Pressure pain threshold alterations in chronic painful temporomandibular myalgia disorsders: a systematic review and meta-analysis.

ABSTRACT Objectives: This meta-analysis aimed to evaluate difference in Pressure Pain Threshold (PPT) for chronic temporomandibular myalgia (TMDm) subjects without comorbidities compare to healthy control in different area of the body. Methods: We searched five electronic databases for studies with particular attention paid to including only chronic temporomandibular myalgia (TMDm) without mixed diagnosis. When data was available, a meta-analysis was performed based on the place of assessment of PPT. The four sections are trigeminal area (masseter and/or temporal), cervical region and the upper and lower limb. Risk of bias was assessed with the SIGN case-control study checklist. Statistical heterogeneity was estimated with Chi² test and inconsistency index, I². Results: 10 studies are included in this review comprising 290 chronic myofascial TMD and 255 healthy controls. We found lower values of PPT for the TMD group in the four assessed areas with an overall effect (Z = 8.14; 𝒑 < .00001) for the trigeminal region; (Z = 8.01; 𝒑 < 0.00001) for the cervical area; (Z = 2.03; 𝒑 = 0.04) in the upper limb and (Z = 2.82; 𝒑 = 0.005) in the lower limb. Risk of bias was presented as high for 6 studies, moderate for 3 and low for 1. Discussion : The results of the study indicate that TMDm subjects present a hypersensitivity to pressure at the trigeminal and extra-trigeminal level. We compare our results to other assessments of the somatosensory system in TMDm and some chronic diseases. These comparisons highlight the singularity and complexity of the mechanisms involved for TMDm and show the importance of distinguishing them from other TMD populations. Conclusion: The study results suggest that there is an altered pain sensitivity in chronic TMDm subjects in trigeminal as both as extra-trigeminal region. More studies should be carried out in these specific patients with better respected methodological guidelines and better standardised PPT protocols.