Five-year incidence of surgery for idiopathic normal pressure hydrocephalus in Norway

Objectives - We have previously determined the incidence and prevalence of idiopathic normal pressure hydrocephalus (iNPH) in the county of Vestfold in Norway. This study aimed at determining the incidence of surgeries for iNPH. Materials and methods - Information about age, sex, operation year and operation type was collected retrospectively for all patients hospitalized from 2002 to 2006 with any diagnosis of iNPH and operated with insertion of a ventriculo-peritoneal or ventriculoatrial shunt system, or with endoscopic third ventriculostomy in any of Norway's five regional neurosurgical centers. Results - Two hundred fifty-two patients were operated during the 5-year period, making the total incidence 1.09/100,000/year. The yearly incidence ranged from a minimum of 0.84/100,000 in 2006 to a maximum of 1.47/100,000 in 2004. The incidence was highest in the age group 70-79 years. There were little regional differences regarding incidence, sex, and age and operation type. Conclusions - The data suggest that too few patients are being offered surgical treatment for iNPH in Norway.