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Aquaporin-4 (AQP4)-IgG-positive neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune astrocytopathic disease and severe attacks of NMOSD can quickly lead to blindness and paralysis. The international diagnostic criteria of NMOSD (2015) have facilitated early diagnosis of the disease which allows for early treatment. Some disease modifying drugs for multiple sclerosis are inefficacious and immunosuppressive drugs (corticosteroid, azathioprine, mycophenolate mofetil, etc) have been used to prevent relapse in AQP4-IgG-positive NMOSD. A few years ago, the results of randomized controlled trials of four monoclonal antibodies (anti-C5, anti-IL-6R, anti-CD19, and anti-CD20) in AQP4-IgG-positive NMOSD cases were reported and they are expected to change the therapeutic landscape. Efficacy, safety, tolerability, and practical considerations, including patient’s life style and potential cost, are important in deciding on the therapeutic strategy. Other therapeutic approaches, such as stem cell transplantation and tolerance induction, may also be promising in this disease.

AQP4-IgG-seronegative NMOSD is a diagnostic challenge and could be a heterogeneous group of diseases. Myelin oligodendrocyte glycoprotein (MOG)-IgG-associated disease (MOGAD) is a newly recognized entity with NMOSD and other clinical phenotypes. Some cases of MOGAD are relapsing. In addition to immunosuppressants used in AQP4-IgG-positve NMOSD, intravenous immunoglobulins appear to be efficacious in MOGAD. Overall, rituximab can reduce the relapse rate, but unlike AQP4-IgG-positive NMOSD, relapse may occur in some MOGAD patients receiving rituximab despite effective B cell depletion.

In this presentation, the therapeutic issues and evidence of AQP4-IgG-positive NMOSD, AQP4-IgG-negative NMOSD including MOGAD will be reviewed and the challenges that lie ahead will be discussed.

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The visual pathways offer a unique platform for integrated assessment of demyelinating, neurodegenerative and repair mechanisms in demyelinating diseases. While visual evoked potentials (VEPs) allow to assess the functional impact of a demyelinating lesion, optical coherence tomography measures in vivo the neuroaxonal and inflammatory processes, based upon microstructural changes in the different retinal layers. After optic neuritis, the combination of the two methods may assist in the differential diagnosis between multiple sclerosis (MS), characterized by autoimmune processes mainly targeting myelin, from neuromyelitis optica spectrum disorder, characterized by a more severe neuroaxonal damage. As VEPs become abnormal very early during development of optic neuritis symptoms, while OCT reveals neuroaxonal damage, we should refine the appropriate time sequencing of both methods when integrating them in clinical practice, observational research and clinical trials. Concerning the latter application, these methods provide useful measures for treatment interventions targeting remyelination (VEPs) and neuroprotection (OCT). Finally, the study of eyes not affected by optic neuritis in MS and NMOSD provides useful measures of hidden underlying processes associated with disease activity, compartimentalized inflammation and neurodegeneration, which are also an important target of different therapeutic interventions.