The inflammatory autoimmune disease neuromyelitis optica (NMO, opticospinal encephalomyelitis, Devic's syndrome) is a rare form (around 1%) of the group of acquired demyelinating diseases of the central nervous system (CNS) with degradation of the insulating sheath of at least one optical nerve (neuritis nervi optici) and at the same time of a few months later the spinal cord (myelitis). Diagnosis is made mostly clinically with anamnesis, neurological and neurophysiological tests, MRT of the CNS and lumbar puncture. The diagnosis NMO is confirmed in laboratory diagnostics by the determination of autoantibodies against AQP-4. The major significance of the autoantibody detection is that autoantibodies against AQP-4 (NMO-IgG) allow serological differentiation of prognostically poor NMO from classic multiple sclerosis (MS), which can influence therapy decisions significantly. While MS is treated with immune-modulating substances, NMO requires the use of immuno-suppressive drugs.