PLASMASEP

Treatment tested

• plasma exchange

Placebo or sham

• sham exchanges procedure

Other measures (4)

Inclusion Criteria: * Probable relapsing-remitting MS (RRMS) according to Polman et al criteria 2010. or clinically isolated neurological syndrome (CIS) compatible with a demyelinating inflammatory episode within the central nervous system, potentially beginning multiple sclerosis (MS). * Age 18-65 * EDSS before the current relapse \<6.5 * Acute relapse (optic neuritis, motor pyramidal relapse, cerebellar relapse, oculomotor relapse) since less than 2 months * Having been treated by IV or orally steroid (Methylprednisolone, 1g/d for at least 3 days), followed or not by oral tapering. * The current relapse inducing a significant clinical deterioration as compared to pre-relapse status and persisting 30 days after starting steroids. * Loss of visual acuity more than 30% on one ot both eyes; * Or: increase of 1 point pyramidal or brainstem functional system score (FSS) (if score ≥ 3) or cerebellar FSS (if score ≥ 2). * Or: reduced walking distance associated with an increase ≥ 0.5 point EDSS if EDSS ≥4.0; * Having signed informed consent. * affiliated to the French Social Security Exclusion Criteria: * Infection * Improving relapse. * Other disease interfering with evaluation. * Current treatment by immunosuppressive drug (as cyclophosphamide and mitoxantrone) or interrupted for less than 3 months. * Modification of DMT since less than 1 month. * Physical or psychic disease interfering with evaluation or consent. * Participation to another trial in the last 3 months. * Inability to establish peripheral central intravenous access; * Cerebral, autonomic, cardiac or other conditions with increased risk from hypovolemia * Pregnancy or breast-feeding. * Woman in age to procreate without effective contraception * Treatment by monoclonal antibody. * Progressive course of MS.

In more than 40 % of multiple sclerosis (MS) patients experiencing relapse, residual disability accumulates in spite of steroid treatment. Plasma exchanges are frequently used but there is no established evidence of their efficacy.