A case of unilateral hemispheric encephalitis.

Herein we report a case of encephalitis involving the unilateral hemisphere, with a clinical course different from that of Rasmussen syndrome. A 44-year-old man visited us because of headache and language abnormality. Cerebrospinal fluid examination showed lymphocytosis with increased level of protein. Brain MRI showed abnormal findings limited to the unilateral hemisphere. The symptoms and signs improved without any specific antiviral treatment in a week. However, language disturbance and right hemiparesis developed after a week. Steroid therapy was effective. He recovered without any neurologic sequelae. Our case was unusual encephalitis involving the unilateral hemisphere, which was benign and steroid-responsive.