Fig. 2

How the compared groups in the final analysis were formed based on the questionnaires and the phone interviews. The dashed lines and the boxes with dashed borders indicate exclusion from the final analysis. The left side of the figure shows how the group of “Probable fNPH patients” (n = 60) was formed from the probable fNPH index patients and their relatives with iNPH and a shunt. Everyone in this group had a diagnosed and shunted iNPH. The middle and the right part of the figure show how the control group of “Non-iNPH relatives, age ≥ 60” (n = 49) was formed from the ≥ 60-year-old relatives of the probable fNPH patients. These relatives were either asymptomatic or had a known etiology for their symptoms other than iNPH. *The iNPH patients with symptomatic relative(s) without brain-imaging and their healthy relatives were excluded from the final analysis