Interoception in functional motor symptoms and functional seizures: ... evidence of intact accuracy alongside... 2023 Millman, Edwards, Chalder et al

[Andy]

Full title: Interoception in functional motor symptoms and functional seizures: Preliminary evidence of intact accuracy alongside reduced insight and altered sensibility

Highlights

• Intact interoceptive accuracy in functional motor symptoms/seizures (FMS/FS).
  
  
• Potentially reduced interoceptive insight in FMS/FS versus healthy controls (HC).
  
  
• Lower levels of “Trusting” and “Not-Distracting” in FMS/FS compared to HC.
  
  
• Elevated “Self-regulation” positively related to interoceptive confidence in FMS/FS.
  
  
• Elevated symptom severity/impact negatively related to interoceptive confidence.

Abstract

Altered interoception may be a pathophysiological mechanism in functional neurological disorder (FND). However, findings have been inconsistent across interoceptive dimensions in FND including functional motor symptoms (FMS) and seizures (FS).

Here, individuals with FMS/FS (n = 17) and healthy controls (HC, n = 17) completed measures of interoceptive accuracy and insight (adapted heartbeat tracking task [HTT] with confidence ratings), a time estimation control task (TET) and the Multidimensional Assessment of Interoceptive Awareness–2 (MAIA-2) to assess interoceptive sensibility. The groups did not differ in interoceptive accuracy (p = 1.00, g = 0.00) or confidence (p = .99, g = 0.004), although the FMS/FS group displayed lower scores on the “Not-Distracting” (p < .001, g = 1.42) and “Trusting” (p = .005, g = 1.17) MAIA-2 subscales, relative to HCs. The groups did not differ in TET performance (p = .82, g = 0.08). There was a positive relationship between HTT accuracy and confidence (insight) in HCs (r = .61, p = .016) but not in FMS/FS (r = 0.11, p = .69). HTT confidence was positively correlated with MAIA-2 “Self-Regulation” (r = 0.77, p = .002) and negatively correlated with FND symptom severity (r = −0.84, p < .001) and impact (r = −0.86, p < .001) in FMS/FS.

Impaired interoceptive accuracy may not be a core feature in FMS/FS, but reduced insight and altered sensibility may be relevant. Reduced certainty in self-evaluations of bodily experiences may contribute to the pathogenesis of FND symptoms.

L. S. Merritt Millman, Eleanor Short, Stanton, Winston, Nicholson, Mehta, Reinders, Mark Edwards, Goldstein, Anthony David, Matthew Hoptopf, Trudie Chalder, Susannah Pick

Open access, https://www.sciencedirect.com/science/article/pii/S0005796723001274

 

[Hutan]

I've never understood the premise of being aware of heart beats. The BPS people seem to think that being aware of your heart beats is a good thing, an example of interception, at the same time as saying that people with FND are pathologically aware of bodily sensations and are too self-focussed. As far as I can see, it's entirely normal to not be aware of your own heart beat most of the time - there are other more important things to think about. Yes, when you are excising heavily you can hear your pulse pounding. Or when you have an infection and it throbs. Or when you have palpitations.

Interoceptive accuracy: Correct and precise monitoring of changes in internal bodily states. E.g., degree of accuracy on performance in heartbeat detection tasks.

It looks like the BPS people have been so convinced of their theory that lots of studies have been done on it, with results all over the place.

I found this attempt to explain the variability hilarious:

The discrepancies in results could be due to inconsistent measurement of interoceptive dimensions and variable control of known confounds of the HTT (Murphy et al., 2018; Palmer, Ainley, & Tsakiris, 2019; Ring & Brener, 1996) including body mass index (BMI), knowledge of own heart rate, and time estimation abilities, as well as an overwhelming focus on interoceptive accuracy, with measures of interoceptive insight or sensibility less commonly included. The use of standard HTT instructions alongside pulse oximeters or worn sensors that may facilitate task performance (Murphy et al., 2019) may also account for some discrepancies.

Yes, I guess people who have their heart rate showing on their Apple Watch probably are a bit better at estimating their heart rate than people who just take a guess. And some of the studies seem to have relied on people just knowing what their usual heart rate is when they are sitting or whatever.

I haven't read the whole paper, but from the abstract, it looks like this is an admission of defeat, i.e. that the inability to accurately estimate your heart beat is not a feature of FND. And so they are moving on to other possible flaws that might give them a way to diagnose FND, and so prove that it is a real thing.

Maybe I am missing something? It just all seems laughable.