Objective: This study focuses on translating parkinsonian tremor tests to an objective method to rate tremor severity using 3D accelerometry, that can be used during neurosurgery.

Background: The current gold standard for evaluating tremor in Parkinson’s Disease (PD) is the internationally standardized Movement Disorder Society – Unified PD Rating Scale (MDS-UPDRS). However, the MDS-UPDRS is associated with limitations, such as its inherent subjectivity and reliance on experienced raters. Objective motor measurements using accelerometry may overcome the shortcomings of visually scored scales. Therefore, the current study focuses on translating the MDS-UPDRS tremor tests into an objective scoring method using 3D accelerometry. An algorithm to measure and classify tremor according to MDS-UPDRS criteria is proposed.

Method: To illustrate the use of this method, 28 PD patients undergoing awake neurosurgical treatment and 26 healthy control subjects were included. Both groups underwent MDS-UPDRS tests to rate tremor severity, while accelerometric measurements were performed at the index fingers. All measurements were performed in off-medication state (at least 12 hours medication washout). Quantitative measures were calculated from the 3D acceleration data, such as tremor amplitude and area under the curve of power in the 4-6Hz frequency range. Accelerometric data of the healthy group were used to calculate the natural variation of noise between 4-6Hz, and to calculate thresholds for the scoring algorithm. Agreement between clinical MDS-UPDRS tremor scores and objective accelerometric scores was investigated.

Results: The trends were consistent with the logarithmic relationship between tremor amplitude and MDS-UPDRS score reported in previous studies. The accelerometric scores showed a substantial agreement (>69.6%) with the MDS-UPDRS ratings. However, accelerometric kinetic tremor measures poorly associated with the given MDS-UPDRS scores (R²<0.3), mainly due to the noise between 4-6Hz found in the healthy controls.

Conclusion: This study shows that MDS-UPDRS tremor tests can be translated to objective accelerometric measurements, applicable during neurosurgery. However, discrepancies were found between accelerometric kinetic tremor measures and MDS-UPDRS ratings. This technology has the potential to reduce rater dependency of MDS-UPDRS measurements and allows for a more objective method for intraoperative monitoring of tremor.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/intraoperative-quantification-of-mds-updrs-tremor-measurements-using-3d-accelerometry/