Fetal ventriculomegaly is a congenital finding that affects the brain. The contents of the brain consist primarily of brain tissue, blood and cerebrospinal fluid (CSF). Enlargement of the ventricular system, the fluid-filled spaces in the brain, can be caused by the overproduction of CSF, inadequate brain development or destruction of brain tissue. In a normal fetal brain, the ventricles are less than 10 mm wide. When the ventricles are between 10-mm and 15-mm wide, the baby is diagnosed with mild ventriculomegaly. If the ventricles are more than 15 mm wide, the enlargement is considered severe.
Fetal ventriculomegaly occurs in approximately one in every 1,000 births, and in roughly half of the cases, there are no other findings or abnormalities in the baby.
Fetal ventriculomegaly can be detected through ultrasound (sonogram) towards the end of the first trimester. Evaluation of the brain and cranial structure is part of the routine ultrasound examination done by many obstetricians as part of their prenatal care. If the condition is detected on ultrasound, the patient may undergo a fetal brain MRI (magnetic resonance imaging) to determine the severity of the finding.
Most of the severe and mild cases will need both pre-natal and post-natal evaluation by neurosurgeons and neurologists. As soon as the baby is born, parents should bring their child in for a detailed examination. A physical examination is performed, and measurements of the infant's skull are taken. Treatment is not necessary unless hydrocephalus, which is the buildup of fluid in the brain, develops.
The long-term outlook for a child born with mild or borderline ventriculomegaly is excellent if it is an isolated finding. Approximately 90–100% have a normal outcome, giving the child an outstanding quality of life and a normal life expectancy. However, it is recommended that these children receive follow-up care and evaluations to monitor the development of the ventricular system to ensure that the finding does not progress further. Without intervention, a small percentage of these children may go on to develop hydrocephalus.