Callosal Angle Sub-Score of the Radscale in Patients with Idiopathic Normal Pressure Hydrocephalus Is Associated with Positive Tap Test Response

Abstract

The aim of the present study was the implementation of the composite imaging “Radscale” in patients with idiopathic normal pressure hydrocephalus (iNPH) and the evaluation of its score, as well as absolute stroke volume and peak flow velocity of cerebrospinal fluid (CSF) in aqueduct as indicators of a positive response following a tap test. Forty-five patients with iNPH were included. Clinical evaluation involved the 10 m timed walk test before and every 24 h for 3 consecutive days after evacuative lumbar puncture (LP). Neuropsychological evaluation comprised a mini mental state examination (MMSE), frontal assessment battery (FAB), 5-word test (5WT) and CLOX drawing test 1 and 2, which were carried out before and 48 h after LP. The tap test’s response was defined as a ≥20% improvement in gait and/or a ≥10% improvement in neuropsychological tests. All scores of neuropsychological and clinical variables, except for immediate 5WT and CLOX-1, differed significantly before and 48 h after LP. Improvement in time and steps of a 10 m timed walk test differed significantly between female and male patients. Out of 45 total patients, 19 were tap test responders and 26 non-responders. The total score of Radscale and CSF flow parameters did not differ between responders and non-responders. However, “Callosal angle” sub-score differed significantly between these two groups. A greater “callosal angle” sub-score, meaning more acute callosal angle, was associated with a positive tap test response, rendering it a useful measurement in the stratification of iNPH patients that will potentially respond to CSF shunting.

Imaging Markers for Normal Pressure Hydrocephalus: An Overview

“…Laticevschi et al, (2021) found that Radscale total score was similar between tap test responders and non-responders [104]. This finding was confirmed by another recent study that implemented Radscale on iNPH patients' brain MRIs [80].…”

“…Regarding the association of imaging markers with the severity of symptoms, tap test, and shunt responsiveness, the following conclusions can be drawn. EI and CA have been, according to many studies, correlated to both tap test and shunt responsiveness [16,[79][80][81]85]. Nevertheless, CA failed to predict shunt responsiveness according to Skalický et al, (2021) [83].…”

“…Results of correlation of composite imaging scales such as Radscale [80,[101][102][103][104] or DESH score [49,83,86,101] to either tap test or shunt responsiveness are rather inconclusive. Aqueductal CSF flow measurements using phase-contrast MRI, along with flow void sign may be helpful in predicting outcome after shunt [29,98,99], although ASV alone does not seem to predict shunt responsiveness [47].…”

“…It has been found that both EI higher than 0.3 and more acute CA (<90 • ) might correlate with better surgical outcome of iNPH patients [16,21], while more acute CA as a single marker has also been associated to tap test and shunt responsiveness [16,79,80]. Another study investigated the difference in EI and CA before and after surgical treatment with lumbo-peritoneal (LP) shunt placement.…”

Cerebrospinal Fluid Biomarkers in iNPH: A Narrative Review

“…Radiologically, it is characterized by enlarged lateral and third ventricles, disproportionally to cortical sulci enlargement, as depicted by brain imaging, either with computed tomography (CT) or magnetic resonance imaging (MRI) [ 8 ]. Increased Evans index, temporal horns dilation, periventricular white matter lesions, narrow callosal angle and sulci in the convexity, focally enlarged sulci and dilated Sylvian fissures are additional imaging findings that have been described [ 9 , 10 , 11 , 12 , 13 , 14 ].…”