Anodal Transcranial Direct Current Stimulation of the Motor Cortex Ameliorates Chronic Pain and Reduces Short Intracortical Inhibition

Department of Clinical Neurophysiology, Georg-August University, 37075 Göttingen, Germany.
Journal of pain and symptom management (Impact Factor: 2.8). 05/2010; 39(5):890-903. DOI: 10.1016/j.jpainsymman.2009.09.023
Source: PubMed

ABSTRACT Consecutive sessions of transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) may be a suitable therapy to treat chronic pain, as it can modulate neural activities in the stimulated and interconnected regions.
The present study investigated the analgesic effect of five consecutive days of anodal/sham tDCS using subjective (visual analog scale [VAS]) and objective (cortical excitability measured by transcranial magnetic stimulation [TMS]) measurements.
Patients with therapy-resistant chronic pain syndromes (trigeminal neuralgia, poststroke pain syndrome, back pain, fibromyalgia) participated. As this clinical trial was an exploratory study, statistical analyses implemented exploratory methods. Twelve patients, who underwent both anodal and sham tDCS, were analyzed using a crossover design. An additional nine patients had only anodal or sham stimulation. tDCS was applied over the hand area of the M1 for 20 minutes, at 1mA for five consecutive days, using a randomized, double-blind design. Pain was assessed daily using a VAS rating for one month before, during, and one month post-stimulation. M1 excitability was determined using paired-pulse TMS.
Anodal tDCS led to a greater improvement in VAS ratings than sham tDCS, evident even three to four weeks post-treatment. Decreased intracortical inhibition was demonstrated after anodal stimulation, indicating changes in cortico-cortical excitability. No patient experienced severe adverse effects; seven patients suffered from light headache after anodal and six after sham stimulation.
Results confirm that five daily sessions of tDCS over the hand area of the M1 can produce long-lasting pain relief in patients with chronic pain.

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    • "We also aimed to determine the beginning and duration of tDCS-induced alterations. Several studies demonstrated that the effects of tDCS were stronger in the first 5 min after stimulation and persisted for about 20 min (Antal et al., 2010; Keeser et al., 2011b). Therefore, we studied the effects of tDCS over EEG power spectral parameters, specifically in theta, alpha, beta, and gamma bands, through a statistical analysis of variance, to determine: "
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    ABSTRACT: Transcranial direct current stimulation (tDCS) delivers low electric currents to the brain through the scalp. Constant electric currents induce shifts in neuronal membrane excitability, resulting in secondary changes in cortical activity. Concomitant electroencephalography (EEG) monitoring during tDCS can provide valuable information on the tDCS mechanisms of action. This study examined the effects of anodal tDCS on spontaneous cortical activity in a resting brain to disclose possible modulation of spontaneous oscillatory brain activity. EEG activity was measured in ten healthy subjects during and after a session of anodal stimulation of the postero-parietal cortex to detect the tDCS-induced alterations. Changes in the theta, alpha, beta, and gamma power bands were investigated. Three main findings emerged: (1) an increase in theta band activity during the first minutes of stimulation; (2) an increase in alpha and beta power during and after stimulation; (3) a widespread activation in several brain regions.
    Frontiers in Human Neuroscience 08/2014; 8:601. DOI:10.3389/fnhum.2014.00601 · 2.99 Impact Factor
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    • "Non-invasive brain stimulation techniques, including transcranial direct current stimulation (tDCS), have received increasing attention as treatment options for SCI-related NP. tDCS involves the application of low current stimulation (often, 2 mA) via scalp electrodes to inject currents in the brain and modulate the level of cortical excitability (Nitsche et al., 2008). tDCS of the motor cortex (i.e., placement of the anode at or near M1or C3 site in the international 10-20 system) contralateral to the site of pain has demonstrated efficacy in a number of preliminary findings, and has been hypothesized to activate inhibitory systems that reduce nociceptive input into the thalamus (Mori et al., 2010; Fregni et al., 2006a; Fregni et al., 2006b; Boggio et al., 2009; Antal et al., 2010; Soler et al., 2010). However, whether tDCS operates via this or other possible mechanisms has not yet been confirmed. "
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    ABSTRACT: Objective Transcranial direct current stimulation (tDCS) has demonstrated efficacy for reducing neuropathic pain, but the respective mechanisms remain largely unknown. The current study tested the hypothesis that pain reduction with tDCS is associated with an increase in the peak frequency spectrum density in the theta-alpha range. Methods Twenty patients with spinal cord injury and bilateral neuropathic pain received single sessions of both sham and anodal tDCS (2 mA) over the left primary motor area (M1) for 20 minutes. Treatment order was randomly assigned. Pre- to post-procedure changes in pain intensity and peak frequency of electroencephalogram spectral analysis were compared between treatment conditions. Results The active treatment condition (anodal tDCS over M1) but not sham treatment resulted in significant decreases in pain intensity. In addition, consistent with the study hypothesis, peak theta-alpha frequency (PTAF) assessed from an electrode placed over the site of stimulation increased more from pre- to post-session among participants in the active tDCS condition, relative to those in the sham tDCS condition. Moreover, we found a significant association between a decrease in pain intensity and an increase in PTAF at the stimulation site. Conclusions The findings are consistent with the possibility that anodal tDCS over the left M1 may be effective, at least in part, because it results in an increase in M1 cortical excitability, perhaps due to a pain inhibitory effect of motor cortex stimulation that may influence the descending pain modulation system. Future research is needed to determine if there is a causal association between increased left anterior activity and pain reduction. Significance The results provide new findings regarding the effects of tDCS on neuropathic pain and brain oscillation changes.
    Clinical Neurophysiology 06/2014; 126(2). DOI:10.1016/j.clinph.2014.05.034 · 3.10 Impact Factor
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    • "One method of therapy has been realized in the form of non-invasive cortical stimulation (NICS) with the primary motor cortex (M1) being the most effective target for the modulation of both experimental and chronic pain [3], [4]. Particular efficacy for NICS has been found in patients with musculoskeletal pain [5]–[8]. However a lack of understanding of the underlying physiological mechanisms has limited these techniques progress in clinical applications. "
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    ABSTRACT: The primary motor cortex (M1) is an effective target of non-invasive cortical stimulation (NICS) for pain threshold modulation. It has been suggested that the initial level of cortical excitability of M1 plays a key role in the plastic effects of NICS. Here we investigate whether transcranial direct current stimulation (tDCS) primed 1 Hz repetitive transcranial magnetic stimulation (rTMS) modulates experimental pressure pain thresholds and if this is related to observed alterations in cortical excitability. 15 healthy, male participants received 10 min 1 mA anodal, cathodal and sham tDCS to the left M1 before 15 min 1 Hz rTMS in separate sessions over a period of 3 weeks. Motor cortical excitability was recorded at baseline, post-tDCS priming and post-rTMS through recording motor evoked potentials (MEPs) from right FDI muscle. Pressure pain thresholds were determined by quantitative sensory testing (QST) through a computerized algometer, on the palmar thenar of the right hand pre- and post-stimulation. Cathodal tDCS-primed 1 Hz-rTMS was found to reverse the expected suppressive effect of 1 Hz rTMS on cortical excitability; leading to an overall increase in activity (p<0.001) with a parallel increase in pressure pain thresholds (p<0.01). In contrast, anodal tDCS-primed 1 Hz-rTMS resulted in a corresponding decrease in cortical excitability (p<0.05), with no significant effect on pressure pain. This study demonstrates that priming the M1 before stimulation of 1 Hz-rTMS modulates experimental pressure pain thresholds in a safe and controlled manner, producing a form of analgesia.
    PLoS ONE 03/2014; 9(3):e92540. DOI:10.1371/journal.pone.0092540 · 3.23 Impact Factor
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