To investigate the relationship between baseline patient characteristics and levodopa equivalent daily dose (LEDD) change following bilateral globus pallidus internus (GPi) deep brain stimulation (DBS) surgery in patients with Parkinson’s disease (PwP).

LEDD change after bilateral GPi DBS is not robustly characterized and existing data often include patients implanted before the advent of recent DBS technological advances such as directional leads.

Patient data, including LEDD, treatment side effects, age, sex, Montreal Cognitive Assessment (MoCA), Unified Parkinson’s Disease Rating Scale (UPDRS I, II, III-off, III-on), and cognitive diagnosis were retrospectively collected from a cohort of 45 PwP who underwent bilateral GPi DBS surgery between 2019 and 2023. Longitudinal LEDD data were retrospectively collected from three follow-up visits between 3 to 24 months postoperatively. Monthly rate of LEDD change was assessed for associations with baseline characteristics using random coefficient regression, Spearman correlation, and multiple regression analyses.

Postoperative monthly rate of LEDD change was -2.189 mg/month (95% CI [-8.711, 4.378]; p= 0.504), Baseline LEDD was negatively correlated with the predicted subject-specific rate of LEDD change (-0.33, 95% CI: [-0.58, -0.03]; p = 0.026), however this correlation was not significant on multiple regression analysis. The proportion of patients reporting treatment-related side effects decreased from 80% preoperatively to 31.1% between 12-14 months postoperatively, with no significant association between treatment side effects and the predicted rate of LEDD change.  No other baseline characteristic was significantly associated with the subject-specific predicted rate of LEDD change in either univariate analysis (p≥0.145) or multivariate analysis (p>0.275).

The change in LEDD from 3 to 24 months postoperatively in PwP undergoing bilateral GPI DBS was not significant. Patients with higher baseline LEDD may have a greater likelihood of reducing their LEDD postoperatively. No other baseline characteristic assessed had a significant predictive association with LEDD change.