The effects of chiropractic spinal manipulation on muscle strength and the H-reflex in children with spastic diplegic cerebral palsy: A feasibility study
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Background: Cerebral Palsy (CP) is a term used to describe a group of motor disorders resulting from an injury to the developing brain either during pregnancy, birth or in infants up to 2 years. Children with CP have deficits in various aspects of motor control, including motor neuron excitability, that can affect their muscle strength, gait and ability to perform activities of daily living. The Hoffman (H) reflex is an electrical variant of the spinal stretch reflex and used in neurophysiology to assess motor neuron excitability. Previous research on chiropractic spinal manipulation in healthy adults, athletes and a brain-injured population indicate improvements in motor neuron excitability, muscle strength and various aspects of motor control. Objectives: To assess feasibility aspects of conducting a large scale randomized, controlled study measuring the effects of chiropractic spinal manipulation on motor neuron excitability and muscle strength in children with CP. Methods: Children with spastic diplegic CP, aged 8-13 years, were recruited through the New Zealand Cerebral Palsy Registry for a randomized, controlled feasibility study. Feasibility was assessed in the areas of recruitment strategy and rate, data collection procedures, equipment, intervention and compliance. Three children completed data collection comprised of pre and post measurements of the H reflex, V-wave and muscle strength. Participants were randomized into a chiropractic spinal manipulation intervention group or a passive control intervention group. Results: The recruitment strategy and rate proved to not be feasible in recruiting enough participants to appropriately power a larger scale study of the same design. All data collection procedures were appropriate and complied with except for the V-wave measurement. H reflex threshold decreased and s50 and slope increased in the participants who received chiropractic spinal manipulation. H reflex threshold increased and s50 and slope decreased in the participant who received the passive control intervention. Changes in MVC force were inconsistent between subjects. Statistical efficacy was not evaluated as the study was designed to measure feasibility only. Recommendations for further research, including changes in recruitment strategy, are provided. Conclusions: This study answered some important feasibility questions about conducting a large scale randomized controlled study measuring the effect of chiropractic spinal manipulation on motor neuron excitability and muscle strength in children with CP. Some aspects proved feasible, such as H reflex recordings, and some aspects need to be altered for any future research in this area.