• Hugo Ribeiro, Ricardo Bertol Sesterhenn, Souza Andressa de A Department of Clinical Research Center, Laboratory of Pain & Neuromodulation, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande, Ana Claudia de Souza, Monique Alves, Jessica Catarina Machado, Nathalia Bofill Burger, Torres Iraci Lucena da Silva ILDS Department of Clinical Research Center, Laboratory of Pain & Neuromodulation, Hospital de Clínicas de Porto Alegre, Universidade Federal, Stefani Luciana Cadore LC Department of Clinical Research Center, Laboratory of Pain & Neuromodulation, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio , Felipe Fregni, and Wolnei Caumo.
• Department of Clinical Research Center, Laboratory of Pain & Neuromodulation, Hospital de Clínicas de Porto Alegre, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, Brazil.
• Plos One. 2017 Jan 1; 12 (11): e0187013.

BackgroundAn imbalance in the excitatory/inhibitory systems in the pain networks may explain the persistent chronic pain after hallux valgus surgery. Thus, to contra-regulate this dysfunction, the use of transcranial direct current stimulation (tDCS) becomes attractive.ObjectiveWe tested the hypothesis that two preoperative active(a)-tDCS sessions compared with sham(s)-tDCS could improve the postoperative pain [as indexed by Visual Analogue Scale (VAS) at rest and during walking (primary outcomes)]. To assess their effect on the change in the Numerical Pain Scale (NPS0-10) during Conditioned Pain Modulation (CPM-task), disability related to pain (DRP) and analgesic consumption (secondary outcomes). Also, we assessed if the brain derived neurotrophic factor (BDNF) in the cerebral spinal fluid (CSF) after tDCS could predict the intervention's effect on the DRP.MethodsIt is a prospective, double blind, sham-controlled, randomized single center, 40 women (18-70 years-old) who had undergone hallux valgus surgery were randomized to receive two sessions (20 minutes each) of anodal a-tDCS or s-tDCS on the primary motor cortex at night and in the morning before the surgery. To assess the DRP was used the Brazilian Profile of Chronic Pain: Screen (B-PCP:S).ResultsA-tDCS group showed lower scores on VAS at rest and during walking (P<0.001). At rest, the difference between groups was 2.13cm (95%CI = 1.59 to 2.68) while during walking was 1.67cm (95%CI = 1.05 to 2.28). A-tDCS, when compared to s-tDCS reduced analgesic doses in 73.25% (P<0.001), produced a greater reduction in B-PCP:S (mean difference of 9.41 points, 95%CI = 0.63 to 18.21) and higher function of descending pain modulatory system (DPMS) during CPM-task.ConclusionA-tDCS improves postoperative pain, the DRP and the function of DPMS. Also, the CSF BDNF after a-tDCS predicted the improvement in the DRP. In overall, these findings suggest that a-tDCS effects may be mediated by top-down regulatory mechanisms associated with the inhibitory cortical control.Trial RegistrationClinicalTrials.gov NCT02360462.

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