The goal of this research study is to investigate whether Rituximab is safe to use in patients suffering from NMO, or who are at high risk for developing NMO. It is thought that NMO is caused by the immune system reacting against the optic nerves and spinal cord. B cells are a part of the immune system that may contribute to the illness. Rituximab is an antibody that depletes B cells. Depletion of these B cells with Rituximab may induce remission of the disease. Because pathological and serological studies suggest that NMO appears to be, at least in part, a B-cell mediated disease Rituximab, is an attractive treatment candidate for this disease.