Deep brain stimulation in children and adolescents with ε-sarcoglycan myoclonus dystonia causes a sustained improvement in motor functionality and quality of life

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This study evaluates the efficacy and safety of globus pallidus internus deep brain stimulation (GPi-DBS) in children and adolescents with SGCE-related myoclonus–dystonia (SGCE-MD). There are currently no pharmacological disease-modifying therapies for SGCE-MD, and available medications often provide limited benefit or cause significant side effects. While DBS is well established in adults with SGCE-MD, evidence in pediatric populations remains limited, and surgery is frequently postponed despite meaningful functional disability early in life. 

Methods

We analyzed 10 patients who underwent GPi-DBS at a mean age of 12.8 ± 3.4 years, with a mean follow-up of 3.8 ± 2.4 years. All patients had medically refractory symptoms. 

Motor outcomes were assessed using standardized rating scales, including the Unified Myoclonus Rating Scale (UMRS), the Burke-Fahn-Marsden Rating Scale (BFMRS), the Writer’s Cramp Rating Scale (WCRS), and the Gait Dystonia Rating Scale (GDRS). Quality of life was evaluated using Neuro-QoL measures, and psychiatric comorbidities were systematically monitored by a child psychiatrist. 

To ensure consistency and reduce rater bias, each patient was independently assessed by the principal investigator and a blinded expert using randomized pre- and post-operative video sequences. Final outcome scores represent the mean of the two independent ratings. 

Results

Motor outcomes:

Robust and sustained motor improvement was observed:  Myoclonus improved by approximately 68% (UMRS-T).  Overall dystonia improved by 63% (BFMRS-T).  Writing dystonia improved by 48% (WCRS).  Gait dystonia improved by 70% (GDRS-walking) and running dystonia improved by 44% (GDRS-running).  Clinical benefits emerged early (around 6 months post-implantation) and remained stable over long-term follow-up. Half of the patients were able to reduce or discontinue oral medications after surgery.

 

Non-motor outcomes:

Psychiatric symptoms, including anxiety, obsessive-compulsive traits, and attention difficulties, remained stable and did not worsen after DBS. Quality-of-life measures demonstrated improvement in domains such as anxiety, fatigue, and perceived stigma, with positive trends in social and cognitive functioning.

 

Surgery Accuracy, Stimulation Parameters and Safety:  

Electrode placement accuracy was high, with a mean targeting error of less than 0.9 mm in all axes. At last evaluation, patients were stimulated with standard stimulation parameters (2.5 [1.8–3.5] milliamps, 64 [60–80] μs, 137.3 [120–200] Hz), further demonstrating the accuracy of the procedure. 

Surgical complications were rare and manageable, and no serious long-term adverse events were reported. 

Take-home message

The study demonstrates that DBS-GPi is safe, effective and functionally meaningful in children and adolescents with SGCE-MD. 

Chronic stimulation produces a significant and sustained improvement in gross and fine motor function. Improving motor symptoms at an early age prevents long-lasting motor sequelae, potentially leading to better academic results and professional and social development, and a better quality of life in adulthood 

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