Experimental Jaw Muscle Pain Increases Pain Scores and Jaw Movement Variability in Higher Pain Catastrophizers

Aims: To investigate differences between higher and lower pain catastrophizers in the effects of hypertonic saline-evoked jaw muscle pain on pain perception and jaw movement. Methods: Repetitive open/close jaw movements were recorded in 28 asymptomatic participants (20 men, 8 women; ages 25 to 62 years) during continuous infusion of 5% hypertonic saline or isotonic saline into the right masseter muscle. All participants completed the McGill Pain Questionnaire; the Depression, Anxiety and Stress Scales; and the Jaw Function Limitation Scale. They were divided into two groups depending on the median Pain Catastrophizing Scale score. Statistical analyses involved multivariate analysis of variance, independent samples or paired t tests, and Pearson correlations (statistical α: P .05). Results: Pain intensity, unpleasantness, perceived area, and pain rating indices were significantly (P .05) elevated in higher pain catastrophizers during hypertonic saline-evoked pain in comparison with lower catastrophizers. The higher catastrophizers exhibited significantly (P .05) slower jaw velocity than the lower catastrophizers during hypertonic saline infusion in comparison with IS infusion. In comparison with lower catastrophizers, there was a significantly greater change in the percentage of coefficient of variation between hypertonic saline and isotonic saline infusions in higher catastrophizers for closing velocity and opening and closing amplitude. Conclusion: The increased reported pain intensity, pain areas, and pain rating indices are consistent with enhanced central sensitization processes in high-catastrophizing individuals. The slower velocity and greater variability of repetitive jaw movements in higher pain catastrophizing individuals in acute experimental pain may reflect changes in motor coordination as an example of avoidance behavior for the jaw motor system. Keywords: jaw movement, orofacial pain, Pain Adaptation Model, pain catastrophizing, pain intensity