Pathology of Progressive Multiple Sclerosis

Multiple sclerosis (MS) is a common inflammatory disease of the nervous system that generally starts in young adulthood and over time frequently leads to progressive functional deficits. A characteristic of this still puzzling disease is that its clinical manifestation changes as it progresses. Although during the early phases of the disorder, most patients mainly experience relapses, on average after 10 to 15 years, this episodic relapsing-remitting phase develops into a progressive phase characterized by steadily increasing disability [1]. Why this transition happens and why approx. 15 % of all patients enter this progressive phase without a preceding relapsing-remitting phase are questions which have yet to be answered completely. The importance of finding answers to these questions is pinpointed by the fact that although numerous medications are effective in treating relapsing-remitting MS, they remain partially or completely ineffective in the progressive stage of the disease. We will approach these questions by summarizing the major advances in the study of the pathology and pathogenesis of progressive MS, and then discuss which concepts and conclusions emerge from these findings.