Kosek Eva, Hansson Per
Department of Surgical Sciences, Karolinska Institute/Hospital, S-171 77 Stockholm, Sweden.
Pain. 2003 Sep;105(1-2):125-31. doi: 10.1016/s0304-3959(03)00171-4.
The aim of the study was to investigate the perceptual integration of simultaneous stimulation in a focal and a referred pain area to investigate whether referred pain is mainly caused by facilitation of on-going input from the referred pain area by stimulation in the focal pain area or if referred pain is a consequence of misinterpretation of the origin of inputs from the focal pain area. Pain was induced in twelve healthy individuals by intramuscular electrical stimulation in the left infraspinatus muscle (MI) or the left dorsolateral upper arm (UA), i.e. the area of referral commonly reported from stimulation in MI. Conditioning stimulation consisted of, in a counterbalanced order, no stimulation (baseline) and pain intensity rated as 2/10 and 4/10, respectively, on a category scale. During conditioning stimulation in MI, sensitivity to test stimuli was assessed in UA and vice versa. The test stimuli consisted of i.m. electrical stimulation corresponding to the perception threshold to innocuous electrical stimulation, the electrical pain threshold (EPT), and pain intensity rated as 2/10, 4/10 and 6/10, respectively. Conditioning stimulation corresponding to 2/10 did not result in a statistically significant change in sensitivity to any test stimuli in either location. During conditioning stimulation corresponding to 4/10 in m. infraspinatus, all twelve subjects reported referred pain in the dorsolateral upper arm. Compared to baseline, EPTs decreased in the referred pain area (P<0.001), while no other statistically significant changes in sensitivity to test stimuli were seen. Conditioning stimulation corresponding to 4/10 in the dorsolateral upper arm gave rise to referred pain in one individual (area of m. biceps brachii), and no statistically significant changes were seen in the sensitivity to electrical stimuli in m. infraspinatus. In conclusion, an effect at pain threshold level only was documented during simultaneous stimulation in the focal and referred pain area, which does not support facilitation of inputs from the referred pain area as the main mechanism generating referred pain. Instead, referred pain is most likely a consequence of misinterpretation of the origin of input from the stimulated focal pain area, due to excitation of neurones somewhere along the neuroaxis with projected fields in the referred pain area. The fact that conditioning stimulation in m. infraspinatus generated referred pain in the dorsolateral upper arm, but not vice versa suggests that the divergence of the input is not reciprocally arranged.
本研究的目的是调查在局部疼痛区域和牵涉痛区域同时进行刺激时的感觉整合情况，以探究牵涉痛主要是由局部疼痛区域的刺激促进了来自牵涉痛区域的持续输入所致，还是由于对来自局部疼痛区域的输入起源的错误解读所致。通过对12名健康个体的左冈下肌（MI）或左上臂背外侧（UA）进行肌内电刺激来诱发疼痛，UA即通常报道的MI刺激所引发的牵涉痛区域。条件刺激按平衡顺序包括无刺激（基线）以及在分类量表上分别评定为2/10和4/10的疼痛强度。在MI进行条件刺激时，评估UA对测试刺激的敏感性，反之亦然。测试刺激包括对应于无害电刺激感知阈值的肌内电刺激、电痛阈值（EPT）以及分别评定为2/10、4/10和6/10的疼痛强度。对应于2/10的条件刺激在任一部位对任何测试刺激的敏感性均未产生统计学上的显著变化。在冈下肌进行对应于4/10的条件刺激时，所有12名受试者均报告在上臂背外侧出现牵涉痛。与基线相比，牵涉痛区域的EPT降低（P<0.001），而对测试刺激的敏感性未见其他统计学上的显著变化。在上臂背外侧进行对应于4/10的条件刺激时，有一名个体（肱二头肌区域）出现牵涉痛，而冈下肌对电刺激的敏感性未见统计学上的显著变化。总之，在局部疼痛区域和牵涉痛区域同时进行刺激时，仅在疼痛阈值水平记录到了一种效应，这并不支持促进来自牵涉痛区域的输入作为产生牵涉痛的主要机制。相反，牵涉痛很可能是由于沿着神经轴在某处神经元兴奋，其投射场在牵涉痛区域，从而对来自受刺激局部疼痛区域的输入起源产生错误解读的结果。冈下肌的条件刺激在上臂背外侧产生了牵涉痛，但反之则不然，这一事实表明输入的发散并非相互安排的。
