Learning ballet technique modulates the stretch reflex in students with cerebral palsy: case series

(2024) 25:66 López‑Ortiz et al. BMC Neuroscience https://doi.org/10.1186/s12868-024-00873-0 BMC Neuroscience Open Access RESEARCH Learning ballet technique modulates the stretch reflex in students with cerebral palsy: case series Citlali López‑Ortiz1,2*, Maxine He1, Deborah Gaebler‑Spira3,4 and Mindy F. Levin5,6 Abstract Background Cerebral palsy (CP) is considered the most prevalent developmental motor disorder in children. There is a need for training programs that enhance motor abilities and normalize function from an early age. Previous stud‑ ies report improved motor outcomes in dance interventions for CP. Investigating the neurophysiological mechanisms underlying such improvements is necessary for efficient and safe intervention design. This study reports changes in stretch reflex responses as the primary neurophysiological motor outcome of a targeted ballet class intervention. Results A case series of participants with mixed spastic and dyskinetic CP (n = 4, mean age = 12.5 years, SD = 6.9S years, three female, one male) who learned ballet technique in a course of one-hour classes twice per week for six weeks is presented. Changes in stretch reflex responses and in clinical motor tests as secondary outcomes were observed after the course and at one-month follow-up. Quantitative measures of elbow or ankle stretch reflex were obtained using electromyography and electrogoniometry. The joint angle of the stretch reflex onset varied across velocities of stretch, and its variability decreased after the intervention. Within-subject tests of the central tendency of stretch reflex angle coefficients of variation and frequency distribution demonstrated significant changes (p-values < 0.05). Secondary outcomes included the Quality of Upper Extremity Skills Test (QUEST), Pediatric Bal‑ ance Scale (PBS), Modified Tardieu Scale (MTS), Dyskinesia Impairment Scale (DIS), and Selective Control Assessment of the Lower Extremity (SCALE). All the participants demonstrated improvements larger than the minimal clinical important difference (MCID) or the smallest detectable difference (SDD), as applicable. Conclusions Evidence of changes in the stretch reflex responses in these four cases of mixed CP was observed. The observed variability in the stretch reflex responses may be due to the dyskinetic component of the mixed CP pres‑ entations. More studies with a larger sample size and longer duration of learning and practice of ballet technique are necessary to establish the extent of possible modulation and adaptation of the stretch reflex response as a neuro‑ physiological basis for observed improvements in clinical measures. Trial registration: This study was registered in the Clinical Trials Protocol Registration and Results System (NCT04237506, January 17, 2020). Keywords Cerebral palsy, Ballet, Stretch reflex, Motor learning, Rehabilitation, Dance Affiliations when the experiment was conducted. *Correspondence: Citlali López‑Ortiz Full list of author information is available at the end of the article © The Author(s) 2024. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativeco mmons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. López‑Ortiz et al. BMC Neuroscience (2024) 25:66 Introduction Cerebral palsy (CP) is considered the most prevalent developmental motor disorder in children [1]. CP is considered a non-progressive condition consisting of a group of permanent dysfunctions in movement and posture resulting from injuries in the developing brain during the prenatal and perinatal periods [2]. According to the Surveillance of Cerebral Palsy working group in Europe, muscle tone in CP is divided into hypertonic and hypotonic types, further classified into three main groups based on motor signs: (1) spastic, (2) dyskinetic (divided further into dystonia and choreoathetosis), and (3) ataxic [3]. Hypertonic and hypotonic manifestations can be present in the same child as in the mixed presentation of spasticity and dyskinesia [4]. The motor impairments result in decreased motor performance and participation in social and daily living activities that evolve into increased disability with age [5]. Hence, there is a need to develop training programs that yield positive motor outcomes and normalize activities and participation throughout the lifespan [6]. Various dance forms, including creative dance, dancebased in somatic therapies, ballroom dance, hip-hop, and classical ballet, have shown positive movement outcomes for persons with CP while increasing social participation. Previous studies have reported improved balance, gait, selective motor control, range of motion, rhythm production, and executive function [5–9]. However, the neurophysiological mechanisms that underlie such improvements have not been elucidated. Gaining a better understanding of the underlying neurophysiological mechanisms is key for the objective, beneficial, and efficient design of dance classes and programs for persons with CP while avoiding possible motor rehabilitation pitfalls. Several studies on stretch reflex adaptation in classical ballet dancers and modern dancers have shown that ballet and modern dance training produce a long-term depression of the H-reflex [10–15]. The H-reflex has the same neuronal pathway as the stretch reflex, but it is electrically induced as opposed to a mechanically induced muscle stretch. It is estimated that 80% of individuals with CP present heightened stretch reflexes that underlie clinical spasticity [4]. Thus, adaptation through learning and practicing ballet techniques in CP may constitute an important neurophysiological mechanism for the improved motor outcomes reported in the previous research [5, 14, 16–21]. This study quantifies the changes in the stretch reflex after learning classical ballet technique in a course similar to that of previously published studies as one plausible neurophysiological mechanism for the previously reported improved motor outcomes [19–21]. Page 2 of 12 In the case of individuals with mixed spasti (...truncated)