AQP4 and optic neuritis: Compared with patients with EO-NMOSD, those with LO- or VLO-NMOSD exhibit: more-severe disability; faster progression; severe myelitis with longitudinal spinal cord involvement, rather than optic neuritis (ON); higher AQP4-IgG seropositivity and higher AQP4-IgG titers; more white matter hyperintensities; more-severe sleep disorders; higher levels of anxiety; poorer cognitive function; and higher scores on the Clinical Dementia Rating-community affairs scale (9–12).