Arteriovenous Malformations (AVMs)

  • AVMsArteriovenous Malformations (AVMs) are abnormal connections between arteries and veins that are congenital (present at birth).

    • They don't have the normal network of tiny vessels (capillaries) that normally connect arteries and veins.
    • AVMs are more common in the brain than in other regions.
    • The cause of AVMs is unknown.

    No known food, medication, or activity during pregnancy can cause an AVM.

    How Boston Children’s approaches AVMs

    AVM tissues removed after treatment are being studied by researchers in the Vascular Biology Program. These studies may lead to better information about both the cause of AVMs as well as possible new treatments.

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  • How common are AVMs?

    AVMs are relatively rare birth defects. They occur approximately once in every 500 births.

    What are the symptoms of AVMs?

    AVMs develop before birth. Usually an AVM is seen as an innocent stain on your child’s skin at birth; often they begin to enlarge in childhood and adolescence.

    • Intracranial (within the head) AVMs have no visible symptoms. However, they may cause headaches or sudden bleeding into the brain.
    • AVMs outside the brain appear more slowly with color changes, then bleeding and persistent pain.

    In time, if the blood flow through an AVM is excessive, your child’s heart can become overworked.

    AVMs can occur in any organ in the body. The occur most frequently in the parts of the body below (in order of frequency):

    • Head
    • Limbs
    • Trunk
    • Internal organs

    In infancy and childhood, the blush of an AVM can be mistaken for hemangioma (the most common tumor in babies).

    • The AVM becomes obvious as signs of fast blood flow appear. The skin becomes a darker red or purple color, nearby veins enlarge a mass appears beneath the stain, and there is local warmth.

    What problems are associated with AVMs?

    Hereditary hemorrhagic telangiectasia (HHT) — A fairly common familiar vascular disorder. Children with HHT can develop AVMs in the lungs, brain, and gastrointestinal track.

    Parkes Weber syndrome — In this disorder, several AVMs plus overgrowth of a limb combine to put extra strain on the heart.

    • Our research collaborators have identified a gene that is changed in about one half of the patients with this syndrome.

    Wyburn-Mason syndrome (also called Bonnet-Dechaume-Blanc syndrome) — A rare combination of a vascular abnormality in the retina and an AVM in the brain.

    • It’s sometimes accompanied by a facial capillary stain and/or overgrowth on one side of the body.

    Cobb syndrome — The combination of a cavernous malformation (fragile arteries/veins) of the skin with an AVM of the spinal cord.

    What causes AVMS?

    We don’t really know. They are believed to be caused by a mistake in the formation of the normal connections between arteries, veins and capillaries that occurs during early embryonic life.

    No known food, medication, or activity during pregnancy can cause an AVM. 

  • Tests

    How are AVMs diagnosed?

    Your child’s doctor may be able to tell with a physical examination of your child. Around the area of the AVM, the skin is warm and, in time, the pulsation of blood flow can be felt.

    After the exam, your child’s doctor will probably want to do one or more of the following procedures:

    • Ultrasonography — To detect the rapid flow of blood through an AVM.
    • Magnetic resonance imaging (MRI) — This test gives the most information about the extent of the anomaly.
    • Angiogram— The most precise test to see the details of the AVM.  Your child’s doctor will inject a contrast dye that can be seen by x-ray fluoroscopy into the AVM via a flexible tube that is usually inserted in your child’s groin.
  • How are AVMs treated?

    Treatment often depends on where your child's AVM is located.

    Intracranial AVMs

    • Radiation
    • Embolization (injection of material into the center of the anomaly via a catheter)
    • Surgery

    AVMs in other parts of the body

    • Embolization
    • Sclerotherapy (direct injection of an irritating solution)
    • Surgery

    Wherever possible, surgery provides the best treatment.

  • What research is being done on AVMs?

    Investigators hope to learn more about AVMs by studying the normal development of arteries, capillaries, and veins during the embryonic period. By understanding the formation and growth of these vascular channels, we hope that defective messages can be interpreted.

    AVM tissues removed after treatment are also being studied in Children's Vascular Biology Program.

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