Objective: To investigate differences in brain glucose metabolism between patients with essential tremor and healthy controls using [18F]FDG PET brain imaging.

Background:

The pathophysiological mechanisms underlying essential tremor are not fully understood. Previous neuroimaging studies investigating essential tremor suggest that essential tremor arises from pathological oscillations within the cerebello-thalamo-cortical circuit. [1]

However, the origin of these pathological oscillations remains unclear. 

Prior FDG-PET studies are scarce and show inconsistent findings when comparing glucose metabolism between patients with essential tremor patients and healthy controls. [2,3]

Here, we compare essential tremor patients and healthy volunteers to get a better understanding of essential tremor pathophysiology.

Method:

[18F]FDG PET brain images were compared between 18 right-handed essential tremor patients (6 female, 12 male, aged 64.61±14.45) and 18 right-handed healthy controls (8 female, 10 male, aged 59.61±15.74) using a voxel-based mass univariate analysis. Age, the Montreal Cognitive Assessment (MoCA), the Hospital Anxiety and Depression scale (HADS) and the tremor severity score were used as covariates. Statistics are reported using an p<0.05, false discovery rate (FDR) corrected threshold.

Results: We found that essential tremor patients have significantly higher glucose metabolism in the right dentate nucleus, right anterior insula, left posterior putamen, and left motor cortex (p(fdr)<0.05). A significantly lower metabolism in essential tremor patients was detected in medial and lateral parietal regions (p(fdr)<0.05). The MoCA and HADS were not significantly different between groups.

Conclusion: Our findings show increased glucose metabolism in the areas involved in the cerebello-thalamo-cortical circuit, i.e. the dentate nucleus as well as the motor cortex. Abnormalities in the cerebellum, motor cortex and insula have been found in a previous study. [4] Furthermore, we found reduced metabolism in the parietal areas in ET patients compared to healthy controls. This finding is in line with previous work implicating the role of the parietal cortex in sensorimotor integration and its involvement in essential tremor pathology. [5]

References: [1] van der Stouwe, A. M. M., Nieuwhof, F., & Helmich, R. C. (2020). Tremor pathophysiology:
Lessons from neuroimaging. Current Opinion in Neurology, 33(4), 474–481.
https://doi.org/10.1097/WCO.0000000000000829

[2] Holtbernd, F., & Shah, N. J. (2021). Imaging the Pathophysiology of Essential Tremor—A
Systematic Review. In Frontiers in Neurology (Vol. 12).
https://doi.org/10.3389/fneur.2021.680254

[3] Timmers, E. R., Klamer, M. R., Marapin, R. S., Lammertsma, A. A., de Jong, B. M., Dierckx,
R. A. J. O., & Tijssen, M. A. J. (2023). [18F]FDG PET in conditions associated with hyperkinetic movement disorders and ataxia: a systematic review. In European Journal
of Nuclear Medicine and Molecular Imaging (Vol. 50, Issue 7).
https://doi.org/10.1007/s00259-023-06110-w

[4] Younger EFP, Ellis EG, Parsons N, Pantano P, Tommasin S, Caeyenberghs K, et al. Mapping essential tremor to a common brain network using functional connectivity analysis. Neurology. 2023;101(15). http://dx.doi.org/10.1212/wnl.0000000000207701

[5] Roy A, Coombes SA, Chung JW, Archer DB, Okun MS, Hess CW, et al. Cortical dynamics within and between parietal and motor cortex in essential tremor. Mov Disord [Internet]. 2019 ;34(1):95–104.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/changes-in-glucose-metabolism-in-essential-tremor-within-and-beyond-the-cerebello-thalamo-cortical-circuit/