AQP4 and neuromyelitis optica: In this respect, neuromyelitis optica (NMO), also named Devic's disease, is a heterogeneous disease, characterized by chronic demyelinating inflammation of the optic nerve and the spinal cord, mostly characterized by the presence of antibodies targeting aquaporin-4 (NMO antibodies) with a specificity of 90% [113]; this autoantigen, expressed on astrocytes in a perivascular distribution, represents a water channel regulating the water homoeostasis in the central nervous system [114].