Objective: To evaluate possible abnormalities (bradykinesia) of repetitive finger movements, including the sequence effect, using kinematic techniques in patients with ET.

Background: Essential tremor (ET) is a heterogeneous movement disorder. Recent studies suggest that bradykinesia may be part of the phenotypic spectrum of ET; however none of the previous studies investigated the sequence effect in this condition.

Method: Ninety patients with ET and 85 age- and gender-matched healthy controls were evaluated by standardized clinical scales and objective analysis of repetitive finger tapping using an optoelectronic motion analysis system. The kinematic analysis of repetitive finger tapping included  total number of movements, movement rhythm, amplitude (hypokinesia) and velocity (bradykinesia) as well as progressive amplitude and velocity reduction during movement repetition (sequence effect).

Results: A between-group analysis revealed lower velocity and impaired movement rhythm in patients with ET in comparison to healthy controls (both Ps < 0.05). A subsequent frequency analysis, showed a significant amplitude decrement (sequence effect) in a subgroup of 13 out of 90 in patients with ET in comparison to 3 out of 85 HC (14.4% vs. 3.52%, X2=0.01). Finally, we found no relationships between the movement parameters and tremor severity in ET.

Conclusion: The present study indicates that slowness of movement is a common feature of patients with ET. In addition a proportion of ET patients has amplitude decrement (sequence effect) during movement repetition, a phenomenon typically present in patients with Parkinson’s disease. The data support the notion that ET is a heterogeneous disorder. The results are relevant for a better understanding of ET pathophysiology.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/is-there-evidence-of-bradykinesia-in-patients-with-essential-tremor/