Objective: We aimed to evaluate the effects of transcranial direct current stimulation (tDCS) on chronic pain in human T-lymphotropic virus type I-infected patients.
Materials and Methods: This is a sham-controlled randomized clinical trial. Twenty participants were randomized to receive active or sham anodal tDCS over the primary motor cortex (M1), with 2 mA, 25 cm2 electrodes, for 20 minutes on 5 consecutive days. Pain intensity was measured at baseline and after each day of treatment using a Visual Analog Scale. Associated factors such as pain components description, pressure pain threshold, and Timed Up and Go task were also assessed.
Results: Mild adverse events were reported by 100% of patients in the tDCS group and 90% in the sham group. Comparison of daily Visual Analog Scale pain scores from both groups demonstrated a significant effect for the factor Time (P<0.001), but not for Group (P=0.13) or Time×Group interaction (P=0.06). There were 8 (80%) responders (reduction of 50% or more in pain intensity) in the tDCS group and 3 (30%) in the sham group (P=0.03). Both groups demonstrated improvements for most associated factors evaluated. However, there was no difference in between-groups comparison analyses.
Conclusions: The analysis of the main outcomes in this study did not demonstrate a significant advantage of anodal tDCS applied to M1 in patients with human T-lymphotropic virus type I and chronic pain in comparison with sham tDCS, although secondary analysis suggests some superiority of active tDCS over sham. The large placebo effect observed in this study may explain the small differences between sham versus active tDCS.
*Bahian School of Medicine and Public Health
†Laboratory of Functional Electrostimulation, Federal University of Bahia, Salvador, Bahia
‡Department of Neuroscience and Behavior, Institute of Psychiatry, University of São Paulo, São Paulo, Brazil
§Laboratory of Neuromodulation, Spaulding Rehabilitation Hospital, Harvard Medical School, Boston, MA
G.S.G. was funded by FAPESB, Salvador, BA/Brazil (Fundação de Amparo a Pesquisa do Estado da Bahia) and M.E.M by CAPES, Brasília, DF/Brazil (Coordenação de Aperfeiçoamento Pessoal de Nível Superior). The authors declare no conflict of interest.
Reprints: Abrahão F. Baptista, PT, PhD, Laboratório de Eletroestimulação Funcional, Instituto de Ciências da Saúde, UFBA, Avenida Reitor Miguel Calmon, S/N, Vale do Canela, CEP: 40.110-902, Salvador, Bahia, Brasil (e-mail: firstname.lastname@example.org).
Received December 28, 2012
Received in revised form December 2, 2013
Accepted September 11, 2013