Essential Tremor, the Cerebellum, and Motor Timing: Towards Integrating Them into One Complex Entity

Tremor and Other Hyperkinetic Movements

article

Martin Bareš¹  Ivica Husárová²  Ovidiu V. Lungu³ 

[1] Central European Institute of Technology, Behavioral and Social Neuroscience Research Group, Masaryk University;First Department of Neurology, Faculty of Medicine Masaryk University and St. Anne’s Teaching Hospital;Psychiatry Department, Université de Montréal;Functional Neuroimaging Unit, Research Center of the Geriatric Institute affiliated with the Université de Montréal;Research Department, Donald Berman Maimonides Geriatric Centre

关键词: Cerebellum;    essential tremor;    motor timing;    prediction;    neurodegeneration;   

DOI  :  10.5334/tohm.121

学科分类：社会科学、人文和艺术（综合）

来源: Ubiquity Press

【 摘 要 】

Essential tremor (ET) is the most common movement disorder in humans. It is characterized by a postural and kinetic tremor most commonly affecting the forearms and hands. Isolated head tremor has been found in 1–10% of patients, suggesting that ET may be a composite of several phenotypes. The exact pathophysiology of ET is still unknown. ET has been repeatedly shown as a disorder of mild cerebellar degeneration, particularly in postmortem studies. Clinical observations, electrophysiological, volumetric and functional imaging studies all reinforce the fact that the cerebellum is involved in the generation of ET. However, crucial debate exists as to whether ET is a neurodegenerative disease. Data suggesting that it is neurodegenerative include postmortem findings of pathological abnormalities in the brainstem and cerebellum, white matter changes on diffusion tensor imaging, and clinical studies demonstrating an association with cognitive and gait changes. There is also conflicting evidence against ET as a neurodegenerative disease: the improvement of gait abnormalities with ethanol administration, lack of gray matter volume loss on voxel-based morphometry, failure to confirm the prominent presence of Lewy bodies in the locus ceruleus, and other pathological findings. To clarify this issue, future research is needed to describe the mechanism of cellular changes in the ET brain and to understand the order in which they occur. The cerebellum has been shown to be involved in the timing of movement and sensation, acting as an internal timing system that provides the temporal representation of salient events spanning hundreds of milliseconds. It has been reported that cerebellar timing function is altered in patients with ET, showing an increased variability of rhythmic hand movements as well as diminished performance during predictive motor timing task. Based on current knowledge and observations, we argue that ET is essentially linked with cerebellar degeneration, or at least cerebellar dysfunction, together with disturbance of motor timing. We explain the context of our current understanding on this topic, highlighting possible clinical consequences for patients suffering from ET and future research directions.

【 授权许可】

CC BY