Objective: To quantify the severity of tremor subtypes and bradykinesia in FXTAS and potentially identify preclinical symptoms in premutation carriers (PMC) without a diagnosis of FXTAS using an inertial sensor system.

Background: FXTAS is a neurodegenerative disorder characterized by tremor and cerebellar gait ataxia. It occurs in some carriers of a 55-200 CGG repeat size premutation in the fragile X mental retardation 1 gene. However, early predictors of FXTAS onset are needed and quantitative measurements of tremor and bradykinesia profiles and fine motor function may be useful in natural history studies, response to medications and as outcome measures in future clinical trials.

Method: 39 PMC with FXTAS, 20 PMC without FXTAS, and 27 healthy controls performed a series of upper extremity (UE) motor tasks while wearing an ETsense™ sensor/Kinesia system which quantifies several types of tremor and bradykinesia. Regression analyses controlling for age, sex and CGG repeat size with FXTAS diagnosis group as the main predictor was performed to detect potential group differences. The FXTAS Rating scale (FXTAS-RS) was administered to determine whether these clinician-rated scores correlate with severity scores from the Kinesia system.

Results: PMC with FXTAS had significantly worse postural and kinetic tremor compared to PMC without FXTAS (p=0.04; 0.03) and controls (p=0.001; 0.0001), respectively, and worse finger tap (p=0.0009), hand movement (p=0.0001) and rapid alternating movement speed (p=0.003) and amplitude (p=0.04) than controls. PMC without FXTAS had significantly worse finger tap (p=0.004), hand movement (p=0.01) and rapid alternating movement speed (p=0.003) and amplitude (p=0.02) than controls. All quantitative scores were significantly correlated with the FXTAS-RS scores (p=0.02 to < 0.0001) except for finger tap speed and amplitude.

Conclusion: The ETSense™ system is a feasible, portable and low-cost method for quantifying UE tremor and bradykinesia in FXTAS and may have potential in detecting preclinical symptoms of UE speed and coordination deficits in PMC without FXTAS. Further validation of these measures and the confirmation of preclinical disease identification in longitudinal studies with higher subject numbers are needed.

References: 1. Giuffrida, J.P., D.E. Riley, B.N. Maddux, and D.A. Heldman. 2009. Clinically deployable Kinesia technology for automated tremor assessment. Mov.Disord. 24:723-730. 2. Heldman, D.A., A.J. Espay, P.A. LeWitt, and J.P. Giuffrida. 2014. Clinician versus machine: reliability and responsiveness of motor endpoints in Parkinson’s disease. Parkinsonism Relat.Disord. 20:590-595.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/inertial-sensor-based-tremor-and-bradykinesia-quantification-and-potential-for-early-disease-identification-in-fragile-x-associated-tremor-ataxia-syndrome-fxtas/