Multisite Transspinal Stimulation for Augmenting Recovery in Spinal Cord Injury

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The main objective of this hypothesis-based and need-driven clinical research trial is to develop novel rehabilitation strategies and impact clinical practice and care for people with spinal cord injury (SCI). The investigators will use non-invasive transspinal stimulation over the cervical and lumbosacral enlargements, the spinal location of arm and leg motor circuits, to augment the benefits of locomotor training and improve recovery of standing and walking ability in individuals with SCI. This trial is a pilot (or small-scale) clinical trial on cervical and lumbosacral transspinal stimulation administered alone at rest or during assisted step training in people with SCI to establish safety and efficacy. The investigators' specific aims are as follows: 1. Determine the underlying physiological actions of paired cervical and lumbosacral transspinal stimulation in people with and without SCI. To address Specific Aim 1, in 12 people with incomplete SCI (AIS B, C, D) and 12 healthy control subjects (age and gender match) we will establish the effects of a) cervical transspinal stimulation on soleus H-reflexes and leg transspinal evoked potentials (TEPs), and the effects of lumbosacral transspinal stimulation on flexor carpi radialis (FCR) H-reflexes, and arm TEPs at rest; and b) the effects of cervical and lumbosacral paired transspinal stimulation on joint coordination and muscle synergies during walking on a motorized treadmill (healthy controls) or with a robotic gait system training (Lokomat) in participants with SCI. 2. Determine if cervical and lumbosacral transspinal stimulation reconnects the injured human spinal cord, strengthens the weak remnant neuronal pathways, and augments the benefits of locomotor training. To address Specific Aim 2, a total of 24 people with incomplete SCI (AIS B, C, D) will be enrolled. Half will receive cervical and lumbosacral transspinal stimulation at rest. The other half of participants will receive cervical and lumbosacral transspinal stimulation during assisted stepping with a robotic gait system (Lokomat 6 Pro®). Both groups will receive 20 sessions (5 sessions/week) of 1-hr duration each. Cervical and lumbosacral transspinal stimulation will be delivered at 30 Hz at or above paresthesia intensities based on each participant's comfort levels. For both groups, the investigators will establish safety based on adverse events, and efficacy based on clinical assessments and neurophysiological biomarkers. Before and after the intervention the investigators will 1) establish changes in non-somatic vital bladder, bowel, and sexual body functions, 2) perform clinical assessments of spasticity, standing and walking ability, and 3) perform state-of-the-art experiments to establish changes in neurophysiological biomarkers. The investigators will use neurophysiological biomarkers to probe actions of the proposed intervention (cervical and lumbosacral transspinal stimulation), use combination of interventions, and address safety and efficacy of intervention via adverse events and neurophysiological biomarkers. Furthermore, the investigators will 1) identify and validate biomarkers for diagnosis, prognosis, and evaluation of treatment efficacies, and 2) maximize the function of the residual neural circuitry, including harnessing neuroplasticity and recovery to improve function after SCI.