Transcranial direct current stimulation does neither modulate results of a quantitative sensory testing protocol nor ratings of suprathreshold heat stimuli in healthy volunteers

Background Transcranial direct current stimulation (tDCS) has been shown to effectively modulate cortical excitability. Several studies have suggested clinical efficacy in pain syndromes such as central neuropathic pain or fibromyalgia. However, little is known regarding tDCS effects on nociception in healthy volunteers. Methods In the present study, we examined the effects of anodal, cathodal and sham stimulation of the left primary motor cortex in 17 healthy volunteers on modalities of a comprehensive quantitative sensory testing protocol (including thermal and mechanoreceptive detection and pain thresholds) and on a repetitive heat pain paradigm mimicking clinical pain. The study was conducted in a single-blind crossover fashion. tDCS was applied at 1?mA for 15?min. Results We could not detect any relevant modulation of somatosensory and pain variables in quantitative sensory testing. In addition, no significant alteration of enhanced pain ratings to repetitive noxious heat stimuli (heat hyperalgesia) was found. Conclusion As pain processing in chronic pain patients might differ, tDCS could exert its antinociceptive effects depending on the activation level of the nociceptive system.