Psychophysiological responses to stress in patients with myofascial pain-dysfunction syndrome.

The hypothesis was tested that patients diagnosed with myofascial pain-dysfunction (MPD) syndrome display a stereotypic response to stress via increased activity in the facial muscles. Twenty MPD patients and 20 matched control subjects were seated and exposed to affectively neutral, then stressful, then affectively neutral film clips. During film viewing, heart rates and skin-conductance levels were recorded along with bilateral EMG activity from the frontalis, temporalis, and masseter muscles and unilateral EMG activity from the forearm extensor. While both groups showed facial EMG responses to the stressor, MPD patients showed lower heart-rate and skin-conductance responses to experimental stress than did normals and a differentially higher frontalis EMG response. MPD patients also showed higher resting EMG levels than did normals at four of six facial muscle sites.