Objective: To determine whether the improvement in levodopa-induced dyskinesias after deep brain stimulation is primarily associated with reduction in dopaminergic medication or with a direct neuromodulatory effect.

Background: Levodopa-induced dyskinesias are a major complication in Parkinson’s disease. Deep brain stimulation of the subthalamic nucleus reduces dyskinesias and motor fluctuations, possibly through modulation of pathological basal ganglia network activity and abnormal beta oscillations. However, it remains unclear whether this improvement is primarily driven by postoperative reduction in dopaminergic medication or by direct neuromodulation of basal ganglia circuits.

Method: WeWe conducted a retrospective observational study including patients with Parkinson’s disease who underwent bilateral subthalamic nucleus deep brain stimulation. Motor complications were assessed using part IV of the Movement Disorder Society–Unified Parkinson’s Disease Rating Scale (MDS-UPDRS). Levodopa equivalent daily dose (LEDD) was calculated before surgery and at six months of follow-up. Pearson correlation and linear regression analyses were performed to evaluate the relationship between LEDD reduction and improvement in dyskinesias.

Results: Forty-five patients with Parkinson’s disease who underwent bilateral subthalamic nucleus deep brain stimulation were included. At six months, dyskinesia severity decreased in MDS-UPDRS part IV scores (Figure 1). Median levodopa equivalent daily dose was also reduced (Figure 2). However, regression analysis showed that reduction in dopaminergic medication explained only a minor proportion of the improvement in dyskinesia scores. Improvements were also observed in time with dyskinesia, functional impact of dyskinesia, motor fluctuations, and off-state dystonia (Figure 3).

Conclusion: Bilateral subthalamic nucleus deep brain stimulation significantly improves levodopa-induced dyskinesias in Parkinson’s disease. The limited contribution of medication reduction suggests that neuromodulation itself plays a substantial role in improving motor complications and supports the hypothesis that DBS directly modulates pathological basal ganglia network activity involved in dyskinesia generation.

Total MDS-UPDRS Part IV Score (Pre vs Post DBS)

Levodopa Equivalent Daily Dose (Pre vs Post DBS)

Specific MDS-UPDRS IV Items (Pre vs Post DBS)

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MDS Abstracts - https://www.mdsabstracts.org/abstract/deep-brain-stimulation-improves-levodopa-induced-dyskinesias-beyond-medication-reduction-in-parkinsons-disease/