Hydrocephalus

What is hydrocephalus?

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 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 when the brain and surrounding structures develop abnormally. The exact cause is usually unknown, but contributing factors may include genetics and certain infections during pregnancy.
Acquired hydrocephalus results from injuries or illnesses that occur at birth or later, including infections in the brain and spinal column (meningitis), bleeding (hemorrhage) of blood vessels in the brain, severe head injury, 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 is caused by a blockage in the system of cavities (ventricles) in the brain. The blockage prevents the cerebrospinal fluid from flowing (or "communicating") with the area that surrounds the brain and spinal cord (subarachnoid space), as it normally should. Blockages 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 of the ventricles together.
Non-obstructive (communicating) hydrocephalus results from problems with cerebrospinal fluid being produced or absorbed. One of the most common causes is bleeding into the subarachnoid space. Communicating hydrocephalus can be present at birth or can occur later.

Another type of hydrocephalus, called normal pressure hydrocephalus (NPH), is an acquired type of communicating hydrocephalus in which the ventricles are enlarged but not under high pressure. NPH is most common in older adults and may be suspected because of gait abnormalities, cognitive impairment, and urinary incontinence. NPH may be the result of injury or illness, but in the majority of cases the cause is unknown.

Another type is called hydrocephalus ex-vacuo. A stroke or traumatic injury causes damage to the brain that causes brain tissue to shrink and the ventricles enlarge.

Premature infants born before 34 weeks or weighing less than 4 pounds have a higher risk of blood vessels bleeding in the brain. Severe bleeding can lead to acquired hydrocephalus, communicating or non-communicating, depending on the site and extent of the bleeding.

Symptoms of hydrocephalus

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

In infants, symptoms include

a large head that is growing too 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
urinary incontinence.

At any age, symptoms include

vomiting
lethargy.

Diagnosing hydrocephalus

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 head that seems to be getting larger too rapidly, or is larger than would be expected given the baby's current weight or length. If the soft spot (anterior fontanelle) is still open, an ultrasound of the head can determine if the head is getting larger due to hydrocephalus.

The doctor will ask questions about the person's medical history, and he or she 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, the child or adult usually is referred to a neurosurgeon for further evaluation and treatment.

Expected duration of hydrocephalus

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

Preventing 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 with a risk of head trauma such as skiing, riding a bike, and sledding.
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. Women of child-bearing age should have folate regularly in their diet before becoming pregnant to help prevent the development of neural tube defects, which can lead to hydrocephalus.

Treating hydrocephalus

Treatment of hydrocephalus depends on its cause and severity. 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 the shunt becomes infected or 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 past the obstruction.

In some cases, surgeons may recommend shunt placement for congenital hydrocephalus while the fetus is still inside the mother's womb (uterus).

When to call a professional

Make an appointment to arrange prenatal care with an obstetrical provider if you become pregnant. Call your doctor if you or your child develops symptoms of hydrocephalus or has a severe head injury.

Prognosis

The outlook depends on the cause of hydrocephalus, and usually is better if the problem is diagnosed and treated early. If hydrocephalus gets worse rapidly or lasts a long time, it can cause brain damage and death.

Children with hydrocephalus are more likely to have various developmental disabilities. Even after treatment, many children with hydrocephalus have seizures, impaired intelligence, memory problems, and vision difficulties, including strabismus (abnormally aligned eyes). Children with hydrocephalus also may enter puberty earlier than normal.

With appropriate treatment, most infants with hydrocephalus survive and approximately one-third have normal cognitive function.