Multiple Sclerosis Classification and Overview

The signs and symptoms of multiple sclerosis (MS) are the consequence of the underlying neuropathologic changes that occur in patients. The primary mechanism of injury is by inflammatory demyelination and, to a variable degree, axonal damage. Either mechanism may produce clinical features. The role of axonal damage is clear-cut, disrupting conduction completely. The progressive impairment or disability that occurs over time with MS results from one of two mechanisms. There is either stepwise worsening because of accumulated deficits from residua of exacerbations or gradual, inexorable progressive disease, independent of the exacerbations. The relative role of exacerbations and progressive disease in the accumulation of deficits has been debated, but the data is clear that both impact the long-term course of the illness. The diagnosis of MS is based on finding clinical evidence of lesions of the CNS, disseminated in time and space. The chapter further discusses clinical course patterns that can be divided into four subtypes: relapsing remitting, primary progressive, secondary progressive, and progressive relapsing.