Closed loop control of vibration for muscle spasms after human spinal cord injury: efficacy and mechanism

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ABSTRACT Involuntary muscle activity (spasms) is the most debilitating aspect of spasticity after spinal cord injury (SCI) because the contractions interfere with everyday tasks, and limit rehabilitation. Treatments are not always effective, lowering health- related quality of life. Our long-term Objective is to use closed-loop control of tendon vibration to implement clinically meaningful management of muscle spasms, and to understand the spinal circuits responsible for spasm generation. Specifically, we aim to build on our existing capabilities and collaborations to: 1a) Refine the design of the housing in our wearable device to deliver vibration to the Achilles tendon by using consumer-oriented input; 1b) Determine the vibration parameters that reduce spasms in leg muscles paralyzed by SCI in the laboratory using the wearable device. In either a seated or reclined position, spasms will be detected using electromyography (EMG), then the Achilles tendon will be vibrated at different frequencies, durations and amplitudes to dampen the spasms in real-time using closed-loop control; 2) Examine the efficacy of tendon vibration in altering muscle spasms by treating spasms as they occur, which personalizes the intervention for maximal clinical and user impact. The acute (chronic) effects of vibration on spasms will be evaluated during 24-hour EMG recordings by comparing unconditioned to conditioned spasms at baseline, during the vibration intervention, and post intervention. Pre/Post measures of different aspects of spasticity will provide insight into the site(s), magnitude, and time-course of changes that occur with vibration; and user perspective on the effects of the therapy. Combining the power of non-invasive physiological recordings with functional, clinical and participant reported outcomes will also reveal neural and muscular plasticity, the mechanisms underlying the action of vibration on spasms, and importantly, the rationale to improve this novel approach to spasm management after SCI and other neurological disorders. Many individuals with SCI may find non-pharmacological treatment for spasms attractive because it may lead to reductions or elimination of spasm medications.