Alteration of Deep Brain Stimulation Parameters for Dystonia

Study Overview
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Brief Summary
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Deep brain stimulation (DBS) involves placing electrodes into the brain. Through these electrodes, artificial electrical signals are chronically delivered into deep brain regions in order to alter abnormal brain activity. The artificial electrical signals are generated by a battery that is inserted under the skin of the chest. DBS is used to treat several disorders of movement, including dystonia. In dystonia, the electrodes are inserted into a brain region called the globus pallidus. Globus pallidus stimulation can be very effective therapy for dystonia. However not all patients are equally responsive and therapeutic outcomes can be frustratingly variable. The reason for this variability is unclear. Such variability in response may need to be met by tailoring stimulation to individual patients. Another issue with deep brain stimulation is battery life. Eventually, batteries become depleted and need to be replaced. Such battery replacements require an operation, hospital stay and the risk of introducing infection. The high electrical energy that has been used to treat dystonia means that batteries are typically replaced every year or two. The artificial electrical signals of deep brain stimulation are delivered with three parameters; frequency (Hertz - Hz), voltage (volts) and pulse width (microseconds). It has recently been reported that lower frequency stimulation, at 60Hz rather than 130Hz, can be used effectively to treat dystonia. Such 60Hz stimulation may be more effective for some patients than others. The lower energy demands of 60Hz stimulation would also greatly improve battery life (potentially doubling battery life). The aim of this study is to assess if 60Hz stimulation is more effective in ameliorating the dystonia of patients who have responded poorly to 130Hz pallidal stimulation. The current status of the evidence is one of clinical equipoise (uncertainty) and therefore suits a double blinded randomised trial.

Official Title
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Alteration of Deep Brain Stimulation Parameters for Dystonia- A Double Blinded Randomised Controlled Trial

Conditions
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Dystonia

Intervention / Treatment
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* Procedure: Alteration of deep brain stimulator settings


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Primary dystonia (focal cervical or generalised dystonia) who are receiving chronic (>1 year) bilateral pallidal stimulation but have had poor therapeutic responses (< 50% improvement in relevant dystonia severity rating scale*) despite confirmation of accurate electrode position. Able to understand study requirements - able to provide consent. Relevant dystonia rating scales: Cervical dystonia - severity subsection of the Toronto Western Hospital spasmodic torticollis rating scale; Generalised dystonia - severity section of the Burke Fahn Marsden rating scale. Exclusion Criteria: None.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Treatment
Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: 60 Hz stimulation<br>Experimental reduced frequency pallidal stimulation | Procedure: Alteration of deep brain stimulator settings<br>* From 130Hz to 60Hz pallidal stimulation<br>|
| No Intervention: 130 Hz stimulation<br>Current standard pallidal stimulation setting | Procedure: Alteration of deep brain stimulator settings<br>* From 130Hz to 60Hz pallidal stimulation<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| To assess if the stimulation frequency of 60 Hz is superior to 130 Hz for patients with primary dystonia who have responded poorly to standard 130 Hz pallidal stimulation |  | 6 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Assess any potential changes in anxiety, mood, cognition |  | 6 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Dystonia