Localized atrophy of the thalamus and slowed cognitive processing speed in MS patients

Background: Deep gray matter (DGM) atrophy is common in multiple sclerosis (MS), but no studies have investigated surface-based structure changes over time with respect to healthy controls (HCs). Moreover, the relationship between cognition and the spatio-temporal evolution of DGM atrophy is poorly understood. Objectives: To explore DGM structural differences between MS and HCs over time in relation to neuropsychological (NP) outcomes. Methods: The participants were 44 relapsing-remitting and 20 secondary progressive MS patients and 22 HCs. All were scanned using 3T magnetic resonance imaging (MRI) at baseline and 3-year follow-up. NP examination emphasized consensus standard tests of processing speed and memory. We performed both volumetric and shape analysis of DGM structures and assessed their relationships with cognition. Results: Compared to HCs, MS patients presented with significantly smaller DGM volumes. For the thalamus and caudate, differences in shape were mostly localized along the lateral ventricles. NP outcomes were related to both volume and shape of the DGM structures. Over 3years, decreased cognitive processing speed was related to localized atrophy on the anterior and superior surface of the left thalamus. Conclusions: These findings highlight the role of atrophy in the anterior nucleus of the thalamus and its relation to cognitive decline in MS.