Objectives: To use pressure-pain testing (ppt) and functional magnetic resonance imaging (fMRI) to test the hypothesis that central pain processing is augmented in TMD patients.
Methods: Carefully-selected (TMD Research Diagnostic Criteria) right-handed TMD (myalgia, N=10) and matched control subjects (N=10) underwent multiple random staircase ppt applied to the left thumb and left anterior temporalis muscle. Subjects rated their pain with a Gracely box scale (GBS). Pressures for which each subject reliably reported 15/20 on a GBS (equal-pain) were recorded. FMRI scanning (BOLD, 3T GE Sigma scanner) was performed while subjects underwent 30 randomized 10-s periods of pressure ‘off' (rest), equal-pressure ‘on' (2-kg), and equal-pain ‘on' (15/20 GBS). Testing was performed first on the thumb and then on the temporalis muscle. Images were warped, smoothed, normalized and analyzed (SPM2) to test for between-group differences during equal-pressure and equal-pain conditions separately.
RESULTS: For equal-pressure applied to the temporalis muscle, TMD subjects showed significantly higher activation of six sites including the ipsilateral superior temporal gyrus and insula. For equal-pain testing to the temporalis muscle, no significant differences were observed between the two subject groups.
CONCLUSION: These results corrobrate previous results demonstrating hyperalgesia in the facial region in TMD and are the first to use fMRI to identify brain regions associated with this hyperalgesia. This project was supported by NIDCR grant DE018528.