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International Parkinson and Movement Disorder Society
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Functional Tic-Like Behaviors: A Common Comorbidity in Patients with Tourette Syndrome

June 24, 2024
Dr. Müller-Vahl joins the podcast to discuss her retrospective study examining the key features in differentiating Tourette syndrome and Functional tic-like behaviors and that comorbidity is far more common than originally thought. Read the article »

[00:00:07] Dr. Sarah Lidstone: Hello, and welcome to the MDS Podcast, the official podcast of the International Movement Disorders Society. My name is Sarah Lidstone from the University of Toronto, and today I have the pleasure of speaking with Kirsten Müller-Vahl, who is a professor of neurology and psychiatry from Hanover.

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And we're going to be discussing her paper that was published recently in Movement Disorders Clinical Practice, entitled Functional Tic Like Behaviors, A Common Comorbidity in Patients with Tourette's Syndrome. So, welcome Kirsten.

[00:00:38] Dr. Kirsten Müller-Vahl: Hi.

[00:00:39] Dr. Sarah Lidstone: All right, so This is a fantastic paper. It's a very hot topic as you are obviously aware in movement disorders since the pandemic from COVID 19. Many, many papers published around this topic. And so, can you please set the stage for us? You know, at the time when you were pulling these data together, what was the goal of writing this [00:01:00] work?

[00:01:00] Dr. Kirsten Müller-Vahl: So the primary aim of this publication is to make colleagues aware that the presence of functional tic like behaviors is much more common in patients suffering from Tourette's syndrome than we all believed before, including myself. So in recent years, when you also look into the literature, you find only very few publications on this topic.

Because we all thought that movements and vocalizations in those people who are diagnosed with Tourette syndrome or with a chronic tic disorder are always tics, motor tics or vocal tics. And the pandemic was a fantastic education for all of us because in this time we learned how functional tic like behaviors look like.

So it was really important for us to [00:02:00] have this kind of education and thereafter it became clear that there's a large number of people who suffer from Tourette's who in addition have behaviors exactly the same than we see in those patients who suffer from functionality tic behaviors only with our Tics and Tourette syndrome.

And this is what we want to describe here. And I think this is really important because in, In recent years, we often made diagnosis of severely affected patients or of patients who are treatment resistant because of their Tourette syndrome wrongly. And the correct diagnosis would be that they suffer from Tourette syndrome and in addition from functional tic like behaviors.

And because their functional symptoms are so severe, we call them. treatment resistant Tourette syndrome, and in some cases even [00:03:00] decided for incorrect treatments.

[00:03:03] Dr. Sarah Lidstone: Yeah, I do. I was very struck by the proportion of patients who had undergone deep brain stimulation as an example in your in your series, which I'd like to speak about in a few minutes. And this and this paper was pulled together before the proposed clinical criteria for functional tic like behaviors were recently published.

Can you maybe share with us the challenges that you had in defining those clinical criteria in the first place to distinguish between tics and functional tics?

[00:03:31] Dr. Kirsten Müller-Vahl: This is definitely a major limitation of this study because people can argue, okay, what is the rationale behind calling this movement a tic and that movement a functional tic like behavior, although it looks very similar. And I think we still do not have the a clear definition that really can disentangle one from the other, but it's mainly, honestly, it's been mainly based on [00:04:00] clinical experience.

And interestingly when I started some years ago to explain this to my patients, they were more than happy. So in the beginning, I was very hesitating because I felt, okay, I've made the diagnosis of Tourette's, and now I have to explain my patient there's something else, and not all movements, not all vocalizations are indeed tics, and I have to say, sorry, but I overlooked that.

this and sorry, we made some wrong treatments, but it was completely the opposite. Most of the patients really like this new view and most of the patients when discussing this clinical Presentation argued, okay, this was always my feeling that they are two different things and patients were able to differentiate between their primary tics and their functional tic like behaviors.

But yes, we do not [00:05:00] have a biomarker to differentiate between these two things. Two different things, and it's heavily based on clinical experience. It's sad for all those who do not have it. But and we can, of course, give some tips. We can argue that when there's a change in the cause of the disease.

When there is a sudden onset of tic attacks, when there's a sudden off onset of complex vocalizations and complex movements, then please look more carefully whether this is indeed an increase of tics, but this is the only thing we can do.

[00:05:38] Dr. Sarah Lidstone: Yeah, I, I really liked how the attempts to differentiate between these two populations was broadened by not relying only on retrospective clinical criteria, but also looking at influential factors as a thing, as a, as an area that we need to dive into a little bit deeper. And what I really liked about that was how much it aligns with what we observe in functional [00:06:00] movement disorder in general.

Could you, could you share a little bit about the influential factors?

[00:06:05] Dr. Kirsten Müller-Vahl: So this is something we all do. So we have learned that when we see patients suffering from tic disorders that we ask for influential factors. What I now do when I have the feeling that there's also a co morbidity with dysfunctional tic like behaviors. I try to differentiate together with the patient between one and the other symptomatology, and then I start to ask separately for suppressibility, for premonitory urges, and also for environmental or influential factors. And then I asked the same questions once again, but in the first time for tics, for eye blinking, grimacing, things like this. And in the second part for those symptoms who are at least in my impression, clearly functional. And then it's really interesting that you often [00:07:00] receive completely different answers from the patients because for the tics, they report typical symptomatology, but for the functional tic like behaviors, they report a clear difference.

[00:07:13] Dr. Sarah Lidstone: Yeah, there was things around the influence of the environment and specific settings only to have the symptoms or within the presence of specific people in their lives,

[00:07:24] Dr. Kirsten Müller-Vahl: Exactly,

[00:07:25] Dr. Sarah Lidstone: which is not reported in tics.

[00:07:28] Dr. Kirsten Müller-Vahl: exactly, exactly. And therefore, you simply need a lot of questions. So, all these different aspects. are only rarely reported spontaneously, and you have to have in mind what is typical for tics, what is typical for functional tic like behaviors, what we have learned during the pandemic, and then you specifically have to ask for all these different aspects.

[00:07:51] Dr. Sarah Lidstone: And it really illustrates the importance of the history. When establishing these diagnoses, you know, we tend to like to focus on the phenomenology only, but the [00:08:00] history is a really rich source of pre test probability around, around this problem. Can you tell us, about urge and premonitory sensations, right?

This is has been traditionally thought to be a major way to differentiate between tics and functional tics. And, and you found some really interesting results. Did you want to describe that for us?

[00:08:21] Dr. Kirsten Müller-Vahl: So in the past, people thought that functional movement disorders are not associated and even functional tic like behaviors are not associated with premonitory urges. But during the pandemic, we learned that this is incorrect. There have been published some papers who report that there's no difference between these premonitory urges in patients suffering from Tourette's compared to those suffering from tic like behaviors.

But this is, at least in my opinion, not correct because you have to ask more specifically. When you only ask yes or no, then you won't find a difference because people with functional tic like behaviors [00:09:00] often report about premonitory urges. But thereafter, you have to ask more specifically, what exactly do you feel?

How long does this urge last? Can you compare it with something you feel? And then you receive answers you have never heard in people suffering from tic disorders. And then you can clearly differentiate one from the other. 

[00:09:24] Dr. Sarah Lidstone: You know, what's interesting is you actually go on to describe, they're often very somatic, kind of physical symptoms, tingling in the body, these types of things. And, and what struck me when I was reading this paper is that the list of premonitory sensations overlap heavily with what we see in functional dystonic attacks, for example, or a functional tremor, even before the onset of the movement disorder.

So that, I find that quite interesting. Also in terms of the, the psychiatric comorbidity between Tourette's syndrome and functional tics or tic behaviors was quite interesting because I think, as movement disorders, we tend to think that tics have a very [00:10:00] heavy overlap with psychiatric symptoms, but in fact, you found quite quite high rates of that also in the functional tic like behavior.

patients as well.

[00:10:07] Dr. Kirsten Müller-Vahl: So I think this data is still relatively weak because we compared it with a historic sample and tried to find some differences. But we all know that people who suffer from pure Tourette syndrome have a lot of comorbidities. We also know that those who suffer from pure functional tic like behaviors have a lot of comorbidities.

It's mainly anxiety disorders and depression. And those who suffer from both, okay, they also have a lot of comorbidities. And I think we do need more data, more studies to see whether there's indeed a difference. So from our small sample, it seems that we have. Also have a sex difference that more female are affected by this combination.

And we found a little bit more OCD a little bit [00:11:00] more self injurious behavior, a little bit more corporal phenomena. But I would say this has to be replicated before coming to a final conclusion. And in my opinion, comorbidities are not helpful to disentangled, this complex problems you really, really have to decide whether what you see and the history about the symptoms you see and hear whether these are tics or yes or no, this is the most important aspect.

[00:11:30] Dr. Sarah Lidstone: And you, and you did report a striking finding of the presence of other somatic symptoms or other quote unquote medically unexplained symptoms in that population, which does align also with other published works in movement disorders in general, around there being a syndrome as well of other other symptoms.

That's interesting. 

[00:11:48] Dr. Kirsten Müller-Vahl: exactly. And in my experience, you really have to ask for this. People often do not report these symptoms spontaneously, and you have to ask for this. [00:12:00] And when people report about epilepsy, you really have to make clear that these are epileptic seizures because Patients often do not know the correct diagnosis, and you really have to go into this to decide what kind of additional conditions or comorbidities exist.

But yes, it's completely the same compared to other movement disorders, and it's Honestly, it's a little bit surprise because in other movement disorders we know that there may be, or in epilepsy as well, we know that there may be a functional overlay and remarkably in Tourette's we overlooked it for. So many years and I hopefully started a discussion on this and started a discussion on the fact that not all vocalizations, not all movements we see in people suffering from Tourette's are always tics.

This [00:13:00] is the most important message. So in the past, and it includes myself as well. So we all try to find new, dramatic, bizarre symptoms no one has reported before in Tourette patients, including nosy non obscene, socially inappropriate behaviors, all these things. But no one thought about that there might be also.

At least in part, a functional overlay, and I think a little bit we have to rewrite the history of Tourette's because do we know which patients we included in recent studies? Do we really know which patients participated in? Treatment studies, do we really know whether those patients who received deep brain stimulation because they were diagnosed as severely affected in treatment refractory, do we really know that they did not suffer from such a functional overlay with functionality like behaviors?

I'm not sure.

[00:13:59] Dr. Sarah Lidstone: [00:14:00] Yeah, it's really bringing, bringing tics in line with the rest of the evolution of the movement disorders field in general right now, I think with a better diagnostic uptake of FMD in general. What also I found interesting was consistent with other, other areas of functional movement disorder is the striking difference between the, so called objective rating of mild tic severity, which I think was like 63 percent by clinicians, but the severe degree of impairment in the self report when you ask the patients, and I think that was around 80 percent and patients weren't working, they weren't able to, you know, do their basic functions.

Some of them, could you comment on, on that discrepancy?

[00:14:41] Dr. Kirsten Müller-Vahl: So in my clinical experience, it's absolutely rare that a patient suffering even from severe Tourette's syndrome is not able to attend school or is indeed not able to go to work. So this is really rare. And most of these patients really try their [00:15:00] very best to live a normal life and to participate in social activities and so on and so on.

And then those patients who suffer. only or in addition from functional tic like behaviors often report a complete change in their life, in their daily activities. And this is something we saw in a dramatic way during the pandemic, when we had this increase in people suffering from functional tic like behaviors.

And there's a kind of a discrepancy between what you see and what people report. And yes, I would say there's a clear difference between people suffering from Tourette's and those suffering from functional tic like behaviors.

[00:15:47] Dr. Sarah Lidstone: Very practically speaking, you know, for those of us in clinic who encounter these patients, when is it that we should consider? the patient is suffering from functional tic like behaviors or possibly kind of [00:16:00] comorbidity of both tics and functional tic like behaviors.

[00:16:03] Dr. Kirsten Müller-Vahl: So I would say this is the most important question. I would say when a patient reported about a typical history of Tourette's, all what you have learned ever about tics, age at onset, age at maximum spontaneous fluctuations typical influential factors, and then there's a dramatic change in what he reported.

So in other words, he reports about a history of 10 or 15 or 20 years of mild to moderate tics. And then. He reports about a complete change, completely new symptoms occur that never occurred before with an abrupt or dramatic increase of symptoms with loud shouts, with some atypical symptoms you have never heard in general, or only rarely heard in people suffering from Tourette's.[00:17:00] 

You should actively ask about it. The occurrence of so called tic attacks another. important aspect is when a patient reports that treatment was effective, medical treatment was effective for many years, and now it does not work anymore, or treatment that has been used in the past and reduce the ticks, they are completely ineffective now.

So these are the main important aspects. And then in addition, You should ask for other medically unexplained symptoms, and this all together makes the diagnosis. Ideally, you see the symptoms. In those patients where I do not see the symptoms, and this is relatively often, Patients come into my office, I see typical tics, but they report about additional symptoms where I think, oh, this might be a functional tic like behavior.

I ask for videos and this is extremely helpful because then you [00:18:00] see videos from so called tic attacks and then it's absolutely clear that these are no tics.

[00:18:06] Dr. Sarah Lidstone: You mentioned there's the more the lack of rostral caudal progression. There's the more upper limb involvement, kind of more complex movements that are involved. And also the corporal phenomena is much more varied and, and intense. Could you speak a little bit just about those, those key findings clinically? 

[00:18:25] Dr. Kirsten Müller-Vahl: Yeah, yeah. So there's no difference between those people who suffer from Tourette's, Plus comorbid functional tic like behaviors and those who suffer from only functional tic like behaviors. There I see no difference at all and therefore all this is true what, what you just mentioned. So functional tic like behaviors are mainly located at arms, at the body, the head.

They are more complex. They are really stereotypes, so when you see this in your office they can be distracted and [00:19:00] there's more coprophenomena, there's more self hitting and self injurious behavior. So all these typical symptoms we identified during and after the pandemic in all these different samples that has been described in the literature.

Exactly the same symptoms we see in those patients who suffer from both.

[00:19:20] Dr. Sarah Lidstone: So, so going forward, what do you think are the key areas that clinicians need to know? I think you already mentioned. The main point. But any others?

[00:19:32] Dr. Kirsten Müller-Vahl: Yes. I, I think the starting and main point is to think about that patients who suffer from Tourette's and where this diagnosis had been made in the past may in addition suffer from functional tic like behaviors. And this is so important because it's of importance for, for the treatment. So when you decide this is a patient who suffers from.

severe treatment, refractory Tourette's, then you think about pharmacotherapy [00:20:00] and in the end, possibly also about surgical therapy using deep brain stimulation. But it makes a huge difference when you say, okay, he suffers from some mild tics, eye blinking, grimacing, and so on and so on. But the main problem that exists currently are not the tics, but functional tic like behaviors, then you have to say to the patients, okay, if you want to, you can stop all your medication because it's helpless.

It does not improve your functional symptoms, and you definitely have to start psychotherapy. And then, and this is another important message, then these symptoms can be cured. So it's not only a reduction of symptoms what we can offer to tic patients, but we speak about a cure of these symptoms.

And I've mentioned it in the beginning. What I've learned from my patients here in my office is that people are really thankful about this. So doctors should really start. Explaining and asking [00:21:00] patients about this comorbid behaviors and patients will be happy and most of my patients, at least here in my office and say, okay, this is something I've thought.

for a long time that there's something else and not only ticks. And this is really interesting. And a lot of patients immediately after I started this discussion with them are able to differentiate between some symptoms they clearly classify as tics and other symptoms they clearly classify as functional tic like behaviors.

And some of the patients even can differentiate tell spontaneously after I've started and initiated this kind of discussion, they can tell other factors what makes them able to differentiate one from the other.

I tell my patients, you have to understand what happens here because psychoeducation is so very, very [00:22:00] important. And then you have to go to the psychotherapist and have to tell, okay, I suffer from two different things, tics.

 And in addition. Functional tic like behaviors. And this is exactly the reason because I'm here and my functional symptoms are this, that, and that. And please start treating these symptoms. So this is something the patient has to tell to the psychotherapist because most of the psychotherapist will not know these.

Very complex, very new and very difficult aspects.

[00:22:32] Dr. Sarah Lidstone: Well, that's that's a really positive note to end on and and the fact that these are treatable and can be treated using different modalities. It opens up many new avenues for for therapy for these patients. So thank you. Thank you very much for sharing this with us.

[00:22:46] Dr. Kirsten Müller-Vahl: Thank you for having me. [00:23:00] 

Special thank you to:

Prof. Dr. Kirsten R. Müller-Vahl, MD, PhD 
Hannover Medical School 
Hannover, Germany 

Sarah C. Lidstone, MD, PhD, FRCP(C) 

Toronto Western Hospital/Toronto Rehabilitation Institute, University Health Network and University of Toronto

Toronto, Canada 

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