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 patients with CFS or MS 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 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.
Results: 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.
Limitations: The main limitations of our study are the relatively small sample sizes, its crosssectional design, and its exploratory nature.
Conclusions: 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.
Keywords: Chronic fatigue syndrome, CFS/ME, multiple sclerosis, experimental pain, central
sensitization