FND: Philosophy Masquerading as Diagnosis - Part 1

28 Jul 2025 Christoff Truter Spousal caregiver

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In an article published in the Journal of Neurology on 21 May 2019 (Vol 266, Issue 8, pp. 2018-2026), DOI 10.1007/s00415-019-09356-3, titled "The misdiagnosis of functional disorders as other neurological conditions": Source link

The authors explored the converse scenario (to this website), investigating FND cases that were originally attributed to other diagnoses.

There tends to be more concern about "missing" an "organic" disease when diagnosing functional disorders, rather than the other way around, probably related to a perception, incorrect in our view, that neurological diseases are always more serious than functional disorders.

There are obvious and serious implications of missing an "organic" diagnosis, but the harms of missing a functional disorder should not be underestimated in relation to unnecessary treatment, delay in treating the underlying functional disorder, and psychological harm as a direct result of the misdiagnosis.

Yes, absolutely. Misdiagnosis, in any direction, is detrimental to receiving proper treatment.

However, I am extremely concerned about how as a matter of fact the term FND is being used here.

With no biomarkers, a reliance on subjective indicators such as Hoover’s sign, and non-specific brain changes on fMRI that occur in many other conditions, along with a broad symptom spectrum often accompanied by comorbidities, the diagnosis of FND appears to be more of a conceptual label rather than a data-driven disease.

It is a disorder that was conceptually defined into existence, unlike diseases discovered through measurable physiology. The very idea that the expression of a symptom that cannot be explained somehow correlates to a "brain software" problem is speculative and should be treated as such. Let's be blunt, FND is a matter of philosophy, not fact; repeating the functional mantra a thousand times when patients request a deeper look will not change that fact.

FND is not a rule-in diagnosis as suggested, but rather a buy-in diagnosis.

It seems there is an inherent problem where many medical professionals are not able or willing to remain agnostic about uncertainty.

The danger is that this approach treads dangerously close to being religious in nature; even the DSM-5 narrative echoes the sentiment of faith healers.

Short duration of symptoms and agreement with the diagnosis are positive prognostic factors.

Functional Neurological Symptom Disorder (Conversion Disorder) Section: Diagnostic Features / Associated Features Supporting Diagnosis - Prognosis

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Wow, okay… I can agree that using FND as a construct (e.g., we have reached a diagnostic impasse, so multiple disciplines are now involved) can be beneficial (even more beneficial if we consider, when appropriate, ophthalmologists, otologists etc), but accepting the diagnosis should be irrelevant to treatment outcome.

That said, when you dig into neurological conditions, you quickly realise how obscenely complex they are. We are dealing with multiple illnesses that present in very similar ways (strange that doctors are not more careful given that consideration). In this picture, FND is the motherlode, a disorder that can mimic anything and everything neurological. That should be a red flag for anyone; it becomes an omnipotent disorder, literally a diagnosis of the gaps.

We are most likely dealing with underlying conditions that are extremely subtle and difficult to detect, disorders that exist on the fringes of our current technology and understanding. Investigators, therefore, need to be pedantic and meticulous. For example, in my wife's case, very early on, when symptoms began to escalate, she had a clear vestibular issue, they were too distracted by how the CNS was reacting. Yet nobody at the time dug deeper into that detail we clearly communicated, and investigating it years later only makes it more challenging.

And, as suggested in another post, conditions that present with neurological symptoms are not always neurological in origin, so throwing in the functional towel would be ill-advised.

Even something like facial asymmetry is often assumed to be functional in nature. In my wife's case, we can clearly demonstrate that it is mechanical (no need to resort to esoteric diagnostic criteria), possibly neurovascular. I will elaborate on this in a future post.

At the end of the day, we are content to accept the unknowns — that honesty keeps the door open to possible answers in the future, answers that can be scrutinised, measured, and weighed appropriately.

Be sure to check out part 2.