None — Hydrocephalus The brain and spinal cord are surrounded by a clear, watery fluid, called cerebrospinal fluid (CSF). The fluid, produced in the ventricles (spaces in the brain), serves three main purposes: (1) it acts as a shock absorber, keeping the brain floating within the skull, (2) it brings nutrients to the brain and takes away waste products, and (3) it helps the skull and spine compensate for changes in blood volume in the brain.
Normally CSF is continually produced, flowing through the ventricles and exiting into tiny reservoirs at the base of the brain. If CSF is produced too rapidly, or if it can't be absorbed fast enough, the amount of fluid in the ventricles increases. This is called, hydrocephalus. Since the skull can only hold a finite amount of mass, the extra fluid causes the ventricles to enlarge, putting pressure on the surrounding brain tissue. This pressure can damage the nerve cells of the brain.
Normal Pressure Hydrocephalus Normal pressure hydrocephalus (NPH) is an abnormal accumulation of cerebrospinal fluid caused by a blockage in the outflow area. Since the fluid can't drain, it accumulates inside the ventricles. Spinal fluid pressure is often normal or near normal, but can sometimes fluctuate between high, normal and low.
People with NPH have a classis triad of symptoms affecting gait, bladder control and cognitive processes. Gait problems can range in severity and is often characterized by a slow, shuffle-like walk and balance problems. Some patients say their feet feel like they are "stuck" to the floor. Bladder control problems may include a frequent need to urinate, urinary urgency and incontinence. Cognitive problems range from inability to pay attention and slowed reaction time to inappropriate responses, loss of interest in activities, forgetfulness and memory loss.
Researchers estimate that NPH accounts for about 5 percent of all cases of dementia in the U.S. It's most commonly seen in older people. Risk factors include: subarachnoid hemorrhage (a type of stroke), head injury, brain infection, tumor or brain surgery complications. In many cases, the cause of NPH isn't known.
Diagnosis and Treating NPH Diagnosis of NPH can be tricky. UCLA Neurosurgeon, Marvin Bergsneider, M.D., says many of the symptoms overlap those of other common conditions in the elderly, like Alzheimer's and Parkinson's. However, brain scans of patients with NPH will show the characteristic enlargement of the brain's ventricles (from the excess fluid). The scans and a careful review of the onset and characteristics of the symptoms help differentiate NPH from other possible diagnoses.
Another big difference between the conditions is that people with NPH often respond very well to treatment. The most common method of treatment for NPH is surgical placement of a device called a shunt. The shunt system consists of a catheter and valve. One end of the catheter is placed within a ventricle or outside the CSF space in the spinal cord. The other end of the catheter is placed in another area of the body, like the abdominal cavity. This system allows the CSF fluid in the brain to drain through the catheter and be absorbed elsewhere in the body. A one-way valve regulates the amount of flow and keeps the CSF fluid flowing in the right direction.
Bergsneider says once a shunt is placed, many people with NPH begin to recover. Patients who have a shunt need regular medical check-ups to ensure the device continues to work properly and to be monitored for any signs of infection.
The Alzheimer's Association reports that in patients with NPH, shunting is most likely to help restore gait and urinary continence, and less likely to produce significant improvement in cognitive problems. The organization also cautions that although NPH may be confused for other causes of dementia, few people with Alzheimer's or Parkinson's actually have NPH and thus, would not benefit from a shunt.
Research compiled and edited by Barbara J. Fister
AUDIENCE INQUIRY For information on normal pressure hydrocephalus (NPH): Alzheimer's Association Hydrocephalus Association National Institute of Neurological Disorders and Stroke
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