Familiarity with the clinical, MRI, CSF, and serologic features of MOGAD can help neurologists recognize this condition in clinical practice. Awareness of the utility and pitfalls of the MOG antibody test is critical. The current therapeutic approach is guided by retrospective studies and the application of immunotherapies used in other autoimmune neurologic disorders. In this episode, Gordon Smith, MD, FAAN, speaks with Eoin P. Flanagan, MBBCh, coauthor of the article "Myelin Oligodendrocyte Glycoprotein Antibody–Associated Disease" in the Continuum® April 2026 Multiple Sclerosis and Related Disorders issue. Dr. Smith is a Continuum® Audio interviewer and a professor and chair of neurology at Kenneth and Dianne Wright Distinguished Chair in Clinical and Translational Research at Virginia Commonwealth University in Richmond, Virginia. Dr. Flanagan is a professor of neurology and the division chair of the Division of Multiple Sclerosis and Autoimmune Neurology in the Department of Neurology at Mayo Clinic in Rochester, Minnesota. Additional Resources Read the article: Myelin Oligodendrocyte Glycoprotein Antibody–Associated Disease Subscribe to Continuum®: shop.lww.com/Continuum Earn CME (available only to AAN members): continpub.com/AudioCME Continuum® Aloud (verbatim audio-book style recordings of articles available only to Continuum® subscribers): continpub.com/Aloud More about the American Academy of Neurology: aan.com Social Media facebook.com/continuumcme @ContinuumAAN Host: @GordonSmithMD Full episode transcript available here Dr Smith: So, what neurological disorder can cause bilateral optic neuritis, transverse myelitis, ADEM, or can mimic acute flaccid myelitis, intracranial hypertension, viral encephalitis, or cause seizures? Sounds like the great imitator, perhaps. If you want to know and learn more about this syndrome and how you can treat it---and it is very treatable---keep listening. My name is Gordon Smith, and today I have the great opportunity to talk with Dr Eoin Flanagan from the Mayo Clinic on his article on myelin oligodendrocyte glycoprotein antibody associated disease, or MOGAD, which is in the April 2026 issue of Continuum on Multiple Sclerosis and Related Disorders. Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast. Dr Smith: This is Dr Gordon Smith. Today I'm interviewing Dr Eoin Flanagan about his article on myelin oligodendrocyte glycoprotein associated disease, or MOGAD, which appears in the April 2026 Continuum issue on multiple sclerosis and related disorders. Eoin, welcome to the podcast, and please introduce yourself to our audience. Dr Flanagan: Yeah, thanks so much. I'm Eoin Flanagan. I'm a neurologist at the Mayo Clinic. I'm originally from Ireland. I work in the neuroimmunology lab at the Mayo Clinic, and work and see patients with MS, MOG, and autoimmune disorders here in Rochester, Minnesota. Dr Smith: Your article is super interesting, I think, and this has been a really rapidly evolving area over the last, you know, many years. We have many more antibodies, and MOG is something that's been around for a while, but we've certainly learned a lot more about it. This is a topic that I think will be familiar to most of our listeners, but I wonder if maybe you can just begin by laying the foundation. Like, what is MOG? What's its typical presentation? Dr Flanagan: So, MOG is a protein on the surface of the oligodendrocyte or its CNS myelin, and it was always of interest as a potential antibody target, and initially it was investigated in multiple sclerosis. But subsequently, we recognized that the antibodies to MOG have a specific syndrome, of which about a quarter of patients are pediatric and then the remainder are adults. And they can present with a variety of syndromes, probably most commonly optic neuritis, but also acute disseminated encephalomyelitis, or ADEM. Transverse myelitis can also occur, and then some other unusual brain and brainstem cerebellar syndromes can also occur. Dr Smith: I was really impressed in the very broad phenotypic spectrum of MOG. We'll talk more about that, of course. But I wonder if maybe you can tell us when we should be ordering MOG antibody? Given this broad variability, does anyone who has a CNS demyelinating disease need a MOG assay, only specific phenotypes? What guidance do you have for our listeners? Dr Flanagan: Yeah. It's a great question. So, I think you have to be a little bit careful because the MOG antibody test is a little bit sticky. So sometimes we can see some low-positive false positives. So, we don't wanna order it in every single patient with classical MS. So, I suppose we'll start with who not to order it in. I think it's also a very optic nerve- and optic neuritis-central disease, so I think you really need to be considering this in a patient with optic neuritis who does not have lesions in the brain suggestive of multiple sclerosis. And then we think about some of the features: if the lesion, the enhancement along the optic nerve is long, if it's bilateral, if there's a lot of optic disc edema accompanying that, we tend to think about MOG antibodies. And then children with demyelinating disease, MOG is over-represented in that cohort, so it accounts for about a third of those. So, if you have a child with CNS demyelinating disease, particularly if they're under twelve, with ADEM presentations or other presentations, you probably want to be ordering the MOG antibody test. And then a longitudinally extensive transverse myelitis in adults, certain types of cerebral phenotypes that we can get into, you would want to consider ordering MOG antibodies too. Dr Smith: Now, you point out in the article that it's really important that laboratories use the cell-based assay for MOG as opposed to an ELISA, for instance. Is this something folks need to be very attentive to, or are all of the commercial laboratories now using a cell-based assay? Dr Flanagan: Yeah. I think all of the commercial labs are using cell-based assays, so we don't really get into much of an issue. There are some differences between serum and CSF, so really, serum is the optimal sample to order. There is also some differences between the live cell-based assay and the fixed cell-based assay, where the live cell-based assay may have some advantages in terms of sensitivity. And then CSF is kind of still under evaluation about its role in the condition. So in general, it's a serum test. And then we have to remember that the antibody tends to be highest at the onset, and then it goes down over time. So, if you delay your testing or you're testing a patient long after the condition, it can go negative, for example. So it tends to be highest both around the relapses and particularly at the onset of the condition. Dr Smith: You mentioned earlier that the test is sticky, which I take to mean that there is some risk for low-titer false positives. How do you navigate that situation? When should we be suspicious about a false positive? Dr Flanagan: Yeah. I think there's some very useful features that can help you. You know, the main differential diagnosis is going to be multiple sclerosis, particularly in the US, in regions of the northern US where MS is particularly common. So, you really wanna be making sure that if you get a positive result, low positive, that it's not multiple sclerosis. And some of the best discriminating features are CSF oligoclonal bands. They're about 85% in MS and about 15% in MOG, so an easy number to remember, 85 and 15. And then the lesions in MOG, the brain lesions, tend to disappear over time. So, if you have the advantage of that follow-up MRI a year down the line, about 70% of lesions in MOGAD will resolve, while in MS, as we know, the term means multiple scars, so the MS lesions tend to persist over time. So, they are two quite useful features that can help discriminate. Dr Smith: And how about specific phenotypes or areas of involvement or imaging abnormalities that suggest MOG? One of the things I found really interesting in your article is there are a host of different syndromes that I think had largely been previously described, many of them, that became clear later that these were really tied to MOG antibodies. Presumably, that's helpful in interpreting the antibody assay in that patients who have, perhaps, a borderline low titer, for instance, but have a very typical phenotype are more likely to have MOG than those who have a more clearly MS-type phenotype. Dr Flanagan: Yeah, absolutely right. Yes. So, there's certain phenotypes that we don't tend to see with MS. The acute disseminated encephalomyelitis, or ADEM, is one that's particularly common in children. And about half of people that have ADEM will be positive for the MOG antibody. So that's a syndrome you need to look out for, which would be often in children, encephalopathy, and they would have multifocal white matter lesions, sometimes involving the gray matter. A second syndrome that was an interesting discovery from a Japanese group was this unilateral cerebral cortical encephalitis, where patients can have this swelling and T2 hyperintensity, often just on one side of the brain. And it's in the cortex, and some of those patients won't have any white matter lesions. And in that situation, it's important to order the MOG antibody, and that seems to be a specific phenotype of MOGAD. But sometimes people don't think about it because the white matter is not involved. So, if you see these patients, they often present with seizures, sometimes they even have fever accompanied by it. And if you see those patients and see
