Neuropathological spectrum of Rasmussen encephalitis

Background: Rasmussen encephalitis (RE) is a chronic epileptic disorder of unknown etiology, and is clinically characterized by progressive neurological deterioration, focal seizures often progressing to intractable epilepsy, cognitive decline and hemispheric atrophy. Aims: We report the spectrum of neuropathological changes seen in RE, and discuss the evolutionary mechanisms of this disease. Materials and Methods: Surgically obtained specimens from RE patients diagnosed during 2002-2004 at this institute were evaluated for the presence and extent of different histopathological features of RE. The H&E and immunohistochemistry stained slides were also evaluated for the type and distribution pattern of inflammatory infiltrates, along with a semiquantitative evaluation for the severity of inflammation. Results: Four cases of RE were admitted during the study period, all of which presented with partial seizures with successive deterioration to intractable epilepsy. The age at onset varied between 5 and 10 years (mean 7.8 years), with three male and one female patients. Subsequently, all four patients underwent hemispherotomy. Histopathological features of perivascular lymphocytic infiltrate, neuronal loss, microglial nodules, and reactive astrocytosis, with or without evidence of neuronophagia confirmed a diagnosis of RE. These cases also had varying degrees of T-cell-rich (CD3-positive) inflammatory infiltrates and CD68-immunopositive microglial proliferation. It was observed that the severity of inflammation had a trend to inversely correlate with the duration of symptoms. Conclusion: It is proposed that an accurate evaluation and histopathological grading of these lesions may possibly have a role in patient prognostication