No Effect of a Single Session of Transcranial Direct Current Stimulation on Experimentally Induced Pain in Patients with Chronic Low Back Pain – An Exploratory Study

Abstract

Transcranial direct current stimulation (tDCS) has been shown to modulate cortical excitability. A small number of studies suggested that tDCS modulates the response to experimental pain paradigms. No trials have been conducted to evaluate the response of patients already suffering from pain, to an additional experimental pain before and after tDCS. The present study investigated the effect of a single session of anodal, cathodal and sham stimulation (15 mins/1 mA) over the primary motor cortex on the perceived intensity of repeated noxious thermal and electrical stimuli and on elements of quantitative sensory testing (thermal pain and perception thresholds) applied to the right hand in 15 patients with chronic low back pain. The study was conducted in a double-blind sham-controlled and cross-over design. No significant alterations of pain ratings were found. Modalities of quantitative sensory testing remained equally unchanged. It is therefore hypothesized that a single 15 mins session of tDCS at 1 mA may not be sufficient to alter the perception of experimental pain and in patients with chronic pain. Further studies applying repetitive tDCS to patients with chronic pain are required to fully answer the question whether experimental pain perception may be influenced by tDCS over the motor cortex.

Building up Analgesia in Humans via the Endogenous μ-Opioid System by Combining Placebo and Active tDCS: A Preliminary Report

“…Overall, we found significant improvement of cold and heat pain tolerance following real tDCS, consistent with other studies [59]–[65]. The large variability in the QST values found in our study, especially for cold pain thresholds, are similar to other reported values [66], [67].…”

Combined neuromodulatory interventions in acute experimental pain: assessment of melatonin and non-invasive brain stimulation

“…The effect of a-tDCS on neurophysiological outcomes (such as evoked potentials) demonstrated in the present study, were also reproduced in the majority of trials after tDCS (Matsunaga et al, 2004 ; Csifcsak et al, 2009 ; Luedtke et al, 2012 ). Perhaps the psychophysical variables depend on a range of different pathways because evaluation of pain is a more complex process than mere somatosensory processing in evoked potentials.…”

“…Other explanations for these results, that challenge our hypothesis, are evidences of previous clinical studies, which demonstrated that the behavioral data did not indicate a pain-reducing effect of anodal stimulation (Grundmann et al, 2011 ; Jürgens et al, 2012 ; Luedtke et al, 2012 ). Interestingly, previous studies on experimental pain using the same stimulation paradigm also showed inconclusive effects of tDCS on psychophysical variables (Grundmann et al, 2011 ; Jürgens et al, 2012 ; Luedtke et al, 2012 ). These inconclusive effect of change on cortical nociceptive processing, as a response to heat pain was also reported in other recent study, which did not found neither cathodal nor anodal tDCS effect over the left M1 (1 mA, 15 min) (Ihle et al, 2014 ).…”

tDCS modulates cortical nociceptive processing but has little to no impact on pain perception

“…tDCS exerted subclinical antinociceptive effects, and these occurred in the predicted direction, but these were neither statistically significant nor within a clinically meaningful range. Interestingly, previous studies on experimental pain using the same stimulation paradigm also showed inconclusive effects on psychophysical variables [24,27,38], whereas neurophysiological outcomes (such as evoked potentials) were altered in the majority of trials after tDCS [5,14,40]. One potential explanation could be that psychophysical variables depend on a range of different pathways because evaluation of pain is a more complex process than mere somatosensory processing in evoked potentials.…”