健康与遗传心理学研究室知识库

经皮神经电刺激是一种通过置于皮肤表面的电极施加特定参数的电流，激活外周神经纤维，从而对急、慢性疼痛的产生缓解作用的物理镇痛疗法。临床上常用的TENS包括“常规型TENS”和“针刺样TENS”两种类型，两者在参数设置上存在很大差异。以往的研究认为，常规型TENS的镇痛原理是闸门控制理论所支持的“以触镇痛”，即高频率、低强度的常规型TENS可以选择性地激活非伤害性传入神经（Aβ纤维），从而产生皮节内的局部镇痛效果；而针刺样TENS的镇痛原理则是弥漫性伤害抑制控制理论所支持的“以痛镇痛”，通过激活直径较小、传导痛觉和温觉的Adelta纤维和C纤维，通过中枢调控产生不局限于刺激位置的全局镇痛效果。但是目前针对这两种TENS的镇痛原理仍存在一定的争议，且多数直接结论均源自动物研究，以人为对象的研究多进行间接推论，无法针对争论所涉及的脊髓机制进行直接验证。针对这一现状，本研究借助行为实验和脑脊髓同步成像方法，在主观和客观两个维度探究经皮神经电刺激镇痛的效果及其脑脊机制。

研究一通过行为实验验证TENS的镇痛效果。通过判断被试TENS刺激前后主观评分变化（包括疼痛强度和疼痛不愉悦度两个指标）证明了常规TENS和针刺样TENS相比对照组都对接触性热痛具有镇痛效果，而且两者的镇痛范围不同。具体而言，常规型TENS只对同侧施加在同一皮节区域的热痛刺激存在显著镇痛作用，而对侧未接受TENS刺激区域无显著镇痛作用，双侧镇痛效果差异显著；针刺样TENS对于施加在同侧和对侧的热痛刺激均具有显著镇痛作用，而且双侧镇痛效果差异不显著；仅施加虚假TENS的控制组双侧均未产生镇痛作用。

研究二基于脑与脊髓同步功能成像技术探究TENS镇痛的脑脊机制。研究通过对平面回波成像序列增大视场，同时并行激发采集多层图像以及添加颈髓局部匀场框的方法实现了高质量的头颈联合功能磁共振成像，可以用于直接比较不同类型TENS镇痛前后接触性热痛对脑和颈髓激活区域和激活程度变化。研究结果证明常规型TENS和针刺样TENS均会引起疼痛矩阵中的部分脑区以及脊髓C5/6节段（对应热痛刺激皮节位置）出现激活变化，激活变化模式与行为评分变化模式一致。具体而言，常规型TENS组仅在TENS同侧处理手的大脑和脊髓C5/6节段引起与行为镇痛效果正相关的疼痛激活变化，针刺样TENS组在同侧处理手和对侧非处理手引起的脑与脊髓C5/6节段疼痛激活均存在显著变化，且激活变化量和行为镇痛效果存在显著相关性，均是由于TENS刺激所引起的。

本论文在行为、大脑和脊髓三个层面探究了常规型和针刺样TENS的镇痛效果和镇痛机制，结果证明常规型和针刺样TENS都具有镇痛效果，并且两者镇痛的范围不同，这种差异在大脑和脊髓层面得到了进一步的证实。这也支持了我们的前提假设，即常规型TENS的镇痛是脊髓主导的皮节范围的疼痛抑制，而针刺样TENS镇痛则是由于中枢调控引起的弥散性疼痛抑制，两者在机制和效果方面均有差异，因此在临床应用中应该结合疼痛位置和疼痛类型选择合适的TENS干预方法。

Transcutaneous electrical nerve stimulation is a kind of physical analgesic therapy that applies specific parameters of current through electrodes placed on the surface of the skin to activate peripheral nerve fibers to relieve acute and chronic pain. Clinically, TENS includes two modes: "conventional TENS" and "acupuncture-like TENS." The parameter settings of the two are very different. Previous studies have shown that the analgesic mechanism of conventional TENS is "analgesia with touch" supported by the gate control theory, which can selectively activate non-invasive afferent nerves (Aβ fibers), thereby producing local analgesia within the dermis pain effect. The analgesic mechanism of acupuncture-like TENS is "analgesic with pain" supported by the theory of diffuse noxious inhibitory controls (DNIC), which mainly activates Adelta fibers and C fibers with small diameters that mediate pain and temperature and could produce a global analgesic effect that is not limited to the stimulation location. However, there is still some controversy about the analgesic mechanism of these two types of TENS, and most of the direct conclusions are derived from animal studies. Studies on humans are often indirectly inferred, and the spinal cord mechanism involved in the analgesic phenomenon cannot be directly verified. In response to this situation, this study explored the effects of percutaneous nerve electrical stimulation on analgesia and its cerebrospinal mechanism in both subjective and objective dimensions with the help of behavioral experiments and synchronized cerebral spinal cord imaging.

In the first study, we use the behavioral experiment method to confirm the analgesic effect of different types of TENS. The subjective ratings (pain intensity and pain unpleasantness) changes proved that conventional TENS and acupuncture-like TENS had different analgesic effects and analgesic regions in contact with heat pain compared with the sham control group. Specifically, the conventional TENS only has a significant analgesic effect when the thermal pain stimulation applied to the same dermal region on the same side. In contrast, the area on the contralateral side has no significant analgesic effect, and the bilateral analgesic effect is significantly different. Acupuncture-like TENS has significant analgesic effects on both the ipsilateral and contralateral thermal pain stimuli, and have no significant difference in bilateral analgesic effects. No analgesic effect was produced on both sides of the control group that only applied sham TENS.

The second study explores the mechanism of TENS analgesia based on the simultaneous imaging of the brain and cervical cord. By increasing the field of view of the planar echo imaging sequence, simultaneously exciting multiple slices of images and adding local shim boxes on the cervical spinal cord, high-quality head and neck combined functional magnetic resonance imaging is achieved, which can be used to explore the mechanism of different types of TENS directly. The contact heat pain evoked brain and cervical spinal cord activation was changing after TENS. The results of statistical analysis prove that both conventional TENS and acupuncture-like TENS can evoke activation changes in some brain regions in the pain matrix and C5/6 levels of the spinal cord. The activation change pattern is consistent with the behavior analgesic effect. The conventional TENS group has a wide range of activation changes after the treatment of TENS and positively related to the behavioral analgesic effect. There are significant changes in the activation of the brain and spinal cord caused by the acupuncture-like TENS group in the treatment and un-treatment hands and have a significant correlation with behavioral analgesic effect.

This study explores the analgesic effect and analgesic mechanism of conventional and acupuncture-like TENS at three levels of behavior, brain, and spinal cord. The results prove that both conventional and acupuncture-like TENS have analgesic effects of different analgesic region, which further confirmed at the brain and spinal cord levels. These results also support our hypothesis that conventional TENS analgesia is the spinal dermal-segment-based local pain inhibition, while acupuncture-like TENS analgesia is caused by central modulation and has diffuse pain inhibition effect. There are differences in mechanism and effect of different types of TENS, so in clinical application, the appropriate TENS intervention method should be selected based on the location and type of pain.