Whole-body Neuroprosthetic Approach for Incomplete Cervical Spinal Cord Injury

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 DESCRIPTION (provided by applicant): Spinal cord injury (SCI), particularly at the cervical level, is one of the most debilitating injures that can be sustained, and is more common in the veteran population than the civilian population. Restoration of hand function is the top priority for individuals with mid-cervical SCI and the existing alternatives for providing hand function for these individuals are inadequate. Upper extremity neuroprostheses have been shown to provide increased independence for individuals with cervical level spinal cord injury (SCI) that is significantly better than the functional improvements that can be achieved through any other intervention. Neuroprostheses use electrical stimulation to activate paralyzed muscles in a coordinated manner. When combined with myoelectric control and tendon transfer procedures, neuroprostheses maximize the use of each subject's voluntary and paralyzed musculature to provide significant improvement in activities of daily living. However, these upper extremity neuroprostheses have not, to date, been systematically implemented and evaluated in individuals with incomplete SCI. Individuals with incomplete SCI have increased heterogeneity in their voluntary function, innervation patterns, and functional goals. The goal of this proposal is to develop a comprehensive strategy for maximizing the function that can be provided to individuals with incomplete cervical SCI, with a focus on neuroprosthetic intervention. The relative percentage of incomplete to complete SCI has been increasing over time due to a variety of factors particularly improved emergency and trauma treatment, resulting in sparing of at least some tracts in the injured cord. This sparing allows voluntary function below the level of injury. For some individuals, this spared function is significant and greatly increases voluntary function. However, there remains a substantial cohort of individuals with cervical SCI who are classified as "incomplete" (Typically ASIA Impairment Scale Group B and C) but for whom much of their voluntary muscle activity is too weak to provide a significant functional benefit. Our fundamental hypothesis in this proposal is that this voluntary function can be harnessed electronically, using myoelectrically controlled neuroprosthetic intervention, to provide significantly enhanced function for these individuals. Specifically, even muscles that produce only weak twitch responses (muscle grade 1) produce easily detectable myoelectric signals which can be utilized for the control of other stimulated muscles. Every weak muscle under voluntary control provides an additional source of control for neuroprosthetic interventions, and these new control sources can be harnessed to control multiple functions as needed for each individual. The goals of this project are to: 1) develop a comprehensive screening assessment strategy for the implementation of neuroprosthetics for incomplete cervical SCI subjects, 2) implant an advanced, fully- implanted, modular neuroprosthetic system in eight incomplete SCI subjects and evaluate the resulting functional outcomes, 3) evaluate the utility of implanted neuroprostheses through analysis of home use of the functions available, and 4) gain preliminary data regarding possible strengthening and recovery of function in incomplete SCI as a result of increased use of the extremity. The overall outcome of this proposal will be to significantly expand the patient population that can benefit from implanted neuroprosthetic systems, particularly to those with incomplete cervical SCI.