Huntington’s disease (HD) is a hereditary neurodegenerative disorder which is associated with severe disturbances of motor function, especially choreatic movements, cognitive decline and psychiatric symptoms. Various brain stimulation methods have been used to study brain function in patients with HD. Moreover, brain stimulation has evolved as an alternative or additive treatment option, besides current symptomatic medical treatment. We intend to better understand the characteristics of cortical excitability and plasticity in HD and give a perspective on the therapeutic role for non-invasive and invasive neuromodulative brain stimulation methods. We furthermore assessed procedure safety of deep brain stimulation, equality of internal- and external-pallidal stimulation and efficacy followed up for 6 months in a registererd prospective pilot trial (ClinicalTrials.gov NCT00902889).

We studied 6 patients (4 chorea-dominant, 2 Westphal-variant) with predominant movement disorder 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.

Intention-to-treat analysis included all 6 patients with 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.

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.