Objective: Identify the causes of encephalitis and describe some clinical and laboratory features of each cause. Subjective and methods: Subjective are all patients with encephalitis who were treated in National Hospital of Pediatrics from January of 2011 to June 30th, 2012. A case of encephelitis are confirmed based on "Guidelines for diagnosis and management of acute viral encephalitis in children" issued by Ministry of Health on 2008. The identification of causes is based on the CSF and serum results of molecular biological and immunological techniques. Results: From January of 2011 to June 30th, 2012, there were 849 children with encephalitis being treated in National Hospital of Pediatrics. Prevalence of identified causes is 29.9 percent. The most common causes are listed below: Rubella 40.23 percent, Japanese Encephalitis 27.34 percent, HSV1 14.45 percent, EV 7.81 percent, mumps 3.91 percent, varicella-zoster 2.34 percent. Among 134 identified cases, the most common encounters are JE (52.24 percent), HSV1 (27.62 percent), EV (14.93 percent). The common signs of HSV1 encephalitis are focal convulsion and paralysis (41.7 percent and 35.1 percent). On brain imaging (crscanner and MRI), the lesions of HSV1 encephalitis are usually located in temporal and frontal lobe
the lesions of JE are usually diffuse edema and located in thalamus.