487: Repeated Conditioned Pain Modulation Across Regions in Women With Myofascial Pain and Comorbidities

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

Background and Aims: Conditioned pain modulation (CPM) is widely used to assess descending inhibitory function, yet its clinical interpretation remains limited by high interindividual variability and inconsistent group differences in chronic pain. Evidence suggests that single-trial protocols and restricted assessment sites may underestimate subtle changes in inhibitory capacity. Repeated CPM testing across anatomical regions may improve sensitivity, particularly in heterogeneous conditions such as painful temporomandibular disorders (TMD) associated with comorbidities. This study aimed to compare CPM responses across repeated trials in asymptomatic women and in those with myalgia/myofascial pain, with trigeminal and extratrigeminal comorbidities, exploring differences between anatomical regions and clinical groups.

Methods: This cross-sectional study included 128 women with and without myalgia and/or myofascial pain for >3 months, occurring 1–14 days/month, allocated into four groups (n=32 each): asymptomatic controls; myalgia/myofascial pain only; myalgia/myofascial pain with trigeminal comorbidity; and myalgia/myofascial pain with extratrigeminal comorbidity. CPM was assessed using pressure pain threshold as the test stimulus and cold water immersion as the conditioning stimulus, applied over three consecutive series in trigeminal (masseter muscle) and extratrigeminal (thenar eminence) areas. CPM variation across repetitions was compared between groups and areas.

Results: In the trigeminal region, repeated-measures ANOVA showed a significant group effect (F(3,124)=8.36, p<0.001, ηp²=0.136), with no repetition or interaction effects. Control and TMD group without comorbidities showed more inhibitory CPM than trigeminal (p≤0.008) and extratrigeminal comorbidity groups (p≤0.002). In the extratrigeminal region, a small repetition effect was observed (F(2,248)=3.19, p=0.043, ηp²=0.006), with reduced inhibition from the second to third repetition (p=0.037), and no group effect. Overall, CPM was more inhibitory in the trigeminal than extratrigeminal area (F(1,124)=4.89, p=0.029), with a significant area × repetition interaction (F(2,248)=3.78, p=0.024).

Conclusions: This study is the first to examine CPM behavior across repeated series in women with myalgia/myofascial pain, with and without painful comorbidities, exploring waning effects across anatomical regions. CPM modulation differed across groups and stimulation sites, with preserved inhibition in controls and in TMD without comorbidities, and weaker inhibitory responses in comorbidity groups, particularly in the trigeminal region. Extratrigeminal CPM showed a small reduction across repetitions. These findings indicate that CPM is not a static measure, varying with comorbidity status, stimulation site, and repeated testing, supporting its use as a complementary rather than isolated tool in orofacial pain assessment.

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Presenting Author: Maria Emilia Servin Berden
Submitting Author: Maria Emilia Servin Berden

Senior Author: Paulo César Rodrigues Conti

IASP 2026 Global Year theme of Neuropathic Pain: No

• Rafaela Stocker Salbego: PhD - University of São Paulo
• Samilla Pontes Braga: PhD - University of São Paulo
• Carolina Ortigosa Cunha: PhD - Sacred Heart University (UNISAGRADO)
• Leonardo Rigoldi Bonjardim: PhD - University of São Paulo
• Fernando G. Exposto: PhD - Aarhus University
• Paulo César Rodrigues Conti: PhD - University of São Paulo