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

Alternative Names

Water on the brain

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. Symptoms vary depending on the cause of the obstruction to CSF circulation, the age at which the problem develops, and the extent of damage to brain tissue 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, risks for developing hydrocephalus include congenital defects, tumors of the central nervous system, intrauterine infection, infections in that affect the central nervous system (such as meningitis or encephalitis ), injury occurring during the birth process, 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 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. The incidence is approximately 1 out of 1,000 people. Hydrocephalus most often occurs in children, but may also occur in adults and the elderly. See Normal pressure hydrocephalus (NPH) .

Signs and tests

Tapping with the fingertips ( percussion ) on the skull may show abnormal sounds associated with thinning and separation of skull bones. Scalp veins may appear dilated. The circumference of the head may be large, or there may be enlargement of only part of the head, most commonly the frontal area. Measurements of the circumference of the head, 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 focal neurologic deficits (localized loss of function), and reflexes may be abnormal for the age of the child. Tests:

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 indicates if hydrocephalus is present (best test).

A

lumbar puncture ( 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 of brain blood vessels may show vascular causes of hydrocephalus.

An

echoencephalogram , a form of ultrasound of the brain, may show dilation of the ventricles caused by hydrocephalus or intraventricular bleeding. This disease may also alter the results of a RHISA scan .

Treatment

The goal of treatment is to minimize or prevent brain damage by improving CSF flow. Surgical interventions are the primary treatment of hydrocephalus. This includes direct removal of the obstruction, if possible. Surgical placement of a shunt within the brain may allow CSF to bypass the obstructed area, if the obstruction cannot be removed. Shunting of CSF to an area outside of the brain (such as to the right atrium of the heart or to the abdominal peritoneum) is an alternative to shunting within the brain. Surgical cautery (destruction by burning) or removal of the parts of the ventricles that produce CSF may (theoretically) reduce CSF production. Antibiotics are used aggressively at any sign of infection. Severe infections may necessitate removal of a shunt. Follow-up examinations should continue throughout the child's life to evaluate the child's developmental level and to treat any intellectual, neurologic, or physical impairments. Public health/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. Prognosis 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 carries the best prognosis, although hydrocephalus caused by tumors has a very poor prognosis.

Complications

shunt

dysfunction (kinking, obstruction, separation of tubing, or similar problems)

infection

meningitis

encephalitis

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

Call your health care provider if symptoms indicate hydrocephalus. This disorder should be brought to the health care provider's attention promptly. 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 the local emergency number (such as 911) if emergency symptoms occur, including difficulties with sucking/feeding, high-pitched cry, fever , lethargy or somnolence , stiff neck (unwillingness to bend or move the neck or head), problems with breathing , seizures , irregular heartbeat , or no heartbeat.

Prevention

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.