Use

NMO (neuromyelitis optica, Devic disease) is an immune‑mediated chronic inflammatory disease predominantly affecting the optic nerve and spinal cord, presenting with optic neuritis and myelitis. Limited forms—such as isolated optic neuritis, brainstem encephalitis, and longitudinally extensive transverse myelitis (LETM)—are referred to as NMO spectrum disorders (NMOSD). Detection of antibodies against AQP4 or MOG is associated with NMO and NMOSD; AQP4 is evaluated first, with reflex to MOG when appropriate, aiding diagnostic clarity.