Utilização da estimulação transcraniana por corrente contínua no tratamento da síndrome pós-laminectomia

Abstract

Transcranial Direct Current Stimulation (tDCS) is a non-invasive brain stimulation technique that modulates cortical excitability; it is safe and promising in a number of clinical diseases. Failed back surgery pain syndrome is defined as low back pain that sets in after the surgery. It is associated with several psychiatric comorbidities, in which depression and anxiety can stand out. Objective: To evaluate the improvement of pain in patients suffering from failed back surgery pain syndrome through tDCS. Material and Method: Twenty-four patients were randomized into three groups to receive active anodic or sham stimulation (1.5mA, 20 minutes during five consecutive days and 25cm2 electrode size) in two different areas, primary motor cortex and dorsolateral cortex pre-frontal, the hemisphere of stimulation being determined based on lateralization of the pain. Brief Pain Inventory and the Visual Analog Scale (VAS) were used to evaluate the pain. The degree of disease severity and the improvement of the condition of the individuals were evaluated through the Global Clinical Impression Scale. The quality of life assessment was performed through two instruments: the World Health Organization Brief Questionnaire on Quality of Life and the Short Form of Health Survey. Beck Anxiety and Depression Inventory was applied to evaluate the presence of psychiatric comorbidities. All these instruments were evaluated and correlated with the results. Individuals who used carbamazepine and / or metal objects in the brain region were excluded from the study. The distribution of normality of data and the homoscedasticity of these were verified from the Shapiro-Wilk and Levene test, respectively. Comparisons between the groups were performed using quantitative variables ANOVA-one way, ANOVA-Welch and Kruskal-Wallis and Man-Whitney. Fisher's test was used for the qualitative variables. Results: The pain intensity of the individuals has improved after the tDCS, and only those stimulated in M1 presented a statistically significant improvement after the five days of intervention. The improvement was maintained during four weeks after the end of the care protocol, but from the third week the mean value of pain intensity reported by the patients returned to resemble the individuals´ report in the other groups. Only in the group that received stimulus in M1 there was improvement of 2 to 5 points in the VAS. It is observed that there was a statistically significant difference in the way the individuals evaluate their quality of life as well as the improvement of the pain intensity by the VAS, and the quality of life evaluation among those who showed improvement was superior to those that have not improved. Conclusion: The use of tDCS was effective, resulting an improvement of the pain pattern in patients presenting failed back surgery pain syndrome, when applied in the primary motor cortex. It is a low-cost, easy-to-handle and high tolerability technique. Moreover, it is an important adjuvant therapeutic tool for better control of chronic pain, such as failed back surgery pain syndrome.