Article

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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    ABSTRACT: Previous studies suggest that transcranial direct current stimulation (tDCS) over the primary motor cortex (M1) reduces chronic pain levels. In this randomized controlled trial, we investigated the effects of 5 consecutive 20-minute sessions of 2-mA anodal tDCS directed to the M1 in 48 patients (45 females) with fibromyalgia. Changes in pain, stress, daily functioning, psychiatric symptoms, and health-related quality of life were measured. Pain and stress were measured 30 days before treatment, at each treatment, and 30 days after treatment by using short message service on mobile phones. Patients were randomized to the active or sham tDCS group by receiving individual treatment codes associated either with the sham or active tDCS in the stimulator. Adverse effects were registered using a standardized form. A small but significant improvement in pain was observed under the active tDCS condition but not under the sham condition. Fibromyalgia-related daily functioning improved in the active tDCS group compared with the sham group. The stimulation was well tolerated by the patients, and no significant difference in the adverse effects between the groups was observed. The results suggest that tDCS has the potential to induce statistically significant pain relief in patients with fibromyalgia, with no serious adverse effects, but small effect sizes indicate that the results are unlikely to reflect clinically important changes.
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    • "Further studies with additional H-reflex-measurements after cathodal stimulation and larger sample sizes are needed to explore the relationship between clinical effects and neurophysiology more deeply and to corroborate our findings. Future studies should also explore whether the clinical effects of anodal tsDCS can be enhanced, for example, by repeated stimulation [28] [33] similar to repetitive anodal tDCS for the treatment of chronic pain [14] [16]. Furthermore, the pathophysiology of RLS might influence the response to spinal stimulation. "
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