Temporal Summation of Heat Pain in Temporomandibular Disorder Patients

Aims: To compare patients with temporomandibular disorders (TMD) to control subjects on two measures of central processing, ie, temporal summation of heat pain and decay of subsequent aftersensations, following thermal stimulation in both a trigeminal and extratrigeminal area. Methods: A "wind-up" protocol was used in which 19 female TMD patients and 17 female controls were exposed to 15 heat stimuli at a rate of 0.3 Hz. Numeric pain ratings were elicited after the 1st, 5th, 10th, and 15th stimulus presentation and every 15 seconds after final presentation (aftersensations) for up to 2 minutes. In separate trials, the thermode was placed on the thenar eminence of the hand and the skin overlying the masseter muscle. Results: Groups did not differ with respect to the slope of wind-up when stimulated at either anatomic site, although asymptotic levels occurred sooner for TMD patients than for controls. In analysis of aftersensations, a significant group x site x time interaction was detected, in which TMD patients experienced more prolonged painful aftersensations than controls when stimulated on the skin overlying the masseter muscles. Conclusion: These results are consistent with the presence of enhanced central sensitivity in TMD and suggest that this sensitivity may be largely confined to the region of clinical pain. This contrasts with conditions such as fibromyalgia, where central sensitivity appears to be widespread. Keywords: aftersensations, chronic pain, temporal summation, temporomandibular disorders, wind-up