Driving Cerebellar Theta Oscillations Interferes With Voluntary Neck Movements in Cervical Dystonia

Background: Cervical dystonia (CD) is a movement disorder with a complex pathophysiology, including cerebellar abnormalities. Transcranial alternating current stimulation (tACS), a noninvasive neuromodulation technique capable of entraining brain oscillations, can transiently modulate neuronal activity and enhance resonant rhythms. Objective: The aim of this study was to explore whether cerebellar tACS delivered at specific cerebellar-resonant frequencies modifies fast voluntary neck movements in patients with CD and whether botulinum toxin (BoNT) therapy influences tACS effects. Methods: Eighteen patients with CD, predominantly exhibiting the torticollis phenotype, were included. Fast voluntary neck movements were objectively assessed using motion analysis during two experimental sessions: (1) pre-BoNT and (2) 1 month after BoNT. Cerebellar tACS was applied at theta (θ), beta (β), and gamma (γ) frequencies, along with sham stimulation, while patients performed fast neck movements. Peak angular velocity and angular amplitude of both prodystonic and antidystonic movements were measured. Results: In the OFF-BoNT state, neck (antidystonic) movements' velocity and amplitude decreased with θ-tACS, particularly when stimulation was applied to the cerebellar hemisphere ipsilateral to the side of torticollis. BoNT ameliorated movement velocity and amplitude, but it did not change the detrimental effect of cerebellar θ oscillations on antidystonic movements. Conclusions: Driving cerebellar θ oscillations interferes with the execution of fast voluntary neck movements in CD, and BoNT therapy does not influence this effect. These findings support the view of dystonia as a network disorder in which the cerebellum plays a key role. © 2026 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.