Abstract
PURPOSE: This meta-analysis aims to evaluate the existing evidence on the effects of tDCS on speech and voice alterations in patients with PD. SEARCH STRATEGIES: PubMed, LILACS, EMBASE, Cochrane Central Register of Controlled Trials, Science Direct, Web of Science, Scopus, and gray literature searches: Google Scholar and Open Grey. The search included the descriptors: "Parkinson Disease, Transcranial Direct Current Stimulation, Voice, Speech" combined with AND and OR. SELECTION CRITERIA: Patients with Parkinson's Disease, both sexes. Use of Transcranial Direct Current Stimulation (tDCS) to treat voice and speech parameters in patients with Parkinson's Disease. DATA ANALYSIS: A total of 1,345 articles were included, 14 articles in the systematic review and 6 articles in the meta-analysis. The risk of bias and level of evidence were assessed using REVIEW MANAGER 5.4.1 and GRADE software. RESULTS: The results showed an overall effect size of tDCS of Z=0.89 (P=0.37). Studies targeting the prefrontal cortex (PFC) showed a larger effect size of 1.38 (P=0.17), thus demonstrating a greater impact on speech and voice outcomes with the use of tDCS for PD. Three studies presented a low risk of bias, and three studies presented an unclear risk. CONCLUSION: Despite the small number of studies, the findings of this meta-analysis suggest the potential applicability of tDCS as an adjunctive tool in the treatment of voice and speech disorders in patients with PD.