Objective: To estimate whether Parkinson’s KinetiGraph (PKG) can be useful in quantifying tremor severity in patients with essential tremor (ET) before and after treatment with deep brain stimulation (DBS).

Background: ET is the most common movement disorder. Rating scales are well established but are dependent on observers’ perception. In recent years, technology-based objective measures have increased in clinical use. One of those is PKG, a useful and established tool to quantify symptoms such as tremor, bradykinesia and dyskinesia in patients with Parkinson’s disease. Programming modern DBS systems with segmented leads and numerous possibilities for current distribution is challenging and time consuming for the patient and the clinician. Wearable sensors can provide complementary data for monitoring response to DBS treatment.

Method: Sixty-eight patients with ET consecutively accepted for DBS surgery at a single center were studied during 2017-2021 and 45 (32 men and 13 women) had complete data sets. Segmented DBS electrodes were used in all cases, either unilateral or bilateral, with zona incerta as the target. Patients were examined before and approximately 6 months after the surgery with The ET Rating Assessment Scale (TETRAS) and with PKG. The PKG parameter Percent Time Tremor (PTT) was recorded, based on 6 days ambulatory monitoring from one wrist. Results were analysed by using Wilcoxon-signed ranks test and Spearman correlation analysis.

Results: Tremor was significantly reduced after DBS surgery, measured by TETRAS total scores, from 53.4±13.4 to 25.9±15.8 (p<0.0001). PKG-PTT was also significantly reduced, from 10.3±9.5 to 5.0±4.4 (p<0.0001). However, no correlations were seen between TETRAS and PKG values (Spearman r 0.08).

Conclusion: PKG detects tremor improvement in ET on a group level, but does not give additional value when evaluating tremor severity and treatment effect. The device was developed for Parkinson’s disease, so using PKG in ET is off-label, but encourages further studies on objective tremor assessments in ET.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/usability-of-parkinsons-kinetigraph-in-deep-brain-stimulation-for-essential-tremor/