The Pathology of Rasmussen Syndrome: Stages of Cortical Involvement and Neuropathological Studies in 45 Hemispherectomies

Purpose: Rasmussen syndrome (RS) is a rare form of epilepsy characterized by progressive destruction of a single hemisphere. To characterize the profile of cortical involvement in RS, we studied the pathological changes in the cerebral cortex of 45 hemispherectomies performed at Johns Hopkins Hospital between 1985 and 2002. Methods: The patterns of pathologic changes and stages of cortical abnormalities were studied by histology and immunocy to chemistry methods. The burden of pathology (BP) was quantified in all brain regions of each of the 45 hemispheres. Results: Our study demonstrated significant heterogeneity in the stages of cortical pathology and the multifocal nature of the disease. These stages varied from early inflammation defined by infiltration of T lymphocytes and neuroglial reactions, to more severe stages with extensive neuronal cell death and cavitation of the cerebral cortex. A greater BP was significantly associated with an early age at onset (p = 0.01) and longer duration of disease (p ≤ 0.001). The BP was similar in all brain regions except the occipital lobe, where the BP was significantly lower (p = 0.032). Conclusions: The multifocal distribution of pathologic changes, as well as the heterogeneity in the stages of cortical damage in each patient, is consistent with an ongoing and progressive immune‐mediated process of neuronal damage that involves neuroglial and lymphocytic responses, resembling other autoimmune CNS disorders such as multiple sclerosis.