Objective: To determine which factors predict medication reduction for Parkinson’s disease (PD) patients after deep brain stimulation (DBS) of the bilateral subthalamic nucleus (STN).

Background: Reduction in dopaminergic medications can be one of the motivations for PD patients to pursue DBS. Levodopa responsiveness is widely accepted as the best predictor of good response to DBS. We evaluated whether the baseline impairment of motor subtypes and levodopa responsiveness of each subtype would predict degree of medication reduction.

Methods: This was a retrospective, single-center review of 21 PD patients who underwent bilateral STN DBS between April 2009 and April 2015. Prior to surgery, we measured total UPDRS III scores and subcategory scores (tremor, bradykinesia, rigidity and gait/axial) both off and on levodopa. Subscores were determined as follows: tremor (UPDRS III items 20,21), bradykinesia (19,23-26,31), rigidity (22b-22c), and gait/axial (18,22a,27-30) and were normalized to patients’ total UPDRS III score. Levodopa equivalent daily doses (LEDD) were calculated at baseline and six months after surgery. Statistical analysis using Spearman correlation and linear regression was carried out using GraphPad Prism.

Results: The mean age at time of surgery of the 21 subjects (16 male, 5 female) was 64 (range 37-76). Mean disease duration was 11.7 years. Mean reduction in LEDD six months after surgery was 17%. There was significant negative correlation (r=-0.50, p=0.01) between the off medication gait/axial score prior to DBS surgery and the percent LEDD reduction six months after surgery. In contrast, there was no correlation between preoperative levodopa responsiveness of the gait/axial subscore and LEDD reduction (r=0.019). There was also no correlation between LEDD reduction and levodopa responsiveness of total or other UPDRS III subscores nor their off medication counterparts.

Conclusions: PD patients with greater impairment in the gait/axial domains of the UPDRS III prior to bilateral STN DBS were less likely to reduce dopaminergic medications at 6 months after surgery. In contrast, the magnitude of preoperative levodopa response was not predictive of postoperative LEDD reduction. This suggests that the severity of baseline impairment in the gait/axial domain is a better predictor than levodopa responsiveness in a patient’s ability to reduce medications after bilateral STN DBS surgery.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/predicting-medication-reduction-in-parkinsons-disease-patients-after-deep-brain-stimulation/