The purpose of this study is to determine if memantine is effective in the treatment on cognitive disorders of Relapsing - Remitting multiple sclerosis. m

Inclusion Criteria:

• Remitting Multiple Sclerosis defined by Mc Donald et al., 2001
• Patient with authorised immunomodulator treatment or oral immunosuppressive therapy during more than three months: Bétâ Interferon, glatiramer acetate, azathioprine, methotrexate, mycophenolate mofetil, treatment by monoclonal antibody I.V. or anti-VLA4, natalizumab (Tysabri)
• Patient having benefited, possibly, of following treatments : mitoxantrone, cyclophosphamide, cyclosporine, general-purpose immunoglobulins, only if the treatment is ended more of 6 months before the inclusion.
• EDSS score ≤ 5.5
• DRS score ≥ 130
• PASAT 3s score > 15 and < median / control subjects according to 2 age brackets, sex, school level.
• Signed the informed consent form.
• Effective contraception for women in age to procreate

Exclusion Criteria:

• Progressive form MS
• MS relapse of less of 4 weeks.
• IV or oral corticoid treatment in the month preceding the screening
• Medicinal treatments or non medicinal in cognitive or psychology-stimulant aim in the 3 months before the screening
• Tumoral form MS visible in the MRI.
• Depressive syndrome (MADRS score > 19).
• Quite other diagnosed psychiatric pathology
• Known allergy or quite contraindication in memantin : renal or hepatic insufficiency, turned out epileptic disease, treatment by ketamine, amantadin, dextromethorphan, L-Dopa, dopaminergic agonist, barbituric, neuroleptic, 3,4-diaminopyridine, lithium, cimetidine, ranitidine, procainamide, quinine, nicotine, hydrochlorthiazide and ally, phenytoin, modafinil.
• Recent treatment (less of 4 weeks) by antidepressants and/or anxiolytics.
• Pregnancy or feeding.
• Minor or Major "protected by the law" patient
• Uncontrolled diet.
• Patient having benefited of one psychometric assessment(including in particular tests planned in the protocol) since less of one year.