AQP4 and neuromyelitis optica: Neuromyelitis optica (NMO) is another inflammatory demyelinating disease of the CNS which is characterized by lesions confined to the optic nerve and spinal cord, especially longitudinally extensive spinal cord lesions [4], antiaquaporin-4 (AQP-4) autoantibody seropositivity [5], and astrocytic impairment associated with the loss of AQP-4 in NMO lesions [6].