Spinal stimulation for upper and lower extremity motor recovery after spinal cord injury

Abstract

Paralysis as a result of spinal cord injury severely impairs control and movement of the extremities. Individuals living with spinal cord injury report significant difficulty with activities of daily living, which can lead to limited mobility and participation within the community. Depending upon the level of injury, restoring movement in the upper and lower extremities is a top priority. Current clinical practice uses exercise-based rehabilitation strategies to facilitate motor recovery after spinal cord injury. The overall effectiveness of exercise alone for movement restoration, however, is limited. Recently, neuromodulation of the spinal cord through electrical and optogenetic stimulation has shown promise as technologies enabling greater movement recovery. Therefore, the aims of this dissertation are to 1) review the history and use of electrical and optogenetic stimulation after spinal cord injury, 2) explore the immediate effects of transcutaneous spinal stimulation on exoskeleton-assisted walking, 3) develop a filtering technique to remove stimulation artifact in surface electromyography recordings, and 4) compare the long-term effects of epidural electrical vs. optogenetic spinal stimulation for forelimb recovery. The immediate effects of transcutaneous electrical spinal stimulation on exoskeleton-assisted walking were assessed in six participants. Stimulation enabled most participants to improve their walking performance, as evidenced by faster gait speeds, reductions in exoskeleton-assistance for stepping, and better muscle coordination. Additionally, we adapted a filtering approach to specifically remove stimulation artifacts while preserving electromyography signals in the same six participants. Lastly, we compared forelimb recovery after a cervical spinal cord injury in rats across three groups: exercise alone, epidural electrical stimulation with exercise, and optogenetic stimulation with exercise. Both stimulation approaches facilitated more recovery compared to exercise alone, with optogenetic stimulation demonstrating a nearly two-fold improvement compared to electrical stimulation. The evidence in this dissertation shows that stimulation of the spinal cord is effective for enabling greater recovery of movement and control of the extremities after spinal cord injury.