Dr David Tuller: Does Functional Neurology Disorder Account for a Third of Outpatient Neurology Consults?


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Trial By Error: Does Functional Neurology Disorder Account for a Third of Outpatient Neurology Consults?
16 June 2022 by David Tuller

By David Tuller, DrPH

Functional neurological disorder, or FND, is the new-ish name for the hoary Freudian construct known as conversion disorder. For decades, psychiatrists informed patients that they were “converting” their emotional distress and anxieties into physical symptoms like tremors, seizures, sensory and cognitive deficits, a halting gait, or other physical dysfunctions. The impossibility of proving such claims did not seem to impact psychiatry’s acceptance of the concept or the certainty with which it was applied to patients with unexplained conditions.

Other terms that have been used to describe such symptoms are psychosomatic or psychogenic disorders, hysteria, and the like. These descriptions, which highlight the belief that the conditions are driven by psychological disturbances, have often been regarded as condescending and dismissive. More recently, however, the more neutral-sounding term “functional” has been increasingly adopted to make the diagnosis more palatable to patients, among other reasons. That makes some sense. After all, these syndromes feature deficits in function that resemble standard neurological complaints. And some or many patients who receive a diagnosis of FND, often after years of feeling belittled, overlooked or abandoned by the medical profession, might experience significant relief just from being given an actual name for what they are experiencing. I get that.

I have previously written posts questioning the term FND because it has seemed to be a so-called “wastebasket” diagnosis–just like conversion disorder. Whatever could not clearly be identified as a dysfunction explained by current pathophysiological understanding seemed at risk of being called FND, as it had previously been labeled conversion disorder.
Yet the FND experts have addressed this issue. The change in name has been accompanied as well by changes in the description of the condition in the latest version of the so-called “psychiatric bible,” the Diagnostic and Statistical Manual.

Although conversion disorder remains the heading of the category, the DSM-5, published in 2013, now includes “functional neurological symptom disorder” as a synonym. (Note: After posting this earlier, I found out that the DSM-5 last month swapped out the names, with functional neurological symptom disorder becoming the main heading and conversion disorder offered as a synonym.) According to the new criteria, identification of psychological distress, once considered to be a necessary component of conversion disorder, is no longer a requirement for diagnosis—although proponents say it can still be a factor in the genesis of the condition. (In a 2020 presentation on FND, for example, Mark Hallett from the US National Institutes of Health noted in one slide that the condition is “sometimes due in part to a psychological cause.”)

Moreover, FND experts have been advocating the notion that the condition is now a “rule-in” diagnosis based on “positive” signs—not just a dumping ground for all symptoms that don’t fit standard or recognizable neurological or pathophysiological patterns. This need for confirmatory evidence has also been incorporated into the DSM-5 description. The requirement has implications for calculating prevalence rates for FND.

In 2016, Alan Carson and Alexander Lehn, two leading FND experts from the UK and Australia, respectively, made this point explicit in the abstract of a chapter on the epidemiology of the condition:

“The recent changes in DSM-5 to a definition based on positive identification of physical symptoms which are incongruent and inconsistent with neurologic disease and the lack of need for any psychopathology represent a significant step forward in clarifying the disorder. On this basis, FND account for approximately 6% of neurology outpatient contacts.”


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It is funny that most societies decide that if anything can't be diagnosed by 'modern medicine' at that specific moment in time, then it must be psychological (which is 'modern' speak for The Gods Have Punished Thee).

Usually based on completely unverifiable theories and claims. "Ah, you have some real symptoms, but you are giving undue attention to those symptoms which then exacerbates them."

Which really is no different from, "You did not say the Maiden's Prayer with the proper devotion and the sacrifice of a goat, so now you are experiencing pain and irregularity as punishment from the wrath of the Maiden God."

Don't worry, we'll apologize in 1,200 years when we figure out what endometriosis is.

We always look at the Dark Ages with dismay, but we rarely realize that we are always living in the dark ages.