Quantitative gait analysis value as a predictor of shunt surgery effectiveness in normal pressure hydrocephalus: A technical note

Abstract

Introduction: Shunt surgery (SS) remains the most effective treatment for idiopathic Normal pressure hydrocephalus (iNPH), but the selection of the patients with the greatest potential benefit remains elusive.

Objective: Identify gait features predictive of best response to SS in iNPH.

Methods: Eight patients with iNPH were assessed at baseline, after Cerebrospinal fluid tap-test (CSF-TT) and SS, with clinical scales (Clinical/Patient Global Clinical Impression, EuroQol-5D, Clinical Dementia Rating Scale(CDR), MoCA test, Hoehn-Yahr Scale) and gait analysis with inertial sensors.

Results: The 8 included iNPH patients had a mean age of 73 years(59-81), moderate cognitive (CDR-1.5 (0.5-2); MoCA-9.5 (3-21)) and motor impairment (Hoehn-Yahr-2.75(2-3)). After SS, patients had a significant improvement in cognition (MoCA, p = 0.001) and quality of life. At baseline, patients with lower improvement (no change/ minimally improved) (n = 2), in comparison to patient with higher improvement (much/very much improved) (n = 6), already had higher cognitive impairment (MoCa-3(3-3) vs. 11(7-21)). Patients with lower improvement had a lower % of change in gait performance at LP (mean 10.2 %) and were absent of additional benefit after SS(mean -0.8 %). In contrast, gait performance in patients with higher improvement consistently got better from baseline to LP (mean 23.1 %) and from baseline to SS (mean 82.9 %). A significant negative correlation was observed between CDR score and several gait variables: speed (r_pb=-0.92,p = 0.009); stride length (r_pb=-0.92,p = 0.009); lift-off angle (r_pb=-0.96,p = 0.003); and maximum heel (r_pb=-0.81,p = 0.049).

Conclusion: The magnitude of gait improvement after CSF-TT, quantified by gait analysis, can be used as an integral variable in the multimodal clinical approach to the prediction of improvement after SS.

Keywords: CSF tap test; Gait analysis; Normal pressure hydrocephalus; Shunt surgery.