Objective: To assess differences in cerebellar lobar volumes in Essential tremor and Parkinson’s disease patients and investigate the relation of lobar volumes with motor symptoms.

Background: The neurobiological basis of tremor in patients with Essential tremor (ET) may localize in part to the cerebellum and its pathways. Previous studies have described malfunctions in the cerebellum, specifically the dentate nucleus, and pathways through the red nucleus and inferior olive, as they may underlie the tremor etiology. Based on these networks, cerebellar changes may influence the motor scores such as the Washington Heights-Inwood Genetic Study of Essential Tremor (WHIGET) in ET individuals. In contrast, Parkinson’s disease (PD) related tremor may have a distinct or overlapping localization, involving the cerebellothalamocortical circuit1.

Method: A cohort of 348 patients diagnosed with ET (n=103) or PD (n=245) underwent T1-weighted Magnetic Resonance Imaging (MRI) under general anesthesia for deep brain stimulation surgical planning. Cerebellar segmentation of 28 lobules was performed using an automated multi-atlas lobar segmentation and individually reviewed for accuracy.  A simple linear regression model was used to assess differences in lobule volume between ET and PT patients while correcting for age and total intra-cranial volume and to investigate the relationship of motor scores with lobule volume. False discovery rate was controlled at 0.1 to correct for multiple comparisons.

Results: ET patients showed significant lower volumes in the deep cerebellar nuclei, caudal lobules (VIIIa and VIIIb), lower anterior lobules (III, IV, V), and vermis VIIIa (p<0.05). Additionally, worsening WHIGET scores were associated with lower volumes in lobule VIII (P<0.01).

Conclusion: ET patients appear to have greater levels of atrophy in cerebellar lobules than in PD individuals, supporting the hypothesis that the pathophysiology of ET is linked to regional cerebellar changes. Our findings are consistent with previous studies that indicate pathology in the dentate nucleus, as this is contained within the deep cerebellar nuclei. In addition, our findings support that specific lobules may influence the clinical phenotype in ET individuals.

References: 1. Helmich RC, Toni I, Deuschl G, Bloem BR. The Pathophysiology of Essential Tremor and Parkinson’s Tremor. Curr Neurol Neurosci Rep. 2013;13(9):378. doi:10.1007/s11910-013-0378-8

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cerebellar-structural-changes-in-patients-with-parkinsons-disease-and-essential-tremor/