Institute of Interventional Pain Medicine Zurich, IISZ, Zurich, Switzerland.
Department of Anesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
Scand J Pain. 2023 Jun 12;23(4):735-742. doi: 10.1515/sjpain-2023-0020. Print 2023 Oct 26.
Muscle pain can be associated with hyperalgesia that may spread outside the area of primary injury due to both peripheral and central sensitization. However, the influence of endogenous pain inhibition is yet unknown. This study investigated how endogenous pain inhibition might influence spreading hyperalgesia in experimental muscle pain.
Conditioned pain modulation (CPM) was assessed in 30 male volunteers by cold pressor test at the non-dominant hand as conditioning and pressure pain thresholds (PPT) at the dominant 2nd toe as test stimuli. Subjects were classified as having inhibitory or facilitating CPM based on published reference values. Subsequently, muscle pain and hyperalgesia were induced by capsaicin injection into the non-dominant supraspinatus muscle. Before and 5, 10, 15, 20, 30, 40, 50 and 60 min later, PPTs were recorded at the supraspinatus, infraspinatus and deltoid muscle, ring finger and toe.
Compared to baseline, PPTs decreased at the supraspinatus, infraspinatus and deltoid muscle (p≤0.03), and increased at the finger and toe (p<0.001). In facilitating CPM (n=10), hyperalgesia occurred at 5, 10, 15, 20 and 40 min (p≤0.026). In inhibitory CPM (n=20), hyperalgesia only occurred after 10 and 15 min (p≤0.03). At the infraspinatus muscle, groups differed after 5 and 40 min (p≤0.008).
The results suggest that facilitating CPM is associated with more spreading hyperalgesia than inhibitory CPM. This implies that poor endogenous pain modulation may predispose to muscle pain and spreading hyperalgesia after injury, and suggest that strategies to enhance endogenous pain modulation may provide clinical benefits.
肌肉疼痛可伴有痛觉过敏，这种痛觉过敏可由于外周和中枢敏化而扩散到原发损伤区域之外。然而，内源性疼痛抑制的影响尚不清楚。本研究旨在探讨内源性疼痛抑制如何影响实验性肌肉疼痛中的扩散性痛觉过敏。
通过非优势手的冷加压试验评估 30 名男性志愿者的条件性疼痛调制（CPM），以作为条件刺激，用优势第二趾的压痛阈值（PPT）作为测试刺激。根据已发表的参考值，将受试者分为具有抑制性或易化性 CPM。随后，在非优势肩峰下肌注射辣椒素以诱导肌肉疼痛和痛觉过敏。在注射前和注射后 5、10、15、20、30、40、50 和 60 分钟，记录肩峰下肌、冈下肌和三角肌、环指和趾的 PPT。
与基线相比，肩峰下肌、冈下肌和三角肌的 PPT 降低（p≤0.03），而手指和趾的 PPT 增加（p<0.001）。在易化 CPM 组（n=10）中，痛觉过敏发生在 5、10、15、20 和 40 分钟时（p≤0.026）。在抑制性 CPM 组（n=20）中，痛觉过敏仅在 10 和 15 分钟时发生（p≤0.03）。在冈下肌，两组在 5 和 40 分钟时存在差异（p≤0.008）。
结果表明，易化 CPM 与更多的扩散性痛觉过敏相关，而抑制性 CPM 则不然。这表明，内源性疼痛抑制不良可能使受伤后更容易发生肌肉疼痛和扩散性痛觉过敏，并提示增强内源性疼痛抑制的策略可能具有临床益处。
