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Advances in immunotherapies for multiple sclerosis and related disorders have increased the risk of infections and raised important questions about vaccination efficacy. This episode reviews infection risks across treatment classes, emphasizes the importance of monitoring and patient education, and discusses optimal vaccine timing to preserve protective immune responses.
In this episode, Aaron L. Berkowitz, MD, PhD, FAAN, speaks with Avindra Nath, MBBS, FAAN, coauthor of the article "Infection Risk and Vaccine Considerations in Multiple Sclerosis and Related Disorders" in the Continuum® April 2026 Multiple Sclerosis and Related Disorders issue.
Dr. Berkowitz is a Continuum® Audio interviewer and a professor of neurology in the Department of Neurology at the University of California, San Francisco, in San Francisco, California.
Dr. Nath is the chief of the Section of Infections of the Nervous System at the National Institute of Neurological Disorders and Stroke, National Institutes of Health, in Bethesda, Maryland
Additional Resources
Read the article: Infection Risk and Vaccine Considerations in Multiple Sclerosis and Related Disorders
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Host: @AaronLBerkowitz
Full episode transcript available here
Dr Berkowitz: Over the last decades, there has been a revolution in the treatment of multiple sclerosis, neuromyelitis optica spectrum disorder, and other immune-mediated neurologic conditions with countless new, highly effective medications. However, with every new treatment comes new risks; and in the case of immunomodulatory therapy, many of those risks relate to infection. Today, I have the privilege of talking with an expert on this topic, Dr Avindra Nath, about the infectious risks of treatments for multiple sclerosis and other immune-mediated neurologic 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 Berkowitz: This is Dr Aaron Berkowitz, and today I'm interviewing Dr Avi Nath about his article on vaccine considerations and infection risk in multiple sclerosis and related disorders, which he coauthored with Dr Amit Bar-Or. This article appears in the April 2026 Continuum issue on multiple sclerosis. Welcome to the podcast, Dr Nath, and could you please introduce yourself to our audience? 
Dr Nath: Thanks very much for inviting me to this podcast. I'm absolutely delighted to have the opportunity to discuss our areas of interest and expertise related to infections and vaccinations for MS patients. My area has been studying the infections of the nervous system since the beginning of the AIDS pandemic, and over the years and decades, we've developed expertise related to various types of CNS infections. That includes ones that are developing in individuals who have immune compromise due to a variety of different reasons.
Dr Berkowitz: Fantastic. Well, glad to have the opportunity to speak with you today. When I was in medical school---and you were my attending, actually, we were just reminiscing, which we probably think was not that long ago, but is now over twenty years ago---there were just two medications for MS, right? Beta interferon and glatiramer acetate. And now we have over a dozen, and it's amazing to think of all the progress in these last two decades, as well as for related diseases like NMO. I don't think we even had the aquaporin-four biomarker, right, when I was working with you as a med student in the early 2000s.
Dr Nath: And that certainly dates me a lot. 
Dr Berkowitz: Both of us. 
Dr Nath: Yeah. 
Dr Berkowitz: Of course, with all these new treatments, these have been amazing advances for our patients, right? But these come with new treatment-related risks to monitor for with the immunomodulatory medications for MS and related disorders. And one of those most important risks is that of infection. So, your article reviews the potential infectious complications of medications used to treat MS, NMO, etc, and also covers considerations related to thinking about vaccines in this patient population. So, as the MS treatment landscape grows, I can say as a general neurologist, keeping up with all these medications and what to screen for and what to worry about and when to vaccinate just becomes more challenging every year. And your article has so many helpful tables, some organized by medicine, some organized by- sorry, medication, some organized by infection, some by vaccines. So, this is gonna be a great resource for our providers to print out and tape up in their clinic rooms. We won't be able to get into all the depth and detail that you have in this article today, but I do want to focus on some of the key points here related to the common medications we use for MS and which infections to think about and which vaccine considerations we might need to keep in mind for these medications. But before we delve into the drugs, I just wanna ask you more broadly, you talk in the article about the challenge of patients with immune-mediated diseases who are on immunomodulatory therapy being at risk for both flares of their disease and for infections; and these infections can present somewhat atypically, right, in immunomodulated hosts, to maybe coin a term you can correct me on, because they can't mount the full inflammatory response. So how do you approach new symptoms in patients on these immunomodulatory medicines as far as distinguishing disease flare from a treatment-related infection? 
Dr Nath: So, I have to say that although a lot of new treatments have come along for MS, and they've really, you know, improved the outcome tremendously and there are so many different options, it has also kept people like me relevant because they cause a lot of various types of infections, and so keeps me in business all the same. But just as you mentioned, there's so many of them, even I have difficulty keeping track of what does what. So, you do need to be able to refer back to published literature, and the tables, I hope, will be quite useful in that regard. You're absolutely right, and you can get new infections, you can get reactivation of existing infections, and you can get atypical presentations of various types of infections that you may not normally think of. So that presents multiple challenges to the treating physician. The other interesting thing about MS is, just as you mentioned, that you already have CNS lesions to begin with. Now, on top of it, you have an infection, so now how to sort out what is the existing disease and what is the infection, it can again become challenging. But one thing is for sure: all these infections are caused by an organism. So, what you really need to do is, the underlying diagnostic is to demonstrate the presence of the organism. Whether you demonstrate it depending on the infection in the spinal fluid or in the brain or, you know, some peripheral organ system, that is going to be key to making the diagnosis. So, all your clinical acumen is good, but that alone may not be sufficient.
Dr Berkowitz: Very good. So, when you see a, a patient now who has a new neurologic symptom in the context of an immune-mediated disease who's on immunomodulatory therapy, what goes through your mind? Are you thinking this disease and this drug, and sort of what are the infections, and does the syndrome match? Or are you thinking, you know, you can't always rely on the imaging to distinguish between, say, a flare of an MS and PML because white matter lesions could look similar? How do you sort of approach this scenario when it comes up? 
Dr Nath: So, you're right. You have to keep an open mind so that even though you know some infections are more likely to occur with certain types of medications, that doesn't mean that others cannot occur. So, I think when you first see the patient, you should not jump to conclusions, but rather have an open mind. But yes, for example, your patient is on natalizumab, the chances of PML are going to be high. It's a very interesting drug. It does not cause immune compromise in the periphery, but what it's doing is preventing these cells from getting into the brain. So, because then it's acting at the blood-brain barrier. So that means that organisms that are already present in the brain have an opportunity to get reactivated. Turns out you don't have a lot of organisms in the brain, except JC virus seems to be one of them that does somehow, in some individuals, manage to reside out there. And so that can get reactivated. It can get reactivated in the periphery and then enter the brain, too. So, where the very specific mutations have to occur in that virus in order to take residence in the brain. That would be a suspicion that you might have, and MRI can be useful in, again, helping you think about that possibility. If you have typical lesions involving the U fibers, they're demyelinating, usually you do not have much edema around them because patient is immune compromised, but certainly within the brain in these individuals. And so, then you need to demonstrate the organism. The demonstration of the organism should be in the spinal fluid and not in the blood because in the virus, it can-- is reservoir in the kidneys and in the lymph nodes, and periodically it'll shed into the blood. Detection of the organism in the blood can be a false positive, but in the spinal fluid, it shouldn't be there unless you have an infection. Or if you cause a traumatic tap, I guess, if a patient is viremic, that's a possibility, but those are extremely rare. So at least for PML, that's the way that you would diagnose it. Now, you can develop, for example, if an individual is on fingolimod, you can get a wide variety of infections. Here it's a totally different type of mechanism of action. Here the cells are trapped within the lymph nodes, so that means now your entire periphery is immune compromised, right?  So here you can get viral infections, bacterial infections, fungal infections. So here, if a patient presents with new neurological symptoms, you have to have a really open mind for all these possibilities. Now, let's say a patient was on dimethyl fumarate, and dimethyl fumarate causes neutropenia early on. So here you have to worry about an individual developing bacterial infections, so latent tuberculosis or bacterial meningitis can occur in these individuals. That's something to keep in mind. It's not that other infections cannot occur with dimethyl fumarate, you can see PML and other things too, but the chances of bacterial infections are greater. So, you got to make sure that you draw all the cultures for that purpose. Similarly, if you're on a complement inhibitor, like a C5 inhibitor or the thing that I could use in NMO, there are the chances of meningococcal meningitis. So, these patients, you need to prevaccinate them before you start these kinds of treatments and look for that possibility. When you suspect bacterial infections, particularly acute bacterial meningitis, there time is of essence. Also, in some of the acute viral infections, for example---herpes encephalitis is another one---you have to be so careful, and if you suspect any of them, even if they're with possibly atypical manifestations, you treat first and then diagnose later, and draw all your cultures, whatever you need to, and just treat them. And these infections can also cause cerebral edema, so one has to be careful about doing spinal taps in these individuals. You want some kind of neuroimaging before you do them. In the days when we didn't have neuroimaging, we used to say, "Okay, if your patient has focal neurological signs or is comatose, you don't do it." But these days, you can get imaging very quickly and very easily. All the-- Because of our stroke management, we've learned how to do them so quickly. So, I think there's little excuse not to do imaging and prevent herniation from occurring. 
Dr Berkowitz: That's very helpful. So, using the information we know about the drug, and we're going to rapid-fire review some of that in a bit to know what infections the patient is susceptible to, but acknowledging that any patient can get any infection, right? Whether they're on particular medications or not. And then if you're not sure, based on the neuroimaging, which as you said, is helpful, but not always helpful in distinguishing between infections and flares or, as you said, in the case of meningitis, encephalitis, early on at least, especially in immunocompromised or immunomodulated, quote unquote, patient might not see the typical imaging. So really, when safe, getting CSF or cultures, PCRs, and other infectious studies too is really gonna be the definitive diagnostic maneuver here. Is that fair summary across the board? 
Dr Nath: I think you said that absolutely right. And you summarized that correctly. And, you know, thing about infection, a lot of neurological diseases are, you know, diagnosed by clinical acumen, like your Parkinson's and Alzheimer's and others. Think about infections is caused by an organism, demonstrate the organism, right? That should be your goal. It doesn't mean that clinical acumen is not important, but here you have an opportunity to demonstrate the organism, so you should depend upon that. 
Dr Berkowitz: Okay. Well, you gave us a nice segue by talking about some of the infections to worry about with some of the medications. So what I'd like to do now for the sort of second half of our interview here is to go through some of the more common medications used for MS, and if we have time, for NMO, and just sort of go kind of rapid fire here, and for each medication, if you can tell us the kind of top infectious concerns and whether when to consider them or what screening needs to take place before or during administration of the medication, and then any vaccine considerations we should be aware of. Some of these will obviously be quite short depending on the medicine. So, going back to the two medications I alluded to earlier that were the only ones in play when you and I last saw each other on the wards when I was a medical student, beta interferon, glatiramer acetate, any infections or vaccine considerations with these medications? 
Dr Nath: No, I think they're probably your safest medications now as far as immunomodulatory therapies are concerned. These two, and IVIG, if you ever use them, are probably the safest, do not require any vaccine considerations, per se.
Dr Berkowitz: Perfect. Okay. So, moving on to fingolimod and others in the sphingosine-one phosphate receptor modulator family, what are the infectious considerations? Any prescreening or vaccination considerations? 
Dr Nath: I think all your patients should be prescreened for antibodies to JC virus, because there is a risk for PML, and those who are positive should be closely monitored. So, it's not an absolute contraindication for using these medications, but they just require closer monitoring. With this class of drugs, PML is of consideration. Also, these varicella-zoster virus infection, yeah, with that you can develop zoster encephalitis or myelitis. It can present with motor symptoms as well, which can be atypical. You don't usually see them otherwise in immune-competent individuals. So, varicella-zoster, sometimes you can develop encephalitis, also vasculitis with varicella-zoster, so one has to be careful. So, getting the shingles vaccine can be actually very helpful to prevent these things. And then some patients can even develop herpes simplex encephalitis also, and that can be extremely atypical. So, they don't- they can involve the basal ganglia, can involve the brain stem and cerebellum. So again, your index of suspicion should be very high. Interestingly, although HSV encephalitis has been associated with NMDA receptor encephalitis, those reports of NMDA receptor encephalitis have not been published yet with NMS patients. Not sure why, maybe they just have been missed. But that doesn't seem to be a major concern. And then there are a whole host of other infections that can occur with this class of drugs, and that can include toxo; fungal infections, particularly crypto. There's a case report of histoplasmosis; hepatitis virus, particularly hepatitis C; and then the poxvirus is a good example. You can get molluscum contagiosum; warts with papillomavirus; you can get atypical mycobacteria; and even Kaposi sarcoma, which is HHV8. So, there's a huge variety of infections with the sphingosine one phosphate receptor modulators. 
Dr Berkowitz: And any- aside from screening for JC virus before initiating these, any- and then continuing to monitor for JC antibody index, any other considerations as far as labs to send, monitoring before or on the drug or vaccine considerations for patients on fingolimod and the others in this category, siponimod, etcetera? 
Dr Nath: Yeah, there are a lot of things to consider. All the details are really available in the chapter if you look at them. But briefly, all the things that one could potentially vaccinate patients for, all these infections I mentioned, one should do so. The timing is critical so that if you can do it before treatment, I think, before starting treatment, that is absolutely important. And you got to give them at least, you know, two to three weeks for these vaccines to take effect before starting your medication. If your patient already arrives on a medication, then you got to play this game of you know, before the next dose, give them again two to three weeks before the next dose and start vaccinating them and get all the vaccines in. Broadly, about the things to worry about the vaccines are you have live vaccines, and you've got the inactivated vaccines or the subunit vaccines. You have to be careful with live vaccines, because if your patient is immunocompromised, that virus can sometimes itself cause harm. For example, you know, yellow fever is one, and there you can develop encephalitis from it. Measles, mumps, rubella, these are all live vaccines. Now, the good thing is that a lot of us have been immunized very early in childhood, but that may not be the case any longer. And so, these things, one has to be very careful with when you're giving live vaccines, that we want to avoid them as much as possible, and individuals are gonna be immune-compromised. But all the others, meningococcus, for example, you should- the HPV vaccines, the varicella zoster vaccines, all these things, you've got to pre-vaccinate and make sure that they have an antibody response to them before starting immunocompromising therapy.
Dr Berkowitz: Perfect. Okay, moving on to some of the other orals. What infectious and/or vaccine considerations do we have with teriflunomide? 
Dr Nath: Okay, yeah. Teriflunomide is a very interesting drug. It's relatively safe. There is concern about the possibility of varicella zoster infection, people have reported that, and also tuberculosis. But PML is extremely rare, if not at all, and we haven't seen herpes encephalitis quite yet. 
Dr Berkowitz: Got it. How about dimethyl fumarate?
Dr Nath: Yeah. So dimethyl fumarate is... as I mentioned earlier, it's interesting because it causes this neutropenia. It's transient, but it occurs early on, and these patients can be at risk of PML, although small. They can develop varicella zoster virus infection, herpes encephalitis, and also fungal infections. For example, cryptococcal infection has been reported with dimethyl fumarate.
Dr Berkowitz: Okay. We've spoken a bit about natalizumab and PML, and you have extensive information on this in your article, and I'll defer the reader to that. But for natalizumab, what are the key points every neurologist should know about natalizumab and PML as far as from the practical perspective, screening, frequency of screening, when to worry, when to not use natalizumab at all in the first place based on what you find in your screening for JC virus? What are the key points every neurologist should know? 
Dr Nath: Uh, yes. You bring up an important point, and that is all patients should be monitored for JC virus. If they're JC virus-negative, so that's your most ideal patient to go on natalizumab, but that doesn't mean they cannot get infected with the virus. In fact, there's an interesting study claiming that, you know, patients, when they get these infusions, they're all sitting in the same room getting infused. Some have JC virus, some don't have JC virus, and so there's the potential that we may be aiding the transmission here in some way or another. The virus is an interesting one. It comes out in urine, and then it's spread through oral contamination, gets into the tonsils, and then spreads from there to your marrow and resides in the kidney and the marrow, as well as the lymph nodes, forever. So, you, you have to monitor these patients to see that during the course, even if they're negative, they could turn out positive. So, every six months or a year, an antibody test should be done on all patients irrespective. If a patient already has antibodies, that's not an absolute contraindication. It just means you've got to monitor them closely for development of new symptoms, and if, whenever there are new symptoms, don't just assume this is due to MS, but just make sure the MRI is done with and without contrast. The- and if there's still a suspicion, that you do a CSF evaluation for JC virus. Just detecting, looking for JC virus in the blood, a rising titer is another thing that can help you. And so, the titer is also important. And the reason you have rising titers is it means that there's an infection that's already occurred in the brain, and the immune system is reacting to that infection by increasing titers. But that alone is not sufficient to make the diagnosis. You still- that gives you an index of suspicion. You've got to then do the MRI and the spinal tap to, you know, be absolutely certain. So, each patient is a little bit different, so the way you monitor them is going to depend on where they are. You know, if they've had prior immunomodulatory therapy before starting natalizumab, or if they're on natalizumab for more than two years, then the chances of PML are much greater, so you may want to monitor them more closely. Uh, they never had any prior immunomodulatory therapy, you're just starting natalizumab, maybe once a year is sufficient. So, I think you've got to tailor it depending on what your risks are for each patient.
Dr Berkowitz: Perfect. That's very helpful. And again, you write extensively about PML and natalizumab and PML considerations in your article. So, for a more detailed and in-depth discussion of what we just discussed, definitely hope readers will take a look at your article. Okay. Last but not least---certainly not least, 'cause we're using these probably, it seems, the most commonly in many places I've worked---rituximab, ocrelizumab are B-cell therapies for MS. What are some of the infectious and vaccine considerations related to these infusion medications? 
Dr Nath: So, there's concern for PML with anti-B-cell therapies also, maybe not to the same degree as natalizumab, but the same principles should be applied. A lot of people think that these are relatively safe. I don't think so. I think we see enough number of patients on B-cell therapies with PML. So, I would use the same caution because these infections are... you know, can be fatal. So, one should be very careful, even with anti-B-cell therapies. And just with natalizumab, you also have the risk of VZV infection causing shingles. HSV1 has been reported, but there's another interesting complication that has been reported with anti-B-cell therapies, and that is severe West Nile encephalitis. And as mosquitoes-borne diseases are getting more and more prevalent, and we're seeing West Nile cases erupting every summer, I think one's got to be, you know, very cognizant of the fact that this can occur. These patients should take precautions to prevent mosquito bites from occurring and not expose themselves to areas where they could be at risk for it. Unfortunately, there is no vaccine for it and no specific treatment for West Nile. So, all one can do is use prevention strategies for mosquito bites. 
Dr Berkowitz: Yeah, I'm glad you mentioned that. I think the only really truly severe neuroinvasive cases I've seen of West Nile virus have indeed been in patients who were being treated with B-cell therapy. Not, if I'm remembering correctly, for immune-mediated disease, but for a lymphoma, so probably other confounding factors there. But yeah, it's a disease we learn about and think about, but I've only seen the most severe cases in patients who had abnormal immune systems, so I'm glad you flagged that. This has been a very helpful discussion, and I've learned a lot from you. I learned a lot from your article, just as I did when you were my attending some 20-something years ago on the wards when I was a medical student. So, it's good to continue learning from you through your writing and research, and today from getting to talk to you again. I encourage our readers to read your article and to bookmark those tables for when these considerations come up for your patients on these immunomodulatory therapies and you're wondering which infections to worry about and how to manage vaccines in this patient population. So again, today I've been interviewing Dr. Avi Nath about his article on vaccine considerations and infection risk in multiple sclerosis and related disorders, which he wrote with Dr. Amit Bar-Or. This article appears in the April 2026 Continuum issue on multiple sclerosis. Be sure to check out Continuum Audio episodes from this and other issues, and thank you again to our listeners for joining today. 
Dr Nath: Thank you so much, Aaron, for that wonderful interview, and I'm extremely proud of all your accomplishments over the last 20 years. You've done an amazing job, and it was such a pleasure to see you and to be able to do this interview with you. Thank you again. 
Dr Berkowitz: Thanks. That means a lot. I never would have imagined- we won't say 20, how many, but 20-something years ago as the medical student looking up to you and all your expertise on these infections and all of your research that led to so much of our understanding on these, that I would find myself interviewing you two decades later. So, for all the students listening, you never know where you'll end up, but I appreciate your very kind words. 
Dr Nath: That's what we hope for all our students. Thank you so much. 
Dr Berkowitz: Thanks again. 
Dr Monteith: This is Dr. Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.

There are many treatment options for people with relapsing MS. Patients should be carefully monitored to assess treatment response, and a change in treatment approach should be considered if safety concerns emerge.
In this episode, Teshamae Monteith, MD, FAAN, speaks with Ellen M. Mowry, MD, MCR, and Daniel Ontaneda, MD, PhD, coauthors of the article "Treatment of Multiple Sclerosis" in the Continuum® April 2026 Multiple Sclerosis and Related Disorders issue.
Dr. Monteith is the associate editor of Continuum® Audio and an associate professor of clinical neurology at the University of Miami Miller School of Medicine in Miami, Florida.
Dr. Mowry is the director of the Multiple Sclerosis Experimental Therapeutics Program and a professor of neurology at The Johns Hopkins University School of Medicine in Baltimore, Maryland.
Dr. Ontaneda is the director of research at the Mellen Center for Multiple Sclerosis and a professor of neurology at the Cleveland Clinic Lerner College of Medicine of Case Western Reserve University in Cleveland, Ohio.
Additional Resources
Read the article: Treatment of Multiple Sclerosis
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More about the American Academy of Neurology: aan.com
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Host: @headacheMD
Guest: @EllenMowryMD
Full episode transcript available here
Dr. Monteith: There are so many new treatment strategies for multiple sclerosis, which is a blessing, but it does come with the complexity of really just trying to nail down the approach. I just got finished talking to Drs Ellen Mowry and Daniel Ontaneda about their article on treatment of multiple sclerosis. We discussed relapses, weighing escalation versus early high-effective treatment and progressive disease. This is a must-listen-to podcast. I hope you enjoy it as much as I enjoyed talking to them. 
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. Monteith: This is Dr. Teshamae Monteith. Today, I'm interviewing Ds Ellen Mowry and Daniel Ontaneda about their article on treatment of multiple sclerosis, which they wrote with Dr. Darin Okuda. This article appears in the April 2026 Continuum issue on multiple sclerosis. Welcome, both of you. How are you? 
Dr. Mowry: Great. And thank you so much for having us. 
Dr. Monteith: Absolutely. So, why don't you both introduce yourself? 
Dr. Ontaneda: All right. My name is Daniel Ontaneda. I'm a neurologist at the Cleveland Clinic. I spend the majority of my time doing research, but I still dedicate about a day a week to seeing people with MS in clinic. 
Dr. Mowry: I'm Ellen Mowry. I'm also a neurologist, but practice at the Johns Hopkins University. And similar to Dan, I mostly work on research, but also have an active clinical care component, taking care of people with MS. 
Dr. Monteith: Well, thank both of you for writing this article and being on our podcast. I assume you guys have probably known each other for quite a while now. 
Dr. Mowry: Yes.
Dr. Ontaneda: Yes.
Dr. Monteith: What inspired you to get into multiple sclerosis research and then clinical care? 
Dr. Ontaneda: I always loved neurology, and I think a lot of us who go into neurology are attracted to the complexity of the human brain and how the nervous system works. But what really hit home to me was a family member of mine who had multiple sclerosis, and he was being treated in a time where we really didn't have super effective disease-modifying medications. And so, as I went through my medical career, I always kind of kept an eye on what was happening with multiple sclerosis, and I started my training at a time where it was really flourishing in terms of the medications available, so that's what inspired me to go into MS. It's a disease that we can definitely treat, and you can change outcomes for people. So, that was it. 
Dr. Monteith: Yeah, that personal experience can be very impactful. 
Dr. Mowry: My journey started, actually, because I was thinking about whether I wanted to be a physician at all, and I happened to land, just after high school, a position with a neurologist who happened to mostly focus on multiple sclerosis and taking care of folks with multiple sclerosis. And by the end of the summer, I knew I wanted to go to med school and I wanted to be a neurologist and I wanted to work with people with MS. I thought I would be a clinician exclusively, but I think as time went on and I started to hear the consistent questions that people I served were asking in the clinic and realizing that those questions could be turned into research projects that could address their concerns, I moved more and more towards research.
Dr. Monteith: Great. There are a lot of really detailed information in the article, so I think that research mind is very useful, and I see that in the writing. Why don't we talk about the goal of the article?
Dr. Ontaneda: So, I think the goal of the article was to set out kind of what the large view of what treatment for multiple sclerosis looks like. And, you know, many times we divide the treatment of multiple sclerosis into these large pillars, and I think that's what we did in the article. The first was, you know, what do you do with a person who has an MS attack or relapse? The second is, what medications do we use to treat the relapsing forms of multiple sclerosis where there is a lot of acute inflammation, focal inflammatory lesions that are occurring? And then the final one is, what do you do with individuals who have a more progressive form of the disease where they're accruing disability slowly and gradually?
Dr. Monteith: And what were some of the main points?
Dr. Mowry: Dr. Okuda provided a really nice section on the treatment of acute relapses in multiple sclerosis, and it's important to understand what we talk about when we are saying "relapse". For people with MS, many symptoms can fluctuate and occur and then get better over time, and sometimes people with MS use the same term of "relapse" to describe those symptom fluctuations. As neurologists, when we're thinking about relapse, we're really trying to think about symptoms that can be attributed to new focal inflammatory events somewhere in the central nervous system. Typically, these are accompanied---if you were to get an MRI at the same time---by a new lesion or MS spot, as I like to call them, on MRI scan. And so, it's important to distinguish when somebody is talking about symptoms, whether they are true new symptoms that could be mapped to a place in the central nervous system. Because alternatively, a lot of people who've had attacks or relapses in the past can have what we call pseudo-relapses, and these are essentially recrudescence of old symptoms, typically in a similar pattern as what had occurred in the past. And these can be brought out by things like fever or infection, sometimes stress. And pseudo-relapses are not thought to be due to new development of immune system-induced injury and therefore would be less likely to respond to treatment; and in fact, treatment may be contraindicated for those events. We also talked a little bit in that article about how relapses are treated, talking about the use of high-dose steroids for true new relapses, but also kind of cautioning that those are not necessarily free of concerns, especially if you have a pseudo-relapse or there could be an infection going on. And that ultimately, the decision as to whether to treat a relapse really is a shared decision-making because it's thought that although the steroids can speed up recovery from a relapse, they may not have a major impact on ultimate recovery. And so, a lot of the shared decision-making comes in here because for a mild relapse, you might choose to forego a course of high-dose steroids. 
Dr. Monteith: Daniel, any other main points? 
Dr. Ontaneda: Yeah. On the side of treating relapses, I think one of the other things that probably has changed a lot, at least during the course of my training, is that in the past, whenever we had identified a relapse, as Dr. Mowry has clearly defined, we would typically treat with intravenous high-dose corticosteroids, typically with methylprednisolone. And that was kind of our go-to. We would either do it in an infusion center or we would set it up with home care. And I think one of the things that our field learned over, I would say, the last five or ten years is there's an abundance of studies that show that you can give that same dose of methylprednisolone. Rather than giving it IV, you can give it orally. No pun intended, as I tell my patients, a lot of pills to swallow because we use fifty-milligram prednisone pills, and they have to take 1,250 a day. The pharmacy always pushes back on that many pills, but really the advantage of being able to take steroids orally that way for three to five days is really, I think, one, better for people with MS because they can do it in the comfort of their own home, and two, I think also when you look at the costs associated with that treatment, it is the most cost-effective option.
Dr. Monteith: And what are some of the latest developments that you're really excited about that weren't in the article? 
Dr. Mowry: A lot of the article focused on the approach to treatment of people with what we've traditionally called relapsing/remitting multiple sclerosis. So, this is the kind of MS that traditionally presents with a relapse or an attack initially, although some of that nomenclature is changing, actually. And the article focused a lot on the strategies surrounding treatment of somebody with newly diagnosed relapsing MS, and thinking about this vast number of disease-modifying therapies that are available to people with MS and their clinicians, and how to think about the strategy with respect to largely centered around the efficacy class of the medication, whether people should take an approach of using a higher-efficacy therapy---meaning a medicine that in clinical trials was more likely on average to suppress relapses as well as new lesions---or whether there's still a good argument for the case of using an escalation approach, using some of the more modest efficacy medications that also probably in general have lower risks, monitoring for response to treatment and changing if the medication isn't working. And so, there's still a lot of debate in the field, I would say, even though many people have moved towards a one-size-fits-all kind of approach. I think there's still a lot of debate in the field about the evidence underlying that. And, you know, full disclosure, Dr. Ontaneda and I are each running parallel and very complementary clinical trial programs to address this very question, the results of which should be available within the next year, year and a half. 
Dr. Monteith: Well, we can't wait that long. Give me some clinical pearls to how we initiate these modifying therapies. Like, what are the pearls that we need to have in our mind? 
Dr. Ontaneda: Yeah. I think when we think about starting the disease-modifying therapy in an individual who has an active form of multiple sclerosis, I think, you know, one of the cornerstones I would say of making that decision is shared decision-making. I think we tend to sit down with the patient and analyze the data that we have at hand, what we know about their multiple sclerosis, and we use several factors to inform how likely we think their disease is gonna be active or potentially might not respond to the initial treatment you give. And we look heavily at the MRI. The MRI is really a useful marker because it shows us, one, how many lesions a person might have---both, you know, where those lesions are and also kind of the amount of lesions. Lesions, certainly, that are in the spinal cord, a very large burden of diseases. A lot of active lesions, which we determine by the presence of contrast-enhancing lesions, really helps us inform on disease severity. I would say that was our number one tool that we use to decide and help us decide how we think that person's MS is gonna do over time. And then the second thing that we put into the equation also is, you know, how well do we think this person is going to tolerate our medications? All our disease-modifying medications act through suppression of the immune system, and we know that that carries some risks associated with it. Some of those risks are stuff like infections. Some of those can be simple infections that really don't have major consequences, but some of them can be quite serious, including the need for hospitalizations or prolonged antibiotic treatment courses. And so, we also look at what, you know, the underlying risk of a person has for infection. This kind of is determined by, one, A, how many infections they've had up to date, and also how much disability they had. I would say in our average patient who when we see them, they're probably typically pretty young, in their twenties, thirties, forties, they typically don't have a lot of infectious risks. And therefore, I think there's kind of a move to saying, "Well, actually their risk of infections is quite low." And we put that together with, you know, also what the preference of the patient might want. So, do they prefer to take a pill, for example? Do they prefer a medication where they receive that via infusion every six months and they don't really have to think about it? There are some people that don't like going into a hospital, and they might prefer an injection type of those medications. And so, after a complex discussion of all those factors, we take into consideration how much risk the patient wants to take as well, and we come up with a rational choice of a couple of medication options. So, I think it's challenging sometimes because we have over two dozen medications. There's the risk of you saying, "There are these twenty-four medications, you can pick one." And I think our job as neurologists is to kind of pare those down, talk about, in a person like yourself, these are the two or three medications that I would recommend using. Why don't you review them? And then we bring them back, and we kind of make a final decision with, one of the key factors that I think is important to remind people is that you're gonna start this medication, and we are gonna monitor to make sure it's working. We're gonna monitor to make sure you're tolerating it well. And although it's an important, the first decision you make, I think one key theme that we tell people is, we can revise our strategy whenever we like. We just have to think about it and do it in a way that we think is gonna make sure that their MS is under the best control. And then we think about the ultimate goal of treatment, which, in multiple sclerosis, is the absence of any attacks and also the absence of any new lesions on MRI. And that's where whether you are offering more of the high-effective medications or more moderate- or low-efficacy medications, that's where there's a little bit of controversy still in our field, and that's what our trials are trying to answer. 
Dr. Monteith: Excellent. So now we've selected a particular option- and I love those points with shared decision-making, using the MRI to guide and then kind of risk tolerance related to infection. But now a patient's still having relapses, and I know the goal is zero, but, you know, there's some margin. What are the pearls to advance to more high-efficacy therapies? 
Dr. Mowry: Yeah, that's a great question. Dr. Ontaneda in the article actually talked about the literature surrounding monitoring for breakthrough disease and when to say this much is too much, and there's actually not a definite right answer. It's clear that more active disease early in the course is probably more of concern than, say, developing, you know, a new spot in your fifties or something to that effect. So, different people have different thresholds. I know at our center, we tend to be pretty on top of making changes for breakthrough disease. So, what we typically do is reimage people about six months after they start a medication to establish a new baseline. And sometimes, because of delays in starting or because the medications take a while to kick in, there might be a new spot or two. So, if that's the case, I really only get concerned if the spots are also taking up the dye or enhancing to indicate they're really quite recent, and I think, "Ugh, that's not something I'd like to see six months after starting a medication." And so that otherwise is sort of the reference scan, moving forward, to evaluate the medication, and I have a very low threshold for changing, particularly if somebody is on a moderate-efficacy therapy. To me, I think, well, our goal of trying the moderate efficacy therapy is essentially to see if we could get away with a medicine that is probably, on average, safer and that will still work for your MS. But if the answer is no, I personally don't like to stick around too much on them. One caveat I would say is that if somebody develops what appears to be a new lesion or spot on higher-efficacy therapy, before presuming that that new area of activity is a definite new MS event, I always like to rethink carefully, did I get the diagnosis correct? Or could this be an early infection such as, you know, progressive multifocal leukoencephalopathy in people on natalizumab in particular? Because I see breakthrough activity so rarely in people on higher-efficacy therapies that I just like to rethink my diagnosis and the differential prior to making switches to, typically, another higher-efficacy therapy in that case. But that, again, is a little bit of shared decision-making. It's sometimes contextual. If a person is using a self-administered medication and they have a little breakthrough, sometimes you can solicit some history, saying, "Oh, I actually kind of stopped taking it for a few weeks because something was going on, and I really want to retry." And that's very reasonable as well. Dan, do you have any other thoughts? 
Dr. Ontaneda: No, I think I agree. That's really close to how I practice myself as well, and the majority of people at my center. I think that we are learning that when you start a treatment, many times---depending on how deeply you look---you can find evidence of ongoing disease, and that's something that we struggle with. It's almost like we have tools to treat inflammation in terms of new MS lesions and new relapses. And so, when those are present, it's pretty clear that you probably have to switch medication. I think a slightly trickier issue is when, for example, you have a person who might be stable. They don't have an attack. But you notice that they're worsening, and they tell you they're worsening. I think our ability and tools for that is a little bit harder, and we recognize that that can actually happen fairly early in the disease. And that's why we're trying to rethink this mantra that we've had for many years, where we kind of divide MS up into relapsing and progressive, and we see people develop progressive MS 10 to 15 years after they've had a relapsing form of the disease. So, I think that's just a reality of clinical practice. And we don't have as many tools to treat that gradual worsening, which is kind of what the rest of our article spent some time talking about.
Dr. Monteith: You've also written about the clinical trial long-term extension studies. And what are the few points that you take away from the emergence of these types of publications over the past few years?
Dr. Mowry: Yeah, well, long-term extension studies can be really helpful to understand whether the findings that are evidenced during the randomized portion of trials themselves continue into a longer term. And for people with MS, understanding these data can be really helpful because, particularly when we're looking for impact of a given treatment or a strategy on disability worsening, often it takes longer than the short-term portion of the trial to truly understand if the medication or strategy has an impact on insidious worsening that Dan is speaking about. Many trials have demonstrated a short-term benefit, but we think a lot of times that benefit is probably because of the reduction in relapses, which sometimes leave a permanent mark on neurologic function. But the extension studies are trying to understand a little bit more about whether the effect on disability worsening is sustained, and also to look a little bit more deeply at long-term safety, especially when it comes to medications that do increase the risk of infection. The caveats, though, in interpreting those types of studies are that people drop out, and so probably the people who drop out of those studies are really different. They may be either less disabled and they think, "Oh, you know, I'm done. I feel good." Or potentially more disabled and they think, "Ugh, I have more things to do I've got to take care of. What's going on?" And so that kind of dropout can produce some bias in interpreting the results. Dan, any other thoughts? 
Dr. Ontaneda: No, I think that's spot on. I mean, I think that when we're trying to decide on what general philosophy to use, right? Like, you're seeing a patient for the first time. They've recently been diagnosed with MS, and you have... you know, I kind of bin them into three options. You can start a low-efficacy, a moderate, or a high-efficacy medication. And the first piece of information you could use is clinical trials, and Dr Mowry very clearly identified why some of that data might be a little bit biased and isn't, you know, completely applicable to the patient who's in front of you. The second thing that we might look at is observational data, and there's a wealth of observational data that shows that, in general, people on higher-efficacy medications tend to do better over time. But one of the challenges we have is that there's always biases related to those observational study designs. And so, I think you have to interpret them with a little bit of caution because there are reasons people start specific medications in people. And when you look at them in a purely observational study, even if you do some fancy way of addressing those biases, such as propensity, there always is the possibility of some residual bias. You know, that's part of the reason why we're doing the trials that Dr Mowry described, because we really need kind of long-term evidence to show that these medications actually can affect disability ten, twelve years after started. And I think pragmatic clinical trials, like the ones we're running, are really gonna be the key to answer those questions. We all have our favorite approaches right now, but I think that the data to actually demonstrate what's best for people with MS is really needed. 
Dr. Monteith: Great, and there's so much in this article. I mean, we didn't even touch on radiological isolated syndrome, monitoring MS therapeutically, and treatment of progressive MS. Any final take-home points? 
Dr. Ontaneda: Yeah. Maybe I will touch a little bit on the side of progressive MS, because it has been, you know, the MS that we historically have not been able to treat as much. So, we described there's over two dozen therapies approved for relapsing forms of MS. For purely progressive forms of MS that don't have any evidence of activity, we really only have one approved therapy, and it appears that that therapy actually does work through active inflammation anyway. And in the article, we highlighted examples of studies that have been negative, but also some recent examples of studies that have been positive, specifically with a new class of medication called BTKI, or Bruton tyrosine kinase inhibitors. We just recently heard of a second molecule that also had positive results in this realm. So, we're excited that, you know, in the next four to five years- 
Dr. Monteith: I'm sorry. Can you just go ahead and say what that molecule...You're leaving people hanging. 
Dr. Ontaneda: One molecule is tolebrutinib, which already has a positive study in secondary progressive MS in individuals without activity. And then the second compound that has been studied with positive trial results, we only have summary results from that, is a medication called fenobrutinib. And we think these two compounds that are part of a single class, the hope is that maybe they can address some of that gradual worsening that occurs in MS. And then the question comes whether we should use those from the get-go or if we should just use them later. So, a whole sort of variety of different questions. But I think important to call out for clinicians that this area where we had no available treatments for so many years might be changing. 
Dr. Monteith: Well, thank you both. I really loved this conversation. I learned a lot listening to both of you, and I look forward to your clinical trial results. 
Dr. Mowry: Thank you so much for having us.
Dr. Ontaneda: Thanks so much. It was our pleasure.
Dr. Monteith: Again, today I've been interviewing Doctors Ellen Mowry and Daniel Ontaneda about their article on treatment of multiple sclerosis, which they wrote with Dr. Darin Okuda. This article appears in the April 2026 Continuum issue on multiple sclerosis. Be sure to check out Continuum Audio episodes from this and other issues. And thank you to our listeners for joining today.
Dr. Monteith: This is Dr. Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.

Although rare, recognizing NMOSD is crucial for improving patient outcomes through correct diagnostic and treatment approaches. Reports of atypical forms and increasing knowledge of clinical, imaging, and laboratory-specific features are fundamental for the accurate recognition of this condition. Research on targeted therapies and biomarkers measuring and predicting disease activity will improve NMOSD management.
In this episode, Gordon Smith, MD, FAAN, speaks with Sara Mariotto, MD, PhD, coauthor of the article "Neuromyelitis Optica Spectrum Disorder" 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. Mariotto is a neurologist in the Neurology Unit in the Department of Neurosciences, Biomedicine, and Movement Sciences at the University of Verona in Verona, Italy.
Additional Resources
Read the article: Neuromyelitis Optica Spectrum Disorder
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Host: @GordonSmithMD
Full episode transcript available here
Dr Smith: Neurology is an increasingly therapeutic specialty, and across many of our subspecialty areas, lots of new drugs are being approved. Are you interested in learning more about a historically disabling disorder for which we now have a spectrum of new therapies that, if used appropriately and promptly in the right clinical situation, promise to dramatically improve patient outcomes? If so, keep listening. My name's Dr Gordon Smith. Today I'll be talking with Dr Sara Mariotto about her article on neuromyelitis optica spectrum disorder or NMOSD, which she wrote with Dr Romain Marignier. This article appears in the April 2026 Continuum issue on multiple sclerosis. 
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 Sara Mariotto about her article on neuromyelitis optica spectrum disorder or NMOSD, which she wrote with Dr Romain Marignier. This article appears in the April 2026 Continuum issue on multiple sclerosis. Sara, welcome to the podcast, and maybe you can start by introducing yourself to our audience. 
Dr Mariotto: Yes. Thanks, Gordon. I'm Sara Mariotto. I'm a neurologist, and I work at the Neurology Unit, University of Verona, where I do both clinical diagnosis and research into neuroimmunology---so, in particular, autoimmune encephalitis, NMOSD, and MOGAD. 
Dr Smith: Well, this is a super exciting area. Whenever I hear about NMOSD, I think of one specific patient I had, and I always think of her when I come across something like your article, which is really fantastic. So, before we dive into the details, I wonder if maybe you can just explain to our listeners who aren't up to speed on what NMOSD is, what the disorder is, and maybe why it's so important that all of our listeners learn how to recognize it quickly and get people started on therapy. 
Dr Mariotto: Yes, sure. So, neuromyelitis optica is an inflammatory autoimmune CNS disorder usually associated with aquaporin-4 antibodies, although there are a few cases, around 10%, who can be antibody-negative. And I think it's very much important to have in mind this disease and recognize it because it can be severe, as you pointed out; can present with very severe optic neuritis, myelitis, the brain stem, or area postrema syndrome. So, it can be really severe, affect quite young people around 40 years of age---although it can affect also the pediatric population and elderly people---and, importantly, it can be treated. It's very much important to treat this patient in the acute stage very quickly with steroids or plasma exchange in addition, and then to start a chronic treatment. So, we have treatment for this condition. So, it's very much important to, to recognize it quickly and treat the patient properly. 
Dr Smith: So, I wonder if we can talk a little bit about the diagnostic criteria and boundaries of NMOSD, right? So, someone who comes in with bilateral op- severe long segment optic neuritis or long segment myelitis, we think about it. But what are the boundaries? Should we be looking for this, for instance, in someone who comes in with a unilateral optic neuritis or looks like typical multiple sclerosis? Is it important to get aquaporin-4 antibodies in those patients? What do the diagnostic criteria say about this? 
Dr Mariotto: So, I wouldn't test aquaporin-4 antibodies in all patients with demyelinating conditions because although aquaporin-4 antibody assay is very specific, as for all assay and all antibody testing---also for MOG antibodies, for example---some false positive results can come out. So, I would suggest to test aquaporin-4 antibodies not in typical MS cases but in those who could be suggestive for not being MS, so in all those cases with atypical optic neuritis and myelitis or other syndromes. For those cases, it's important to test aquaporin-4 antibodies, but I wouldn't test them in all typical, classical MS cases. As I said, it's quite specific, the assay, so it's uncommon to have false positive results, but it can be. 
Dr Smith: Serum, CSF, both? 
Dr Mariotto: So, for aquaporin-4 antibodies, they're usually present in serum. They can be positive also in the CSF. And there are a few reports of isolated CSF positivity. But if we analyze larger samples volume, then it becomes clear that isolated CSF positivity is so, so rare that it's not recommended to test them in the CSF when serum is negative. So, for aquaporin-4 antibodies, the recommended matrix of testing is serum, which is different for MOG, which is not the topic of our article but is important to mention because MOG antibodies should be tested in serum and CSF. But aquaporin-4, I would recommend to test serum. 
Dr Smith: What are the boundaries between MOGAD and NMOSD? And you talked about the differential testing of antibodies, which I was going to ask about. But when should we think of NMOSD relative to MOG?
Dr Mariotto: Yeah. There are aspects which are the one mentioned in the criteria, highly suggestive for NMOSD. But the clinical spectrum can be similar to that of MOGAD. Usually, although there are some clinical aspect---like, for example cortical encephalitis or ADEM, which is more typical for MOGAD, or others like area postrema syndrome, which are more typical of NMOSD. The spectrum can be similar among the two conditions, so that's why in our clinical experience, usually they ask both aquaporin-4 and MOG antibodies in patients. It's- for experts, it can be easy to differentiate the two conditions, but for nonexperts can not be so easy. 
Dr Smith: Can you define area postrema syndrome? I think not all of our listeners see that every day. 
Dr Mariotto: Yeah, sure. This is a syndrome which is highly suggestive of NMOSD. That's why I mention it. And it's characterized by nausea, vomiting, hiccups are known as the syndrome. And it is very, very suggestive because of the expression of aquaporin-4 in that area of NMOSD. That's why I strongly recommend for all patients who comes out to have this syndrome to test for aquaporin-4 antibodies. MOGAD is hardly ever positive for that, so I think that whenever you see a patient with that syndrome, you should think about NMOSD. 
Dr Smith: I'm just curious, aquaporin-4 is a water channel, which is kind of an interesting concept. Our conversation, I really want to make sure we give clinically important information to folks, but it's so curious to me at least, how does this actually result in a inflammatory demyelinating syndrome? For a simple neuromuscular guy, what's the immunopathogenesis of this? 
Dr Mariotto: Yeah, the immunopathogenesis is quite complicated, as in all CNS disorders. And of course, aquaporin-4 antibodies are the main focus, but they are not the only one. As you said, aquaporin-4 antibodies have a target, this water channel, which is at the basis of the disease, and they are produced by the interplay between T cells, B cells, and plasma cells. But then also eosinophils, macrophages, cytokines, and chemokines are involved, enter the CNS, and then another important component is complement, which is highly activated in this disease. At the end, we have astrocyte damage because astrocytes are the main target of the disease, but also axon and myelin are involved. So, it's a quite complex pathogenesis based on the antibodies, but not only on that. 
Dr Smith: And this will become important when we start talking about treatment. There seems to be a recurring theme of long segment demyelination, right? Optic neuritis is typically a large percentage of the length of the optic nerve, and obviously the myelitis se- more than three segments. Do you see other long segment areas of CNS demyelination, corpus callosum or things like that? Any ideas why that is, if that's true? 
Dr Mariotto: Of note, this is quite interesting because usually when we have NMOSD, we have a longitudinal involvement, especially of the optic nerve and spinal cord, while brain lesions are quite different. Like, we usually do not have the typical Dawsen fingers-like lesions that we have in MS, for example, or the classical periventricular or subcortical extensive lesions that we can see and we have in mind when we think about MS. In some cases with NMOSD, the brain is completely negative, so we do not see anything. And Dawsen lesion's quite suggestive of NMOSD. So, you're right. I mean, this is related partially to the expression of aquaporin-4, and that's why we have this typical involvement also for area postrema, for example, and maybe also our other examples of clinical aspect that we can see in these conditions. But it's basically linked with the expression of aquaporin-4, which is the main target of the disease. And that's why usually the brain doesn't show so much involvement as we can see in MS, for example. 
Dr Smith: I was actually really interested in some of the unusual manifestations or phenotypes, and I don't want to get into arcadia, really, but which of these should our listeners be familiar with that would really suggest that they should be thinking about NMOSD beyond the area postrema and other features that we've already talked about that are part of the core criteria? 
Dr Mariotto: Yeah. I mean, I think that the encephalic syndromes or also ADEM, which is most typical of MOGAD but can be observed also in NMOSD or PRES, for example, are syndromes that can be considered in patients with NMOSD. There are the typical ones, which are the ones showed in the criteria, but whenever we have a brainstem involvement or, like, these encephalic syndromes or also PRES, we should think about NMOSD also. 
Dr Smith: Another area I was interested in are red flags. In your article, you talk about red flags that might suggest an alternative diagnosis, right? And then this presumably is particularly important in seronegative patients, which 10% is not a reasonably high number, I suppose. What are red flags we should be thinking about for some other diagnosis? 
Dr Mariotto: Yeah. I would here mention two very important red flags. The first one is a very hyperacute onset. Usually these conditions, these inflammatory conditions have a subacute onset, so whenever you have a very, very acute onset, you should think about something else. This can occur sometimes also in NMOSD, but hardly ever occur. Like, a very acute myelitis, the first thing we should think about is a vascular origin, for example, with a lot of pain and not about NMOSD, although sometimes the differential diagnosis is not so easy. The second thing is a progression independently of relapses, which hardly ever occur in NMOSD. Usually in NMOSD, we have the onset, and then we have a relapsing disease course. That's why we have to treat patients always and not to stop treatment. But we do not have progression in the meanwhile, while we can have, for example, this in MS. Same thing is for MOGAD. So, these are two things that I think is very much important to keep in mind. 
Dr Smith: I want to pivot to talk about treatment because that's been super exciting. But rumor has it there are new diagnostic criteria coming for NMOSD in the next year. I bet you know a bit about those. Can you give our listeners any indication about kind of where the puck is going on this? Not so much what the criteria are specifically, but what sort of diagnostic challenges are the new criteria going to help us with once they come out? 
Dr Mariotto: Yeah. So basically, we are working on that, so you will read them in the next future. This is the good point of the conversation on the new criteria. And we work a lot on the definition, on the new definition and nomenclature of NMOSD; on the definition of seronegative NMOSD, which is also quite tricky; and then on the assay we should use to test aquaporin-4 antibodies, and also on potentially new syndromes which should be included into the main feature of the disease. But hopefully you will read about this very soon. 
Dr Smith: Looking forward to it. And Continuum Audio listeners, you heard it here first, so thank you. Let's pivot to treatment. This has been super exciting, and I wonder if the way to approach this is to start with acute management and then sort of chronic management. Would that make sense? 
Dr Mariotto: Sure. 
Dr Smith: Let's say I go on service on Friday, and I have a patient who comes in with positive aquaporin-4 and bilateral optic neuritis. What's the acute approach to managing that patient? 
Dr Mariotto: So, the first approach is to administer intravenous steroids, but I would not wait to escalate to plasma exchange. There is quite good evidence that we should treat the patient with additional plasma exchange very quickly, and every day of delay of plasma exchange can cause increased disability. So, we should treat patients with steroids first, and then if we are not satisfied by the recovery, soon start with a plasma exchange. There is also some evidence, although less, for IVIG, but it's important to try to treat them very quickly, even if it's Friday, you know, there is the weekend and so on. But I think it's very much important to start with steroids after excluding other infectious causes or so on, and then to start quickly with plasma exchange. The main problem could be that we do not have the results of the antibody yet. 
Dr Smith: Right. So, let me ask that question. You know, let's say my patient comes in on Friday, and clinical syndrome that really looks like NMOSD, and we're waiting for the aquaporin-4. There are many places where it's hard to get plasma exchange over weekends. And so, in that setting, are you better off doing the steroids over the weekend then PLEX on Monday, or should we just give IVIG because maybe it's as good as PLEX? What's your advice there? I'm trying to get ready for Friday because I know one's coming in. 
Dr Mariotto: That's true, that's true. Usually they come on Friday or Saturday. I think it's acceptable to have three days of steroids and see how the patient improves, and then after three days to start with plasma exchange. Actually, we have a very good improvement if we start between three and five days after onset. So, I think waiting for three days is acceptable just because we can see if the steroids work properly or not, and then we can quickly start to plasma exchange. But I would not wait, like, 10 days, you know, before starting with a plasma exchange, and I would not wait for antibody results. 
Dr Smith: Got it. Super helpful. And I'm actually not joking around, I learned recently that I have a reputation among our residents for having lots of optic neuritis when I'm on service, which I think is sort of karmic justice for being a peripheral nerve expert. But let me ask another question. So, let's say we do that, and the patient gets three or five days of pulse methylprednisolone and five courses of PLEX, and they're not doing well. Do you then just move right along into another agent B cell depletion therapy? I mean, what's your next step in escalation in the acute setting? 
Dr Mariotto: I would for sure start to, as you said, with steroids, plasma exchange, and in case IVIG, and then quickly move to chronic treatment. And for patients who are not recovering well, I would think of something which has a quick effect so we can really start treating patients very quickly. There are different options. And all over the world, there are different rules for using immunosuppression in NMOSD. Like in Italy, for example, it's different from US or other countries, Germany, for example. There are different approved treatments and different rules of using them before or after rituximab, for example. We all know that there are treatments approved for NMOSD all over the world. But in some countries, like for example in Italy, we should use rituximab first, and then if it doesn't work, escalate to the approved treatment. I know in the US it's different. But anyway, for a patient who does not improve quickly, I would start with something which has a quick effect on the disease. 
Dr Smith: And then rituximab versus inebilizumab, you know, CD20, CD19, what's your advice there? Is one preferable to the other, you know, if we have options to do either? 
Dr Mariotto: Yeah. So, between rituximab and inebilizumab, we know that the target, well, is different, but is anyway B cells, so CD19 and CD20. With CD19, we can affect both plasma blast, plasma cells, and B cells. That's why the target is broader. And of note, this is an approved drug, while rituximab is, in most countries, used as off-label treatment. 
Dr Smith: So inebilizumab would probably be preferable if we're able to do that. 
Dr Mariotto: Unfortunately, there are not so many studies comparing rituximab with the approved drug, which is, of course, a pity, but that's the case. While we have clinical trials for all the approved drugs, and although the trials were designed differently, as we mentioned in the Continuum paper, we can argue something of the comparison between the approved drugs. But it is not so clear the comparison between rituximab and the new drugs, which is also something that we should work on. 
Dr Smith: And then for chronic suppressive management, what other options are there? 
Dr Mariotto: So, in addition to B cells, target can be interleukin-6, as we know with tocilizumab or satralizumab, and then complement with eculizumab. These drugs are both based on the pathogenesis of the disease. That's why we also discuss it in the paper, which shows a clear involvement of complement, and among cytokines of interleukin-6. So, targeting these made clear that could improve the disease quite well, and that's why they designed some clinical trials on these drugs, which are now approved, as we said, for NMOSD. 
Dr Smith: Wow, so many options, and a lot of questions, but limited time. Let me just ask a couple of more. I see a lot of myasthenia patients, and there's a lot of variability, as you know, in patients with myasthenia, the extent to which complement is an important mechanism versus other, you know, important mechanisms. To what extent is response to a complement inhibitor kind of uniform across NMOSD? Or there's some patients who just don't respond to a complement inhibitor and others that respond really well. And then just, I'll just give my second question out is, you know, what about combination therapies for patients who have particularly challenging NMOSD? 
Dr Mariotto: So usually these patients have a terrific response to complement inhibitors, and this is also shown by the clinical trials where we saw how eculizumab have a very impressive effect on the disease. And also, maybe this is also your experience, a very quick effect. So that's why there are also thoughts on using it in a very acute stage of the disease. That was what I was thinking about before. But then it has a very huge effect on complement, which is a major factor involved in the pathogenesis of NMOSD also in the chronic disease stage, and that's what also we see from clinical trials. Usually, we prefer to switch treatment from one to another and not to combine them. Of course, in very difficult cases, this can be considered, but the recommendation is to switch from one of these approved drugs to the other, or from rituximab to one of the approved drugs, and try to find out the best for our patient before combining them.
Dr Smith: The complement inhibitor trials are breathtaking, at least for me. If I'm trying to convince students to go into neurology, I'll say, "Take a look at that paper," because anyone who claims that we're "diagnose and adios" is so wrong. It's so exciting. So, at a high level, this must have fundamentally changed outcomes for patients. I mean, it's still a difficult disease, but what is the kind of prognosis for that patient I described who comes in, gets the therapy you talked about? What does their long-term outcome look like in this modern therapeutic environment?
Dr Mariotto: So, NMOSD is almost always a relapsing disease. That's why, as we mentioned, we have to treat patients always. But the prognosis changes a lot since we were also able to use all these drugs for the disease. So, the prognosis changes if we recognize it properly and early, and if we treat NMOSD properly with immunosuppressives. So, whatever we choose it's important to start it quickly, and this is the only way that we have to improve the prognosis of this disease. We have very active cases, but we have also cases who responds quite well to this immunosuppressive treatment, since now we have, as mentioned, these ones which are very impressive and show incredible results. So, the prognosis of the disease change in the last year, thanks also to the improvement of the diagnosis and of the treatment choices for the disease. 
Dr Smith: I'm just... I- maybe my last question, you know, just at a personal level, not only for you as an expert who's caring for these patients, but in the patient community, this must have been a pretty exciting period of time, right? I mean, these, these drugs are coming fast and furious, and what a change. What's the kind of zeitgeist in the community, both your professional community and amongst the patient community about where we are?
Dr Mariotto: Yeah, you're right. The last years were defined the years of NMOSD and also MOGAD because we had finally approved drugs which is relevant for all the disease that we treat and changed the landscape of the disease for clinicians, but also for patients. And we have more than one, as we said, so we have more options that we can also discuss with patients to try to choose the best one in terms of activity, but also route of administration or time. Some years ago, we just had rituximab, which is not approved in most of the countries, and now we have different approved drugs. And we improved the diagnosis of the disease thanks to the availability of live cell-based assay. And then we are working a lot also on biomarkers like GFAP, for example, which has been shown to be a very attractive biomarker able to mark disease activity and maybe also prognosis on this disease. So, you're right. I mean, in the last years, the landscape of NMOSD changed a lot. 
Dr Smith: Sara, thank you so much for talking with me. I could keep going for another half an hour, but I would be in trouble with my editor, so I think we probably need to wrap it up. But thank you so much. This has been very informative. 
Dr Mariotto: My pleasure.
Dr Smith: Mine too. Thank you. Again, today I've been interviewing Dr Sara Mariotto about her article on NMOSD, which she wrote with Dr Romain Marignier. This article appears in the April 2026 issue of Continuum on multiple sclerosis. Be sure to check out Continuum Audio episodes from this and other issues, and thanks to you, our listeners, for joining us today.
Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.

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
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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 this radiological feature, then you really want to consider ordering the MOG antibody too.
 
Dr Smith: Yeah, I found that really interesting. And I- actually, my next question is perhaps a good follow-up on that, is, what are the diagnostic pitfalls? You give a lot of examples of situations and I think some cases where it's easy to get tripped up and misdiagnose someone who has MOG with another fairly common neurological problem.
 
Dr Flanagan: Yeah, I think some of the things that can help you when you're determining if the MOG is a true positive or false positive is the level of the antibodies. The super high titers, if it's a clear positive or very strong positive, the likelihood is that that is much more likely to be MOGAD than those low positives just above the cutoff. So that can be useful to help you discriminate from false positives. Those lesions, again, if all the lesions persist over time, that's going to be more suggestive of multiple sclerosis. Other diagnostic pitfalls, I suppose, if it's a syndrome that's not really associated with MOG, like peripheral neuropathy or other syndromes where we'll see some case reports, but usually I would be very cautious about those kind of presentations. So usually, having the antibody at a high level, and then also if they've had other symptoms suggestive of MOGAD, like if a patient has had recurrent optic neuritis and then they have an unusual brain syndrome, or they start out with an unusual brain syndrome and then have recurrent optic neuritis. You know, there are situations that make it more likely if they're having other typical phenotypes of the MOGAD where we can kind of expand the spectrum, but we have to be careful.
 
Dr Smith: I was really curious about the dynamic imaging findings. And you point this out both in terms of the resolution of imaging findings, but also in that patients who have an acute MOG syndrome often have very rapid evolution of the imaging abnormalities. I'm just curious, you know, why is that, and what do you make of it? Does it have a mechanistic implication, do you think?
 
Dr Flanagan: I don't think we know for sure. I think there's probably a lot more happening than we see on MRIs sometimes. What sometimes can happen in about 10% of patients is the initial MRI can be normal. We don't tend to see that with multiple sclerosis or NMOSD. Then what we see is it evolving over time. So, at that time, if you do a CSF, you'll often see inflammation, but we don't see the lesions. Now, that might be because the MRI is not very good at picking up cortical involvement. That can be difficult to see in MRI. Or there could be other factors. It could be a functional effect on the MOG but without frank demyelination yet, for example. Or there could be edema that you- myelin edema that you can't see as a lesion yet on MRI. But we do see that if you repeat the MRI, sometimes it'll change a lot. So, you may go from one or two lesions on the first MRI to twenty lesions on the second MRI a week later. So, it does tend to change a lot. And then over time, those lesions also resolve. So, what I say is if it's a very suspicious situation---like a child comes in with new-onset encephalitis, has inflammatory CSF---you might wanna consider repeating that MRI down the line and seeing if it's changing. And then over time, you know, a repeat MRI a year after the onset when there's brain or spinal cord lesions can be very helpful just to make sure you're on the right track, because lots of those lesions will then disappear, and that's a very clear discriminator from multiple sclerosis.
 
Dr Smith: Yeah, thanks. I mean, I was wondering the same thing about whether that particular feature might imply, you know, a functional abnormality as opposed to more of a structural abnormality. So probably a lot more to learn as we move forward. There are now consensus diagnostic criteria that were published a couple of years ago. I think you've already touched on kind of the general approach, but do you want to speak to those? I found your summary pretty helpful.
 
Dr Flanagan: Yeah, I think that those criteria are quite useful. They have three main parts to them. The first part is having a characteristic clinical syndrome. So, we talked about ADEM, we talked about cerebral cortical encephalitis, transverse myelitis that's often longitudinally extensive, and optic neuritis being the main syndromes, but sometimes other brainstem or cerebellar involvement can be seen. And then the second part is having a positive MOG antibody. And then there's some caveats there. So, if you have a high positive, then you don't really need any additional supportive criteria. On the other hand, if you're low positive, to get at those sticky antibodies that make sure it's not a false positive, you need some additional supportive clinical or MRI criteria. Or if you're only positive in CSF, you need that additional criteria. You also need to be negative for the aquaporin-4 antibody, because they can overlap clinically. And some of those supportive criteria are things that we talked about a little bit earlier, longer lesions within the optic nerve, bilateral involvement, involvement of the nerve sheath or optic disc edema. This is a situation, MOG antibody disease, where your fundoscope is useful and looking in the back of the eye and seeing swelling, because we don't tend to see that quite as often. It's less common in multiple sclerosis, but we often see prominent edema in MOGAD. And then in the spinal cord, the lesions tend to be central in the cord. Sometimes they form this H sign where it's restricted to the gray matter, and they tend to be longer, sometimes involving the conus. Patients will often have neurogenic bowel or bladder. And then in the brain, deep gray involvement, those large lesions along the cortex with swelling are some of the typical features. And then the final step is exclusion of another diagnosis. Just like with any test that we do in neurology, our final step is going to be to put that into context. So that's just a normal thing that we will always do when we get a group of test results back that we don't know what it means. We have to put it into context. So, make sure it's not multiple sclerosis, everything else does not look like multiple sclerosis, and then you can be on your way to make a diagnosis.
 
Dr Smith: Definitely encourage listeners to read your article. I guess I say that with every time I- or with everyone I talk to for Continuum Audio, but the images are really fantastic and the cases are fantastic. So, everything you've described is well-illustrated, including really nice schematic sort of diagrams that help differentiate NMO from MOG and MS. So, if you like MRI scans and good imaging frameworks, then this is the article for you.
 
Dr Flanagan: I think that's true, and the other thing is that the imaging is quite helpful because it takes a while for that antibody to come back. We're lucky at Mayo Clinic, if you work here, it, it comes back faster for you. But for many places, that time of sending it in, so a lot of times you don't know right away. So, looking at scrutinizing that MRI can be very helpful to guide you on your way and to know what you're dealing with and how to approach both the acute treatment and plans to have potentially a steroid taper after the acute treatment and those kind of things that can help guide you in that regard.
 
Dr Smith: Yeah. So, let's talk about treatment. You know, what's your approach to treating a patient who has an acute demyelinating syndrome related to MOG?
 
Dr Flanagan: So similar to other things, MOG is very steroid responsive. So, we use high-dose IV methylprednisolone in adults. That would be one gram IV for five days. And then we also will sometimes use oral steroids, twelve hundred and fifty milligrams. That's a bit of a hassle because it's twenty-five fifty-milligram tablets, it doesn't come in a larger tablet version. But it's very helpful to patients because they can get started on it right away. You don't have to set up an infusion center. So, we have used those oral steroids often in people who don't have access to an infusion center, are not in the hospital. And particularly as it's often optic neuritis, some of those patients are seen in the outpatient setting, so we can get in with treatment quickly. In patients where it's more severe, it doesn't recover quickly with steroids, then we would consider escalating to plasma exchange as our second-line treatment, and there's some retrospective data that suggests that plasma exchange can be useful. That's gonna be particularly for those people who don't have that quick response to steroids, or maybe more severe phenotypes like that brain involvement with ADEM or cerebral cortical encephalitis, where those patients might be in the hospital and quite unwell. I will say, we might get on to this, that sometimes MOG can be very, very severe and even fulminant, where there can be increased intracranial pressure, and these patients can be in the ICU, and it can be life-threatening. And so, it's really important to treat those patients aggressively, and some patients have even required hemicraniectomy or additional treatment. Sometimes IL-6 blocking medications have been used in that situation. So, monitoring and treating increased intracranial pressure in those rare patients, probably 2 or 3% that have the very severe attack, is important.
 
Dr Smith: I think one of the things I found interesting, and then I'd love to get your feedback on this, is that most patients with MOG seem to have a very readily treatable disorder that's monophasic, right? You treat them with steroids, and they do well. On the other extreme, there are these patients that have a much more malignant presentation, and there are some that sound like they benefit from prophylactic or some chronic therapy. What's your approach, right? In MS, we do serial scans to monitor, and obviously, our patients are on, you know, chronic disease-modifying therapy. How do you decide when you're going to provide some sort of prophylactic therapy? How do you monitor it? How long do you continue it?
 
Dr Flanagan: That's a great point. We don't know for sure yet, but I think for the most part, our approach has been if the patient has a single episode, they recover well from that episode. So, if that's optic neuritis, they're back to twenty/twenty vision. They have recovered well. We don't tend to use chronic maintenance immunotherapy. Sometimes after the first attack, we'll do a little bit of a slow taper, maybe over four, six weeks. We have done longer than that. And then we won't place them on any long-term treatment, because it's about 50% of patients that may have a monophasic disease, so we don't want to treat all those people who are destined never to have another relapse. On the other hand, if a patient had a very severe episode, they're in the ICU, they're intubated, some of those patients then afterwards we will start them at least temporarily on an attack prevention medication for at least a few years to get them through. Some patients will be very fearful of future relapses in that situation. Or if they don't recover well, if they're blind in one eye after an episode and then their other eye is vulnerable, or they're left with some residual deficits neurologically from a myelitis, then we would often sometimes put those patients after the first attack. But most of the time, we're gonna wait and see if they get that second attack, and then once they have the second attack, that is when we would consider a steroid-sparing medication. But I will say that there's no proven medications. We don't have any clinical trial data available yet. So some of those patients with relapsing disease, we'll either try to enroll them in a clinical trial, or we'll use an off-label treatment to try and manage their disease based on what we've learned from neuromyelitis optica or from multiple sclerosis. A few different options seem to be better, and we can maybe get into that too.
 
Dr Smith: Yeah, let's go there. So, what options are there? You mentioned in more fulminant disease IL-6 inhibitors, and by that I assume you mean tocilizumab, but what are the options when you want to use prophylactic therapy?
 
Dr Flanagan: So, that tocilizumab can be beneficial in the very acute situation, in that malignant situation. But also as an attack prevention treatment, the IL-6 blockers seem to- some of the retrospective data seems to look like it works reasonably well, so we work and see if we can get that approved. Another medication that can work well is IVIG or subcutaneous immunoglobulin as a maintenance treatment, so we would sometimes give that, like, at least one gram per kilogram once a month. The benefit of that is it doesn't lower your immune system, so there's some advantages there, particularly in people who may be more prone to infections, older people. So, we'll sometimes use that. But we do get into a lot of challenges with insurance coverage, and it can be difficult to get these approved by insurance because we only have retrospective data out there. So then for some patients, if they're in a region where there's a clinical trial available, we might try to enroll them in a clinical trial. And there are some clinical trials underway now, so hopefully in the future we'll be able to have some FDA-approved medications that can have some Class 1 data that we can follow. Because it's hard when you're just following retrospective data or anecdotal reports, it's a little bit difficult to know exactly how well you're doing with your treatments.
 
Dr Smith: Well, Eoin, I wonder if we could finish up by just looking into the future, right? I mean, it sounds like a fun patient population to take care of because you've got lots of great therapies and can have a durable impact. But sure would be nice to have more evidence-based therapies and an FDA approval. What trials are going on? What's the future look like?
 
Dr Flanagan: Yep. So, there's some trials going on in the- a couple of worldwide trials. One is on an FCRN blocker called rozanolixizumab, which is kind of like a plasma exchange-type treatment which removes your antibodies, and it's a weekly subcutaneous treatment where adults are enrolled. And the second one is called satralizumab, which is another IL-6 blocking medication. And again, that one's given once monthly under the skin. And the trial for that also includes children down to age eighteen, so for adolescents, too, that can be an option. There are trials, I believe, in Asia for tocilizumab too, and there's one starting in Australia for rituximab. So, the good news is that we're going to have some really good data down the line for lots of different agents, and we'll be able to figure out which treatments work. And this will be really of great benefit to our patients when we get that Class 1 data to kind of guide us on what we should be using and really build on the success of some of the other conditions like neuromyelitis optica spectrum disorder, where we now have four or five approved, medications that work very well.
 
Dr Smith: Well, Eoin, thank you. This is a great conversation. I will say that it... the topic that I was a little intimidated about. I'm a simple peripheral nerve guy, as you know. But I think moreso than any other Continuum article I've read recently, I'm, like, loaded for bear. I can't wait to go back on the inpatient service and look for some MOG patients, because your article really left me feeling kind of prepared to think through this in a clinical setting. So, thank you for the conversation, and congratulations on a really wonderful piece for Continuum.
 
Dr Flanagan: Yeah, thanks so much. Always a great honor to be involved in the Continuum, and thanks to all the readers out there.
 
Dr Monteith: This is Dr. Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.

Adult‑onset leukodystrophies, though rare, can closely mimic MS on both clinical presentation and neuroimaging, posing a significant diagnostic challenge. This episode highlights key clinical and radiologic red flags that can help distinguish these disorders from MS, preventing misdiagnosis and avoiding inappropriate treatment while enabling timely genetic counseling and targeted therapies.
In this episode, Teshamae Monteith, MD, FAAN, speaks with Roberta La Piana, MD, PhD, coauthor of the article "Adult-Onset Leukodystrophies Mimicking Multiple Sclerosis" in the Continuum® April 2026 Multiple Sclerosis and Related Disorders issue.
Dr. Monteith is the associate editor of Continuum® Audio and an associate professor of clinical neurology at the University of Miami Miller School of Medicine in Miami, Florida.
Dr. La Piana is an associate professor in the Department of Neurology and Neurosurgery at the Montreal Neurological Institute, McGill University, and an associate member of the Department of Diagnostic Radiology at McGill University in Montreal, Quebec, Canada.
Additional Resources
Read the article: Adult-Onset Leukodystrophies Mimicking Multiple Sclerosis
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Full episode transcript available here
Dr Monteith: You just saw a patient in clinic. And you're clear, the diagnosis is multiple sclerosis. Not everything fits, but it kind of looks like multiple sclerosis. You see the patient back years later. There're some treatment issues, the patient's not responding to treatment, and things look different. Have you thought about a genetic inherited problem like leukodystrophy or a genetic white matter disorder? Listen to this podcast. We're going to help you figure it out.
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 Monteith: This is Dr Teshamae Monteith. Today I'm interviewing Dr Roberta La Piana about her article on adult-onset leukodystrophies mimicking multiple sclerosis, which she wrote with Dr Gabrielle Macaron. This article appears in the April 2026 Continuum issue on multiple sclerosis. Welcome to our podcast. 
Dr La Piana: Thank you. Thank you for having me. 
Dr Monteith: Absolutely. Why don't we start off with you introducing yourself?
Dr La Piana: So, my name is Roberta La Piana. I'm a pediatric neurologist. I trained in Italy, I did my medical school, I did my residency in pediatric neurology there. And then I moved here to Montreal, to the Montreal Neurological Institute, to do a PhD in neuroscience. And that's where I specialized in adult-onset genetic white matter diseases. And after my PhD, I was recruited as an assistant professor here. So, that's where I got into this field. 
Dr Monteith: This big field, highly specialized; lots of disorders, but highly specialized. And what got you into this? Neuroscience is huge. So, was it a mentor, or…? 
Dr La Piana: No, actually, it was because of my background, because I trained as a pediatric neurologist and I loved the genetic white matter disorders in the pediatric population. So, when I came to the Montreal Neurological Institute, initially it was mainly to have a better expertise in imaging. And being at an adult neurology institute, I started seeing patients with adult genetic white matter diseases, and I was immediately fascinated by how different they were from their pediatric counterparts. Because in pediatric genetic white matter diseases, pediatric leukodystrophies look very diffuse, look very confluentous, so it's difficult to mistake them. But in adults, in the adult forms, I was initially driven by how often they can be misdiagnosed as multiple sclerosis or as other acquired white matter disorders. So that's why I got really interested in in this field. 
Dr Monteith: You're, like, literally the perfect person for this discussion. 
Dr La Piana: I'm not sure- *laughs*
Dr Monteith: Why don't we start off with what your objectives were when writing this article?
Dr La Piana: With writing this article, the goal is what I have been, actually, doing for the past ten years or so. So, really try to get more attention into the field because of the high rate of potential misdiagnosis of patients. So, that's exactly the reason why I really would like to raise the interest of neurologists for these disorders, because they are not considered enough in the differential diagnosis of patients, of adult patients presenting with white matter disorders. They are considered rare---which are, they are rare, definitely. But collectively, while each single form is rare, collectively they are not as rare. So- and thus, the risk of misdiagnosis and the potential impact of misdiagnosis on them with, you know, you can imagine giving patients inappropriate treatment or missing the possibility of a prenatal genetic diagnosis is so high that I really would like people to keep these disorders in the differential. 
Dr Monteith: And it sounds like more than ever, this is really important because some of the newer developments in the field.
Dr La Piana: Yes. Specifically, we have now tools that will allow to diagnose these patients quite quickly. All the genetic techniques that are available nowadays can really, with one single shot, we can now sequence hundreds of genes so we can have a quicker diagnosis. And this thing was impossible up until ten years ago. So that's definitely the first huge improvement that makes these disorders now easily diagnosed.
Dr Monteith: Yeah. So why don't we talk a little bit about how common is this misdiagnosis for these rare subtypes?
Dr La Piana: Yeah, the misdiagnosis, it depends on the cohorts. Generally speaking, I would say that the rate of that misdiagnosis for these forms is up to 25% or even more in some other cohorts. And it really depends on the forms. Like, there are clearly some forms, especially those that present with multifocal white matter diseases, that present with nonspecific clinical presentations like migraines, image---and especially for female patients, and for which migraine is so common, having multifocal with other abnormalities is so common, the rate of diagnosis increases even further. So, these are all things that we need to keep in mind. I know these are rare, but still, we need to always have them on the back of our minds. 
Dr Monteith: Are there any particular disorders that are more often misdiagnosed? And you spoke about progressive forms of multiple sclerosis being a common kind of misdiagnosis. 
Dr La Piana: Yeah. So, there are definitely forms that are more commonly misdiagnosed. And these are those that, as I probably repeated already too many times, is the word multifocal, which is key. So, all those genetic white matter disorders that present with multifocal white matter abnormalities are not initially considered as genetic. So, I'm thinking about all of the leukovasculopathies, so, the small vessel diseases which are genetic in origin. For example, CADASIL; for example, the disorders related to collagen-4; so, the COL4 A1 or A2-related disorders. Those are clearly more commonly misdiagnosed initially. Another big group, unfortunately, is the CSF1R-related disorders. I know I'm saying a lot of gene names, but due to the fact that they start with multifocal abnormalities and they start with quite nonspecific, slowly progressive symptoms, the rate of misdiagnosis is definitely higher.
Dr Monteith: And can you discuss some of the clinical challenges when seeing patients that might lead to this misdiagnosis? 
Dr La Piana: There are multiple clinical challenges. One is definitely the presence of nonspecific or initially mild clinical symptoms that sometimes don't raise initially the red flag of something, degenerative or progressive or genetic. One category that I would mention are psychiatric disturbances, especially in the form of depression, anxiety, or apathy. This is quite common in patients with some forms of genetic white matter disorders, and they are initially misdirected to psychiatrists and taken care in that domain. But it's only when some even mild neurological symptoms like a gait disturbance or hyperreflexia, or we had patients with, like, a urinary incontinence. It's only at that time, but maybe years have passed meanwhile, that these patients are finally referred to the neurologist
Dr Monteith: You spoke about some of these clinical symptoms. Can you give us some other clinical red flags? 
Dr La Piana: Well, some other clinical red flags can be, for example, the extraneurological involvement. So, we have patients where- and there's a reason immediately to some specific disorders. For example, infertility. The presence of infertility in a female patient with white matter disorders should immediately form the consideration of the specific genetic white matter diseases that are associated with these forms. And this is not something that neurologists tend to ask about in the collection of the clinical history. And this is something that can make the difference and can accelerate the diagnosis. 
Dr Monteith: What are some other things? I mean, I know we can think about treatment, lack of a common treatment response, maybe, to steroids. You gave a great example of optic neuritis, for example. Give us some other things that we should say, hey, this doesn't fit the picture. Red flag. 
Dr La Piana: In this case, I think we want to talk more about the specific misdiagnosis of MS. Because these patients are often misdiagnosed with MS, but they might sometimes be misdiagnosed with other forms of acquired white matter diseases. When we consider MS, definitely the presence of being treatment resistant: so, patients that are not responsive to the common MS-targeting treatment should be always a red flag. The evolution as well. So, for example, the presence of a more slowly progressive course is another red flag. The presence of optic neuritis. Sometimes it's tricky because it's not common in the genetic white matter disorders, it's used as a criterion to orient correctly towards a multiple sclerosis. But we need to keep in mind that there are forms, genetic forms, especially the mitochondrial forms, that can present with optic neuritis and are really at the overlap with the multiple sclerosis spectrum. Then, if we want to move forward beyond the clinical side and go into the laboratory, of course a negative lumbar puncture with no oligoclonal bands should be a major red flag.
Dr Monteith: What about some of the radiographic features? 
Dr La Piana: So, the radiographic features is something we are really working on in the field, especially with the new criteria used in MS. So, for example the paramagnetic rim lesions or the central vein sign, they are considered the specific forms. But it's true- and don't have an answer for that. I want to be clear, but it's true that they haven't been assessed yet extensively in patients with genetic white matter disorders. Anecdotally, I can say, because I have already reported this at conferences, that we have seen patients with genetic white matter conditions reaching a threshold for a central vein sign that can be considered diagnostic for MS. And we have seen that in some patients. Again, no study has been carried out extensively to date, but I think we should consider that with a grain of salt. But yeah, the paramagnetic rim in lesions is probably more accurate to distinguish between genetic and acquired white matter disorders. 
Dr Monteith: And what about some of the genetic white matter disorders that mimic MS? You spoke about things like CADASIL; what are other things that we should keep in the back of our mind? And you have great charts, to our listeners, and they're going to have to review those charts, because they're excellent. I think maybe they need to find a way to make that a little bookmark you walk around with on the ward. But what are some other conditions that kind of commonly mischaracterized? 
Dr La Piana: Two of the main groups are the one that you mentioned. So, leukovasculopathy is- so, CADASIL, is definitely one of the most common misdiagnoses of MS. And the presence, as we said, of some clinical features like migraine, especially when it's complicated migraine with visual aura, we all know that. But especially in the context of a positive family history for either a psychiatry condition or migraine as well, or strokes, these are all factors that should prompt the consideration of these disorders in the differential of a patient with white matter disorders. Another category are definitely mitochondrial disorders, which I think are more neglected than others because we don't think about mitochondrial disorders when we see white matter disease; we tend to consider that mitochondrial disorders are a problem of the gray matter, but they are not. There are white matter diseases that have definitely mitochondrial. And the third category are probably microgliocytes, which are represented by the CSF1R-related disorder. And this is also something that is clearly quite prevalent, relatively prevalent, in the field of genetic white matter disorders misdiagnosed as MS. 
Dr Monteith: Yeah. Why don't we go through some of the, kind of, key history, you know, some of the key questions you would ask in the history to try and differentiate? You mentioned kind of subtle symptoms, longstanding progressive symptoms. I know things that we look at like relapsing/remitting and some trigger factors can actually be associated with some of these genetic disorders. So how do you approach a patient? What are some of the key questions? You talked about family history and you talked about medical history, but why don't you kind of give us a nice way to kind of hone in on to the patient?
Dr La Piana: There are a couple of questions that we usually ask. I should make a disclaimer, though, that I work very closely with the MS clinics, so we are ready to receive patients that are prescreened. So, these are already patients that people working on acquired white matter disorders feel like they are atypical, so they want our opinion. But usually, there are two groups of questions that we always ask. One is about the family history. And by saying family history, I really dig into the family history. I don't just want to know whether there are family members with neurological disorders. I ask specifically about migraine. I ask specifically about infertility issues. I ask specifically about psychiatric issues. These three things are always on the top of my mind when asking about family history. The other thing is a family history for neurodevelopmental disorder, because you know that some people might not remember that some genetic white matter diseases can present at different ages. So, in the same family, there might be cases with a pediatric-onset leukodystrophy, and that can manifest at a later age in other family members. So, this is something that we always explore. In terms of the clinical history, one question that I recommend always to ask is really about more subtle symptoms. So, for example, many of our patients present with progressive balance problems or progressive mobility issues that have been going on for a while. So, we always ask how they were when they were in their teenage years, for instance. And it's frequent that they say, actually, I was a bit clumsy. Actually, I was not the first being picked in school at phys-ed sports. And these are all interesting aspects. Maybe they are totally incidental, and sometimes they suggest that there was probably something going on for a long time. The other thing is the presence, for example, of learning difficulties. Again, these are things that are subtle but testify that there was probably a process that was more longstanding.
Dr Monteith:  You talked about things like rim lesions. Are there other types of sequences that might be useful to better characterize demyelinating diseases that are genetic in origin? I assume higher levels of MRI might be better at differentiating. 
Dr La Piana: Yeah. So, in the clinical setting, there are a couple of sequences that are very useful. One is the diffusion, because as opposed to multiple sclerosis, the presence of persistently restricted areas of diffusion can point immediately towards some genetic white matter diseases. One is CSF1R-related disorders. But there are also some other, more rare tremor and ataxia syndrome that present with persistent areas of restricted diffusion as well as others. The presence of calcification. So, adding an SWI, susceptibility weighted imaging, to check not just for calcifications that can immediately orient towards some disorders, but can also identify areas of microhemorrhages that, if we are going back to the leukovasculopathies, to the genetic leukovasculopathies, can tell us that we are on the right track for excluding those type of diseases. Basically, these are the two that are available in every scanner without even going into fancy, more advanced techniques.
Dr Monteith: I was going to ask you that question, how often should we think about this next-generation sequencing when you're kind of on the fence, allowing for some negative results to come back in the abundance of caution? 
Dr La Piana: The problem with the panel, of course, is that you run a panel and you don't know what's coming back. So, then having to deal with variants of unknown significance in genes, then you have to deal with them, and then you have to deal with results that maybe are not as black or white as you would expect initially. So, I'll answer to your question when to do that, our recommendation would be to do that every time you are presented with a patient that presents those atypical features that we summarized in the paper, and that basically raise multiple red flags for an atypical white matter disease that is not multiple sclerosis. And then what to do when you have results? I still believe that having access, of course, to genetic counselors, to neurogeneticists, is critical, but also having access and being in contact with the network of people working on this. Because we are a network; we put the website address on the paper of the white matter rounds because this is an international network that we built over the years, and we connect monthly, on a monthly basis, with meetings to discuss exactly this type of patient. So, we are all learning together, and it's very frequent that people ask us to present cases at the white matter rounds because they have a presented with unusual or atypical genetic findings and they want the opinion of experts. 
Dr Monteith: Great. Well, I'm really glad that resource is available. And I'm also really glad that you wrote that article with your colleague. Thank you so much.
Dr La Piana: Thank you so much, Tesha.  
Dr Monteith: Today I have been interviewing Dr Roberta La Piana about her article on adult-onset leukodystrophies mimicking multiple sclerosis, which she wrote with Dr Gabrielle Macaron. This article appears in the April 2026 Continuum issue on multiple sclerosis. Be sure to check out Continuum Audio episodes from this and other issues, and thank you to our listeners for joining today. 
Dr Monteith: This is Dr Teshamae Monteith, Associate Editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use the link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/audioCME. Thank you for listening to Continuum Audio.