Normal Pressure Hydrocephalus -- Overview, Incidence an...

Normal Pressure Hydrocephalus -- Overview, Incidence and Prevalence

Overview

Normal pressure hydrocephalus (NPH) is a condition that involves the build-up of fluid in the brain. Normally, a fluid called cerebrospinal fluid (CSF) circulates around the brain and spinal cord. This fluid cushions, cleanses, and brings nutrients to the cells in the brain and spine. CSF is produced in small, hollow spaces within the brain called ventricles. For people in good health, excess CSF normally drains away into the bloodstream as fresh CSF is produced.

When cerebrospinal fluid does not drain properly, the cerebrospinal fluid builds up in the ventricles and NPH can occur. This build up puts pressure on the brain, interfering with healthy brain function. NPH most commonly affects the areas of the brain that control leg movement, bladder function, and cognitive abilities such as problem solving, speaking, and remembering.

"Hydrocephalus" was once called "water on the brain," but we now know that the water is CSF. The term "normal pressure" refers to the fact that this type of hydrocephalus, which generally develops slowly, has a lower CSF-pressure than other types of hydrocephalus. Normal pressure hydrocephalus occurs mainly in people over the age of 60 and symptoms may be mistaken for other disorders, such as Parkinson's disease, Alzheimer's disease, dementia, or Creutzfeldt-Jakob disease. However, with proper diagnosis and treatment many of the symptoms of NPH can be controlled or greatly reduced. In some cases, a nearly complete recovery is possible.


Incidence and Prevalence

There are no definitive statistics for the prevalence of NPH in the United States at this time. Some experts estimate that up to 750,000 Americans may have NPH. Estimates also suggest that NPH may be the cause for up to 5% of dementia cases. To date, the numbers of men and women who have NPH are relatively equal in number, and there is no correlation between NPH and race. In general, NPH affects patients over the age of 50, with most patients being age 60 or older.


Risk Factors and Causes

Normal pressure hydrocephalus (NPH) can develop after a stroke, head injury, brain surgery, meningitis, or any disorder that causes bleeding around the brain. The presence of a brain tumor may also cause NPH. In most cases, however, the cause of NPH is unknown.


Signs and Symptoms

In general, a combination of the following symptoms may indicate normal pressure hydrocephalus (NPH):

* Frequent urination or the urgent need to urinate
* Gait disturbance (difficulty walking)
* Mild dementia (a progressive impairment of mental abilities)

Additional symptoms of NPH, such as headache, nausea, and vision problems, can also occur due to the increased pressure on the brain.

The first noticeable symptom of NPH is often a gait disturbance, or having trouble walking or balancing. Commonly, people with NPH may walk with slow, short, shuffling steps and keep a wide stance (for balance) when standing still, or even when walking. People with NPH may also feel as if they cannot lift their foot from the floor. They may feel weak and unsteady in their legs, have a hard time getting started walking, and experience sudden falls.

Signs of dementia often associated with normal pressure hydrocephalus may include having trouble remembering (memory loss), being unusually slow to speak or to understand what is being spoken, having difficulties with tasks that were once routine, and a reduced attention span. The person may also have difficulties with basic reasoning and problem-solving. A general lack of interest in life, as well as changes in behavior and mood, may also accompany NPH.

People in the early stages of NPH may also feel a frequent or urgent need to urinate. Later, as the effects of NPH worsen, these urinary symptoms may progress to incontinence, or the inability to control the flow of urine. In fact, incontinence is often associated with more advanced cases of NPH.

Early signs of normal pressure hydrocephalus may go unnoticed because they can seem subtle, or insignificant. For example, some people with NPH think signs of urinary difficulties are not worth noting and thus neglect to report them to their healthcare provider. People often associate the symptoms of NPH with the typical signs of aging, so the early warning signs for NPH may simply be ignored or overlooked. However, the good news is that those who are diagnosed early on generally have a higher success rate for treatment and for a much-improved quality of life. If you notice any of the above signs in yourself or a family member, contact your healthcare provider.


Diagnosis

Normal pressure hydrocephalus (NPH) can be difficult to diagnosis and a thorough and accurate diagnosis is essential for successful treatment. Several different diagnostic procedures and tests are used to diagnose the condition. A patient history and physical examination is generally considered the first step.

The goal is to document symptoms—and when they began—in order to help determine the patient's current condition. As part of this process, it's important to review the medical history of both the patient and his or her family.

Neuropsychological tests consist of a series of questions and tasks that can help to determine the patient's cognitive abilities (thinking and memory) and the extent of any brain impairment. These tests may be recommended before as well as after a lumbar puncture. Neuropsychological tests can also be helpful in determining whether shunt surgery may be a useful treatment option.

A CT scan (computed tomography) of the head or brain is a painless and low-risk diagnostic imaging test. A CT scan provides an image of the brain, similar to an x-ray. In some cases, a contrast agent (dye) is used to help make the images easier to read. A CT scan can help detect physical and structural abnormalities, such as areas of the brain that may be affected by the build-up of CSF pressure. In general, a CT scan is an outpatient procedure.

An MRI scan (magnetic resonance imaging) of the head or brain is another painless and low-risk diagnostic imaging test. MRI uses a strong magnetic field and radio waves to create a very detailed picture of the brain. In general, a MRI is an outpatient procedure, with the actual procedure taking about 30 to 90 minutes to complete. In some cases, the patient is given a sedative to help relieve anxiety and stress about this test. Patients with any metal inside their bodies or certain implanted devices like pacemakers may not be able to undergo MRI.

A lumbar puncture (or spinal tap) may be used to both measure the pressure of the CSF and to test whether reducing the CSF pressure actually relieves symptoms. First, a tiny sensor may be inserted in the skull to measure pressure on the brain. Then, during the actual lumbar puncture procedure, a catheter (small, flexible tube) is inserted in the lower back. The catheter allows a small amount of fluid to drain from the spinal column. The patient is then checked to see if symptoms have improved.

Risks from a lumbar puncture include headache, bleeding, and infection. Headache may occur from a couple of hours to 1 day following the lumbar puncture and is less common when the patient remains lying flat for 1–3 hours after the procedure. Patients may remain hospitalized for observation for a few hours to a few days following this test.

Other diagnostic tests may also be used to diagnose normal pressure hydrocephalus (NPH). For example, cisternography is a test that examines the rate of absorption of the CSF over a period of time. This test involves the injection of a radioactive isotope into the spinal column, usually in the lower back.

It is important to discuss possible risks and benefits with your healthcare provider before undergoing any diagnostic procedure and to adhere to all preparation and follow-up instructions. Any unusual or severe side effects, such as headache or nausea, should be reported to your healthcare provider immediately.


Treatment

Normal pressure hydrocephalus cannot always be cured. As a chronic condition, however, proper treatment can make a significant improvement in the patient's quality of life.


Medications

Currently, there are no medications to directly treat NPH.


Surgery

Shunt surgery is the most common treatment for the symptoms of normal pressure hydrocephalus. However, not all patients with NPH are suitable candidates for shunt surgery. Proper diagnostic testing for NPH is essential to determine if a patient is a suitable candidate for shunt surgery.

Shunt surgery is a surgical procedure in which a neurosurgeon implants a very thin tube that leads from the enlarged ventricle in the brain into the patient's abdomen (the peritoneal cavity). Attached to the tube is a small valve that opens when CSF pressure builds up. The tube and valve transfer the excess CSF fluid from the enlarged ventricle in the brain into the abdomen. The excess CSF is then absorbed harmlessly into the bloodstream. As part of the patient's follow-up care, the flow of CSF is monitored to see if adjustments to the valve are needed. Newer valve technology allows the neurosurgeon to adjust the valve externally, so additional surgery is not required.

Endoscopic ventriculostomy also may be performed to treat NPH. In this procedure, a hole is created in the bottom, or floor, of the ventricle so that excess CSF can drain. However, this surgery is relatively new, is less commonly used, and, at this time, is associated with greater risks.

As with any surgical procedure, it is important to discuss all possible risks and benefits with your healthcare provider beforehand, and to follow all instructions for before and after the surgery. Unusual or severe side effects following surgery should be reported to your healthcare provider immediately.


Other Therapies

In general, patients with normal pressure hydrocephalus who do not undergo shunt surgery require daily care by a family member or professional caregiver. NPH patients who are advised not to have shunt surgery may experience temporary relief through periodic lumbar punctures. Other treatments may include therapies for symptom relief.


Follow-up

Patients diagnosed and treated for NPH, with or without shunt surgery, should be under the regular care of a neurologist or neurosurgeon and should see their primary healthcare provider regularly.


Prognosis

Statistics vary regarding the success of shunt surgery. Not all patients with normal pressure hydrocephalus experience significant improvements from shunt surgery. When the cause of NPH has been determined, however, shunt surgery has a high success rate.

Untreated, NPH symptoms will generally worsen and likely lead to death over time. Individuals who are advised not to undergo shunt surgery may see improvements with periodic lumbar punctures and/or other treatments. When shunt surgery is successful, patients experience a reversal or lessening of their symptoms and an improved quality of life.


Prevention

Although the cause of many cases of normal pressure hydrocephalus is unknown, commonsense steps can help reduce your risks of a head injury, which can result in NPH. Always wear your safety belt when driving and insist that all passengers wear theirs. Always wear a safety helmet when biking, skating, roller-blading, skiing, or snowboarding.

Not smoking, eating a healthy diet, and being physically active also helps to reduce the risks of high blood pressure, heart disease, diabetes, and stroke all conditions that can lead to NPH.