ABSTRACT
The past decade has witnessed substantial progress in our understanding of the pathogenesis of multiple sclerosis (MS), improvement in our ability to diagnose the disease and monitor its course, and the emergence of MS as a treatable neurologic disease. Nevertheless, the development of effective treatments for MS has been impeded by several characteristics of the disease. The purpose of this chapter is to discuss the aspects of MS that have an impact on the design of clinical trials, the development of new disease therapies, and patient care. These aspects include heterogeneity in disease course, in severity, and in manifestations; the presence of subclinical disease activity early in the disease; and the complexity of pathogenic mechanisms.
