Effects of Cerebellar tACS-iTBS in Ataxia

Ataxia comprises a heterogeneous group of acquired or inherited disorders primarily involving cerebellar dysfunction, leading to impaired coordination and motor learning. Traditional treatments, including medication and physical therapy, often provide limited symptomatic improvement. Non-invasive brain stimulation (NIBS) techniques have emerged as promising tools for modulating cerebellar activity and enhancing motor function. Transcranial magnetic stimulation (TMS) can influence cortical excitability and plasticity, and studies have shown that high-frequency cerebellar rTMS can improve motor performance in spinocerebellar ataxia. Intermittent theta burst stimulation (iTBS), a patterned form of TMS, has demonstrated benefits in other movement disorders, suggesting potential applicability to ataxia. Transcranial direct current stimulation (tDCS), which modulates neuronal excitability via weak electrical currents, has shown improvements in static and dynamic balance in degenerative cerebellar ataxia. Transcranial alternating current stimulation (tACS) modulates neural oscillations and early studies indicate possible benefits for ataxia symptoms. Recent work has explored combining NIBS modalities to enhance neuromodulatory effects. In preliminary experiments, combined cerebellar tACS and iTBS increased MEP amplitudes more than iTBS alone, with effects lasting up to 30 minutes. These synergistic effects may translate into improved motor performance, coordination, and balance. The present study aims to investigate whether combining real or sham tACS with iTBS produces greater benefits than exergaming biofeedback alone in individuals with ataxia. A cross-over design will be used so that each participant serves as their own control. The primary outcomes will include motor coordination, balance, and cerebello-cortical plasticity. The rationale is that tACS may optimize oscillatory activity while iTBS enhances excitability, thereby jointly promoting neuroplasticity in cerebellar networks. The study will recruit individuals diagnosed with ataxia and assess the therapeutic potential of combined NIBS interventions.

Inclusion criteria

• Confirmed diagnosis of ataxia based on clinical assessment and/or neuroimaging findings.
• Stable medication regimen for at least four weeks prior to the study.
• Sufficient cognitive ability to understand and comply with study instructions.

Exclusion criteria

• History of seizures.
• Severe general impairment or concomitant diseases.
• Intracranial metal implants.
• Cardiac pacemaker.
• Pregnancy status.