Functional Movement Disorders | Congress 2026

Dr. Sarah Lidstone: You are so welcome, and it's an absolute pleasure to be back on the podcast.

Ms. Nicole Duff: So, I am going to say that I heard you talk in Boston at the FND conference a few years ago, and since then I've followed and loved your work, and I'm so excited that we have this time to be able to sit and chat about the field of FND. You did a talk yesterday on FMD specifically. First, can you explain the difference [00:01:00] between FND and FMD?

Dr. Sarah Lidstone: Such a good question. I know it's getting a bit blurry, isn't it? The boundaries there. And thank you for your kind words.

I think about FND, or functional neurological disorder, as being the overarching umbrella term, and underneath that are a number of different presentations that can occur. And so functional movement disorder would be one of those. But then also we could include functional seizures, functional vestibular disorders, functional cognitive disorder, functional sensory symptoms.

And so FMD is a term that I like to use. I have developed an approach actually as to when I use that term. And I did speak about this a little bit yesterday because I think it's very different if you have an individual, for example, that has a functional tremor only, isolated functional tremor.

And then we see patients that have a number of different functional movement disorders at the same time. So they may have functional dystonia, functional gait disorder, and a functional tremor. And there I would then actually generalize a little bit and say more of an FMD presentation rather than [00:02:00] an isolated functional tremor.

I think we can have individual presentations of each of these different phenotypes within FMD as its own umbrella term. But I also think sometimes it's helpful to blend those together if somebody has a number of different, separate movement disorders into a functional movement disorder as its own thing.

Ms. Nicole Duff: Perfect. Thank you. It makes so much sense, and I think that for people who are still learning about FMD, it just gives a sense of peace of, okay, if I'm not understanding it all correctly, it's not the end of the world. It all kind of fits in together, but if I don't know the exact specifics, it's not the end of the world.

Part of the talk yesterday focused on diagnostic features of FMD. So could you elaborate on some of those for us?

Dr. Sarah Lidstone: Movement disorders has really led the way I think in a rule-in approach to diagnosing FMD. And that's because we have all these fantastic maneuvers that we can do on the physical examination that [00:03:00] demonstrate the features, the hallmark features of a functional symptom, which essentially is that it is inconsistent by definition.

A non-lesional network-based symptom is changing over time. So it's present at one minute and then gone the next minute, and this can be within a day or between days. That inconsistency is really an important feature. And then also variability, which refers to the movement disorder itself is always changing.

So an example would be a functional tremor where it's migrating to different body parts. It may have a different amplitude, a different frequency. It may arise during different provocative maneuvers, and so that's variability. So intrinsically, the symptom is changing around. They're all distractible.

So when the brain's attention is focused on something different, off the body, whatever that would be, then the symptom tends to be improved. And conversely, the corollary of that is it's enhanced with attention. So when the individual, [00:04:00] when the brain is focused on the symptom, on that body part, then it tends to be exacerbated and is worse.

Incongruency is the final one, which really refers to the fact that we, in general, know how kind of the laws of neuroscience and neuroanatomy and neurophysiology, how most of these symptoms in movement disorders are going to be showing up. We understand what a cerebellar syndrome looks like. We understand what parkinsonism related to nigral degeneration will look like.

We know upper motor neuron signs, lower motor neuron signs, and these features. But because, by their nature, these are network-based disorders that are utilizing voluntary motor pathways, they're not going to obey those same laws, and so they'll be incongruent to what we know about existing presentations.

Now, I will add a caveat to that, which is that among FND-ologists like myself and others in the field, we are solely trying to shift away from incongruency and de-prioritizing it in the diagnostic criteria. And that's simply because, at the heart of it, it's also saying that it is a rule-out thing.

It also implies [00:05:00] that we are omniscient around all of the various presentations of everything in neurology, which, we're discovering new mutations all the time, new disorders all the time. They have different clinical features, and so I think it behooves us to not attach too much weight to incongruency as the sole.

Ms. Nicole Duff: Thank you. I think sometimes all those words blend together. So to have them teased out and explained exactly what each one means has been so helpful. I'd also heard that you were trying to move away from the incongruency, and I wasn't exactly sure why. This makes complete sense, and so thank you for explaining it.

So now that you've done all your diagnostic features, the tough part comes when you're sitting in front of your patient and you have to explain to them what you found. Can you explain to us how you would start that conversation?

Dr. Sarah Lidstone: It's such a good question. And as we were preparing for this interview I was sharing with you that most of the questions we had yesterday in the session were actually about the communication and about treatment.

And I think this is an area that many neurologists really struggle [00:06:00] with. These are really excellent, very well-trained, empathetic, smart, movement disorders neurologists who are struggling with this area, and there really is a gap there. And it is an art, actually, I think the...

Communicating this to a patient, like any diagnosis, does have a component of an art or communication skills that I think can be trained. I would actually back up a little bit and say that, you have to recognize that this population inherently have often had a series of negative healthcare experiences when they're coming in to see you.

By the time they see most people in this audience of this podcast, which is a subspecialist in movement disorders, they've probably already seen their general practitioner, if they have one, maybe an emergency physician, maybe several times an emergency room physician. They may have seen other specialists related to the other functional symptoms they may have.

If they have a concussion, if they have gastric symptoms, and so they've interacted with the healthcare system usually a lot before they [00:07:00] even see you, probably a number of tests and so forth. And the resounding survey results from patients is that they often feel dismissed, they often feel invalidated, and that they're not believed.

I think there's a lot happening there. There's a whole separate podcast around the stigma and the cultural attitudes towards mental health and how that informs things. But regardless of the reasons, patients can be mistrustful. And so it's not like you can do your regular consult your regular way, and then now all of a sudden turn on your super communicator skills

Dr. Sarah Lidstone: when it comes time to convey the diagnosis. It actually starts in the visit itself. It's the body language about how you show the patient that you're listening actively. It's understanding their top concerns. It's demonstrating empathy and, especially, validating their symptoms and believing them when they tell you that they have weakness or they have a tremor.

And even if you may not see it on your exam, because these symptoms fluctuate and are inherently inconsistent, what they're [00:08:00] reporting is what they're experiencing, and we have to believe people. I think if that is done well during the assessment itself, the work of a diagnostic delivery, quote unquote, there's much less heavy lifting to be done.

And so I follow a general rule where I will always do a good thorough kind of history, always do a good personal history to understand what stressors somebody might be encountering, which is important in all of medicine anyways and actually is an opportunity to demonstrate empathy to the patient.

I do a head-to-toe good screen neurological exam, and whenever I see a positive sign, I tell the patient in real time, "I'm noticing this. Isn't that interesting?" So if I do a Hoover sign and can show them that, "Hey, at this point, your leg is really weak, and I can see that you can't move it. But now look, automatically it's stronger when you lift the other side."

That's a powerful moment for the patient to see. Same thing with a tremor. If I can see the tremor is distractible when they go into their purse to grab something, or they're doing a transfer from the chair to the examining [00:09:00] table or something like that, or from seated to standing. Whatever the opportunities are, I will point it out to the person in real time, and then when I tell them, "You have a functional movement disorder.

Have you heard of that before?" Explain what it is. I say, "It's a problem with communication in the nervous system. The hallmark of these symptoms is that they're changing, which is exactly what you told me on the history and what I've seen on the exam." And then I will, in that discussion, illustrate then, I'll actually list the points in the exam where we saw that together, right?

So I'm bringing it back to the patient's own experiences to really personalize that diagnosis delivery, which I think has a much higher chance of uptake than a standard stock phrase that you can use because it really accurately describes their experience. And then, answer their questions around it and let them have a chance to share what they think about that.

Many people come in with very different amounts of information. They may have been privy to really good resources like neurosymptoms.org or there's some good content on YouTube, other types of [00:10:00] medical education, and they can also have a lot of misinformation and bad stereotypes as well.

So it's a good opportunity to explore their understanding a little bit and provide good resources there. So that's a very long answer to your very short question, but I hope that kind of helps show how it's more of a process than it is a kind of single point in time in an assessment.

Ms. Nicole Duff: I appreciate the answer because I think that a lengthy answer demonstrates a lengthy process, as you've said. Do you think that the more doctors understand about the condition, the better the communication of the diagnosis will be? 

Dr. Sarah Lidstone: Yeah, I think that's a big part of it. Educating our clinicians is always a gap. I just came from our FMD Study Group meeting, and we had people speaking to us from Malaysia and from Argentina and from El Salvador who they're all saying the same things. It's that there aren't enough providers.

Providers don't know how to diagnose or communicate FND, and there's no resources to treat it. And of course, [00:11:00] that then trickles down to the patients because the patients learn about these things through us.

It's clearly a linear relationship, right? Research and the outcomes of studies really inform how we look at disorders, and there's fantastic research happening now in terms of the pathophysiology of FMD, involving agency networks and interoceptive networks and attentional mechanisms, and all of these are interplaying together.

And I think that gives a kind of a credibility, quote-unquote, right? The message to people is that there is a lesion, it's dynamic, it's changing. Mark Hallett has said this many times before, the late Mark Hallett. And so having some idea about the kind of basic nuts and bolts of what's going on from a neuroscience level, I think does make providers more confident and comfortable sharing this with patients, and why we can't see it on an MRI, why we can't see it on a blood test, for example.

Ms. Nicole Duff: Thank you. So, FMD in its broader sense can be broken down into your hypo- and your [00:12:00] hyperkinetic movement disorders. Could you tell us briefly if that fits in with your general movement disorders? If there would be the same, your functional movement disorders mirroring your general movement disorders, or if it would be different?

Dr. Sarah Lidstone: Yeah, I think we're still understanding how to categorize. The more that we learn about the brain and about the crosstalk in networks between neurology, psychiatry, but it's more of a, kind of a transdiagnostic approach where we're looking at brain function in terms of mechanism that cuts across both neurological disease and psychiatric disease.

 I think we have to evolve how we categorize a lot of these illnesses. For the average movement disorder specialist, it makes a lot of sense to approach FMD in terms of excess movement and hypofunction. The hyperkinetic and typically I think movement disorders tend to be biased towards hyperkinetic FMD presentations.

The more hypofunction or weak, let's say [00:13:00] weakness, more sensory symptoms, those patients tend to present more, let's say, to a neuromuscular subspecialist, for example. And so we don't see them often in movement disorders clinic because they don't attract as much attention. But things like functional myoclonus, functional tremor, functional dystonia,

 functional gait disorders, more hyperkinetic presentations. And the hypokinetic, as I mentioned, kind of weakness. Fixed dystonia, hard to categorize. I think probably more on the hyperkinetic side. So we could look at things more in that framing, I think.

It's not a bad idea.

Ms. Nicole Duff: Thank you. Yeah, that makes complete sense. So, FMD is now diagnosed on positive signs, as you'd mentioned, not exclusion of diagnosis.

What still gets misunderstood about that shift?

Dr. Sarah Lidstone: When I first began my training as a fellow, I was recognizing positive signs on an exam of a patient, let's say, with functional tremor or gait disorder. But within any given patient, it was their diagnosis was the functional version [00:14:00] of this, quote-unquote, "organic movement disorder."

So it's every presentation had a functional version and an organic or real or true version, right? That's the implication there. And the truth is, if we look at the data, most patients, the most common presentation of FMD is actually a mixed presentation, where they have a number of different functional phenotypes at the same time.

And so we have to think about the disorder a bit differently and not miss the forest for the trees. We can still rule that in, but I think it's understanding that FND has its own rules, and this is stable across cultures. It's stable over the history of medicine,

based on really excellent kind of old archival photos and videos after the war and in Charcot's time and so forth.

They obey their own rules. They have their own historical features. They have their own examination features and their own comorbidities and all of that. It's its own entity. So I think that might get lost a little bit in shifting from a rule-out to a rule-in. Another area people struggle with a [00:15:00] lot is the comorbidity with other neurological disease.

So 30% of patients with FND will also have another neurological illness. We see this a lot in epilepsy, where they'll have epileptic seizures and functional seizures. We'll see it in Parkinson's disease, where they have functional tremor, and then they have maybe parkinsonian tremor at the same time or even go on to develop Parkinson's disease.

I think this speaks to, again, more of a sophisticated understanding of brain function and how our networks respond actually to lesions in the brain and a disease process happening. There's downstream effects that happen at a network level, which could be manifest as functional symptoms, right?

We still don't know. There's a huge amount of work that has to go into this area, but it's hard for a practitioner to be simultaneously having to make two diagnoses in the same visit. I have a lot of empathy for that because that can be very challenging. But I think that is an area, because I think in medicine, at least in this area, there was a tendency to be all one thing or another.

And that approach, unfortunately, doesn't work super well when it comes [00:16:00] to FND.

Ms. Nicole Duff: Thank you. That makes complete sense, and I think leads you down the path of thinking exactly around ... and I know the term nowadays isn't functional overlay ... but exactly where you have these two conditions. So what FMD condition would you say is the most commonly misdiagnosed?

Dr. Sarah Lidstone: Out of FMD, functional movement disorder?

Ms. Nicole Duff: Or, let's speak more broadly, FND.

Dr. Sarah Lidstone: Yeah, I don't actually know. I don't know if there's data on that. We do have data about FND in general and about accuracy of diagnosis, which is, it's very readily diagnosable and it's quite accurate, and that's been stable since the 1970s. And that's older data, but it still holds true.

I think functional dystonia represents a pretty big area of challenge for people, and that's because investigations aren't super helpful always. We have

been able to very confidently say that there's specific phenotypes of dystonia that are almost pathognomonic for FMD, [00:17:00] which would be the functional dystonic facial spasms, where the platysma is overactivated and pulls the corner of the lip down.

In the hand or the upper limb, it's kind of flexion of the last three digits that spares the pincer grasp. That's generally functional. And in the lower limb, it would be kind of plantar flexion inversion of the foot, either unilaterally or bilaterally. And those are, pretty clearly, we know that's going to be a functional dystonia picture.

But more episodic symptoms, it can be challenging, right? There's a differential around paroxysmal kinesigenic dyskinesia. These are rarer channelopathies but are still entering into the picture. Tremor can still be really difficult. There's people that will have, for example, a coexisting enhanced physiologic tremor and also functional tremor, or again, that kind of comorbidity.

And then gait disorders, again, some of these much more rarer genetic presentations can present with really unusual-looking gaits. And again, taking kind of an older rule-out approach doesn't really work as well for those individuals.

Ms. Nicole Duff: [00:18:00] Thank you. I remember way back when I was taught about the functional gait disorders, I was just taught if they can walk backwards fine

and they can't walk forwards, then that's a functional gait disorder. Which, I think it's evolved so much.

Dr. Sarah Lidstone: That would apply to focal or limb dystonia, too, so not specific. 

Ms. Nicole Duff: So you mentioned some of these special investigations or ancillary investigations that we might have done as an addition to your general neurological investigation. Can you maybe just explain a few of those? 

Dr. Sarah Lidstone: For sure. In general, you approach investigations the same way in FND as you would in any neurological illness, right? Your history and your examination guide your differential. The key thing I would just asterisk here is just make sure you have FND on the differential if you're thinking about it.

And then you can select an investigation that will help rule in FND, which is not really a thing yet because we don't have good biological markers for this so I would put a little [00:19:00] placeholder there for now. But often we're doing them to rule out the presence of comorbid neurological illness in cases where there could be some ambiguity there.

And of course, we want to make sure that there's good neuraxis imaging, MRI of brain and spine, video EEG in the case of dissociative functional seizures and epilepsy, and that distinction. EMG can be very helpful and EEG and also when we combine the two together for functional myoclonus, for example, when we're doing cortical back-averaging, that can be helpful in functional myoclonus.

But, the average neurologist won't have access to fancier more movement disorders-specific electrophysiology. If you do have that, you're very lucky because then you can do some much more nuanced studies around functional myoclonic or kind of undifferentiated myoclonic presentations, tremor, and sometimes dystonia.

Although dystonia, because the net result is excessive muscle contraction, you can't diagnose that alone. But again, with a good history and a good physical altogether, that can be [00:20:00] useful. So I think, for me, it's usually if those investigations haven't been done, I will order them if necessary.

Blood tests and CSF markers can be important, too. But it's just being a good clinician. There's nothing specific about FND that is a recipe for investigations, but it's making sure nothing's been missed, very often. And how you frame it to the patient is crucial as well, right?

Because we're not wanting to give them the impression that if this test is negative, then you have FND. That's, I think, what a lot of people approach it as, relying on the test to convey that message. But instead it's you have the positive signs, you have FND, let's make sure there isn't anything else going on that could be contributing to the picture, and then you can order the test.

Ms. Nicole Duff: So that was going to be my next question, if ordering these other investigations could ever be damaging to the patient, particularly to their psyche?

Dr. Sarah Lidstone: Yeah, that's such a big question, right? There's so much that goes into that, but I think, that would be true of any investigation in medicine. We can always have incidental findings. There's nothing really different about FND in that regard. I think where people [00:21:00] run into a little bit of trouble is there are a portion of patients with FND, because as a group they tend to be more somatically preoccupied and because they've had often, again, these kind of negative healthcare experiences, there tends to be a feeling among clinicians that they have to prove to them that everything is normal before that it can be FND, and you get into this quagmire that can be really difficult to get yourself out of.

And so, again, it comes back to how this is communicated to patients.

Ms. Nicole Duff: Brilliant. Thank you. I didn't mention at the start, but you are the director of the Integrated Movement Disorders Program, which is an interdisciplinary precision rehabilitation program. And firstly, can you explain the concept of interdisciplinary rehab?

Dr. Sarah Lidstone: Yes, and I love that you're a physio. We can chat about it. We can all agree that interdisciplinary, multidisciplinary care is necessary in medicine, especially in neurological illness, and especially in more chronic kind of neurological illnesses. In our program, [00:22:00] we realize that FND, like most movement disorders actually, are neuropsychiatric presentations.

Most people that have it, including Parkinson's disease, ataxia, dystonia, they all have a spectrum of symptoms across the mind-body interface. And mind and body really strongly inform each other, especially in a rehab context. So one example I could use would be Parkinson's disease, right?

If you have a patient with Parkinson's disease who could benefit from physiotherapy and learning the skills necessary to live with their Parkinson's, including big movements, large amplitude movements, postural exercise, those kinds of things. If they are limited by low motivation and apathy because of their low dopamine levels, then rehab isn't really going to be effective. And so there's always a kind of mind and behavioral component, I think, to all rehabilitation. Anxiety, which is so common in the population, very common in this population specifically, really informs motor [00:23:00] control. Balance, gait is hugely informed by anxiety. Freezing of gait, all of these things.

My view out of the gates really is that all rehab should be interdisciplinary because right now we still don't have a single profession within healthcare that can do all of those things by themself. So we need a team of people, and what's really crucial, I think, is that team look at the problem the same way, use the same language, have the same perspective, learn from each other, share skills, and this way it's so much less confusing for the patient, and all of a sudden they then have a language and a way to look at the problem and their bodies, and that can be built into the interventions.

It's a really kind of harmonious approach. And it's very clinically rewarding, and the outcomes also speak for themselves, right? Patients do very well with this model. FND, fundamentally, a lot of people have had this dualistic approach and the split of mind and body and [00:24:00] brain.

And if the team actually exemplifies that integration itself, we're modeling how we're trying to treat the nervous system itself. It's a meta idea, but everyone's in the same group.

Ms. Nicole Duff: Thank you. Within your team how would each person's role contribute towards diagnosis?

Dr. Sarah Lidstone: Diagnosis is a bit trickier, right? It's not that my psychotherapist could confidently diagnose FMD, that's for sure. Our physio is pretty good, right? You work together long enough and enough patients, there's obviously like a referral bias that's there. So I think with diagnosis, that still would be the role probably of the neurologist, if it's a new diagnosis especially.

But I think the role there is, in the diagnostic process I was alluding to earlier in our conversation, is that if the team speaks the same language, uses the same models, it's a seamless transition between the patient leaving my office and then beginning a course of physiotherapy. They're hearing the same messages.

And that's [00:25:00] crucial because people with functional symptoms often have never heard of this before. It's hard to conceptualize a physical symptom in the body if they can't point to the place on the scan that it's broken. So they need a way of looking at the problem.

They need a model to understand that. In our team, because we've worked together for a long time, but also anybody doing FND work in general, we all tend to use these same educational models and analogies about how to explain the problem. And if everyone's using those same analogies, then the patient really begins to understand what's going on in their nervous system, or at least have a way of looking at it.

And I think it, it really kickstarts their recovery actually. Because they have to do less work to understand their own symptom patterns, which is crucial actually to long-term recovery, is understanding. "Why am I getting a flare on Wednesday morning?" "Oh, I actually didn't sleep well the night before. Ah, I understand. This makes sense now. My brain is overwhelmed and I need to do my skills or strategies," or what have you, right? So that's where the team can be really helpful in that transition between diagnosis and recovery.

Ms. Nicole Duff: [00:26:00] Thank you. And I'm sure that treatment is accelerated in a way because having the same message repeated over and over allows them to get in touch with what's happening in their body so much quicker ... because they're having this reinforced in a positive way all the time. So I'm sure that model, as you're saying, and that reframing 

really helps encourage them in their treatment, understand where their treatment is going. So I think the model it's amazing. As you say, as a physio, I think it's amazing being included with that forward thinking of let's all do it together versus these silos.

Dr. Sarah Lidstone: It's validating, too, that's a big part of it. It's like, "Oh the neurologist believes I have a real problem," and "wow, I talk with physiotherapists and they're a physio who understands this condition." It's like, "Oh my gosh, it's a real thing."

We can't underestimate the impact that actually has on how the patients are feeling and their recovery.

Ms. Nicole Duff: So, what research question in [00:27:00] FMD or FND are you the most excited about at the moment?

Dr. Sarah Lidstone: I'm most excited about all the excellent work that's going on around mechanisms. We have so many different groups all over the world who are doing fantastic work around genetics, around neuroimaging, and we're learning so much about these kind of network brain dysfunctions that I think is really fascinating.

The work on agency, the work on predictive coding, the work on interoception is really interesting. And, the advent of AI is really helping bring teams across the world closer together, communicate more freely, and do more data analysis in larger groups.

It's been this way for a while, but it's a renaissance in FND, in terms of brain function, because now we actually have the technology has caught up to our ideas. And we're able to delve into these areas a lot more deeply. So it's the next 5, 10 years are going to be very exciting in this field.

Ms. Nicole Duff: Awesome. And then one take-home message, if you can squeeze us all into one, for everyone listening?

Dr. Sarah Lidstone: I have three, but they're very short. 

FND is rule in. Comorbidity exists, don't [00:28:00] be scared to make two diagnoses. And the last thing I'll say is inconsistency is really the key. It's the key on the history, it's the key on the exam, and it's actually the key in guiding treatment.

So get good at doing it, and have fun with it, and be creative in your clinic.

Ms. Nicole Duff: Thank you. My take-home message would be having the passion of being with your patients and caring for your patients that you have, which is so evident, and I hope that everyone can hear that and try and replicate it.

So yes, thank you so much for your time. It's been so wonderful chatting with you.

Dr. Sarah Lidstone: Thank you so much. Such a pleasure to be here. [00:29:00]