Encephalitis is an inflammatory lesion of the brain parenchyma caused by the attack of pathogens. The most common form of encephalitis in children is viral encephalitis. The severity of the disease varies widely and is related to the site of neurological involvement, the strength of the viral pathogenicity, and the immune response of the child. Prodromal or concomitant symptoms: The prodromal symptoms are mostly respiratory or gastrointestinal symptoms, such as sore throat, cough, vomiting, diarrhea, and loss of appetite. 2. Fever: The fever can be of different degrees, and low fever, moderate fever, and high fever are all possible; in the case of epidemic B encephalitis, the fever is often acute and high or super high. 3. Neuropsychiatric symptoms (1) Disorders of consciousness: indifference, sluggishness or irritability, drowsiness in mild cases; delirium and coma in severe cases. (2) Convulsions: can be limited, generalized or continuous. (3) Intracranial hypertension signs: ① persistent headache and frequent vomiting in older children; infants often show irritability, irritability, screaming or double vision, often with varying degrees of consciousness; ② increased muscle tone or tonicity of the extremities; ③ increased blood pressure, slowed breathing irregularities or even pauses; ④ infants with bulging fontanelle, increased tension, followed by separation of cranial sutures and increased head circumference and fontanelle; ⑤ optic papilla edema, but in acute intracranial high pressure is often absent, and is rare in infants. The presence of impaired consciousness, dilated pupils, and increased blood pressure with bradykinetic triad signs suggest cranial hypertension, which is often a precursor to brain herniation. (4) Positive cone bundle signs: positive pathological signs such as Bartholomew’s sign. (5) Limited cerebral symptoms (related to the site of involvement): (1) brainstem damage: respiratory changes, cerebral nerve palsy, and teeel changes; (2) basal nucleus damage: tremor, hyperactivity, and muscle tone changes; (3) cerebellar damage: ataxia; (4) frontal lobe damage: abnormal mental behavior and motor aphasia; (5) temporal lobe damage: central hearing loss; (6) occipital lobe damage: central blindness; (7) cortical motor function damage: central unilateral or unilateral or single limb paralysis.