A prospective pilot trial for pallidal deep brain stimulation in Huntington´s disease

Background: Movement disorders in Huntington´s disease are often medically refractive. The aim of the trial was assessment of procedure safety of deep brain stimulation, equality of internal- and external-pallidal stimulation and efficacy followed-up for 6 months in a prospective pilot trial. Methods: In a conrolled double-blind phase 6 patients (4 chorea-dominant, 2 Westphal-variant) with predominant movement disorder were randomly assigned to either the sequence of 6 week internal-/6 week external-pallidal stimulation, or vice versa, followed by further 3 months chronic pallidal stimulation at the target with best effect-side-effect ratio. Primary endpoints were changes in the Unified Huntington´s Disease Rating Scale motor-score, chorea subscore and total motor-score 4 (blinded video ratings), comparing internal- versus external-pallidal stimulation, and 6 month versus baseline. Secondary endpoints assessed scores on dystonia, hypokinesia, cognition, mood, functionality/disability and quality-of-life. Results: Intention-to-treat analysis of all patients (n=3 in each treatment sequence): Both targets were equal in terms of efficacy. Chorea subscores decreased significantly over 6 months (-5.3 (60.2%), p=0.037). Effects on dystonia were not significant over the group due to it consisting of three responders (>50% improvement) and three non-responders. Westphal patients did not improve. Cognition was stable. Mood and some functionality/disability and quality-of-life scores improved significantly. 8 adverse events and 2 additional serious adverse events - mostly internal-pallidal stimulation-related - resolved without sequalae. No procedure-related complications occurred. Conclusion: Pallidal deep brain stimulation was demonstrated to be a safe treatment option for the reduction of chorea in Huntington´s disease. Their effects on chorea and dystonia and on quality-of-life, should be examined in larger controlled trials.