BilateralWidespreadMechanicalPainSensitivityinWomenWithMyofascialTemporomandibularDisorder:EvidenceofImpairmentinCentralNociceptiveProcessing

Myofascial temporomandibular disorder (TMD) is a common condition affecting the jaw muscles and temporomandibular joint, with women being disproportionately affected. While local pain in the jaw region is well recognized, many patients with myofascial TMD report pain in multiple body areas beyond the trigeminal region. This has led researchers to suspect that central sensitization—an amplification of pain signals within the central nervous system—may play an important role in the condition. However, previous studies examining pressure-pain sensitivity in TMD patients have produced conflicting results, possibly due to small sample sizes, inclusion of patients with comorbid conditions like depression or fibromyalgia, or differences in patient selection.

Understanding whether widespread mechanical pain sensitivity exists in pure myofascial TMD, without confounding conditions, is crucial for developing appropriate management strategies that address the full scope of the disorder rather than just local symptoms.

The researchers recruited 20 women with myofascial TMD and 20 healthy matched control women. All TMD patients were diagnosed using standardized Research Diagnostic Criteria for TMD (RDC/TMD) and had experienced spontaneous masseter muscle pain for at least 6 months with an intensity of at least 3 out of 10 on a numerical pain rating scale. Importantly, the researchers carefully excluded patients with any comorbid conditions that could confound pain sensitivity measurements, including other TMD diagnoses, fibromyalgia, systemic diseases, previous whiplash injury, pregnancy, depression scores above 9 on the Beck Depression Inventory, or any primary headache diagnosis.

Using an electronic pressure algometer, the researchers measured pressure-pain thresholds (PPT)—the minimum pressure at which a sensation of pressure first becomes painful—at multiple sites bilaterally across the body. These sites included three trigeminal nerve branches (supra-orbital V1, infra-orbital V2, and mental V3 nerves), three peripheral nerve trunks in the arm (median C5, radial C6, and ulnar C7), the C5-C6 zygapophyseal joint in the neck, the lateral pole of the temporomandibular joint itself, and the tibialis anterior muscle in the lower leg. All measurements were performed by an investigator blinded to whether participants had TMD or were healthy controls. The study also examined correlations between PPT levels and clinical features including pain duration and intensity.

The results revealed dramatically lower pressure-pain thresholds in women with myofascial TMD compared to healthy controls at every single test location, and these differences were bilateral (present on both sides of the body). Specifically, PPTs were significantly decreased over the supra-orbital, infra-orbital, and mental nerves, the median, ulnar, and radial nerve trunks, the lateral pole of the TMJ, the C5-C6 zygapophyseal joint, and the tibialis anterior muscle (all sites: P < .001). The mean PPT values illustrate the magnitude of these differences: for example, at the tibialis anterior muscle, TMD patients had thresholds of approximately 374 kPa on the most painful side and 366 kPa on the contra-lateral side, compared to 758 kPa and 752 kPa in controls. At the TMJ lateral pole, TMD patients had thresholds around 120 kPa versus approximately 282 kPa in controls.

Crucially, there were no significant differences in the magnitude of PPT decreases between trigeminal and extratrigeminal test sites—the degree of sensitization was similar whether measured in the face, neck, arm, or leg. The PPT indices (relative decreases compared to controls) ranged from 47% to 52% across all sites. Additionally, PPT levels over the mental nerve, TMJ, C5-C6 zygapophyseal joint, and tibialis anterior muscle were negatively correlated with both duration of pain symptoms and TMD pain intensity (P < .05), meaning that longer symptom duration and higher pain intensity were associated with greater mechanical pain sensitivity.

These findings provide strong evidence that women with myofascial TMD exhibit widespread central sensitization, not merely localized peripheral sensitization in the jaw muscles. The bilateral and similar magnitude of pressure-pain hypersensitivity across both trigeminal and distant body regions suggests that the central nervous system is amplifying pain signals globally, rather than just at the site of initial injury or dysfunction. This has important clinical implications: treatments for myofascial TMD may need to address central pain processing mechanisms, not just local peripheral issues in the jaw. The correlation between longer symptom duration and greater widespread sensitivity also suggests that central sensitization may become more established over time, potentially making the condition more difficult to treat if not addressed early.

For patients, this means that pain felt in areas seemingly unrelated to the jaw—such as the neck, arms, or legs—may be genuinely connected to their TMD through shared central nervous system mechanisms, and should not be dismissed as unrelated or psychosomatic. Clinicians should consider evaluating and potentially treating widespread pain sensitivity, not just local jaw symptoms, when managing myofascial TMD.