Diagnosis and staging of Rasmussen's encephalitis by serial MRI and histopathology.

Abstract

To correlate MRI and histopathologic findings in patients with Rasmussen's encephalitis (RE). MRI features of 10 patients with RE were studied on serial scans. In surgical specimens from these patients, densities of T lymphocytes, microglial cells and nodules, and reactive astrocytes were evaluated. Densities of T cells, microglial nodules, and astrocytes were inversely correlated to disease duration. MRI abnormalities had a focal onset and spread across one hemisphere. The following course of MRI abnormalities in a given brain region was observed: on very early scans, the cortex was swollen and showed a hyperintense T2/fluid-attenuated inversion recovery signal. Consecutively, progressive atrophy of the affected hemisphere occurred. Correlation of MRI features with quantitative histopathology revealed that there was a higher number of T cells and reactive astrocytes in the earlier MRI stages compared with the late (merely atrophic) stage. These data suggest a disease course in RE with the highest inflammatory intensity in the early stages and a subsequent decrease in inflammation. The MRI abnormalities and their characteristic sequence may help to identify patients with RE and to obtain informative biopsies.