To evaluate changes in bilateral masseter and temporalis EMG activity among myofascial pain patients in response to experimental stressors, and to determine the relation between EMG changes and patients' characteristic (“trait”) anxiety levels and muscle pain on palpation.
Methods:
Data will be drawn from an in-progress study designed to test popular beliefs about the etiology of myofascial face pain. Participants meet criteria for the myofasical subtype of temporomandibular disorder (TMD) according to Research Diagnostic Criteria (RDC) examination. Muscle activity increases are assessed in terms of increases in baseline electromyography (EMG) levels when participants are exposed to a series of four stressful experimental tasks (speech preparation, serial subtraction, startle response, cold pressor). Following the testing session, EMG artifacts due to movement, talking or other behaviors are removed. Patients' baseline anxiety levels are measured by a widely used State-Trait Anxiety Inventory (STAI) questionnaire. Pain on palpation is assessed using RDC diagnostic examination methods.
Results:
Preliminary analyses on a subset of these subjects (n=8) suggest that myofascial face pain patients with high trait anxiety have higher baseline EMG activity, creating a ceiling effect so that smaller increases are detected in response to stress when compared to patients with low trait anxiety.
Conclusion:
Early evaluation of enrolled subjects demonstrated higher baseline EMG activity in patients with higher anxiety (STAI) score, and smaller increases in EMG activity following experimental stress (ceiling effect). We will present findings from a similar analysis on a larger group (n=30) and extend our analysis to include correlations between STAI score, baseline and stress-related changes in EMG muscle activity and sites of muscle palpation pain. (Supported by NIH/NIDCR R01DE018569)