Long‐term effects of pallidal and thalamic deep brain stimulation in myoclonus dystonia

Objective Observational study to evaluate long‐term effects of deep brain stimulation (DBS) of the globus pallidus internus (GPi) and the ventral intermediate thalamic nucleus (VIM) on patients with medically refractory myoclonus dystonia (MD). Background More recently, pallidal as well as thalamic DBS have been applied successfully in MD but long‐term data are sparse. Methods We retrospectively analyzed a cohort of seven MD patients with either separate (n = 1, VIM) or combined GPi‐ DBS and VIM‐DBS (n = 6). Myoclonus, dystonia and disability were rated at baseline (BL), short‐term (ST‐FU) and long‐term follow‐up (LT‐FU) using the United Myoclonus Rating Scale, Burke−Fahn−Marsden Dystonia Rating Scale (BFMDRS) and Tsui rating scale, respectively. Quality of life (QoL) and mood were evaluated using the SF‐36 and Beck Depression Inventory questionnaires, respectively. Results Patients reached a significant reduction of myoclonus at ST‐FU (62% ± 7.3%; mean ± SE) and LT‐FU (68% ± 3.4%). While overall motor BFMDRS changes were not significant at LT‐FU, patients with GPi‐DBS alone responded better and predominant cervical dystonia ameliorated significantly up to 54% ± 9.7% at long‐term. Mean disability scores significantly improved by 44% ± 11.4% at ST‐FU and 58% ± 14.8% at LT‐FU. Mood and QoL remained unchanged between 5 and up to 20 years postoperatively. No serious long‐lasting stimulation‐related adverse events were observed. Conclusions We present a cohort of MD patients with very long follow‐up of pallidal and/or thalamic DBS that supports the GPi as the favourable stimulation target in MD with safe and sustaining effects on motor symptoms (myoclonus>dystonia) and disability. The present retrospective, long‐term study extends predominantly anecdotal evidence of beneficial long‐term effects of deep brain stimulation (DBS) in patients with myoclonus dystonia (MD) and provides extensive assessment of motor features (myoclonus, dystonia), disability, quality of life and mood in a very long follow‐up on an older MD population. Furthermore, this study provides data on combined thalamic and pallidal stimulation in MD and supports the GPi as the best DBS target on a long follow‐up in a real‐world setting.