Brain, Nervous System and Mental Conditions


What Is Hydrocephalus?

Hydrocephalus normal, non-normal MRI scans

An MRI scan of a brain with hydrocephalus (left) and a normal MRI scan (right). The large dark area on the left is the ventricles, made bigger by a build-up of CSF.

Hydrocephalus (pronounced hi-dro-SEF-a-lus) is a harmful build-up of cerebrospinal fluid (CSF) in the ventricles of your child's brain. CSF is a clear fluid made in your child's ventricles. It bathes and protects your child's brain and spinal cord.

The word "hydrocephalus" means water (hydro) in the head (cephalus). This problem is sometimes called water on the brain. The "water" is actually CSF.

Normally, CSF flows from the ventricles, through the brain and into the space around the brain and spinal cord. A child's body is always making and absorbing CSF.

When the CSF cannot flow or doesn't get absorbed the way it should, the CSF builds up. This is hydrocephalus. The build-up puts pressure on your child's brain. Without treatment, hydrocephalus can cause problems with how your child's brain develops and how it works (cognitive function). Pressure on the brain from hydrocephalus can be deadly.

Hydrocephalus in Children

Common causes of CSF blockage which causes hydrocephalus. Reprinted from 'Principles of Neurosurgery,' 2nd edition, edited by Setti S. Rengachary, Richard G. Ellenbogen, Copyright 2005, with permission from Elsevier


Common causes of CSF blockage include tumors (such as astrocytomas and gliomas), cysts and narrow CSF channels (aqueductal stenosis).

Hydrocephalus occurs in 1 in 500 to 1 in 1,000 babies.

Hydrocephalus can happen if the CSF is blocked because of the way your child's brain formed. This is called congenital hydrocephalus.

Hydrocephalus that happens for any other reason is called acquired hydrocephalus. Reasons for acquired hydrocephalus include:

  • Intraventricular hemorrhage  
  • Head injury
  • Brain infection
  • Brain tumor

Hydrocephalus at Seattle Children's

At Seattle Children's we've made a major commitment to the treatment of hydrocephalus. All our neurosurgeons are experts in treating this condition. We perform more than 200 hydrocephalus surgeries a year. We are also international leaders in hydrocephalus research.

Our first priority is to improve patient care. We are working to lower the risk that children will get shunt infections or need their shunts replaced. Also, we use methods to reduce the amount of radiation your child is exposed to during imaging scans.