Have you ever heard of a condition referred to as “water on the brain” and wondered what it meant? The condition is hydrocephalus. Hydrocephalus is derived from the Greek words "hydro" meaning water and "cephalus" meaning head. Although hydrocephalus may be known to many as “water on the brain," the "water" is actually cerebrospinal fluid (CSF) — a clear fluid that surrounds the brain and spinal cord. Excessive accumulation of CSF results in an abnormal widening of spaces in the brain called ventricles, and the widening can create potentially harmful pressure on the tissues of the brain.

Hydrocephalus results from a lack of proper fluid absorption, blockage of brain and spinal fluid flow, or overproduction of the CSF that is found inside the ventricles, or fluid-filled areas, of the brain. This may result in a buildup of fluid that can increase pressure inside of the head and dangerously expand the head to a larger-than-normal appearance. Hydrocephalus occurs in approximately one out of 500 births and is also at risk of occurring in babies born with the most common disability at birth, spina bifida. The primary reasons why hydrocephalus occurs include blockage of the CSF flow inside of the head, problems with the body absorbing the CSF and overproduction of the CSF.

A flow system inside the brain is made up of four ventricles connected by narrow passages. Normally, brain and spinal fluid flows through these” ventricles,” exits into cisterns (closed spaces that serve as reservoirs) at the base of the brain, bathes and cushions the surfaces of the brain and spinal cord, and then reabsorbs into the bloodstream. However, in hydrocephalus, this system is interrupted causing excess pressure.
CSF has three important life-sustaining functions:

1) to keep the brain tissue buoyant, acting as a cushion or "shock absorber";
2) to act as the vehicle for delivering nutrients to the brain and removing waste; and
3) to flow between the cranium and spine and compensate for changes in intracranial blood volume (the amount of blood within the brain).

The balance between production and absorption of CSF is critical. Because CSF is in constant production, medical conditions that block its normal flow or absorption will result in an over-accumulation of CSF. The resulting pressure of the fluid against brain tissue is what causes hydrocephalus.

Hydrocephalus may occur at birth, as with birth conditions like spina bifida, or acquired later in life. Congenital hydrocephalus is present at birth and may be caused by either events or influences that occur during fetal development or coupled with genetic abnormalities to the brain and spinal development of the baby. Acquired hydrocephalus develops at the time of birth or at some point afterward due to an injury or illness.

Hydrocephalus may also be what’s called communicating or non-communicating. Communicating hydrocephalus occurs when the flow of CSF is blocked after it exits the ventricles. This form is called communicating because the CSF can still flow between the ventricles, which remain open. Non-communicating hydrocephalus, or "obstructive" hydrocephalus, takes place when the flow of CSF is blocked along one or more of the narrow passages connecting the ventricles. One of the most common causes of hydrocephalus comes from the narrowing of a small passage between the third and fourth ventricles in the middle of the brain.

There are two other forms of hydrocephalus which do not fit exactly into the categories mentioned above and primarily affect adults: hydrocephalus ex-vacuo and normal pressure hydrocephalus.

Hydrocephalus ex-vacuo occurs when stroke or traumatic brain injury cause damage to the brain, and rather than swelling occurring, shrinking is evident. Normal pressure hydrocephalus can happen to people at any age, but it is most common among the elderly. It may result from brain hemorrhage, head trauma, infection, tumor, or complications after surgery. However, many people develop normal pressure hydrocephalus even when none of these factors are present for uncertain reasons.

The causes of hydrocephalus are still not totally understood. Hydrocephalus may result from inherited genetic abnormalities or developmental disorders, such as those associated with neural tube impairments, including spina bifida, etc. Other possible causes include complications of premature birth such as hemorrhage inside the ventricles of the brain, diseases such as meningitis, tumors, traumatic head injury, or hemorrhage.

So, what are the symptoms? Symptoms of hydrocephalus vary with age, disease progression, and individual differences in tolerance to the condition. For example, an infant's ability to compensate for increased CSF pressure and enlargement of the ventricles differs from an adult's. The infant skull, since it is still soft and developing, can expand to accommodate the buildup of CSF.

In infancy, the most obvious indication of hydrocephalus is often a rapid increase in the size of the head. Other symptoms may include vomiting, sleepiness, irritability, downward deviation of the eyes, and seizures.

Older children and adults may experience different symptoms because their skulls, which are fully developed and fused, cannot expand to accommodate the buildup of CSF. Symptoms may include headache followed by vomiting, nausea, blurred or double vision, problems with balance, poor coordination, gait disturbance, urinary incontinence, slowing or loss of developmental progress, lethargy, drowsiness, irritability, or other changes in personality or cognition including memory loss.

Symptoms of normal pressure hydrocephalus include, problems with walking, impaired bladder control leading to urinary frequency and/or incontinence, and progressive mental impairment and dementia. An individual with this type of hydrocephalus may have a general slowing of movements or may complain that his or her feet feel heavy or stuck. Because some of these symptoms may also be experienced in other disorders such as Alzheimer's disease, Parkinson's disease, and Creutzfeldt-Jakob disease, normal pressure hydrocephalus is often incorrectly diagnosed and isn’t always properly treated. Doctors may use a variety of tests, including brain scans, such as a CT and/or MRI, a spinal tap or lumbar catheter to monitor spinal fluid levels, intracranial pressure monitoring, and neuropsychological tests, to help them accurately diagnose normal pressure hydrocephalus and rule out other things.

Hydrocephalus is most often treated by surgically inserting a shunt system into the body. This system is like a fluid bypass system that diverts the flow of CSF from the central nervous system to another area of the body where it can be naturally and safely absorbed as part of the normal circulatory process.

The prognosis for individuals diagnosed with hydrocephalus is difficult to predict, although there is some correlation between the specific cause of the hydrocephalus and the outcome. Prognosis is further complicated by the presence of associated disorders, the timing of the diagnosis, and treatment success. Also, there are various ways to treat the condition, from a surgically implanted shunt to medications.

Affected individuals and their families should be aware that hydrocephalus poses risks to both cognitive and physical development. However, many children diagnosed with the disorder can go unaffected if it is caught early enough in some cases. Children may also benefit from rehabilitation therapies and educational interventions and go on to lead healthy, productive lives.

Treatment by an interdisciplinary team of medical professionals, rehabilitation specialists, and educational experts is critical to a positive outcome. Left untreated, though, hydrocephalus can kill, so be watchful of symptoms.

The symptoms of normal pressure hydrocephalus usually get worse over time if the condition is not treated, although some people may experience temporary improvements. While the success of treatment with shunts varies with the individual, some people recover completely and have a good quality of life. Early diagnosis and treatment improves the chance of a good recovery.

The National Institute of Neurological Disorders and Stroke (NINDS) and other institutes of the National Institutes of Health (NIH) conduct research related to hydrocephalus. Much of this research focuses on finding better ways to prevent, treat, and ultimately cure disorders such as hydrocephalus. The NINDS also conducts and supports a wide range of fundamental studies that explore the complex mechanisms of normal and abnormal brain development.

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