Enhanced pain facilitation rather than impaired pain inhibition in burning mouth syndrome female patients.

Background: Deficient endogenous pain modulation has been implicated in the development and exacerbation of chronic orofacial pain. To date, relatively little is known regarding the function of the endogenous pain modulation in patients with burning mouth syndrome (BMS). This case-control study investigated endogenous pain modulation in women with BMS.

Methods: Conditioned pain modulation (CPM) was assessed upon temporal summation (TSP) of thermal pain. Forty female subjects, 20 BMS patients and 20 age-matched control subjects, were included in a 2 session-protocol. Mechanical and thermal pain thresholds were measured on the forearm and hand. TSP was obtained using repetitive laser-evoked thermal stimuli applied on the non-dominant hand, at an intensity yielding to moderate pain. During TSP, CPM was produced by immersing the contralateral foot in a water bath at painful cold (8 °C) temperature. In control conditions, the foot was immersed in a water bath at not painful (30 °C) temperature.

Results: BMS was not associated with any impairment in thermal as well as mechanical extracephalic pain thresholds. TSP and CPM efficacy were similar in BMS patients and control subjects. However, BMS patients exhibited enhanced extracephalic heat hyperalgesia.

Conclusion: This study reveals that there is no impairment of endogenous pain inhibition mechanisms in BMS patients, but rather an increase in pain facilitation.