Neuromyelitis optica in western countries: Establishing diagnostic criteria and characterization of the spectrum

Neuromyelitis optica (NMO) can be distinguished from MS by clinical, radiological and serological findings, especially the tendency for spinal cord lesions to be longer than 3 vertebral segments during acute attacks and the presence of aquaporin-4 autoantibodies in NMO. The spectrum of NMO is broader than previously realized and includes recurrent myelitis, recurrent optic neuritis, certain cerebral presentations, including intractable vomiting and posterior reversible encephalopathy. It may coexist with other systemic autoimmune diseases, including systemic lupus erythematosus and Sjogren's syndrome. Whether NMO has a predilection for individuals of Asian ancestry or whether there are differences between NMO and Asian optic-spinal MS other than arbitrary definitions remains to be clarified. Further epidemiological studies using comparable diagnostic criteria, radiological studies and serological tests are required.