The primary pathological process in chronic lesions in multiple sclerosis (MS), even those described as “slowly expanding,” is likely to be tissue loss, a recent study found. Researchers measured volumes of individual lesions from 22 individuals on proton density magnetic resonance imaging acquired between 1992 and 2015. They found:

• There was sustained radiological contraction of MS lesions, a surprising result given that fresh myelin breakdown products within chronic active lesions are observed relatively frequently at autopsy.

• The mean (standard deviation) lesion volume at baseline was 142 (82) mL, falling to 74 (51) mL after 16 (3) years.

• All lesions shrank over time.

• Change in lesion volume did not correlate with change in supratentorial brain volume.

• In simulations, the results could be explained by a process of slow radial expansion superimposed on substantially more rapid resorption of damaged tissue.

Citation: Sethi V, Nair G, Absinta M, et al. Slowly eroding lesions in multiple sclerosis. [Published online ahead of print June 23, 2016]. Mult Scler. doi:10.1177/1352458516655403.