A special case of arteriovenous malformation is the vein of Galen malformation. The vein of Galen is a large deep vein at the base of the brain. As in other AVMs, the capillaries, which normally slow blood flow and allow oxygen exchange with the surrounding tissues, are missing. Blood flows directly from arteries into veins without slowing down and without releasing its load of oxygen and nutrients.
In vein of Galen malformations, this rush of blood goes almost directly to the heart and can rapidly overwhelm it, leading to congestive heart failure. Sometimes the defect will be recognized on an ultrasound before birth, but most often it is seen in infants who experience rapid heart failure. In less severe cases, a child may develop hydrocephalus because the enlarged malformation blocks the normal flow or absorption of cerebrospinal fluid.
The most effective treatment for the malformation has been embolization rather than surgery. By feeding a narrow catheter through the arteries that lead to the defect, surgeons can introduce materials that block the blood flow through the malformation and form a clot that closes it off. The materials used can vary from a kind of fast-acting glue to small particles or coils. The procedure is often not 100% successful on the first try. By gradually closing off remaining areas of blood flow in subsequent efforts, surgeons can usually shutdown the pathway. After successful embolization, patients can go on to full and active lives.