Neuromyelitis optica (NMO) spectrum disorders represent an evolving group of central nervous system–inflammatory autoimmune demyelinating diseases unified by a pathogenic autoantibody specific for the aquaporin 4 (AQP4) water channel. Disability is attack related and accrues incrementally, in contrast to multiple sclerosis, where disability generally occurs progressively in the later phase of the disease. Currently, immunosuppression is the mainstay of treatment in NMO. Based on relatively small retrospective and open-label prospective series, several treatments appear to be effective in preventing attacks and stabilizing disability in NMO. Unfortunately, these studies are limited by lack of randomization. The immunosuppressants most commonly prescribed for maintenance of remission include prednisone, azathioprine, mycophenolate mofetil, and rituximab. Breakthrough attacks should result in reevaluation of treatment strategy. Currently, outcomes appear more favorable than traditionally considered; this is believed to be related to a combination of earlier diagnosis (owing to the availability of AQP4-IgG testing, which confirms the diagnosis) and initiation of immunosuppressive medication. Despite optimal dosing, azathioprine, mycophenolate mofetil, and rituximab fail to prevent attacks in 53%, 25%, and 17% of patients, respectively. Thus, currently available treatments clearly do not offer a cure; they can also be associated with significant adverse effects. The use of rituximab for treatment of NMO is increasing, particularly in the United States. The challenge facing us is to optimize its efficacy, while limiting both cost and adverse effects.
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