STN or GPi: How Is the DBS Target Selected?
In brief
The subthalamic nucleus (STN) and the internal globus pallidus (GPi) are the two most frequently selected targets for deep brain stimulation in Parkinson’s disease.
Both can improve appropriate levodopa-responsive motor symptoms. The choice is not simply about which target is “better”; it depends on the patient’s symptoms, medication goals, cognitive and psychiatric profile, age and the experience of the multidisciplinary DBS team.
What are the STN and GPi?
The STN and GPi are small structures located deep within the brain. Both are part of the networks that regulate movement.
Parkinson’s disease disrupts activity within these networks. DBS delivers carefully programmed electrical stimulation to a selected target, helping modify abnormal signalling.
The electrodes are not placed in the same target for every patient. Preoperative assessment is used to decide which target is more suitable.
Does one target control movement better?
For many patients, both STN and GPi stimulation can improve tremor, rigidity, bradykinesia and motor fluctuations.
Evidence-based guidance from the Congress of Neurological Surgeons concludes that bilateral STN and GPi DBS are both effective for improving motor symptoms. Either target may therefore be considered when motor improvement is the principal goal.
The differences become more relevant when the team considers medication reduction, dyskinesia, cognition, mood and the patient’s long-term treatment priorities.
When may STN DBS be considered?
STN DBS may be considered when:
Motor symptoms respond clearly to levodopa
Medication “off” periods are a major problem
Reducing dopaminergic medication is an important objective
Tremor, rigidity and slowness are prominent
The patient can participate reliably in postoperative programming
A reduction in medication may be possible after STN DBS, but it should be gradual and supervised. DBS does not mean that every patient will stop Parkinson’s medication completely.
When may GPi DBS be considered?
GPi DBS may be considered when:
Troublesome dyskinesia is a major concern
Medication reduction is not the primary objective
Greater flexibility in medication management is desirable
The clinical team has concerns about cognitive or mood vulnerability
The patient’s individual symptom pattern favours pallidal stimulation
GPi stimulation can reduce dyskinesia directly as well as through improved motor control. However, these are general considerations rather than fixed rules.
How do cognition and mood affect target selection?
DBS candidates normally undergo cognitive and psychological assessment before surgery.
Significant cognitive impairment, uncontrolled depression, psychosis or severe behavioural problems may affect overall suitability for DBS—not only the choice between STN and GPi.
When cognitive decline or depression is a particular concern, the team may consider whether GPi offers advantages for that individual. The evidence is not identical for every outcome, so target selection should remain personalised rather than automatic.
Does tremor determine the target?
Both STN and GPi DBS can improve medication-resistant Parkinson’s tremor. For carefully selected tremor-dominant patients, another target known as the ventral intermediate nucleus of the thalamus—VIM—may occasionally be discussed.
However, VIM stimulation mainly addresses tremor and generally has less effect on the broader Parkinson’s symptom profile. STN and GPi therefore remain the principal targets for most Parkinson’s DBS procedures.
What information is reviewed before choosing?
The multidisciplinary DBS team may review:
Response to levodopa
Severity of tremor, rigidity and bradykinesia
Duration and frequency of “off” periods
Dyskinesia severity
Current medication burden
Speech, gait and balance symptoms
Cognitive testing
Mood and behavioural history
Brain MRI findings
Age, general health and surgical risk
The patient’s personal treatment priorities
Modern DBS planning is therefore not only about finding a point on an MRI. It combines anatomy with the patient’s complete clinical profile. Contemporary reviews increasingly describe this as a precision-care approach.
My approach to target selection
In my discussions with patients, I explain that STN and GPi are not competing versions of the same operation.
The goal is to select the target whose expected benefits best match the patient’s most disabling symptoms while considering medication goals and possible adverse effects. Final planning should be made jointly by the movement-disorders neurologist, neurosurgeon, neuropsychology team and patient.
For an overview of surgical steps, read How Is Deep Brain Stimulation Surgery Performed?.
You can also review Who Is a Suitable Candidate for DBS Surgery?.
Frequently asked questions
Is STN the most commonly used DBS target?
STN is widely used for Parkinson’s disease, particularly when medication reduction is an important goal. This does not mean it is automatically the best target for every patient.
Can both STN and GPi improve dyskinesia?
Yes. Both may improve dyskinesia, although they may do so through partly different mechanisms. The patient’s medication goals influence the choice.
Can different targets be used on each side?
This is possible in selected and unusual circumstances, but most patients receive bilateral stimulation of the same target. The decision depends on symptom asymmetry and the treatment strategy.
Is the target chosen only from the MRI?
No. MRI is essential for anatomical planning, but target selection begins with the patient’s symptoms, medication response, cognition, mood and treatment expectations.
Conclusion
STN and GPi are both established DBS targets for Parkinson’s disease. Neither is universally superior.
The best target is the one that fits the individual patient’s motor symptoms, dyskinesia, medication goals, cognitive and psychiatric profile and long-term treatment plan.
Dr Kaan Tuğberk ÖzdemirNeurosurgeon – İzmir, Türkiye
This article provides general medical information and does not replace an individual consultation or multidisciplinary DBS assessment.
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