Cerebral AVM
Also known as: Cerebral Arteriovenous Malformation;
High Flow AVM
What is it?
A Cerebral AVM (arteriovenous malformation) is an
abnormal collection of tangled blood vessels.
High-pressure blood in distorted abnormal arteries flows
directly into large draining veins without the presence
of an intervening network of capillaries. These are
congenital lesions, which occur in less than 1% of the
population. AVMs usually cause medical problems by
bleeding or leaking blood. AVMs, may also cause seizures
or progressive neurological dysfunction.
Who gets it?
Cerebral AVMs are congenital lesions which arise
during fetal development. They occur in less than 1% of
the population. AVMs can run in families and can be
associated with other vascular lesions of the brain such
as cerebral aneurysms.
What causes it?
Cerebral AVMs are the result of abnormal development
of cerebral circulation. They result in a “tangle” of
abnormal arteries connected to large draining veins,
without the benefit of an intervening capillary network.
These congenital lesions may then enlarge by recruiting
more blood vessels throughout childhood and into
adulthood.
What are the symptoms?
Many patients with cerebral AVMs have no symptoms.
However, the most common reason brain AVMs come to
medical attention is through bleeding (rupture). Common
symptoms of a bleeding brain AVM include, severe
headache, nausea/vomiting and a new neurological
deficit, such as numbness, weakness or paralysis.
Patients may also present with seizures or progressive
neurological decline in the absence of AVM bleeding.
How is it diagnosed?
Cerebral AVMs can be seen on CT scans, MRI/MRA, and
CTAs. Specific sequences on the MRI can further help
evaluate these vascular malformations. Cerebral
angiography remains the gold standard in the evaluation
and grading of cerebral AVMs. Cerebral angiography aids
in better understanding the AVM’s inflow and outflow. An
angiogram is essential to planning any treatment for the
AVM.
What is the treatment?
There are three major treatment options for cerebral
AVMs. These include a combination of open microsurgery,
endovascular surgery, and stereotactic radiosurgery.
Microsurgery uses traditional open surgical techniques
with the help of a microscope and sometimes with
computerized image guidance to remove the AVM. Some
lesions may be too large, too deep, or located in too
important of an area of the brain for safe microsurgical
excision. In such cases other treatments may be
necessary. In endovascular surgery, treatment is
performed from within the affected blood vessel.
Specially designed microcatheters are navigated by means
of an angiogram into the nidus of the AVM. The lesion is
then occluded from the inside using a process of
embolization with either particles or glue. Some forms
of endovascular treatment may be investigational and
therefore require a special consent. Although very
effective in reducing the size of an AVM, endovascular
embolization is rarely able to completely obliterate all
but the smallest of AVMs. Endovascular therapy,
therefore, is usually combined with either microsurgery
or stereotactic radiosurgery to give the best chance.
Stereotactic radiosurgery involves the delivery of a
highly focused beam of radiation to the AVM. The two
most common forms of radiosurgery are linear accelerator
based radiosurgery (also known as LINAC or photon knife)
and gamma ray based radiosurgery (gamma knife).
Radiosurgery may be less risky when compared to
microsurgery, for patients with AVMs that are deep or
located in important brain areas. However, the ability
of conventional radiosurgery to cure an AVM drops off
sharply as the AVM diameter goes above 2.5 cm (1 inch).
With radiosurgery cure is not immediate and may take up
to two or three years. During this time, the patient may
require follow-up tests and will still be at risk for
problems from the AVM. For these reasons, radiosurgery
is especially appropriate for small lesions that are
located in or near critical brain areas or are very
deep.
This information has been designed as a comprehensive and quick reference
guide written by our health care reviewers. The health information written
by our authors is intended to be a supplement to the care provided by your
physician. It is not intended nor implied to be a substitute for
professional medical advice.
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