Objective: To provide improved understanding of the relationship between postural and kinetic tremor presentation with deep brain stimulation (DBS) in Essential Tremor (ET).

Background: ET commonly presents with both postural and kinetic tremors, with most patients being kinetic tremor dominant [1]. DBS targeting the cerebello-receiving area of motor thalamus is an effective therapy for ET; however, the impact of stimulation on both action tremor subtypes has not been quantified.

Method: Ten subjects (4 female/6 male) with medication-refractory ET were implanted with directional DBS lead(s) (7 bilateral/3 unilateral, 17 leads) and enrolled in a prospective clinical trial investigating programming of DBS systems for ET (NCT03984643). Accelerometer data was collected from a wireless IMU sensor attached to the dorsal surface of each subject’s middle finger contralateral to the tested DBS lead. In the off-stimulation condition, unilateral clinician-optimized DBS setting, and at 10 monopolar review configurations, subjects performed tasks (rated 0-4 on the TETRAS scale) intended to elicit postural tremor (forward arms outstretched, lateral wing-beating, dot approximation) and kinetic tremor (finger-to-nose, Archimedes spiral, handwriting).

Results: At baseline, upper extremity postural tremor scores were significantly lower than kinetic tremor scores for both clinical rating scales (TETRAS, p<0.001) and mean IMU amplitude (p<0.02). Kinetic tremor amounts were positively correlated with postural tremor (R²=0.69, p<0.01). At clinician-optimized DBS settings, postural tremor exhibited greater tremor suppression (-67.6%) compared to kinetic tremor (-39.3%) (p<0.05). Across the DBS lead, 73.4% of configurations tested (N=222) scored higher in kinetic tremor compared to postural. Task-based correlation analysis of tremor suppression by DBS showed strong relationships between outstretched and wing-beating postures (R²=0.66, p<0.01) and dot approximation and finger-to-nose (R²=0.69, p<0.01) tasks across all configurations.

Conclusion: While ET often presents with greater kinetic than postural tremor, this study suggests that kinetic tremor is more difficult to suppress with DBS. Moreover, DBS configurations can affect postural and kinetic tremor differently. Future work will assess the neural pathways responsible for the suppression of specific postural and kinetic tremors.

References: [1] Louis ED. The Primary Type of Tremor in Essential Tremor is Kinetic Rather than Postural: Cross-Sectional Observation of Tremor Phenomenology in 369 Cases. Eur J Neurol. 2013 Apr; 20(4):725-7.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/relationship-between-postural-and-kinetic-tremor-control-with-vim-dbs-in-essential-tremor/