Objective: To study white matter (WM) abnormalities and global cortical atrophy in isolated rapid eye movement sleep behavior disorder (IRBD) patients and its relation to cognitive impairment.

Background: IRBD has been increasingly recognized as a prodromal phase of the synucleinopathies. Therefore, there is a growing interest in describing neuroimaging and cognitive biomarkers of brain neurodegeneration in this prodromal disorder.

Method: Twenty-two IRBD patients and 29 healthy controls (HC) were evaluated using diffusion-weighted and T1-weighted MRI on a 3T scanner. Voxelwise statistical analysis of the FA, MD and RD data was carried out using Tract-Based Spatial Statistics¹(TBSS) and FSL’s randomise². FreeSurfer was used to estimate mean cortical thickness as a measure of global atrophy³. A comprehensive neuropsychological battery was used to measure cognitive performance at the time of nueroimaging. Correlations between mean diffusivity measures, global cortical atrophy and cognitive tests were computed.

Results: Compared with HC, IRBD patients showed impairment in verbal learning, executive and visuoperceptive functions as well as in processing speed. TBSS showed widespread reductions of FA and increased RD in IRBD patients (p<.05 TFCE). Mean FA values positively correlated with Stroop Color test (r=.511; p=.021) and Symbol Digit Modalities Test (r=.529; p=.016) in the IRBD group but not in HC. No correlation was detected between mean RD or global cortical atrophy and any cognitive test.

Conclusion: These findings confirm previous results of cognitive impairment, global cortical atrophy and WM abnormalities in IRBD⁴. We found that reduced WM integrity is associated with low performance in tests involving processing speed.

References: [1] S.M. Smith, M. Jenkinson, H. Johansen-Berg, D. Rueckert, T.E. Nichols, C.E. Mackay, K.E. Watkins, O. Ciccarelli, M.Z. Cader, P.M. Matthews, and T.E.J. Behrens. Tract-based spatial statistics: Voxelwise analysis of multi-subject diffusion data. NeuroImage, 31:1487-1505, 2006. [2] Winkler AM, Ridgway GR, Webster MA, Smith SM, Nichols TE. Permutation inference for the general linear model. NeuroImage, 2014;92:381-397. [3] Dale, A.M., Fischl, B., Sereno, M.I., 1999. Cortical surface-based analysis. I. Segmentation and surface reconstruction. Neuroimage 9, 179-194 [4] B. Högl B, A. Stefani, A. Videnovic. Idiopathic REM sleep behaviour disorder and neurodegeneration – An update. Nat Rev Neurol, 14:40–56, 2018. doi:10.1038/nrneurol.2017.157

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MDS Abstracts - https://www.mdsabstracts.org/abstract/white-matter-abnormalities-and-its-relation-to-cognitive-impairment-in-isolated-rapid-eye-movement-sleep-behavior-disorder/