“A rose by any other name”: does defining extreme phenotypes add to the management of multiple sclerosis?

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system characterized by recurrent episodes of neurological dysfunction. Diagnostic criteria have evolved over time but the core principles of “dissemination in time” and “dissemination in space” have been retained. Different clinical phenotypes are recognized, such as the commonly encountered relapsing remitting and secondary progressive forms of the disease. Less commonly patients may present with a progressive course from onset.