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Published on: December 13, 2017
Phase-locked transcranial electrical brain stimulation for tremor suppression in dystonic tremor syndromes
Freek Nieuwhof1, Ivan Toni1, Arthur W G Buijink2
1Centre for Cognitive Neuroimaging, Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, the Netherlands.
Objective:
To establish the causal role of the cerebellum and motor cortex in dystonic tremor syndromes, and explore the therapeutic efficacy of phase-locked transcranial alternating current stimulation (TACS).
Methods:
We applied phase-locked TACS over the ipsilateral cerebellum (N = 14) and contralateral motor cortex (N = 17) in dystonic tremor syndrome patients, while patients assumed a tremor-evoking posture. We measured tremor power using accelerometery during 30 s stimulation periods at 10 different phase-lags (36-degrees increments) between tremor and TACS for each target. Post-hoc, TACS-effects were related to a key clinical feature: the jerkiness (regularity) of tremor.
Results:
Cerebellar TACS modulated tremor amplitude in a phase-dependent manner, such that tremor amplitude was suppressed or enhanced at opposite sides of the phase-cycle. This effect was specific for patients with non-jerky (sinusoidal) tremor (n = 10), but absent in patients with jerky (irregular) tremor (n = 4). Phase-locked stimulation over the motor cortex did not modulate tremor amplitude.
Conclusions:
This study indicates that the cerebellum plays a causal role in the generation of (non-jerky) dystonic tremor syndrome. Our findings suggest pathophysiologic heterogeneity between patients with dystonic tremor syndrome, which mirrors clinical variability.
Significance:
We show tremor phenotype dependent involvement of the cerebellum in dystonic tremor syndrome. Tremor phenotype may thus guide optimal intervention targets.
