Can the radiological scale “iNPH Radscale” predict tap test response in idiopathic normal pressure hydrocephalus?

Tiberiu Laticevschi,Alma Lingenberg,Stéphane Armand,Alessandra Griffa,Frédéric Assal,Gilles Allali

doi:10.1016/j.jns.2020.117239

Abstract

BackgroundIdiopathic normal pressure hydrocephalus (iNPH) presents typical radiological signs that have been summarised in a semi-quantitative scale named the iNPH Radscale. However, the iNPH Radscale's predictive value for response to cerebrospinal fluid (CSF) tap test has never been studied. This study aims to investigate if the iNPH Radscale can predict locomotion improvement after CSF tap test. MethodsA total of 100 patients with iNPH (age: 76.3 ± 7.9, gender: 36% female) were included in this retrospective study. Two raters, blinded to the response of the CSF tap test, evaluated the iNPH Radscale and its seven subitems (Evan's index, callosal angle, size of temporal horns, narrow high-convexity sulci, dilated Sylvian fissures, focally dilated sulci, and periventricular hypodensities). Locomotion improvement was assessed by the Timed Up and Go (TUG) performed before, and 24 h after, the CSF tap test. ResultsThe iNPH Radscale (total score) was similar between the CSF tap test responders and non-responders (responders: 8.31 ± 1.96, non-responders: 9.18 ± 2.51, p = 0.128). However, the temporal horns score was smaller in the responders group (1.66 ± 0.57 versus 1.94 ± 0.24, p = 0.045), even after adjusting for age, gender, education level, white matter changes, and global cognition (β: -0.250, C.I. 95%: [−3.185; −0.161], p = 0.031). ConclusionThe iNPH Radscale (total score) does not predict locomotion improvement after CSF tap test, while a smaller temporal horns score at baseline is associated with a positive tap test responder status.

Highlights

Idiopathic normal pressure hydrocephalus is characterised by locomotion disturbance, cognitive impairment, and urinary inconti nence, with enlarged ventricles at brain imaging [1,2]
This study aims to investigate if the Idiopathic normal pressure hydrocephalus (iNPH) Radscale can predict locomotion improvement after cerebrospinal fluid (CSF) tap test
The iNPH Radscale does not predict locomotion improvement after CSF tap test, while a smaller temporal horns score at baseline is associated with a positive tap test responder status

Summary

Introduction

Idiopathic normal pressure hydrocephalus (iNPH) is characterised by locomotion disturbance, cognitive impairment, and urinary inconti nence, with enlarged ventricles at brain imaging [1,2]. INPH is often associated with comorbid neurological conditions, such as Alzheimer’s disease or other neurodegenerative conditions, which interfere with the reversibility of symptoms [4] Various neuroimaging biomarkers, such as the hippocampal volume or microstructural changes in specific white matter tracts [5,6], have been studied to identify iNPH patients with good prognosis after shunt surgery. These neuroimaging fea tures rely on complex image processing approaches, which are difficult to apply in clinical practice. Conclusion: The iNPH Radscale (total score) does not predict locomotion improvement after CSF tap test, while a smaller temporal horns score at baseline is associated with a positive tap test responder status

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