Self-Assisted Standing Enabled by Non-Invasive Spinal Stimulation after Spinal Cord Injury

Abstract

Neuromodulation of spinal networks can improve motor control after spinal cord injury (SCI). The objectives of this study were to (1) determine whether individuals with chronic paralysis can stand with the aid of non-invasive electrical spinal stimulation with their knees and hips extended without trainer assistance, and (2) investigate whether postural control can be further improved following repeated sessions of stand training. Using a double-blind, balanced, within-subject crossover, and sham-controlled study design, 15 individuals with SCI of various severity received transcutaneous electrical spinal stimulation to regain self-assisted standing. The primary outcomes included qualitative comparison of need of external assistance for knee and hip extension provided by trainers during standing without and in the presence of stimulation in the same participants, as well as quantitative measures, such as the level of knee assistance and amount of time spent standing without trainer assistance. None of the participants could stand unassisted without stimulation or in the presence of sham stimulation. With stimulation all participants could maintain upright standing with minimum and some (n = 7) without external assistance applied to the knees or hips, using their hands for upper body balance as needed. Quality of balance control was practice-dependent, and improved with subsequent training. During self-initiated bodyweight displacements in standing enabled by spinal stimulation, high levels of leg muscle activity emerged, and depended on the amount of muscle loading. Our findings indicate that the lumbosacral spinal networks can be modulated transcutaneously using electrical spinal stimulation to facilitate self-assisted standing after chronic motor and sensory complete paralysis.

Reversing 21 years of chronic paralysis via non‐invasive spinal cord neuromodulation: a case study

“…Although recent transcutaneous spinal cord stimulation studies have shown improvement of trunk control during sitting 16 and self‐assisted standing 17 in individuals with SCI, this is the first study to show that tES can facilitate volitional movements in the completely paralyzed leg of a SCI patient after just 16 weeks of stimulation and training. This finding is comparable with previous research using invasive epidural electrical stimulation on a motor complete paraplegic patient regaining volitional movements of lower limbs after stimulation and training 4 .…”

“…Transcutaneous electrical stimulation (tES) is a non‐invasive neuromodulation method to activate neural circuits via electric current between a pair of stimulating electrodes placed onto the skin. The tES to SCI patients has recently demonstrated successful activation of motor pools of distal muscles, 7 facilitation for standing, 8 and inducing stepping‐like movements in a gravity‐neutral position 9 . However, tES has not yet exhibited full restoration of voluntary movements of paralyzed limbs, independent full‐weight‐bearing standing, or bipedal stepping without any assistance in paralyzed patients.…”

The relationship between maximum tolerance and motor activation during transcutaneous spinal stimulation is unaffected by the carrier frequency or vibration

“…Regardless of the exact mechanism, the ratio between tolerance and spinally evoked motor potentials has to be considered when choosing a stimulation paradigm for studies that require TSS‐induced motor activation for functional outcomes (e.g., for standing such as in Sayenko et al, 2019). On the other hand, previous studies have demonstrated the TSS can be used to facilitate other functions such as rhythmic motions (Gerasimenko et al, 2015), trunk stability (Rath et al, 2018), cardiovascular function (Phillips et al, 2018), and bladder function (Gad et al, 2018) in individuals with spinal cord injury, without directly inducing motor responses.…”

“…As such, mechanisms of spinal neuromodulation may also include activation of spinal interneural networks and antidromic activation of ascending fibers in the dorsal columns. TSS has been used to increase excitability at multiple levels of the spinal neuraxis to enable motor and autonomic functions in individuals with chronic spinal cord injury (SCI) (Gad et al, 2018; Hofstoetter et al, 2013, 2015; Minassian et al, 2013, 2016; Phillips et al, 2018; Rath et al, 2018; Sayenko et al, 2019). Although TSS has been examined as a possible clinical intervention for individuals with SCI, the promising findings with regard to motor recovery and the noninvasive nature of the technique could make TSS suitable for use with other neurologically‐impaired populations.…”

“…Previous studies have suggested that it may be possible to reduce discomfort during TSS by using a specific waveform to deliver electrical stimulation (Gad et al, 2018; Gerasimenko et al, 2015, 2016; Rath et al, 2018; Sayenko et al, 2019). The waveform consists of 0.1–1 ms bursts of alternating biphasic rectangular pulses with a carrier frequency of up to 10 kHz.…”