Mastering Autoimmune Neurology Diagnostics

Awareness of the specific clinical and MRI features associated with AQP4-NMOSD and MOGAD and the limitations of currently available antibody testing assays is crucial for a correct diagnosis and differentiation from MS. Growing availability of effective treatment options will lead to personalized therapies and improved outcomes.

In this episode, Gordon Smith, MD, FAAN speaks with Elia Sechi, MD, author of the article “NMOSD and MOGAD,” in the Continuum August 2024 Autoimmune Neurology issue.

Dr. Smith is a Continuum® Audio interviewer and 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. Sechi is a neurology consultant in the neurology unit of the Department of Medical, Surgical and Experimental Sciences at the University Hospital of Sassari in Sassari, Italy.

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Read the article: NMOSD and MOGAD

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Host: @gordonsmithMD

Guest: @EliaSechi

Full episode transcript available here

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum, the premier topic-based neurology clinical review and CME journal from the American Academy of Neurology. Thank you for joining us on Continuum Audio, which features conversations with Continuum’s guest editors and authors, who are the leading experts in their fields. Subscribers to the Continuum journal can read the full article or listen to verbatim recordings of the article and have access to exclusive interviews not featured on the podcast. Please visit the link in the episode notes for more information on the article, subscribing to the journal, and how to get CME.

Dr Smith: Hello. This is Dr Gordon Smith. Today, I've got the great pleasure of interviewing Dr Elia Sechi about his article on aquaporin-4 antibody-positive NMOSD and MOGAD, which appears in the August 2024 Continuum issue on autoimmune neurology. Dr Sechi, before we dig into this really exciting topic about NMOSD and MOGAD, perhaps you can tell our listeners a little bit about yourself, where you practice, how you got interested in this topic.

Dr Sechi: Hi, Dr Smith, and thank you for having me. So, my story begins here in Italy, actually - I did my med school and residency in neurology at the University Hospital of Sassari here in Sardinia. And after residency, I was lucky enough to be accepted at the Mayo Clinic in Rochester, Minnesota for a research fellowship - and that's where I spent the next three-and-a-half years, approximately. My fellowship was focused on autoimmune neurology, specifically demyelinating diseases of the CNS associated with antibodies – so, of course, NMOSD and MOGAD mostly, but also myelitis, MS, and autoimmune encephalitis – so, there's where I built most of my expertise in the field. And then, it was at the beginning of the pandemic (of the COVID pandemic) that I came back here to Italy to practice. And now, I work mostly as a neurohospitalist, and I also have my subspecialty outpatient service for patients with autoimmune neurological diseases.

Dr Smith: I wonder if you might just give us a minute or two about what it was like training in Mayo? I went to medical school there, and, you know, at the time, I thought that was just normal healthcare and normal training, and, you know, it was only later that I realized how amazing that was. I mean, this is where aquaporin-4 was discovered - I mean, what was that like? It must have been really cool training there with that team.

Dr Sechi: Yeah. You know, it's the temple of autoimmune neurology. It's fantastic. It's a great environment, very stimulating. You know, I think the great strength is that they see many patients with rare diseases, so, you get really confident with MRI features and clinical features with the history of the diseases, and this is important to recognize the typical features and differentiate from MS to do a good differential. And, of course, you know, the team is fantastic - superstars in the field. It's very, very stimulating. So, it's something that I definitely recommend. It was a fantastic experience.

Dr Smith: Well, you know what's great is, I don't know if you follow sports, but, you know, like, in the United States and college football, people refer to Gator Nation – right, these are all people who are fans of the Florida Gators. Or, maybe it's AC Milan nation in Italy. I don't want to get there (Roma, whatever), but there are all these people who've trained at Mayo, and, uh, what's great is it's a small world, right? So, I'm super excited to meet you and talk about this, because - I'm going to add you to my Rolodex, because when I see these patients (I'm a neuromuscular guy, but I do a fair bit of inpatient time), I'm always calling a small number of people, so I'm really pleased to meet you so I can put you on speed dial and ask you questions about these patients. I wonder if, maybe, we can begin? You know, in our preparatory discussions, I shared that I just came off our hospital service, and we had several of these patients, you know, where we were thinking about NMO or MOGAD as a cause for their problem - and I wonder if you just have any pearls or pitfalls in when we should suspect this, right? Most of us recognize bilateral optic neuritis, longitudinally extensive myelitis - we need to be thinking about these. Any pearls or pitfalls for when we should or should not be looking for these disorders?

Dr Sechi: Yeah, I think this is a great question. I think the first thing to pay attention is the phenotype. So, the clinical MRI phenotype that are typically associated with NMOSD and MOGAD, they are quite characteristic - and it's important to be aware of those phenotypes and how they differ from MS, because in my experience, one of the common misinterpretation (misconception) in clinical practice is just to test for AQP-4 and MOG antibodies in any patient with new-onset demyelinating disease of the CNS, even if it's typical MS. And, this is quite wrong, because MS is way more common in clinical practice - it’s sixty, eighty times more common than NMO and MOGAD - and so, if you test all those patients without filter (indiscriminately) for antibodies, you increase the risk of false positivity exponentially, even if you have a highly specific test. So, first of all, I think it's good to select the right patients to test. As you said, patients with LTM, extensive involvement of the optic nerves on MRI, ADEM - there’s also patients with cortical encephalitis phenotype (which is a rare phenotype of MOGAD), but not definitely good to test the typical MS patients. This is the first thing.

Dr Smith: Yeah, I mean, that's an issue in all of neurology, isn't it, right? I mean, it's an issue in sort of just sending, you know, the Mayo panel, the autoimmune encephalitis panels - you need to select patients carefully, but I think this attention to prior probability is something that we need to really focus on in multiple areas. So, I wonder if you might expand a little bit on assays. I do a lot of work in myasthenia and I know which labs do a really good job with, you know, acetylcholine receptor antibody testing and those that maybe do not, and there are different methodologies for testing - do you have any wisdom in terms of how to select a lab, what to look for, and how to interpret the results you see based on the particular assay that's being used?

 Dr Sechi: Yeah, that's a critical point. I agree. And especially if you work in myasthenia, you're very well aware of the differences between different assays, and nowadays, most of the high-quality assays are cell-based assays (either fixed or live) - it's the same in myasthenia, and people need to pay attention to some of the less-specific assays. Let's say ELISA, for instance - testing AQP-4 and MOG antibodies with ELISA is quite dangerous, because the risk of false positivity is quite high. So, it's good to know what assays to trust most and also good to know what's the right specimen to send for antibody test. For instance, with AQP-4, we know that serum testing is recommended only, and the CSF doesn't add much, but with MOG, we know that approximately 10% of patients have an isolated positivity in the CSF, which is interesting, because it means that when you have a patient with a strong diagnostic suspicion as a phenotype that is highly suggestive for MOGAD and the serum testing is negative, you may consider testing the CSF to increase your sensitivity. So, this is very important.

Dr Smith: So, I have a question for you that may seem a little naïve, but I bet other people are thinking it - can you tell us why it is that these disorders affect optic nerve and spinal cord preferentially? And I think, for NMO, the whole area postrema thing seems awfully specific to me. What's the deal? Why are these areas preferentially affected by these antibody-mediated disorders?

Dr Sechi: This is a tough question. For NMO, we know, probably, there is higher expression of some of the isoforms. Let's say there is a higher density of AQP-4 molecules that target the most affected regions - so, of course, AQP-4 is preferentially expressed in the subependymal regions around the ventricles and in the spinal cord and optic nerves, but you may have, also, solutions along the cortical spinal tracts in case of the brain involvement. The area postrema is kind of a different explanation, because there is a sort of permeability - increased permeability - of the blood-brain barrier there. So, there are several factors in MOGAD - this is not very clear, so, this is a great topic to study in the future, I think.

Dr Smith: This is a really interesting area, and one that's really benefited by significant therapeutic development. I wonder if you might look a little bit in the future and tell us, maybe, the agent, or perhaps the target, that you're most excited about therapeutically that's coming down the road these days?

Dr Sechi: There are trials ongoing for MOGAD, which is the real need in terms of treatment, because for NMO, we already have three, four drugs that have been approved and which efficacy have been demonstrated by randomized clinical trials, and those are B-cell depleting agents, IL-6 inhibitors, and complement inhibitors. For MOGAD, this is still a gray zone, because the optimal treatment strategies remains to be defined. There are ongoing trials that are quite promising on IL-6 inhibitors and the inhibitors of the neonatal Fc receptor (which is also used in myasthenia gravis as you know). And something that seems to be quite effective - a good option for long-term treatment in these patients and relapse prevention - is also the periodic administration of IVIG (intravenous immunoglobulin), which is a nice option, for instance, in the children where you want to avoid immunosuppressants of other types. So, I think IL-6 is going to show to be very effective in the end. We'll see. We'll see.

Dr Smith: So, I wonder if I might just give you a vignette and get your thoughts about, kind of, acute management, right? I just took care of a patient who had a longitudinally extensive myelitis and she was essentially paraplegic and actually came in progressing fairly rapidly, and we, of course, started her on IV methylprednisolone, sent off the proper diagnostic testing - the question I have is, how quickly do you advance therapy and go to IVIG or plasma exchange when you're encountering these, right? It takes, you know, I think the turnaround time is, you know, often about a week to get these tests back (at least several days) - I mean, should we be going very quickly to plasma exchange in someone who has a severe phenotype? Is it okay to do three to five days of IV methylprednisolone and wait for the results to come back? What's the right approach?

Dr Sechi: I think this is a great question, actually. You know, management of the acute attacks probably is the most important thing, you know, to allow a good recovery, and I think timing of PLEX administration should be very short - so, the threshold for PLEX should be low, especially when the attack is severe, and this has to be done regardless of antibody testing results, which is typically not available before one or two weeks (at least a year in Italy), I think, in many hospitals. So, I think the risk-benefit ratio of administering PLEX is in favor of treatment in these patients, because the side effects (the potential side effects) are very rare and can be prevented. Some diseases, they can mimic NMO or MOGAD - they're very rare, and they can really worsen with PLEX. As an example, we can say spinal cord infarction can worsen, maybe, because of hypotension due to PLEX. Or some very rare infections, like one case, a bad case of intramedullary spinal cord abscess that looked really similar to an AQP-4 IgG-related LTM - and it was bad, because the patient had no fever, no signs of infection, the CSF culture was negative initially, so we ended up doing a biopsy after failure of PLEX and steroids. So, it is recommended to start within the first three to five days, preferentially, in severe cases, and this is great for the outcome of the patient, so, I do recommend PLEX as a second treatment option. And I'm not sure about IVIG acutely. There is some data on MOG, but it's still controversial - it works a lot when PLEX fails, but it can be considered after PLEX, of course. And there are some very rare patients that do not improve, even after IV methylprednisolone, PLEX, or IVIG, and so, you need to consider some rescue therapies. In those patients, it's kind of complicated, because there are some options, like IL-6 inhibitors seem to be quite effective and quite fast-acting for MOGAD attacks, and also eculizumab and complement inhibitors can be an option in patients with AQP-4 - but maybe less in patients with MOG. So, these are the possibilities (very quickly).

Dr Smith: So, you mentioned FcRn inhibitors a moment ago, and I wonder, do you see a future where - and I think you were mentioning them as maybe more chronic therapy? Correct me if I'm wrong.

Dr Sechi: Yeah, yeah.

Dr Smith: Do you foresee a role for these agents in acute management? I mean, there are some that, you know, very quickly lower immunoglobulin levels, though just looking out in the future, you think that these sort of infusion therapies that we think about chronic therapy (you mentioned, you know, complement inhibitors) are going to be useful in acute management?

Dr Sechi: Yeah, it depends. It's a good option to try. I'm not sure about the time to action. It's very dependent on that, because IL-6 inhibitors and complement inhibitors are very fast-acting (I think they can be effective already within twelve hours, 24 hours, which is good), but it's reasonable that, also, Fc inhibitors can be an alternative in the future. As far as I know, there is not much in the literature, but it's good to try in the future in case, acutely.

Dr Smith: Well, exciting times indeed. Elia, thank you so much for a great discussion. I thoroughly enjoyed this. I look forward to visiting you soon, and I want to congratulate you on a really great article that's very interesting and very clinically useful.

Dr Sechi: Well, thank you, Dr Smith. This is my pleasure, and thank you for great questions. I had a great time and hope the readers of Continuum will like the article and the nice figures we have put together. So, thank you, thank you very much.

Dr Smith: Well, again, congratulations. And for our listeners today, I've been interviewing Dr Elia Sechi, whose article on aquaporin-4 antibody-positive NMOSD and MOGAD appears in the most recent issue of Continuum, which is on autoimmune neurology. It's a very exciting issue. Please check out Continuum Audio episodes from this and other issues of Continuum. And thanks to you all 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 this 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.