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

Objective: To correlate MRI and histopathologic findings in patients with Rasmussen's encephalitis (RE). Patients and methods: 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. Results: 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. Conclusion: 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.