Datasheet1_Effect of spinal anesthesia-induced deafferentation on pain processing in healthy male volunteers: A task-related fMRI study.pdf

BackgroundSpinal anesthesia causes short-term deafferentation and alters the crosstalk among brain regions involved in pain perception and pain modulation. In the current study, we examined the effect of spinal anesthesia on pain response to noxious thermal stimuli in non-deafferented skin areas using a functional magnetic resonance imaging (fMRI) paradigm.
MethodsTwenty-two healthy subjects participated in the study. We performed a task-based fMRI study using a randomized crossover design. Subjects were scanned under two conditions (spinal anesthesia or control) at two-time points: before and after spinal anesthesia. Spinal anesthesia resulted in sensory loss up to dermatome Th6. Calibrated heat-pain stimuli were administered to the right forearm (C8-Th1) using a box-car design (blocks of 10s on/25s off) during MRI scanning. Pain perception was measured using a visual analogue scale (1–100) at the beginning and the end of each session. Generalized estimating equations were used to examine the effect of intervention by time by order on pain scores. Similarly, higher-level effects were tested with appropriate general linear models (accounting for within-subject variations in session and time) to examine: (1) Differences in BOLD response to pain stimulus under spinal anesthesia versus control; and (2) Effects of spinal anesthesia on pain-related modulation of the cerebral activation.
ResultsComplete fMRI data was available for eighteen participants. Spinal anesthesia was associated with moderate pain score increase. Significant differences in brain response to noxious thermal stimuli were present in comparison of spinal versus control condition (post—pre). Spinal condition was associated with higher BOLD signal in the bilateral inferior parietal lobule and lower BOLD signal in bilateral postcentral and precentral gyrus. Within the angular regions, we observed a positive correlation between pain scores and BOLD signal. These observations were independent from order effect (whether the spinal anesthesia was administered in the first or the second visit). However, we did observe order effect on brain regions including medial prefrontal regions, possibly related to anticipation of the experience of spinal anesthesia.
ConclusionsThe loss of sensory and motor activity caused by spinal anesthesia has a significant impact on brain regions involved in the sensorimotor and cognitive processing of noxious heat pain stimuli. Our results indicate that the anticipation or experience of a strong somatosensory response to the spinal intervention might confound and contribute to increased sensitivity to cognitive pain processing. Future studies must account for individual differences in subjective experience of pain sensation within the experimental context.

背景：脊髓麻醉可引发短期去传入效应，并改变参与疼痛感知与疼痛调控的脑区间的信号串扰。本研究中，我们借助功能磁共振成像（functional magnetic resonance imaging，fMRI）范式，探究了脊髓麻醉对非去传入皮肤区域受到伤害性热刺激时的疼痛反应的影响。
方法：本研究共纳入22名健康受试者。我们采用随机交叉设计开展任务态功能磁共振成像研究。受试者分别在两个时间点（脊髓麻醉前、脊髓麻醉后）接受两种条件下的扫描：脊髓麻醉组与对照组。脊髓麻醉可导致感觉丧失范围可达第6胸神经节段（Th6）。扫描过程中，通过箱式设计（即10秒刺激开启/25秒刺激关闭的块设计）对受试者右前臂（C8-Th1皮区）施加校准后的热痛刺激。每轮实验开始与结束时，采用视觉模拟评分法（visual analogue scale，1~100分）评估疼痛感知情况。采用广义估计方程分析干预方式、时间顺序对疼痛评分的影响。此外，采用适配的一般线性模型（控制受试者在实验轮次与时间点内的组内变异）检验更高层级的效应，以探究：（1）脊髓麻醉组与对照组在痛刺激下的血氧水平依赖（blood oxygen level dependent，BOLD）反应差异；（2）脊髓麻醉对脑激活的疼痛相关调控效应。
结果：本研究最终获得18名受试者的完整功能磁共振成像数据。脊髓麻醉组的疼痛评分呈现中等程度升高。对比脊髓麻醉组与对照组（麻醉后-麻醉前）的伤害性热刺激脑响应，可见显著差异。脊髓麻醉组受试者的双侧下顶叶血氧水平依赖信号显著升高，而双侧中央后回与中央前回的血氧水平依赖信号则显著降低。在角回区域内，疼痛评分与血氧水平依赖信号呈正相关。上述观测结果不受顺序效应（即脊髓麻醉实施于首次还是第二次访视）的影响。但我们仍观察到部分脑区存在显著的顺序效应，包括内侧前额叶皮层，这可能与脊髓麻醉体验的预期有关。
结论：脊髓麻醉引发的感觉与运动功能丧失，对参与伤害性热痛刺激的感觉运动与认知加工的脑区具有显著影响。本研究结果提示，对脊髓干预产生的强烈躯体感觉响应的预期或实际体验，可能会混淆认知疼痛加工过程，并加剧其敏感性。未来的研究需在实验框架内考虑疼痛感知主观体验的个体差异。