Objective: To review various electrophysiology markers of levodopa induced dyskinesia (LID) investigated in current studies and the pathophysiology of LID in the context of abnormal basal ganglia-thalamocortical pathways.

Background: The prevalence of PD in the population above 60 is about 1%, affecting one to two per 1000 of the population with total economic cost estimated at $51.9 billion. Discovery of levodopa and carbidopa therapy revolutionized treatment of PD in the 1970s. However, levodopa therapy is limited by LID. LID have three types of abnormal movements, off period dystonia, peak dose dyskinesia, and diphasic dyskinesia. An important step in the management of LID is recognition of the clinical pattern. However, there is no objective tool to identify or assess dyskinesia. Therefore, brain electrophysiology has been proposed as one potential marker of LID.

Method: This is a systematic review to identify potential electrophysiology marker of LID from the available literature. This review will summarize electrophysiological findings of LID which inform the underlying basal ganglia-thalamocortical pathophysiology We reviewed systematic reviews and primary studies of both human subjects and animal models studies with either electroencephalogram, electrocorticography, and/or basal ganglia local field potentials (LFPs).

Results: Nigrostriatal dopaminergic degeneration and pulsatile dopaminergic stimulation from levodopa pathophysiology results in altered dopamine receptor mediated signaling and abnormal corticostriatal synaptic plasticity. This results in abnormal basal ganglia-thalamocortical loop which may manifest in altered electrophysiological findings. Key findings include that off period dystonia is associated with alpha oscillations in the motor cortex and elevated coupling between beta phase and high frequency oscillations. Hyperkinetic dyskinesia (peak dose and diphasic dyskinesia) is associated with gamma oscillation and lower beta phase coherence.

Conclusion: Candidate electrophysiological markers include prominent alpha oscillations, interhemispheric alpha coherence, or gamma oscillations. Electrophysiology markers of LID could one day be used in diagnosis and monitoring. In addition, these biomarkers could contribute to the advancement of closed loop deep brain stimulation.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/electrophysiology-marker-of-levodopa-induced-dyskinesia-in-parkinson-disease/