Figure 1
Illustration of methods. (A) Example images from simultaneous stereo videography recording, with automated virtual markers applied by the DeepBehavior toolbox. Axes illustrated apply to both 3D kinematic and accelerometric analysis. Inset: Skeletal 3D reconstruction based on automated markers (B) Vectors connecting the L and R shoulders and L and R eyes were used to calculate the head rotation angle, relative to forward-facing. Tonic head position was then quantified as the average of the head rotation angle over the entire 20-second trial. (C) Tremor was quantified using the position of the face in 3D space over time (average of L eye, R eye, and nose marker positions). To remove drift and isolate oscillatory movement, face position was high-pass filtered (light gray line: unfiltered). Principal component analysis was applied to be agnostic to movement direction in identifying tremor cycles. Tremor frequency was obtained by deriving cycle length via an average of time between zero-crossings. The path-length (distance travelled) of one virtual marker during one cycle length (time) was used as a measure of tremor magnitude.
Figure 2
Bilateral Vim-DBS additively reduces phasic and tonic (posturing) components of cervical dystonia. A tremor “null-point” is suggested beyond the 40-degree rightward rotation. Plots depict average value over the duration of each trial and shading represents the standard deviation. (A) Accelerometry in the axis of greatest tremor amplitude demonstrates tremor reductions in all directions of head rotation from left Vim-DBS (orange, note missing data at 40R), right Vim-DBS (yellow, less effective), and bilateral Vim-DBS (purple). (B) Markerless-3D-kinematic analysis demonstrates similar findings. (C) Markerless-3D-kinematic analysis demonstrates improvement in tonic dystonia (posturing). With DBS OFF, the patient is unable to comply with requested head rotation and maintains a rightward rotation throughout all conditions. With bilateral Vim-DBS activation the patient has near-perfect control of head rotation (illustrated by the dotted line). Right and left Vim-DBS are each partially effective in facilitating head rotation.