Objective: We aimed to evaluate the bradykinesia features in ET by clinical examination and kinematic analysis of repetitive finger movements. We compared data collected in essential tremmor (ET) patients with those recorded in Parkinson’s disease patients and healthy controls.

Background: ET is a movement disorder primarily characterized by postural tremor of the upper limb. Although still under-investigated, bradykinesia may be part of the phenotypic spectrum of ET.

Method: Overall, 258 subjects participated in the study (90 ET patients, 84 Parkinson’s disease patients, and 84 healthy controls). Repetitive finger tapping was kinematically recorded using a motion analysis system. Movement velocity, amplitude and decrement (sequence effect) were measured. We first compared the three groups by one-way analysis of variance. We also performed a cluster analysis to better address the data variability observed in ET patients. Possible relationships between kinematic and clinical data were assessed in ET.

Results: ET patients were slower than healthy controls. Movement slowness in ET did not correlate with tremor severity. We also found that movement slowness in ET was not associated with sequence effect, which instead is a common feature in Parkinson’s disease. Cluster analysis showed that a proportion of ET patients may have movement abnormalities as those showed in Parkinson’s disease.

Conclusion: Movement slowness without sequence effect is a common feature in ET patients. The present findings are relevant when interpreted in the context of the new tremor classification system and in the pursuit of reaching a more accurate bradykinesia definition.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/kinematic-assessment-of-bradykinesia-in-essential-tremor-compared-to-parkinsons-disease-a-cluster-analysis/