Trial By Error: Questions About the Prevalence of Functional Neurological Disorder and the Research on Hoover’s Sign for Functional Leg WeaknessLeave a Comment / By David Tuller / 22 May 2023
By David Tuller, DrPH
(This is a long-ish post. Sorry! It covers two complicated issues. I want to thank an intrepid source for help with these issue.)
I have great sympathy for patients diagnosed with functional neurological disorder (FND). Their symptoms can be seriously disabling and their plight has long been neglected and dismissed by the medical establishment. When I post about FND, I like to recommend this well-written essay by a patient who goes by the moniker FNDPortal. The article provides a harrowing portrait of the experience of living with FND as well as a cogent account of the history of the construct.
I have, however, raised issues with how FND experts and investigators have made claims that do not seem to conform to the evidence cited. That includes the routine and unwarranted tripling of the reported FND prevalence rate from a 2010 study from Stone et al called “Who is referred to neurology clinics?—the diagnoses made in 3781 new patients,” published in the journal Clinical Neurology and Neurosurgery. FND, formerly called conversion disorder, was redefined in 2013 in the fifth edition of the Diagnostic and Statistical Manual (DSM-5), often referred to as the “psychiatric bible.” Among the changes in the new definition of the diagnosis was that it required the presence of a clinical sign incompatible with neurological disease.
As I’ve blogged here, here and here, Stone et al has repeatedly been referenced for the claim that FND–as re-defined in DSM-5–is the second-most common reason, after headache, for patients to see a neurologist, and/or that it has a 16% prevalence among new presentations at neurology clinics. That is simply not what the paper reported, as should be apparent to anyone reading it..............