Definition of responder: introduction

Availability of multiple disase modifiyng treatments in multiple sclerosis requires the definition of criteria to classify the response to individual treatments, to open the possibility to substitute a drug with another potentially effective drugs in case of treatment failure or to add a second treatment if the first is classified as partially effective. Because of the large inter and intra- individual variability of the disease evolution such a classification is frequently difficult. Different clinical and magnetic resonance imaging (MRI) parameters have been proposed. Measures of disease activity, attacks and active MRI lesions, are ore suitable, particularly in the remitting phase of the disease.