Effects of Dimethyl Fumarate on Cognitive Performance and Brain Abnormalities in Multiple Sclerosis.

The goal of this observational study is to evaluate the slowing/reduction of cognitive dysfunction progression and to evaluate grey matter (GM) and thalamus structural changes in Relapsing-Remitting Multiple Sclerosis (RRMS) patients after 12 months of treatment with Dimethyl Fumarate (DMF). The main questions it aims to answer are: * Can DMF slow or reduce the progression of cognitive dysfunction in RRMS patients? * Can DMF slow the reduction of brain volume in RRMS patients? At baseline visit, RRMS patients undergo extensive neurological examination in which their disability is evaluated by using Expanded Disability Status Scale (EDSS). The efficacy assessments of this study are: 1. The Brief Repeatable Neuropsychological Battery (BRB); 2. Executive functions: Delis-Kaplan Function System (DKEFS) scale - Sorting Test. All RRMS patients undergo MRI: conventional MRI measures (T2-, T1-enhancing and T1-hypointense lesions), global brain atrophy, regional brain atrophy and Diffusion Tensor Imaging (DTI) (GM and thalamus) examinations. Six and 12 months after the baseline visit, the RRMS patients in treatment with DMF undergo the BRB, DKEFS and MRI/DTI study and neurological evaluation (EDSS).