Activity-based training with spinal cord epidural stimulation for the recovery of standing in individuals with chronic motor complete spinal cord injury
Rejc E, Angeli C, Harkema S
University of Louisville, Louisville, KY, USA
Title: Activity-based training with spinal cord epidural stimulation for the recovery of standing in individuals with chronic motor complete spinal cord injury
Objective: Individuals with chronic, motor complete spinal cord injury (SCI) are unable to stand, walk, or move their lower limbs voluntarily, and the prognosis for recovery of motor function in these individuals is poor. We have shown that chronic, motor complete SCI individuals can progressively recover standing ability when lumbosacral spinal cord epidural stimulation (scES) is applied with task- and individual-specific parameters. The aim of this study was to investigate the effects of two different activity-based training paradigms with scES on standing ability, and to determine whether standing and stepping can be concurrently trained without limiting the recovery of standing in individuals with chronic complete SCI using scES.
Design/Method: Seven individuals with chronic, motor complete spinal cord injury (SCI) were implanted with a spinal cord epidural stimulation unit. Four individuals performed approximately 80 sessions of stand training with scES (5 days/week; 1 hour per session) followed by 80 sessions of step training with scES (Group 1). Three other individuals (Group 2) performed an interleaving stand-step training with scES, which consisted of stand training and step training that alternated every session until the same amount of training as in the previous protocol (~ 160 sessions) was achieved.
Results: After approximately 80 sessions of stand training with scES, the ability to stand overground bearing full body weight improved to different extents in the four research participants of Group 1. In particular, two individuals achieved independent standing while other two individuals needed external assistance for hip extension. However, step training performed afterwards substantially impaired standing in three of the four individuals enrolled in Group 1. Conversely, standing ability improved throughout stand-step training in Group 2, as all the three individuals were able to stand with no external assistance for longer periods of time using less stable upper limb support for balance (i.e. from standing frame to holding the trainer’s hands for balance control). Improved standing ability generally coincided with continuous EMG patterns and constant levels of ground reaction forces, and with the increased evoked potentials amplitude modulation induced by sit to stand transition. Conversely, poorer standing ability was associated with more variable EMG patterns that alternated EMG bursts and longer periods of negligible activity in most of the muscles.
Conclusion: The interleaving stand-step training with scES promoted significant recovery of standing ability in three chronic complete SCI individuals, and seemed more effective than the previous paradigm in which stand training was completed prior to step training. This indicates that the human spinal circuitry can learn to generate motor patterns effective for standing while also stepping, as long as both standing and stepping are practiced. These findings also underline the importance of the trained motor task in driving neural plasticity of spinal networks.
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