The actual cause of hydrocephalus is not always clear and it differs with the age and circumstances. More than 70% of all hydrocephalus cases are congenital (discovered during the mother's pregnancy, at the time of birth, or soon after). There are also cases associated with infections, which affects the unborn child.  

Other causes of hydrocephalus include:

• Blockage of the CSF flow
• Overproduction of CSF
• Problem with the body absorbing the CSF
• Intraventricular Hemorrhage (IVH) - caused by head trauma during birth or by other causes
• Meningitis - an infection of the membranes surrounding the brain
• Neural tube defects
• Brain tumors
• Spina Bifida
• Other birth defects (often neurological in nature), which may have caused hydrocephalus

Hydrocephalus often occurs with no known cause or reason.