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This team of researchers observes that formation of lesions in MS shows pronounced short-term fluctuation of MR imaging hyperintensity and size. This, they say, is a qualitatively known, but poorly characterised phenomenon.
With the use of time-series of MR imaging intensity, they related the short-term dynamics of new lesion formation to those of the markers of long-term progression of the disease.
They analysed 915 examinations from weekly to monthly MR imaging in 40 patients with MS using a time-series model. Patterns of activity, duration, and residual hyperintensity within new lesions were measured and evaluated for relationships to disability, atrophy, and clinical phenotype in long-term follow-up.
Significant T2 activity was observed for 8 to 10 weeks, which suggests that T2 MR imaging is sensitive to non-inflammatory processes such as degeneration and repair. Larger lesions showed longer subacute phases, but disproportionally more recovery.
Patients with smaller average peak lesion size showed trends toward greater disability and proportional residual damage. Higher rates of disability or atrophy were associated with subjects whose lesions showed greater residual hyperintensity.
They concluded that smaller lesions appeared disproportionally more damaging than larger lesions, with lesions in progressive MS smaller and of shorter activity than in relapsing-remitting MS.
Associations of lesion dynamics with rates of atrophy and disability and clinical subtype suggest that changes in lesion dynamics may represent a shift from inflammatory toward degenerative disease activity and greater proximity to a progressive stage, possibly allowing staging of the progression of MS earlier, before atrophy or disability develops.
Reference: Meier, D., Weiner, H. and Guttman, C. (2007) MR Imaging Intensity Modeling of Damage and Repair In Multiple Sclerosis: Relationship of Short-Term Lesion Recovery to Progression and Disability. American Journal of Neuroradiology 28:1956-1963, November-December 2007
Source full text of article: http://www.ajnr.org/cgi/content/abstract/28/10/1956