Dystonia is a group of movement disorders characterized by twisting, repetitive movements, or abnormal postures caused by involuntary muscle contractions and is characterized by a young age of onset and a high disability rate. Early intervention can reduce disability incidence, improve the patient's quality of life, and reduce the burden on families and society. Multiple international guidelines on dystonia have found deep brain stimulation (DBS) to be a safe and effective treatment for refractory dystonia. The globus pallidal internus (GPi) is the mostly widely used target for dystonia. However, there are limitations on the GPi DBS treatment, including slow onset of beneficial effects, poor improvement of axis symptoms, and potential stimulation-related side effects. Previous studies have described the highly successful use of subthalamic nucleus deep brain stimulation (STN DBS) in patients with refractory dystonia, suggesting that STN DBS is an effective and persisting alternative to pallidal deep brain stimulation. However, all STN DBS treated cases have been analyzed in open-label uncontrolled cohort studies, leading to limited data with a high level of evidence on the STN DBS in dystonia. Further, the investigators hypothesized STN has potentially more effectiveness when compared with GPi, and may be more power-saving and quick-acting. In this study, the investigators will organize a prospective randomized, double-blind, parallel-group, multicenter study comparing active versus sham stimulation in isolated segmental or generalized dystonia to evaluate the effectiveness and safety of STN DBS by measuring the impact on motor status, mental status, quality of life, the rate of response of the patients (the number of patients with ≥30% improvement in the movement score on the Burke-Fahn-Marsden Dystonia Rating Scale) and the rate of adverse events during the trial.

Inclusion Criteria:

1. Patients must meet criteria for the diagnosis of isolated generalized or segmental dystonia, including idiopathic and inherited dystonia, as defined by the Phenomenology and Classification of Dystonia: A Consensus Update 2013;

2. Patients will be ≥ 14 years old;

3. The course of disease will be ≥ 3 years;

4. Patients will have:

   1. Significant dystonia symptoms;
   2. Compromised life quality;
   3. Unsatisfactory response to oral treatment with anticholinergic agents antiepileptic agents, anti-dopamine agents, dopaminergic agents, or muscle relaxants;
   4. Unsatisfactory response to or contraindication for previous botulinum toxin treatment; and
   5. Ability to provide written informed consent.

Exclusion Criteria:

1. Patients with a diagnosis or probable diagnosis of acquired, compound, and complex dystonia, as defined by the Phenomenology and Classification of Dystonia: A Consensus Update 2013;
2. Previous brain surgery for dystonia;
3. Patients with cognitive impairment (MMSE score <24) or moderate-severe depressive disorder (BDI>25);
4. Patients with marked brain atrophy identified by magnetic resonance imaging (MRI) or computed tomography (CT);
5. Patients with other medical or psychiatric comorbidities that could increase the surgical risk or interfere with completion of the trial;
6. Patients with increased bleeding risk, or other factors contraindicating neurosurgery or general anesthesia;
7. Patients unable to cooperate with the assessments during the follow-up.

The randomization will be conducted by the Coordination Center of Clinical Trials (CenTrial) in order to keep the researchers managing the data and the statistician blind to group assignment and the study conditions. All the clinical assessments done during the trial period will be double-blind, e.g., neither the patient not the clinician or study personnel involved in the scoring will not be aware of the condition of stimulation. All personnel, except the physician-programmer responsible for the DBS setting, will be blinded to the identity of the parameters. While programming the programmer will not sit face-to-face with the patient, but in another room adjusting the parameter wirelessly with the help of the attending doctor who will inform the programmer of the patient's reaction. The electrical parameters will be tested in all patients which means they all will perceive similar stimulation related sensations during each follow-up.