Water on the brain

Alternative names

Hydrocephalus is an accumulation of cerebrospinal fluid in the ventricles of the brain, leading to their enlargement and swelling.

Causes, incidence, and risk factors

Cerebrospinal fluid (CSF) is formed in a region of the brain known as the choroid plexus. CSF usually circulates through channels of the brain known as ventricles, as well as flowing around the outside of the brain and through the spinal canal.

When the circulation or absorption of this fluid is blocked, or excessive fluid is produced, the volume of fluid in the brain becomes higher than normal. The accumulation of fluid puts pressure on the brain, forcing it against the skull and damaging or destroying the tissues.

The symptoms vary depending on the cause of the obstruction, the person’s age when the problem develops, and the extent of brain tissue damage caused by the swelling.

In infants, fluid accumulates in the central nervous system, causing the fontanelle (soft spot) to bulge and the head to expand. An infant’s head can enlarge because the bony plates that make up the skull have not yet fused together. However, once the skull bones are completely fused together, at about age 5, the skull will no longer expand.

In small children, hydrocephalus may be associated with infections acquired before birth, injury occurring during the birth process, congenital defects, tumors of the central nervous system, infections that affect the central nervous system (such as meningitis or encephalitis ), and trauma before or after birth (including subarachnoid hemorrhage). Myelomeningocele, a disorder involving incomplete closure of the spinal column, is strongly associated with hydrocephalus.

In older children, risks include a history of congenital or developmental defects, space-occupying lesions or tumors of the brain or spinal cord, central nervous system infections, bleeding anywhere in the brain, and trauma.

Hydrocephalus most often occurs in children, but may also occur in adults and the elderly.

See normal pressure hydrocephalus (NPH).


  • Enlarged head (increased head circumference)  
  • Bulging fontanelles (soft spots of the head) with or without enlargement of the head size  
  • Separated sutures  
  • Vomiting


  • Irritability, poor temper control  
  • Muscle spasticity (spasm)


  • Decreased mental function  
  • Delayed development  
  • Slow or restricted movement  
  • Difficulty feeding  
  • Lethargy, excessive sleepiness  
  • Urinary incontinence (loss of control over bladder)  
  • Brief, shrill, high-pitched cry  
  • Slow growth (child 0-5 years)


The symptoms vary depending on the amount of damage caused by pressure in the brain. The symptoms may include the following or other symptoms:

  • Headache  
  • Vomiting  
  • Vision changes  
  • Crossed eyes  
  • Uncontrolled eye movements  
  • Loss of coordination  
  • Poor gait (walking pattern)  
  • Mental aberrations (such as confusion or psychosis)  
  • Changes in facial and brow contours, eye spacing, or protrusion

Signs and tests

When a physician taps fingertips on the skull, there may be abnormal sounds associated with thinning and separation of skull bones. Scalp veins may appear dilated.

The circumference of the entire head may be large, or only part of the head may be enlarged, most commonly the frontal area. Head circumference measurements, repeated over time, may show progressive enlargement.

The eyes may be depressed, with a “setting-sun” sign where the sclera (white portion of the eye) is visible above the iris (colored portion of the eyes). A neurologic examination may show specific deficits, and reflexes may be abnormal for the age of the child.

The following tests may be performed:

  • Transillumination of the head (shining a light against the head) may show abnormal fluid accumulation in various areas of the head.  
  • A head CT scan is one of the best tests for identifying hydrocephalus.  
  • A spinal tap and examination of the CSF may be performed (rarely).  
  • Skull x-rays show thinning and/or separation of skull bones and enlargement of the skull.  
  • A brain scan using radioisotopes may show abnormalities of the fluid pathway.  
  • An arteriography may show causes of hydrocephalus related to the brain’s blood vessels.  
  • An echoencephalogram, a form of ultrasound of the brain, may show dilated ventricles caused by hydrocephalus or intraventricular bleeding.

This disease may also alter the results of a RHISA scan.


The goal is to reduce or prevent brain damage by improving the flow of CSF.

Surgery is the main treatment. The obstruction may be surgically removed, if possible. If the obstruction cannot be removed, a shunt may be placed within the brain to allow CSF to bypass the obstructed area.

Shunting CSF to an area outside the brain (such as the right atrium of the heart or the abdominal peritoneum) is an alternative to shunting within the brain. Removing or cauterizing (destroying by burning) the parts of the brain that produce CSF may (theoretically) reduce CSF production.

Antibiotics are usually used aggressively with any sign of infection. Severe infections may require the shunt to be removed.

Follow-up examinations generally continue throughout the child’s life to evaluate the child’s developmental level and to treat any intellectual, neurologic, or physical problems.

Visiting nurses, social services, support groups, and local agencies can provide emotional support and assist with the care of the child with hydrocephalus who has significant brain damage.

Expectations (prognosis)
Untreated hydrocephalus has a 50-60% death rate, with the survivors having varying degrees of intellectual, physical, and neurologic disabilities.

The outlook for treated hydrocephalus varies, depending on the cause. If the child survives for 1 year, more than 80% will have a fairly normal life span. Approximately one-third will have normal intellectual function, but neurologic difficulties may persist.

Hydrocephalus that is caused by disorders not associated with infection has the best outlook, although hydrocephalus caused by tumors usually has a very poor prognosis.


  • Problems with the shunt, such as kinking, blockage, or tube separation  
  • Infection       o meningitis       o encephalitis       o infection of the area to which CSF is shunted  
  • Intellectual impairment  
  • Neurologic damage (decrease in movement, sensation, function)  
  • Physical disabilities  
  • Complications of surgery

Calling your health care provider

Any symptoms of this disorder should be brought to the health care provider’s attention immediately. Call if a child’s head is getting larger or there is a change in the appearance of the face, head, or eyes. Also call if the condition deteriorates to the point that the child cannot be cared for in the home.

Go to the emergency room or call 911 if emergency symptoms occur, including difficulties with sucking/feeding, high-pitched cry, fever, lethargy or drowsiness, stiff neck (unwillingness to bend or move the neck or head), problems with breathing, severe headache, seizures, irregular heartbeat, or no heartbeat.

Protect the head of an infant or child from injury. Prompt treatment of infections such as meningitis and other disorders associated with hydrocephalus may reduce the risk of developing the disorder.

Johns Hopkins patient information

Last revised: December 4, 2012
by Janet G. Derge, M.D.

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