What is it?

This is a very rare condition affecting the blood vessels of the brain. The abnormality occurs during embryonic development and results in abnormal communications between the arteries and the veins in the blood vessels of the developing brain. The capillaries which normally connect arteries to veins and function to slow blood flow allowing for the drop off of oxygen and nutrients to the brain are missing. Since vein of Galen malformations lack capillaries, blood flow can be fast and this in turn increases the work of the heart. Blood drainage is towards a single deep draining vein, which becomes markedly enlarged (vein of Galen aneurysm). The result can be heart failure. The high flow of blood can also interfere with the normal blood drainage of the brain potentially causing hydrocephalus or 'water on the brain'.This rare malformation develops in utero. These patients may be new-borns with congestive heart failure due to arterial-venous shunting of blood in the brain.

Sometimes this abnormality can be detected during an antenatal ultrasound scan, but not always. In particularly severe cases, the growing baby has difficulty coping with this abnormal shunt and it develops heart failure. Sometimes this is so severe that the baby will die in utero. Often this is not the case and the baby is born, but rapidly goes into heart failure after birth. Sometimes this can be managed medically until the baby is a bit bigger, but sometimes the baby has to be treated in the neonatal period. Sometimes the heart failure is so severe that it affects all the other organs, including the lungs, liver, kidneys and brain and then despite treatment the baby will not survive.

If the baby has only mild heart failure it is safer to try and grow the baby until it is a little easier to treat.

Other children with vein of Galen malformations never develop heart failure, but because of the abnormal communications between the arteries and veins, the water that is inside the head and brain cannot be properly absorbed. This leads to an accumulation of water within the baby's head, so that the baby starts to develop a very large head. Often these babies are a little bit 'floppy' and sometimes just a little developmentally delayed.These children can be treated at a few months of age. Their heads often remain large, but they 'grow into' their head size over time.

Following embolisation these children often make rapid steps forward in their development. Children in whom the diagnosis is missed or remains untreated are at risk of developing permanent brain damage. The abnormal communications affect the ability of the blood vessels to mature properly and can result in a permanent high pressure within the blood vessels. This affects the brain tissue, which fails to grow properly and can malfunction. These children may develop seizures or fits and may develop symptoms of a stroke.

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