Objective: To compare the effect of bilateral sub-thalamic nucleus (STN)  deep brain stimulation (DBS) and Globus pallidus interna (GPI) DBS on gait and postural stability in Parkinson’s disease (PD).

Background: DBS is an effective surgical therapy for motor complications in PD and tremor, with main targets being the STN and GPI. A comparative evaluation of the effect of these targets on gait and balance is limited.

Method: A systematic review of parallel randomized controlled studies comparing bilateral DBS of the STN and GPI in PD was conducted that were published before 2^nd October 2021.Primary outcome: change in severity of gait and postural stability using validated scales. Secondary outcomes: change in functional mobility & occurrence of adverse events. A risk of bias assessment and GRADE methodology was used for critical appraisal of studies. Four studies were examined in a random effects model meta-analysis. We calculated the standardized mean difference (SMD) and corresponding 95% confidence intervals (CI) for the outcomes. A planned subgroup analysis (follow up ≤ 12months vs. > 12months) was also conducted.

Results: We found a clinically meaningful difference in favour of STN DBS for the change in severity of gait and postural stability (UPDRS gait sub-scores) in stimulation on & medication off-state at 12-months follow-up (SMD: -0.63, CI: -0.87 to -0.38, n=270, low certainty of evidence], but not in stimulation on & medication on-state. (SMD: -0.06, CI: -0.38 to 0.27, n=145, low certainty of evidence).When comparing STN DBS to GPI DBS for severity of gait and postural instability in stimulation on & medication off-state with longer follow-up (12 – 24 months) using UPDRS gait sub-scores, there was little or no difference between targets (SMD: 0.37, CI: -0.87 to 0.13, , n=418, very low certainty of evidence).Pooled analysis could not be done for adverse effects and functional mobility due to significant differences in reporting.

Conclusion: Our results suggest better outcomes for STN DBS over GPI DBS in terms of severity of gait and postural instability at 12-months of follow up. This difference was not seen for longer follow periods, which could be due to worsening axial features with disease progression with both targets. There is need for future trials to address this important question that should also include patient reported outcomes.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-systematic-review-to-compare-the-effect-of-bilateral-deep-brain-stimulation-stn-versus-gpi-on-gait-and-balance-in-parkinsons-disease/