Common causes of encephalitis include microbial infection, poisoning, and neoplastic diseases. 1. Microbial infection: common in viral encephalitis, bacterial encephalitis, etc. Viruses or bacteria can attack the central nervous system, which can be clarified by cerebrospinal fluid, serum test, travel or contact history. 2. Autoimmune encephalitis: it is a kind of encephalitis caused by autoimmune mechanism mediated by immune reaction against central nervous system antigens, with clinical manifestations of mental behavioral abnormality, cognitive dysfunction, and epilepsy with acute or subacute seizures. 3. Tumor disease: some brain tumors may cause encephalitis due to tumor stimulation or tumor secretion stimulation. Common neoplastic diseases include diffuse glioma, molluscum contagiosum, etc., which can be clarified by MRI and cerebrospinal fluid cytology. It is recommended to seek timely medical treatment for suspected symptoms of encephalitis, and improve the examination and targeted treatment under the guidance of the doctor.