Ma. Lee et al., Spatial mapping of T-2 and gadolinium-enhancing T-1 lesion volumes in multiple sclerosis: evidence for distinct mechanisms of lesion genesis?, BRAIN, 122, 1999, pp. 1261-1270
It is generally believed that most T-2-weighted (T-2) lesions in the centra
l white matter of patients with multiple sclerosis begin with a variable pe
riod of T-1-weighted (T-1) gadolinium (Gd) enhancement and that T1 Gd-enhan
cing and T-2 lesions represent stages of a single pathological process. Les
ion probability maps can be used to test this hypothesis by providing a qua
ntitative description of the spatial distribution of these two types of les
ions across a patient population. The simplest prediction of this hypothesi
s would be that the spatial distributions of T-1 Gd-enhancing and T-2 lesio
ns are identical. We generated T-1 Gd-enhancing and T-2 lesion probability
maps from 19 patients with relapsing-remitting multiple sclerosis, There wa
s a significantly higher probability (P = 0.001) for T-2 lesions to be foun
d in the central relative to the peripheral white matter (risk ratio 4.5),
although the relative distribution of T-1 Gd-enhancing lesions was not sign
ificantly different (P = 0.7) between central and peripheral white matter r
egions (risk ratio 0.6). Longitudinal data on the same population were used
to demonstrate a similar distribution asymmetry between new T-1 Gd-enhanci
ng and new T-2 lesions that developed over the course of 1 year. Alternativ
e hypotheses to explain this observation were tested. We found no spatial d
ifference in the likelihood of development of persistent T-2 lesions follow
ing T-1 Gd enhancement. The relative distribution of T-1 Gd-enhancing lesio
ns was shown to be independent of the dose of Gd contrast agent and the fre
quency of scanning. Our findings suggest that a proportion of the periventr
icular T-2 lesion volume may arise from mechanisms other than those associa
ted with early breakdown of the blood-brain barrier leading to T-1 Gd enhan
cement.