Trial By Error: Can Functional Neurological Disorder Be an Indication of Prion Disease?

By David Tuller, DrPH

A recent article in the Journal of Neurology presents a twist on the issue of functional neurological disorder (FND). The article, which was published in September, is called “Functional neurological symptoms as initial presentation of Creutzfeldt‐Jakob disease: case series.” Creutzfeldt-Jakob disease is a prion disorder that leads to dementia and death, usually within months.

But first, some background.

FND is a clinical entity with “rule-in” signs that are designed to distinguish it from recognized or standard neurological disease, according to the Diagnostic and Statistical Manual of Mental Disorders. Formerly, FND was commonly known as conversion disorder. Before that, hysteria.

Once a neurologist has rendered a diagnosis of FND based on these rule-in signs, further testing to identify hidden pathophysiological dysfunctions is considered inappropriate. The FND diagnosis itself is the explanation—even if the proposed mechanisms remain poorly understood. The literature is clear: FND is not intended as a place-holder or provisional diagnosis to be used while doctors search for a better explanation for a patient’s symptoms.  

Some confusion about the construct is apparent from the differing prevalence rates routinely highlighted by leading FND experts. As I’ve previously documented, these experts have cited the prevalence of the condition among neurology clinic attendees as being 6%, 16% and 31%–with all three rates being drawn from the same study of Scottish neurology clinics.

Only the lowest prevalence rate—6%–is based on rule-in diagnoses, according to an authoritative 2016 paper. However, FND experts have generally preferred to cite the prevalence rate of 16%, which allows them to refer to the condition as the second-most common presentation, after headache.

But this 16% figure is inflated. It includes many patients identified in the Scottish study as having “psychological” problems but apparently without the rule-in signs required for an FND diagnosis. FND experts have perpetuated this confusion rather than demonstrating any inclination to clear it up. Perhaps they believe that promoting pumped-up prevalence rates is an effective way of drawing attention to the issue.

Misdiagnoses of patients as having FND when they actually have known neurological disorders are said to be rare. But whether they’re rare or not, they can be disastrous when they occur. (The counter-argument is that that misdiagnosing someone as having a known neurological disease when they actually have FND can also cause harm.)

Last May, an Irish court ordered a hospital to pay a young man six million euros for having failed to diagnose a brain tumor, an error that delayed necessary surgery by months. Doctors had misdiagnosed his headaches, concentration problems and hand numbness as “psychological and functional” and referred him to “the mental health services and physiotherapy,” according to The Irish Independent.

Physicians can be quick to default to psychological explanations when they don’t understand what is causing a patient’s problems, noted Brian Hughes, a psychology professor at University of Ireland Galway, in a blog post about the case. “It would be nice if the doctors concerned could perhaps try to be a little less hasty, and a bit more humble,” he wrote.


Prion diseases masquerading as FNDs

The article in the Journal of Neurology is not the first report related to FNDs and prion disorders. In 2017, researchers at Rutgers University in New Jersey published an article called “A Case of Sporadic Creutzfeldt-Jakob Disease Presenting as Conversion Disorder.” According to the abstract, “The patient was a 64-year-old woman with no prior psychiatric history who was initially diagnosed with conversion disorder and unspecified anxiety disorder but soon thereafter was discovered to have Creutzfeldt-Jakob disease.

In 2019, BMJ Case Reports published an article called Gerstmann-Sträussler-Scheinker syndrome misdiagnosed as conversion disorder.” Gerstmann-Sträussler-Scheinker syndrome is a genetic prion disorder. Here’s part of the abstract:

We present a 40-year-old man without relevant medical or family history who developed progressive neurocognitive and behavioural symptoms over 3 years. Initial extensive diagnostic workup of his variable motor symptoms was unrevealing and he was diagnosed with conversion disorder. This diagnosis persisted for over 2 years, despite progressive neurocognitive symptoms. He eventually developed dementia and severe neurological impairment.

And from the text:

“The diagnosis of a psychogenic disorder was seemingly substantiated at a subsequent hospital admission for falls, when inpatient video monitoring revealed inconsistencies in his neurological examination…He continued to experience progressive neurocognitive decline and presented to the emergency department repeatedly for falls due to gait disturbance. However, given his diagnosis of conversion disorder, his symptoms were interpreted as psychogenic.”

In other words, the presence in the patient’s records of a diagnosis of conversion disorder—that is, FND—meant that doctors continued to mischaracterize and misinterpret his worsening symptoms as psychogenic in nature. The patient died three years after the initial diagnosis. “In retrospect, it was likely that the variable nature of the abnormal movements was due to dystonia,” noted the article.


Were these FND diagnoses an error or correct?

Both of these individual case studies presented the FND diagnosis as an error that was later clarified. The Journal of Neurology study, from a team of Spanish researchers, frames the matter differently.

Here’s part of the abstract: “We report a clinical series of three patients who initially presented positive signs of a functional movement disorder (FMD) and were later diagnosed with a Creutzfeldt-Jakob disease (CJD). All patients presented with unilateral functional tremor, two patients also had functional limb weakness.”

(The authors parrot the party line on FND prevalence. They write that FND “represents one of the most frequent referrals to general neurology clinics” while citing the same study of Scottish clinics that has been referenced to support three different prevalence rates.)

In all three cases, the FND diagnoses were based on the presence of positive signs considered confirmatory for the condition. But it didn’t take long for these initial diagnoses to be revealed as insufficient. “Later on, a rapid clinical worsening occurred, and patients developed clear parietal and cerebellar signs that prompted the diagnosis of a prion disease,” the authors write. All three patients died within months.

Yet they do not suggest that the FND diagnosis was wrong or inaccurate. On the contrary, they seem to view the FND as part of the ongoing prion disease process or pathway. The full clinical picture, they write, “suggests that perhaps early prion-mediated neuronal loss might result in the involvement of brain circuits that are implicated in the FND genesis…Diagnosis of FND should not become immutable and an adequate neurological follow-up is, therefore, crucial.”

In other words, the authors are suggesting that the rule-in signs used to confirm an FND diagnosis cannot easily distinguish between an FND diagnosis that is a precursor of a prion disease and an FND diagnosis that is not a precursor of a prion disease. Therefore, they argue, the diagnosis should be provisional and not “immutable.”

(The authors’ efforts to communicate the meaning of their findings is marred by a sentence in the abstract that seems to have parts missing: “A positive diagnosis of FND is essential as it is an adequate examination and a close follow-up of these patients in neurology clinics.”

What does that linguistically and grammatically challenged sentence mean? Free subscription to Virology Blog for the best interpretation!!)

The authors contextualize their findings with a discussion of the literature about FNDs as co-morbidities in the presence of Parkinson’s and other known neurological conditions. At the same time as they present the FND diagnosis as a kind of place-holder pending further developments, they also seem to indicate that it exists as an entity independently of the prion disease. Here’s what they write:

“We propose that initial precipitants such as mood disorders that can be present at the onset of prion diseases (Patient 2) or minor trauma (Patient 3) associated with subtle sensory abnormalities in our patients might have driven increased attention to self-movements and facilitate a conscious motor processing. This, along with parietal dysfunction in our patients, may have facilitated the genesis of the FND.”

I find this kind of confusing—especially because the first sentence in the above paragraph, like the sentence in the abstract, is somewhat challenging to untangle. (Note to researchers: Please copy-edit your articles before they appear!!)

The explanation seems to be that early markers or indications of the prion disease led patients to engage in heightened monitoring of their symptoms—one of the prominent factors said to be involved in generating FND. And that these patients, therefore, actually suffered from FND as well as their prion disorder. So FND was the right diagnosis after all.

At least, I think that’s what they’re saying. But I could be wrong.

What would leading FND experts make of this article, I wonder? Would they consider these FND diagnoses to be misdiagnoses, or diagnoses that were properly made at the time? And do they have suggestions for how neurologists can distinguish FND from early signs of prion disease other than waiting for patients to get worse and die?

8 thoughts on “Trial By Error: Can Functional Neurological Disorder Be an Indication of Prion Disease?”

  1. Explanations are always made more difficult when trying to explain the unexplainable or excuse the inexcusable.

  2. Fantastic! Thanks so much for this David, it really shows how these people seem to tie themselves up in knots when they venture into FND territory. Let’s not doubt FND, just explain all these problems away some other way, oh, and try to find a way to blame the patient if we can, or rather I mean – put it down to ‘mental health’ issues. (I know I really shouldn’t use the word ‘blame’ lest people could think that I stigmatize mental health problems, which couldn’t be further from the truth, when they actually exist).

    “But this 16% figure is inflated. It includes many patients identified in the Scottish study as having “psychological” problems but apparently without the rule-in signs required for an FND diagnosis.”

    We mustn’t forget that that figure included excess drinking/alcohol so with the festive season upon us do go careful peeps and try to avoid that FND diagnosis too.

    “Perhaps they believe that promoting pumped-up prevalence rates is an effective way of drawing attention to the issue.”

    Not only drawing attention to the issue – I suspect that securing service and research funding may have something to do with it? I mean, if they made out to research funding bodies that FND prevalence was only 6% then would be as likely to secure research funding as supplying a 16% prevalence rate? And with respect to services, if service providers are told that FND’s the second most common neurological presentation, or even comprise up to a third of neurology referrals, isn’t that more likely to get them to sit up and take notice and direct funding towards FND services, rather than saying that FND affects only about 1 in 16? (see - and - and - . Just saying.

    “Misdiagnoses of patients as having FND when they actually have known neurological disorders are said to be rare. ”

    Yes, they are (said to be), but:
    1) if the misdiagnosis rate is based on positively identified FND or “conversion disorder” then it shouldn’t be extended to those of the 16% or 30% that haven’t been positively identified. (see -
    2) if the misdiagnosis rate isn’t that safe, if your confidence in it is limited, then it surely shouldn’t be relied upon - (see second paragraph?
    3) if the time interval for follow up of cases is too short, then the misdiagnosis rate may well be unreliable - see 2nd paragraph.

    Here’s something for the festive season from 5 years ago - – it’s one of my favourites too, ENJOY!

  3. The J of N shows its cult member status right from the choice of title for its article:
    “Functional neurological symptoms as initial presentation of Creutzfeldt‐Jakob disease: case series.”

    The correct title would be: ‘Creutzfelt-Jakob disease symptoms and signs disregarded due to consultant preference for psychologising rather than admitting they do not possess tools to effectively diagnose anything but the most obvious nerve trauma.’

    Anyone who has been through a neurological ‘work up’ has seen for themselves, the utterly primitive, diagnostic toolkit that even the leading UK specialist hospital has at its disposal. Testing a few reflexes (even if you put measurement numbers to them by running through a voltmeter and electronic timer), and sticking pins in people, is not going to pick up any cause of anything, yet this is the sort of test psychogenic ‘science’ believers use as the bedrock of their assertions on the prevalence of their made up, unfalsifiable until too late, ‘presentations’.

    I recently attended at the ‘Atonomic Unit’ of the top UK neurological hospital, where I had hoped that I would, at long, long, last be able to talk to people at the leading edge of neurological research. When I started asking what they were going to do to get to the bottom of my peripheral system signs and symptoms, I was, rather apologetically informed, that the department name was a bit misleading, as they really only do blood pressure measurements in different orientations and under varying stressors. Even more disappointing, was when I asked if they had tests to find out the actual cause of the blood pressure failings of any particular patient, and was, rather glumly, told that, most of the time, they really don’t find out the cause.

    This was my experience on meeting a genuinely helpful and sympathetic researcher who knew the current limitations of what is availible to UK hospital based neurologists: Now imagine what happens when a CBT/FND/MUS zealot with a cure for everything, gets behind the controls…

    Unfortunate doomed patients are callously put through extreme extra mental stress on top of their already distressing illnesses, by CBT zealots with only cure all quackery to offer as help, while they prevent their victims from seeing proper researchers and getting the right diagnosis before it’s too late.

    Far too many decades ago, my fate was sealed by a 5 minute visit from the leading psychiatrist of the local hospital. On hearing I was to be honoured by this visit, I took care to have notes ready so as not to waste time and miss key points. Instead of listening to me, this eminent individual took the very existence of a notebook as sufficient evidence to write ‘hypochondria’ in the report of his flying visit where no tests or proper interview were carried out.

    His one word had the power to consign me to a fate almost worse than death itself. A psychiatrist’s power to destroy people is almost god like. Hardly anyone ever believed anything I said about my health ever again. It destroyed relationships and almost broke up families: I didn’t find a local doctor willing to help me for over three decades, and most treated me with utter contempt: on hospital visits, nurses scowled on seeing my notes, and left me to find my own way home somehow, though I was often brought in by ambulance, by worried paramedics…

    Where is the outcry on behalf of all the uncounted victims of the almost universal narcissism and assumption of infalibility that seem to be required characters for members of the psych professions? Until Dave Tuller took an interest and would not be dismissed, the media just treated patients as whipping boys and easy targets for right wing ‘would be social reformers’ complaining of ‘the work shy and the worried well’.

    The tide is turning at last.
    Happy Christmas, Dave.

  4. “A positive diagnosis of FND is essential as it is an adequate examination and a close follow-up of these patients in neurology clinics.”
    What does that linguistically and grammatically challenged sentence mean?

    If you omit the word “it” it says : A positive diagnosis of FND is essential as is an adequate examination and a close follow-up of these patients in neurology clinics.”
    This is grammatically understandable. But why the diagnosis of FND would be essential is difficult to understand. What does this add to an unbiased description of the symptoms and the admission that the doctor does not (yet) know what the cause is?

  5. Seems clear to me these people are trying to immunize themselves against accusations of malpractice when it turns out that the signs and symptoms they based their diagnosis on were actually due to an underlying illness which is not ‘functional’, and which should have been treated in ways very different from the essential non-treatment that ensues from an FND diagnosis.

    Insurance companies would be delighted if such a view were to prevail, of course, and I’m sure these researchers will experience very little difficulty in finding funding for their studies from now into an indefinite and rosy future.

  6. Maybe it’s time neurologists learned that ‘inconsistencies’ might actually be entirely ‘consistent’ with neurological disease? The fault lies entirely within their own, consistent, prejudices.

  7. Several years ago Jon Stone replied to a letter critical of a case of CJD misdiagnosed as FND as follows:

    “ It would be a shame, however, if this case conference reinforced the erroneous idea that the development of neurological disease in such cases is the norm. Failure to make a positive diagnosis of conversion disorder can have serious adverse consequences. The patient may be denied appropriate treatment management that vitally depends on persuading him or her that the symptoms are reversible and not due to disease. We should not withhold the diagnosis simply because we occasionally get it wrong.”

    Just read that last bit twice.

    I may not be an expert in FND, but I am an expert in neurodegenerative conditions and cognitive impairment. Not once in the last 10 years have I diagnosed a single patient with a functional cognitive disorder. Not. Once. There is always a plausible alternate diagnosis. I am, however, appalled at the rampant increase in FND misdiagnoses based purely on a clinician bias towards patient personalities or past histories.
    The most egregious double down is the “comorbid” FND or “functional overlay”. If their own studies report anywhere from 18-40% of PNES patients ALSO have actual epilepsy, then it seems more likely that they just have epilepsy. EEG’s do not pick up small discharges or deep or interhemispheric discharges and I have personally watched neurologists see epileptiform (eg slowing, occasional spikes and random PLEDS) discharges on EEG but make a clinical decision it did not reach significance based on their clinical judgement that the patient had FND. Then report the EEG as normal.

    For many of the patients I see who have been labelled as “functional” it is a deeply unhelpful diagnosis. Sadly, the diagnosing clinicians never get any feedback as usually the patients just quietly go elsewhere. Even should they get feedback, they cite functional overlay to pretend they were still correct, even when they’re wrong.

    Interesting too that Michael Sharp who was on the DSM 5 panel that removed the criterion that FND symptoms not be feigned wrote a chapter in “Malingering and Illness Deception” that suggested that the primary hallmark of malingering is inconsistency, which also appears to be his primary rule-in for FND.

  8. I think it’s likely that many FNDs represent attempts by the brain to preserve itself from attacks by the immune system or some external agent by shutting down the parts that are under attack.

    In the case of the somnambulant ‘sleepers’ of Oliver Sacks’ Awakenings, for example, Sacks was able to wake them up with injections of l-DOPA, and they resumed some semblance of normal activity.

    But these returns to normalcy lasted only a matter of weeks before the patients fell back into their previous state, from which no amount of l-DOPA could then revive them. The almost unavoidable conclusion to be drawn from this trajectory is that the brain damage which led to their illness in the first place, and which was vastly slowed during their ‘sleep’, progressed rapidly to an end state once they were awakened.

    If that’s usual with FNDs, “appropriate treatment management that vitally depends on persuading him or her that the symptoms are reversible and not due to disease” is actually about the worst possible treatment for FND, because insofar as it ‘succeeded’, it could and probably would put the patient beyond any hope of a cure or remission from a future medical breakthrough which identified the true underlying cause of their illness and developed a course of treatment to alleviate it.

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