Enhanced negative feedback sensitivity of the hypothalamus-pituitary-adrenal axis in chronic myogenous facial pain

Dysregulations of the hypothalamus-pituitary-adrenal (HPA) axis, as a physiological substrate of stress, have been observed in patients with different stress-related and chronic pain disorders. In this study, we investigated possible dysregulations of the HPA axis in patients with masticatory muscles pain. In 20 patients with myogenous facial pain and 20 healthy controls, awakening cortisol responses, i.e.cortisol rise in the first hour after awakening, as well as a short circadian free cortisol profile, i.e. four cortisol samples over 12h during the day, were assessed before and after administration of 0.5mg dexamethasone. Results: In comparison to controls, chronic myogenous facial pain patients showed enhanced and prolonged suppression of cortisol after the administration of 0.5mg dexamethasone. Unstimulated cortisol response (before dexamethasone-intake) to awakening and cortisol levels during the day did not differ between the groups. Dysregulation in terms of enhanced negative feedback suppression exists in chronic myogenous facial pain. These results are in line with a multifactorial etiology of chronic facial pain, shifting the perspective away from a local towards a more central etiology with dysregulations in the stress and pain modulating system.