Epub: Koch MW, Greenfield J, Javizian O, Deighton S, Wall W, Metz LM. The natural history of early versus late disability accumulation in primary progressive MS. J Neurol Neurosurg Psychiatry. 2014 Aug 4.
BACKGROUND: Primary progressive multiple sclerosis (PPMS) is the least common MS disease course and carries the worst prognosis. In relapsing-remitting multiple sclerosis (RRMS) disability accumulation occurs in two distinct phases, but it is unclear whether this is also true for PPMS. Here we investigate factors associated with early and late disability accumulation in PPMS.
METHODS: We investigated the influence of sex, age at disease onset and onset symptoms on time to, and age at, Expanded Disability Status Scale (EDSS) 4 and 6, as well as the time from EDSS 4 to 6 in PPMSers.
RESULTS: We identified 500 PPMSers. The analyses on time to EDSS 4 included 358 PPMSers, and those on time to EDSS 6 included 392 PPMSers. The median times to EDSS 4 and EDSS 6 were 5 and 9 years. The analyses on age at EDSS 4 included 360 PPMSers, and those on age at EDSS 6 included 402 PPMSers. The median ages at EDSS 4 and EDSS 6 were 51 and 55 years. Older age at onset and bilateral motor onset symptoms were independently associated with a shorter time to both EDSS 4 and EDSS 6. Sex and other onset symptoms were not associated with time to, or age at, landmark disability. Only age at onset was significantly associated with the time from EDSS 4 to EDSS 6.
CONCLUSIONS: Age at disease onset is the most important predictor of disability accumulation in PPMS. Bilateral motor onset symptoms were associated with quicker disease progression. In contrast to RRMS, we found no evidence for distinct phases of disability accumulation in PPMS. Disability accumulation in PPMS appears to be affected by the same factors throughout its course.