OBJECTIVETo evaluate trigeminal function of patients with chronic masticatory muscle pain (MMP) using trigeminal somatosensory evoked potential (TSEP) and analyze mechanism of changes compared to the controls.

METHODSTwelve chronic MMP patients and 12 matched controls participated in this study. TSEPs of bilateral masseter regions and inferior alveolar nerves were measured and compared between patient and control groups. The collected waves were concluded and those with appearance rate over 75% - 100% were selected. The latencies of waves were analyzed by use of the paired t test and independent-samples t test.

RESULTSFive stable-appearing waves were obtained and named P1, N1, P2, N2, P3. The latency of P1 was significant reduced in patients (P < 0.05). The latencies of other waves were prolonged, but only P2 and N2 in left were significantly changed (P < 0.05).

CONCLUSIONSTSEP latencies of chronic MMP patients changed in certain regular pattern and TSEP could be used as a parameter to disclose the trigeminal system abnormalities of the patients. The reduced latency of P1 might indicate the increasing conductivity of trigeminal nerves under level of ganglion Gasseri and the prolongation of latency of P2 was possibly related to inhibitory effects of the brain stem.