473: STEPS-TMD: Stress-Testing the Endogenous Pain System in Temporomandibular Disorders

Topic: Clinical Science
Subtopic: Pain category (ICD-11), Chronic primary orofacial pain, Assessment and Measurement of Pain/Nociception, Quantitative Sensory testing (static and dynamic, e.g., HPT, PPT, CPM, TSP, offset analgesia)

Background and Aims: Chronic pain affects one in five adults and remains difficult to assess mechanistically in clinical practice. Conditioned Pain Modulation (CPM) is the most common method for evaluating endogenous pain inhibition, yet it typically relies on a single trial that may not capture dynamic changes in inhibitory function. This study aims to introduce and evaluate a repeated “stress-test” CPM approach in patients with temporomandibular disorders (TMD). By assessing inhibitory responses across multiple consecutive trials, we aim to characterize individual inhibitory resilience profiles and determine whether this approach provides more reliable and clinically meaningful information than conventional single-trial CPM.

Methods: In this experimental study, patients diagnosed with myofascial orofacial pain will undergo repeated CPM assessments within a single session. A standardized test stimulus will be applied before and during a conditioning stimulus across multiple consecutive trials to repeatedly activate endogenous inhibitory pathways. Rather than deriving a single CPM value, response trajectories across trials will be analyzed to identify patterns such as stable inhibition, progressive decline, or facilitation.

Results: We expect the repeated stress-test CPM paradigm to reveal distinct inhibitory response patterns among myofascial orofacial pain patients that are not detectable using a single-trial approach. Some individuals may demonstrate stable inhibitory capacity, whereas others may show diminishing or fluctuating responses across trials, reflecting reduced inhibitory resilience. We anticipate that these dynamic profiles will show meaningful associations with clinical pain characteristics and neurophysiological measures, providing insight into underlying pain modulation mechanisms. Compared to conventional CPM assessment, this approach is expected to demonstrate improved reliability and greater sensitivity to individual differences in endogenous pain regulation.

Conclusions: This study will evaluate a novel repeated-trial CPM “stress-test” paradigm in TMD patients to better characterize endogenous pain inhibition. By moving beyond a single summary value and capturing dynamic response patterns, this method may offer a more mechanistic and individualized assessment of inhibitory pain function. If successful, the approach could improve the identification of dysfunctional pain modulation in TMD and support the development of more targeted, mechanism-based pain management strategies.

References: Yong RJ, Mullins PM, Bhattacharyya N. Prevalence of chronic pain among adults in the United States. Pain 2022; 163: e328–e332.
Le Bars D, Dickenson AH, Besson J-M. Diffuse noxious inhibitory controls (DNIC). I. Effects on dorsal horn convergent neurones in the rat. Pain 1979; 6: 283–304.
Yarnitsky D. Conditioned pain modulation (the diffuse noxious inhibitory control-like effect): Its relevance for acute and chronic pain states. Curr Opin Anaesthesiol 2010; 23: 611–615.
Ferreira DMAO, Costa YM, Bonjardim LR, et al. Effects of acute mental stress on conditioned pain modulation in temporomandibular disorders patients and healthy individuals. Journal of Applied Oral Science; 29. Epub ahead of print 2021. DOI: 10.1590/1678-7757-2020-0952.
Moana-Filho EJ, Herrero Babiloni A. Endogenous pain modulation in chronic temporomandibular disorders: Derivation of pain modulation profiles and assessment of its relationship with clinical characteristics. J Oral Rehabil 2019; 46: 219–232.

Presenting Author: Fernando G. Exposto
Submitting Author: Fernando Exposto

Senior Author: Fernando G. Exposto

IASP 2026 Global Year theme of Neuropathic Pain: No