Subthalamic nucleus deep brain stimulation in isolated dystonia: A 3-year follow-up study

Objective: To report long-term safety and efficacy outcomes of a large cohort of patients with medically refractory isolated dystoniatreated with subthalamic nucleus(STN) deep brain stimulation(DBS). Methods: Twenty patients (12 male, 8 female; mean age 49 ± 16.3 years) with medically refractory isolated dystoniawere studied (14 were followed for 36 months). The primary endpoints were change in Burke-Fahn-Marsden DystoniaRating Scale (BFMDRS) motor score and Toronto Western Spasmodic TorticollisRating Scale (TWSTRS) total score at 36 months compared to preoperative baseline. Multiple secondary outcomes were also assessed (ClinicalTrials.govNCT00773604). Results: Eighteen of 20 patients showed improvement 12 months after STN DBS with sustained benefit persisting for 3 years (n = 14). At 36 months, BFMDRS motor scores improved 70.4% from a mean 17.9 ± 8.5 to 5.3 ± 5.6 ( p = 0.0002) and total TWSTRS scores improved 66.6% from a mean 41.0 ± 18.9 to 13.7 ± 17.9 ( p = 0.0002). Improvement at 36 months was equivalent to that seen at 6 months. Disability and quality of life measures were also improved. Three hardware-related and 24 stimulation-related nonserious adverse events occurred between years 1 and 3 (including 4 patients with dyskinesia). Conclusions: This study offers support for long-term tolerability and sustained effectiveness of STN DBS in the treatment of severe forms of isolated dystonia. Classification of evidence: This study provides Class IV evidence that STN DBS decreases long-term dystoniaseverity in patients with medically refractory isolated dystonia.