Task specific spinal cord epidural stimulation enables independent stepping in motor complete humans
Angeli C, Harkema S
University of Louisville, Louisville, KY, USA
Objective: Various studies in the animal model have shown recovery of stepping with spinal cord epidural stimulation following a spinal cord injury. Our group had shown that epidural stimulation of lumbosacral spinal cord, combined with activity based training, enabled four motor complete paraplegics to progressively regain full weight bearing standing and achieve voluntary movement of their lower extremities. The objective of this study is to describe the effects of task-specific epidural stimulation in combination with intense step training in seven individuals with a motor complete injury.
Design/Method: Seven individuals with a motor complete injury (3 AIS-B and 4 AIS-A) implanted with an epidural electrode array over the L1-S1 segments of the spinal cord participated in this study. Individuals received intense step training with step-scES and stand training with stand-scES for 160 sessions. EMG, kinematics and ground reaction forces were recorded during stepping on a treadmill with body weight support.
Results: Various levels of stepping independence where achieved following intense task-specific training with scES. All individuals achieved the ability to generate independent portions of the step cycle when scES and intent to step were present. Three individuals were able to independently generate a full step cycle when the lumbosacral spinal cord was stimulated with individual-specific parameters optimal for stepping following 20-60 training sessions. Intention to step a specific leg (left or right or both) was needed for independent stepping to occur. The appropriate state of excitability, proprioception, and intent was required for independent stepping. The level of independence appeared to correlate with the intensity and type of task specific training.
Conclusion: These results have important implications with respect to identifying strategies that are likely to be most efficacious in enabling improved motor function for stepping after motor complete paralysis. This study provides preliminary evidence that the combination of intense step training with task-specific step-scES promotes significant plasticity in the spinal circuitry leading to functional improvements during stepping.
Support: NIGMS P30 GM103507, the Leona M. and Harry B. Helmsley Charitable Trust, the Christopher & Dana Reeve Foundation, Kessler Foundation, Kentucky Spinal Cord Injury Research Center, and Medtronic Inc.
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