Processing of Laser-Evoked Potentials in Patients with Chronic Whiplash-Associated Disorders, CFS, and Healthy Controls, 2020, Goudman et al

Andy · May 20, 2020

Objective
Laser-evoked potentials (LEPs) are among the reliable neurophysiological tools to investigate patients with neuropathic pain, as they can provide an objective account of the functional status of thermo-nociceptive pathways. The goal of this study was to explore the functioning of the nociceptive afferent pathways by examining LEPs in patients with chronic whiplash-associated disorders (cWAD), patients with chronic fatigue syndrome (CFS), and healthy controls (HCs).

Design
Case–control study.

Setting
A single medical center in Belgium.

Subjects
The LEPs of 21 patients with cWAD, 19 patients with CFS, and 18 HCs were analyzed in this study.

Methods
All participants received brief nociceptive CO2 laser stimuli applied to the dorsum of the left hand and left foot while brain activity was recorded with a 32-channel electroencephalogram (EEG). LEP signals and transient power modulations were compared between patient groups and HCs.

Results
No between-group differences were found for stimulus intensity, which was supraliminal for Aδ fibers. The amplitudes and latencies of LEP wave components N1, N2, and P2 in patients with cWAD and CFS were statistically similar to those of HCs. There were no significant differences between the time–frequency maps of EEG oscillation amplitude between HCs and both patient populations.

Conclusions
EEG responses of heat-sensitive Aδ fibers in patients with cWAD and CFS revealed no significant differences from the responses of HCs. These findings thus do not support a state of generalized central nervous system hyperexcitability in those patients.
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Paywall, https://academic.oup.com/painmedicine/article-abstract/doi/10.1093/pm/pnaa068/5820105
Sci hub, https://sci-hub.tw/10.1093/pm/pnaa068

ETA: Added Sci hub link

wigglethemouse · Apr 15, 2020

Looks like PDF access is free, no paywall, if you click on the PDF symbol

I'm not able to read in detail, but I took a look at patient selection section. Wouldn't a key part of the investigation of neuropathic pain be to perform traditional diagnostic methods in parallel to confirm a neuropathic biological process? One method could be skin biopsy to look at nerve density that would have confirmed the diagnosis of small fiber neuropathy in patients, who could then undergo the test to confirm the Laser-evoked potentials method can detect a valid change that might indicate CNS fiber issues as well.

In the end this paper tells us nothing, as we don't know that their pain is neuropathic. Or maybe I need to read the paper and understand what LEP is all about.

EDIT : I removed my link to the PDF as it times out. Please click on the PDF symbol on the official paper website

rvallee · Apr 15, 2020

Seemed like a long shot with a very specific tool.

https://www.ncbi.nlm.nih.gov/pubmed/14678844

Limitations for the use of LEP are pointed out, too, like the uncertainty of lesion location along these pathways and the fact that LEP can reliably show correlates of reduced nociceptive function but only rarely of enhanced transmission (like in hyperalgesia).
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Unclear how specific and reliable, but it seems only useful to show reduced pain transmission, not increased, which is what was examined here.

Though considering the objective it's weird they did not include people with fibromyalgia or neuropathy. Weird study.

Dolphin · Dec 18, 2022

The full text is available for free here:
https://dial.uclouvain.be/pr/boreal/object/boreal:250018/datastream/PDF_01/view

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Processing of Laser-Evoked Potentials in Patients with Chronic Whiplash-Associated Disorders, CFS, and Healthy Controls, 2020, Goudman et al

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Processing of Laser-Evoked Potentials in Patients with Chronic Whiplash-Associated Disorders, CFS, and Healthy Controls, 2020, Goudman et al

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