Experimental jaw muscle pain increases pain scores and jaw movement variability in higher pain catastrophizers

Aims: Catastrophic interpretations of pain are associated with amplified pain experience but little is known about effects on movement. The aim is to investigate differences between higher and lower pain catastrophizers in 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 (age 25 to 62 yrs; 20 male, 8 female) during continuous infusion of 5% hypertonic saline (HS) into right masseter muscle or 0.9% isotonic saline infusion (IS). All participants completed the McGill Pain Questionnaire (MPQ), the Depression, Anxiety and Stress Scales, The Jaw Function Limitation Scale and were divided by the median Pain Catastrophizing Scale (PCS) score. Statistical analyses involved MANOVA, independent samples or paired t-tests, and Pearson correlations (statistical a:P <0.05). Results: Pain intensity, unpleasantness, perceived area, and pain rating indices were significantly (P<0.05) elevated in higher pain catastrophizers during HS in comparison with lower catastrophizers. The higher catastrophizers exhibited significantly (P<0.05) slower jaw velocity than the lower catastrophizers during hypertonic saline in comparison with isotonic saline infusion. In comparison with lower catastrophizers, there was a significantly greater change (HS-IS) in the percentage of coefficient of variation between hypertonic and isotonic 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 behaviour for the jaw motor system.