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Hydrocephalus: Frequently Asked Questions

What is Hydrocephalus?
Hydrocephalus is a condition characterized by an abnormal accumulation of cerebrospinal fluid (CSF) within the ventricles of the brain. CSF surrounds the brain and spinal cord. When the circulatory path of the CSF is blocked, fluid begins to accumulate, causing the ventricles to enlarge and the pressure inside the head to increase, resulting in hydrocephalus.

Learn more about hydrocephalus.

What is Normal Pressure Hydrocephalus?
Normal pressure hydrocephalus (NPH) is an accumulation of CSF that causes the ventricles in the brain to become enlarged, sometimes with little or intermittent increases in intracranial pressure (ICP). It is most commonly seen in older adults, and is accompanied by some or all of the following symptoms: gait disturbance, mild dementia and impaired bladder control.

What Causes Normal Pressure Hydrocephalus?
The majority of cases of NPH have no known cause. It can develop as the result of a head injury, cranial surgery, subarachnoid hemorrhage, tumor or cysts, as well as subdural hematomas, , meningitis and other brain infections.

What are the Symptoms of Hydrocephalus?
NPH is usually characterized by a triad of symptoms: complaints of gait disturbance (difficulty walking), mild dementia and impaired bladder control. These symptoms may not occur all at the same time, and sometimes only one or two symptoms are present. The triad of symptoms is often associated with the aging process and a majority of the NPH population is older than 60 years. The cognitive deficits of NPH can resemble those associated with Alzheimer’s and the gait disturbances of NPH can look similar to those of Parkinson’s disease. In some cases NPH can occur in combination with these diseases. Symptoms of hydrocephalus seem to progress with time, but the rate is variable. As a general rule, the earlier the diagnosis, the better the chance for successful treatment; however some patients who have had symptoms for years may improve with treatment.

How is Normal Pressure Hydrocephalus Diagnosed?
Once NPH is suspected by a primary physician, one or more of the following tests are usually recommended to confirm the diagnosis and assess the person’s candidacy for shunt treatment. It is important that at this point a neurosurgeon and/or neurologist become part of the medical team. Their involvement is helpful not only in interpreting test results and selecting likely candidates for shunting, but also in discussing the actual surgery and follow-up care as well as expectations and risks of surgery.

  • Clinical Exams – consists of an interview and or a physical/neurologic examination
  • Brain images to detect enlarged ventricles
    • MRI
    • CT or CAT scan
  • CSF tests to predict shunt responsiveness and/or determine shunt pressure
    • Lumbar or spinal tap
    • External lumber drainage
    • Measurement of CSF outflow resistance

What Treatment is Available?
The only available treatment for NPH  is the surgical implantation of a shunt, a device that channels CSF sway from the brain to another part of the body where it can be absorbed. Most shunt systems consist of three components: 

  • A collection catheter situated within the cerebral ventricles
  • A valve mechanism to control how much CFS flows
  • An exit catheter to drain the CSF to another part of the body

After the surgery, all components of the shunt system are entirely under the skin, and nothing is exposed to the outside.

Who is a Likely Candidate for Shunting?
The answer to this question is still uncertain. No one single factor is reliable in predicting success from implantation of a shunt. The following findings are generally associated with a better outcome following shunt placement:

  • The onset of gait disturbance as the first and most prominent symptom
  • A known cause for NPH, such as a trauma or hemorrhage
  • The scan shows the ventricle size to be disproportionately larger than the CSF in the subarachnoid space
  • Removal of spinal fluid via lumbar puncture or lumbar catheter gives dramatic, temporary relief of symptoms
  • ICP or spinal fluid pressure monitoring shows an abnormal range or pattern of spinal fluid pressure or an elevated CSF outflow resistance

Although everyone hopes for a complete recovery, it is not often seen. Many individuals and their families are satisfied when shunt surgery results in reduced disability or dependence than he or she had before surgery, or prevention of further neurological deterioration. People with NPH, their families and their physicians need to be supportive and hopeful, but they should also know the possible complications, risks and realities of shunt implantation.

What does a Shunt Operation Entail?
The surgical procedure to implant a shunt usually requires less than an hour in the operating room. The patient generally stays under careful neurological observation for the first 24 hours following the procedure. Patients generally stay in the hospital from one to seven days. Follow-up visits will be necessary to check post-operative status and resolution of symptoms. After surgery, physical therapy, occupational therapy and other rehabilitation strategies may be advised to help patients attain as much resolution of symptoms as possible.

How Successful is Shunting?
The symptoms of gait disturbance, mild dementia and bladder control problems may improve within days of shunt surgery, or may take weeks to months to abate. Other factors that affect the outcome after shunt surgery are the presence of other neurological or medical conditions. The more symptoms are due to NPH, rather than the associated conditions, the greater the likelihood of successful recovery after shunting.

What are the Complications and Risks Involved with Shunting?
The potential complications of shunt surgery include those related to the actual operation, as well as those that may occur days to years later. One of the most common problems with shunt systems is that they can become obstructed; however it can usually be easily fixed and rarely results in serious problems, although further surgery may be necessary. Other common complications include: shunt malfunction; infection at the site of the surgical wound, the shunt or the CSF (meningitis); bleeding into the brain or ventricles; or a seizure. One of the more serious complications that can occur following the insertion of a shunt is a subdural hematoma (blood clot). This risk occurs approximately 5 to 10 percent of the time. Given the potential complications, individuals and their families need to assess their own situation to determine if the possible benefits of surgery outweigh the possible risks.

How can I consult a Johns Hopkins specialist for assessment of possible NPH?
There are several neurologic conditions that can mimic NPH. Obtaining a CT or MRI of the Brain is helpful in narrowing the possibilities and is often the first step in the diagnosis. If the symptoms and scans are consistent with NPH your primary care physician or neurologist can refer you to our center for further assessment. To arrange for a personal appointment to discuss hydrocephalus diagnosis and treatment options with a specialist at the Johns Hopkins Normal Pressure Hydrocephalus Center, please call 410-955-7482. We will need you to fill a detailed questionnaire and review your medical notes and actual scans before your appointment, for optimal assessment at your clinic visit. More information can also be found at

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Maryland Patients

Thank you for your interest in the Hydrocephalus Center at Johns Hopkins. Learn how to request an appointment or refer a patient.

Adult Neurology: 410-955-9441
Pediatric Neurology: 410-955-4259
Adult Neurosurgery: 410-955-6406
Pediatric Neurosurgery: 410-955-7337


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