A comprehensive clinico-radiological, neuropsychological and biomechanical analysis approach to patients with idiopathic normal pressure hydrocephalus

•It is essential to recognize iNPH patients who may benefit from shunt surgery.•Cut-off values after CSF tap test will be proposed.•A systematic approach is essential to support a positive shunt surgery outcome. A systematic approach to patients with suspected idiopathic normal pressure hydrocephalus (iNPH) is essential to recognize the subset of patients who may benefit from ventriculoperitoneal shunt surgery (VPS). Quantitative biomechanical analysis of gait and balance (QBAGB) may help objectify the response to the cerebrospinal fluid tap test (CSF-TT) and VPS outcome after 3 months and support identification of candidates for VPS. We retrospectively reviewed data from all patients with probable iNPH who 1) underwent clinico-radiological and neuropsychological assessments using validated scales (iNPH Scale and iNPH Radscale) at our centre in the period from January to December 2018; and 2) had completed QBAGB before CSF-TT (‘baseline’), shortly after CSF-TT, and at three months after either VPS or conservative treatment. At the time-points ‘after CSF-TT’ and ‘3 months’, patients with iNPH and VPS (n = 11) significantly improved on the Kiefer Scale score, iNPH Scale total score and gait domain score, as well as in gait velocity and step length measured by QBAGB. In contrast, patients without surgery (n = 10) had unchanged iNPH Scale scores and motor performance throughout. Using data from all patients, we calculated cut-off levels for substantial improvements in gait velocity, step length, and the iNPH Scale domain gait score at the time-point ‘after CSF-TT’. QBAGB helps to objectify the response to CSF-TT to select candidates for VPS and corroborates clinico-radiological and neuropsychological data derived from validated scales. The QBAGB cut-off values for substantial improvement after CSF-TT need further elucidation in larger, preferably prospective studies.