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Hydrocephalus is a condition in which excess fluid builds up in your brain. The word "hydrocephalus" comes from the roots "hydro" meaning "water" and "cephalus" meaning "head." The fluid that accumulates is cerebrospinal fluid (CSF), a fluid that normally surrounds your brain and spinal cord.

In hydrocephalus too much fluid builds up, causing abnormal enlargement of the cavities in the brain (ventricles) that contain CSF. Too much CSF in the ventricles can put increased pressure on the brain, potentially damaging the brain.

Hydrocephalus can be present at birth or you can develop it later. The outlook for people with hydrocephalus varies depending on how soon the condition is diagnosed, whether any other disorders are present and whether treatment is successful. With no treatment, hydrocephalus is nearly always fatal.

Age, how far the disease has progressed and how well a person can tolerate increased cerebrospinal fluid pressure all affect the signs and symptoms. Babies may better tolerate increased CSF pressure because the bones of their skulls haven't completely fused together, and thus their skulls have more flexibility to handle the pressure.

In infants, common signs and symptoms of hydrocephalus include:

• An unusually large head
• A rapid increase in the size of the head
• A bulging "soft spot" on the top of the head (anterior fontanel)
• Vomiting
• Sleepiness
• Irritability
• Seizures
• Eyes fixed downward (sunsetting of the eyes)
• Developmental delay

In older children and adults, common signs and symptoms of hydrocephalus include:

• Headache followed by vomiting
• Nausea
• Blurred or double vision
• Eyes fixed downward (sunsetting of the eyes)
• Problems with balance, coordination or gait
• Sluggishness or lack of energy
• Slowing or regression of development
• Slowed development or loss of development
• Memory loss
• Urinary incontinence
• Irritability
• Changes in personality

Hydrocephalus produces different combinations of these signs and symptoms, depending on its cause, the person's age and similar factors. For example, a condition known as normal pressure hydrocephalus, which mainly affects older people, typically starts with difficulty walking. Urinary incontinence often develops, along with a type of dementia marked by slowness of thinking and information processing.

Hydrocephalus can be present at birth (congenital hydrocephalus) or you can develop it later (acquired hydrocephalus). Hydrocephalus results when the flow of cerebrospinal fluid is disrupted or when your body doesn't absorb CSF properly. CSF provides a number of important functions, including acting as a cushion to protect your brain and bringing nutrients to your brain.

Inside your brain are four ventricles. CSF flows through the ventricles by way of channels that connect one ventricle to another. Once CSF passes through the ventricles, it flows into closed spaces (cisterns) at the base of your brain. Eventually, the CSF is absorbed into your bloodstream. Keeping the production, flow and absorption of CSF in balance is important to maintaining normal pressure inside your skull.

Defective absorption of CSF causes normal pressure hydrocephalus, seen most often in older people. In normal pressure hydrocephalus, excess CSF enlarges the ventricles but does not increase pressure on the brain. Normal pressure hydrocephalus may be the result of injury or illness, but in most cases the cause is unknown.

The main causes
The causes of hydrocephalus fall into two main categories:

• Obstructive (noncommunicating). This type of hydrocephalus results from an obstruction within the ventricular system of the brain that prevents CSF from flowing or "communicating" normally within the brain. Aqueductal stenosis, a narrowing of a channel in the brain that connects two ventricles, is one of the most common types of obstructive hydrocephalus.
• Nonobstructive (communicating). This type of hydrocephalus results from problems with the production or absorption of CSF. A common cause is bleeding into the subarachnoid space in the brain (subarachnoid hemorrhage).

Doctors don't completely understand the specific causes of hydrocephalus. For congenital hydrocephalus, the causes may be genetic disposition or a developmental problem. The most common developmental problems that may lead to hydrocephalus include failure of the tissue surrounding the spinal cord to close properly (spina bifida) and herniation of the brain (encephalocele). For acquired hydrocephalus, the cause may be a disease or condition such as encephalitis, meningitis or a brain tumor that causes blood vessels in the brain to rupture and bleed. Or the cause may be a head injury.

Premature infants have an increased risk of intraventricular hemorrhage in which severe bleeding within the ventricles of the brain can lead to hydrocephalus. Other problems that can occur during pregnancy may increase an infant's risk of developing hydrocephalus, including intrauterine infection or a disorder involving incomplete closure of an infant's spinal column (myelomeningocele).

Congenital or developmental defects can increase older children's risk of hydrocephalus. Lesions or tumors of the brain or spinal cord, central nervous system infections, bleeding in the brain, and severe head injury also can increase the risk of hydrocephalus.

If you notice any of the signs or symptoms of hydrocephalus, call your child's doctor. A high-pitched cry, problems with sucking or feeding, fever, acting lethargic, exhibiting an unwillingness to bend or move the neck or head, breathing difficulties and seizures are all reasons to seek immediate medical care by calling 911 or other emergency help or by going to the emergency room.

An older adult with walking difficulties that can't be attributed to arthritis or injury should have a complete physical and neurological exam.

In addition, seek emergency medical care if you or your child experiences a severe head injury. If you become pregnant, talk with your doctor to begin receiving proper prenatal care.

Diagnosing congenital hydrocephalus
Your doctor may diagnose congenital hydrocephalus in your unborn child during a routine prenatal ultrasound, but it's often discovered during infancy or early childhood. Your doctor may suspect hydrocephalus before other signs and symptoms appear if your infant has a large head that seems to be rapidly increasing in size. If the soft spot on your infant's head is still open, an ultrasound of the head can distinguish between a normal large head (macrocephaly) and hydrocephalus. If the results of the ultrasound are abnormal, your infant will need further evaluation.

Diagnosing acquired hydrocephalus
The evaluation of a child or an adult who develops signs or symptoms of hydrocephalus begins with a careful medical history and a physical and neurological examination. X-rays, a computerized tomography (CT) scan or a magnetic resonance imaging (MRI) scan can provide detailed pictures of the brain. If these pictures reveal hydrocephalus or other abnormalities, referral to a brain surgeon (neurosurgeon) for further evaluation and treatment is likely.

The severity of hydrocephalus depends on the time of onset and whether the disease is progressive. If the condition is well advanced at birth, major brain damage and physical disabilities are likely. In less severe cases, with proper treatment, it's possible to have a nearly normal life span and intelligence.

Other complications of hydrocephalus include:

• Intellectual impairment
• Neurological damage, such as decreased function, movement or sensation
• Problems with the artificial CSF drainage channel (surgical shunt), such as a blockage or kinking of the shunt tubing
• Infection at the site of the shunt

The goal of treatment is to re-establish the balance between cerebrospinal fluid production and reabsorption.

Shunt is common approach
Doctors most often treat hydrocephalus with surgery to insert a system to divert the CSF. This system, called a shunt system, consists of a flexible silicone rubber tube (shunt) and a valve. This artificial channel allows CSF to flow away from the brain to elsewhere in the body, where it can be absorbed.

One end of the channel begins inside one of the ventricles in the brain. At the other end of the channel, CSF fluid may drain into the abdominal (peritoneal) cavity. In this case, the shunt is called a ventriculoperitoneal shunt. Or the fluid may sometimes be drained into a chamber of the heart, in which case the shunt is called a ventriculoatrial shunt. A valve along the channel serves to keep the flow going in the right direction and at the proper rate.

Sometimes, a medication such as acetazolamide (Diamox) or furosemide (Lasix) is used to temporarily reduce pressure from excess CSF. Lumbar puncture (spinal tap), a procedure used to measure CSF pressure and remove small samples of CSF for laboratory testing, is sometimes also used to relieve some of the extra pressure.

Complications of shunts
A successful shunt system allows an infant's head size to become normal and relieves signs and symptoms in older children and adults. Shunt tubes may require replacement as a child grows. Successful shunts usually are maintained for life, but there can be complications.

Mechanical failure, infections and obstructions are possible complications. Sometimes, the tube needs to be lengthened or replaced. Shunt systems require monitoring and regular medical follow-up. When complications happen, a shunt usually requires some type of revision.

A shunt system that isn't operating correctly can result in either too much or too little drainage of CSF. If too much drainage occurs, the ventricles can collapse. When this happens, blood vessels can tear, causing blood to collect just below the lining of the brain, a condition known as subdural hematoma. If too little drainage occurs, the signs and symptoms of hydrocephalus return or remain.

Infections from a shunt may cause a low-grade fever, sore muscles in your shoulder or neck, and redness or tenderness in the area of the shunt.

Shunting sometimes fails to relieve the symptoms of normal pressure hydrocephalus. When a shunt does help people with this condition, the improvement is often temporary.

Another treatment option
An alternative procedure for some people with hydrocephalus is called ventriculostomy. Doctors may use this procedure when there's an obstruction of flow between ventricles. In the procedure, your doctor makes a hole in the bottom of the third ventricle. The procedure uses a small camera to help your doctor locate the correct place to make the hole. This lets CSF flow toward the base of the brain, where normal absorption occurs.

Treatment for hydrocephalus can be lifesaving and life sustaining. Lifelong follow-up examinations are needed to evaluate changes in developmental, intellectual, neurological and physical impairments and to maintain proper functioning of a shunt system.

Protecting the head of your infant or child from injury by handling your child carefully may help prevent the development of hydrocephalus. Prompt treatment of infections such as meningitis and other disorders associated with hydrocephalus may reduce the risk of developing the disease. If you're pregnant, you may reduce the risk of hydrocephalus in your unborn baby by taking precautions to reduce the likeliness of premature birth.

With the help of rehabilitation therapies and educational interventions, many people with hydrocephalus live with few limitations. Public health providers, social services and local agencies can provide you with emotional support and assist with the care of a child with hydrocephalus. Local support groups for people with hydrocephalus and their families may be available. Hospitals often sponsor these groups. Doctors and nurses also may be able to make recommendations on where to find emotional support.