Associations between cognitive performance and pain in chronic fatigue syndrome : comorbidity with fibromyalgia does matter

Background: In addition to the frequently reported pain complaints, performance-based cognitive capabilities in patients with chronic fatigue syndrome (CFS) with and without comorbid fibromyalgia (FM) are significantly worse than those of healthy controls. In various chronic pain populations, cognitive impairments are known to be related to pain severity. However, to the best of our knowledge, the association between cognitive performance and experimental pain measurements has never been examined in CFS patients. Objectives: This study aimed to examine the association between cognitive performance and self-reported as well as experimental pain measurements in CFS patients with and without FM. Study Design: Observational study. Setting: The present study took place at the Vrije Universiteit Brussel and the University of Antwerp. Methods: Forty-eight (18 CFS-only and 30 CFS+FM) patients and 30 healthy controls were studied. Participants first completed 3 performance-based cognitive tests designed to assess selective and sustained attention, cognitive inhibition, and working memory capacity. Seven days later, experimental pain measurements (pressure pain thresholds [PPT], temporal summation [TS], and conditioned pain modulation [CPM]) took place and participants were asked to fill out 3 questionnaires to assess self-reported pain, fatigue, and depressive symptoms. Results: In the CFS+FM group, the capacity of pain inhibition was significantly associated with cognitive inhibition. Self-reported pain was significantly associated with simple reaction time in CFS-only patients. The CFS+FM but not the CFS-only group showed a significantly lower PPT and enhanced TS compared with controls. Limitations: The cross-sectional nature of this study does not allow for inferences of causation. Conclusions: The results underline disease heterogeneity in CFS by indicating that a measure of endogenous pain inhibition might be a significant predictor of cognitive functioning in CFS patients with FM, while self-reported pain appears more appropriate to predict cognitive functioning in CFS patients without FM

Unravelling Impaired Hypoalgesia at Rest and in Response to Exercise in Patients with Chronic Whiplash-Associated Disorders:Effects of a Single Administration of Selective Serotonin Reuptake Inhibitor versus Selective Norepinephrine Reuptake Inhibitor

(1) Background: Noradrenaline and serotonin have modulatory roles in pain signaling and in exercise-induced hypoalgesia. Patients with chronic whiplash-associated disorders often show impaired exercise-induced hypoalgesia. Therefore, this study aimed to examine the isolated effect of activating serotonergic or noradrenergic descending pathways on hypoalgesia at rest and in response to exercise in patients with chronic WAD by using respectively a single dose of a selective serotonin reuptake inhibitor (SSRI) and a selective norepinephrine reuptake inhibitor (NRI). (2) Methods: Twenty-five people with chronic WAD participated in this double-blind randomized controlled crossover experiment. Serotonin and noradrenaline concentrations were modulated by the oral ingestion of a single dose of citalopram (i.e., SSRI) or atomoxetine (i.e., SNRI). Quantitative sensory testing (including pressure pain thresholds and conditioned pain modulation) was measured before and after exercise in combination with no medication (1), atomoxetine (2), or citalopram (3) at three different test days. (3) Results: Random-intercept linear mixed models analysis was used to analyze pain outcomes (i.e., pain at rest and exercise-induced hypoalgesia) before and after exercise over the three conditions in patients with chronic WAD. No differences in pain at rest were found between the three conditions before exercise. The effect of exercise on pain outcome measures was not influenced by medication intake. The occupational status of the participants had a significant influence on the effect of exercise and medication on pain outcomes (p &lt; 0.05). Patients working full-time had some positive effect of atomoxetine on pain facilitation (p &lt; 0.05). Unemployed patients had some negative effect of citalopram on pain tolerance and experienced exercise-induced hypoalgesia (p &lt; 0.05). (4) Conclusions: A single dose of citalopram or atomoxetine did not result in changes in hypoalgesia at rest and in response to exercise. These results do not support the use of SSRI or selective NRI to overcome impaired hypoalgesia at rest or in response to exercise in people with chronic WAD. Effect of exercise and medication on pain in patients with chronic WAD is influenced by the occupational status.</p

Does motor cortex engagement during movement preparation differentially inhibit nociceptive processing in patients with chronic whiplash associated disorders, chronic fatigue syndrome and healthy controls? An experimental study

Background: Patients with chronic fatigue syndrome (CFS) and chronic whiplash associated disorders (cWAD) present a reduced ability to activate central descending nociceptive inhibition after exercise, compared to measurements before exercise. It was hypothesised that a dysfunctional motor-induced inhibition of nociception partly explains this dysfunctional exercise-induced hypoalgesia. This study investigates if engagement of the motor system during movement preparation inhibits nociception-evoked brain responses in these patients as compared to healthy controls (HC). Methods: The experiment used laser-evoked potentials (LEPs) during three conditions (no task, mental task, movement preparation) while recording brain activity with a 32-channel electroencephalogram in 21 patients with cWAD, 20 patients with CFS and 18 HC. Two-factor mixed design Analysis of variance were used to evaluate differences in LEP amplitudes and latencies. Results: No differences in N1, N2, N2P2, and P2 LEP amplitudes were found between the HC, CFS, and cWAD groups. After nociceptive stimulation, N1, N2 (only at hand location), N2P2, and P2 LEP amplitudes significantly decreased during movement preparation compared to no task (within group differences). Conclusion: Movement preparation induces a similar attenuation of LEPs in patients with CFS, patients with cWAD and HC. These findings do not support reduced motor-induced nociceptive inhibition in these patients