Essential tremor Searching for dissonance in an orchestrated sensorimotor network

In this thesis we studied the brain networks underlying essential tremor and we compared these to networks associated with tremor in Parkinson's disease and cortical myoclonic tremor. By combining EEG and EMG, we demonstrated that in essential tremor the motor cortex has no active role in contrast to cortical myoclonic tremor which is known for its cortical origin of the tremor. Furthermore, our fMRI study suggests involvement of the olive-cerebellar circuit in tremor generation. Lastly, by means of a multimodal approach in which a wrist manipulator was applied in the MRI environment, we were able to split incoming and outgoing signals of the voluntary sensorimotor network. Unlike in Parkinson’s disease, the sensorimotor network was not affected in essential tremor. Altogether, the olivo-cerebellar circuit seems to be pivotal for tremor generation, while sustaining of tremor depends on the entire olivo-cerebello-thalamocortical network without affecting the voluntary sensorimotor network. With help of advanced neurophysiological and imaging techniques, we have contributed to the understanding of the pathophysiology of essential tremor.