Home›Neurology› STN-SNr co-stimulation adds no motor or gait benefit over STN-only in Parkinson's
STN-SNr co-stimulation adds no motor or gait benefit over STN-only in Parkinson'sTrial shows no added benefit for specific Parkinson's brain stimulation
Neurological sciences : official journal of the Italian Neurological Society and of the Italian Society of Clinical NeurophysiologyPublished October 24, 2026Study authors: Kong Lingjie, Li Pengxing, Bi Yuewei, Gong Le, Ren Yutong, Wang Yaning, Guo YiPubMed ↗DOI ↗Editorial oversight: Dr. Ji-eun Park, MD · Brain, Mind & Pain
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Key Takeaway
Interpret STN-SNr co-stimulation cautiously: no added motor or FoG benefit over STN-only in low-certainty data.
This meta-analysis pooled 10 studies including 109 unique evaluable participants with Parkinson's disease to assess whether subthalamic nucleus and substantia nigra pars reticulata (STN-SNr) co-stimulation adds benefit over STN-only stimulation. Outcomes were UPDRS-III and freezing of gait (FoG).
For the head-to-head comparison, there was no between-group difference in UPDRS-III (MD -0.10, 95% CI -1.01 to 0.81; 73 participants) and no additional FoG benefit (Hedges' g -0.23, 95% CI -1.04 to 0.59; 86 participants).
Comparisons against baseline did favor co-stimulation, with UPDRS-III MD -13.55 and FoG Hedges' g -0.60, but these baseline comparisons did not isolate an incremental SNr effect. Improvements versus stimulation-off or baseline therefore cannot establish added benefit from SNr co-stimulation.
The authors rated certainty as low for motor outcomes and very low for FoG outcomes. Additional limitations include lack of objective gait endpoints and lack of systematic adverse-event reporting; safety, tolerability, discontinuations, follow-up duration, and funding were not reported.
For practice, the synthesis indicates no clinically important difference in global motor outcomes and no consistent additional FoG benefit for STN-SNr co-stimulation compared with STN-only stimulation. The low and very low certainty of the underlying evidence limits how firmly this can guide programming decisions.
How this fits prior evidence
This meta-analysis extends the publication's Parkinson's disease coverage, which has recently focused on biomarkers and non-motor risk factors: neuromelanin-sensitive MRI differences in locus coeruleus signal and volume, GrimAge epigenetic age acceleration and dementia risk, dietary modulation of Parkinson's drug pharmacokinetics, photobiomodulation's inconsistent clinical results, and KRTCAP2 and depression polygenic risk scores. Those items addressed diagnostic and risk stratification questions, whereas this synthesis addresses a device-based treatment question, comparing STN-SNr co-stimulation with STN-only stimulation. Its null head-to-head findings for UPDRS-III and FoG contrast with the baseline improvements reported, reinforcing that uncontrolled comparisons cannot establish incremental benefit.
Living with Parkinson's disease means managing constant challenges with movement and balance. Doctors have explored different ways to use deep brain stimulation to help patients move more freely. One specific method involves stimulating two areas at once, called STN-SNr co-stimulation, to see if it works better than stimulating just one area.
A review of data from 109 patients found that this dual-stimulation approach did not provide any extra benefit over standard single-site stimulation. While both methods showed improvements compared to no stimulation at all, the extra step of adding the second site did not change the scores for overall motor function or for freezing of gait. Freezing of gait is a common and frustrating condition where a person's feet feel stuck to the floor.
It is important to note that the evidence for these specific outcomes is currently low to very low in certainty. Because the study compared both methods against a baseline of no stimulation, it could not prove if the second site provided any unique benefit. Patients should talk to their doctors to understand how these findings relate to their specific treatment plan.
What this means for you:
Adding a second stimulation site does not provide extra motor benefits for Parkinson's patients over standard methods.
Common questions
Does adding a second stimulation point help with Parkinson's symptoms?
The study found no significant difference between using two stimulation points (STN-SNr) and just one (STN-only). While both methods showed improvement compared to having no stimulation, the extra point did not provide additional benefits for motor scores or for freezing of gait.
What is freezing of gait?
Freezing of gait is a common symptom in Parkinson's disease where a person's feet feel stuck to the floor, making it hard to move. The study looked at 86 participants for this specific issue and found no extra benefit from the dual-stimulation method.
How certain are these results?
The evidence for motor outcomes is considered low certainty, and the evidence for freezing of gait is very low certainty. Because the study compared both methods to a baseline of no stimulation, it could not isolate if the second site offered any unique benefit.
BACKGROUND: Freezing of gait (FoG) and axial impairments often persist in Parkinson's disease despite optimized medication and subthalamic nucleus deep brain stimulation (STN-DBS). We systematically reviewed whether adding substantia nigra pars reticulata (SNr) stimulation improves motor and FoG outcomes.
METHODS: Following PRISMA 2020 and PROSPERO registration (CRD420261343479), six databases were searched through 1 May 2026. Primary outcomes compared STN-SNr co-stimulation with STN-only stimulation; stimulation-off or baseline comparisons were secondary. Two reviewers independently screened studies, extracted data, and assessed risk of bias. UPDRS-III and FoG were pooled as mean differences (MDs) and Hedges' g, respectively, accounting for paired data and within-study dependence. Certainty was assessed using GRADE.
RESULTS: Ten studies (nine randomized trials and one observational study) included 109 unique evaluable participants; two single-patient case reports were summarized narratively. UPDRS-III showed no between-group difference across seven studies (73 participants; MD - 0.10, 95% CI - 1.01 to 0.81; I² = 0%; low certainty). FoG showed no additional benefit across six studies (86 participants; Hedges' g - 0.23, 95% CI - 1.04 to 0.59; I²_total = 85.6%; very low certainty). Secondary baseline comparisons favored co-stimulation for UPDRS-III (MD - 13.55) and FoG (Hedges' g - 0.60), but did not isolate an incremental SNr effect.
CONCLUSIONS: Low-certainty evidence suggests no clinically important difference in global motor outcomes, while very-low-certainty evidence does not demonstrate a consistent additional FoG benefit. Improvements versus stimulation-off or baseline cannot establish an incremental SNr effect. Larger phenotype-stratified trials with objective gait endpoints and systematic adverse-event reporting are needed.
