Deep Brain Stimulation for Visuomotor Function in Parkinson's Disease
Overview
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This observational clinical trial investigates how deep brain stimulation (DBS) of the subthalamic nucleus (STN) affects visuomotor function in patients with Parkinson's disease. Specifically, the study focuses on vergence — the coordinated movement of both eyes to maintain binocular alignment when focusing on objects at different distances. Vergence deficits are a common but understudied non-motor symptom in PD that affects reading, depth perception, and daily activities.
...Deep Brain Stimulation for Visuomotor Function in Parkinson's Disease
Overview
Mermaid diagram (expand to render)
This observational clinical trial investigates how deep brain stimulation (DBS) of the subthalamic nucleus (STN) affects visuomotor function in patients with Parkinson's disease. Specifically, the study focuses on vergence — the coordinated movement of both eyes to maintain binocular alignment when focusing on objects at different distances. Vergence deficits are a common but understudied non-motor symptom in PD that affects reading, depth perception, and daily activities.
The study aims to characterize how STN DBS influences vergence metrics and identify optimal stimulation locations and parameters that can preserve motor symptom control while improving binocular coordination.
Trial Details
| Parameter | Value |
|-----------|-------|
| NCT Number | NCT05400499 |
| Status | Recruiting |
| Phase | Not Applicable (Observational) |
| Sponsor | VA Office of Research and Development |
| Study Type | Observational (Cohort) |
| Enrollment | 40 participants (estimated) |
| Start Date | October 4, 2022 |
| Primary Completion | June 30, 2026 |
| Completion Date | July 1, 2026 |
| Location | Louis Stokes VA Medical Center, Cleveland, OH |
Scientific Rationale
Why Study Vergence in PD?
Parkinson's disease affects not only motor function but also oculomotor control. Patients with PD commonly experience:
Reduced vergence accuracy — difficulty aligning both eyes on near or far targets
Increased vergence latency — delayed onset of eye alignment adjustments
Reduced peak vergence velocity — slower eye movements for focusing
Binocular incongruency — misalignment between eyes during convergenceThese deficits impact:
- Reading ability and speed
- Depth perception (affecting driving, walking on stairs)
- Fine visual tasks
- Quality of life
Subthalamic Nucleus and Oculomotor Control
The [subthalamic nucleus](/cell-types/subthalamic-nucleus-neurons) (STN) is a key component of the basal ganglia-thalamocortical circuit and a primary target for DBS in Parkinson's disease. While STN DBS is highly effective for motor symptoms (rigidity, bradykinesia, tremor), its effects on oculomotor function are less understood.
The STN has connections to:
- Premotor cortex — movement planning including eye movements
- Superior colliculus — orienting responses and eye movements
- Brainstem nuclei — controlling eye muscle activation
- Thalamus — sensory integration for motor commands
This study investigates how modulating STN activity through DBS affects these interconnected systems involved in vergence control.
Patient-Specific Modeling Approach
A key innovation of this study is integrating patient-specific DBS models with high-resolution eye-tracking:
Pre-operative MRI — anatomical mapping
Post-operative CT/MRI — electrode localization
Patient-specific models — computational models of stimulation fields
High-resolution eye-tracking — precise vergence measurementThis approach allows researchers to correlate specific stimulation locations with vergence outcomes, potentially enabling optimized targeting for both motor and oculomotor symptoms.
Study Design
Participant Population
The study enrolls veterans with Parkinson's disease who have undergone bilateral STN DBS implantation:
Inclusion Criteria
- Parkinson's disease with bilateral STN DBS
- Pre-operative MR images available
- Post-operative MRI or CT scans available
- Hoehn and Yahr stage 2-4 when off medication
- Stable antiparkinsonian medication regimen
- Stable DBS parameter settings
Exclusion Criteria
- Previous surgical therapy for Parkinson's disease (other than DBS)
- [Dementia](/diseases/dementia)
- Clinically significant untreated depression or anxiety
- Clinical features suggestive of atypical parkinsonism
Outcome Measures
Primary Outcome: Eye Alignment (Vergence)
The primary outcome measure is dynamic eye alignment measured using non-invasive high-resolution video oculography:
| Metric | Description |
|--------|-------------|
| Vergence ratio | Ratio of actual versus desired vergence movements |
| Vergence latency | Delay from target change to vergence onset |
| Peak vergence velocity | Maximum speed of vergence eye movements |
| Binocular congruency | Agreement between left and right eye positions |
Assessment Protocol
Participants perform vergence tasks while their eye movements are recorded:
- Duration: 1 hour testing session
- Paradigms: Step and ramp stimuli at various distances
- Measurement: High-resolution video oculography
Clinical Significance
Non-Motor Symptoms in PD
Non-motor symptoms are increasingly recognized as major contributors to disability in Parkinson's disease:
- Visual dysfunction affects up to 78% of PD patients
- Reading difficulty is a common complaint
- Reduced quality of life from oculomotor deficits
This study addresses a critical gap — understanding how DBS affects these understudied symptoms.
Optimizing DBS Parameters
By correlating stimulation location with vergence outcomes, this research may enable:
Individualized targeting — optimize electrode placement for each patient's symptom profile
Parameter optimization — adjust stimulation settings to improve both motor and oculomotor symptoms
Outcome prediction — predict which patients will benefit from STN DBS for oculomotor function
Novel targets — identify alternative brain regions for oculomotor controlVeterans Health Priority
As a VA-funded study, this research directly addresses the health needs of veterans with Parkinson's disease, a population with significant service-related exposures and age-related neurodegenerative disease risk.
Research Team
| Role | Name | Contact |
|------|------|---------|
| Principal Investigator | Aasef G. Shaikh, MD PhD | (216) 791-3800 ext 60000 |
| Study Coordinator | Monica O'Loughlin | (216) 791-3800 |
| Study Coordinator | Cheryl Dudek | 216-679-3800 |
Institution: Louis Stokes VA Medical Center, Cleveland, OH 44106-1702
Related Pages
- [Parkinson's Disease](/diseases/parkinsons-disease)
- [Deep Brain Stimulation](/therapeutics/deep-brain-stimulation)
- [Subthalamic Nucleus](/cell-types/subthalamic-nucleus-neurons)
- [Oculomotor Nucleus](/cell-types/oculomotor-nucleus-neurons)
- [Basal Ganglia](/brain-regions/basal-ganglia)
- [Clinical Trials in Parkinson's Disease](/clinical-trials/parkinsons-disease)
- [VA Parkinson's Disease Research](/institutions/va-parkinsons-disease-research)
External Links
- [ClinicalTrials.gov: NCT05400499](https://clinicaltrials.gov/study/NCT05400499)
- [Louis Stokes VA Medical Center](https://www.cleveland.va.gov/)
- [VA Office of Research and Development](https://www.research.va.gov/)
References
[NCT05400499 - Deep Brain Stimulation for Visuomotor Function in Parkinson's Disease](https://clinicaltrials.gov/study/NCT05400499)
[Deep brain stimulation mechanisms - Nature Reviews Neurology](https://doi.org/10.1038/s41582-020-00454-5)
[Ocular motor and visual dysfunction in Parkinson's disease - Progress in Retinal and Eye Research](https://doi.org/10.1016/j.preteyeres.2022.100994)
[Motor and non-motor effects of chronic DBS - Parkinsonism & Related Disorders](https://doi.org/10.1016/j.parkreldis.2021.03.006)