NPH is a type of hydrocephalus that usually occurs in people aged 65 and older. It is different than other types of hydrocephalus because it develops slowly over time. The cerebral spinal fluid (CSF) is blocked gradually, and the excess fluid builds up slowly. This means the fluid pressure in the brain may not be as high as in other types of hydrocephalus. The ventricles still become enlarged and press on the brain causing the triad of symptoms loss of bladder control, altered walking gait and a decline in cognitive processes such as memory and problem solving.