Abstracts

Rationale: Rasmussen's encephalitis (RE) is a rare, progressive form of chronic encephalitis characterized by seizures and hemiparesis. About 10% of cases are late onset, typically occurring in adolescence or early adulthood. Symptoms are often milder with slower progression. We present four cases of late onset RE, with symptoms beginning at age 13 to 23. Methods: Information was gathered by chart review and included age of symptom onset, initial presenting complaint, MRI results, EEG findings, age of diagnosis, and treatment. Results: Mean onset of symptoms was 18.3 years (range 13-23). In three cases, seizure was the presenting complaint. In one patient hemiparesis was followed by seizures in one year. Two out of four patients experienced epilepsia partialis continua during the course of illness. In two cases the initial brain MRI showed inflammatory changes and atrophy. The other two cases had initially normal MRI scans and developed hemi-atrophy and diffuse unilateral T2 prolongation consistent with inflammation (16 years from onset of symptoms in both cases). All had EEG findings consistent with partial onset epilepsy. Mean age of diagnosis was 26.5 years (range 20-31) and average time from symptom onset to diagnosis was 8.8 years (range 0-16). Treatment included intravenous immunoglobulin (IVIg) and/or corticosteroids in all four patients. One of the four patients in our report progressed rapidly and was diagnosed in the first year of symptom onset. This patient is currently undergoing treatment with rituximab. To date, none required hemispherectomy. Conclusions: Late onset RE can present a diagnostic challenge, especially early in the disease. The initial MRI may be normal. Seizures may be suggestive of a partial onset epilepsy. As the disease progresses over decades, the diagnosis is established. The impact of immunosuppressive therapy in RE still needs to be determined in larger studies as compared to the natural course of the disease.