Incongruence in FND: time for retirement 2024 Stone

[Andy]

[Don't get your hopes up, this is not Stone's announcement of his retirement]

The diagnosis of functional neurological disorder (FND) has rested traditionally on two key features: inconsistency and incongruency.

Inconsistency usually refers to inconsistency between movement, sensory or cognitive performance in a voluntary versus an ‘automatic’ scenario. This is the principle of Hoover’s sign of functional leg weakness, the tremor entrainment test for functional tremor and a range of cognitive tests in functional cognitive disorder. It is often helpful to share these tests with patients as they show the potential for improvement, give an insight into the ‘software’ mechanism of FND in the brain and also feed into a range of FND-specific therapies. For example, a physiotherapist might actively use distraction to promote automatic movement and discourage overlearned abnormal patterns of voluntary movement.

Incongruency, on the other hand, refers to a clinical feature that is not present in other superficially similar neurological conditions, or that apparently violates laws of anatomy, biology or physics. I have always struggled with incongruency in FND but now am breaking my silence, assisted by the intriguing case of a patient with ‘functional freezing of gait’ from Jorik Nonnekes and colleagues in this issue of Practical Neurology.1

The patient described in the paper and accompanying video has a functional gait disorder. But is it reasonable, as the authors suggest, to make that diagnosis, in part, because it does not look like another disorder, principally Parkinsonism, with which we are more familiar?

In my view, incongruence needs retirement. It should be sent to the FND section of the neuromythology graveyard where it can join ‘la belle indifférence’,2 ‘non-organic’3 and the universal application of ‘conversion disorder’.4 Here is what I object to, and find incongruent, about this sign still being used in the clinical assessment of FND (box 1).

Paywall, https://pn.bmj.com/content/early/2024/01/11/pn-2023-003897

 

[Sid]

• Incongruence is just another way of making a diagnosis of exclusion. What other diagnosis in neurology do we make just because it does not look like something else? Could there be any more insecure and unsatisfactory way to diagnose, and explain a condition both to ourselves and our patients? If we translate that to a similar situation in clinical neurology the absurdity reveals itself: ‘I think you have epilepsy. I know that because your attacks look nothing like syncope’.
  
  
• Incongruence requires omniscience in clinical neurology. For a long time, I have been waiting to feel that I had seen enough neurology to know what was truly incongruent. Now I am older I realise that this is never going to happen. There are many neurologists more knowledgeable than me, but the omniscience required for the true application of incongruence is not practically achievable.
  
  
• Incongruence is not future proof. We are discovering new kinds of ‘bizarre’ clinical features all the time that do not look like conditions we are used to. Think of faciobrachial dystonia in LGi1 encephalitis or a ‘hobby horse gait’ in DYT-4. What is incongruent today may not be tomorrow. We should not be diagnosing FND just because we think it is ‘bizarre’.
  
  
• Incongruency presumes we know all there is to know about anatomy. We are gaining new understanding all the time about how the brain works, which means our pronouncements that deficits are ‘non-anatomical’, based on standard neuroanatomy, are now out of date. The predictive processing model of brain functioning is one that makes sense of a range of hitherto hard-to-understand conditions such as phantom limb phenomena. There is a good argument that FND is a disorder that ought to exist if we believe that the brain works in part by predicting bodily states and variably responding to sensory input that tries to correct those predictions.

Very surprising to see these statements exhibiting humility from Stone. Encouraging development.

 

[Sean]

Meh. He is still clinging just as tightly onto the whole FND project.

I don't see much practical distinction between incongruency and inconsistency. The comments he makes on the problems with incongruency could be applied to inconsistency too.

 

[rvallee]

the neuromythology graveyard where it can join ‘la belle indifférence’,2 ‘non-organic’3 and the universal application of ‘conversion disorder’

I guess that semetary is brought to us by Stephen King, because the corpses of those ideas are shambling around and although they may suffer from the odd gait disorder, are very much indistinguishable from alive and kicking.

This is the stuff that makes what sounds like a bit of a breakthrough entirely forgettable. Because these people never give up on their myths, they just describe them differently. Same as it ever was. They are zombie beliefs, impossible to kill. FFS the 'non-organic' stuff is still the main excuse they still use, and there he pretends that the idea is dead. Usual nonsense from people who can't tell the difference between reality and the thoughts in their heads.

 

[Sean]

Once upon a time neurology was absolutely sure that the reports from MS patients about monocular diplopia (double images in one eye) were impossible (inconsistent with the laws of physics, to use Stone's phrase in this paper), and indeed evidence of some form of psychopathology. Until it wasn't, and is now a completely accepted phenomenon.

Yet Stone seems untroubled by asserting that reports of tunnel vision issues in FND are inconsistent with the laws of physics.

There is certainly inconsistency here. Just not in patients reports of their experience. It lies in the interpretations into which the experts are trying to shoehorn those stubborn facts.

 

[SNT Gatchaman]

He's updated that idea in this paper —

In functional visual loss, it is often said (including by me8) that a tubular visual field is incongruent with the laws of physics—visual fields should expand conically the further away the examiner is (figure 1). That is true, but a tubular visual field is also typical of a functional visual disorder. It is congruent with the prediction operating at a brain level and below awareness, that there is ‘tunnel vision’. In the face of such a strong prediction, the FND visual brain ignores sensory input to the contrary. There is nothing ‘non-anatomic’ going on. It is in keeping with the functional neuroanatomy of symptom experience and what you would expect of abnormally strong predictive machinery in the brain.9

Explaining to a patient that their symptoms break the laws of physics may be a shortcut for the clinician wanting to reassure that the hardware is ok, but for the patient is likely to be heard as ‘you shouldn’t be having that symptom, that’s not possible’. Explaining why their symptom breaks the laws of physics, ‘your brain has decided there is a tunnel—so it doesn’t matter what it actually sees’, is perhaps a more satisfying explanation all round.

 

[Andy]

Unless his future actions and words prove otherwise, I assume that this is just more positioning to attempt to maintain FND concepts as relevant, rather than accepting that it is a waiting room for issues that currently science either can't explain or hasn't properly investigated. Even him thinking that is is OK to explain "why their symptom breaks the laws of physics" shows that he is absolutely fine deceiving patients, just so the explanation can be "satisfying".

 

[dave30th]

. He is still clinging just as tightly onto the whole FND project.

I don't see much practical distinction between incongruency and inconsistency. The comments he makes on the problems with incongruency could be applied to inconsistency too.

This is how it seems to me.

 

[Jonathan Edwards]

I don't see much practical distinction between incongruency and inconsistency.

There is actually a clear difference and I think he is making a vlid point - but for the wrong motivation.

Making a neurological diagnosis always involves gathering about 100 pieces of information and working out what consistent patterns emerge. If the left arm is weak and the left leg is weak and the visual field is blank on the left you have a right internal capsule bleed very likely. If position sense is lost in both feet and hands you likely have a dorsal column peripheral neuropathy but not if one foot is fine. If weakness in one leg is associated with an upping planter response the diagnostic possibilities are quite different from a downing response. And so on.

Inconsistency of pattern is the backbone of all neurological diagnosis. You use it to narrow down a thousand possibilities to one. Hoover's test uses the same principle and has to be considered legitimate - as long as the clinician has genuinely covered all the evidence.

But incongruity, in the sense of something unfamiliar, is not a legitimate reason to diagnose nothing wrong. However, it is a very common lazy habit of doctors to do so. Stone is quite right to point this out but 1. All doctors should know it anyway.
And 2. He is using it to imply that FND is not incongruous but stereotypic and recognisable by positive sigs. He is at the same old game, but the distinction is very sound.

 

[rvallee]

He's updated that idea in this paper —

Good grief the pseudoscience is off the charts. The misuse of "not possible by the laws of physics" should never be acceptable, but they make it clear that they intend to keep on deceiving patients using sciency sounding fake explanations precisely because they sound more credible by misusing scientific language and concepts.

In a way, they are perfecting pseudoscience, creating the Platonic ideal of what pseudoscience is all about, especially the very explicit intent to deceive.

 

[ToneAl]

He is still clinging on to the predictive coding model even though it doesn't work as suggested. Fnd is a learner behaviour problem according to him but as knowledge of anatomy increases many of these problems may be biological but he doesn't want to admit it

 

[rvallee]

He is still clinging on to the predictive coding model even though it doesn't work as suggested. Fnd is a learner behaviour problem according to him but as knowledge of anatomy increases many of these problems may be biological but he doesn't want to admit it

To be fair, it's a great position to fall back on. Complete black box and unfalsifiable until the inner workings of the brain are solved. They can have several more years with that scam. Kind of "software", in a way, but it would take a full working model of a human brain to know better, since it's in the functional connectivity, way more complex than an anatomical map of the connections.

It's an immoral position, but it is devilishly effective. Basically the last turtle in the turtles-all-the-way-down. It makes no sense at all, is of the "the splat on the ground is what caused the fall from high up", but that never stopped psychosomatic quackery before.

 

[NelliePledge]

Best bit about this is the second half of the title, sadly as @Andy pointed out at the start of post 1 it’s not what we would have actually hoped for.

 

[Gradzy]

Very surprising to see these statements exhibiting humility from Stone. Encouraging development.

After reading those points I can only think: how on earth has he only realised this now?

He’s been working on FND for 20 years or so hasn’t he?

These conclusions that he has supposedly finally arrived at are things that seemed entirely obvious to me as glaring weaknesses in the FND theory - and within weeks of first receiving that diagnosis!

And I’m not a career neurologist with a medical degree. In fact, did badly at school and I received no further education beyond GCSE.

What is going on with this guy, a highly educated and experienced medical professional, only just arriving at such obvious conclusions now?

What is going on in this field? I feel like I’m taking crazy pills reading this stuff.

 

[Sean]

What is going on in this field? I feel like I’m taking crazy pills reading this stuff.

I felt the same when I first started learning about the situation and history of it all more than 30 years ago, and it still feels the same today.

It is a genuinely bizarre Kafkaesque situation that such obviously poor technical and ethical standards have been allowed to become so entrenched and normalised, and so resistant to change.

There is nothing remotely sane or humane about any of this.