A demyelinating disease of the central nervous system characterized by the presence of a demyelinating event (optic neuritis, myelitis, acute/multiphasic encephalomyelitis, cerebral or polyfocal deficits, brainstem or cerebellar deficits, and/or cerebral cortical encephalitis), a positive myelin oligodendrocyte glycorotein-IgG test, and exclusion of an alternative diagnosis like MS.