What Is It?

Hydrocephalus, also known as “water on the brain,” is a condition in which there is extra cerebrospinal fluid around the brain and spinal cord. Cerebrospinal fluid acts as a cushion for the brain and spinal cord, supplies nutrients and takes away waste products. Hydrocephalus occurs when there are problems with the flow or absorption of cerebrospinal fluid.

Hydrocephalus can be present at birth (congenital) or can develop later (acquired).

  • Congenital hydrocephalus is present at birth, although it may not be detected until later in life. It forms because of abnormal development of the brain and surrounding structures. The exact cause is usually unknown, but contributing factors may include a genetic predisposition and certain infections during pregnancy.

  • Acquired hydrocephalus results from injuries or illnesses that occur at birth or later. It can develop as a complication of infections in the brain and spinal column (meningitis), bleeding of blood vessels in the brain, severe Head injury, or brain tumors or cysts. Hydrocephalus also can occur when there is no known injury or illness to cause it.

Hydrocephalus can be classified according to its cause:

  • Obstructive (non-communicating) hydrocephalus results from an obstruction within the system of cavities (ventricles) in the brain. The obstruction prevents the cerebrospinal fluid from flowing (or “communicating”) with the subarachnoid space, the area that surrounds the brain and spinal cord, as it normally should. Obstructions can be present at birth or can occur later. One of the most common types is aqueductal stenosis, which occurs because of narrowing of the aqueduct of Sylvius, a channel that connects two ventricles together.

  • Non-obstructive (communicating) hydrocephalus results from problems with the production or absorption of cerebrospinal fluid. One of the most common causes is bleeding into the subarachnoid space (subarachnoid hemorrhage). Communicating hydrocephalus also can be present at birth or can occur later.

Another type of hydrocephalus, called normal pressure hydrocephalus is an acquired type of communicating hydrocephalus in which the ventricles are enlarged but not under high pressure. Normal pressure hydrocephalus is seen in older adults. It may be the result of injury or illness, but in the majority of cases the cause is unknown.

Premature infants born before 34 weeks or weighing less than four pounds have a high risk of rupture and bleeding of blood vessels in the brain (intraventricular hemorrhage). Severe bleeding can lead to acquired hydrocephalus, communicating or non-communicating depending on the site and extent of the bleeding.


The most common symptoms of hydrocephalus vary depending on the age of onset.

In infants, symptoms include:

  • A large head that is growing rapidly
  • A bulging “soft spot” on top of head (anterior fontanelle)
  • Irritability
  • Seizures
  • Delays in development

In older children and adults, symptoms include:

  • Headache
  • Difficulty walking
  • Loss of athletic abilities
  • Change in personality
  • Decrease in mental abilities

At any age, symptoms include:

  • Vomiting
  • Lethargy



Congenital hydrocephalus may be diagnosed during a routine prenatal ultrasound, but often is discovered during infancy or early childhood. A doctor may suspect hydrocephalus before other symptoms appear if an infant has a large head that seems to be increasing in size rapidly. However, the most common cause of a large head in an infant is not hydrocephalus but a family history of large heads. If the anterior fontanelle (soft spot) is still open, an ultrasound of the head can distinguish a normal large head (macrocephaly) from hydrocephalus. If the results of that ultrasound are abnormal, further evaluation is necessary.

The doctor will ask questions about the person’s medical history, and will perform a physical and neurological examination. Detailed pictures of the brain may be obtained with computed tomography (CT) or magnetic resonance imaging (MRI). If these pictures reveal hydrocephalus or other abnormalities, the child or adult usually is referred to a neurosurgeon for further evaluation and treatment.

Expected Duration

Although the symptoms may subside with treatment, the duration varies according to the type and cause of the hydrocephalus.


A few of the causes of hydrocephalus can be prevented:

  • To help avoid severe Head injury, wear appropriate protective gear when participating in contact sports or other activities, such as skiing and sledding, with a risk of head trauma.

  • If you are pregnant, visit your doctor as soon as you know you are pregnant and frequently throughout the pregnancy. Your doctor will screen you for infections and other problems that may occur during pregnancy. Regular visits also will reduce the risk of premature birth.



Treatment of hydrocephalus depends on its cause. Occasionally, medications are used to slow the rate of cerebrospinal fluid production temporarily.  However, this has not been successful for long-term treatment. Most cases require drainage of the excess fluid. A tube called a shunt is inserted into one of the cavities in the brain through a hole in the skull. The shunt is tunneled under the skin and carries the cerebrospinal fluid into another area of the body, such as the abdomen, where it can be absorbed. The shunt may need to be replaced periodically as a child grows or if an infection develops or the shunt becomes blocked.

Some people with obstructive hydrocephalus can be treated with a technique called ventriculostomy in which a neurosurgeon makes an incision at the site of the blockage to allow cerebrospinal fluid to drain. Surgeons also are experimenting with surgical repair of congenital hydrocephalus while the fetus is still inside the mother.

When To Call A Professional

Call your doctor if you or your child develops symptoms of hydrocephalus or has a severe Head injury. Also call your doctor if you become pregnant.


The prognosis depends on the cause of hydrocephalus and usually is better if the problem is diagnosed and treated early. Rapidly progressing or long-standing hydrocephalus can cause brain damage and death.

Children with hydrocephalus have a higher risk of various developmental disabilities. Even after treatment, most children with hydrocephalus have decreased intelligence, memory problems and visual problems, including strabismus (abnormally aligned eyes). Children with hydrocephalus also may enter puberty earlier than normal.

With appropriate treatment, the majority of infants with hydrocephalus survive and approximately half have normal intelligence.

Johns Hopkins patient information

Last revised:

Diseases and Conditions Center

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.