MRI Hippocampal Microstructure and Episodic Memory in Early Multiple Sclerosis

Clinically isolated syndrome (CIS) can evolve into multiple sclerosis. In CIS patients, episodic memory is frequently impaired. Memory disorders could be preceded by microstructural abnormalities without visible atrophy in hippocampus. A recent MRI imaging of diffusion called NODDI (Neurite Orientation Dispersion and Density Imaging) can measure specifically microstructural abnormalities and map the axons in the white matter (WM) and dendrites in the grey matter (GM). The aim of this study is to evaluate microstructural abnormalities in the dentate gyrus of the hippocampus in CIS patients compared to controls.

Inclusion Criteria: * \- PATIENTS: * Men and Women, * Age 18-60 years, * Native French language, * Clinically isolated neurological syndrome (CIS) compatible with a demyelinating inflammatory episode within the central nervous system, potentially beginning multiple sclerosis (MS) whatever the mode of presentation, * Between 60 and 180 days from the onset, * At least two clinically silent lesions on their T2-weighted brain or spinal MRI scan with a size of least 3 mm, at least one of which being cerebral, ovoid, or periventricular, * Willing to participate and to sign informed consent. * \- HEALTHY CONTROLS * Men and Women, * Age 18-60years, * Native French language, * Willing to participate and to sign informed consent. Exclusion Criteria: * \- PATIENTS: * Prior documented neurological episode suggestive of MS, * History of neurological disease and/or other neurological diseases, * Psychiatric diseases, * Known chronic systemic diseases as judged by the investigator, * Alcohol or other addiction to toxic, * Disabling visual or motor problems preventing participation to neuropsychological assessments, * Acquisition disorders : Dyslexia, Dysphasia, Dyscalculia and dyspraxia, * Dosage change, stop or start of hypnotic or anxiolytic or antidepressive treatment less than 30 days, * Contra-indication to MRI (pacemakers, aneurysm clips, artificial heart valves, ear implants, metal fragments or foreign objects in the eyes, skin or body, claustrophobia), * Steroid treatment less than one month (be taken orally or by infusion) at the dosage of 500mg daily, * Illiteracy, is unable to count or to read, * Pregnant or breastfeeding women, * Patient concerned by articles L 1121-5 to L 1121-8 (persons deprived of their liberty by a judicial or administrative decision, minors, persons of legal age who are the object of a legal protection measure or unable to express their consent). * \- HEALTHY CONTROLS * History of neurological disease and/or neurological diseases, * Psychiatric diseases, * Known chronic systemic diseases as judged by the investigator, * Alcohol or other addiction to toxic, * Acquisition disorders: Dyslexia, Dysphasia, Dyscalculia and dyspraxia, * Known cognitive impairment or Prior neuropsychological testing with the same tests less than one year, * Hypnotic or anxiolytic or antidepressive treatment, * Steroid treatment less than one month (be taken orally or by infusion) at the dosage of 500mg daily, * Contra-indication to MRI (pacemakers, aneurysm clips, artificial heart valves, ear implants, metal fragments or foreign objects in the eyes, skin or body, claustrophobia) or refusing MRI, * Illiteracy, unable to count or to read, * Pregnant or breastfeeding women, * Patient concerned by articles L 1121-5 to L 1121-8 (persons deprived of their liberty by a judicial or administrative decision, minors, persons of legal age who are the object of a legal protection measure or unable to express their consent).