OBJECTIVETo evaluate and analysis facial somatosensory changes of patients with chronic masticatory muscle pain (MMP) quantitatively.

METHODSThe seven parameters of standardized quantitative sensory testing (QST) protocol were used to test the pain sites, contralateral sites of masticatory muscles of 20 chronic MMP patients and the same sites of right masticatory muscles of 20 matched healthy controls. QST thresholds were compared within groups using paired t test and between groups using unpaired t test.

RESULTSCompared to the controls, all seven parameters of bilateral sides of patients had changed. Mainly cold detection thresholds [(-1.2±0.5) and (-1.7±0.9) °C] and cold pain thresholds [(27.6±2.3) and (27.0±2.0) °C] of pain and contralateral sides increased significantly, while warm detection thresholds [(2.0±1.1) and (2.1±1.2) °C], heat pain thresholds [(37.9±3.2) and (39.7±3.9) °C], and mechanical pain thresholds [(49.3±34.1) and (111.8±86.3) mN] of pain and contralateral sides decreased significantly (P<0.05). Mechanical detection thresholds of pain sites [(1.8±1.4) mN] significantly increased (P=0.01).

CONCLUSIONSChronic MMP patients were detected thermal hyperesthesia, thermal hyperalgesia, and mechanical hyperalgesia. Mechanical hypoesthesia was found at the pain sites of masticatory muscles. Chronic MMP might influence the central modulation of trigeminal nerve system.