The natural history of primary progressive MS in British Columbia, Canada

Background: Primary progressive multiple sclerosis (PPMS) has a distinct clinical phenotype and has historically been understudied with few longitudinal natural history studies spanning a reasonable time period. The authors examined patient characteristics, disease progression, and associated risk factors in the PP population of British Columbia, Canada. Method: The authors report on the PP population from an upcoming publication of the natural history study of definite MS in British Columbia, Canada. The main outcome was sustained progression to Expanded Disability Status Scale (EDSS) 6, secondary outcome time to EDSS 8. Risk factors for progression included sex, onset age, onset symptoms, and for time to EDSS 8, time to EDSS 6. Results: Of the 2,837 patients with definite MS in the original study, 352 (12.4%) had PPMS. Mean disease duration was 17.2 years (0.3 to 49.6 years), mean onset age was 40.1 years (SD 11.5), and 53% (187) were female. One-quarter of the population had reached EDSS 6 after 7.3 years from onset, yet another 25% still did not require a cane after 25 years. Sex, onset age, and onset symptoms did not predict progression (p > 0.05). A shorter time to EDSS 6 predicted a shorter time to EDSS 8 (p < 0.0005). Discussion: Progression of disability was slower than found in previous primary progressive multiple sclerosis natural history studies. However, considerable variation existed, with few predictors, other than sooner to cane, sooner to wheelchair.