Exploring pain mechanisms in hypermobile Ehlers-Danlos syndrome: A case-control study.

BACKGROUND: The hypermobile type of Ehlers-Danlos syndrome (hEDS) is a heritable connective tissue disorder, associated with joint hypermobility and prominent chronic pain. Because experimental pain testing in hEDS is scarce, the underlying mechanisms are still poorly understood. OBJECTIVE: The present study assesses endogenous pain facilitation and pain inhibition in hEDS, using a protocol for temporal summation of pain (TSP), conditioned pain modulation (CPM) and exercise-induced hypoalgesia (EIH). METHODS: Twenty women with hEDS and 20 age-matched healthy controls participated. After evaluating thermal and mechanical pain thresholds (PPT), TSP was assessed using 10 repetitive painful pressure stimuli. CPM was provoked using pressure as the test stimulus and hand immersion in hot water (46°) as the conditioning stimulus. EIH was assessed after a submaximal cycling protocol. RESULTS: The hEDS group demonstrated reduced PPTs and showed significantly more TSP after repeated painful stimuli than the control group. In comparison to the healthy control group, the hEDS group demonstrated significantly less EIH at the quadriceps test location. At the trapezius, EIH did not significantly differ between groups. No significant differences were found between the hEDS group and control group in the CPM response. CONCLUSION: The results demonstrate increased TSP in hEDS, suggesting increased central pain facilitation. EIH should be studied more extensively but may be disturbed when evaluated in the muscles that are activated during exercise. The CPM results are inconclusive and require more research. SIGNIFICANCE: Studies regarding the mechanisms that underlie pain in hEDS are scarce, although it is the most prevalent and disabling symptom in this patient population. This study demonstrates increased temporal summation in hEDS and suggests that exercise-induced hypoalgesia may be reduced. Because exercise is a cornerstone in the multidisciplinary treatment of heritable connective tissue disorders, gaining knowledge in this field is important. Pressure stimuli were used to facilitate the international usability of the protocols, allowing for future data acquisition in large cohorts.

Skin Temperature during Cold Pressor Test in Fibromyalgia: an Evaluation of the Autonomic Nervous System?

INTRODUCTION: Fibromyalgia (FM) is a common chronic pain disorder characterized by whole-body pain and multiple symptoms. This study investigated potential dysfunctions of the Autonomic Nervous System (ANS) in FM patients through the measurement of the autonomic response during a cold-water test. METHODS: 23 female patients with FM and 15 healthy female controls were recruited. First, FM patients filled out the following questionnaires: PainDETECT, American College of Rheumatology (ACR) criteria of FM, and Profile of Mood States (POMS). Healthy controls only filled out the POMS. Subsequently, all participants immersed their forearm into 1 degrees C cold-water as long as they could tolerate for a maximum of 120 seconds. A thermographic camera recorded skin temperature and its recuperation process. RESULTS: The two groups differed significantly regarding central body temperature, forearm thermography, and peripheral (forearm)-central (ear) temperature ratio. FM patients showed less tolerance to cold water than control participants. Although total temperature decrease, cool-down rate, recuperation between 0 and 20 minutes after withdrawal showed significant intergroup differences, thermal recovery followed similar patterns in both groups. DISCUSSION: Peculiar ANS baseline characteristics are seen in FM patients. Although those patients have reduced ability to sustain low temperatures, therefore limiting extrapolation of inter-group analysis, their thermal-adaptive responses were found different as compared to controls.