Arterio-venous malformation of the brain
Disclaimer: This fact sheet is for education purposes only.
Please consult with your doctor or other health professional to
make sure this information is right for your child.
What is it?
An arterio-venous malformation (AVM) is a condition that happens during
growth in the womb. It occurs in the small capillaries between an artery and a
vein. Enlarged blood vessels are produced, which can form a knot that looks
like a "bag of worms". The pressure in the enlarged blood vessels
causes movement (or shunting) of blood from artery to vein across the AVM.
Where does it occur?
AVMs can be found anywhere in the brain and may extend from the outer
surface to the inner cavities of the brain (ventricles).
In the rare Vein of Galen Malformation, an AVM occurs in one of the
large veins of the brain. The ordinary flow of the fluid in the brain
ventricles (cerebro-spinal fluid) is interrupted. The pressure of this fluid is
increased. This may cause enlargement of the ventricles
("hydrocephalus"). Occasionally brain and spinal cord AVMs may also
be found in association with skin lesions (angiomas).
What are the symptoms?
Although an AVM occurs in the brain before birth, only a small portion of
the children affected show symptoms straight away. Many never have any
problems. An AVM is usually recognised when bleeding has occurred into or
around the brain.
Symptoms may include:
- severe headache.
- vomiting.
- neck stiffness.
- fitting - sometimes epileptic fitting may occur without any bleeding.
AVM and babies
When a large AVM is present in a newborn baby, the symptoms may cause heart
problems. This is because the pressure in the AVM moves (or shunts) blood from
the arteries into the veins and causes an increase of blood in the veins. The
baby's heart cannot cope with the increased load.
How is it diagnosed?
- Your doctor will sometimes be able to hear the increased blood flow through
a stethoscope. The noise is called a bruit (broo-ee).
- An AVM is usually diagnosed only after symptoms have occurred (see
above).
- A CAT scan (x-ray) or MRI scan is used to diagnose the AVM.
- Injecting dye into a blood vessel that feeds blood into the brain shows the
AVM on x-rays (angiogram).
What is the treatment?
Your doctor may recommend surgery, as the risk of repeated bleeding is high.
However, this is not always the case. Ask your doctor about the choices for
your child.
- AVM is usually diagnosed only after symptoms occur. Ask your
doctor about the choices for treatment.
© The Children's Hospital at Westmead & Sydney Children's Hospital, Randwick - 1997-2008.
This document was reviewed on Wednesday, 2 April 2003.
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