The swimming test is effective for evaluating spasticity after contusive spinal cord injury.

Youngjae Ryu,Naoki Fujita,Taku Kitamura,Yoshinori Ichihara,Ryohei Nishimura,Toru Ogata,Masami Akai,Yasuhiro Sawada,Motoshi Nagao,Kazuhito Morioka,Toru Doi,Michael G Fehlings

doi:10.1371/journal.pone.0171937

Abstract

Spasticity is a frequent chronic complication in individuals with spinal cord injury (SCI). However, the severity of spasticity varies in patients with SCI. Therefore, an evaluation method is needed to determine the severity of spasticity. We used a contusive SCI model that is suitable for clinical translation. In this study, we examined the feasibility of the swimming test and an EMG for evaluating spasticity in a contusive SCI rat model. Sprague-Dawley rats received an injury at the 8th thoracic vertebra. Swimming tests were performed 3 to 6 weeks after SCI induction. We placed the SCI rats into spasticity-strong or spasticity-weak groups based on the frequency of spastic behavior during the swimming test. Subsequently, we recorded the Hoffman reflex (H-reflex) and examined the immunoreactivity of serotonin (5-HT) and its receptor (5-HT2A) in the spinal tissues of the SCI rats. The spasticity-strong group had significantly decreased rate-dependent depression of the H-reflex compared to the spasticity-weak group. The area of 5-HT2A receptor immunoreactivity was significantly increased in the spasticity-strong group. Thus, both electrophysiological and histological evaluations indicate that the spasticity-strong group presented with a more severe upper motor neuron syndrome. We also observed the groups in their cages for 20 hours. Our results suggest that the swimming test provides an accurate evaluation of spasticity in this contusive SCI model. We believe that the swimming test is an effective method for evaluating spastic behaviors and developing treatments targeting spasticity after SCI.

Highlights

Spasticity is a common complication after traumatic spinal cord injury (SCI)
Given that some of the common spastic symptoms observed after SCI include hyperreflexia, clonus, hypertonus of the muscles, and muscular spasm in both human patients and animal models [4, 26], we postulated that the clonus phase and the spastic phase observed during swimming represent the spastic symptoms of contusive SCI rats
The symptoms of spasticity in the contusive SCI rat model were observed during the swimming test

Summary

Introduction

Spasticity is a common complication after traumatic spinal cord injury (SCI). Traumatic disconnection between the upper and lower motor neurons is known to result in hyperexcitability of spinal circuits and subsequent spastic symptoms, including muscle spasms, muscular hypertonia, and clonus [1,2,3,4,5]. Spasticity frequently impairs voluntary motor control, and its severity varies among individuals with SCI. Swimming test for spasticity patients with SCI present with muscle spasticity, whereas others have reported that 50–60% of patients complain of spastic symptoms that interfere with voluntary motion [2, 6, 7]. To improve upon and develop new spasticity-targeted therapeutic interventions, the underlying mechanisms of spasticity and voluntary motor control need to be elucidated

Methods

Results

Conclusion