Review Long COVID Is Not a Functional Neurologic Disorder 2024 Davenport, Tyson et al

Apologies this is a bit of a ramble and may not make sense or be particularly relevant or useful. I'm just posting it because I've written it. I've put most of it in a spoiler so as not to clutter up the thread discussion.

I've decided to take a more thorough look at the historical and definitional aspects of this article. I'm leaving the sections on details of biomedical evidence to others to comment on as I don't feel qualified to judge the soundess or otherwise of the details.

Spoiler: Neurasthenia as the precursor of ME/CFS and FND

Starting with this paragraph:

This part is just plain wrong in my opinion:

Definitions of neurasthenia and ME/CFS are based on descriptions of symptoms, not on causes.
For example:

This describes a pattern of symptoms that could well lead to the people diagnosed with neurasthenia in the 19th century being diagnosed with ME/CFS today. Equally it could lead to some being diagnosed with burnout, stress related fatigue and all sorts of other fatiguing illnesses that do have clear pathology such as MS.

There is a clear path from neurasthenia to current BPS models of ME/CFS, and has been since the 1980's and probably earlier.
For example, 34 years ago:
Old wine in new bottles: neurasthenia and 'ME' S Wessely

. . . the true successor to neurasthenia only appeared in the 1980s, with the arrival of chronic fatigue syndrome (CFS).
Wessely S. Neurasthenia and chronic fatigue syndrome: theory and practice. Transcultural Psychiatric Review 1994;31:173-209.

I have a particular fascination with the history of neurasthenia, which I think is now accepted as the precursor of CFS/ME. The parallels between neurasthenia and CFS are many and inescapable.
Wessely S. “To tell or not to tell”: The problem of medically unexplained symptoms. In ; Ethical Dilemmas in Neurology (eds Zeman & Emanuel), WB Saunders, 1999, 41-53

Wessely also equates CFS with burnout:

If the work-relatedness was left out of the equation then burnout would indeed equate to CFS or fatigue, not least given the 96% overlap between CFS and neurasthenia, for example, reported from one CFS clinic.
Leone S, Wessely S, Huibers M, Knottnerus J, Kant U. Two sides of the same coin? On the history and phenonomology of burnout. Psychology & Health 2011: 26: 449-464.

And Michael Sharpe in 2010

I think the Oxford criteria (Sharpe 1991), the clear history of equating ME and/or CFS with Neurasthenia, and its psychosomatic attibution is an essential part of the history of ME/CFS.

I think it's also notable that the Oxford criteria, with its requirement only for chronic disabling fatigue, is an even broader umbrella than neurasthenia which required at least 2 other symptoms and which explicitly excluded 'the presence of mood, panic, or generalized anxiety disorders'. The Oxford paper specifically includes these mental disorders, and only excludes major psychiatric disorders such as schizophrenia.

I think by muddling together causes and symptoms this section confuses rather than enlightens.

As far as I can see, neurasthenia is a symptom description, not an attribution of aetiology.

Getting back to the article in this thread, the introduction ends:

I don't feel qualified to comment on the FND history of association with neurasthenia, nor with its psychosomatic attibution, but it seems to me that ME/CFS and FND have followed very similar paths of a set of symptoms, largely focused on fatigue in ME/CFS and on neurological signs and sympoms in FND, and with some links back to the set of symptoms described in neurasthenia, have been developed along two paths, but not split in the way the authors of this paper describe.

Rather than the split being, as they suggest, between ME/CFS = biomedical path, FND = psychosomatic path.

This is my understanding of the split:

Biomedical scientists and some clinicians: ME/CFS and unexplained neurological signs/symptoms = biomedical but biology not yet fully elucidated, diagnostic criteria for both overlap with those for neurasthenia

BPS proponents, mostly psychiatrists and neurologists: ME/CFS and FND are psychosomatic and the successors of neurasthenia/conversion disorder/hysteria.

 

More ramblings, this time on PEM.

Quoting from the article:

That attempt to describe PEM as a host of symtoms following exertion, and PEM being 'responsible for episodic disability' seems unhelpful to me. It both confuses cause and effect, and conflates 'symptoms after exertion' ie fatiguability' with delayed PEM which is both an increase in already existing symtoms and some new ones, and decreased ability to function for days or longer.

PEM is not the cause of eplsodic disability, one of its features is increased disability. The idea of it cycling seems to suggest a pattern of cycles of health and relapse, or ability and disability. And whether it 'cycles' or the pattern is continuous rolling PEM or rare PEM may depend on disease severity and life circumstances allowing adequate pacing (and luck).

The symptoms listed and many more are features of ME/CFS, not solely of PEM. The existence of these symptoms is not a sign the person is in PEM, it's a sign they have ME/CFS. Most of us have symptoms and disability all the time, we don't have cycles of disability.

This reminds me of the problems with Sarah Tyson's questionnaire PASS that purported to be about PEM but was about symptoms after exertion, muddling together PEM with fatiguablity.

Why not differentiate muscle fatiguability from PEM and use a clear definition of PEM that incorporates exertion above the person's current limited capacity, delay of a day or two in onset of PEM, significant increase in ME/CFS symptoms, additional symptoms, significantly decreased ability to function and duration exceeding a day, often much longer.

I think the attempt to conflate Ramsay's description of muscle fatiguablity with PEM is unhelpful.

I haven't come across the microcycling and macrocycling idea for PEM, has anyone else? It doesn't seem particularly helpful to me. Do they mean microcycling is short term fatigablity and macrocycling is PEM?

 

More ramblings, this time mostly on FND, and comparisons with criteria and aetiological models of FND and ME/CFS

Spoiler: more blah blah

Reading the section on FND, there seem to be two possibly contradictory definitions given in the article:

The first specifies it's a mental health condition, says it's a synonym for conversion disorder, and and focuses on mental processes, the second specifies it as unexplained and defined by symptoms.

So which one of these are the authors arguing is LC is not? The mental illness or the set of neurological symptoms?
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The thing that strikes me most about this section is you could substitute ME/CFS for FND in that description and you would get the BPS approach to ME/CFS as inflicted on us for over 3 decades. Far from sailing merrily along the biomedical route with lots of research to support it, we have been, and largely still are, stuck in the same place as FND.

ME/CFS and FND both have diagnostic criteria based on descriptions of symptoms, ME/CFS and FND both have limited and often poor quality biomedical research and no clearly established biological aetiology, ME/CFS and FND both have powerful medical proponents of psychosomatic aetological models, and pwME and pwFND are both subjected to largely ineffective psychobehavioural treatments.

So in arguing that LC is sometimes ME/CFS, but is never FND, which definitions or aetiology are the authors objecting to? The diagnostic criteria based on symptoms, the different models of aetiology for each?

I guess I have to read on to find out.

 

I don't know why I'm ploughing on with this. I have no idea whether this is helpful. Perhaps I want to try to contribute to making subsequent papers from this group more useful. There is clearly a need for something to stop pwLC being wrongly diagnosed as having FND when they don't and as being assumed to be psychosomatic, and I commend the effort.

I guess that depends how the clinician explains it. If they use the symptom based definition and explain the cause is unknown and they get some help with coping with the symptoms, why not accept it if you find it helps to have a name to attach to your symptoms. I can't imagine being happy with the label if I'm given the mental health explanation and am told the old name was hysteria and the bizarre Freudian conversion disorder explanations.

I have underlined 'and pathophysiology' because it's wrong. Again they are muddling together symptoms and aetiology unhelpfully. As far as I know, none of the diagnostic criteria for ME/CFS say anything about pathophysiology, nor should they, since it's not established.

Is it true that medical organisations conflate ME/CFS and FND on the basis of symptoms. Or is it on the basis of assumed psychosomatic cause? Just asking, I don't know.

 

That all seems pretty sensible to me. In fact, why not stop there, it's all that needs to be said.
Edit: They probably should add that currently unexplained or functional does not mean psychosomatic, it simply means the physiological explanation has not yet been found.

You'll be pleased to here I'm stopping there. I've run out of energy, and it's nice to end on a positive note.

 

But I reckon even that paragraph is full of problems.

FND is not when the medical and neurologic symptoms fail to match existing medical or neurological conditions. It is when doctors believe that the symptoms don't match existing conditions or other physical conditions that may be identified in the future. The symptoms may in fact match, and the problem is in the doctors' inadequate knowledge or the technology they have. And FND involves a belief on the part of the doctor that the reported problems could be overcome by the patient thinking better.

We don't know how many people have it, or indeed if any do. It is nonsense to present prevalence figures as if they are facts.

That isn't true and seems to be a fundamental misunderstanding on the part of the authors. FND is not just seizures and abnormal movements and weakness - it can include cognitive dysfunction, ME/CFS and fibromyalgia and headaches and persistent coughs. The broader functional spectrum includes all sorts of thing such as IBS, incontinence - anything where the doctor feels that there is no physical reason for the symptoms. @sarahtyson - you need to understand that ME/CFS is very much seen as an FND, and, at present, there are pretty much only beliefs and some still only promising indications from research that differentiate the two. If you have ME/CFS, then the psychosomatic proponents believe that you have an FND.

But which bit of Long Covid shouldn't be regarded as FND? The fatigue, the intermittent muscle weakness, the brain fog - most of the core symptoms are in fact entirely compatible with the BPS view of functional disorders.

 

Thanks for providing a different perspective, @Hutan. I think part of the difference of opinion is because we are talking at cross purposes. It depends a lot on which definition of FND you are talking about, the narrow range of neurological symptoms of unexplained aetiology, as in the diagnostic criteria in Box 1, or the ICD definition that calls it a mental health disorder. I read this paragraph as referring to the diagnostic criteria based on symptoms and unknown aetiology.

I liked the paragraph I quoted because it said clearly that FND should only be applied to a very limited range of symptoms, with a couple of examples given. I don't think the paragraph says anything about aetiology, only that the symptoms don't fit a recognised neurological disease and it's rare. I have no idea what the source of the numbers is, so I can't comment on that.

It then goes on to say that some people with other conditions may also have FND in this narrow sense. I took that to mean it was referring to comorbid conditions. It's possible that it could happen at the same time as ME/CFS and any other symptosm all in the same person. It's saying the FND bit should be restricted to the specific symptoms, and not assumed to subsume the rest of the pwLC's symptoms, and also lists a whole lot of other conditions which have been misdiagnosed as FND and argues against that. Surely that's helpful.

I knew I should steer clear of discussing anything to do with FND. I simply don't know enough about it.

 

The first sentence of the paragraph cites the DSM5-TR. That is the Diagnostic and Statistical Manual of Mental Disorders. In that manual, Functional Neurological Disorder has 'Conversion Disorder' in brackets after it. The list of diagnostic criteria in Box 1 is cited as also being from the DSM. So, the contents of Box 1 and the DSM definition that calls it a mental health disorder are all one and the same. They aren't two different conceptions of FND.

You might think that Box 1 refers to a narrow range of neurological symptoms. It often does not.

It can be and often is interpreted as covering a very broad range of symptoms. Sensory function is taken to include cognitive function and that is taken to include brain fog, fatigue and tiredness.

ME/CFS is a group of symptoms that has been given a name. A diagnosis of ME/CFS is not protection against a diagnosis of FND by those who see ME/CFS as a subset of FND.

We might prefer FND to only be applied to a very limited range of presentations requiring non-epileptic seizures and/or a funny walk, but it usually isn't. You don't have to have seizures or gait issues to be given an FND label. Someone with ME/CFS compliant symptoms and no seizures or limb paralysis easily qualifies for an FND diagnosis.

 

Or to accept.

We are also having to fight with one hand behind our back, in that the standard biomedical arguments have meet to be accepted are much higher than those for psychosomatic arguments. It should not be that way, but in practice it is.

That puts you on the same level of knowledge as the entire FND movement.

 

Thanks @Hutan, I stand corrected. I knew I shouldn't try to discuss FND. I have previously steered clear of the FND sections of the forum most of the time as I have no experience or expert knowledge of things like movement disorders or non epileptic seizures and don't feel qualified to comment about other people's experience of them or the appropriateness or otherwise of collecting them under an FND label.

I was trying to make the point that if FND were restricted to a narrow set of very specific rare unexplained symptoms that would prevent pwME and pwLC being wrongly diagnosed with FND unless they have those symptoms as a separate comorbidity.

At least we can agree that nobody with ME/CFS or LC should be diagnosed with FND on the basis of brain fog, muscle weakness which are part of ME/CFS. I think that's the point of this article. FND should not be used as an alternative diagnosis for LC.
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I would find an article on this subject more helpful if it took ME/CFS and and FND in turn and laid out clearly the diagnostic criteria based on symptoms for each, then explained clearly the different approaches to aetiology for each with enough history to show how those causal models arose and the evidence, or rather lack of evidence for each. There would also need to be a clear explanation about the term 'functional' and how it's misused to interpret currently unexplained symptoms as psychosomatic.

Then bring in LC and explain its an umbrella term for all post covid symptoms, list the main subcategories such as damaged organs and ME/CFS,
then finally conclude that FND is not a relevant or appropriate label for ME/CFS or LC.

 

Can someone help me out of my confusion about FND?

We have seen and apparently supported David Tuller spending a lot of effort getting people publishing papers that quote higher prevalence for FND and giving alternative lower figures, so does that mean we accept that some people have a condition accurately called FND? Or should David Tuller instead have been pointing to evidence that FND is not a thing at all?

Why is it OK to refer to functional movement disorders, and functional seizures, but not to use an umbrella term like FND as an overarching diagnostic category?

What arguments does anyone think should be used to justify the heading of this article, LC is not FND?

• FND doesn't exist, so no one should be diagnosed with it?
• FND is a rare neurological set of conditions that aren't seen in LC apart from rare comorbidity?
• FND is a disguised version of psychosomatic so does not apply to LC because...?
• FND and LC have different symptoms?
• Or what?