MRI in patients with optic neuromyelitis optica is characterized by long spinal cord inflammatory demyelinating lesions, generally greater than 3 vertebral segments in length, which are mostly located in the central part of the spinal cord on axial images, involving most of the gray matter and some of the white matter. The lesions are mainly found in the cervical and thoracic segments. In the acute stage, the spinal cord is swollen and cavity-like changes can be seen in severe cases, and the lesions can be strengthened after enhancement scans. The lesions in the cervical segment may extend upward to the lower part of the medulla oblongata. In the recovery phase, the spinal cord may atrophy at the lesion. In contrast, in multiple sclerosis, the length of the spinal cord lesion is less than 2 vertebral segments, the lesion is mainly located in the white matter, and spinal cord swelling in the acute phase and spinal cord atrophy in the remission phase are not significant. The affected optic nerve in optic neuromyelitis optica shows swelling and thickening, and the optic nerve sheath shows long T1 and long T2 signals. The pathology demonstrates that the inflammatory response of the optic nerve causes local obstruction of cerebrospinal fluid circulation, resulting in a T2-weighted image with “orbit-like” high signal. In some patients without hypermetropia, a similar presentation is still present. As the disease progresses, some patients may see punctate high signal changes in the optic nerve. Enhancement scans show small striations of enhancement in the affected optic nerve. More than half of the patients with optic neuromyelitis optica initially have normal brain MRI examinations, but abnormal nonspecific lesions are found on subsequent MRI review. Most of these lesions are small and nonspecific and do not meet the criteria for MS, and a few are located in the hemispheres, fused to subcortical areas, and some are located in the hypothalamus, thalamus, triventricles, periventricles, and peduncles, and these lesions in the brain are usually nonenhancing.