Test Details: Neuromyelitis optica (NMO) is a severe relapsing inflammatory demyelinating disease of the CNS that preferentially affects the optic nerve, spinal cord and circumventricular organ systems. Antibodies to aquaporin 4 (called NMO IgG or AQP4 Ab) in CSF sample is a marker for diagnosis of neuromyelitis optica (NMO) that can facilitate the differential diagnosis of NMO and classic multiple sclerosis.