Endogenous pain facilitation rather than inhibition differs between people with chronic fatigue syndrome, multiple sclerosis, and controls: an observational study

Simon Collin, Jo Nijs, Mira Meeus, Andrea Polli, Barbara Willekens, Kelly Ickmans

Research output: Contribution to journalArticle (Academic Journal)peer-review

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Abstract

Background: 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.
Objectives: To compare experimental pain measurements in CFS and MS patients and healthy controls.
Study design: Observational study
Setting: This study took place in Belgium at Vrije Universiteit Brussel and the University of Antwerp.
Methods: 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 verbal numerical scale (2nd cuff pressure threshold) were measured in CFS patients (n=48), MS patients (n=19) and healthy pain-free controls (n=30). Adjusted between-group differences were estimated using linear regression models.
Results: Finger pain pressure thresholds of CFS patients, compared with MS patients, 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 MS patients, CFS patients had 29% lower 1st 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 CFS than in MS patients (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 CFS and MS patients 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 CFS but not in MS patients was strongly negatively correlated with pain pressure thresholds and cuff pressure thresholds, and positively correlated with temporal summation.
Limitations: The main limitations of our study are the relatively small sample sizes, its cross-sectional design, and its exploratory nature.
Conclusions: We found differences in the characteristics of pain symptoms reported by CFS and MS patients, which suggest different underlying mechanisms. Specifically, overactive endogenous pain facilitation was characteristic of pain in CFS but not in MS patients, suggesting a greater role for central sensitization in CFS.
Original languageEnglish
Pages (from-to)E489-E497
Number of pages9
JournalPain Physician
Volume20
Issue number4
Early online date16 May 2017
Publication statusPublished - May 2017

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