Congenital non-communicating hydrocephalus is a type of hydrocephalus that is present at birth. It is caused by a blockage in the flow of cerebrospinal fluid (CSF) within the brain. This blockage prevents the CSF from circulating properly, leading to an accumulation of fluid in the brain. This can cause the head to become enlarged and can lead to a variety of neurological symptoms, including developmental delays, seizures, and vision problems. Treatment typically involves the placement of a shunt to drain the excess fluid from the brain.