The reoperation rate of 26% for any cause in our data was rather high. Fourteen percent of the patients had revisions due to mechanical problems. In the systematic review by Toma et al., the revision rate, constituting the need for revision due to shunt failure or “mechanical causes”, was 13% in 30 articles published after 2006 . One explanation for a higher reoperation rate in the current material is the longer follow-up period. Most studies have follow-up periods of up to 1 year, while 42% of the revisions in the present study were performed later. Another explanation could be that patients included in other studies aiming to investigate, e.g., specified measurements may have been carefully selected, whereas the present study includes all operated iNPH patients from the participating centers.