Neuromyelitis optica (NMO) is a neuroinflammatory disorder characterized by optic neuritis and extensive myelitis. Like multiple sclerosis (MS), it can have a relapsing remitting disease course. Some of the NMO patients tend to run a more aggressive disease course. Most patients with NMO have Ig G antibodies to the aquaporin-4 water channel (AQP4).
In July 2015, experts from International Panel for NMO Diagnosis (Wingerchuk DM et al. Neurology 2015 Jul 14) provided updated consensus recommendations for NMO spectrum disorders (NMOSD). These consensus criteria support a broader range of clinical and imaging findings to support the diagnosis. These new criteria collapse everything under the NMOSD heading.
Patient with clinical presentation with at least one core syndrome should be evaluated for possible NMOSD. Some of these syndromes are similar to MS, such as optic neuritis and acute myelitis. Other typical syndromes, such as area postrema syndrome (intractable nausea and vomiting, or hiccups), an acute brainstem syndrome or symptomatic narcolepsy should also be evaluated carefully. Alternate diagnoses, particularly multiple sclerosis (MS), sarcoidosis, malignancy, paraneoplasia, and central nervous system infection should be excluded.
The panel noted that these criteria should also apply to children, with a few caveats, especially that longitudinally extensive transverse myelitis (LETM) is probably less specific for NMO in children than in adults, as LETM is not infrequent in pediatric MS (about 15% of myelitis presentations) and can also occur with acute disseminated encephalomyelitis.
These valuable criteria allow us to make a correct diagnosis of NMOSD early in the disease course. As the biology of AQP4 antibody–negative NMOSD is elucidated, and particularly if other antigenic targets and biomarkers are confirmed, it will be important to revisit this diagnostic approach and consider reclassification based on mechanism.