title: Epidemiology of Idiopathic Normal Pressure Hydrocephalus: A Systematic Review of the Literature.
abstract: BACKGROUND
  Idiopathic normal pressure hydrocephalus (iNPH) is an important cause of gait disturbance and cognitive impairment in elderly adults. However, the epidemiology of iNPH is relatively unknown, largely as a result of the paucity of specifically designed population studies. This systematic review aims to assess the prevalence and incidence of iNPH.
  
  
  METHODS
  A systematic literature review on the epidemiology of iNPH was conducted using MEDLINE/PubMed searching for articles published up to June 2014.
  
  
  RESULTS
  The inclusion criteria were met by 21 studies. Of the studies, 12 were specifically designed for detecting cases of iNPH; however, only 4 were prospective. In people >65 years old, pooled prevalence obtained from specific population studies was 1.3%, which was almost 50-fold higher than that inferred from door-to-door surveys of dementia or parkinsonism. Prevalence may be higher in assisted-living and extended-care residents, with 11.6% of patients fulfilling the criteria for suspected iNPH and 2.0% of patients showing permanent improvement after cerebrospinal fluid diversion. The only prospective population-based survey that reported iNPH incidence estimated 1.20 cases/1000 inhabitants/year, 15-fold higher than estimates obtained from studies based on hospital catchment areas. The incidence of shunt surgery for iNPH and shunt-responsive iNPH obtained from incident cases of hospital catchment areas appears to be <2 cases/100,000 inhabitants/year and 1 case/100,000 inhabitants/year, respectively. No population-based study reporting the real values for these 2 parameters could be found.
  
  
  CONCLUSIONS
  iNPH appears to be extremely underdiagnosed. Properly designed and adequately powered population-based studies are required to characterize the epidemiology of this disease accurately.
authors.affiliation: Department of Neurosurgery-Spine Unit, University Hospital "Marqués de Valdecilla", Santander, Spain. Electronic address: rmlaez@yahoo.es.
authors.forename: Rubén
authors.initials: R
authors.lastname: Martín-Láez
authors.affiliation: Department of Neurosurgery-Spine Unit, University Hospital "Marqués de Valdecilla", Santander, Spain.
authors.forename: Hugo
authors.initials: H
authors.lastname: Caballero-Arzapalo
authors.affiliation: Department of Neurosurgery-Spine Unit, University Hospital "Marqués de Valdecilla", Santander, Spain.
authors.forename: Luis Ángel
authors.initials: LÁ
authors.lastname: López-Menéndez
authors.affiliation: Ikerbasque, Basque Foundation for Science, University of Deusto, Bilbao, Spain.
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Arango-Lasprilla
authors.affiliation: Department of Neurosurgery-Spine Unit, University Hospital "Marqués de Valdecilla", Santander, Spain.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Vázquez-Barquero
mesh_terms: D006306:Health Surveys; D006801:Humans; D006850:Hydrocephalus, Normal Pressure / Q000453:epidemiology*; D015995:Prevalence
keywords: Epidemiology; Idiopathic normal pressure hydrocephalus; Incidence; Prevalence; Review; Shunt-responsive hydrocephalus; Ventriculomegaly