ABSTRACT
Ten per cent of patients with multiple sclerosis (MS) exhibit a progressive course from onset, with no history of relapse or remission; so called primary progressive MS (PPMS). Unlike patients with relapsing-remitting MS (RRMS) or secondary progressive MS (SPMS) the disability of patients with PPMS results solely from disease progression and not from the effect of relapses. Due to the relative rarity of this clinical subtype and its unique clinical course (which excludes the use of relapse rate to assess disease activity) these patients have largely been excluded from therapeutic trials. Their further evaluation could, however, teach us much about the underlying mechanisms of disability resulting from disease progression as distinct from the effect of relapses, which may in turn facilitate appropriate trial design.
