Department of Neurology, Justus Liebig University, 35392, Giessen, Germany.
Department of Anaesthesiology, Justus Liebig University, 35392, Giessen, Germany.
BMC Neurol. 2021 Jul 9;21(1):272. doi: 10.1186/s12883-021-02304-7.
Human hairy (not glabrous skin) is equipped with a subgroup of C-fibers, the C-tactile (CT) fibers. Those do not mediate pain but affective aspects of touch. CT-fiber-activation reduces experimental pain if they are intact. In this pilot study we investigated pain modulating capacities of CT-afferents in CRPS.
10 CRPS-patients (mean age 33 years, SEM 3.3) and 11 healthy controls (mean age 43.2 years, SEM 3.9) participated. CT-targeted-touch (brush stroking, velocity: 3 cm/s) was applied on hairy and glabrous skin on the affected and contralateral limb. Patients rated pleasantness of CT-targeted-touch (anchors: 1 "not pleasant"-4 "very pleasant") twice daily on 10 days. Pain intensity (NRS: 0 "no pain" - 10 "worst pain imaginable") was assessed before, 0, 30, 60 and 120 min after each CT-stimulation. To assess sensory changes, quantitative-sensory-testing was performed at the beginning and the end of the trial period.
CT-targeted-touch was felt more pleasant on the healthy compared to the affected limb on hairy (p < 0.001) and glabrous skin (p 0.002), independent of allodynia. In contrast to healthy controls patients felt no difference between stimulating glabrous and hairy skin on the affected limb. Thermal pain thresholds increased after CT-stimulation on the affected limb (cold-pain-threshold: p 0.016; heat-pain-threshold: p 0.033).
CT-stimulation normalizes thermal pain thresholds but has no effect on the overall pain in CRPS. Therefore, pain modulating properties of CT-fibers might be too weak to alter chronic pain in CRPS. Moreover, CT-fibers appear to lose their ability to mediate pleasant aspects of touch in CRPS.
人类有毛（非无毛）皮肤配备了一组 C 纤维，即 C 触觉（CT）纤维。这些纤维不介导疼痛，但与触觉的情感方面有关。如果 CT 纤维完好无损，它们的激活可减轻实验性疼痛。在这项初步研究中，我们研究了 CRPS 中 CT 传入纤维的疼痛调节能力。
10 名 CRPS 患者（平均年龄 33 岁，SEM 3.3）和 11 名健康对照者（平均年龄 43.2 岁，SEM 3.9）参与了研究。在受影响和对侧肢体的有毛和无毛皮肤上应用 CT 靶向触摸（刷动，速度：3cm/s）。患者在 10 天内每天两次对 CT 靶向触摸的愉悦度进行评分（锚定：1“不愉快”-4“非常愉快”）。在每次 CT 刺激之前、0 分钟、30 分钟、60 分钟和 120 分钟评估疼痛强度（NRS：0“无痛”-10“可想象到的最痛”）。为了评估感觉变化，在试验开始和结束时进行了定量感觉测试。
与受影响的肢体相比，CT 靶向触摸在健康肢体上的有毛（p<0.001）和无毛皮肤（p<0.002）上感觉更愉悦。与健康对照者不同，患者在受影响的肢体上感觉刺激无毛和有毛皮肤之间没有差异。CT 刺激后，受影响肢体的冷痛阈值增加（冷痛阈值：p=0.016；热痛阈值：p=0.033）。
CT 刺激可使热痛阈值正常化，但对 CRPS 中的总体疼痛没有影响。因此，CT 纤维的疼痛调节特性可能太弱，无法改变 CRPS 的慢性疼痛。此外，CRPS 中 CT 纤维似乎失去了介导触觉愉悦感的能力。
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