Neuromyelitis optica aquaporin-4 antibody negative

**Definition:** Neuromyelitis optica (NMO) is an inflammatory demyelinating disease of the central nervous system characterised mainly by attacks of uni- or bilateral optic neuritis (ON) and acute longitudinally extensive (> 3 vertebral segments) myelitis. This form is seronegative for aquaporin-4 antibodies. Some patients may be myelin oligodendrocyte glycoprotein (MOG) antibody positive.