Neural basis of fatigue in post-COVID syndrome and relationships with cognitive complaints and cognition, 2024, Diez-Cirarda+

[Nightsong]

Abstract
The main objective was to evaluate structural and functional connectivity correlates of fatigue in post-COVID syndrome, and to investigate the relationships with an objective measure of mental fatigue and with subjective cognitive complaints. One-hundred and twenty-nine patients were recruited after 14.79 ± 7.17 months. Patients were evaluated with fatigue, neuropsychological, and subjective cognitive complaints assessments.

Structural and functional magnetic resonance imaging were acquired, and functional connectivity, white matter diffusivity and grey matter volume were evaluated. Fatigue was present in 86 % of patients, and was highly correlated to subjective cognitive complaints. Fatigue was associated with structural and functional connectivity mostly in frontal areas but also temporal, and cerebellar areas, showing mental fatigue different pattern of functional connectivity correlates compared to physical fatigue. White matter diffusivity correlates were similar in fatigue and subjective cognitive complaints, located in the forceps minor, anterior corona radiata and anterior cingulum.

Findings confirm that fatigue in post-COVID syndrome is related to cerebral connectivity patterns, evidencing its brain substrates. Moreover, results highlight the relationship between fatigue and subjective cognitive complaints. These findings point out the relevance of the multidisciplinary assessment of post-COVID syndrome patients with subjective cognitive complaints, in order to unravel the symptomatology beneath the patient's complaints.

Link | PDF (Open access)

 

[rvallee]

However interesting this could be from a scientific perspective, and how it's frankly unlikely to be of any relevance, I can't really much use for this kind of research focused on 'functional networks'. It's not as if this is something that is actually understood or medicine can do anything about, and the only use this ever has is to recommend the same old useless generic rehabilitation that doesn't have any relevance to the problem, as if it's a 'use it or lose it' kind of thing, which this obviously isn't.

Functional connectivity networks appears to be as much buzzword as most of the quantum healing or whatever we hear out of other forms of pseudoscience and the likes of Deepak Chopra. I could be wrong, but it's definitely part of the functional ideology and it's always ever used with some imagined effect that... doing stuff... or whatever, will change that connectivity. Or whatever. So damn wishy-washy.

Then again it could actually lead to some real understanding about the whole thing, but it doesn't fit the evidence as those 'functional networks' would have to be able to switch between a normal state and a 'disordered' state in ways that just don't have anything at all to do with the concepts of neuroplasticity this seems to be based on. If they can switch, then there's something responsible for that switch. And it obviously can't explain so many of the symptoms anyway that it would only ever be one minor part of it.

 

[SNT Gatchaman]

They seem to note correlation is not causation:

Some limitations should be considered. First, the present study presents a cross-sectional design, and longitudinal studies are needed to study whether these brain correlates are permanent or dynamic and to identify if they are part of compensatory mechanisms or part of a recovery process.

But then continue on with the idea that the fatigue is caused in the CNS, which as rvallee notes above is much more likely to be a downstream finding:

In conclusion, patients with post-COVID syndrome at 14 months from the infection presented functional connectivity and white matter associations with fatigue symptoms, mostly in frontal but also temporal and cerebellar areas. These findings suggest a role of central nervous system involvement in the pathophysiology of fatigue in PCS. Cognitive and physical fatigue differed in the functional connectivity patterns. Functional connectivity correlates of subjective cognitive complaints were similar to physical fatigue, while connectivity related to mental fatigue partially overlapped with Stroop W-C connectivity correlates. The existence of several brain characteristics associated with fatigue severity detected by MRI could constitute a neuroimaging biomarker to objectively evaluate this symptom in clinical trials. In addition, the involvement of the central nervous system in the pathophysiology of fatigue in PCS paves the way for the use of non-invasive brain stimulation techniques to alleviate fatigue in these patients.

 

[rvallee]

Intuitively, it does seem reasonable that a change in the body would see changes in the neural networks that regulate them. In fact the opposite would be kind of odd, but then again biology doesn't care about making sense or being intuitive.

Maybe this would in turn tell us what is being dysregulated, if there is such a thing as a reliable map of which neural networks do what. Which I doubt. If the brain were as simple as what was initially expected and specific parts of the brain did specific things regulating specific parts of the body. Which we know isn't right.

But the idea that you can simply zap those brain networks and have a desired outcome seems frankly a bit silly. Even more so with fatigue. Especially since fatigue is definitely also peripheral.

Ugh. This all feels too much like growing pains, with way too much of adolescent weirdness and emotional instability mixed in that metaphor.