Metabolic changes induced by theta burst stimulation of the cerebellum in dyskinetic Parkinson's disease patients.

BACKGROUND Cerebellar repetitive transcranial magnetic stimulation may be effective in reducing peak-dose levodopa induced dyskinesia in Parkinson's disease patients. It was proposed that the antidyskinetic effect could be due to modulation of cerebello-thalamo-cortical pathways. However the neural basis for these clinical effects have not yet been demonstrated. METHODS We investigated the effects of repeated sessions of cerebellar continuous theta burst stimulation in Parkinson's disease patients with levodopa induced dyskinesia on brain metabolism by means of positron emission tomography scan with fluorodeoxyglucose ((18)F-FDG) to characterize the specific cerebral network activated by cerebellar stimulation in these patients. RESULTS We found that five days of bilateral cerebellar continuous theta burst stimulation (cTBS) were effective in reducing levodopa induced dyskinesia. Clinical changes were paralleled by a reduction of (18)F-FDG metabolism in the cerebellum as revealed by positron emission tomography imaging. We found a global decrease in the metabolism of the bilateral cerebellar hemispheres, and a significant decrease in (18)F-FDG uptake in correspondence of bilateral dentate nucleus. CONCLUSIONS Our study demonstrates the antidyskinetic effect of cerebellar cTBS in Parkinson's disease patients with levodopa induced dyskinesia, is paralleled by modulation of the activity of the pathways connecting the cerebellar cortex with the deep cerebellar nuclei, confirming the hypothesis that the motor cerebellar circuit is involved in the generations of levodopa induced dyskinesia.