Thalamic Structural Connectivity Alterations in Essential Tremor Associated with REM Sleep Behaviour Disorder
Elisa Bortolin1, Salvatore Mazzeo2, Camilla Calomino3, Rita Nisticò3, Giulia Bruschi1, Maria Vittoria Corbari1, Andrea Quattrone3, Aldo Quattrone3, Fabiana Novellino3, Massimo Filippi4, Maria Salsone1
1Vita-Salute San Raffaele University, 2Policlinico San Donato S.p.A., 3Magna Grecia University, 4Ospedale San Raffaele, Neuroimaging Research Unit
Objective:
We aimed at investigating investigated thalamic regions in Essential Tremor (ET) patients with and without REM sleep behavior disorder (RBD), using a graph theoretical analysis.
Background:
RBD is a rare REM-parasomnia, now considered a non-motor symptom of ET. Distinct structural alterations in the thalamus, as a key region modulating REM sleep, have been reported in patients with idiopathic and Parkinson’s disease-related forms. 
Design/Methods:

MRI data were acquired from 96 participants (41 ET, 10 ET with polysomnographic-confirmed RBD, ET-RBD, 45 controls). T1-weighted scans were obtained, and grey matter volumes were estimated across 28 thalamic regions of the AAL3 template (Cat12 toolbox). An adjacency matrix for each group was calculated using Pearson correlation. Group-specific matrices were extracted and nodal measures such as centrality measures and clustering coefficient were calculated. Differences between ET groups were computed using a set of 10000 random networks.

Results:

Among analyzed thalamic regions, ET-RBD patients showed increased local strength and weighted clustering coefficient in Geniculate Body and increased Betweenness centrality in Right Pulvinar Inferior Nucleus (p=0.05 FDR-corrected). Moreover, ET-RBD patients showed an increased strength and weighted clustering coefficient in Left Lateral Geniculate Body and Right Medial Geniculate Body, compared to controls (p=0.05 FDR-corrected).

Conclusions:

Our study demonstrates, for the first time, that the presence of RBD in ET is associated with an altered structural connectivity in thalamic regions. Our findings support the pathophysiologic role of the thalamus in the complex circuit causing RBD, in this particular ET phenotype.

10.1212/WNL.0000000000216402
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