Testing for Neuromyelitis Optica (NMO)
So I have talked to you about how NMO-IgG can help us make a diagnosis of a neuromyelitis optica spectrum disorder, but what else can the antibody do? We have also found that the antibody can be predictive of the development of future attacks, and this is important because it will impact management.
Here you can see a Kaplan-Meier survival analysis stratified by NMO-IgG status. In this study, Dr. Weinshenker and colleagues looked at the likelihood of developing a further event of either transverse myelitis or optic neuritis if you had had a single event of transverse myelitis. Patients were divided into those that were NMO-IgG positive and those that were NMO-IgG negative. If you had a single episode of longitudinally extensive transverse myelitis and you are NMO-IgG negative, then none of those patients developed another attack or a second event in the follow-up period. However, if a patient had a single episode of longitudinally extensive transverse myelitis and was found to be positive for the NMO-IgG, then 56% of those patients had a second event of either optic neuritis or a further episode of longitudinally extensive transverse myelitis within 1 year.
This study suggests that NMO-IgG, if positive in the setting of a single episode of longitudinally extensive transverse myelitis, is predictive of the development of a further event and, if that event is an optic neuritis, then fulfillment of the criteria for NMO. Thus, if a patient has a longitudinally extensive transverse myelitis and is positive for the antibody, we would recommend initiation of an attack-preventing treatment, an immunosuppressive medication that I have discussed previously.
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