Early deep brain stimulation in patients with myoclonus-dystonia syndrome

Abstract

Myoclonus-dystonia (MD) is a rare movement disorder which is disabling and frequently refractory to medical treatment. Deep brain stimulation (DBS) of the globus pallidus interna (GPi) has been used to treat some patients. Although there is significant motor improvement with DBS, the impact on disability and on quality of life has been infrequently reported. Also, the benefit of the procedure is not established in patients without ε-sarcoglycan gene (SGCE) mutations. We present two patients with severe MD treated with GPi-DBS, one of the patients without a SGCE mutation. Motor improvements (rest/action/total subscores of the Unified Myoclonus Rating Scale and movement subscore of the Burke-Fahn-Marsden Dystonia Rating Scale [BFMRS]) and disability (BFMRS disability subscore) were carefully evaluated preoperatively and at 6 and 12months after surgery. Quality of life (addressed using the Portuguese version of the Medical Outcomes Study 36-item Short-Form General Health Survey, version 2.0 [SF-36v2]) was tested preoperatively and 12months after DBS. At 12-month follow-up, myoclonus improved 78.6% in Patient 1 and 80.7% in Patient 2, while dystonia improved 37% and 86.7%, respectively. Improvements in disability ranged from 71.4% to 75%. With regard to quality of life, all parameters addressed by the SF-36v2 improved or stabilized in both patients. No major adverse effects were noticed. Improvements in motor symptoms are consistent with reports in the literature and were obtained regardless of the identification of a SGCE gene mutation. There were also significant benefits on disability and quality of life. DBS should be considered for MD.

Keywords: Deep brain stimulation; GPi; Globus pallidus; Myoclonus-dystonia syndrome; Quality of life; VIM.