ABSTRACT
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Multiple sclerosis (MS) is the prototypic idiopathic inflammatory demyelinating disease (IIDD) of the central nervous system (CNS) (Table 20.1).1 The clinical manifestations, prognosis and pathological features vary, both amongst entities within the broad spectrum of demyelinating disease and amongst subtypes of MS.2 MS is usually classified based on the temporal course of disease; the most common form is characterized by an initial relapsing-remitting course that ultimately evolves into a progressive disease. A variety of neurological functions are affected during these relapses depending on the location of the lesion. During and between clinical relapses, magnetic resonance imaging reveals CNS white matter lesions of different stages, most evolving without symptoms. While relapses and new inflammatory lesions detected on MRI become less frequent, and even scarce over time, an insidious course of worsening neurological function ensues characterized by prominent progressive axonal loss (secondary-progressive MS). Progressive axonal dropout apparently begins at a very early stage, when the clinical disease is still regarded as relapsing remitting. About 15% of cases, despite occasional relapses, remain disability-free (benign MS). Some cases present with insidious neurological dysfunction, most commonly as a myelopathy from onset without any clinical symptoms of acute relapses (primary progressive MS).
