Bearing in mind that I'm not a neurologist: The gold standard for "non-epileptic seizures" is nothing abnormal on scalp readings. But my understanding from multiple neurologists is that this gold standard can miss electrical things going on much deeper in the brain. Regarding tremors and other movement-related disorders, there is now acknowledgement from FND experts that some of these can be prodromal symptoms of Parkinson's and maybe other neurological disorders. The dispute seems to be whether they are an FND overlay (FND experts) or whether a later Parkinson's diagnosis means it was Parkinson's all along (other neurologists). In other words, per the former, the same underlying whatever is leading to both FND and then later Parkinson's, so in that case they would be independent diagnoses.
Regarding other work on the positive signs...I have pointed out that their claims of robust evidence these signs--Hoover's sign, etc--indicate FND is based on historical knowledge from neurologists that the FND experts say has been "rediscovered." But all the studies don't show much of anything. As I've reported the most robust study of Hoover's sign included less than 20 patients identified as having FND--but all had been previously diagnosed with FND based partly on a positive Hoover's sign, so the study is based on circular reasoning.
The claim that it's a brain network disease is also based on studies of associations between symptoms and functional MRIs. But every human activity will show some patterns on funtional MRIs. They're taking this association and intepreting it as causal "software" problems--even as they now acknowledge widespread structural issues as well.
And as far as I can tell, the "rule-in" signs for the emerging category of "functional cognitive disorder" are based on pretty much no data at all--just the "clinical observations" of the FND experts. There was a recent Delphi consensus paper that pretty much made this point. You use that methodology when there is basically huge uncertainty, so you collate expert opinion to come up with an uber-opinion. And if the expert opinions are from the likes of Jon Stone and Alan Carson and Michael Sharpe, it's hard to see why anyone would take it seriously.
Another thing that confuses me is that there are lots of papers saying it's challenging to distinguish FND from other clinical presentations. At the same time, they keep saying the rule-in signs are highly specific for FND. I don't see how both can be true at the same time. Either a sign is highly specific, or it's not. They also say clinicians have to make the Dx self-confidently so patietns believe it, becauae believing in it is required for treatment. But if making the distinctions is so challenging, why should clincians be so self-confident?
As we wrote in our STAT opinion piece, an FND diagnosis really seems like a way of saying, we don't know what's going on, so let's give it a name.
I simply can't believe much written by people who routinely inflate statistics, inflate claims of rule-in sign specificity, and completely misinterpret and mispresent their own research--such as the CODES study of CBT for non-epileptic seizures. In a recent paper, they blamed the funders for making them choose the primary outcome of seizure reduction--they now say that's not the best primary outcome, even though the CODES team has been hyping that as the correct primary outcome for 15 years. They're blaming funders for focusing on the primary outcome they themselves have advocated for.
These aren't honest and disinterested researchers, so everything they write seems suspect to me.
