Voluntary Leg Movement Enabled after Complete Paralysis Using Noninvasive Spinal Cord Transcutaneous Stimulation, a Case Study.

Abstract

Neuromodulation for the recovery of lower extremity motor function has shown much progress for those living with severe paralysis after spinal cord injury (SCI). Transcutaneous spinal cord stimulation (scTS) has emerged as a noninvasive alternative to epidural stimulation for improving motor function after SCI. However, it is unknown whether a single scTS session can acutely reveal voluntary motor output and enable modulation of movement characteristics without prior stimulation exposure or task-specific training in individuals with clinically motor-complete SCI. The individual was male, 35 years old and injured 13 years prior to enrollment in the study and had no voluntary motor movement below the T8 injury level, rendering the pelvis and legs completely paralyzed. Noninvasive transcutaneous stimulation (30 Hz, 1 ms) was delivered at T11/12 and L1/L2 vertebral levels sequentially with continuous biphasic pulses below motor threshold. The individual was able to volitionally control right knee extension in a seated position with intent, on command, and against resistance and control the rate of movement using the scTS parameters focused on the lumbosacral spinal cord repeatedly within a session without activity-based training. This was reproducible one week and one month later without intervening training. These findings suggest that noninvasive scTS can acutely alter the physiological state of the spinal cord, revealing clinically silent but functionally accessible neural pathways even years after injury and expanding the potential relevance of neuromodulation for individuals with very chronic SCI.