Abstract
Background:Deep Brain Stimulation (DBS) for dystonia is usually targeted to the globus pallidus internus (GPi), though stimulation of the ventral-intermediate nucleus of the thalamus (Vim) can be an effective treatment for phasic components of dystonia including tremor. We report on a patient who developed a syndrome of bilateral upper limb postural and action tremor and progressive cervical dystonia with both phasic and tonic components which were responsive to Vim DBS. We characterize and quantify this effect using markerless-3D-kinematics combined with accelerometry.Methods:Stereo videography was used to record our subject in 3D. The DeepBehavior toolbox was applied to obtain timeseries of joint position for kinematic analysis [1]. Accelerometry was performed simultaneously for comparison with prior literature.Results:Bilateral Vim DBS improved both dystonic tremor magnitude and tonic posturing. DBS of the hemisphere contralateral to the direction of dystonic head rotation (left Vim) had greater efficacy. Assessment of tremor magnitude by 3D-kinematics was concordant with accelerometry and was able to quantify tonic dystonic posturing.Discussion:In this case, Vim DBS treated both cervical dystonic tremor and dystonic posturing. Markerless-3D-kinematics should be further studied as a method of quantifying and characterizing tremor and dystonia.
Highlights
Essential tremor (ET) is one of the most common movement disorders, with an overall population prevalence of approximately one percent [2]
Using a protractorgoniometer as a guide, the patient was instructed to rotate his head to specific angles. 20 seconds of simultaneous accelerometry and markerless-3Dkinematics were obtained at each position. 3D-kinematics data was obtained with a stereo video recording system at 170 frames per second as previously described [1]
Bilateral ventral-intermediate nucleus of the thalamus (Vim) Deep Brain Stimulation (DBS) reduced the amplitude of dystonic head tremor as measured by accelerometry (amplitude: DBS OFF: 16.3 SD = 11.8; DBS Right: 9.5 SD = 5.1; DBS Left 2.9 SD = 1.4; DBS Bilateral 0.7 SD = 0.9) (Figure 2b) and markerless-3D-kinematics (DBS OFF: 17.0 SD = 6.8; DBS Right: 11.0 SD = 3.6; DBS Left 2.8 SD = 0.7; DBS Bilateral 1.0 SD = 1.0) (Figure 2b)
Summary
Essential tremor (ET) is one of the most common movement disorders, with an overall population prevalence of approximately one percent [2]. DBS of the globus pallidus internus (GPi) is a well-established and effective treatment for dystonia. Accelerometry is a well-established method of characterizing and quantifying tremor and has been used to differentiate oscillatory and irregular components of phasic dystonic movements [7]. Kinematics has the added advantage of directly measuring joint position to quantify tonic dystonic movements (posturing). Deep Brain Stimulation (DBS) for dystonia is usually targeted to the globus pallidus internus (GPi), though stimulation of the ventral-intermediate nucleus of the thalamus (Vim) can be an effective treatment for phasic components of dystonia including tremor. We report on a patient who developed a syndrome of bilateral upper limb postural and action tremor and progressive cervical dystonia with both phasic and tonic components which were responsive to Vim DBS. We characterize and quantify this effect using markerless-3D-kinematics combined with accelerometry
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