Review made by me and AI for public

[AR561]

Diagnostic Ambiguity and Boundary Expansion in Functional Neurological Disorder and Related Syndromes: A Patient-Informed Academic Review of Epistemic Limits, Autonomic Overlap, and Classification Drift is a produced by me and AI. I. think it is important such things are shared. I have been down with severe weakness, coordination issues, slurred speech, and more all following a severe migraine I had January 17th. For spme reason the ENT did not think it was a stroke and referred me to psychiatry for my illness burden. I see a cardiologist in a month for an autonomic workup and a neuro-opthamologist, but I am not sure what will come of it. I am diagnosed with vestibular migraine as well as MdDS. I noticed some of the doc's language was FND related and realize they are really out of their element. I hope you enjoy the review even if there are flaws.

 

[Hutan]

Thanks @AR561 and welcome to the forum. I like your avatar picture.

I am only part of the way through your article. It's an interesting read.

A framework of diagnostic humility and structured physiological evaluation is proposed to preserve both scientific integrity and patient trust.

I think that's a sentence many of us here would strongly agree with, as applying when someone has neurological symptoms but no obvious neurological lesions.

The purpose of this review is not to argue against functional neurological frameworks themselves, but to examine how diagnostic boundaries are constructed when theoretical models, heterogeneous symptom clusters, and emerging physiological findings intersect.

Specifically, this paper evaluates whether current clinical usage risks collapsing mechanistically diverse conditions into shared diagnostic categories before sufficient physiological differentiation has occurred.

Yes, an FND label would be fine if it did not carry with it unevidenced assumptions about aetiology.

The term “functional” has undergone significant semantic evolution within neurology. Historically, it served as a placeholder for symptoms without identifiable structural lesion. In the 19th and early 20th centuries, it often functioned interchangeably with “hysterical” or “psychogenic.” Contemporary usage seeks to detach the term from overtly psychiatric connotations while retaining its non-structural implication.

I see that you used 'psychiatric' there, which is a tricky word, sometimes covering neurology and sometimes psychology. 'Psychiatric' is often applied to pathologies that result in mood and personality dysfunction, and so it can cover diseases with structural evidence. I think perhaps you are meaning 'psychological' or probably more accurately 'psychosomatic' there, when suggesting that more recent use of FND has moved away from the connotations of hysteria and psychogenic illness.

Regardless of the words used, I think I disagree with you though. While 'FND' is often used due to the belief that it is more palatable to patients, the assumptions of hysteria or psychosomatic causation seem to me to remain in the form of knowing glances and nods and winks between clinicians.

Edwards et al. conducted a mixed-methods investigation examining how clinicians and patients understand the label “functional” [3]. Their work demonstrated that the term often functions pragmatically in clinical communication. It can reduce immediate defensiveness, avoid stigmatizing language, and create space for therapeutic alliance. In this sense, “functional” operates as a communicative bridge. However, the communicative function of terminology does not resolve its ontological status.

Currently, “functional” may imply:
1. Altered nervous system function without visible structural lesion.
2. Symptoms not explained by recognized neurological disease mechanisms.
3. A historical association with psychological causation or stress-related modulation.

These meanings are not equivalent. A term defined primarily by absence of structural abnormality risks functioning as a residual category. Residual categories are epistemically vulnerable because they depend on the limits of current detection methods. As detection technologies improve, residual categories often fragment.

Moreover, absence of MRI-visible pathology does not exclude:
• Microstructural connectivity changes
• Neurochemical imbalance
• Immune-mediated dysfunction
• Autonomic dysregulation
• Cerebral perfusion abnormalities
• Intracranial pressure fluctuations
• Dynamic mechanical compression

The semantic elasticity of “functional” therefore performs a dual role:
• It reduces stigma and facilitates care.
• It permits conceptual drift when boundaries are insufficiently constrained.

You say that the term 'functional' operates as a communicative bridge. I think it can do that while the patient does not realise what the term actually means to their clinicians. Once they do realise that it means that the clinician thinks the problem can be fixed by the patient thinking more correctly, the patient experience more harm than if they had understood the clinician's true thinking from the beginning. I argue that stigma is not reduced, it is simply that the patient initially has less awareness of it.

I liked your words about 'residual categories' and how they are liable to fragment as knowledge increases.

Modern FND diagnostic practice emphasizes positive clinical signs rather than diagnosis by exclusion. This shift, associated with Stone, Espay, Hallett, and colleagues, represents a significant evolution in approach [1,2]. Hoover’s sign, tremor entrainment, and variability across contexts are cited as reliable indicators of FND. These signs demonstrate that motor output may normalize under certain conditions, suggesting preserved corticospinal tract integrity.

This approach achieved several important goals:
• Reduced reliance on “normal scan” as sole justification.
• Framed FND as a neurological disorder rather than purely psychiatric.
• Provided operational criteria for research and clinical practice.

I think this is a misunderstanding. We have seen a published clinical guide that suggests that a soft toy accompanying a young person in the appointment is a positive sign that substantiates a diagnosis of FND, being a young female is a further positive sign. The absence of signs that show neural damage definitely is not taken to mean that a disorder is a neurological disorder. The opposite is in fact typically true. The irony is that, while 'Functional Neurological Disorder' has 'neurological' in the title, it is not typically seen as a neurological disorder, but rather as a psychological or psychosomatic disorder. The 'functional' in the name really serves to suggest that the person has a disorder that is functioning like a neurological disorder but is in fact not.

 

[AR561]

Thanks @AR561 and welcome to the forum. I like your avatar picture.

I am only part of the way through your article. It's an interesting read.


I think that's a sentence many of us here would strongly agree with, as applying when someone has neurological symptoms but no obvious neurological lesions.



Yes, an FND label would be fine if it did not carry with it unevidenced assumptions about aetiology.



I see that you used 'psychiatric' there, which is a tricky word, sometimes covering neurology and sometimes psychology. 'Psychiatric' is often applied to pathologies that result in mood and personality dysfunction, and so it can cover diseases with structural evidence. I think perhaps you are meaning 'psychological' or probably more accurately 'psychosomatic' there, when suggesting that more recent use of FND has moved away from the connotations of hysteria and psychogenic illness.

Regardless of the words used, I think I disagree with you though. While 'FND' is often used due to the belief that it is more palatable to patients, the assumptions of hysteria or psychosomatic causation seem to me to remain in the form of knowing glances and nods and winks between clinicians.




You say that the term 'functional' operates as a communicative bridge. I think it can do that while the patient does not realise what the term actually means to their clinicians. Once they do realise that it means that the clinician thinks the problem can be fixed by the patient thinking more correctly, the patient experience more harm than if they had understood the clinician's true thinking from the beginning. I argue that stigma is not reduced, it is simply that the patient initially has less awareness of it.

I liked your words about 'residual categories' and how they are liable to fragment as knowledge increases.



I think this is a misunderstanding. We have seen a published clinical guide that suggests that a soft toy accompanying with a young person is a positive sign that substantiates a diagnosis of FND, being a young female is a further positive sign. The absence of signs that show neural damage definitely is not taken to mean that a disorder is a neurological disorder. The opposite is in fact typically true. The irony is that, while 'Functional Neurological Disorder' has 'neurological' in the title, it is not typically seen as a neurological disorder, but rather as a psychological or psychosomatic disorder. The 'functional' in the name really serves to suggest that the person has a disorder that is functioning like a neurological disorder but is in fact not.

This is good feedback and I will edit the original as people fill in with their reasoning, as I know it is not perfect. This subject can get very messy...

 

[Hutan]

This subject can get very messy...

It certainly can. This is an area where words can be very slippery indeed.
Thanks for the constructive response.

 

[SNT Gatchaman]

For doctors, the term "functional" translates to psychological/psychosomatic (or aka "non-organic") and is the modifier then attributed to various domains. They may not specifically use these terms but the literature abounds with reference to the idea that all specialties have their version of functional disorders.

This would give, among others —

• functional neurological disorder
• functional gastrointestinal disorder (referenced as functional dyspepsia, irritable bowel syndrome, disorder of gut-brain interaction)
• functional cardiac disorder (referenced as non-cardiac chest pain)
• functional respiratory disorder
• functional pain disorder (referenced as fibromyalgia, chronic pain)
• functional gynaecological disorder (dyspareunia, vaginismus, but also spreading into clearly inflammatory conditions like endometriosis)
• functional musculoskeletal disorder (including the spectrum of ME/CFS and FM)
• functional skin disorder (referenced as functional pruritis, mucocutaneous dysaesthesia)
• functional urinary tract disorder (referenced as bladder pain syndrome or interstitial cystitis)

See eg A broader perspective: Functional symptoms beyond Neurology (2022) —

Functional (psychogenic) symptoms exist in all specialties.

 

[bicentennial]

the literature abounds with reference to the idea that all specialties have their version of functional disorders. This would give, among others —

• neurological
• gastrointestinal
• cardiac
• respiratory
• pain
• gynaecological
• musculoskeletal
• skin
• urinary tract

So it just now dawned on me these people do not want to be doctors.

 

[hotblack]

So it just now dawned on me these people do not want to be doctors.

Oh I don’t know I think they really do. What they do not want to be is people who say ‘I don’t know’ or ‘I don’t understand his’ or ‘I may be wrong’. I get the the impression they very much want to be very important doctors, consider themselves very very clever and have an answer and explanation for everything.

It likely took hold in neurology because we understand so little while other areas had a good understanding of straightforward mechanical stuff but beyond that it got messy and that’s where it takes hold now.

Sorry, maybe a bit off topic, I haven’t been through the review to comment on its contents, a bit long for me, but thanks for the contribution.

 

[Jonathan Edwards]

Hi @AR561.
I think you will find a general agreement here that 'functional' is deliberately used to convey different meanings to different people as a way of manipulating patients by doctors to give an impression of knowledge that is not there. As a doctor I would never want to use it. Quite a lot of doctors openly admit to each other that they use the term as 'doublespeak', to mean something different to patients versus other doctors. Stone and Edwards have tried to corner a market in claiming it is a legitimate way of communicating and reassuring patients but the stuff about predictive coding is not just dubious, it is self-contradictory - i.e. wrong.

I think this is an area where the use of AI runs into serious trouble because AI is not set up to include a recognition that words are being used in this bogus doublespeak way in what purports to be scientific literature.

Basically FND is a commercial product marketed by a group of loud but rather unintelligent neurologists. I would give it a wide berth.


Another thing that strikes me about AI responses is that not only do they love to be positive and answer yes to any science question you ask, they also love academic jargon - presumably being programmed to make use of it to sound convincing. In this sort of context I think it is better to use plain English.