Literature ReviewEpidemiology of Idiopathic Normal Pressure Hydrocephalus: A Systematic Review of the Literature

BackgroundIdiopathic 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.MethodsA systematic literature review on the epidemiology of iNPH was conducted using MEDLINE/PubMed searching for articles published up to June 2014.ResultsThe 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.ConclusionsiNPH appears to be extremely underdiagnosed. Properly designed and adequately powered population-based studies are required to characterize the epidemiology of this disease accurately.