Abstract: Acute encephalitis is an infectious disease caused by viruses, bacteria, fungi or other microorganisms, which will mainly cause by central nervous system damage. This disease can be life-threatening. If active and effective treatment measures can be taken earlier, the cure rate will be improved. In clinical practice, patients with typical acute encephalitis can be diagnosed by neurological symptoms and signs of infection, while suspected patients are often difficult to be diagnosed. Imaging examination is crucial for the diagnosis of acute encephalitisby various pathogens, especially after the lumbar puncture. Immediate MRI examination of the brain is the first choice for the diagnosis of acute encephalitis ^[1]. Brain MRI can prompt diagnosis and sometimes even can discover pathogens. It can not only assess the extent of brain damage, but also exclude some major differential diagnoses, such as cerebrovascular lesions or tumors^[2]. At present, there are few reviews about MRI manifestations of encephalitis caused by various pathogens in China. This article briefly reviews the pathogenesis of some viruses and bacterial encephalitis and the MRI manifestations of encephalitis caused by different pathogens, in order to facilitate early accurate diagnosis and guide clinical practice timely and effectively.

Key words: Acute encephalitis, Pathogen, MRI