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Normal Pressure Hydrocephalus

What Is Normal Pressure Hydrocephalus?

The brain and spinal cord are surrounded by a clear fluid called cerebrospinal fluid (CSF). This fluid is produced and stored in cavities in the brain called ventricles. It circulates around the brain, moving from ventricle to ventricle. The purposes of the fluid are to cushion and protect the brain and spinal cord, to supply them with nutrients, and to remove some of their waste products. Any excess fluid drains away from the brain and is absorbed by veins at the top of the brain.

Hydrocephalus is a condition in which there is too much CSF in the ventricles. This occurs when the natural system for draining and absorbing extra CSF does not work right. The ventricles enlarge to accommodate the extra fluid and then press on different parts of the brain, causing a number of different symptoms. Hydrocephalus has many different causes. Some people are born with the condition, while others develop it during their lives.

Normal pressure hydrocephalus (NPH) is a type of hydrocephalus that usually occurs in older adults. The average age of person with NPH is older than 60 years. NPH is different than other types of hydrocephalus in that it develops slowly over time. The drainage of CSF is blocked gradually, and the excess fluid builds up slowly. The slow enlargement of the ventricles means that the fluid pressure in the brain may not be as high as in other types of hydrocephalus. However, the enlarged ventricles still press on the brain and can cause symptoms (the term "normal pressure" is somewhat misleading).

The parts of the brain most often affected in NPH are those that control the legs, the bladder, and the "cognitive" mental processes such as memory, reasoning, problem solving, and speaking. This decline in mental processes, if it is severe enough to interfere with everyday activities, is known as dementia. Other symptoms include abnormal gait (difficulty walking), inability to hold urine (urinary incontinence), and, occasionally, inability to control the bowels.

The dementia symptoms of NPH can be similar to those of Alzheimer's disease. The walking problems are similar to those of Parkinson's disease. Experts say that many cases of NPH are misdiagnosed as one of these diseases. The good news is that, unlike Alzheimer's and Parkinson's, NPH can be reversed in many people with appropriate treatment. But first it must be correctly diagnosed.

What Causes Normal Pressure Hydrocephalus?

Normal pressure hydrocephalus can occur after a head injury, bleeding around the brain (due to a blow to the head), stroke, meningitis (infection of a protective layer of tissue around the brain), or brain tumor. It can happen after surgery on the brain. How these conditions lead to NPH is not clear. In most cases, the cause of NPH is never known.

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