Damage in the Thalamocortical Tracts is Associated With Subsequent Thalamus Atrophy in Early Multiple Sclerosis.

Merlin M Weeda,Iman Brouwer,Ruth Schneider,Carsten Lukas,Frederik Barkhof,Barbara Bellenberg,Petra J W Pouwels,Aimee S R Westerveld,Hugo Vrenken,Ilanah J Pruis

doi:10.3389/fneur.2020.575611

Abstract

Background: In early multiple sclerosis (MS), thalamus atrophy and decreased integrity of the thalamocortical white matter (WM) tracts have been observed.Objective: To investigate the temporal association between thalamus volume and WM damage in the thalamocortical tract in subjects with early MS.Methods: At two time points, 72 subjects with early MS underwent T1, FLAIR and diffusion tensor imaging. Thalamocortical tracts were identified with probabilistic tractography using left and right thalamus as seed regions. Regression analysis was performed to identify predictors of annual percentage change in both thalamus volumes and integrity of the connected tracts.Results: Significant atrophy was seen in left and right thalamus (p < 0.001) over the follow-up period (13.7 ± 4.8 months), whereas fractional anisotropy (FA) and mean diffusivity (MD) changes of the left and right thalamus tracts were not significant, although large inter-subject variability was seen. Annual percentage change in left thalamus volume was significantly predicted by baseline FA of the left thalamus tracts F(1.71) = 4.284, p = 0.042; while no such relation was found for the right thalamus. Annual percentage change in FA or MD of the thalamus tracts was not predicted by thalamus volume or any of the demographic parameters.Conclusion: Over a short follow-up time, thalamus atrophy could be predicted by decreased integrity of the thalamic tracts, but changes in the integrity of the thalamic tracts could not be predicted by thalamus volume. This is the first study showing directionality in the association between thalamus atrophy and connected WM tract damage. These results need to be verified over longer follow-up periods.

Highlights

Multiple sclerosis (MS) is an autoimmune disorder affecting the central nervous system
MS is characterized by atrophy in the gray matter (GM) and widespread pathology in the white matter (WM), which can be investigated with diffusion tensor imaging (DTI)
None of the measures differed between subjects with CIS or RRMS, all analyses were performed in the entire cohort of subjects

Summary

Introduction

Multiple sclerosis (MS) is an autoimmune disorder affecting the central nervous system. The thalamus, a central structure in the brain that acts as a convergence location as well as a gateway to the cortex [3], has numerous reciprocal WM connections to the cortex and subcortical structures, referred to as the thalamocortical projections. These thalamocortical projections connect distinct thalamic nuclei to cortical areas, such as to the prefrontal and temporal cortex, to the posterior parietal cortex and to the somatosensory and motor/premotor cortices. In early multiple sclerosis (MS), thalamus atrophy and decreased integrity of the thalamocortical white matter (WM) tracts have been observed

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