Preditores do tratamento com estimulação transcraniana por corrente contínua em pacientes com dor neuropática: metanálise e meta-regressão de ensaios clínicos randomizados

Abstract

Background: In the literature, the analgesic effects of Transcranial Direct Current Stimulation (tDCS) in populations with chronic pain have been well reported. In Neuropathic Pain the results are still contrasting, with previous reviews showing small effect sizes and a considerable level of heterogeneity. The objective of the present study is to evaluate the effectiveness of treatment with tDCS in patients with chronic neuropathic pain on pain intensity, disability and psychosocial factors and to determine the predictors of this effectiveness when considering the influence exerted by sample characteristics, study design and parameters of the intervention. Methodology: A systematic search of the electronic databases of MEDLINE, CINAHL, EMBASE and CENTRAL conducted from June to July 2021 was carried out. Controlled clinical trials involving patients with chronic neuropathic pain who applied tDCS were included. The effect was measured using the standardized mean difference (SMD) with a 95% confidence interval, calculated with the values obtained after the intervention between the active and control groups. The level of evidence was assessed with GRADE (Grading of Recommendations Assessment, Development and Evolution) to explore potential moderating factors, we performed meta-regression analyses. Results: Based on 16 controlled clinical trials, mostly with low risk of bias, in a total of 432 individuals, tDCS was superior to simulation in improving pain (SMD = -0.41; 95% CI (-0.72 , -0.11); p=0.007). The meta-analysis did not show statistical significance in favor of active intervention to improve disability, as well as psychosocial outcomes. These results were based on a low level of evidence. Meta-regression analyzes showed that the duration of pain is negatively correlated with the effect size [diff SMD=0.003 (0.001; 0.012), p=0.02], R²= 1.00. The stimulation target was responsible for 86% of the variability, while the randomization description was responsible for 15% of the heterogeneity [diff SMD=0.385 (-1.749; -0.239), p=0.009], as was the study design [ diff SMD=0.380 (-0.033; 1.457), p=0.03]. Conclusion: tDCS may have beneficial effects on the outcome of pain intensity. The duration of symptoms, place of application of tDCS and methodological quality are moderators of the effects of tDCS. Future studies are needed to improve the quality of evidence.