Functional dystonia: A case‐control study and risk prediction algorithm, 2021, Stephen, Perez et al

Abstract
Objective
Functional dystonia (FD) is a disabling and diagnostically challenging functional movement disorder (FMD). We sought to identify historical predictors of FD vs. other primary dystonias (ODs) and develop a practical prediction algorithm to guide neurologists.

Methods
1475 consecutive new patient medical records were reviewed at an adult/pediatric tertiary‐referral dystonia clinic from 2005 to 2017. Ninety‐nine met criteria for clinically established FD (85 adults and 14 pediatric), paired with 99 age/dystonia distribution‐matched OD. Univariate and multivariate regression analyses were performed to identify predictors of FD and disability. We formed a prediction algorithm, assessed using the area under the receiver operating curve (AUC).

Results
Multivariate logistic regression analysis investigating independent predictors of FD (P < 0.001) followed by development of a prediction algorithm showed that the most robust predictors included abrupt onset, spontaneous resolution/recurrence, pain, cognitive complaints, being on or pursuing disability, lifetime mood/anxiety disorder, comorbid functional somatic disorders, and having ≥3 medication allergies. The prediction algorithm had utility for both adult and pediatric FD, with excellent sensitivity/specificity (89%/92%) and an area under the curve (AUC) 0.95 (0.92‐0.98). Greater disability (modified Rankin Scale) independently correlated with a number of functional examination features, unemployment/not attending school, number of medication allergies, and younger age of presentation. FD patients were high health‐care utilizers and were more frequently prescribed opiates/opioids and benzodiazepines (P < 0.003).

Interpretation
This case‐control study provides an algorithm to guide clinicians in gauging their index of suspicion for a FD, with diagnostic confirmation subsequently informed by neurological examination. While this algorithm requires prospective validation, health‐care utilization data underscore the importance and need for more research in FD.

Open access, https://onlinelibrary.wiley.com/doi/10.1002/acn3.51307


"FD had higher rates of functional somatic disorders (FSDs) (fibromyalgia, CRPS type 1, irritable bowel syndrome [IBS], chronic fatigue syndrome etc.) 28.3% vs. 3.0% (P < 0.0001) and in children, FSDs were solely present in FD (21.4%) and absent in OD. IBS and fibromyalgia were most highly associated with FD. Autonomic symptoms were prevalent in FD, including gastroparesis (10.1%), sometimes requiring gastrostomy tube placement, and postural orthostatic tachycardia syndrome (POTS) (7.1%), which were present only in FD and frequently occurred together."

 

They do not give any description of how functional dystonias differ from other dystonias beyond their own decision to class certain aspects of dystonia as functional.

They decide that sudden onset fixed dystonia means it is functional because other dystonias do not have this but this just means they do not accept that type of dystonia as organic. Completely circular!

They say one of the features of functional dystonia is more pain then say one of the ways to diagnose it is higher opioid use. How can anyone take this sort of thing seriously?

Maybe the answer lies here

They have a type of dystonia that causes them to need medical treatment so the answer is to not treat them any more. Instead they are subtly abused by the implication they are drug addicted scroungers not that they need more painkillers because of pain and can't work because of severe disease. Let's not allow people to feel compassion for them.

 

It sounds to me like they are disabled by their ME/CFS, fibromyalgia and other primary problems. The dystonia is just what landed them in a neurology office, probably because the GP was impressed by it.

 

The term "primary symptom of" appears to be mostly "which symptom has been the focus of one particular physician at the expense of other symptoms". This thing where a "primary symptom" is required is seriously problematic with multi-system disorders. You read those papers focusing on one symptom and there is always this hand-wavy mention of a bunch of other symptoms that are simply not considered.

I have no idea how anyone expects this to work at all. So bizarre, especially when translated into other common contexts like a mechanic demanding what ONE thing should be fixed on a car that is borderline totalled. Sometimes simplifying things actually makes seem far more difficult than they really are.

 

Exactly. Was the dystonia REALLY the presenting complaint in these patients? Or was it one of myriad symptoms they have but since it looks “objective” (unlike something not readily observable like fatigue and pain), the doctor latched onto it.

I am noticing a huge swell of diagnosis of FND on social media. This is anecdotal but it seems to me they have realised they have lost on the PACE front so they are simply moving to a different battlefield. I’m seeing new people with ME/CFS, POTS, gastroparesis, fibro etc. being given other diagnoses like FND, MUS, pervasive refusal syndrome etc so they can push people into rehabilitation programmes.

 

After 20 years of invisible illness I developed neurological symptoms that were embarrassingly obvious. At last, I thought I would be taken seriously. Sadly it was a devastating experience where all my realities were denied.