The Vain of Galen Malformation is a spectrum of vascular malformations occurring in infants and young children with a one common feature, a large draining deep vein. 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 exchange of oxygen and nutrients to the brain are missing.
Since vein of Galen malformations lack capillaries, there is a shunt, meaning the blood flow is very fast in its return to heart 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’ or even causing stroke by stealing blood from other parts of the brain. This rare malformation develops in utero.
The Vain of Galen Malformation or Vein of Galen Aneurysm is a misnomer. In reality the dilated venous structure anatomically is not a Vain of Galen that has very important implications in endovascular treatment.
There are several different types of malformations by anatomic criteria, however by clinical presentation there are clearly two distinct categories with a wider spectrum of presentation in the second category.
Those who present early with a heart failure( large shunt) and those with more progressive course
without a heart failure (small or smaller shunt) either presenting in infancy or as an older children.
THE LARGE SHUNT CATEGORY
Neonates that present with congestive heart failure and a loud intracranial bruit (noise made by blood turbulence).
Sometimes this malformation can be detected during a prenatal ultrasound, 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.
SMALLER SHUNT CATEGORY-INFANTS
Infants presenting with abnormally enlarging head (hydrocephalus), and developmental delay.
SMALLER SHUNT CATEGORY-OLDER CHILDREN
Older children presenting with a large head and possibly seizures (epileptic fits) and maybe a stroke. They also may have learning difficulties.
Small or smaller shunt category 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 or even little older and some at few years of age because of late presentation. Their heads often remain large, but they ‘grow into’ their head size over time.
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