Objective: Deep brain stimulation of the subthalamic nucleus (STN-DBS) is an established treatment in advanced Parkinson's disease (PD). However, the clinical outcome after STN-DBS is variable. The aim of this study was to explore the coherence of antagonistic muscles measured with electromyography (EMG) as novel biomarker of STN-DBS efficacy in PD.
Methods: EMG of bilateral wrist and upper arm antagonistic muscles of 21 PD patients was recorded during three standardized motor tasks. Patients were measured one day prior to DBS surgery (pre-DBS) and 6 months afterwards (post-DBS). Coherence analyses were performed on the antagonistic muscle pairs. Pearson correlations between intermuscular coherence and clinical performance were calculated.
Results: Intermuscular coherence during each of the different co-contraction tasks significantly correlated to UPDRS-III bradykinesia scores (p < 0.01). In other words, higher intermuscular coherence is associated with more severe PD symptoms. Moreover, coherence changes (pre-DBS - post-DBS coherence) correlated to clinical score changes after DBS (p < 0.01) and pre-DBS coherence correlated to this clinical score change as well (p < 0.01).
Conclusions: Higher pre-DBS coherence of antagonistic arm muscles is correlated to worsening of clinical PD state and higher intermuscular coherence predicts enhanced clinical improvement.
Significance: We propose that pre-DBS intermuscular coherence could be developed into a predictor of STN-DBS clinical outcome. It could aid patient selection and adaptive stimulation algorithms for DBS.
Keywords: Biomarker; DBS; EMG; Neurophysiology; PD; Parkinson’s disease; STN-DBS; aDBS.
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