Transcutaneous Spinal Stimulation: Safety and Feasibility for Trunk Control in Children With Spinal Cord Injury

Overview

Paralysis of trunk muscles and the inability to sit upright is one of the major problems facing adults and children with spinal cord injury (SCI). Activity-based locomotor training has resulted in improved trunk control in children with spinal cord injury, though full recovery is not achieved in all children. Transcutaneous spinal stimulation' (TcStim), a stimulation applied over the skin to the sensory nerves and spinal cord, is a promising tool that may further enhance improvements to trunk control. The purpose of this study is to determine the feasibility (can we do it) and safety of Transcutaneous Stimulation (TcStim) in children with SCI to acutely improve sitting upright and when used with activity-based locomotor training (AB-LT). Thus, can we provide this therapy to children and do so safely examining a child's immediate response and cumulative response relative to safety and comfort. Eight participants in this study will sit as best they can with and without the stimulation (i.e. stimulation applied across the skin to the nerves entering the spinal cord and to the spinal cord) and their immediate response (safety, comfort, trunk position) recorded. Then, two participants will receive approximately 40 sessions of activity-based locomotor training in combination with the stimulation. Their cumulative response of stimulation (i.e. safety, comfort, feasibility) across time will be documented. Participation in this study may last up to 3 days for the 8 participants being observed for acute response to stimulation and up to 9 weeks for the participants being observed for cumulative response to training with stimulation. We will monitor the participants throughout the testing and training for their response to the stimulation (i.e. safety) and their comfort.

Similar to adults, children with severe spinal cord injury (SCI) suffer the devastating consequences of limb and trunk muscle paralysis rendering them unable to sit upright, stand, or walk. Unique to pediatric-onset SCI, nearly 100% of children injured under the age of 10 develop neuromuscular scoliosis with approximately 65% requiring surgical intervention. Given the importance of muscle activity and load-bearing for musculoskeletal development, SCI-induced trunk muscle paralysis during rapid growth contributes significantly to the onset and progression of scoliosis. Current physical rehabilitation interventions after pediatric-onset SCI are based on the premise of permanence of SCI-induced paralysis and the inability to restore intrinsic trunk control. As a result, thoraco-lumbosacral braces remain the standard of care for upright sitting support without clear efficacy for reducing the incidence of neuromuscular scoliosis. Advances in rehabilitation after SCI, for adult and pediatric populations, capitalize on the intrinsic capacity of spinal neuronal networks for generation of motor output below the lesion in response to sensory input during activity-based locomotor training (AB-LT). Our recent work demonstrated remarkable improvements in trunk control as measured by the Segmental Assessment of Trunk Control (SATCo) in all 21 participants with SCI, age range: 17 months-12 years at enrollment and mean time since injury 1.5 years (range 1 month-6 years), receiving AB-LT across 60 sessions. Sensory-afferent driven activation of the intrinsic synergies between the lower limb and trunk extensor muscles above, across and below the lesion likely underlies the physiological adaptations responsible for these gains. While all children improved, not all attained full trunk control. Incorporation of neuromodulatory techniques, such as epidural spinal cord stimulation, further challenges the limits for SCI recovery previously thought possible. There are recent reports of individuals with chronic complete SCI regaining the capacity to stand and walk with stimulation. Transcutaneous spinal stimulation (TcStim) provides a non-invasive neuromodulatory tool that may, similar to epidural stimulation, increase the central state of excitability below the lesion, thereby enabling greater capacity for integration of sensory input and augment motor output to potentiate trunk motor recovery. Children with SCI may not only benefit from novel neurotherapeutic interventions, but also may demonstrate even greater improvements due to inherent plasticity present during development. Previous studies demonstrated the efficacy of TcStim to acutely improve sitting posture and trunk muscle activation in adults with SCI. In children with cerebral palsy, TcStim combined with AB-LT significantly improved locomotion compared to AB-LT alone. Our overall objective is to demonstrate 'proof-of-principle', as a necessary first step, that TcStim is a feasible and safe approach to a therapeutic intervention targeting trunk control in children with SCI. If found to be feasible and safe, then future studies will employ TcStim in combination with restorative rehabilitation for children with SCI to examine the effect on trunk control.