Objective: Extending our prior FMAS validation in Parkinson’s disease (PD), we utilized this tablet-based system to quantify finger movement profiles in Essential tremor (ET) patients during a visual-motor task, focusing on potential irregularities due to tremor.

Background: ET is a common movement disorder characterized by action tremor, often affecting fine motor tasks.

Method: We enrolled 302 ET patients (diagnosed per the Consensus Statement on Essential Tremor; mean age 47.3 ± 26.1 years; 158 men, 144 women) and 298 age-matched healthy controls (mean age 46.9 ± 25.8 years; 152 men, 146 women). Exclusion criteria included MMSE <24, visual/joint impairments, or confounding medications. FMAS recorded latency (stimulus onset to movement initiation) and movement time (MT; finger flight duration) over 30 trials using a central start button and five peripheral stimuli. First quartile (Q1) values were analyzed, with additional assessment of variability in MT to capture tremor effects. Assessments were performed off-medication, with correlations to Fahn-Tolosa-Marin Tremor Rating Scale (FTMTRS) scores.

Results: ET patients showed moderately prolonged MT (right: 412.6 ± 98.4 ms; left: 405.2 ± 102.7 ms) compared to controls (right: 326.8 ± 72.3 ms; left: 332.1 ± 76.5 ms; P<0.001), with slight latency increases (P<0.05) and heightened MT variability indicative of tremor. The latency/MT ratio was reduced in ET (right: 1.02 ± 0.23; left: 1.05 ± 0.25) versus controls (right: 1.28 ± 0.24; left: 1.26 ± 0.25; P<0.001). ROC analysis identified a right-side ratio cut-off of 1.12 (AUC=0.842) for differentiating ET from controls. Parameters correlated with FTMTRS scores (r=0.45–0.59, P<0.01) and disease duration (P<0.01), but not age in ET patients.

Conclusion: FMAS provides a portable, repeatable tool for objective assessment of movement irregularities in ET, highlighting tremor-related MT prolongation and variability. This may support differential diagnosis from PD and facilitate remote monitoring in tremor disorders.

References: Tang P, Hou C, Liu Y, et al. Quantitative assessment of finger movement profile in a visual-motor task based on a tablet computer: The application in parkinson’s disease[J]. J Parkinsons Dis,2019,9(4):811-819.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/tablet-based-quantitative-evaluation-of-finger-movement-in-essential-tremor-a-visual-motor-task-study/