Comparison of Pallidal With Subthalamic Deep Brain Stimulation for Cervical Dystonia

Cervical dystonia (CD), also known as spasmodic torticollis, is a type of focal dystonia, mainly manifesting as involuntary head turning or tilting, or holding a twisted posture. Although it can be alleviated by injection of botulinum toxin, the effect is temporary so that patients require multiple injections. Deep Brain Stimulation (DBS) targeting on globus pallidus internus (GPi) or subthalamic nucleus (STN) has been proved to be a safe and effective strategy for primary cervical dystonia, even for those medically refractory cases. However, the question of which target is better has not been clarified.

Therefore, the invstigators design this randomized and controlled trial, aiming to compare the differences between GPi-DBS and STN-DBS for cervical dystonia in the improvement of symptoms , quality of life, mental status, cognitive status, as well as in stimulation parameters and adverse effects. The invstigators hypothesize that STN-DBS will outperform GPi-DBS at short-term follow-up, while the superiority will disappear and the efficacy of the two group will become similar at long-term follow-up.

CD limits the neck activity by involving one or a group of neck muscles and is often accompanied by pain and psychological disorders, seriously affecting the quality of life. GPi and STN are two dominant targets for DBS, either of which has been widely used in the treatment of CD with remarkable efficacy (about 50%-90% symptomatic improvement rate). However, there has been no prospective studies to directly compare the DBS efficacy of these two targets.

The invstigators plan to design a multicenter, prospective, randomized, parallel-controlled equivalent clinical trial, aiming to compare GPi-DBS with STN-DBS for drug-resistant CD in the following aspects: (1) improvement rate of dystonic symptoms, (2) improvement rate of life quality, mental and cognitive status, (3) stimulation parameters, (4) adverse effects.

According to the inclusion and exclusion criteria, a total of 98 idiopathic or hereditary isolated CD patients will be enrolled, each of whom will be randomly divided into GPi-DBS group or STN-DBS group in a 1:1 ratio by central randomization. Informed consent forms are signed and information at baseline is collected. A standardized video will be recorded to assess the severity of the disease. The DBS electrodes will be implanted into posteroventral GPi (GPi-DBS group) or dorsolateral STN (STN-DBS group) respectively. The other operation procedures and subsequent follow-up plan are the same. The DBS device will be switched on in four weeks postoperatively and the optimal stimulation parameters will be used. The invstigators will record standardized videos and/or complete a series of clinical scales (see outcome measures) for all patients at baseline, four weeks postoperatively (after activation of DBS device), three months postoperatively, six months postoperatively, and one year postoperatively. Meanwhile, the stimulation parameters and adverse effects will also be documented. Finally, two professional raters will assess the severity of CD (reflected by Toronto Western Spasmodic Torticollis Rating Scale and Tsui scale) at different timepoints according to those standardized videos in a blind manner.

Intention-to-treatment analysis and per protocol analysis are both conducted by a professional data analyst.

Eligibility Criteria:
Inclusion criteria

1. Diagnosed as idiopathic or hereditary isolated CD;
2. Severe functional impairment;
3. Oral medication and injection of botulinum toxin become ineffective (\> 3 months since last injection), or refuse to adopt botulinum toxin injection;
4. No secondary causes of CD;
5. Age 18-80 years old;
6. Normal neurological examination except for dystonia;
7. Normal brain MRI;
8. The subject or their family members can fully understand the trial and sign the informed consent;
9. Good compliance and willingness to receive regular follow-ups.

Exclusion criteria

1. Diagnosed as secondary CD;
2. CD with obvious trunk/limb involvement, or Meige syndrome;
3. History of severe mental disorders, dementia, or epilepsy;
4. Previous dystonia surgery (pallidotomy, thalamotomy, DBS, etc);
5. Accompanied by other neurological diseases (Parkinson's disease, essential tremor, multiple sclerosis, stroke, etc);
6. The patient has or needs other implantable devices (cardiac pacemakers, defibrillators, cochlear implants, spinal cord stimulators, etc);
7. Pregnant women or women who are waiting to become pregnant during the trial;
8. Poor health condition.