Serial magnetic resonance imaging in children with postinfectious encephalitis

We analyzed follow-up magnetic resonance images (MRI) in eight children with clinical postinfectious encephalitis (PIE), and discussed their pathogeneses. Three categories of MRI findings were apparent: (1) multifocal lesions in the white matter with/without basal ganglia involvement consistent with acute disseminated encephalomyelitis (ADEM) (three patients); (2) single or multifocal lesions localized only in the gray matter (two patients); and (3) localized lesions in the brain stem, basal ganglia or cerebellum. Some lesions in the patients in Categories 1 and 2 migrated or were resolved quickly, sometimes within 10 days. Gadolinium caused linear or spotty enhancement in the patients in Category 2. These findings suggest that Categories 1 and 2 are a self-limiting allergic angiopathy without demyelination. In contrast, the lesions in the patients in Category 3 were fixed, and not resolved within 6 months (three patients). The pathogenesis of Category 3 is not known. All except one patient had no prednisolone (PSL) therapy, however; all lesions were resolved completely or markedly reduced in size, which indicates PSL therapy is not always necessary in patients with PIE.