Indications for Deep Brain Stimulation in Advanced Parkinson's Disease
DBS is indicated for patients with advanced idiopathic Parkinson's disease who have disabling motor symptoms—including motor fluctuations, dyskinesias, or medication-resistant tremor—that persist despite optimal dopaminergic therapy. 1, 2
Core Patient Selection Criteria
Motor Symptom Requirements
- Disabling motor response fluctuations (unpredictable "off" periods despite medication adjustments) 3, 4
- Severe levodopa-induced dyskinesias that limit functional capacity 3, 5
- Medication-resistant tremor that interferes with daily activities 6, 4
- Painful dystonia refractory to medical management 7
Disease Characteristics That Support DBS Candidacy
- Confirmed levodopa responsiveness is essential—patients must demonstrate clear motor improvement with dopaminergic medications, as DBS efficacy parallels medication response 3, 4
- Inadequate symptom control with best medical treatment despite optimization of medication timing, dosing, and formulations 3, 5
- Preserved cognitive function without significant dementia (though emerging research is exploring DBS in PD dementia) 7, 4
Target Selection Algorithm
The choice between subthalamic nucleus (STN) and globus pallidus internus (GPi) depends on specific patient goals and risk factors:
Choose STN-DBS When:
- Primary goal is medication reduction—STN-DBS allows significant reduction in dopaminergic medications, which GPi does not 1, 2
- Patient has no significant cognitive concerns or depression risk 1
- Both motor symptom control and medication burden reduction are priorities 1
Choose GPi-DBS When:
- Significant concern exists about cognitive decline, particularly processing speed and working memory 1, 2
- Risk of depression is substantial—GPi carries lower mood disturbance risk than STN 1
- Primary goal is controlling "on" medication dyskinesias without reducing medication doses 1
- Patient is older or has mild baseline cognitive changes 4, 8
Either Target Is Appropriate When:
- Motor symptom control alone is the goal—both targets produce equivalent UPDRS-III improvements 1
- Quality of life improvement is the primary outcome—no difference exists between targets 1
Critical Exclusion Criteria
Absolute Contraindications
- Severe, medically-resistant axial symptoms including balance disturbances, gait freezing, and frequent falls—these symptoms are non-dopaminergic and will not respond to DBS 4
- Atypical parkinsonism (progressive supranuclear palsy, multiple system atrophy, corticobasal degeneration)—DBS is only effective in idiopathic PD 3, 4
- No levodopa responsiveness—if medications don't work, DBS won't work 3, 4
Relative Contraindications Requiring Careful Consideration
- Advanced cognitive impairment or dementia—though traditionally excluded, this is being investigated in research settings 7, 4
- Severe, uncontrolled psychiatric disease including major depression or psychosis 4
- Advanced age with multiple comorbidities increasing surgical risk 4
Timing Considerations
- Mean disease duration at DBS is approximately 13 years, though earlier intervention is being investigated to prevent psychosocial decline 3
- DBS should be considered before severe axial symptoms develop, as these become progressively less responsive to any intervention 4
- Long-term efficacy is sustained—appendicular motor symptoms remain responsive for years, though axial features eventually progress 4, 5
Common Pitfalls to Avoid
- Do not offer DBS as a cure or disease-modifying therapy—it is purely symptomatic treatment that does not stop neurodegeneration 5
- Do not select patients with predominant axial symptoms—gait, balance, and postural instability respond poorly regardless of target 4
- Anticipate dysarthria as the most common side effect regardless of target selection 4
- Ensure multidisciplinary evaluation including movement disorder neurology, functional neurosurgery, neuropsychology, and specialized nursing before proceeding 4, 5