Subthalamic deep brain stimulation in isolated generalised or segmental dystonia (RELAX Study): a multicentre, randomised, double-blind, controlled trial.

Background: The safety and effectiveness of deep brain stimulation of the subthalamic nucleus (STN-DBS) for the treatment of dystonia lack high-level evidence-based medical support. This study aimed to clarify the efficacy and safety of STN-DBS and perform a post hoc analysis comparing it with DBS of the internal globus pallidus (GPi-DBS).

Methods: This multicentre, randomised, double-blind, controlled trial included 67 patients aged 6-60 years old diagnosed with genetic or idiopathic isolated generalised or segmental dystonia. They were enrolled from seven hospitals in China and randomly assigned to undergo GPi-DBS or STN-DBS. After surgery, they were randomised to receive either neurostimulation or sham stimulation for 3 months. At the 3-month follow-up, neurostimulation was also initiated in the sham stimulation group, and all patients were followed up for more than 3 years after treatment. The primary outcome was the Burke-Fahn-Marsden Dystonia Rating Scale movement (BFMDRS-M) score.

Results: In the STN group, the neurostimulation subgroup exhibited significant improvement (p<0.001), which is also superior to the sham stimulation subgroup (p=0.028) at 3-month follow-up. At the 6-month and >3-year follow-ups, all patients receiving STN-DBS showed a significant improvement in BFMDRS-M scores (p<0.001). Further post hoc analysis revealed that both STN-DBS and GPi-DBS could produce similar therapeutic effects on motor symptoms (P_{6 months}=0.865, P_{>3 years}=0.905). There were no ongoing serious adverse events throughout the study.

Conclusions: For isolated generalised and segmental dystonia patients, the STN is a selectable DBS target with ensured safety and efficacy. STN-DBS and GPi-DBS may achieve comparable therapeutic effects on motor symptoms.

Trial registration number: NCT03017586.