Spinal Cord Stimulation for Functional Recovery in Humans with Tetraplegia

Abstract/summary Arm and hand movements are essential for daily-life functions and are largely impaired in veterans with cervical spinal cord injury (SCI). Promising results have been reported on the effects of transcutaneous electrical spinal stimulation (TESS) on arm and hand functional recovery, however, the effects remain limited and this method has not yet entered clinical practice. Our specific goals are to: 1) examine physiological effects of TESS on upper-limb muscles after cervical SCI, and 2) maximize the recovery of arm and hand function by using tailored TESS in a task-specific manner combined with motor training. We focus on reaching and grasping movements because of their importance in daily life activities. Thus, our results may have a direct impact on the quality of life of veterans and their caregivers by enhancing their independence and level of care. [In Aim 1, we will investigate the effects of TESS on cortical and subcortical neuronal pathways including the reticulospinal pathway, intracortical inhibition in the primary motor cortex, and in their interaction. Transcranial magnetic stimulation (TMS) will be used to examine transmission in intracortical pathways within the primary motor cortex and a loud acoustic stimuli will be used to engage reticulospinal inputs. In Aim 2, we propose to maximize the effects of TESS on recovery of arm and hand function by applying TESS in a task-specific manner during the reaching or the grasping phases of movements followed up by massed practice training. TESS will be applied using a novel closed-loop paradigm that relies on ongoing kinematic signals to trigger stimulation in a task-dependent manner in Veterans with chronic cervical SCI.] Training activities will focus on intrinsic and extrinsic muscles of the hand and arm movements using the virtual reality RAPAEL Smart Glove. These unique approaches aiming at promoting neuroplasticity during functionally relevant movements using targeted task- specific TESS have not been used before. The proposed experiments will provide new knowledge on the control of upper-limb functions, which will be used to guide functionally-relevant plasticity-inducing protocols to enhance recovery of hand and arm function. The absence of well-accepted treatments for upper-limb motor impairments for veterans with cervical SCI and the limited behavioral gains of present interventions underline the importance of these investigations.