Objective: To explore the mechanism by which levodopa modulates the functional connectivity of the subregions of the thalamus and  which subregional connectivity changes are associated with improved motor symptoms.

Background: Levodopa is the most effective medication for the management of Parkinson’s disease (PD) clinical motor symptoms. It can reverse these clinical manifestations with varying degrees of improvement by modulating the function of circuits, but its detailed mechanisms are still not fully understood. The thalamus is an important hub for these circuits and different subregions of the thalamus have different roles in the motor circuit of PD.

Method: Thirty-six PD patients and thirty-seven healthy controls were scanned using resting-state functional MRI. Functional connectivity of the subregions of the thalamus was measured and compared before and after levodopa administration in patients with PD. The correlation between improvements in motor symptoms and changes in the subregions of the thalamus connectivity was examined.

Results: Compared with PD “off”state, PD“on”state  exhibited decreased connectivity with the right pre-motor thalamus, right lateral pre-frontal thalamus and the right postcentral gyrus. Compared with the healthy controls, PD patients including “off”state and “on”state exhibited decreased connectivity with the left cerebellum and the right pre-motor thalamus. Furthermore , improvements in tremor were positively correlated with decreased connectivity of the right pre-motor thalamus, right lateral pre-frontal thalamus and the postcentral gyrus.

Conclusion: Levodopa improves tremor symptom by reducing the connectivity between the right pre-motor thalamus, right lateral pre-frontal thalamus and the postcentral gyrus.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/levodopa-improves-tremor-symptom-by-reducing-the-connectivity-between-the-thalamic-subregions-and-postcentral-gyrus-in-patients-with-parkinsons-disease/