Anodal Cerebellar Transcranial Direct Current Stimulation Reduces Motor and Cognitive Symptoms in Friedreich's Ataxia: A Randomized, Sham-Controlled Trial

BackgroundFriedreich Ataxia is the most common recessive ataxia with only one therapeutic drug approved solely in the United States. ObjectiveThe aim of this work was to investigate whether anodal cerebellar transcranial direct current stimulation (ctDCS) reduces ataxic and cognitive symptoms in individuals with Friedreich's ataxia (FRDA) and to assess the effects of ctDCS on the activity of the secondary somatosensory (SII) cortex. MethodsWe performed a single-blind, randomized, sham-controlled, crossover trial with anodal ctDCS (5 days/week for 1 week, 20 min/day, density current: 0.057 mA/cm(2)) in 24 patients with FRDA. Each patient underwent a clinical evaluation (Scale for the Assessment and Rating of Ataxia, composite cerebellar functional severity score, cerebellar cognitive affective syndrome scale) before and after anodal and sham ctDCS. Activity of the SII cortex contralateral to a tactile oddball stimulation of the right index finger was evaluated with brain functional magnetic resonance imaging at baseline and after anodal/sham ctDCS. ResultsAnodal ctDCS led to a significant improvement in the Scale for the Assessment and Rating of Ataxia (-6.5%) and in the cerebellar cognitive affective syndrome scale (+11%) compared with sham ctDCS. It also led to a significant reduction in functional magnetic resonance imaging signal at the SII cortex contralateral to tactile stimulation (-26%) compared with sham ctDCS. ConclusionsOne week of treatment with anodal ctDCS reduces motor and cognitive symptoms in individuals with FRDA, likely by restoring the neocortical inhibition normally exerted by cerebellar structures. This study provides class I evidence that ctDCS stimulation is effective and safe in FRDA. (c) 2023 International Parkinson and Movement Disorder Society.