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Endogenous Pain Facilitation Rather Than Inhibition Differs between CFS, MS, and Controls

Discussion in 'Latest ME/CFS Research' started by hixxy, May 24, 2017.

  1. hixxy

    hixxy Senior Member

    Pain Physician. 2017 May;20(4):E489-E497.

    Endogenous Pain Facilitation Rather Than Inhibition Differs Between People with Chronic Fatigue Syndrome, Multiple Sclerosis, and Controls: An Observational Study.

    Collin SM, Nijs J, Meeus M, Polli A, Willekens B, Ickmans K.


    Commonalities in the core symptoms of fatigue and cognitive dysfunction experienced by chronic fatigue syndrome (CFS, also known as ME) and multiple sclerosis (MS) patients have been described. Many CFS and MS patients also experience chronic pain, which has been attributed to central sensitization in both groups of patients. However, the characteristics of pain in CFS and MS patients have not been compared.

    To compare experimental pain measurements in patients with CFS or MS and healthy controls.

    Observational study.

    This study took place in Belgium at Vrije Universiteit Brussel and the University of Antwerp.

    Pressure pain thresholds, temporal summation, conditioned pain modulation, and occlusion cuff pressure thresholds rated as painful (1st cuff pressure threshold) and as 3/10 on a verbal numerical scale (2nd cuff pressure threshold) were measured in patients with CFS (n = 48), MS (n = 19) and healthy pain-free controls (n = 30). Adjusted between-group differences were estimated using linear regression models.

    Finger pain pressure thresholds of patients with CFS, compared with patients with MS, were 25% lower (difference ratio 0.75 [95% CI 0.59, 0.95], P = 0.02) and shoulder pain pressure thresholds were 26% lower (difference ratio 0.74 [0.52, 1.04], P = 0.08). Compared with patients with MS, patients with CFS had 29% lower first cuff pressure threshold (difference ratio 0.71 [0.53, 0.94], P = 0.02) and 41% lower 2nd cuff pressure threshold (0.59 [0.41, 0.86], P = 0.006). Finger temporal summation was higher in patients with CFS than in patients with MS (mean difference 1.15 [0.33, 1.97], P = 0.006), but there were no differences in shoulder temporal summation or conditioned pain modulation at either site. Differences between patients with CFS and MS tended to be greater than between either patient group and healthy controls. Pain pressure thresholds and cuff pressure thresholds tended to be positively correlated, and temporal summation negatively correlated, with higher physical function and lower fatigue in both groups of patients. Subjective pain in patients with CFS but not in patients with MS was strongly negatively correlated with pain pressure thresholds and cuff pressure thresholds, and positively correlated with temporal summation.

    The main limitations of our study are the relatively small sample sizes, its cross-sectional design, and its exploratory nature.

    We found differences in the characteristics of pain symptoms reported by patients with CFS and patients with MS, which suggest different underlying mechanisms. Specifically, overactive endogenous pain facilitation was characteristic of pain in patients with CFS but not in patients with MS, suggesting a greater role for central sensitization in CFS.

    PMID: 28535557
    SamanthaJ and Hutan like this.
  2. Hutan

    Hutan Senior Member

    New Zealand
    I haven't seen the full paper.

    So, they presumably didn't find significant differences in pain thresholds and the like between people with CFS and healthy controls (and between people with MS and healthy controls). Why don't they say that in their conclusion? (rhetorical question).

    The differences found between people with CFS and people with MS that they make so much of could easily be an artefact of the small sample size (especially the MS sample).

    The adjustment process provides scope for fudging stuff. Maybe there were differences in the ages or gender mix of the samples.
    Manganus, Effi, Valentijn and 2 others like this.
  3. Snow Leopard

    Snow Leopard Hibernating

    South Australia
    This study was poorly matched with regards to gender 64.1% (HC n=39) 68.4% (MS n=19) 95.8% (CFS n=48). Specifically the CFS group only had two men out of 48, vs fourteen out of thirty-nine for HC.

    The results attempted to statistically control for gender, but I wonder how this could have effected the results?

    Comparing the CFS group to healthy controls (HC), the following measurements were not significant:
    Pain pressure threshold finger
    1st cuff pressure threshold
    2nd cuff pressure threshold was not significant when correcting for multiple comparisons
    Temporal summation finger
    Temporal summation shoulder
    Conditioned pain modulation finger
    Conditioned pain modulation shoulder

    Comparing the CFS group to healthy controls (HC), the following measurements were significant:
    Pain pressure threshold shoulder.

    Of the Pairwise correlations between experimental pain measurements and patient-reported characteristics, only a few were significant (P < 0.007 (Bonferroni-adjusted P < 0.05)):
    CIS reduced physical activity was associated with Temporal summation finger for CFS patients
    Visual analogue pain (VAS) rating was associated with Temporal summation finger, Temporal summation shoulder, 2nd cuff pressure threshold. Keeping in mind that self reported pain on the VAS was one of the biggest symptomatic differences reported between MS and CFS - MS reported the same as healthy controls.

    Pain pressure method:
    Given that only one of the eight measurements was statistically significant and there were substantial gender differences, this is a fairly weak result that doesn't provide much confidence for the "central sensitization of pain" theory.
  4. A.B.

    A.B. Senior Member

    Haven't read the paper, but they did not appear to have measured central sensitization and therefore do not know whether the increased pain reflects a central or local problem.

    This tendency to interpret findings that are not particularly specific as consistent with a specific explanatory model while not considering alternatives is indicative of bias. We've seen the same behaviour by the BPS model proponents and it's a good recipe to end up with a wrong model. It's not difficult to collect data in favor of an explanatory model. One could theorize that increased pain sensitivity is characteristic of demonic possession and that therefore any finding of increased pain sensitivity is consistent with demonic possession.
    Hutan, Effi, Aroa and 1 other person like this.
  5. Aroa



  6. Effi

    Effi Senior Member

    I wish this team would stop conflating CFS with chronic pain conditions. Tbh I wish this team would stop working on CFS altogether. Pretty much every single one of their papers I have read so far was written clearly for the sole purpose of making people believe central sensitization is a thing. (Many researchers have tried to prove this hypothesis over the years, so far all have failed. It's time to move on from this!) Also, they need a reason for their association 'Pain in Motion' to exist. Their samples are always so ridiculously small, their illness criteria are warped at best, and their conclusions are always the same: central sensitization and/or gentle movement as a tool towards rehabilitation. :cautious:
    Manganus, Hutan, Snow Leopard and 2 others like this.

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