Altered Functional Connectivity of the Subthalamic Nucleus in Parkinson's Disease: Focus on Candidates for Deep Brain Stimulation

Background: The hypothesis that the effectiveness of deep brain stimulation (DBS) in Parkinson's disease (PD) would be related to connectivity dysfunctions between the site of stimulation and other brain regions is growing. Objective: To investigate how the subthalamic nucleus (STN), the most frequently used DBS target for PD, is functionally linked to other brain regions in PD patients according to DBS eligibility. Methods: Clinical data and resting-state functional MRI were acquired from 60 PD patients and 60 age- and sex-matched healthy subjects within an ongoing longitudinal project. PD patients were divided into 19 patients eligible for DBS and 41 not candidates. Bilateral STN were selected as regions of interest and a seed-based functional MRI connectivity analysis was performed. Results: A decreased functional connectivity between STN and sensorimotor cortex in both PD patient groups compared to controls was found. Whereas an increased functional connectivity between STN and thalamus was found in PD patient groups relative to controls. Candidates for DBS showed a decreased functional connectivity between bilateral STN and bilateral sensorimotor areas relative to non-candidates. In patients eligible for DBS, a weaker STN functional connectivity with left supramarginal and angular gyri was related with a more severe rigidity and bradykinesia whereas a higher connectivity between STN and cerebellum/pons was related to poorer tremor score. Conclusion: Our results suggest that functional connectivity of STN varies among PD patients eligible or not for DBS. Future studies would confirm whether DBS modulates and restores functional connectivity between STN and sensorimotor areas in treated patients.