Effects of acute mental stress on conditioned pain modulation in temporomandibular disorders patients and healthy individuals

Abstract Stress is a contributing factor to painful temporomandibular disorders (TMD). Nevertheless, the underpinnings of this relationship are not fully understood. Objective To investigate the effects of acute mental stress on conditioned pain modulation (CPM) in TMD patients compared with healthy individuals. Methodology Twenty women with chronic myofascial TMD diagnosed according to the RDC/TMD and 20 age-matched healthy women had the CPM assessed before and after a stressful task using the Paced Auditory Serial Addition Task (PASAT) in a single session. Subjective stress response was assessed with the aid of visual analog scale (VAS). Pressure pain threshold (PPT) on masseter muscle was the test stimulus (TS) and immersion of the participant’s hand on hot water was the conditioning stimulus (CS) - CPM-sequential paradigm. Results Healthy individuals reported PASAT are more stressful when compared with TMD patients and the stress task did not affect the CPM in neither group. Nonetheless, a negative correlation was observed between change in CPM and change in TS from baseline to post-stress session, which indicates that the greater the increase in PPT after the stress task, the greater was the decrease in CPM magnitude. The correlation was strong for healthy controls (r=- 0.72, p<0.001) and moderate for TMD patients (r=- 0.44, p=0.047). Conclusions The correlation between the change in CPM and the TS change following the stress task may possibly indicate an overlapping pathway between stress-induced analgesia/hyperalgesia and descending pain inhibition.

摘要：心理应激是疼痛性颞下颌关节紊乱病（Temporomandibular Disorders, TMD）的诱因之一，但二者间关联的病理生理学机制尚未完全阐明。
研究目的：旨在探究急性心理应激对TMD患者与健康人群的条件性疼痛调节（Conditioned Pain Modulation, CPM）的影响差异。
研究方法：本研究纳入20名符合RDC/TMD诊断标准的慢性肌筋膜型TMD女性患者，以及20名年龄匹配的健康女性。在单次实验中，于序列听觉加法测试（Paced Auditory Serial Addition Task, PASAT）这一应激任务前后，分别评估受试者的CPM水平；采用视觉模拟评分法（Visual Analog Scale, VAS）评估主观应激反应。本实验采用CPM序列范式：以咬肌压力痛阈（Pressure Pain Threshold, PPT）作为测试刺激（Test Stimulus, TS），以受试者手部热水浸泡作为条件刺激（Conditioning Stimulus, CS）。
研究结果：相较于TMD患者，健康人群认为PASAT任务的应激程度更高；且应激任务对两组受试者的CPM水平均无显著影响。然而，在基线至应激后阶段的CPM变化量与TS变化量之间观察到负相关关系，即应激任务后PPT升高幅度越大，CPM强度的下降幅度就越大。其中健康对照组的相关程度较强（r=-0.72，p<0.001），TMD患者组的相关程度中等（r=-0.44，p=0.047）。
研究结论：应激任务后CPM变化量与TS变化量之间的相关关系，或提示应激诱导的镇痛/痛觉过敏与下行性疼痛抑制存在共同的作用通路。