Pallidal Deep Brain Stimulation in Dystonia: Investigating Differential Response by Dystonia Distribution

Dystonia is characterized by involuntary intermittent or sustained abnormal movements or postures. Deep brain stimulation (DBS) is an effective treatment, and response has been shown to vary across body regions but literature depicting this pattern is conflicting. Our study analyzes dystonia response to DBS by body distribution using the Burke-Fahn-Marsden Rating Scale motor (BFMRS-M) score and the Global Dystonia Rating Scale (GDRS).

We reviewed standardized videos of patients with isolated non-acquired dystonia obtained at baseline and post-DBS of unilateral or bilateral globus pallidus interna between 2008 and 2020. BFMRS-M and GDRS were scored using blinded assessment by two movement disorders neurologists. Mean baseline and post-DBS scores were compared using a paired t-test.

Ten male and 10 female patients were included, with average age at surgery 49 years. Post-DBS total BFMRS-M scores demonstrated improvement (20.5 ± 3.6 vs 11.9 ± 2.6) and there was significant improvement in neck sub-scores (4.9 ± 0.6 vs 2.5 ± 0.4). All patients demonstrated an improved total GDRS score post-DBS (21.6 ± 3.7 vs 11.1 ± 2.1), with significant improvements in GDRS sub-scores of the neck (5.9 ± 0.6 vs 2.6 ± 0.4) and shoulder & proximal arms (4.7 ± 1.1 vs 1.6 ± 0.5).

Efficacy of DBS varies by distribution of dystonia and should be considered in treatment planning discussions. GDRS is a more sensitive outcome measurement for dystonia compared to BFMRS-M and should be more routinely integrated into studying treatment response.

This study shows that pallidal deep brain stimulation yields differential improvement across dystonia body regions, with greatest benefit in the neck and proximal arms. These results highlight that the Global Dystonia Rating Scale is more sensitive to regional outcomes compared to the commonly utilized Burke-Fahn-Marsden Rating Scale.