Special Series: Is propriospinal myoclonus a functional movement disorder?

He's a professor of neurology and interface disorders at King's College London, and we will today discuss the topic is propriospinal myoclonus, a functional movement disorder. He was mainly trained at the National Hospital for Neurology at Queen Square London, where he also worked as a consultant.

Later on, he moved to the St. George's University Hospital where he set up a large, very well-known functional movement disorder unit, and he recently moved to Kings College [00:01:00] and mostly hospitals. And his main topics are, as we all know, functional movement disorders, but also dystonia and especially neurology and psychiatry.

In September, during the MDS Congress in Honolulu, he will give the prestigious Stanley Fahn lecture. Congratulations on that mark, and so many thanks for joining me today, and I would say, let's get started.

Prof. Mark Edwards: Thank you. It's a great pleasure to be here today.

Prof. Marina de Koning-Tijssen: Excellent, Mark. To get started, we are gonna talk about propriospinal myoclonus. Could you give a bit of a short overview of the history of propriospinal myoclonus in the literature?

Prof. Mark Edwards: Sure. I think it's important to see propriospinal myoclonus against the background of spinal myoclonus which was a sort of previous concept. And that comes from this idea that there are multiple different levels or generators of myoclonus. So we might [00:02:00] think about cortical myoclonus, brainstem or reticular myoclonus, and then there was spinal myoclonus.

And that was there in the literature for a very long time. So for example, in the mid 1980s, Joe Jankovic read up, a series of 19 cases of spinal segmental myoclonus. And the idea there was that damage within the spinal cord or in the roots, for example you might have myoclonus generated probably because of a reduction in function of spinal interneurons, which then release the anterior horn cell to just generate an impulse and therefore we get a muscle jerk. And that was something where it would be a one or two adjacent spinal segment so the muscles innovated by that would be jerking. It was often rhythmic might continue during sleep and so on. But then in the early 1990s David Marsden, Peter Brown, and John Rothwell, Brian Day, Philip Thompson wrote up a series of three cases.

[00:03:00] Where patients had developed these episodes of very disabling flexion jerks of the abdomen and also involving the knees and hips as well and neck. And the idea here was that that can't really be explained by just one or two adjacent spinal segments. So they propose the idea that maybe there was a dysfunction in longer propiospinal pathways, which were joining multiple segments in the cord. And that was how you generated this sort of flexion jerking phenomenon. And further cases were then described over time, and there was in some of these cases an association with some kind of spinal problem, whether that was a disc prolapse or something more serious.

Like one of the first cases had a cervical hemangioblastoma operation and then they developed the problem. It wasn't until the kind of mid 2000s that people started to bring this idea and that maybe that [00:04:00] wasn't the explanation at least for everybody.

And maybe there was a functional origin for this. So in about 2006, there was a paper that showed that you could voluntarily mimic the same electrophysiological pattern that was recorded. The EMG pattern that was proposed to be something that you saw in propriospinal myoclonus, and then in 2008, that David Williams wrote up the first case of what seemed to be fairly convincingly, a functional propriospinal myoclonus. So a patient with a typical  propriospinal myoclonus pattern, but with a story that really was pretty clearly one of a functional disorder where the whole thing started off after an operation on this lady's brow. She had some sort of surgical procedure done and then it all remitted when screws were removed from this operation in her skull. And that sort of set off a lot of reporting of cases that were presumed of a functional origin. [00:05:00] And then in 2014, Sandra van der Salm, yourself, and me and various others, did a sort of review of all of the cases of what was said to be propriospinal myoclonus in the literature and demonstrating that felt like lots of them had characteristics, either clinically or electrophysiological or both that fitted better with a functional movement disorder rather than something that was damaged to these long propriospinal pathways. 

Prof. Marina de Koning-Tijssen: Okay. You are saying some interesting things about this spinal myoclonus, like the segmental, which we both agree, I think is very rare. That's just very few cases in the literature. In my whole career, I think I've seen two. And I've seen a lot of myoclonus and then this propriospinal myoclonus, which is actually a different form, as you said, and that's also not like during the night.

It's more like in certain postures. And as you [00:06:00] said in 2014, we wrote that review and we still had the idea that some of the cases might be symptomatic. Did you change your idea in the last 11 years on that? Did you see cases in which you considered that it was symptomatic or can you say something about that?

Prof. Mark Edwards: I think it's... from the cases that I've seen. I have not seen a case of propriospinal myoclonus, if we use that term, of this sort of flexion, jerking episodes that I felt was convincingly symptomatic or nonfunctional. I felt that all of the cases that I've seen are functional disorders.

I still accept the fact that these long propriospinal pathways exist. I accept the fact that it could be possible that one could generate a sort of myoclonic disorder from damage to those pathways or other problems within the cord. And there are cases that have [00:07:00] been reports in the literature, which are perhaps more convincing from that point of view. For example cases where jerks have occurred during sleep, although of course that might be a different phenomenon. Or where jerks have been a very, the EMG bursts have been a very short duration. Or have occurred with very short latency from a stimulus.

So I think it's always important to be a bit humble with these things and not make dogmatic, strict statements. My feeling is that if you see somebody with this propriospinal type myoclonus pattern, then the most likely diagnosis by far is that they have a functional movement disorder.

Prof. Marina de Koning-Tijssen: Okay.

Prof. Mark Edwards: But I think one has to keep an open mind on that about whether there could be rarer cases where there's a different cause.

Prof. Marina de Koning-Tijssen: And could you, based on your experience, say, what would be your red flags that you would do additional examinations? When you have a patient [00:08:00] with the symptoms of flexing jerks, mainly when laying down or sitting what would be a red flag for you to do additional investigations?

Prof. Mark Edwards: So to be honest I quite often do additional investigations because I find them important or useful in explanation to patients that this is a functional disorder. I think in general with, jerky movements, it can be more difficult to demonstrate the distractibility. That's a useful part of demonstrating that this is a functional movement disorder that you can use, for example, in tremor. So tremor is something where I think it's generally easier at the bedside to say this is definitely a functional movement sort because look, I can really get this movement to stop or significantly change with distraction.

But, if you spend enough time with people who've got my jerky movement presentations of a functional movement disorder, you can often demonstrate distraction. And if I've convincingly [00:09:00] demonstrated that as part of my assessment, then I don't usually go on to do other tests. But when I've not been able to demonstrate that convincingly.

Then I would often want to do an EMG with back averaging as a way of looking at the characteristics of the myoclonus in a bit more detail and seeing whether there might be a pre movement potential in the EEG.

Prof. Marina de Koning-Tijssen: Okay. And saying that, I recently saw another paper on the parasomnia with propriospinal myoclonus. And could you give some technical advice about how many jerks you have to register before you really are sure that there is not a bereitschaftspotential?

Because I sometimes feel that, that's not always done in the proper way by saying there is no branch of potential.

Prof. Mark Edwards: Yeah I think the first thing to say is that in quite a lot of cases where the disorder is [00:10:00] clearly a functional movement disorder. Even when the recording of the pre movement potential has been done technically well, then there are patients where you do not record that pre movement potential or Bereitschaftspotential.

I think that it's important to average a lot of jerks in order to say that you've got a premium potential or not, and I think that most people want to average about sort of 40 to 60 jerks, something of that region. I don't know whether you would agree with that. 

Prof. Marina de Koning-Tijssen: Yes, I do. Yeah, I think at least 40, but preferably even more to be sure to be able to say it's negative, right?

Prof. Mark Edwards: Yeah, and I mean we were both involved in a study looking at whether there are other electrophysiological markers of being a functional disorder. And we looked at desynchronization of reduction in beta power effectively in the EEG, which is another marker [00:11:00] of a sort of self-paced or a sort of the voluntary movement mechanism starting getting activated like the bereitschaftspotential.

And that seemed to be a little bit more sensitive than the typical bereitschaftspotential. But I think it's like with lots of things in functional disorders you can see the same in tremor for example, that sometimes you need multiple different bit of evidence. That you put together to say this is most likely to be a functional disorder.

Rather than relying on just a single piece of evidence.

Prof. Marina de Koning-Tijssen: Yeah. And then you're saying, I thought that was an interesting remark, that you usually do additional investigations when you consider a functional movement disorder. Or did I misunderstood that, that you said "Just when I don't find the distractibility, then I do additional investigations". 

Prof. Mark Edwards: So I think that there are situations where it's useful to do investigations because you as a clinician are not sure on the basis of your clinical [00:12:00] evaluation. But there are also sometimes situations where they can be helpful to demonstrate to a person why you're saying they have the diagnosis that they have.

If I can demonstrate distractibility at the bedside, that's helpful for me. But it's also helpful in my explanation to the patient 'cause I can show them that distractibility and I can use that as part of my explanation for why I'm saying it's a functional movement disorder, not a different cause of a movement disorder.

But when I can't demonstrate that and I'm saying to the patient, I know because of this pattern and various other things that this is a functional disorder, it can sometimes be useful to have some additional evidence to show to the patient. For example, the presence of a pre-movement potential, like the variability of the EMG bursts or their pattern which allows me to again, explain to them.

This is, a reason, an additional reason why I'm saying that this is a functional disorder and not another cause.

Prof. Marina de Koning-Tijssen: And, just a final question on this. If you have a [00:13:00] patient with a propriospinal myoclonus, what kind of treatment would you advise, if you consider it a functional movement disorder?

Prof. Mark Edwards: So I think that ends up being quite a big, or a complex question to answer because it really very much depends on the patient. So I think the first step is to think of the whole context in which this is happening. So to take kind of various extreme examples, if somebody developed this disorder in the context of a physically or psychologically traumatic event, and they have post-traumatic stress disorder of a very high severity, then I would treat that that would be the first step.

So I think you need to look at it in context, but I think that the, techniques that have been developed from a physiotherapy point of view for functional movement disorders can often be applied very well to people with functional propriospinal myoclonus. Physiotherapists that I've had the good fortune to work with have often used [00:14:00] breathing techniques in people with functional propriospinal myoclonus.

Noting that often there's breath holding or an abnormal breathing pattern, and actually working on control of breathing during attacks seems to be a, quite a nice way in for some people. Obviously that always needs to be started off in the context of a really good diagnostic explanation, explaining why you think it's a functional disorder, the nature of functional disorders, the possibility of improvement.

Through retraining the system and then thinking of all the things that might be keeping it going, both physical and psychological, and trying to get into that.

Prof. Marina de Koning-Tijssen: Thank you. And just a final question on that, because when you look in the literature, then if you look at propriospinal myoclonus, the treatment is like Clonazepam, or some people even consider botulinum toxin or other medication. What is your opinion on that? Do you use that? Do you also use that in patients if you think it's [00:15:00] a functional movement disorder or if it's a non-functional propriospinal myoclonus.

Prof. Mark Edwards: So when I think it's a functional disorder, I do try and avoid medications because I have had patients who are already on medications where they've actually found them helpful. I try to avoid them myself. I think they're not the best way.

They may produce some symptomatic benefit, but I don't think they're the way to really help the problem in the end. I've over time used botulinum toxin in people with functional movement disorders, including functional jerky movement disorders, and my opinion about it has changed a bit over time.

I used it often when I didn't have anything else to do anything else available. But I've had the luck to work in services where I've got good therapists, particularly physiotherapists working there, and I found them to be much more effective than botulinum toxin in the end. And that feels to me like a much more real treatment that has the possibility of getting the person [00:16:00] better.

Prof. Marina de Koning-Tijssen: Okay. Because in the past I've done this randomized control trial and it was effective, but it was as effective as a placebo treatment was, do you have an opinion on that?

Prof. Mark Edwards: So that, that makes sense to me, really, because a lot of the patients that I treated with botulinum toxin clearly had a placebo effect. I was giving them botulinum toxin, but they had an immediate response. I think it, it is something that can work. It's changing people's beliefs and expectations about things.

And that can produce a change in the movement disorder. My problem with that treatment, is that it's a very passive treatment, so the person is getting better. At the hands of the doctor a little bit by magic rather than by actually having any agency and understanding how they might be able to control the movement.

And that feels to me to be the thing that really is about getting better, that would give control back to the patient [00:17:00] over their own body. And that's the thing we're trying to achieve in treatment, if possible.

Prof. Marina de Koning-Tijssen: Yes. You could imagine perhaps sometimes that you could use it once to sort of interrupt the circle and then get started with physiotherapy. Right?

Prof. Mark Edwards: I agree. I mean, I have used it that way and I continue to use it that way actually in some people with fixed dystonia. So it's functional, fixed postures where actually I think the botulinum toxin may have a direct effect on some aspects of pain and of tension within muscles.

And it's like a way in to try and get some movement to happen. But I would always in that situation, explain to the patient that I'm giving you the botulinum toxin to try and just turn things down a bit to allow you to get on with the real treatment, which is the rehabilitation that you need.

Prof. Marina de Koning-Tijssen: In my experience, it's hard then to stop it again. 

Prof. Mark Edwards: It really is. It really is.

Prof. Marina de Koning-Tijssen: So you really have to think about it. If you want to get it started.

Prof. Mark Edwards: Yes.

Prof. Marina de Koning-Tijssen: I [00:18:00] think it's a difficult decision sometimes.

Prof. Mark Edwards: I think that what it says to me is that we really need a good set of tools. If you're seeing people with functional movement disorders, then you really need a good set of therapeutic tools. And so you need access to rehabilitative treatments, both physical and psychological. Because otherwise you're left in this situation where you have to do things which are not the best, not optimal. So it's true, you can get some people improved with botulinum toxin or by giving them Clonazepam or doing lots of other things, but it's just not the optimal thing to do. And you end up in situations, like you say, where people are stuck on treatments, they may be getting side effects if they're on medication, for example.

It's another example of needing good access to rehabilitative services. When you're seeing people with FMD. 

Prof. Marina de Koning-Tijssen: Well, thank you so much, Mark. If I would rather wrap it up, I think you would say that [00:19:00] propriospinal myoclonus is in most of the cases a functional movement disorder. And so that's the way clinicians should approach it, but always keep an eye on that it might be secondary to some lesion as based on the anatomy, it could be possible that those tracks are affected. And for the treatment I think you gave us a very good insight in how you treat these patients in your clinic, and thank you so much for that, that you wanted to join me today and it was great to listen and to see you again.

Prof. Mark Edwards: Thanks, Marina. It was great to be here. Thanks very much. [00:20:00]