The preceding chapters provide an overview of the pathology of MS and its relationship to experimental models (Chapter 2), on genetic disposition and immunological changes (Chapter 3), and on some epidemiological characteristics of the disease and its geographical distribution (Chapter 4). The following is an attempt to develop the basis of a modern concept of disease mechanism, and, in particular, of the pathogenesis of the plaques which are fundamental to it. It is unavoidable that some aspects are hypothetical, since the true cause of the disease is not known. Out of the mosaic of knowledge, a picture of pathogenesis is emerging based on the best proven facts.

GENERAL PATHOGENESIS

The prevalence of MS varies widely in relation to geographical location and the ethnic background of the population examined. As discussed in Chapter 4, there is an increase in the prevalence of MS with increasing geographical distance from the equator in Europe and Northern America. This is not a methodological artifact, but reflects a true biological characteristic of the disease. A similar North–South gradient is found in Japan, although the prevalence rates there are lower by a factor of 10 than those at similar geographical latitudes in Europe and Northern America.

In some ethnic groups, such as Bantu, Eskimos, Hungarian gypsies and Hutterites in the U.S., MS appears to be extremely rare; whereas in certain geographical areas such as the Faeroe Islands and West Finland, accumulations of cases are described.