Optic neuromyelitis optica is an inflammatory demyelinating disease of the central nervous system involving mainly the optic nerve and spinal cord, first reported by Eugène Devic in 1884, and therefore also known as Devic’s disease. In recent years, it has been found that antibodies to the CNS aquaporin-4 (AQP4) (NMO-IgG) are more specific immunological markers for optic neuromyelitis optica, and have differential diagnostic value between optic neuromyelitis optica and multiple sclerosis. Regardless of the ethnic distribution, immunological mechanism, pathological changes, clinical manifestations and imaging changes, as well as treatment and prognosis, optic neuromyelitis optica differs from multiple sclerosis, and should be differentiated in the early stage of the disease and treated differently between optic neuromyelitis optica and multiple sclerosis. 1, clinical manifestations and prognosis are different The vast majority of optic neuromyelitis optica is a relapsing type, and the ratio of female to male is much higher than male, and the ratio of female to male can be as high as 10:1. Patients with optic neuromyelitis optica mainly present clinically with visual impairment and myelitis optica, and their degree of neurological dysfunction is significantly greater than that of multiple sclerosis, with a dramatic decrease in visual acuity or even blindness, bilateral lower limb paralysis and urinary retention, and sensory impairment. Visual impairment in patients with optic neuromyelitis optica is less effective than multiple sclerosis with high-dose methylprednisolone shock therapy. About 15% of patients with optic neuromyelitis optica have symptoms outside the optic nerve and spinal cord, such as encephalopathy, hypothalamic and brainstem symptoms. Although the majority of patients with optic neuromyelitis optica have a worse prognosis than multiple sclerosis, they are less likely to progress to the secondary progressive form. The frequency of relapses is significantly higher in optic neuromyelitis optica than in classical multiple sclerosis, with some patients experiencing clustered relapses early in the disease, with a 1-year relapse rate of approximately 60 and a 3-year relapse rate of up to 90%. Some patients with optic neuromyelitis optica in Western countries have a monochromatic course, with bilateral optic neuritis optica and myelitis optica occurring simultaneously or sequentially, with similar proportions of men and women. Some patients with optic neuromyelitis optica may have other autoimmune diseases, such as systemic lupus erythematosus, dry syndrome, mixed connective tissue disease, myasthenia gravis, hyperthyroidism, Hashimoto’s disease, polyarteritis nodosa, pernicious anemia, ulcerative colitis, primary sclerosing cholangitis, and idiopathic thrombocytopenic purpura. 2, MRI performance is different in patients with optic neuromyelitis optica MRI manifests as long spinal cord inflammatory demyelinating lesions, generally greater than 3 vertebral segments in length, mostly located in the cervical and thoracic medulla, cross-sectional imaging lesions are mostly located in the center of the spinal cord, involving most of the gray matter and part of the white matter. In the acute phase, the spinal cord is swollen, and in severe cases, cavity-like changes can be seen, and the lesion can be enhanced on enhanced scanning. Patients with such long spinal cord demyelination changes have a high detection rate of positive serum NMO-IgG antibodies. Recent MRI studies have found that intracerebral lesions may be present in patients with optic neuromyelitis optica, but such lesions are not consistent with multiple sclerosis lesions. About half of the patients have no abnormalities on MRI of the head at the beginning of the disease, but abnormal lesions can be detected during subsequent review. These lesions are mostly nonspecific, with a few of them located in the cerebral hemispheres and fused to the subcortical areas, and others distributed in the hypothalamus, thalamus, around the third or fourth ventricle, and the peduncle; unlike multiple sclerosis, these intracerebral lesions are not enhanced on enhanced MRI scans. However, foci in the hypothalamus, periventricular area of the third or fourth ventricle can have high expression of AQP4, suggesting that these lesions may be related to water channels. 3. Different laboratory findings Serological tests (1) NMO-IgG: a specific autoantibody marker for optic neuromyelitis optica, mostly expressed at the astrocyte peduncle of the blood-cerebrospinal fluid barrier. Serum NMO-IgG is mostly negative in patients with multiple sclerosis, therefore, positive serum NMO-IgG is an important basis for differentiating optic neuromyelitis optica from multiple sclerosis. The sensitivity and specificity of the NMO-IgG assay is higher than that of the cell transfection indirect immunofluorescence assay. (2) Glial fibrillary acidic protein (GFAP): This marker has some clinical significance in differentiating optic neuromyelitis optica from multiple sclerosis. The expression level of serum glial fibrillary acidic protein (GFAP) is significantly increased in the acute phase of optic neuromyelitis optica, while it is mostly normal in the acute phase of multiple sclerosis. Therefore, serum GFAP may also be a biological marker of optic neuromyelitis optica. (3) Other autoimmune antibodies: Our clinical study showed that the positive detection rate of serum ANAs in patients with optic neuromyelitis optica was 44.44% (36/81), among which the positive detection rates of ANA, anti-dsDNA, anti-adherent antibody (ACA), anti-SSA antibody, and anti-SSB antibody were 35.80% (29/81), 6.17% (5/81), and 1.23% (1/81), respectively. ), 1.23% (1/81), 24.69% (20/81) and 8.64% (7/81), respectively, while only one patient in the multiple sclerosis group was positive for ANAs (1/49). 4. Different diagnostic criteria The diagnosis of optic neuromyelitis optica should refer to Wingerchuk’s 2006 version of diagnostic criteria for optic neuromyelitis optica. The new version of the diagnostic criteria for optic neuromyelitis optica removes the necessary condition of “no evidence of central nervous system involvement other than the optic nerve and spinal cord” and adds the supporting condition of a positive serological NMO-IgG test. For the same patients with optic neuromyelitis optica, the old diagnostic criteria had a sensitivity of 85% and a specificity of 48%, while the new diagnostic criteria have a sensitivity of 94% and a specificity of 96%. The diagnosis of multiple sclerosis should refer to the McDonald’s multiple sclerosis diagnostic criteria published in 2010. 5.The treatment principle of optic neuromyelitis optica should be different from that of multiple sclerosis Acute treatment (1) glucocorticoid: the principle of glucocorticoid treatment for patients with multiple sclerosis is high dose and short course, and it is not advocated to apply small dose for a long time, often using methylprednisolone shock therapy. For example, starting from 1g/d, intravenous drip for 3-4h, continuous treatment for 3 d, after which the dose is stepped down by half, each dose applied for 2-3 d, until <120mg/d, changed to maintenance dose of 60-80mg/d orally, 1 time/d, each therapeutic dose side for 2-3 d, continue stepped down by half until discontinuation, total course of treatment <3-4 weeks. However, a significant proportion of patients with optic neuromyelitis optica are hormone-dependent, and the disease may be aggravated during the process of dose reduction or when the speed of drug discontinuation is too fast. Therefore, the hormone reduction process for hormone-dependent patients should be slow, and the dose can be reduced by 5mg per week to the maintenance dose (15-20mg/d), and the maintenance time for small doses of hormone should be longer than that for multiple sclerosis, and the small dose can be maintained for several months. (2) Intravenous high-dose immunoglobulin (IVIg): The overall efficacy of IVIg in the treatment of multiple sclerosis is still unclear and is only indicated for patients who are intolerant to glucocorticoid therapy or who are pregnant or postpartum. IVIg may be slightly more effective than multiple sclerosis in the treatment of optic neuromyelitis optica and can be tried in those who are ineffective with hormones. (3) Plasma exchange: Plasma exchange therapy may be effective in patients with optic neuromyelitis optica who have failed to respond to hormone therapy, especially when applied early in the relapse, and patients may experience significant improvement in symptoms after two plasma exchanges. The importance of humoral immune mechanisms in optic neuromyelitis optica is further confirmed by the fact that removal of antibodies, immune complexes and activated complement from plasma may reduce the inflammatory response in the central nervous system. Plasma replacement is generally recommended 3 to 5 times with 2 to 3 L of plasma each time, and most patients can see results after 1 to 2 treatments. However, the efficacy of plasma exchange in multiple sclerosis is unclear. In summary, early identification of optic neuromyelitis optica and multiple sclerosis is crucial. Patients with suspected optic neuromyelitis optica should be promptly tested for serum AQP4 antibodies for early diagnosis to avoid treating optic neuromyelitis optica in exactly the same way as classical multiple sclerosis.