Dynamics of MRI lesion development in an animal model of viral-induced acute progressive CNS demyelination.

Theiler's murine encephalitis virus (TMEV) infection in mice is an established model of CNS demyelinating diseases. The aim of the study was to determine the chronological pattern of lesion development in this model of monophasic fulminant demyelinating disease. We followed six highly susceptible interferon-gamma receptor knockout mice with serial in vivo brain magnetic resonance imaging (MRI) studies to determine changes in overall T2 lesion load and gadolinium enhancement. Altogether, 163 individual lesions were followed over 52 days. The number of lesions increased linearly with time. Four chronological patterns of lesion development were seen: (a) expanding lesions (48.5% of all lesions, 54.05% volume contribution); (b) expanding-retracting lesions (20.85% of all lesions, 15.03% volume contribution); (c) fluctuating lesions (16.6% of all lesions, 28.8% volume contribution); (d) stable lesions (14.05% of all lesions, 2.12% volume contribution). Gadolinium enhancement was not seen in the evolution of every lesion. Enhancement was both time- and lesion type-dependent. Early in the disease course (<43 days after infection), enhancement was almost always seen, later on (>43 days after infection) it was only seen in 8% of new lesions. All of fluctuating, 85.3% of expanding, 83.5% of expanding-retracting, and 56.5% of stable lesions were associated with gadolinium enhancement. We conclude that the MRI features of TMEV-induced demyelination in this model showed four unique chronological patterns, and inconsistent gadolinium enhancement. These novel findings may provide new insights into the pathogenesis of acute fulminant multiple sclerosis (MS).