Reduced reciprocal inhibition during clinical tests of spasticity is associated with impaired reactive standing balance control in children with cerebral palsy

• Type of Material: Article
• Authors: Jente Willaert, KU Leuven; Lena Ting, Emory University; Anja Van Campenhout, KU Leuven; Kaat Desloovere, KU Leuven; Friedl De Groote, KU Leuven
• Language: English
• Date: 2023-11-08
• Publisher: NIH
• Publication Version: Preprint (Prior to Peer Review)
• Copyright Statement: The copyright holder for this preprint is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.
• License: Creative Commons Attribution 4.0 International
• Final Published Version (URL): https://doi.org/10.1101/2023.11.07.23298160
• Title of Journal or Parent Work: medRxiv
• Grant/Funding Information: This study was funded by the Flemish Agency for Scientific Research (FWO-Vlaanderen) through a research fellowship to JW (1192320N) and by the National Institute of Health (NIH) research grant NIH R01 HD46922 to LHT
• Keywords: perturbing functional movements; reactive balance impairments; cerebral palsy; muscle response; standing balance; relaxed patient; joint hyper-resistance
• Research Categories: Health Sciences, Human Development; Biology, Anatomy

Abstract

Background: Joint hyper-resistance is a common symptom in cerebral palsy (CP). It is assessed by rotating the joint of a relaxed patient. Joint rotations also occur when perturbing functional movements. Therefore, joint hyper-resistance might contribute to reactive balance impairments in CP. Aim: To investigate relationships between altered muscle responses to isolated joint rotations and perturbations of standing balance in children with CP. Methods & procedures: 20 children with CP participated in the study. During an instrumented spasticity assessment, the ankle was rotated as fast as possible from maximal plantarflexion towards maximal dorsiflexion. Standing balance was perturbed by backward support-surface translations and toe-up support-surface rotations. Gastrocnemius, soleus, and tibialis anterior electromyography was measured. We quantified reduced reciprocal inhibition by plantarflexor-dorsiflexor co-activation and the neural response to stretch by average muscle activity. We evaluated the relation between muscle responses to ankle rotation and balance perturbations using linear mixed models. Outcomes & results: Co-activation during isolated joint rotations and perturbations of standing balance was correlated across all levels. The neural response to stretch during isolated joint rotations and balance perturbations was not correlated. Conclusions & implications: Reduced reciprocal inhibition during isolated joint rotations might be a predictor of altered reactive balance control strategies.