What is normal pressure hydrocephalus?

Normal pressure hydrocephalus, or NPH, is a brain disorder in which excess cerebrospinal fluid builds up in the brain's ventricles, causing trouble walking, problems with thinking and loss of bladder control. The Alzheimer's Association explains it is called normal pressure because fluid pressure measured during a spinal tap is often normal. It mainly affects people in their 60s and 70s, and in most cases the cause is unknown.

The three main symptoms are changes in walking, slowed thinking, and trouble controlling urine. MedlinePlus describes difficulty starting to walk and feeling as if the feet are stuck to the ground, along with forgetfulness, difficulty paying attention and apathy. Symptoms often begin slowly. Not everyone has all three, and bladder problems tend to appear later than the walking and thinking changes.

NPH is a brain disorder that can cause dementia, and it is one of the few causes of dementia that can be controlled or reversed with treatment. The Alzheimer's Association notes its symptoms resemble Alzheimer's, Parkinson's and Creutzfeldt-Jakob disease, so it is often overlooked or misdiagnosed, and says fewer than 20 percent of people with NPH are properly diagnosed.

Sometimes. A shunt, a thin tube that drains extra fluid from the brain to the abdomen, can improve symptoms in some people, and walking is the most likely to get better. The Alzheimer's Association notes that thinking and bladder problems are less likely to improve, that benefits may fade over time, and that surgery has risks. A high volume spinal tap can help show who might benefit.

NPH is caused by fluid building up in the brain's ventricles and can sometimes be treated with a shunt, while Alzheimer's involves progressive damage to brain cells. The Alzheimer's Association explains that brain scans help tell them apart: in Alzheimer's, shrinking brain tissue can make the ventricles look larger, but in NPH the ventricles are enlarged without that shrinkage. Walking problems are a hallmark of NPH.