Testing for Neuromyelitis Optica (NMO)
In regards to optic neuritis, there are 2 groups of patients to consider. The first are those that present with a single episode of optic neuritis, and the second are those that present with multiple episodes of optic neuritis.
In regards to the spinal cord disease, there are 2 groups of patients to consider. Those that present with a longitudinally extensive spinal cord lesion, extending over greater than or equal to 3 vertebral segments, similar to the image that I showed on the first slide, or, patients with short spinal cord lesions that are less than 1 vertebral segment.
We recommend that NMO-IgG be tested in patients presenting with longitudinally extensive transverse myelitis for whom no other cause has been found, or patients presenting with multiple episodes of optic neuritis. In our studies we have found that the likelihood of identifying neuromyelitis optica IgG in a patient with a longitudinally extensive transverse myelitis is approximately 30% to 40%. The likelihood of identifying NMO-IgG in patients with recurrent episodes of optic neuritis is approximately 15% to 20%.
We think it is reasonable to consider ordering NMO-IgG in patients with a single episode of optic neuritis or a short spinal cord lesion. However, the prevalence of NMO-IgG in these 2 groups is much, much lower than in the other groups marked in green. Though, the frequency of the antibody in these patients is much lower. If, for example, NMO-IgG were to be identified in a patient with a single episode of optic neuritis than that would predict the development of another attack of optic neuritis, or of a transverse myelitis, and would mean that that patient likely has an NMO spectrum disorder.
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