Objective: This study investigates how motor and non-motor manifestations of essential tremor (ET) progress over time.

Background: ET is a common and heterogeneous movement disorder characterized by action tremor of upper limbs and other body parts and non-motor symptoms (e.g., cognitive, and psychiatric abnormalities). However, only a few studies have comprehensively attempted to estimate symptoms progression in ET.

Method: We enrolled 34 patients with ET. Each patient underwent the same evaluation at baseline (T0) and during a follow-up assessment (T1) (mean interval: 39 months). We assessed tremor and repetitive movements (finger tapping) using clinical rating scales and kinematic recordings; patients also underwent neuropsychological tests for cognitive assessment and structured interviews to investigate psychiatric disorders. We performed subgroup and regression analyses to investigate any predicting factors of clinical worsening.

Results: At follow-up, we observed higher Fahn-Tolosa-Marin Tremor Rating Scale (FTM-TRS) scores than baseline (20.04 ± 10.71 vs. 28.89 ± 12.88; P<0.01), with a higher percentage of patients with tremor in multiple body segments, e.g., upper limbs plus cranial districts or lower limbs (baseline: 41.18% vs. follow-up: 82.35%; P<0.01). Kinematic analyses, however, did not reveal amplitude and frequency changes of head or upper limbs tremor over time (all Ps>0.05). At follow-up, we also observed an increase in the number of patients with rest tremor (25.53% vs. 67.65%; P<0.01) and slower performance with reduced amplitude in finger tapping at kinematic analysis (velocity: baseline 980.4 ± 241 degrees/sec. vs. follow-up 825.8 ± 282.2 degrees/sec., P<0.01; amplitude: baseline 47.7 ± 10.6 degrees vs. follow-up 36.6 ± 16.1 degrees, P<0.01). The cognitive and psychiatric assessments showed that the prevalence of MCI, anxiety, and depression did not significantly increase at follow-up. Subgroup and correlation analysis individuated female sex, absence of familial history, and baseline head and rest tremor as possible predictive factors of higher worsening.

Conclusion: ET is a progressive disorder characterized by a tremor spread in multiple body segments over time and the emergence of soft signs, e.g., rest tremor and bradykinesia (movement slowness). Further investigation is needed to better identify possible predictive factors of ET progression over time.

References: Bhatia, Kailash P., Peter Bain, Nin Bajaj, Rodger J. Elble, Mark Hallett, Elan D. Louis, Jan Raethjen, et al. 2018. “Consensus Statement on the Classification of Tremors. from the Task Force on Tremor of the International Parkinson and Movement Disorder Society: IPMDS Task Force on Tremor Consensus Statement.” Movement Disorders 33 (1): 75–87. https://doi.org/10.1002/mds.27121.

Bologna, Matteo, Isabella Berardelli, Giulia Paparella, Gina Ferrazzano, Luca Angelini, Patrizia Giustini, Danilo Alunni-Fegatelli, and Alfredo Berardelli. 2019. “Tremor Distribution and the Variable Clinical Presentation of Essential Tremor.” Cerebellum (London, England) 18 (5): 866–72. https://doi.org/10.1007/s12311-019-01070-0.

Bologna, M., G. Paparella, D. Colella, A. Cannavacciuolo, L. Angelini, D. Alunni-Fegatelli, A. Guerra, and A. Berardelli. 2020. “Is There Evidence of Bradykinesia in Essential Tremor?” European Journal of Neurology, May. https://doi.org/10.1111/ene.14312.

Louis, Elan D., Martin Bares, Julian Benito-Leon, Stanley Fahn, Steven J. Frucht, Joseph Jankovic, William G. Ondo, Pramod K. Pal, and Eng-King Tan. 2020. “Essential Tremor-plus: A Controversial New Concept.” The Lancet. Neurology 19 (3): 266–70.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/longitudinal-study-of-clinical-and-neurophysiological-features-of-essential-tremor/