Cognitive Changes After Tap Test in Patients With Normal Pressure Hydrocephalus

Abstract

Abstract Background: Normal pressure hydrocephalus (NPH) leads to cognitive impairment (CI) as part of its triad of symptoms. Its assessments before and after a tap test in suspected patients can be used to inform diagnosis, differentiate NPH symptoms from alternative or concomitant causes of CI, and suggests the potential benefits of valve-placement. The aim of this study was to describe the assessment of domain-specific cognitive performance in patients with NPH diagnosis before and after a tap test, applied as part of the diagnostic workup upon initial NPH suspicion. Methods: Before-and-after study that included NPH patients that underwent cognitive assessments by neuropsychologists before and after a tap test. Clinical features at baseline and results in the CERAD, ADAS-COG, SVF, PVF, ROCF and IFS tests were recorded. The tests scores were converted to z-scores according to age and level of education. Absolute scores, z-scores are described for each domain and according to the presence of dementia. Changes after tap test were assessed with paired-samples hypothesis testing. This study was approved by the institutional ethics review board before start. Results: 76 NPH patients were included, their median age was 81 years (77-83) and 65 NPH patients (87.8%) were considered to have improved cognitive performance after tap test as part initial usual-care diagnostic assessment. We detected small differences in scores of ROCF (p=0.018) and IFS (p<0.001) between pre- and post-tap test assessments. No difference in the proportion of patients with altered cognitive performance was detected in this short 24-hour interval. Dementia was concomitant in 68.4% of patients, was negatively associated with improvement in SVF (2.9% vs. 28.6%, p=0.003) and IFS (0% vs. 16%, p=0.014) and may have affected detection of improvement for other tests. Conclusion : Executive function and praxis are the cognitive domains more susceptible to improvement after a tap test in a 24-hour interval in NPH patients upon initial assessment. These results are of interest to multidisciplinary groups involved in the diagnosis of NPH and could help inform patient selection for valve placement in NPH.