Objective: Describe the time course of clinical response to bilateral globus pallidus internus (GPi) deep brain stimulation (DBS) in a patient with myoclonus-dystonia syndrome (M-D), and explore intra-operative local field potentials (LFP) of the GPi with correlation to upper limb electromyography (EMG).

Background: M-D is a rare, autosomal dominant genetic condition that presents early in childhood with hyperkinetic movements, including myoclonus in the majority of patients and dystonia in up to half. DBS of the GPi and ventral intermediate thalamus (VIM) have both been successful in attenuating motor symptoms in a number of patients, but the time course for clinical improvement has not been well described. Additionally, there are rare reports demonstrating significant coherence between LFPs in the GPi and EMG.

Method: A 17-year-old girl with genetically-confirmed M-D underwent staged bilateral GPi DBS. Standardized clinical assessments were performed pre-operatively and three months post-operatively to evaluate symptomatic improvement. We recorded intraoperative LFPs from the dorsal, central, and ventral GPi, as well as EMG from select upper limb muscles while performing the following activities: 1) resting the arm, 2) extension of arm against gravity, 3) extension of arm with a one-pound weight attached to the wrist, and 4) maintaining a grip task at 25% of MVC. These tasks were repeated three months post-operatively after optimizing DBS programming.

Results: On pre-operative examination, the patient had frequent myoclonus of the proximal upper extremities, torso, and face, which worsened with startle. She had marked dystonia, with frequent plantarflexion and inversion of the left foot, and flexion at the bilateral wrists. She underwent surgery without complication. Forty-eight hours after initial programming, she noted almost complete resolution of dystonia, though only a 25% improvement in myoclonus, predominately distal. This bnefit was sustained at three months. Coherence analysis is underway.

Conclusion: In a young patient with M-D who underwent bilateral GPi DBS, we describe early and near complete resolution of dystonia, with less improvement in myoclonus. Previous case reports have described excellent long-term symptom control, but none have commented on similar short-term effects.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/rapid-improvement-in-dystonia-after-pallidal-deep-brain-stimulation-in-a-patient-with-myoclonus-dystonia-syndrome-a-case-report/