Objective: To compare the short-term effects of deep brain stimulation (DBS) in subthalamic nucleus (STN) and globus pallidus internus (GPi) on freezing of gait (FOG) in Parkinson’s disease (PD) and to identify potential predictors of improvement in FOG within the first year after surgery.

Background: STN DBS is proposed to improve FOG in PD by restoring dopaminergic transmission in basal ganglia while GPi DBS acts via modulation of its downstream connections to mesencephalic locomotor region. Though previous studies have independently shown improvement of FOG after both STN and GPi DBS, there are no studies with head-to-head comparison of the two targets.

Method: PD patients with levodopa-responsive FOG who underwent either STN or GPi DBS for the established indications between January 2022 and March 2024, were included in the study. FOG score¹ and scores in UPDRS I-IV, Montreal Cognitive Assessment (MoCA), Frontal Assessment Battery (FAB) and Beck’s depression inventory (BDI) were assessed pre-DBS and at 6 and 12-month visits. Improvement was estimated using the formula: pre-DBS Drug Off score- Post DBS score in Stimulation On, Drug Off/pre-DBS score in Drug Off.

Results: 22 patients in STN group and 20 patients in GPi group had levodopa responsive FOG before DBS.  Mean age at DBS was 60.23 ± 8.54 years in STN group and 64.05 ± 4.78 years in GPi group. Pre-op FOG severity in drug OFF was similar in both groups (p = 0.781). Mean improvement in FOG scores at 6 months and 1 year are shown in table 1. At 6 months post-DBS, 68.2% in STN group and 60% in GPi group had improvement in FOG (p = 0.58). Among the patients with improvement in FOG at 6 months, 66.7% in STN group and 80% in GPi group had sustained benefit at 1 year (p = 0.11). Univariate analysis showed no significant differences in age, sex, disease duration, disease phenotype, pre-DBS levodopa response, DBS target, MoCA, FAB, BDI scores between patients with and without improvement in FOG after DBS.

Conclusion: STN and GPi DBS improved FOG in a significant proportion of PD patients after DBS at 6 months without superiority of one target over another. The proportion of patients with sustained improvement in FOG at 1-year post-DBS was higher in GPi group but larger studies are required to confirm if a significant difference exists between the two targets on FOG.

Table 1

Figure 1

References: 1. Schaafsma JD, Balash Y, Gurevich T, Bartels AL, Hausdorff JM, Giladi N. Characterization of freezing of gait subtypes and the response of each to levodopa in Parkinson’s disease. Eur J Neurol. 2003 Jul;10(4):391-8.

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