The role of transcranial direct current stimulaton on ataxia: a scoping review

Cerebellar ataxias are a diverse group of hereditary and acquired disorders that impair balance, gait, posture and ocular movements. With limited treatment options, particularly in hereditary forms, neuromodulation has emerged as a promising therapeutic approach particularly the transcranial direct current stimulation (tDCS). This scoping review aims to discuss the role of tDCS as a potential therapy in reducing ataxia symptoms in both hereditary and acquired forms. A total of 787 studies were found after searching Pubmed, EMBASE, and Cochrane. After removing 273 duplicates, 514 studies remained for title and abstract screening. Of these, 387 studies were excluded, leaving 127 studies for full-text assessment. Following retrieval of full text, 26 was assessed for eligibility. This review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) guidelines. A comprehensive literature search was performed using PubMed, EMBASE, and Cochrane databases. Two independent reviewers screened studies through title/abstract and full-text review, with disagreements resolved by discussion or adjudication by two additional reviewers when necessary. We included 18 studies for the final analysis. Most studies reviewed showed that tDCS is a potential option for the treatment of ataxia, however, differences among participants, neuromodulation techniques, or trial protocols may have led to differences in the clinical outcomes. Our review highlights that the vast majority of the randomized controlled studies of tDCS in neurodegenerative ataxias have demonstrated clinical beneficial effect. There are preliminary observations that tDCS in combination therapy with rehabilitation or exercise may provide greater or more functional improvements. Future multicenter studies with long term follow up of individual disease groups, supported by clinical, imaging and biological marker measurements will help address the current limitations.