Normal pressure hydrocephalus (NPH) is a type of hydrocephalus that occurs in adults, usually older adults. The average age of people with NPH is older than 60 years.
NPH is different to 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.
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.
Note: The symptoms of NPH can be similar to those of diseases such as Alzheimer's and Parkinson's. Experts believe that many cases of NPH are misdiagnosed as one of these diseases.
What causes NPH?
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 tumour. It can also happen after surgery on the brain. How these conditions lead to NPH is not clear. In most cases, the cause of NPH is never fully known.