Basal ganglia neurophysiological markers of non-motor symptoms in Parkinson's disease: A systematic review.

BackgroundDeep brain stimulation (DBS) for Parkinson's disease (PD) primarily improves motor symptoms but leaves non-motor symptoms (NMS) largely unattended. Neurophysiological markers associated with specific symptoms could improve DBS programming. We systematically reviewed the evidence linking basal ganglia local field potentials (LFP) to NMS in PD.MethodsThe literature search (Medline, Embase, Scopus, and Web of Science) on August 20, 2024 yielded 1066 records. Studies were included if they focused on patients with idiopathic PD treated with DBS of the subthalamic nucleus (STN) or globus pallidus interna (GPi) and reported on the relationship between LFP data and NMS. The study risk of bias was evaluated using the Prediction Model Risk of Bias Assessment Tool (PROBAST). A narrative synthesis of results was provided.ResultsTwenty-one studies were included, focusing on impulse control disorders (n = 8), sleep-wake disorders (n = 5), depressive symptoms (n = 4), cognitive dysfunction (n = 3), hypomania (n = 1) and lower urinary tract symptoms (n = 1). Seven studies had a high risk of bias. Theta and alpha power in the STN were frequently associated with neuropsychiatric symptoms and cognitive function. Beta power in the STN and GPi was linked to sleep-wake disorders and urinary dysfunction.ConclusionsOverall, evidence on basal ganglia physiomarkers of NMS in PD remains limited. Further research is essential to develop patient-specific stimulation paradigms targeting NMS, which could significantly improve the quality of life of individuals with PD.OtherThis systematic review was registered with the International Prospective Register of Systematic Reviews (CRD42024495284). There was no specific funding for this study.