Long spinal cord lesions, or long segmental spinal cord lesions, are a complex group of diseases with three or more consecutive vertebral body lengths on spinal cord MRI. A large number of clinical observations have revealed that about 50% of long segmental spinal cord lesions may develop into optic neuromyelitis optica, which is more diagnostic if combined with other autoimmune diseases or combined with autoantibody positivity. Therefore, for long-segment spinal cord lesions, routine screening for antibodies to aquaporin 4 (AQP4), a specific antibody for optic neuromyelitis optica, is recommended, and a positive result will lead to a clear diagnosis and regular treatment of optic neuromyelitis optica. The long spinal cord lesions of optic neuromyelitis optica have the following characteristics: 1. Most transverse damage, H-shaped or circular lesions on spinal cord MRI cross-section, clinically manifested as limb weakness, numbness, pain, and urinary and fecal disorders. 2. The spinal cord lesion may show obvious swelling and low signal on magnetic resonance T1 imaging, and some patients may show dilatation of the central canal of the spinal cord. 3, mostly involving the cervical and thoracic spinal cord, the cervical medullary lesions have a tendency to extend to the medulla oblongata (brainstem). 4. Enhanced scans may show patchy or striated enhancement, which may be accompanied by spinal strengthening. However, it should be noted that nearly 50% of long-segment spinal cord lesions are due to other causes such as dural arteriovenous fistula, acute disseminated encephalomyelitis, paraneoplastic myelopathy, and infectious myelitis, which are also treatable and need to be excluded clinically.