Hydrocephalus is a brain condition that gets its name from the Greek word for water (meaning "hydro") and head (meaning "cephalus"). It occurs when cerebral spinal fluid (CSF) — the clear, water-like fluid that surrounds and cushions the brain and spinal cord — is unable to drain from the brain. It then pools, causing a backup of fluid in the skull.

Sometimes referred to as "water on the brain," hydrocephalus can cause babies' and young children's heads to swell to accommodate the excess fluid. Older kids, whose skull bones have matured and fused together, experience painful headaches due to increased pressure in the head.

If left untreated, hydrocephalus can lead to brain damage, a loss in mental and physical abilities, and even death. With early diagnosis and timely treatment, however, most children recover successfully.

Causes of Hydrocephalus

When everything is working normally inside the brain, CSF will flow through narrow passageways called ventricles and exit the brain through a small reservoir at the base of the brain called the cistern. CSF is responsible for delivering nutrients to the brain and taking waste away from sensitive areas, where it will eventually be absorbed into the bloodstream.

If a blockage exists in any of the ventricles, CSF backs up and causes an excess of fluid in the brain, or hydrocephalus. This accumulation of fluid can also happen when the choroid plexus (the area of the brain that produces CSF) is in overdrive or if the fluid fails to be properly absorbed by the bloodstream.

When hydrocephalus is present at birth, it can be the result of conditions like spina bifida (where the primary cause is abnormal development of the spinal cord) or aqueductal stenosis (a narrowing of the small passageway, called the "aqueduct of Sylvius," that connects two major ventricles in the brain).

Acquired hydrocephalus is caused by cranial hemorrhage, or bleeding in the brain. This can happen in premature babies or kids who've undergone traumatic head injuries.

But not every case of hydrocephalus is due to the causes mentioned here: Some kids can develop hydrocephalus without a known cause.

Signs in Babies

Symptoms of hydrocephalus vary depending on the age of a child.

Infants and babies under the age of 1 year will appear to have significant swelling of the head. Their skull bones — thin, bony plates that have not yet fused together — are connected by fibrous tissue called sutures. These sutures, or "soft spots," have not yet hardened and therefore stretch and protrude to accommodate the excess CSF.

As a result, a baby with hydrocephalus will appear to have an abnormally shaped head — usually much larger than other babies the same age. Other signs to look for include:

• bulging at the soft spots
• "split" sutures — a gap can be felt between skull bones
• rapid increase in head circumference
• swollen veins that are recognizable to the naked eye
• downward cast of the eyes (called "sunsetting")

Depending on the severity of the condition, kids may also experience sleepiness, irritability, vomiting, and seizures. In extreme cases, a child may also experience "failure to thrive," meaning that he or she might miss growth or developmental milestones or may revert to earlier developmental stages.

Signs in Older Kids

Older children will not have the easily recognizable symptom of an enlarged head because their skull bones have fused together and therefore cannot expand to accommodate the excess fluid.

In these cases, pressure on the brain intensifies and causes severe headaches that may wake a child in the middle of the night or early in the morning. Headaches may be coupled with:

• nausea/vomiting
• sleepiness
• difficulties with balance and motor skills
• double vision
• squinting and/or other repetitive eye movements
• seizures

Changes in personality, loss of new developmental abilities (like speaking or walking), and memory loss may also occur in more advanced cases.

Diagnosis

A child who shows any of the signs and symptoms mentioned above should be evaluated by a doctor right away. The doctor will perform examinations, which may include a medical history and diagnostic imaging — like ultrasound, CT (computed tomography), or MRI (magnetic resonance imaging) — to get a clear picture of the inside of the brain.

During imaging, a child will lie still on a table for a few seconds while a machine passes over his or her body, emitting very low (and harmless) frequencies of radiation or sound waves.

Shunt Procedure

If hydrocephalus is diagnosed, treatment will depend on the age of the child, the cause of the cerebral spinal fluid build-up (whether from a blockage, overproduction of fluid, or another problem), and the child's overall health.

Shunt procedures, which have been the standard of care for decades, involve surgically implanting one end of a catheter (flexible tube) into a ventricle of the brain and placing the other end in the abdominal cavity, chambers of the heart, or space around the lungs where fluid is drained and absorbed by the bloodstream. A valve in the shunt system regulates flow to prevent over-draining and under-draining.

While shunting is often an effective treatment for hydrocephalus, there is a high chance of failure and complications. About 30% of shunts will stop working within the first year, with about 5% failing in each subsequent year, causing symptoms to recur. A child will need to have surgery to correct the problem — whether it requires replacing a catheter or valve or replacing the entire shunt. Most kids who undergo shunting will require subsequent operations over their lifetimes to regulate shunt problems.

Infections are another side effect of shunting, and occur in 5%-10% of shunt operations. Kids will develop typical signs of infection, like fever and neck stiffness, and may feel tenderness along the shunt or belly pain. Most infections develop within the first several months after a shunt procedure and require temporary removal of the device while a child receives intravenous antibiotics for up to 2 weeks.

Ventriculostomy

A second, increasingly more common treatment for hydrocephalus is an endoscopic third ventriculostomy. During this procedure, a small opening is made in the bottom of the third ventricle (one of four ventricles in the brain) to allow fluid to exit the brain.

This minimally invasive approach involves placing an endoscope (small lighted camera) inside the brain to provide surgeons with a view of the surgical site on a computer monitor. Then, using very small instruments, the doctor will make a tiny hole in the bottom of the third ventricle, where a thin membrane separates the inside and outside of the brain. This new "evacuation route" permits fluid to drain normally into the spaces outside the brain while bypassing any obstructions that are causing a backup, so the body can reabsorb the CSF back into the bloodstream as it normally would.

When deemed appropriate, third ventriculostomies are the procedure of choice for kids older than 6 months of age due to a higher efficacy rate and lower risk of infection than shunting. Those who undergo the procedure have up to a 90% chance of long-term success, with little need for follow-up procedures.

Third ventriculostomies also have shown promise in newborns and may be offered as a treatment to these younger patients in the near future.

Outlook

With timely treatment, many kids with hydrocephalus go on to lead normal lives.

Those with more complex medical problems, like spina bifida or bleeding in the brain from prematurity, may experience a higher rate of complications due to their underlying medical conditions. In these kids, early intervention greatly improves the chances of recovery.

Reviewed by: Joseph H. Piatt, MD
Date reviewed: October 2011
Originally reviewed by: Jeffrey W. Campbell, MD