Objective: To quantify the response of isolated non-acquired dystonia to deep brain stimulation (DBS) of the globus pallidus interna (GPi) across multiple body regions.

Background: Dystonia is characterized by muscle contractions causing abnormal movements or postures leading to functional impairment and diminished quality of life. DBS emerged as an effective treatment for refractory dystonia. The response to DBS has been shown to vary across body regions and the literature predicting dystonia response to DBS is conflicting. This study analyzes response to DBS by dystonia distribution in patients with isolated non-acquired dystonia. While most literature in focal dystonia utilizes only BFMRS-M, we present a unique perspective by including GDRS metrics.

Method: We performed a retrospective analysis using standardized videos of patients with isolated non-acquired dystonia obtained at baseline and post-DBS in unilateral or bilateral GPi between 2008 and 2020. GDRS and BFMRS-M were scored using blinded, randomized assessment of videos individually rated and averaged between two movement disorders neurologists. If sub-scores differed by ≥2 or total score differed by ≥3, a third neurologist’s score was included.

Results: We followed 20 patients (10 male, 10 female) with average disease duration of 15 years and average follow-up of 14 months. All patients had improved total GDRS scores (>50%: n=11; <50%: n=9). There were significant improvements between baseline vs post-DBS GDRS in the neck (5.9±0.6 vs 2.6±0.4; p<0.001), shoulder & proximal arms (4.7±1.1 vs 1.6±0.5; p<0.01), distal legs & feet (5.3±1.9 vs 2.8±1.1; p<0.05), trunk (4.9±1.1 vs 0.5±0.5; p<0.01), and total dystonia (21.6±3.7 vs 11.1±2.1; p<0.001). Post-DBS total BFMRS-M scores were incongruent with total GDRS scores (>50% improvement: n=10; <50% improvement: n=8; worse: n=2). There were significant improvements in BFMRS-M scores post-DBS in patients with neck (4.9±0.6 vs 2.5±0.4; p<0.001) and total dystonia (20.5±3.6 vs 11.9±2.6; p<0.01).

Conclusion: The efficacy of DBS varies by body distribution of dystonia and this differential response should be considered in treatment planning discussions between physicians and patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/deep-brain-stimulation-in-dystonia-investigating-differential-response-by-dystonia-distribution/