NON-INVASIVE BRAIN STIMULATION TECHNIQUES FOR THE TREATMENT OF FIBROMYALGIA: A SYSTEMATIC REVIEW AND META-ANALYSIS

BACKGROUND: FM is a complex chronic nervous system syndrome, in which pain represents the main symptom complained by patients. This condition is linked to a reduction in quality of life, involving multiple activities and domains, from the cognitive to the physical function. Non-invasive brain stimulation techniques (NIBS) are being increasingly used in rehabilitation as means of neurostimulation and neuromodulation. They include different techniques: transcranial magnetic stimulation (TMS), transcranial direct current stimulation (tDCS), transcranial random noise stimulation (tRNS), transcranial alternating current stimulation (tACS) and reduced impedance non-invasive cortical electrostimulation (RINCE). OBJECTIVE: to analyze the effectiveness of non-invasive brain stimulation techniques for the treatment of fibromyalgia. DESIGN: A systematic review with meta-analysis DATA SOURCES: We searched through the PubMed, Scopus, Web of Science, and Clinical Trials databases for relevant articles. Only randomized controlled trials and cross-over studies have been included, also investigating through the bibliography of the systematic reviews found in literature. REVIEW METHODS: Articles were entirely read if they adhered to the inclusion criteria or if there was any uncertainty. A quality assessment of the included studies has been conducted with the application of the Jadad scale. RESULTS: Positive therapeutic effect of rTMS on pain and quality of life (FIQ) was assessed, while tDCS resulted associated to a small effect on pain only. Adjustment for publication bias resulted in reduction of effect size and consequent cancellation of treatment effect. Application of rTMS maintains better FIQ scores after adjustment, particularly when left M1 in stimulated (Hedges’ g = 0.74), compared to left DLPFC (Hedges’ g = 0.22). Combined effect size after all subgroup analyzes demonstrates wide variability range and no statistical significancy, denoting inconsistency results. CONCLUSIONS: No effect of rTMS or tDCS was found on pain when publication bias adjustment is conducted. FIQ scores demonstrate an improvement only after rTMS intervention, considering stimulation of left M1 as better performative. Inconsistency of data have been largely demonstrated.