SENSITIVITY OF PATIENTS WITH PAINFUL TEMPOROMANDIBULAR DISORDERS TO EXPERIMENTALLY EVOKED PAIN - EVIDENCE FOR ALTERED TEMPORAL SUMMATION OFPAIN

Temporomandibular disorders (TMD) represent a group of chronic painful conditions involving the muscles of mastication and the temporomandib ular joint. Several studies have reported that TMD is associated with enhanced sensitivity to experimental pain. Twenty three TMD subjects a nd 24 pain-free matched control subjects participated in a set of stud ies which were designed to evaluate whether the temporal integrative a spects of thermal pain perception are altered in TMD patients compared with control subjects. Specifically, we have examined in both TMD pat ients and in age- and gender matched control subjects: (1) the time-co urse and magnitude of perceived pain evoked by the application of sust ained 7-s noxious thermal stimuli (45-48 degrees C) to the face and fo rearm, (2) the central summation of C-fiber mediated pain produced by applying brief trains of noxious heat pulses to the skin overlying the ventral aspect of the right palm and (3) the ability to discriminate small increments in noxious heat applied to facial and volar forearm s kin. Data collected from these studies indicate that TMD patients show enhanced temporal integration of thermal pain compared with control s ubjects. TMD patients show greater thermal C-fiber-mediated temporal s ummation than pain-free subjects and they report a greater magnitude o f sustained noxious heat pulses applied to either the face or the fore arm than control subjects. In contrast to these findings, TMD and pain -free subjects are equally able to discriminate and detect small incre ments of heat applied to noxious adapting temperatures. These findings suggest that the augmented temporal integration of noxious stimuli ma y result from alterations in central nervous system processes which co ntribute to the enhanced pain sensitivity observed in TMD patients. (C ) 1998 International Association for the Study of Pain. Published by E lsevier Science B.V.