The intention of this page is to provide information to patients, family members, caregivers and friends on the subject of hydrocephalus. The information provided is a general overview of the diagnosis and treatment of hydrocephalus and other conditions associated with hydrocephalus.
The term hydrocephalus is derived from the Greek words "hydro," meaning water, and "cephalus," meaning head. As its name implies, hydrocephalus is a condition in which the primary characteristic is excessive accumulation of fluid in the brain. Although hydrocephalus was once known as "water on the brain," the "water" is actually cerebrospinal fluid (CSF), a clear fluid surrounding the brain and spinal cord. The excessive accumulation of CSF results in an abnormal dilation of the spaces in the brain called ventricles. This dilation causes potentially harmful pressure on the tissues of the brain.
Cerebrospinal Fluid Dynamics
The ventricular system is made up of four ventricles connected by narrow pathways. Normally, CSF flows through the ventricles, exits into cisterns (closed spaces that serve as reservoirs) at the base of the brain that bathes the surfaces of the brain and spinal cord, and then is absorbed into the bloodstream.
Purpose of Cerebrospinal Fluid
CSF has three important life-sustaining functions:
- Helps the brain tissue remain buoyant acting as a cushion or "shock absorber"
- Delivers nutrients to the brain and removes waste
- Flows between the head and spine to adjust with changes in intracranial blood flow within the brain
Production and Absorption of Cerebrospinal Fluid
The balance between production and absorption of CSF is critically important. Ideally, the fluid is almost completely absorbed into the bloodstream as it circulates; however, there are circumstances which, when present, will prevent or disturb the production or absorption of CSF, or inhibit its normal flow. When this balance is disturbed, hydrocephalus is the result.
- CSF circulation is intact, but the absorption into arachnoid granulations is blocked
Non-communicating or Obstructive
- Circulation of CSF is blocked somewhere between the lateral, third, and/or fourth ventricles
Normal Pressure Hydrocephalus (NPH)
- IVP (Intraventricular Pressure) is at “normal levels”
- Typically affects elderly patients
- Symptoms: Incontinence, Dementia, Gait Ataxia (loss of balance, shuffling walk)
- Diagnosed: History, imaging, spinal tap
What causes hydrocephalus?
The causes of hydrocephalus are not all well understood. Hydrocephalus may result from developmental disorders such as those associated with neural tube defects including spina bifida and encephalocele. Other possible causes include complications of premature birth such as intraventricular hemorrhage, diseases such as meningitis, tumors, traumatic head injury, or subarachnoid hemorrhage blocking the exit from the ventricles to the cisterns and eliminating the cisterns themselves.
What are the symptoms of hydrocephalus?
Symptoms vary with age, disease progression and individual differences in tolerance to CSF. For example, an infant's ability to tolerate CSF pressure differs from an adult's. The infant skull can expand to accommodate the buildup of CSF because the sutures (fibrous joints that connect the bones of the skull) have not yet closed. In infancy, the most obvious indication of hydrocephalus is the rapid increase in head circumference or an unusually large head size. Other symptoms may include vomiting, sleepiness, irritability, downward deviation of the eyes (also called "sun setting") and seizures.
Older children and adults may experience different symptoms because their skulls cannot expand to accommodate the buildup of CSF. Symptoms may include:
- Vomiting and/or nausea
- Papilledema (swelling of the optic disk which is part of the optic nerve)
- Visual disturbances: blurred vision, diplopia (double vision), and sun setting of the eyes
- Difficulty with balance, poor coordination, and gait disturbance
- Urinary Incontinence
- Slowing or loss of development
- Lethargy, drowsiness, irritability and or other changes in personality or cognition including memory loss
Normal Pressure Hydrocephalus
Symptoms of NPH include progressive mental impairment and dementia, problems with walking, and impaired bladder control leading to urinary frequency and/or incontinence. They may have a general slowing of movements or may complain that their feet feel "stuck." Because these symptoms are similar to other disorders such as Alzheimer's disease, Parkinson's disease, and Creutzfeldt-Jakob disease, NPH is often misdiagnosed. Many cases go unrecognized and are never properly treated. Doctors may use a variety of tests, including brain scans (CT and/or MRI), a spinal tap or lumbar catheter, intracranial pressure monitoring, and neuropsychological tests to help them diagnose NPH and rule out other conditions.
The symptoms described in this section account for the most typical ways in which progressive hydrocephalus manifests. It is, however, important to remember that symptoms vary significantly from individual to individual.
Implanting a Shunt System
Implanting of a shunt system is a relatively short surgical procedure. The procedure is performed in an operating room using sterile techniques under general anesthesia. A neurosurgeon will perform the procedure where he or she will make an incision on the scalp and a small hole made in the skull. This hole will allow access to the ventricle where the catheter will be placed. This catheter will be connected to the valve, which will allow the CSF to drain away from the brain. Lastly, another small incision is made in the abdomen to pass the end of the catheter into the abdominal cavity. Once all of the connections are made, the shunt system will automatically open to drain excess CSF whenever the pressure in the skull exceeds the opening pressure set on the valve.
Potential Complications of a Shunt System
Shunt systems are not perfect devices. Complications may include mechanical failure, infections, obstructions and the need to lengthen or replace the catheter. Generally, shunt systems require monitoring and regular medical follow up. When complications do occur, usually the shunt system will require some type of revision.
Over-draining of Cerebrospinal Fluid
Some complications can lead to other problems, such as over-draining or under-draining. Over-draining occurs when the shunt allows CSF to drain from the ventricles more quickly than it is produced. This over draining can cause the ventricles to collapse, tearing blood vessels and causing headache, hemorrhage
(subdural hematoma), or slit-like ventricles (slit ventricle syndrome).
Under-draining of Cerebrospinal Fluid
Under-draining occurs when CSF is not removed quickly enough and the symptoms of hydrocephalus recur. In addition to the common symptoms of hydrocephalus, infections from a shunt may also produce symptoms such as a low-grade fever, soreness of the neck or shoulder muscles, and redness or tenderness along the shunt tract. When there is reason to suspect that a shunt system is not functioning properly (for example, if the symptoms of hydrocephalus return), medical attention should be sought immediately.
The prognosis for patients diagnosed with hydrocephalus is difficult to predict, although there is some correlation between the specific cause of the hydrocephalus and the patient's outcome. Prognosis is further complicated by the presence of associated disorders, the timeliness of diagnosis and the success of treatment. The degree to which decompression (relief of CSF pressure or build-up) following shunt surgery can minimize or reverse damage to the brain, is not well understood.
Prognosis of Progressive Hydrocephalus
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 benefit from rehabilitation therapies and educational interventions and go on to lead normal lives with few limitations. Treatment by an interdisciplinary team of medical professionals, rehabilitation specialists, and educational experts is critical to a positive outcome. Left untreated, progressive hydrocephalus is, with rare exceptions, fatal.
Prognosis of Normal Pressure Hydrocephalus
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 from person to person, some people recover almost completely after treatment and have a good quality of life. Early diagnosis and treatment improves the chance of a good recovery.
* Information provided by the National Institute of Neurological Disorders and Stroke (NINDS).