Thermal temporal summation and decay of after-sensations in temporomandibular myofascial pain patients with and without comorbid fibromyalgia

INTRODUCTION: Chronic myofascial temporomandibular disorders (TMD) may have multiple etiological and maintenance factors. One potential factor, central pain sensitization, was quantified here as the response to the temporal summation (TS) paradigm, and that response was compared between case and control groups. OBJECTIVES: As previous research has shown that fibromyalgia (FM) is diagnosed iñ20% of TMD patients, Aim 1 determined whether central sensitization is found preferentially in myofascial TMD cases that have orofacial pain as a regional manifestation of FM. Aim 2 determined if the report of after-sensations (AS) following TS varied depending on whether repeated stimuli were rated as increasingly painful. METHODS: One hundred sixty-eight women, 43 controls, 100 myofascial TMD-only cases, and 25 myofascial TMD + FM cases, were compared on thermal warmth and pain thresholds, thermal TS, and decay of thermal AS. All cases met Research Diagnostic Criteria for TMD; comorbid cases also met the 1990 American College of Rheumatology criteria for FM. RESULTS: Pain thresholds and TS were similar in all groups. When TS was achieved (~60%), significantly higher levels of AS were reported in the first poststimulus interval, and AS decayed more slowly over time, in myofascial TMD cases than controls. By contrast, groups showed similar AS decay patterns following steady state or decreasing responses to repetitive stimulation. CONCLUSION: In this case–control study, all myofascial TMD cases were characterized by a similar delay in the decay of AS. Thus, this indicator of central sensitization failed to suggest different pain maintenance factors in myofascial TMD cases with and without FM.