Non-invasive spinal neuromodulation enables stepping in children with complete spinal cord injury.

Abstract

Paralysis is assumed permanent in persons with motor-complete spinal cord injury (SCI). However, spinal epidural stimulation combined with activity-based locomotor training (ABLT) and cognitive intent enabled two adults with motor-complete SCI to walk with a walker. Transcutaneous spinal stimulation (scTS), also capable of promoting a cyclic step-like pattern, might be a viable alternative in children with SCI. These findings prompted our investigation into multimodal neuromodulation training using ABLT (enhancing afferent input), spinal stimulation (scTS), and descending (intent) drive to restore voluntary stepping in children with chronic motor-complete SCI. Five non-ambulatory children (9.6 ± 2.5 years old, 3F, 4 thoracic/1 cervical injury) with chronic (>1 year, 5.2 ± 2.5 years), complete SCI underwent 60 sessions of combined ABLT and scTS training with cognitive intent to step and returned for a 3 to 6-month follow-up. During the first training session in a gravity-neutral position, all five children (5/5) made small reciprocal cycles of the hips/knees in a flexion/extension step-like pattern with stimulation, with increased excursion at session 20 for 5/5 children (right hip excursion increased from 10.1 ± 15.1 to 25.9 ± 21.3 degrees and right knee excursion increased from 9.3 ± 13.9 to 39.6 ± 29.2 degrees, p = 0.02). The children stepped overground at session 50 (P15), 60 (P34), and 20 (P32, P14, P240), voluntarily initiating and alternating left/right leg swings on the treadmill and overground with and without scTS. Three to six months post-training, all children maintained the capacity to step. The parents and children reported unanticipated improvements in sensation, bladder function, proprioception, assist to stand, transfers, and dressing. In children with chronic, motor-complete SCI, multimodal neuromodulation training can potentiate the intrinsic stepping capacity of the spinal locomotor centers to enable voluntary stepping. Remarkably, these enhancements are durable and observed even in the absence of spinal stimulation.