Treatment of myoclonus-dystonia syndrome with tetrabenazine

Background: Many cases of myoclonus-dystonia (M-D) are due to mutations in SGCE (DYT11). For the majority of patients, myoclonus is relatively more severe than dystonia and can lead to significant functional disability. Deep brain stimulation has been chosen as a treatment option in some patients given that M-D often responds poorly to oral pharmacotherapy. Methods: Two siblings with M-D due to the same SGCE deletion mutation were evaluated with the Global Dystonia Rating Scale (GDRS), Fahn-Marsden Rating Scale (FM) and Unified Myoclonus Rating Scale (UMRS) on and off tetrabenazine. Results: Both subjects showed marked improvement in myoclonus and mild-to-moderate improvement in dystonia with tetrabenazine. In addition, the response to tetrabenazine has been sustained for years. Conclusions: A therapeutic trial of tetrabenazine should be considered in patients with M-D, especially before consideration of deep brain stimulation. An adequately powered multi-center, double-blind study of tetrabenazine will be required to determine the relative contributions of tetrabenazine therapy to myoclonus, dystonia, quality of life, and activities of daily living in patients with M-D. (C) 2014 Elsevier Ltd. All rights reserved.