Examination of Conditioned Pain Modulation in Myofascial TMD With Consideration of Temporal Summation

• Published in: The journal of pain Vol. 25; no. 5; p. 104430
• Main Authors: Santiago, Vivian, Janal, Malvin N., Cook, Dane B., Raphael, Karen G.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.05.2024
• Subjects: Adult; Conditioned pain modulation; Conditioning, Psychological - physiology; Endogenous pain modulation; Female; Humans; Middle Aged; Myofascial pain; Pain Measurement; Pain Threshold - physiology; Temporal summation of second pain; Temporomandibular disorder; Temporomandibular Joint Disorders - physiopathology; Temporomandibular Joint Dysfunction Syndrome - physiopathology; Young Adult; Myofascial pain; Temporal summation of second pain; Endogenous pain modulation; Conditioned pain modulation; Temporomandibular disorder
• ISSN: 1526-5900; 1528-8447
• DOI: 10.1016/j.jpain.2023.11.013

Research on myofascial temporomandibular disorder (mTMD) has often focused on potential dysfunction in endogenous pain modulation. However, studies on the specific inhibitory and facilitatory components of endogenous pain modulation using conditioned pain modulation (CPM) and temporal summation of second pain (TSSP) have shown mixed results. This study aimed to 1) examine whether women with mTMD demonstrated efficient CPM compared to controls; 2) explore the association between independent measures of CPM and TSSP in women with mTMD relative to controls; and 3) determine whether resulting modulatory profiles differentially predicted pain intensity among cases. All participants were recruited from dental clinics. Cases were women who met the research diagnostic criteria for mTMD. Controls did not have facial pain on exam and were selected to be sociodemographically similar to cases. CPM and TSSP were assessed via independent psychophysical protocols. CPM was examined in linear mixed models predicting pain thresholds adjusted for age and stratified by TSSP. Mean CPM was estimated at a 2.2 (SD = 2.8) degree increase in pain thresholds (P ≤ .001), similar in cases and controls (P = .67). CPM was less efficient in cases with enhanced TSSP (P = .031), but not in controls. Although the double-pronociceptive profile of both low CPM and high TSSP trended higher among cases than controls, it did not predict higher levels of pain intensity among cases. This study does not support deficient inhibitory endogenous pain modulation in mTMD, but results suggest that inhibitory and facilitatory pain modulation should be examined concomitantly in the study of endogenous pain modulation. This manuscript presents a novel examination of inhibitory modulation by the level of facilitatory modulation in mTMD. The findings and approach may prove useful for mechanistic researchers studying endogenous pain modulation and clinical researchers seeking to jointly examine conditioned pain modulation and temporal summation in future research on chronic pain. •Few studies examine inhibitory pain modulation by levels of facilitatory pain modulation.•Our study found CPM in women with mTMD was comparable to that of control women.•However, in mTMD, CPM was less efficient when TSSP was enhanced.•The double pronociceptive profile was higher in women with mTMD than controls.•Joint consideration of inhibitory and facilitatory modulation may provide mechanistic insights.