Multisite Transcutaneous Spinal Stimulation for Walking and Autonomic Recovery in Motor-Incomplete Tetraplegia: A Single-Subject Design

Abstract

Objective This study investigated the effect of cervical and lumbar transcutaneous spinal cord stimulation (tSCS) combined with intensive training to improve walking and autonomic function after chronic spinal cord injury (SCI). Methods Two 64-year-old men with chronic motor incomplete cervical SCI participated in this single-subject design study. They each underwent 2 months of intensive locomotor training and 2 months of multisite cervical and lumbosacral tSCS paired with intensive locomotor training. Results The improvement in 6-Minute Walk Test distance after 2 months of tSCS with intensive training was threefold greater than after locomotor training alone. Both participants improved balance ability measured by the Berg Balance Scale and increased their ability to engage in daily home exercises. Gait analysis demonstrated increased step length for each individual. Both participants experienced improved sensation and bowel function, and 1 participant eliminated the need for intermittent catheterization after the stimulation phase of the study. Conclusion These results suggest that noninvasive spinal cord stimulation might promote recovery of locomotor and autonomic functions beyond traditional gait training in people with chronic incomplete cervical SCI. Impact Multisite transcutaneous spinal stimulation may induce neuroplasticity of the spinal networks and confer functional benefits following chronic cervical SCI.

Enhanced selectivity of transcutaneous spinal cord stimulation by multielectrode configuration

“…This selection was deliberate to facilitate a conservative analysis of recruitment mechanisms in a "worst-case" scenario. Routine applications of tSCS use stimulation amplitudes between 0.8 and 1.2 times the motor threshold to enhance motor function after paralysis (Hofstoetter et al, 2013;Inanici et al, 2021;Minassian et al, 2016;Samejima et al, 2022). As these amplitudes are considerably lower than saturation, we expect the probability of directly recruiting anterior roots in a therapy setting to be lower than those reported here.…”

“…Transcutaneous SCS (tSCS) offers a promising non-invasive alternative to engage paralyzed muscles below the injury by activating the same neural structures via similar mechanisms as epidural SCS (Danner et al, 2011;Ladenbauer et al, 2010;Minassian et al, 2007a). Recent work suggests that it may be possible to achieve similar rehabilitative outcomes through this non-invasive approach (Al'joboori et al, 2020;Inanici et al, 2021;Samejima et al, 2022;Shapkova et al, 2020). However, the low selectivity of tSCS compared to epidural SCS (Hofstoetter et al, 2018) may limit the types and number of movements that can be enabled by it and, thus, its potential applications in exercise-based rehabilitation strategies.…”

Transcutaneous spinal stimulation in people with and without spinal cord injury: Effect of electrode placement and trains of stimulation on threshold intensity

“…This enables therapeutic stimulation intensity to be set relative to this threshold and standardized between participants. However, no consensus on what amount of stimulation relative to threshold intensity has been established: some stimulate at threshold intensity (Siu et al, 2022), while others stimulate above (Minassian et al, 2016;Shapkova et al, 2020;Zaaya et al, 2021) or below threshold intensity (Hofstoetter et al, 2020;Hofstoetter, Krenn, et al, 2015;Momeni et al, 2022;Samejima et al, 2022). Since relevant muscles may have different threshold intensities for evoking sEMR, setting the therapeutic intensity based on the first recruited muscle will result in all other muscles being stimulated at subthreshold intensities; the opposite problem exists if stimulation intensity is set based on the threshold intensity of the last recruited muscle.…”

High-Frequency Stimulation Does Not Improve Comfort of Transcutaneous Spinal Cord Stimulation

“…tSCS is a more accessible neuromodulation therapy that could potentially reach people without access to surgical procedures or those who are contra-indicated or unwilling to receive a SCS implant. To date, tSCS has been demonstrated as an effective method to improve motor function in the arm and hand (Freyvert et al, 2018;Gad et al, 2018;Inanici et al, 2021Inanici et al, , 2018, trunk (Keller et al, 2021;Rath et al, 2018;Sayenko et al, 2019), and legs (Gad et al, 2017(Gad et al, , 2019Hofstoetter et al, 2013Hofstoetter et al, , 2015bHofstoetter et al, , 2021Samejima et al, 2022) in people with various neurological conditions. tSCS (and SCS) excite the large-diameter afferents in the spinal roots (Hofstoetter et al, 2019(Hofstoetter et al, , 2018, engaging spinal reflex pathways that facilitate activity in motoneurons.…”