Objective: This study assesses the effect of STN-DBS in early PD patients on axial symptoms compared to BMT.

Background: In well-selected candidates, STN-DBS offers symptom relief in PD even in earlier stages of disease (1). Whereas the effect on tremor, rigidity and bradykinesia is obvious, the outcome on axial symptoms is less clear. If and to which extend axial symptoms improve after STN-DBS remains under debate.

Methods: 124 patients with STN-DBS and best medical treatment (BMT) were compared to 127 patients with BMT alone (ITT analysis set). Statistical analyses compared changes of axial symptoms from baseline to 24 months. The postural instability/gait difficulty (PIGD)-subscore derived from the UPDRS III (items 27-30), the PDQ-39 ‘gait subscore’ (items 4-8), the axial subscore of the UPDRS II (items13-15, “worst”), the UPDRS II item 14 (freezing of gait, “worst”, whereas a freezer was defined as a value of ≥ 1) as well as gait assessments (CAPSIT-PD) were compared. The latter included number of steps and freezing episodes and time needed to complete the walking test. The gait assessments and UPDRS III were performed in the medication-on and -off state. For subscores, mixed model statistical analyses, and for individual questions the proportional odds statistical analyses were performed.

Results: The UPDRS III PIGD subscore (On-stim, Off-med) from baseline to 24 months improved significantly for the DBS-group compared to BMT. The PDQ-39-subscore improved for the DBS-group compared to BMT at 24 months. The subscore of UPDRS II worsened from baseline to 24 months for the BMT group but was statistically significantly improved for the DBS group.  According to UPDRS II item 14, about 50% of the patients of each group suffered from FOG at baseline, which was reduced in the DBS-group to 34% but not in the BMT group after 24months. In the walking test (On-stim, Off-med), the difference in mean change at 24 months between treatment groups was statistically significant for the DBS group as compared with the BMT group for the number of steps, the amount of freezing episodes (statistical trend, p=0.0612) but not for the walking time.

Conclusions: Within the first two years of early STN-DBS treatment in PD patients, axial symptoms such as gait, freezing of gait and postural instability improve compared to BMT alone.

References: (1) Schüpbach WM et al., N Engl J Med. 2013 Feb 14;368(7):610-22.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-effect-of-early-stn-dbs-in-pd-patients-on-axial-symptoms-a-2-year-randomized-controlled-trial-earlystim-gait-analysis/