Cognitive changes after tap test in patients with normal pressure hydrocephalus: a before-and-after study

Abstract Normal pressure hydrocephalus (NPH) leads to cognitive impairment (CI) as part of its triad of symptoms. Assessment of CI before and after a tap test can be used to inform diagnosis, differentiate NPH symptoms from alternative or concomitant causes of CI, and suggest the potential benefits of valve placement. The aims of this study are: to describe cognitive performance in patients with NPH diagnosis before and after a tap test, and to compare CI between patients with NPH meeting criteria for a dementia diagnosis (D +) and those without criteria for dementia (D−) at both baseline and after the tap-test. We performed a Before-and-after study evaluating clinical features and performance on cognitive tests (CERAD, ADAS-COG, SVF, PVF, ROCF and IFS). We included 76 NPH patients, with a median age of 81 years. 65 patients (87.8%) improved cognitive performance after tap test. ROCF (p = 0.018) and IFS (p < 0.001) scores significantly change after the tap test. Dementia was concomitant in 68.4% of patients. D + group showed higher proportion of patients with altered performance in IFS, PVF, SVF, and ROCF than D- group at baseline (p < 0.05). A significant improvement in SVF and IFS was observed exclusively in the D− group after tap test. Our results suggest that executive function and praxis are the cognitive domains more susceptible to improvement after a tap test in a 24-h interval in NPH patients. Moreover, the D− group showed a higher proportion of improvement after the tap test in executive function and verbal fluency test compared with the D + group