Efficacy of Cerebellar Transcranial Direct Current Stimulation in Degenerative Ataxia. A Sham-Controlled Clinical and Quantitative Analysis

Neurodegenerative ataxias represent a heterogeneous group of disorders lacking effective treatments. This double-blind, sham-controlled study investigated the therapeutic potential of cerebellar transcranial Direct Current Stimulation (tDCS) in degenerative ataxia. Sixteen patients were randomized to receive either real or sham tDCS (10 sessions). Clinical evaluation, quantitative assessment of gait and upper limb function (through the “hand-to-mouth” task) and EEG were performed before and after treatment. Clinical outcome tools included the Modified International Cooperative Ataxia Rating Scale (MICARS), the Scale for the Assessment and Rating of Ataxia (SARA) and the Robertson dysarthria profile to rate ataxic and dysarthric symptoms. Quantitative kinematic assessment of upper and lower limb motor function was carried out by means of optical motion capture system. At last, resting state electroencephalography (EEG) enabled evaluation of cortical oscillatory changes. The primary outcomes were change from baseline in SARA and MICARS total scores; secondary outcomes included changes in Robertson dysarthria profile score, spatiotemporal gait and hand-to-mouth kinematics and cortical beta/gamma power on resting state EEG. Both real and sham tDCS groups showed improvements in ataxic and dysarthric symptoms, but real tDCS induced greater benefits in posture, gait (MICARS), and upper-limb coordination (SARA) subscales. Although statistical significance was not reached for main gait parameters, a higher proportion of patients receiving real tDCS demonstrated clinically meaningful gains in gait speed and step width. In contrast, hand-to-mouth parameters remained unchanged. EEG showed increases in central/parietal beta and low-gamma power after active but not sham stimulation, supporting neuromodulatory effects on the cerebello-thalamo-cortical network. Overall, these data support a therapeutic potential of cerebellar tDCS in improving symptoms in degenerative ataxia of different aetiology and contribute to elucidate the mechanisms underlying these effects. ClinicalTrials.gov registration: NCT07250321 (registered 2025-11-18).