Bilateral pallidal stimulation for sargoglycan epsilon negative myoclonus.

We report on the clinical efficacy of bilateral globus pallidus internus deep brain stimulation in two patients with myoclonus dystonia/essential myoclonus who lack mutations in the epsilon sarcoglycan gene. The primary outcome measures were the Burke-Fahn-Marsden Dystonia Scale motor severity and the Unified Myoclonus Rating Scale scores, and the secondary outcome measure was the 36-item Short Form Health Survey score at the last postoperative follow up. Neuronal firing rates were also calculated from microelectrode recordings. At the last postoperative follow-up (16 weeks for Patient 1 and 18 weeks for Patient 2), there was 57.1% (Patient 1) improvement in the Burke-Fahn-Marsden Dystonia Scale motor severity score and 31.3% (Patient 1) and 69% (Patient 2) in the Unified Myoclonus Rating Scale score while individual SF-36 scores showed improvement in most subdomains. Bilateral globus pallidus internus deep brain stimulation can be effective in ameliorating epsilon sarcoglycan negative myoclonus with or without concurrent dystonia. Whether an epsilon sarcoglycan negative status represents a less favorable prognostic factor for pallidal deep brain stimulation remains to be elucidated.