding tissues. This is usually well tolerated in
the first 2 decades of life. But the increased flow of blood caused by the shunt
weakens the blood vessels. These weakened blood vessels can rupture. This is
known as a hemorrhage or bleed. If an AVM bleeds, the patient almost always has
an extremely severe headache, and most commonly has a stroke and often dies. The
chances of an AVM bleeding is 4 % per year. Larger AVMs occasionally may cause
progressive neurological problems by putting pressure on the brain or altering
the blood flow.
Do not use aspirin or aspirin containing compounds. Do not use non-steroidal
anti-inflammatory agents. If you were to bleed, these agents may make the bleed
worse. There is no other activity that is known to protect or cause a bleed in
AVMs can be seen on outpatient imaging studies such as CT's or MRI's. Angiograms
are inpatient procedures needed to image the arteries and veins before any
treatment. An angiogram is a x-ray movie of the blood flowing through the blood
vessels. It is made by injecting contrast into the arteries going into the head
and taking a series of x-rays films.
Treatment for AVMs include, Surgery, Radiation, Embolization or a combination of
these methods. With all of these treatments. complete obliteration of the AVM is
needed to avoid bleeding. Parietal treatment of the AVM is not known to offer
any benefit except for very specific conditions. Each treatment has it
advantages and disadvantages that make tailoring the type treatment to the
particular AVM the most sense.
- The AVM is obliterated at the time of surgery.
- Surgery has the longest "track record."
- Both small and large AVMs can be treated in this way.
- It requires an operation with General Anesthesia and some period of
- Some deep AVMs cannot be removed.
- Can be done without a craniotomy.
- Some small deep lesions can be most safely treated this way
- Lesions larger than 2.5cm are unlikely to be treated effectively.
- It takes two years for protection from bleeding after radiation.
- Does not require a Craniotomy.
- Eloquent deep areas can be treated by doing small areas at a time and
allowing the surrounding brain to recover.
- Testing of the importance of the area can be done by injection of
medication into the area before permanent treatment is done.
- Often requires multiple treatments.
- Requires the use of new materials that are often
- Is less likely than the other methods to totally obliterate the AVM
when used alone.
Combination of Treatments
is a method of plugging the blood vessels of the AVM. Under X-ray guidance, a
small tube, a catheter is guided from the femoral artery in the leg up into the
area to be treated.
- Can be tailored to the specific AVM type and patient considerations.
- Requires additional steps, time and coordination.
A neurological exam is performed before and after a small amount of medicine
is injected. This can help tell if the vessel that feeds the AVM also feeds
normal and important portions of the brain. After this, a permanent agent is
injected into the AVM and the catheter removed. This is repeated for each vessel
that feed the AVM.
During the embolization, the patient is awake but is made comfortable with
the help of the anesthesia team that monitors them and gives them medicines by
an intravenous line. After the embolization the patients usually spend the night
in the Neurological Intensive Care Unit (NICU) where they can be monitored
closely. Patients are usually hospitalized for 3 nights for each embolization
and usually require 2-3 embolizations at 2-6 week intervals. Patients resume
their normal full activity immediately upon each discharge. There may be some
mild headache after the embolization related to the blood vessels of the AVM
clotting, or some nausea related to some of the medicines that are given.
AVMs are a rare condition affecting about 250,000 people in the United States.
Much remains to be known. Which AVMs bleed ? Why do they bleed when they do?
What type of AVMs are there? Which is the best way to treat each type of AVM?
How can one maximize the benefits and minimize the risks of treatments. These
questions can only be answered by studies.
Any study requires the consent of the patient, approval of the hospital and
often the approval by the FDA and the company involved in making a medicine or
material. The nature of the study and the reason for the study is explained in a
consent form. You may be asked to participate in such study. If you are, it will
be explained to you and you will be asked to sign a special consent.