Normal pressure hydrocephalus is a form of hydrocephalus that is relatively mild but is very hard to diagnose. It is often mistaken for other conditions that cause gradual dementia or loss of the ability to walk, such as Parkinson's disease. However, it is treatable and most treated patients regain full use of their legs and mental faculties.

The underlying cause is the same as most forms of hydrocephalus, a blockage at the base of the brain where cerebro-spinal fluid drains into the spinal column. However, in most cases of hydrocephalus, the symptoms are obvious and severe, usually headache, nausea and vomiting. In addition, the opening pressure with a lumbar puncture is noticeably high, where in normal pressure hydrocephalus, the value will usually be well within the normal range and only occasionally will fall in the high range. Doctors will often rule out hydrocephalus as a cause of the symptoms and focus on other conditions that cause dementia.

Because normal pressure hydrocephalus tends to happen more often in older patients, a differential has to be far more complete to rule it out as a possible diagnosis. A combination of a series of lumbar punctures, a CT scan, MRI and other tests should be performed to see if there is any blockage.

Once diagnosed, a shunt can be surgically inserted. Patients usually improve rapidly after treatment with mental faculties returning almost immediately and walking returning after physiotherapy.

Normal pressure hydrocephalus is one of Chi Park's favorite differential diagnoses.

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