Objective: To assess the acute effect of combined ventrolateral thalamus (VL-Th) and subthalamic nucleus (STN) stimulation in Cervical Dystonia (CD) on clinical and kinematic measurements in a cross-sectional study design.

Background: Deep brain stimulation (DBS) of the VL-Th and STN is effective for treating CD and dystonic head tremor, respectively. We hypothesized that combined VL-Th/STN DBS might improve kinematic components of CD, including head turning performance and involuntary movements.

Method: Nine CD subjects were bilaterally implanted with an octopolar linear lead spanning from STN to VL-Th. They underwent clinical and kinematic assessment in two conditions: OFF STIM (with DBS turned off for 20 minutes) and ON STIM (with stimulation delivered according to subject’s best DBS settings). Time from operation to assessment was 16.9±7.9 months. TWSTRS was used to rate clinical severity. Head motion was captured from the forehead with an inertial measurement unit. Voluntary movements were recorded during right and left head turns. Involuntary movements were captured while attempting to hold a fixed neutral head position and in an unconstrained condition. Kinematic metrics were compared OFF and ON STIM.

Results: TWSTRS significantly decreased in the ON STIM compared to the OFF STIM condition. Voluntary head turning movements ON STIM had increased mean amplitude (p=0.004) and smoothness (p<0.001). 4/9 subjects showed improved peak angular velocity, but this did not reach significance at a group level. The ON STIM condition showed reduced range (p<0.001) and cumulative rotation (p<0.001) of involuntary movements. Spectral analysis of velocity data showed reduced power of involuntary movement ON STIM (p<0.001). Attenuation of several involuntary movement patterns was demonstrated, including high-amplitude drifts, rhythmic jerky oscillations and rhythmic sinusoidal oscillations.

Conclusion: Combined VL-Th/STN DBS improves smoothness and amplitude of voluntary head movements. Stimulation attenuates several distinct patterns, as well as the overall extent, of involuntary movement. Detectable kinematic improvements within a short time frame suggests rapid onset of treatment effect with stimulation of these targets. This study provides kinematic evidence that abnormal head turning and involuntary mobile components of CD can be successfully treated by dual targeting of the ventrolateral thalamus and the STN.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/rapid-onset-kinematic-effects-of-thalamic-subthalamic-dbs-in-cervical-dystonia/