Alternative Deep Brain Stimulation Targets in the Treatment of Isolated Dystonic Syndromes: A Multicenter Experience-Based Survey.
Professors Krauss, Cif, Limousin and Hariz (well-known experts in DBS treatment for Dystonia for two decades) conducted an international survey (a total of 42 questions), involving 49 specialists from 28 medical centers across 13 countries, shedding light on how doctors are approaching DBS using alternative DBS Brain targets structures.
Dystonia may have numerous etiologies, with a variety of bodily distributions and clinical presentations. The patients who are refractory or receive insufficient relief from pharmacological treatments and botulinum toxin injections may benefit from deep brain stimulation (DBS).
Deep Brain Stimulation (DBS) has offered renewed hope for many living with inherited and idiopathic dystonia and acquired dystonia. Several publications and robust studies have been conducted to sustain these clinical outcomes even in the long term.
What happens when standard treatments do not work as expected?
The prediction of clinical response to DBS in Dystonia might be a challenge since there are no available pharmacological tests like the so called “levodopa challenge” in Parkinson’s disease that allow anticipating on the clinical response to DBS. Also, the full clinical effect of DBS in dystonia can be delayed by weeks or even months. However, it is now recognized that patients with isolated monogenic or idiopathic dystonia of both adult and pediatric onset (without associate additional neurological impairments and structural brain alterations on magnetic resonance imaging) benefit from GPi-DBS and are good responders.
“Dystonia is a disorder of neuronal networks consisting of defective inhibitions responsible for the excess of muscle contractions and involuntary movements. Excessive plasticity in the motor cortex leads to dysfunction at the network level which generates dystonia at the network level. DBS improves the dysregulated activity of the network. Some of the DBS-induced changes in dystonia are delayed,
explaining that improvement emerges over several weeks or months. Further studies of the physiological alterations and their distribution in the motor network induced by DBS in dystonia are necessary to better understand the variability of the clinical outcome, and the differences between responders and non-responders. Future improvements of DBS therapy in dystonia concern both the duration of the administration and the site of administration, with exploration of alternative brain targets to the Globus Pallidus internus (GPi) as well as multitargeting approaches.”
Dr. Cif
The Globus Pallidus Internus (GPi) is the traditional brain target for DBS in dystonia. However, some individuals don’t respond well at all, and others experience improvement at first but later lose the benefit.
When Do Doctors Consider a Patient as non-responder?
- Most clinicians wait 12–18 months before concluding that GPi-DBS isn’t working.
- For those who initially improved but worsened later, most secondary failures occurred after 3 years.
Objective of the Survey and structure
The survey was distributed to a total of 91 clinicians from 28 DBS centers and 13 countries, including Europe, the United States, Canada, and India. The main objective was to collect information about Treatment strategies for Dystonia in DBS.
The 42 questions were structured into 4 domains:
- Use of alternative DBS targets to the GPi in dystonia patients as either primary or additional targets (rescue targets)
- Selection of the alternative target(s) according to dystonia phenomenology.
- Experience with dystonia patients’ secondary non-responders to pallidal DBS.
- DBS management in patients who received additional leads
The Results of the Survey
The survey clearly showed a common strategy: over 85% of neurologists and neurosurgeons surveyed commonly use Alternative DBS Brain targets, especially for patients who do not respond well to GPi-DBS.
The most common alternatives Brain Targets (Alternative Options for patients) to GPi include:
- Subthalamic Nucleus (STN) – most frequently used as a rescue option when GPi fails.
- Ventral Intermediate Nucleus (Vim) – often used when tremor is a major symptom.
- Other Thalamic Areas and the Zona Incerta – occasionally selected based on the specific type and location of dystonia.
Although rare, pediatric neurologists also reported using alternative DBS targets.
Advanced DBS treatment with Multiple Targets
In complex cases, especially when dystonia is mixed with tremor, some doctors use multiple DBS targets. In these cases:
- Around two-thirds kept both areas stimulated.
- Some centers implanted multiple leads during one procedure; others did so in stages.
“Since we have introduced pallidal DBS for the treatment of dystonia in the 1990s, numerous studies have shown both its efficacy and its safety. DBS has been applied to more than 20.000 patients with dystonia over the last decades. Nevertheless, it has been recognized that the response to pallidal DBS differs among individuals related to the genetic background and to the phenotype of dystonia. Stimulation of alternative targets, possibly also in the frame of a multitarget approach, would provide a window for further improvement of care.”
Prof. Krauss
Eventually, in recent months new 16-contacts leads are available in the market (reference: Cartesia X, HX and Genus PC, RC). They allow experts to target different areas with the same trajectory in one lead, since the lead has a longer span of stimulating contacts.
“Understanding which brain circuits are active in different types of dystonia may help us tailor DBS therapy better. While alternative DBS targets show promise and are increasing use, we still need well-designed studies to understand which patients benefit most and why. More research is critical to refine our approach and improve outcomes for all individuals living with dystonia.”
Prof. Limousin
The main focus areas for next research should be:
- Understand why some patients don’t respond to GPi-DBS.
- Optimize the use of other DBS targets.
- Better prediction of who will benefit.
This study confirms that many experts are working on ways to expand treatment options and improve outcomes for patients with complex or resistant forms of dystonia, helping to guide personalized decisions, including whether other DBS options may be worth exploring.
If you are interested in accessing the full article: https://pubmed.ncbi.nlm.nih.gov/39801349/
To learn more about dystonia and treatment options, scan the QR code or visit bostonscientific.eu/dystonia.
