Effects of Transcutaneous Spinal Direct Current Stimulation (tsDCS) in Patients With Chronic Pain: A Clinical and Neurophysiological Study

Abstract

Background and Aims: Chronic pain is a complex clinical condition, often devastating for patients and unmanageable with pharmacological treatments. Converging evidence suggests that transcutaneous spinal Direct Current Stimulation (tsDCS) might represent a complementary therapy in managing chronic pain. In this randomized, double-blind and sham-controlled crossover study, we assessed tsDCS effects in chronic pain patients.Methods: Sixteen patients (aged 65.06 ± 16.16 years, eight women) with chronic pain of different etiology underwent sham and anodal tsDCS (anode over the tenth thoracic vertebra, cathode over the somatosensory cortical area: 2.5 mA, 20 min, 5 days for 1 week). As outcomes, we considered the Visual Analog Scale (VAS), the Neuropathic Pain Symptom Inventory (NPSI), and the components of the lower limb flexion reflex (LLFR), i.e., RIII threshold, RII latency and area, RIII latency and area, and flexion reflex (FR) total area. Assessments were conducted before (T0), immediately at the end of the treatment (T1), after 1 week (T2) and 1 month (T3).Results: Compared to sham, anodal tsDCS reduced RIII area at T2 (p = 0.0043) and T3 (p = 0.0012); similarly, FR total area was reduced at T3 (p = 0.03). Clinically, anodal tsDCS dampened VAS at T3 (p = 0.015), and NPSI scores at T1 (p = 0.0012), and T3 (p = 0.0015), whereas sham condition left them unchanged. Changes in VAS and NPSI scores linearly correlated with the reduction in LLFR areas (p = 0.0004).Conclusions: Our findings suggest that tsDCS could modulate nociceptive processing and pain perception in chronic pain syndromes.

Preferential activation of proprioceptive and cutaneous sensory fibers compared to motor fibers during cervical transcutaneous spinal cord stimulation: A computational study

“…Contrary to what was suggested in previous experimental studies, our simulations therefore showed an sizable contribution of cutaneous fibers to the motor evoked potentials during cervical tSCS [17,52]. While cutaneous afferents may contribute to motor evoked potentials, they may also convey divergent excitatory potentials to relevant spinal nodes and significantly contribute to the rehabilitative potential of non-invasive spinal stimulation [53–55]. Taken together, our results showed preferential recruitment of Aα- and Aβ-sensory fibers compared with α-motor fibers, suggesting large contribution of proprioceptive and cutaneous activations during cervical tSCS.…”

“…However, it is important to note that other parameter selection such as the duration of stimulation [15] and voluntary involvement during stimulation [4] are likely required for effective neuromodulation during cervical spinal stimulation. Taken together, our findings imply that the activation of Aα- and Aβ-sensory fibers during cervical tSCS likely plays a role in motor rehabilitation of spinal cord injured patients [1,3,5], also suggesting potential utility of this technology for treatment of other clinical conditions such as sensorimotor impairment caused by stroke [53,54] and for chronic pain [55].…”

“…This reasoning is supported by the recent evidence showing utility of transcutaneous spinal direct current stimulation in chronic pain care [55]. Irrespective of the intended application, the stimulation intensity of cervical tSCS should be configured just around the level to transsynaptically elicit motor potentials through selective activation of proprioceptive and cutaneous fibers, i.e., without direct motor fiber activation [3,4,12,60].…”

Effect of Transcutaneous Spinal Direct Current Stimulation in Patients with Painful Polyneuropathy and Influence of Possible Predictors of Efficacy including BDNF Polymorphism: A Randomized, Sham-Controlled Crossover Study

“…With the aim to treat neuropathic pain due to PNP, we have studied one of the more novel, non-invasive paradigms; transcutaneous spinal direct current stimulation (tsDCS). The technique involves a low-intensity spinal stimulation and has been demonstrated to induce polarity-dependent effects on different pathways of the spinal cord, e.g., [6][7][8]. One promising effect is that of anodal tsDCS on pain signaling; in a double-blind, sham-controlled study on healthy subjects we have been able to reproduce and expand on prior studies [6,7] finding parallel inhibitory effects of anodal tsDCS on subjective pain experience and pain signaling [9].…”

Trans-Spinal Direct Current Stimulation Targets Ca2+ Channels to Induce Persistent Motor Unit Responses

“…Non-invasive trans-spinal cord direct current stimulation (tsDCS) has the potential for promoting spinal motor function through its modulatory actions on sensory processing ( Aguilar et al, 2011 ), reflexes ( Winkler et al, 2010 ; Song et al, 2015 ; Mekhael et al, 2019 ), the motor cortex motor map ( Ahmed, 2013a ; Song et al, 2015 ), and enhancing spinal motor circuit function and motor output ( Ahmed, 2011 ; Jankowska, 2017 ; Song and Martin, 2017 ). tsDCS has also been used for treating different neurological diseases and injuries (e.g., Picelli et al, 2015 and Lamy et al, 2021 ) and for pain control ( Guidetti et al, 2021 ). The effects of tsDCS tend to be polarity dependent.…”