Neurostimulation in tardive dystonia/dyskinesia: A delayed start, sham stimulation-controlled randomized trial.

Introduction: Growing evidence suggests that pallidal deep brain stimulation represents a potential new therapeutic avenue in tardive dystonia/dyskinesia, but controlled and blinded randomized studies (RCT) are missing. The present RCT compares dystonia/dyskinesia severity of pallidal neurostimulation in patients with tardive dystonia using a delayed-start design paradigm.

Methods: Dystonia/dyskinesia severity was assessed via blinded videos following pallidal neurostimulation at 3 (blinded phase) and 6 months (open extension phase). Primary endpoint was the percentage change of dystonia severity (Burke-Fahn-Marsden-Dystonia-Rating-Scale, BFMDRS) at 3 months between active vs. sham neurostimulation using blinded-video assessment. Secondary endpoints comprised clinical rating scores for movement disorders. Clinicaltrials.gov NCT00331669.

Results: Twenty-five patients were randomized (1:1) to active (n = 12) or sham neurostimulation (n = 13). In the intention-to-treat analyses the between group difference of dystonia severity (BFMDRS) between active vs. sham stimulation was not significant at 3 months. Three months post-randomisation dystonia severity improved significantly within the neurostimulation by 22.8% and non-significantly within the sham group (12.0%) compared to their respective baseline severity. During the open-label extension with both groups being actively treated, significant and pronounced improvements of 41.5% were observed via blinded evaluation. Adverse events (n = 10) occurred in 10/25 of patients during the 6 months, mostly related to surgical implantation of the device; all resolved without sequelae.

Conclusion: The primary endpoint of this randomized trial was not significant, most likely due to incomplete recruitment. However, pronounced improvements of most secondary endpoints at 3 and 6 months provide evidence for efficacy and safety of pallidal neurostimulation in tardive dystonia.