Randomized Open-label Trial to Compare Efficacy and Tolerance of Corticosteroids and IVIg

Inclusion Criteria: * Man or woman between 18 and 80, Weight ≤ 100 kg, CIDP diagnosis: * stable or deteriorated state (no spontaneous improvement), * with the following features: * motor or sensory and motor deficits, and reduced or abolished tendon reflexes, * progressive or relapsing evolution, * global symmetric disability in more than one limb, * disease course installation over at least 2 months, * cerebrospinal fluid with ≤10/µL white blood cells and \> 0.5 g/L protein rate (non compulsory examination), * electrophysiological or histological signs of demyelinization, * INCAT disability score ≥ 2 in arms or ≥ 1 in legs Exclusion Criteria: * Severe electrophysiological axonal damage, * Pure motor syndrome, * Spontaneous improvement, * Associated systemic disease that could be the cause of neuropathy, * Severe cardiac insufficiency, * Cardiac arrhythmia, * Severe cardiopulmonary pathology, * Inflammatory syndrome, * Severe physical disease which can interfere with the trial, * Patient in a strict salt-free diet, * A clinically significant abnormal biological result, * Positive serology in one of the following tests: HIV1, HIV2, A-B-C hepatitis, Hbs antigen, Lyme disease, * IgA complete deficiency, * History of anaphylactic reaction during previous IVIg infusion, * Hypogammaglobulinemia (IgG \< 3g/L), * Creatinine clearance \< 80 mL/min, * Evolutive gastroduodenal ulcer, diabetes, serious infectious condition, evolutive virus disease (hepatite, herpes, varicella, zona), psychotic states not controlled by treatment, veinous or arterial thrombosis, non controlled high blood pressure, osteoporosis, * Patient previously treated by corticosteroids, IVIg, plasma exchanges or any other immunosuppressive agent within 3 months before inclusion, except for azathioprine and mycophenolate mofetil which were tolerated in the case of the dose being unmodified within 3 months and kept unchanged during the trial, * Experienced failure with a IVIG or prednisone prior treatment, * Hypersensitivity to any components of the 2 treatments, * Unsigned informed consent, * Ongoing or planned pregnancy (mandatory pregnancy test at the screening visit), breastfeeding, effective contraception for over 3 months for women of childbearing age.