Course and prognosis of chronic progressive multiple sclerosis. Results of an epidemiological study.

In studies on the natural course of multiple sclerosis (MS), several forms of the disease are distinguished. The most important are the relapsing remitting and the chronic progressive forms. The relationship between these remains unclear. In a prospective epidemiological survey we studied the course of MS using the year in which the chronic-progressive phase started as a landmark. The reliability of this "year of progression" was examined in an observer agreement study. Data were acquired from 342 patients. Progression of the handicap was most rapid in case of a secondary progressive course, female sex, high relapse rate in the preceding remitting phase and "year of progression" at a higher age. Survival after the "year of progression" was lowest in the secondary progressive group. Determining the "year of progression" seems to be significant for the prognosis.