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Normal-pressure hydrocephalus consists of difficulty walking, urinary incontinence, and dementia due to an increase in the fluid that normally surrounds the brain.
Normally, the fluid that surrounds the brain and protects it from injury (cerebrospinal fluid) is continuously produced in the spaces within the brain (ventricles), circulates in and around the brain, and is reabsorbed. Normal-pressure hydrocephalus is thought to occur when this fluid is not reabsorbed normally, causing it to accumulate. The amount of fluid in the ventricles increases and the brain is then pushed outward.
Usually, the main symptom is an abnormally slow, unsteady, wide-legged walk. The feet may seem to stick to the floor (called a magnetic gait). People also have urinary incontinence and a tendency to fall.
Dementia may not develop until late in the disorder. Often, the first signs of dementia are difficulty planning, organizing, putting ideas or doing actions for a task in the right order (sequencing), thinking abstractly, and paying attention. Memory tends to be lost later.
The diagnosis cannot be based on symptoms alone, particularly in older people. Other dementias can cause similar symptoms. Brain imaging, usually magnetic resonance imaging (MRI) may detect excess cerebrospinal fluid, but this finding is also inconclusive, although it supports the diagnosis of normal-pressure hydrocephalus.
To help with the diagnosis, doctors do spinal taps (lumbar puncture) or place a temporary drain into the spinal cord to remove excess cerebrospinal fluid. If these procedures relieve symptoms, normal-pressure hydrocephalus is likely, and treatment is likely to be effective.
Treatment consists of placing a piece of plastic tubing (a shunt) in the ventricles of the brain and running it under the skin, usually to the abdomen (ventriculoperitoneal shunting). Cerebrospinal fluid is then drained away from the brain. The effects of this treatment may not be evident for several hours. This procedure may significantly improve the ability to walk and function and may lessen incontinence. However, mental function improves less and in fewer people. Thus, early diagnosis is important, so that people can be treated before dementia develops.
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