Rasmussen's syndrome (chronic encephalitis with epilepsy) is a rare neurological disorder of unknown cause characterized by severe epilepsy, hemiplegia, dementia, and inflammation of the brain, and progressive functional and structural destruction of a single cerebral hemisphere. While one mechanism underlying the pathogenesis of Rasmussens encephalitis has been hypothesized to be mediated by production of excitotoxic GluR3 autoantibodies to the a-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptor, other neuropathological etiologies have also been indicated. Proposed therapies have included antiepileptics, steroids, antiviral agents, alpha-interferon, and immunoglobulin. The mainstay of therapy is surgical hemispherectomy. To date, no medical therapies have permanently halted neurologic deterioration.