The significance of thalamic nuclei degeneration in relapsing-remitting and secondary progressive multiple sclerosis: results of neuropsychological and morphometry studies

Introduction.The thalamus is a 'transmitting organ' that is involved in a wide range of neurological functions. Its functional uniqueness and high sensitivity to damage during the earliest stages of multiple sclerosis (MS) make the thalamus a kind of barometer of diffuse brain damage in MS. Theaimof the study was to examine the structural and functional changes in the thalamus and its subregions using magnetic resonance morphometry and to determine their clinical significance in different types of MS. Materials and methods.We examined 68 patients with relapsing-remitting (n = 40) and secondary progressive (n = 28) MS. The control group consisted of 10 healthy people matched for age and gender. The Expanded Disability Status Scale (EDSS) and the Multiple Sclerosis Severity Score (MSSS) were used to assess the patients' neurological status. The cognitive and mental domains were tested using the MMSE, FAB, MoCA, SDMT, Beck's test, and HADS. All patients underwent a brain MRI and morphometric evaluation of the obtained data using the FreeSurfer 6.0 software. Results.The size of the thalamic pulvinar in relapsing-remitting MS was reduced on the left (M (anterior : posterior) = 186.6 : 149.4 mm3) compared with the controls (229.5 : 187.5 mm3) and on the right (219.5 : 187.1 mm3) compared with the controls (261.6 : 240.5 mm3; p 0.05). The size of the left thalamic nuclei was significantly reduced in secondary progressive MS when compared with relapsing-remitting MS and the controls. EDSS was correlated with a decrease in the dimensions of the geniculate nucleus on the left (r = 0.48) and the pulvinar nuclei on the left (r = 0.460.54). Standard neuropsychological scales correlated with the size of the medial dorsal nucleus (r (MMSE:FAB:MoCA) = 0.51; 0.45; 0.59). The greatest correlation was between the SDMT test (written section) and the left ventral anterior nucleus (r = 0.71). Conclusion.The obtained data indicate that thalamic nuclei atrophy plays a significant role in the progression of disability and cognitive disorders in MS. Mag- netic resonance morphometry of the thalamic nuclei can be considered an important marker and predictor of MS progression.