【晨读】脊髓电刺激（七）
英语晨读 ·
山东省立医院疼痛科英语晨读已经坚持10余年的时间了，每天交班前15分钟都会精选一篇英文文献进行阅读和翻译。一是可以保持工作后的英语阅读习惯，二是可以学习前沿的疼痛相关知识。我们会将晨读内容与大家分享，助力疼痛学习。
本次文献选自ROCK AK , Truong H , Park YL, et al. Spinal Cord Stimulation[J]. Neurosurg Clin N Am, 2019, 30(2):169-194.本次学习由谢珺田副主任医师主讲。
Although trial implants are generally performed under local anesthesia, permanent implants may either be performed awake or asleep with intraoperative neuromonitoring. The decision usually depends on the type of lead being implanted and the workflow of the surgeon and their team. Both modalities involve direct feedback from the patient, electromyography, and/or somatosensory evoked potentials with intraoperative neuromonitoring. Difficulties for awake implantation may arise when paddle leads are being implanted or when the patient is anxious, obese, or has a history of obstructive sleep apnea. In some cases, waking up the patient intraoperatively places extra stress on the surgeon and/or anesthesiologist. Reports suggest that placement while the patient is asleep has similar or superior outcomes as compared with awake placement. Occasionally, paddle lead placement may also be offered under epidural or spinal anesthesia.
清醒与睡眠
测试电极植入通常在局部麻醉下进行，而永久植入电极可以在完善术中神经监测的清醒/或睡眠状态下进行。具体采取何种手术方式通常取决于植入电极的类型，和手术医生及其团队的工作流程。这两种手术方式都必须有患者的直接反馈、肌电图和/或术中神经监测的体感诱发电位。当病人肥胖、合并焦虑状态或有阻塞性睡眠呼吸暂停病史时，可能会导致清醒手术电极植入困难。在某些情况下，术中叫醒病人会给手术医生和/或麻醉医师增加额外的负担。临床报道显示，与清醒植入电极相比，患者在睡眠时植入电极具有相似或更好的效果。有时，手术电极也可在硬膜外麻醉或腰麻下进行植入。
Waveforms
Results from major RCTs related to types of waveform patterns used for SCS are presented in Table 6. Over the past 10 years, alternative waveforms have become the most dynamic part in SCS. Traditional systems deliver continuous stimulation at low frequency around 50 Hz and provide pain relief together with paresthesia. Successful stimulation was explained by gate control theory of pain and guided practice toward stimulation-induced paresthesia that overlaps with the painful region. In 2010, the notion of “paresthesia-free pain suppression,” was introduced, which has substantially changed SCS. The mechanism of action remains unclear. Arle and coworkers suggest that (1) high frequency preferentially blocks largediameter fibers, (2) large diameter fibers convey vibratory sensation, which is associated with paresthesia; and (3) high-frequency stimulation, while blocking action potentials of large fibers, recruits medium-diameter fibers, which produce the pain relief effect. Others implicate involvement of wide dynamic range neurons and/or modulation of the dorsal horn.
波形编程方案
与SCS所采用波形编程相关的主要RCT研究结果如表6所示。在过去的10年里，各种不同的波形编程方案已经成为SCS新的研究热点。传统方案是在50赫兹左右的低频率下产生持续的刺激，在疼痛缓解的同时可伴有治疗区的感觉异常。作用机制可用痛觉门控制理论来解释，并可依此指导临床上将电刺激引起的感觉异常范围覆盖的疼痛区域。2010年，“无感觉异常的疼痛抑制”这一概念的提出，大大改变了大家对SCS的认知。其作用机制尚不清楚。Arle及其同事认为：（1）高频刺激优先阻断大直径纤维；（2）大直径纤维传递振动感觉，与感觉异常有关；（3）高频刺激在阻断大纤维动作电位的同时，激活中等直径纤维，产生镇痛效果。其它机制则涉及广动力范围神经元和/或调节背角神经元。