Congenital Hydrocephalus

Congenital hydrocephalus is caused by a brain malformation or birth defect that causes excessive cerebrospinal fluid (CSF) to accumulate in brain cavities, called subarachnoid space.

Cerebrospinal fluid is a clear, colorless liquid that surrounds the brain and spinal cord, protecting them from injury. It carries nutrients to the brain and spinal cord and takes away waste. In a healthy person, the amount of this fluid produced by the brain is absorbed by the body. In hydrocephalus, the fluid fails to drain and accumulates, leading to pressure on the brain.

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A build-up of this fluid may result from:

  • Too much CSF produced, a condition known as choroid plexus papilloma
  • Blocked flow of CSF through the cerebrospinal system
  • Brain not absorbing enough of the fluid

Congential hydrocephalus — from the Greek word for water (hydro) and head (cephalus) — affects one out of every 1,000 newborns.

A less common type of hydrocephalus, called acquired hydrocephalus, occurs after birth, when a tumor, injury or disease blocks the absorption of cerebrospinal fluid.

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The most common cause of congenital hydrocephalus is obstruction of the cerebral aqueduct — the long, narrow passageway between the third and fourth ventricle or cavity of the brain. This condition may result from a blockage, infection, hemorrhage, tumor or arachnoid cyst.

Other medical problems associated with congenital hydrocephalus may include:

  • Chiari malformations, an abnormality at the base of brain where the spinal column joins the skull
  • Craniosynostosis, when the bones in the skull fuse together before the brain has stopped growing
  • Dandy-Walker syndrome, when the fourth ventricle is enlarged because of partial or complete closure of its outlets
  • Hydranencephaly, a rare condition in which the brain's cerebral hemispheres are absent and replaced by sacs filled with cerebrospinal fluid
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Prenatal Diagnosis

With sophisticated imaging technologies, congenital hydrocephalus can be detected in a fetus as early as the third or fourth month of pregnancy. By the fifth or sixth month, abnormal dilation of brain cavities is more clearly detectable. Tests to identify the condition before your baby is born include:

  • Amniocentesis -- This, or a needle aspiration of intrauterine fluid, may be performed to detect the presence of other birth defects associated with hydrocephalus.
  • Ultrasound -- Performed by a radiologist or perinatologist, this test will establish if there is an abnormal collection of fluid but may not show the obstruction.

Postnatal Diagnosis

Congenital hydrocephalus can be detected before birth, but it is more often diagnosed at birth or shortly after. To make a diagnosis, our experts thoroughly evaluate your child's physical condition.

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Congenital hydrocephalus generally isn't treated until after birth, even if diagnosed in the womb. The condition most often is treated by removing the cause of the condition, such as a tumor or other blockage, or inserting a shunt. A shunt is a small flexible plastic tube that diverts excess cerebrospinal fluid (CSF) from the brain to another part of the body where the fluid can be reabsorbed.

Some children can be treated with an alternative procedure called endoscopic third ventriculostomy (ETV). In this procedure, a small hole is made in the floor of the third ventricle of the brain, allowing the cerebrospinal fluid to bypass the obstruction and flow toward the area where it can be reabsorbed by the body.

Your child's medical team will design a treatment plan tailored to your child's specific needs and that may include more than one kind of treatment. You and your child may be referred to additional doctors or other medical professionals. Any possible risks or complications from your child's treatments will be explained to you in detail.

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Reviewed by health care specialists at UCSF Benioff Children's Hospital.

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