Chronic Inflammatory Demyelinating Polyradiculoneuropathy With Drs. Jeffrey Allen and Arjun Seth

CIDP is a treatable immune-mediated neuropathy, but both delayed diagnosis and misdiagnosis are common and can have significant consequences. In this episode, Drs. Jeffrey Allen and Arjun Seth review the key clinical and electrodiagnostic features of CIDP, discuss common diagnostic pitfalls and mimics, and explain how updated diagnostic criteria can improve accuracy. They also highlight objective methods for monitoring treatment response and discuss emerging therapies that are expanding the treatment landscape for CIDP.

In this episode, Kait Nevel, MD, FAAN, speaks with Jeffrey A. Allen, MD, and Arjun Seth, MD, authors of the article "Chronic Inflammatory Demyelinating Polyradiculoneuropathy" in the Continuum® October 2026 Peripheral Nerve and Motor Neuron Disorders issue.

Dr. Nevel is a Continuum® Audio interviewer and a neurologist and neuro-oncologist at Indiana University School of Medicine in Indianapolis, Indiana.

Dr. Allen is a professor of neurology in the Department of Neurology at the University of Minnesota in Minneapolis, Minnesota.

Dr. Seth is an assistant professor of neurology at Northwestern University Feinberg School of Medicine in Chicago, Illinois.

Additional Resources

Read the article: Chronic Inflammatory Demyelinating Polyradiculoneuropathy

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Full episode transcript available here

Dr. Nevel: What if nearly half the people diagnosed with a rare disabling neurological disease don't actually have it? Chronic inflammatory demyelinating polyradiculoneuropathy, CIDP, is one of the few neuropathies that can often be treated successfully, yet it remains difficult to diagnose. For some patients, a delayed diagnosis can mean irreversible nerve damage. For others, a misdiagnosis can lead to years of unhelpful and expensive treatments. Good understanding of updated diagnostic guidelines for CIDP has never been more important as newer therapies enter the field and the stakes grow higher.

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. Nevel: Today, I'm interviewing Doctors Jeff Allen and Arjun Seth about their article on chronic inflammatory demyelinating polyradiculoneuropathy. This article appears in the October 2026 Continuum issue on peripheral nerve and motor neuron disorders. Jeff and Arjun, welcome to the podcast, and please introduce yourselves to the audience.

Dr. Allen: Hi, Kate. Thanks so much for having us. I'm Jeff Allen. I'm a neurologist, Professor of Neurology at the University of Minnesota. Do a lot of work in CIDP and really interested in trying to find better ways to diagnose and treat that condition.

Dr. Seth: And hi, I'm Arjun. I'm a neurologist and neuromuscular specialist at Northwestern University, and I'm Assistant Professor here. I also help run our neuromuscular fellowship program. I also have an interest in CIDP and working with Jeff and others to help really diagnose and treat this condition.

Dr. Nevel: Wonderful. Well, thank you so much again for being here, and really looking forward to talking to you both about your article. I always like to start by asking, what do you think is the most important takeaway for the practicing neurologist?

Dr. Allen: I'll kick off with that one. Yeah, I think CIDP can be a challenging diagnosis to make. We know it's tough because there's no diagnostic test. It's rare and heterogeneous. So really being confident about the diagnosis, I think is really, really important. The guidelines published in 2021 can really be helpful to integrate and put a lot of that information together. From a treatment side, we know things that work. We also know that the treatment landscape for CIDP is really, really evolving rapidly. Speaks to the importance of really understanding the diagnosis and making sure we're confident with the diagnosis.

Dr. Nevel: Great. Thanks for that. And I look forward to talking more about some of those points that you made. Why is delayed diagnosis and misdiagnosis of CIDP so common?

Dr. Seth: So, I think there's a lot of reasons that the diagnosis of CIDP is delayed. I think, one, it's hard sometimes for primary care providers and neurologists to recognize the clinical syndrome, specifically if it's a progressive neuropathy worsening over at least 8 weeks with proximal and distal weakness predominantly, and can take a long time

actually to get electrodiagnostics for certain patients. So, I think that ends up leading to a lot of delayed diagnosis. The misdiagnosis of CIDP, I think, is also, uh, quite common. I think things are misinterpreted, perhaps. Electrodiagnostics with diabetic neuropathy, for instance, or something doesn't really quite fit and patients get started on treatments when, in fact, they have a different diagnosis altogether. Or they're diagnosed actually with, they have Charcot-Marie-Tooth disease, they get treated with IVIG, but they don't actually have CIDP and are treated for CIDP with IVIG, but have CMT.

Dr. Nevel: Right. And what are some of the risks to the patient with delayed diagnosis or misdiagnosis? What have you guys seen in the patients that maybe have come to you who have been misdiagnosed or have a big delay in diagnosis?

Dr. Allen: Yeah, we know that this is on both sides of the coin, where delayed diagnosis is a problem, misdiagnosis is a problem. From the delayed diagnosis standpoint, we know time from symptom onset to diagnosis often takes a year or more in most patients. And all that time, patients are progressing, they're developing more axonal degeneration, axonal loss. So, you delay the diagnosis, you delay the initiation of treatment, which is a potential opportunity or missed opportunity to intervene in a meaningful way, and patients develop irreversible deficits that maybe aren't going to come back no matter what we do with treatment. On the overdiagnosis question, yeah, we know that can be challenging, too, in part because it exposes patients to treatments that they probably don't need, and that has certain costs and risks associated with it. It also misses an opportunity to maybe treat what's actually causing their problems. Has a lot of emotional, psychological, and health downsides that we want to avoid if possible.

Dr. Nevel: Great. Thanks for that. And so, kind of getting into how we make this diagnosis, then. How do we make it as accurately as possible in light of, as you mentioned, there's no, like, blood test or specific marker that gives us a yes-no answer in terms of, does this person have CIDP? Can you talk a little bit about the clinical features specifically that are expected or in the guidelines, maybe required even, and what features are common or thing, kind of ancillary symptoms that people have that maybe don't fall into that category if they have to have them, or that's something that you really expect in everyone?

Dr. Seth: Yeah, I can take that. So, I think, uh, we think of CIDP as, like, two different sort of types, so typical and then variants of CIDP. The typical sort of, uh, symptoms is really progressive, relapsing, remitting symptoms or progressive symptoms of proximal and distal weakness with sensory involvement affecting an arm or leg or two limbs in general. You can have different variants of CIDP where it can be just distal, sort of involving just distal sensory loss as well as distal lower extremity weakness in a multifocal, sort of an asymmetric pattern, focal really involving one arm, one leg, or motor predominant variants with just weakness or sensory variants. But really, the clinical syndrome is really progressive symptoms over at least 8 weeks with strong electrodiagnostic criteria, electrodiagnostics that help support that diagnosis. So, you need those 2 big features, and then it's really trying to put them in a bucket. Is it a typical CIDP or a variant of CIDP and what type? And then you decide on treatments based on that.

Dr. Nevel: Great, thank you. What are some other symptoms that are pretty common in people with CIDP?

Dr. Allen: It can be a couple of different things. The disease is really defined by weakness and numbness, as Arjun highlighted. Those are really defining symptoms, and they can differ on which of those is more predominant or which part of the body is affected, but those are really the key features that define the disease. Which not to say other things can't happen. Tremor happens in some patients. We see that quite frequently. Pain and fatigue can happen being part of this disorder, yeah, but they're usually not front and center. It's usually weakness and numbness, and pain and fatigue are usually less of a problem. And certainly, balance is affected in a lot of patients with the disease, and hand function and fine finger tasks. It's rare that cranial nerves get affected, but on occasion, we can see it, especially a 7. Respiratory almost never gets affected. That'd be really uncommon for CIDP. Just not to say it can't happen, but it's quite unusual.

Dr. Nevel: Great. Thank you for that. What are some red flags that when you're seeing patients alert you that maybe this isn't CIDP? Maybe you're thinking about CIDP or it's in your differential diagnosis. What are some things that would lead you to consider an alternative diagnosis, either clinically or maybe on electrophysiologic testing?

Dr. Seth: I can start with the electrophysiologic testing piece first and then go to the other red flags. Physiologically, if you see uniform conduction velocity slowing, for instance, that would be pointing more toward a genetic neuropathy, perhaps, like CMT, Charcot-Marie-Tooth 1A, for instance. Or if you see very prolonged distal median motor latencies with very slowed conduction velocities, that could point toward something like anti-MAG neuropathy, for instance, or POEMS syndrome. If they have really rapidly progressive symptoms with a lot of pain, and it's really sensory-predominant symptoms alone with no weakness, you think of other things that could be driving it instead of just CIDP alone, though that can happen. It's just a little bit unusual for that to happen. Or the other systemic signs and features such as autoimmune conditions, other inflammatory conditions that could be associated with it.

Dr. Nevel: Great. Thanks for that. Can you share some of the tables from your article that I found very helpful? Tables 6-1 and 6-2 had some information on clinical features, and then 6-6, some guideline-driven definitions on CIDP and possible CIDP. And we're used to when there's this guideline-driven definition of a diagnosis having definite, probable, possible. Can you talk a little bit about why this is a little different? It's just CIDP versus possible CIDP.

Dr. Allen: Yeah, sure. I can start with your last question on why definite is dropped. Definite CIDP was dropped from those definitions because there is no single diagnostic test that says you for sure do or you do not have CIDP. So, to say something is definite CIDP is just a little bit fooling ourselves that we can land on a diagnosis with that degree of confidence. So that definite label went away, and now we just call it CIDP or possible CIDP. Before getting into those specific ones, maybe just a couple other red flags that always pique my interest a little bit. Whenever I see a disorder clinically that's really a pain or fatigue dominant disorder, that makes me a little concerned. The electrophysiology, whenever I see slowing that's under the guideline definition of slowing, especially with axonal degeneration, that's always a concern. Was it really secondary demyelination from axonal loss, or is it really true demyelination that's a problem? Slowing across compressible sites is an issue as well. Family history is a big

red flag. You know, if there's a family history, be worried about that diagnosis of CIDP. On your lab testing, if you see a monoclonal gammopathy, dig a little deeper, especially if it's an IgM. And then the treatment response is another big red flag. We consider that patients that are suspected of having CIDP, if you improve after an immunotherapy, then that supports your diagnosis. And if that logic is true, then the opposite must also apply, where if you start a treatment, you do it at a dose and a frequency and a duration that makes sense, and there's no response, that probably suggests that maybe you don't have CIDP. It doesn't mean you don't, but it might suggest that maybe you should look a little bit deeper. So that's a big red flag for me. But going back to the CIDP or possible CIDP, those are kind of how the guidelines now label the diagnosis, so two different diagnostic categories. So, it was collapsed from 3 to 2 in part to make it a little bit more simple. Not to say that it's simple, but at least it's two categories instead of 3. Both of those categories require patients to meet one of the clinical definitions of CIDP that we talked about, either the typical definition or one of the accepted variants. So, you have to meet that clinical definition in order to get in the door. The next step is the electrophysiology, and the difference between CIDP and possible CIDP is essentially how strong your electrophysiologic data is. If you've got 2 nerves with a predefined demyelinating abnormality, then you go up into the CIDP category. If you only have one nerve with a predefined demyelinating abnormality, then you're possible CIDP. And all that supportive stuff that we talk about, spinal fluid imaging, response to treatment, nerve biopsy, if you have a couple of those that are abnormal, as we might expect in CIDP, then you can bump up from possible to CIDP. So, it's all about diagnostic confidence.

Dr. Nevel: Great. Thank you for that. That was really informative. Can you tell us more about the autoimmune nodopathies and when we should consider these in the differential? When should we consider sending antibody tests? Do you send these in every patient that you see who you suspect may have CIDP?

Dr. Allen: You know, it's been an exciting development in CIDP, just kind of recognized within the last 10 or so years, a couple of antibodies that really target that node of Ranvier or the paranodal structures, and those are neurofascin-155 and contactin-1. Caspr1 also is now recognized. Yeah, but those patients typically present with more ataxia, tremor early on, tend to be earlier in life, can have a lot of axonal damage early on, especially the contactins. We know that clinically they behave a little bit differently than typical CIDP or the variants. They progress a little differently. We know that the physiology is much different because we have a specific antibody in those disorders. We also know the treatment response is much different, where they tend not to respond as well to IVIG. So I don't check them in every patient, but certainly people with those clinical features, I'll check them early on because I know it's going to make a difference with my treatment approach. And in patients that maybe it's a little softer call, but they don't respond to IVIG, that's one of the things that I'll go back and look for. Really important to look for those.

Dr. Nevel: What are 2 immune-mediated demyelinating neuropathies that have a fair amount of clinical overlap but do not meet criteria or not included in the CIDP definition?

Dr. Allen: Maybe the 2 most controversial things that weren't included as part of the CIDP under that umbrella is number one, the nodopathies, and number 2, CISP. CISP is a little trickier in whether that's really a different disorder or not. You know, the Mayo

Clinic has done some outstanding work actually biopsying those dorsal nerve roots, and it turns out that the pathology they see is much like what we see in CIDP. So, whether that disorder truly deserves its own label separate from CIDP is, I think, still not a fully told story. But certainly, the nodopathies, there's enough different about them that that's something different than what we typically think about as CIDP.

Dr. Nevel: Great. Does CISP respond to therapy similarly as kind of more typical CIDP?

Dr. Allen: Yeah, it seems to. It seems to respond to steroids and IVIG similar to CIDP. It's a little harder to measure because it is a pure sensory disorder. Diagnosis is really challenging because your nerve conductions, by definition, should be normal because it's all proximal to the dorsal root ganglion. But often you'll see high CSF protein, you'll see enhancement on MRIs. Nobody, or almost nobody outside of Mayo could biopsy those dorsal nerve roots, but if you did, you might see similar changes, and the treatment response should be similar. There's kind of this entity that also goes by CISP+ or sometimes referred to as distal or CISP-plus, where you have pathology of the dorsal root, but it sort of bleeds out beyond the dorsal root ganglion, and you can start to get some sensory involvement, which is probably an extension of that disease as well.

Dr. Nevel: So that segues into my next question, which is, how do you assess for response to treatment? What kind of things are you looking for? Do you have any objective measures that you can use to really determine if somebody's benefiting from the therapy that you're giving them or not?

Dr. Seth: We try to use objective measures in clinic, really, to assess different areas of whether it's causing impairment or disability. Essentially, one is grip strength, so using either Jamar grip strength or a vigorometer to actually measure grip strength improvement as an objective response to treatment over several months. We also use, like our MRC scale, so strength assessment. We use something else called the Inflammatory Neuropathy Cause and Treatment scale, which is a disability score to tell us how much it's impacting the arms and the legs. Those are objective measures. We don't really have a good biomarker as of right now to tell us how active a disease is. There are some that are being studied, such as neurofilament has been studied, paranodin has been studied, but we can't reliably use those right now to tell us if someone's active in their disease.

Dr. Allen: I really love testing grip strength in clinic. And so, the 2 big buckets that I like to look at for following patients with CIDP, one, how are you assessing disability, and 2, how are you assessing impairment? And impairment, it's usually strength impairment. For disability, the I-RODS Disability Scale, I think, is really helpful. It's in the public domain. You can use it. It's a 24-item questionnaire that was developed for folks with CIDP. It's actually patient-reported outcome measures, so what I'll often do is give it to patients either through the electronic record or in paper format while they're sitting in the waiting room or waiting for me to see them, so I have that information available for me. It takes essentially no time and no cost. For grip strength, it takes about 30 seconds to a minute to do that, and you get an immediately available quantifiable result. It's a good

reflection of overall strength impairment or disability in patients with CIDP. So, it's great, and patients love to follow grip strength. I do those for every patient, every visit, follow up prospectively. It tells me something a little more objective about how they're doing disability-wise and how they're doing impairment-wise.

Dr. Nevel: So, thinking about treatment options for people with CIDP, how do you choose between steroids, IVIG, maybe PLEX, maybe some new treatment that I'd love to hear about a little bit, but which one works best?

Dr. Allen: The ones you mentioned, the big 3 that we've used historically for CIDP, IVIG, corticosteroids, and plasma exchange. We know they all work. There's, of course, no head-to-head data, so we don't know which one works better. I think all of the studies that looked at those show response rates for treatment-naive patients between 60 and 80%, maybe up to 90% in one recent IVIG study. But it always comes back in that range. I think which one you start with is one of practicalities, which one we can- Obtain quickly. Comorbidities, of course, play a role in selecting treatments. Putting a patient diabetes on chronic steroids is probably not a good idea. Plasma exchange has some logistical challenges to add to it. So often, IVIG is our go-to, in part because it avoids some of those side effects of some of the other treatments. We know it works, it's proven effective, it's not immunosuppressant, so it's got a really strong role for induction and early maintenance therapy for CIDP.

Dr. Nevel: What's new in treatment in CIDP over the last few years?

Dr. Seth: There have been a lot of new developments that have come out for CIDP. So Fc receptor antagonist, so specifically efgartigimod was studied in CIDP and showed fewer relapse, risk of relapse as compared to placebo. So that was approved actually in June 2024 for CIDP as the 1st new novel therapy. It's pretty easy, once-a-week injections, so it does work decently. I think there's been some concern about switching patients from, let's say, IVIG to that drug, perhaps with some reports of worsening disease status afterwards. So that's being studied and investigated actually in a trial right now. Other drugs that are in the pipeline are complement inhibitors. So, we know complement plays a role in CIDP, and so complement inhibition, specifically with C1 inhibitors and as well C2s are being studied right now.

Dr. Allen: Yeah, I think one of the exciting things in the field is, especially as we move into a landscape that's got more targeted therapies, is if we can take a person with a heterogeneous disease like CIDP and understand which of these options might be the best for an individual person. So right now, all of CIDP and variants we treat in a similar way, usually with immunoglobulin to start with, but we have a hard time understanding which patient might be a better fit for steroids versus immunoglobulin. Maybe we can tweak that a little bit, knowing that there's a small percentage of patients with the motor variant of CIDP that worsen with corticosteroids similar to what happens in MMN patients. So, we might stay away from steroids in that group, but otherwise we treat it very similarly. Now that we've got efgartigimod approved, an FcRn-targeted therapy, how can we better select patients that were good candidates for that and those that maybe aren't so good? I don't have an answer for that right now, but it's something to really keep an eye on and think about how targeted therapies might be applied in

specific clinical scenarios to know where we've got a good match and maybe where a different treatment would be a better option.

Dr. Nevel: Patients are pretty savvy, and they see things online. So, what do you tell your patients who come in and they say, "I see efgartigimod, and I really want to be on it." How do you consider who's appropriate to maybe switch from their current therapy to efgartigimod, and what do you tell your patients?

Dr. Allen: Well, it's always a personalized discussion, where they're coming from, how they've done on their existing treatments, what's the risk and potential benefits. Sometimes we don't know those things, but we can make an assessment. There are certain advantages to efgartigimod from a logistical standpoint. It certainly is a lot easier for patients to get it. It's a subcutaneous injection, pre-filled syringe. You do it once a week. It takes about 60 seconds, which is a far lower treatment burden than IVIG or subcutaneous IG. As Arjun mentioned, there are probably a small group of patients that have a challenging time transitioning from IVIG to an FcRn antagonist. Maybe they are at risk for getting worse. I think that risk is small and uncommon, but it seems to be there. I think there's a couple of red flags for me to say when you should probably stay away from an FcRn and when maybe it's a good idea. And when it's a good idea, I think, is when you have somebody that has clear disease, clearly responding to a treatment like immunoglobulin, but really, really struggles with that treatment, either from a side effect standpoint or a feasibility standpoint. Getting a IV infusion that lasts 3 to 5 hours is just not a good long-term plan. I think those patients are really good candidates for something like efgartigimod or maybe other therapies. On the other hand, if you've got somebody that tolerates immunoglobulin well, they respond well, why switch them? There's probably not a good reason to switch them over to something that may well work, but their current treatment is working well already. I think the other thing to keep an eye on is that the FcRns do a great job at lowering IgG levels and presumably IgG autoantibodies, but they don't do anything to IgM, they don't do anything to IgA. So, if you've got somebody where you suspect maybe there is an IgM or IgA component, maybe you have a monoclonal gammopathy or maybe you've identified some other IgM antibody, ganglioside antibody, certainly those patients I would not switch over to an FcRn. Where it falls in the treatment-naive patient, I think, is something we have to think about more. It's a good option, it's proven effective, but in the absence of head-to-head data with IVIG, knowing which of those is the best is something we need to figure out.

Dr. Nevel: Great. That makes a lot of sense. Thank you both so much for chatting with me today. I really learned a lot and enjoyed hearing all things about CIDP and CIDP-related conditions. Again, today I've been interviewing Doctors Jeff Allen and Arjun Seth about their article on chronic inflammatory demyelinating polyradiculoneuropathy. This article appears in the October 2026 Continuum issue on peripheral nerve and motor neuron disorders. Be sure to check out Continuum Audio episodes from this and other issues. And as always, I urge our listeners to read the article. There's lots more really great information that we just didn't have time to get to today. And thank you to our listeners for joining today, and thank you, Arjun and Jeff, for sharing your expertise with me today.

Dr. Allen: Thank you.

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.