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 3 years, 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.

Clinical significance of atrophy and white matter mean diffusivity within the thalamus of multiple sclerosis patients.

BACKGROUND: Gray-matter (GM) atrophy is strongly predictive of cognitive impairment in multiple sclerosis (MS) patients. The thalamus is the region where the atrophy/cognition correlation is most robust. However, few studies have assessed diffusion tensor imaging (DTI) metrics within the thalamus. OBJECTIVE: This study was designed to determine if thalamus white matter DTI predicts cognitive impairment after accounting for the effects of volume loss. METHODS: We enrolled 75 MS patients and 18 healthy controls undergoing 3T brain magnetic resonance imaging (MRI). Thalamus volumes were calculated on 3D T1 images. Voxelwise analyses of DTI metrics were performed within the thalamic white matter tracts. Neuropsychological (NP) testing, acquired using consensus standard methods, contributed measures of memory, cognitive processing speed and executive function. RESULTS: All cognitive tests were significantly predicted (R (2) =0.31, p<0.001) by thalamus volume after accounting for influence of demographics. Mean diffusivity was retained in regression models predicting all cognitive tests, adding from 7-13% of additional explained variance (p<0.02) after accounting for thalamus volume. CONCLUSIONS: We confirm the significant role of thalamus atrophy in MS-associated cognitive disorder, and further report that subtle thalamus pathology as detected by DTI adds incremental explained variance in predicting cognitive impairment.