Temporal Summation and Aftersensations of Second Pain in Women with Myofascial Temporomandibular Disorder Differ by Presence of Temporomandibular Joint Pain

PURPOSE: Mechanisms underlying myofascial temporomandibular disorder (mTMD) are poorly understood. One theory is dysfunction in the central mediation of pain, specifically in enhanced facilitatory pain modulation. Because mechanisms leading to central sensitization may differ for joint and muscle pain, this study of mTMD addressed phenotypic heterogeneity by temporomandibular (TM) joint pain in the examination of quantitative sensory testing (QST). PATIENTS AND METHODS: The stimulus dependent increase in second pain (temporal summation (TS)) and associated aftersensations (AS) were examined across groups of women with mTMD with TM joint pain and without, and a demographically matched control group. RESULTS: TS was slightly more evident in mTMD without joint pain vs with (p = 0.035), but AS were most robustly persistent in the group with joint pain vs without (p < 0.002). CONCLUSION: While both subgroups demonstrated evidence of central sensitization relative to controls on one of two measures, differences in QST results, if replicated, may point to possible differences in the mechanisms that yield central sensitization. Alternatively, it may represent methodological artifacts that need to be addressed. Therefore, greater consideration should be given to symptom-based phenotypes in studies examining TS and AS.