Examining Laterality in Masticatory Myofascial Pain

Objective: To characterize unilateral and bilateral masticatory myofascial pain (MMP) in a clinical cohort. Materials and Methods: Patients meeting criteria for MMP according to the Research Diagnostic Criteria for Temporomandibular Disorders were recruited over a 2-year period. Demographic and clinical date were recorded. Data for unilateral and bilateral pain were analysed using Mann–Whitney U, Kruskal–Wallis H, and Fisher's Exact tests. Variables showing a p < 0.2 were entered into a binary logistic regression model, with pain laterality as the dependent variable. Results: Patients with unilateral pain exhibited muscle tenderness both ipsilaterally and bilaterally, and patients with bilateral pain likewise demonstrated tenderness bilaterally and unilaterally. Unilateral pain was significantly associated with pain-related awakening (p = 0.03), nausea (p = 0.01), and primary pain (p = 0.01). These associations were confirmed in the regression analysis. Patients with unilateral and bilateral pain were similar in demographic characteristics. Conclusions: Unilateral and bilateral masticatory muscle pain differ in three clinical domains. Unilateral pain is significantly associated with pain-related awakening, primary pain, and nausea. The significance of these findings needs further study in a larger cohort. Additionally, the potential relationship between unilateral/bilateral MMP and headache warrants further investigation.