Objective: To (1) report a case of cervical dystonia resulting from ventral intermediate nucleus (Vim) thalamic deep brain stimulation (DBS) surgery, which was then responsive to stimulation; (2) analyze and quantify the effect of unilateral and bilateral stimulation on fixed dystonic posture and dystonic tremor.

Background: Vim-DBS is an effective treatment for medically refractory essential tremor (ET). Typical side effects include dysarthria and gait impairment but not dystonia. The standard DBS target for treatment of dystonia is the globus pallidus internus. Vim-DBS may also be an effective treatment for dystonic tremor, but has not been shown to significantly improve fixed dystonic posture [1].

Method: Multi-direction videography was used to record our subject in 3D. The DeepBehavior toolbox [2] was applied to analyze joint position and kinematics. Accelerometry data was simultaneously recorded by an iPhone (Apple Inc.) affixed to the subject, running the “Vibration” application (Diffraction Limited Design LLC).

Results: A 56 year old right-handed man with a 30 year history of ET (characterized by a regular and oscillatory action tremor isolated to the upper extremities) without dystonic features or head tremor was seen at our center. Six years prior, after failing medical therapy, he had undergone implantation of left Vim-DBS. This was complicated by the development of delayed post-operative cervical dystonia with rightward tilt/rotation and dystonic tremor, along with dysarthria. Five years later he underwent implantation of right Vim-DBS, further worsening his dystonia. Stimulation parameters were optimized for treatment of both ET and dystonia with good efficacy, though he also benefited from adjunctive botulinum toxin injection. Vim stimulation improved both dystonic tremor and fixed dystonic posture. Data from 3D joint position/kinematic analysis, and accelerometry demonstrated an additive contribution from bilateral Vim stimulation, with larger effect size from the left Vim than the right.

Conclusion: Placement of Vim-DBS can cause focal dystonia. In this case, Vim stimulation treated both dystonic cervical tremor and fixed dystonic posture. Bilateral stimulation had an additive therapeutic effect, though stimulation of the contralateral (left) Vim appeared to provide more contribution to overall efficacy.

References: [1] Deep brain stimulation for the treatment of uncommon tremor syndromes. Ramirez-Zamora A, Okun MS. Expert Review of Neurotherapeutics. 2016. 16 (8): 983-997. [2] DeepBehavior: a deep learning toolbox for automated analysis of animal and human behavior imaging data. Arac A, Zhao P, Dobkin BH, Carmichael ST, Golshani P. Frontiers in Systems Neuroscience. 2019. 13 (20).

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-case-of-cervical-dystonia-resulting-from-vim-dbs-surgery-that-was-then-responsive-to-stimulation-quantitative-analysis-of-therapeutic-effect-on-both-fixed-dystonic-posture-and-dystonic-tremor/