Evaluation of the Effectiveness of the Tap Test by Combining the Use of Functional Gait Assessment and Global Rating of Change

Abstract

BackgroundAlthough the tap test for patients with suspected idiopathic normal pressure hydrocephalus (iNPH) is still often performed as part of the preoperative evaluation, it is true that some studies have reported the limitations of the tap test, claiming that it does not provide the additional information for appropriate patient selection for surgery. We aimed to determine whether a better method of pre- and post-tap test assessment could lead to appropriate patient selection for shunting.MethodsWe performed the tap test as part of the preoperative evaluation in all 40 patients who underwent lumboperitoneal shunt surgery for iNPH from April 2021 to September 2021. We retrospectively analyzed the patient data. We examined whether a comprehensive evaluation of the effect of the tap test using the Functional Gait Assessment (FGA) and Global Rating of Change (GRC) scales would identify a wider range of patients who would benefit from shunt surgery than the 3-m Timed Up and Go test (TUG) alone.ResultsAssuming a prevalence of 1% for iNPH, the TUG had a sensitivity of 0.23, specificity of 0.71, positive likelihood ratio of 0.79, and negative likelihood ratio of 1.09. When improvement in either the FGA or the GRC was used as a criterion for the validity of the tap test, the sensitivity was 0.88, specificity was 0.17, positive likelihood ratio was 1.06, and negative likelihood ratio was 0.71.ConclusionImprovement in either the FGA or the GRC is a more sensitive criterion for the effectiveness of the tap test for the gait aspect than the TUG. Since the negative likelihood ratio is lower than that for the TUG alone, it is more appropriate to exclude patients with neither FGA nor GRC improvement from surgical indications than to exclude surgical indications based on a negative TUG.

Relationship between disproportionately enlarged subarachnoid-space hydrocephalus and white matter tract integrity in normal pressure hydrocephalus

“…The CSF tap test was performed in 10 and 16 patients in the low- and high-DESH groups, respectively. Based on the criterion of at least 10% improvement in gait velocity in the timed up and go evaluation 15 , 70% (low-DESH group) and 62.5% (high-DESH group) patients showed improvement, respectively. Improvements of 3 or more points in cognitive function assessed by Mini-Mental State Examination (MMSE) before and after the CSF tap test were observed in approximately 20 and 18.8%, respectively 16 .…”

“…We collected whether a CSF tap test was performed and whether symptoms improved afterward. A responder was defined as a patient who showed an improvement of 10% or more in walking speed 6 h and 24 h after the CSF tap test, based on the results of the timed up and go evaluation performed at the time of the tap test 15 . For cognitive function, we checked the change in MMSE score before and after the CSF tap test to determine if the score improved by 3 points or more 16 .…”