Grant: Project Grant

Nearly 1.6 million people live with paralysis resulting from traumatic or non-traumatic spinal cord injury (SCI) in North America, of whom >50% never recover the ability to walk. Electrical stimulation of nerves and muscles has been one of the few interventions to date to provide functional improvements after SCI; however, restoring functional walking has remained an unresolved challenge. An alternative electrical stimulation approach for restoring walking focuses on stimulating the spinal cord. Two paradigms of spinal cord stimulation have shown great potential: epidural spinal cord stimulation (ESCS) and intraspinal microstimulation (ISMS). Both activate spinal networks in the same small region of the spinal cord, but through different pathways. Exciting new results suggest that ESCS, coupled with extensive physical therapy, may restore some ability to walk (up to 100 m) for people experiencing severe SCI. Also exciting are results from ISMS work done in animals that show that ISMS can restore long distances of walking (close to 1 kilometer)! However, despite the compelling findings, it remains unknown how ESCS or ISMS work, and which neural networks in the spinal cord they activate. It is also unknown how long-term use of ESCS or ISMS can change the neural networks in the spinal cord, how much they are dependent on extensive physical therapy to produce good functional outcomes, and how effective they are in restoring stable and sustained walking. This proposal will systematically address these unknowns in the adult Yucatan pigs. This strain of pigs has spine and spinal cord anatomies that best resemble those of humans. Therefore, the findings from this project can be readily translated to humans. Very importantly, the results of this pivotal study will be crucial for determining the suitability of ESCS and ISMS for restoring meaningful distances of walking after severe SCI, and will guide the use of these stimulation strategies in persons experiencing SCI.