Restorative Neuromodulation for Lower Extremity Functions

Overview

The overall objective of the proposed study is to restore lower-extremity functions of paraplegic individuals. Paralysis following Stroke or spinal cord injury (SCI) result harsh sufferings including lifelong dependence on wheelchairs and thus often life threatening conditions such as pressure sore resulted from the immobility. Recently, electrical stimulation targeting the lumbosacral spinal cord has shown activation of spinal circuits that control standing and walking functions; while body-weight supported locomotor training has shown overall health improvement of the paraplegic patients through activity dependent rehabilitation. In the current project we aim to combine the trans-spinal electrical stimulation and locomotor training in an efficient, cost-effective and simplified manner for functional rehabilitation. In this proposed study, Stroke and SCI paraplegics will be regularly trained to stand and walk on a body-weight support system with the aid of lower-limb orthoses and trans-spinal electrical stimulation. In progressive weeks the orthotic support of the lower-limb would be slowly lifted off and only the stimulation therapy will be delivered during the locomotor training. Repetitive training with this combination therapy, the spinal pathways would likely reorganize and would promote long-term rehabilitation of the lower-extremity. After successful demonstration of this in our laboratory settings, we aim to transform this technology for community use.

Spinal cord is composed of specialized neural networks, capable of executing different functions. Although the command for lower-limb functions such as standing and walking is primarily delivered from the brain, it was found that the spinal cord circuits not only execute it but also maintain the task and control the dynamics with proper feedback mechanisms with it's reflex circuitry. Simple bipedal standing and walking requires spatiotemporal coordination of muscles, limb joints, balance etc., their adaptation and control in gravity. For human, these physiological activities are well choreographed by sets of neural networks. In combination with afferent proprioceptive inputs, these network circuits work with the motor periphery to generate a series of motor acts during each task. Normally, the activity of these spinal networks are regulated supraspinally and by peripheral sensory inputs. In case of the loss of supraspinal inputs, resultant of a Stroke or spinal cord injury (SCI), motor tasks maybe enabled by directly activating these specialized spinal cord networks via external stimuli. Recent studies have demonstrated that neuromodulation via spinal cord stimulation can effectively restore lower-extremity functions in patients with chronic neurological injuries. Traumatic injury to the central nervous system (CNS) such as SCI is devastating events leaving patients with impairment of motor, sensory and autonomic functions. Mainstay for the treatment is still limited to rehabilitation by physical therapy and training. In few patients, however, neuroplasticity and repair mechanisms are considered to contribute to recovery of paresis in the acute stage of the injury and stops in the chronic stage. But, recent groundbreaking studies have shown that the recovery can be further amplified in the chronic stage by the novel treatment of trans-spinal electrical stimulation. However, the rehabilitation related to this recovery is not very significant, and thus it is a challenge to be convinced with the efficacy of this new therapy. A combination therapy of trans-spinal electrical stimulation along with body-weight would promote better recovery and benefit the patients more. The current study will further assist the researchers to design such combinational therapeutic intervention for neurologically impaired patients to stimulate to walk again. Successful translation of this novel technology would facilitate the paraplegic community to become more healthy, independent and happy.