Nationwide hospital‐based survey of idiopathic normal pressure hydrocephalus in Japan: Epidemiological and clinical characteristics

Objectives There have been no nationwide epidemiological studies of idiopathic normal pressure hydrocephalus (iNPH) in Japan. Therefore, a nationwide epidemiologic survey of iNPH was performed to determine the number of cases and clinical characteristics by sex and diagnostic level. Methods The first survey examined the numbers of cases that met the diagnostic criteria of iNPH and those who underwent shunt operations in 2012. The second survey gathered patients' details to clarify their clinical background characteristics. Results The estimated number of cases meeting the diagnostic criteria in 2012 was 12,900, with 6,700 undergoing shunt operations. The estimated crude prevalence was 10.2/100,000 persons. The age of onset was in the 70s in more than 50% of both men and women. Significantly higher (p