Normal pressure hydrocephalus (NPH): more about NPH by a physician who is the patient.

The incidence of idiopathic normal pressure hydrocephalus (INPH) is seen to be relatively rare, ie about two per million inhabitants per year. Five studies on the prevalence of INPH in elderly patients, from three countries, have been published between 1985 and 2009.1-5 Prevalence ranged from 0.41% to 2.94% (mean 0.8%), ie slightly less than one per 100 based on samples ranging from 170 to 982 subjects. This surprisingly high percentage was not found in a survey that attempted to identify every person with INPH in a small county in Norway with a population of 219,748. Attempts to identify all patients with INPH overlook many cases. INPH is actually a very common disease and its prevalence increases with age.