Encephalitis.

Encephalitis is an acute infection of brain parenchyma characterized clinically by fever, headache, and an altered level of consciousness. There may also be focal or multifocal neurologic deficits, and focal or generalized seizure activity. This article discusses the clinical presentation, diagnosis, and treatment of herpes simplex virus (HSV) encephalitis, the arthropodborne viral encephalidities, Rocky Mountain spotted fever, viral encephalitis in the immunocompromised patient, and postinfectious encephalomyelitis.