Clinically, acute myelitis occurs after infection, and the inflammation often involves the gray and white matter of several medullary segments and their surrounding spinal membranes, with the thoracic medulla being the most susceptible and producing transverse spinal cord damage symptoms. In some patients, the level of paralysis and sensory impairment rises, eventually reaching the upper cervical medulla and causing tetraplegia and respiratory muscle paralysis, and may be accompanied by high fever, endangering the patient’s life. So, what are the causes of acute myelitis? The cause is not known, but may be due to some viral infections, or an autoimmune reaction of the body after infection, or some occur after vaccination. Depending on the etiology, there are different clinical syndromes, such as: post-infectious myelitis, vaccination myelitis, demyelinating myelitis, necrotizing myelitis and paraneoplastic myelitis. Although most patients had symptoms of viral infection such as fever, upper respiratory tract infection, and diarrhea 1-4 weeks before the disease, no viral antibodies were detected in their cerebrospinal fluid, and no virus was isolated from the spinal cord or cerebrospinal fluid, so it was speculated that it might be related to the autoimmune reaction after viral infection. Finally, as the disease worsens, inflammation can involve different parts of the spinal cord, but the upper thoracic medulla is the most common. The spinal cord is swollen, congested, and soft, and the soft spinal membrane is congested and cloudy. The gray and white matter of the spinal cord is indistinctly demarcated in the spinal cord section, and punctate hemorrhage is visible. According to the content of this article, I believe that the introduction of the causes of acute myelitis has been understood, so strengthening physical fitness, preventing colds and diarrhea, and avoiding vaccination when poor health can help prevent the occurrence of this disease. If there is weakness in the lower limbs or extremities, numbness, and difficulty in relieving bowel movements, you should be sent to the hospital promptly for medical treatment.