The mapping of cortical activation by near-infrared spectroscopy might be a biomarker related to the severity of [FM] symptoms, 2021, Donadel et al

[Andy]

Full title: The mapping of cortical activation by near-infrared spectroscopy might be a biomarker related to the severity of fibromyalgia symptoms

Abstract

The delta value of oxyhemoglobin (Δ-HbO) determined by functional near-infrared spectroscopy at prefrontal cortex (PFC) and motor cortex (MC) based on primary (25 °C) and secondary (5 °C) thermal stimuli presented a larger peak latency at left MC in fibromyalgia than in controls. The difference between HbO concentration 15 s after the thermal stimuli ending and HbO concentration before the thermal stimuli onset (Δ-HbO*) at left PFC increased 47.82% in fibromyalgia and 76.66% in controls. This value had satisfactory discriminatory properties to differentiate cortical activation in fibromyalgia versus controls. A receiver operator characteristics (ROC) analysis showed the Δ-HbO* cutoffs of − 0.175 at left PFC and − 0.205 at right PFC offer sensitivity and specificity of at least 80% in screening fibromyalgia from controls. In fibromyalgia, a ROC analysis showed that these cutoffs could discriminate those with higher disability due to pain and more severe central sensitization symptoms (CSS). The ROC with the best discriminatory profile was the CSS score with the Δ-HbO* at left PFC (area under the curve = 0.82, 95% confidence interval = 0.61–100). These results indicate that cortical activation based on Δ-HbO* at left PFC might be a sensitive marker to identify fibromyalgia subjects with more severe clinical symptoms.

Open access, https://www.nature.com/articles/s41598-021-94456-2

 

[Hutan]

Fibromyalgia is a chronic primary pain condition recently defined as nociplastic1 and described as diffuse pain associated with significant emotional distress related to functional disability that cannot be better accounted for by another chronic pain condition1. Other symptoms that accompany pain include sleep disturbance, joint stiffness, headache, abdominal discomfort, cognitive impairment, and depressive symptoms2. It is a prototypical condition of central sensitivity syndrome (CSS)2,3 which encompasses widespread pain and a persistent state of high reactivity that amplifies nociceptive stimuli4. The CSS cluster of symptoms includes psychological distress, sleep disturbances, fatigue, pain, allodynia, hyperalgesia, and expansion of the receptive field5. Although the mechanisms underpinning CSS are not fully elucidated, it is characterized by hyperexcitability by impaired functioning of neurons and circuits in nociceptive pathways, with an increase in neuronal excitability and synaptic efficacy and reduced inhibition.

Hmm, they've definitely drunk the Kool-aid. 'Chronic primary pain condition', 'significant emotional distress', 'depressive symptoms', 'prototypical condition of central sensitivity syndrome', 'persistent state of high reactivity that amplifies nociceptive stimuli', 'psychological distress' - all in the first paragraph. They seem to jump from a plausible 'people with fibromyalgia having hyper-sensitive pain neurons' to a much less plausible 'people with fibromyalgia are over-reacting to everything'. Maybe they are right, but I don't think we have seen good evidence of a lack of emotional resilience in people with fibromyalgia.

fMRI and fNIRS measure brain activity by detecting changes associated with transient dynamics of the vascular response by blood oxygenation level-dependent (BOLD). These neuroimage exams can record the signal from all brain regions, unlike EEG/MEG, which are biased toward the cortical surface10. While fMRI has a higher spatial resolution, but poorer temporal resolution compared with EEG, fNIRS assesses the coupling between cerebral blood flow and neuronal activation with better temporal resolution than fMRI.

So, they used functional near-infrared spectroscopy:

Functional near-infrared spectroscopy (fNIRS) is a ... brain imaging technology that uses low levels of non-ionizing light to record changes in cerebral blood flow in the brain through optical sensors placed on the surface of the scalp.

 

[Hutan]

The study is to measure blood flow to various parts of the brain while sequentially reclining, reclining with right hand in warm water, reclining, reclining with right hand in very cold water, reclining. (sorry, added that a bit later)

Thus, in the current study, we compared the cortical activation patterns in fibromyalgia subjects and controls-based brain cortical activation after immersing the right hand into water at two different temperatures 25 °C or primary stimulus and 5 °C or secondary stimulus.

22 women in the fibromyalgia group and 19 in the control group. The controls didn't look much like the fibromyalgia group, being considerably younger, for example, and with quite different medication profiles.