Modulatory effects of transcranial direct current stimulation on sensory gating in Fibromyalgia Syndrome.

Introduction: Several studies have demonstrated a reduced habituation to redundant somatosensory stimulation (sensory gating) in Fibromyalgia Syndrome. Furthermore, anodal transcranial direct current stimulation has been shown to modulate somatosensory processing. The aim of this study was to examine the modulatory effects of anodal transcranial direct current stimulation applied over the left primary somatosensory cortex on sensory gating in Fibromyalgia Syndrome.

Methods: Thirty-nine female Fibromyalgia Syndrome patients (43-71 years, mean 55.56 ± 7.85) participated in the study and were randomly assigned to the active transcranial direct current stimulation ( = 17) or non-electrical stimulation (sham;  = 22). Before and after transcranial direct current stimulation, somatosensory evoked potentials were recorded during a paired-pulse paradigm, consisting of two identical somatosensory stimuli (S1 and S2) applied in the right forefinger in rapid succession.

Results: Whereas P50 and N100 components were unaltered, a significant modulatory effect on the difference S1 - S2-which is commonly considered an index of sensory gating-in the Late Positive Complex component was found. This modulation manifested as an increased difference in the right hemisphere (contralateral to the stimulation) and a decreased difference in the left hemisphere (ipsilateral).

Discussion: Although this lateralizing pattern remains to be clarified, present results suggest brain excitability and somatosensory processing modulation by using anodal transcranial direct current stimulation in Fibromyalgia Syndrome patients.