Transcutaneous spinal stimulation as a therapeutic strategy for spinal cord injury: state of the art

Abstract

Treatments for spinal cord injury (SCI) still have limited effects. Electrical stimulation might facilitate plastic changes in affected spinal circuitries that may be beneficial in improving motor function and spasticity or SCI-related neuropathic pain. Based on available animal and clinical evidence, we critically reviewed the physiological basis and therapeutic action of transcutaneous spinal cord stimulation in SCI. We analyzed the literature published on PubMed to date, looking for the role of three main noninvasive stimulation techniques in the recovery process of SCI and focusing mainly on transcutaneous spinal stimulation. This review discusses the main clinical applications, latest advances, and limitations of noninvasive electrical stimulation of the spinal cord. Although most recent research in this topic has focused on transcutaneous spinal direct current stimulation (tsDCS), we also reviewed the technique of transcutaneous electric nerve stimulation (TENS) and neuromuscular electrical stimulation (NMES) as potential methods to modulate spinal cord plasticity. We also developed a finite element method (FEM) model to predict current flow in the spinal cord when using different electrode montages. We identified gaps in our knowledge of noninvasive electrical stimulation in the modulation of spinal neuronal networks in patients with SCI. tsDCS, TENS, and NMES have a positive influence on the promotion of plasticity in SCI. Although there are no randomized controlled studies of tsDCS in SCI, preliminary evidence is encouraging. FEMs predict that tsDCS electrode montage can be used to shape which spinal segments are modulated and what detailed areas of spinal anatomy can concentrate current density (eg, spinal roots). tsDCS is a technique that can influence conduction along ascending tracts in the spinal cord, so could modulate supraspinal activity. It may also be a promising new approach for a number of neuropsychiatric conditions.

Neural Substrates of Transcutaneous Spinal Cord Stimulation: Neuromodulation across Multiple Segments of the Spinal Cord

“…Neuromodulation of the spinal cord by means of non-invasive transcutaneous (tSCS) and implanted epidural (eSCS) spinal cord stimulation may improve sensorimotor rehabilitation after spinal cord injury (SCI) [1][2][3][4]. However, developing an optimal treatment approach requires taking advantage of the intrinsic ability of the spinal circuits by facilitating preserved sensorimotor pathways that could drive spinal plasticity [5]. The influence of spinal cord stimulation (SCS) does not necessarily depend on the nature of the neurological disorder, but on the operational and functional status of residual neural networks [6].…”

Backward locomotor treadmill training combined with transcutaneous spinal direct current stimulation in stroke: a randomized pilot feasibility and safety study

“…Supported by electrical current modelling ( Parazzini et al , 2014 ; Fregni et al , 2015 ; Fiocchi et al , 2016 ; Kuck et al , 2017 ), preclinical ( Zaghloul, 2014 , 2016 ; Weiguo et al , 2015 ), neurophysiologic ( Cogiamanian et al , 2012 ; Priori et al , 2014 ) and neuroimaging studies ( Schweizer et al , 2017 ), a growing body of literature suggests that tsDCS can modulate activity at multiple levels of the central nervous system, including the segmental spinal cord ( Winkler et al , 2010 ; Lamy et al , 2012 ; Hubli et al , 2013 ), ascending lemniscal and nociceptive pathways ( Cogiamanian et al , 2008 ; Cogiamanian et al , 2011 ; Truini et al , 2011 ), as well as cortical regions ( Bocci et al , 2014 , 2015 a , b , c ; Marangolo et al , 2017 ; Schweizer et al , 2017 ). In addition, a recent proof-of-concept study from our group, in young and neurologically intact individuals, found that anodal tsDCS applied over the lower thoracic region (T-11) concurrently with BLTT, increased the acquisition rate and retention of backward walking speed up to 2 weeks post-training ( Awosika et al , 2019 ).…”

Transcutaneous spinal direct current stimulation improves locomotor learning in healthy humans

“…Given these findings, previous modeling and electrophysiological studies attempted to modulate subcortical function using DCS applied over the spine (tsDCS). These studies demonstrated that tsDCS could indeed modulate spinal cord function (17,19,20,29,31,32,59,60), raising the question whether it could also influence locomotor behavior. In this investigation, we used the same montage and stimulating parameters reported to modulate electrophysiological measures of spinal cord function to address a novel question: could tsDCS modulate locomotor behavior in the form of learning a novel backward task of relevance in sports medicine and neurorehabilitation (61)(62)(63)(64)(65)(66)(67)(68)(69)(70).…”

“…provided mechanistic foundation to these empirical findings (29)(30)(31)(32). It is then possible that tsDCS could also influence locomotor learning.…”