Topic Overview

Hydrocephalus of the brain occurs when there is an imbalance in how
cerebrospinal fluid (CSF) is made and absorbed, or in
how it flows. One way to classify this condition is by how the imbalance
occurs. There are two main ways:

  • Nonobstructive, or communicating,
    hydrocephalus occurs when the CSF flows out of the chambers of the brain (ventricles) and into
    the spinal canal, but it is not reabsorbed normally by the tissue surrounding
    the brain and spinal cord. Sometimes this type of hydrocephalus corrects
  • Obstructive, or noncommunicating,
    hydrocephalus occurs when the CSF does not flow properly between or out of the
    brain ventricles because of an obstruction, such as from a malformation or

In very rare cases the brain tissue makes too much CSF and the body
can’t properly absorb or distribute the high amount of fluid. This is called
overproduction hydrocephalus.

Cerebrospinal fluid sometimes builds up rapidly, such as with an
injury, and can cause sudden and severe damage if not treated. Other times the
fluid gradually accumulates and may not cause problems right away.

Types of hydrocephalus include:

  • Congenital hydrocephalus, which is
    present at birth. Congenital hydrocephalus may be caused by physical problems
    with how CSF flows or is made or absorbed, by infections or trauma during fetal
    development, or by
    teratogens. It may be linked with other birth
    defects that affect the spine, especially open
    neural tube defects.
  • Acquired
    hydrocephalus, which develops at the time of birth or later. It can be caused
    by infections such as
    meningitis, bleeding, injury, or a
  • Normal-pressure hydrocephalus, which usually develops in
    people who are age 55 or older. It is a potentially treatable cause of
    dementia. This type of hydrocephalus often occurs
    after head trauma, infections, and bleeding within the
  • Ex-vacuo hydrocephalus, which occurs when there is damage to
    the brain caused by
    stroke or traumatic injury. This type of hydrocephalus
    may not be a health danger for some people, in which case treatment is not

With all types of hydrocephalus, early detection and treatment are
important to minimize or prevent long-term problems.

Related Information


ByHealthwise Staff
Primary Medical Reviewer John Pope, MD – Pediatrics
Specialist Medical Reviewer Christian G. Zimmerman, MD, FACS, MBA – Neurological Surgery

Current as ofMay 4, 2017