|
My Child Has:
|
|
Arteriovenous Malformations
|
|
|
|
|
|
AVMs are abnormal connections between arteries and veins that are congenital (present at birth). They don't have the normal intervening capillary bed, the network of tiny vessels (capillaries) that normally connect arteries and veins. AVMs are more common in the brain than in other regions.
|
|
|
|
|
|
For most AVMs precise cause(s) are unknown. They are believed to be caused by a mistake in the formation of the normal arterial-capillary-venous connections that occurs during early embryonic life. No known food, medication, or activity during pregnancy can cause an AVM.
|
|
|
Some AVMs appear in a familial disorder called hereditary hemorrhagic telangiectasia (HHT) (Rendu-Osler-Weber syndrome). The two genes that cause HHT are known; both result in the loss of function in cell receptors. The condition usually presents with telangiectasia of the skin and mucous membranes (mouth and gastrointestinal tract). The telangiectasia bleed, typically during puberty. In HHT, AVMs also occur in the lungs, liver, and brain.
Another genetic condition is called capillary malformation- AVM. Multiple, usually oval capillary stains occur in a family; an AVM is present in about 10 percent of family members the causative gene is RA5AI- it also is involved in some patients with Parkes Weber syndrome.
|
|
|
|
|
|
They probably develop before 5 to 6 weeks of embryonic life. Usually an AVM is seen as an innocent vascular stain at birth; often they begin to enlarge in childhood and adolescence. Intracranial (within the head) AVMs are silent and present slowly or suddenly in adults.
|
|
|
|
|
|
They can occur in any organ in the body, in order of frequency: head, limbs, trunk, and internal organs.
|
|
|
|
|
In infancy and childhood, the blush of an AVM can be mistaken for hemangioma (the most common tumor of infancy). 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.
|
|
|
|
|
|
A specialist should be contacted whenever an AVM is suspected.
|
|
|
|
|
|
Intracranial AVMs often present with headache or other neurologic signs or with sudden bleeding into the brain. AVMs outside the brain present more slowly with color changes, then ulceration/bleeding of the skin, and persistent pain. In time, if the blood flow through an AVM is excessive, the heart can become overworked.
|
|
|
|
|
|
On physical examination, the overlying skin is warm and, in time, the pulsation of blood flow can be felt. The shunting of blood through an AVM can be detected earlier by ultrasonography.
|
|
|
|
Magnetic resonance imaging (MRI) is the best diagnostic examination and gives the most information about the extent of the anomaly. The most precise study is angiography, in which a contrast dye that can be seen by X-ray fluoroscopy is injected into the AVM via a flexible tube called a super selective catheter that is usually inserted in the groin.
|
|
|
|
|
|
Some intracranial AVMs are controlled by proton-beam irradiation, while others can be treated by embolization (injection of material into the center of the anomaly via a catheter) and/or surgical excision. In other parts of the body, AVM is often treated either by embolization or sclerotherapy (direct injection of an irritating solution). Whenever possible, surgical resection gives the best chance for a "cure."
|
|
|
|
|
|
Investigators hope to learn more about AVMs by studying the normal development of arteries, capillaries, and veins during the embryonic period. By understanding the molecular signaling involved in the formation and growth of these vascular channels, it is hoped that defective messages can be interpreted. AVM tissues removed after treatment are also being studied in the Vascular Biology Laboratory.
|
|
|
|
|
Hereditary hemorrhagic telangiectasia (HHT) is a fairly common familiar vascular disorder that presents with tiny little capillaries on the skin and mucus membranes, three causative genes are known patients with HHT can develop AVMs in the lungs, brain, and gastrointestinal track.
Parkes Weber syndrome involves diffuse AVM of a limb with overgrowth of that limb. The affected limb usually has CM involving some of the skin, and is increased in length and girth. When the amount of blood passing through the AVM is very large, the heart is affected because it has to handle more blood flow (high-output cardiac failure). Our research collaborators have identified a gene (RA5AI) that is changed in about one half of the patients with this syndrome (CM_AVM).
|
|
|
|
Wyburn-Mason syndrome, also called Bonnet-Dechaume-Blanc syndrome, is a rare vascular malformation of the central nervous system. It is the association of a vascular anomaly in the retina and a cerebral AVM, sometimes accompanied by a facial capillary stain and/or overgrowth on one side of the body.
|
|
|
|
Cobb syndrome is an association of a CM of the skin with an underlying AVM of the spinal cord as well as the adjacent muscular and bony elements of the spine.
For more on research happening at Children's Hospital Boston, see The Moses Lab.
|
|
|
