Faculty Bibliography

This report presents the findings from a psychophysical study of vibrotactile responses in a patient diagnosed with temporomandibular disorder (TMD). This patient unexpectedly reported pain due to innocuous vibrotactile stimulation, and this allodynia appeared to have a component of temporal summation. The pain response occurred not only in the region of the clinical pain (the face), but also on the volar forearm, where the patient reported no clinical pain. Administration of the N-methyl-D-aspartate (NMDA) receptor antagonist dextromethorphan (DM), but not vehicle, attenuated the vibration-induced pain at both sites.

Temporomandibular disorders (TMD) represent a group of chronic painful conditions involving the muscles of mastication and the temporomandibular joint. Several studies have reported that TMD is associated with enhanced sensitivity to experimental pain. Twenty-three TMD subjects and 24 pain-free matched control subjects participated in a set of studies which were designed to evaluate whether the temporal integrative aspects of thermal pain perception are altered in TMD patients compared with control subjects. Specifically, we have examined in both TMD patients and in age- and gender-matched control subjects: (1) the time-course and magnitude of perceived pain evoked by the application of sustained 7-s noxious thermal stimuli (45-48 degrees C) to the face and forearm, (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 skin. Data collected from these studies indicate that TMD patients show enhanced temporal integration of thermal pain compared with control subjects. TMD patients show greater thermal C-fiber-mediated temporal summation than pain-free subjects and they report a greater magnitude of sustained noxious heat pulses applied to either the face or the forearm than control subjects. In contrast to these findings, TMD and pain-free subjects are equally able to discriminate and detect small increments of heat applied to noxious adapting temperatures. These findings suggest that the augmented temporal integration of noxious stimuli may result from alterations in central nervous system processes which contribute to the enhanced pain sensitivity observed in TMD patients.

The purpose of this study was to determine whether the elevation in vibrotactile detection threshold, found in many individuals with temporomandibular disorders (TMD), is paralleled by suprathreshold impairments. Participants with TMD were compared with pain-free control subjects in their ability to discriminate on the basis of differences in amplitude and frequency between vibratory stimuli delivered to the face. The TMD group was significantly impaired with respect to frequency discrimination, but not amplitude discrimination. This dissociation suggests that the cortical processing of vibrotactile signals may be affected in TMD patients. TMD participants' estimates of the intensity of their spontaneous and palpation-evoked pain did not significantly correlate with performance on either discrimination task; this finding makes it unlikely that impaired vibrotaction in TMD is primarily the result of a pain-dependent gating of tactile signals.

OBJECTIVE: Patients experiencing temporomandibular disorders (TMD) show greater sensitivity to painful stimuli than age- and gender-matched control subjects. This enhanced pain sensitivity may result, at least in part, from an alteration in pain regulatory systems that are influenced by resting arterial blood pressure. In this study, we examined the relationship between resting systolic blood pressure and pain perception in 64 female TMD and 23 age-matched pain-free female subjects. METHOD: Resting arterial blood pressure and measures of thermal and ischemic pain threshold and tolerance were determined for each participant. Subjective ratings of thermal pain evoked by suprathreshold noxious thermal stimuli (45-49 degrees C) using a magnitude matching procedure were also obtained for both groups. RESULTS: TMD patients had lower thermal and ischemic pain thresholds and tolerances than pain-free subjects (ps < .05). Both groups provided equivalent intensity ratings to suprathreshold noxious thermal stimuli. A median split of each group based on resting systolic blood pressure revealed an influence of blood pressure on both thermal and ischemic pain perception for the Pain-Free group. The Pain-Free high resting blood pressure subgroup had higher thermal pain tolerances, higher ischemic pain thresholds, and provided lower magnitude estimates of the intensity of graded heat pulses compared with the Pain-Free low blood pressure subgroup. A trend toward a significant effect of blood pressure level on ischemic pain tolerance was also observed for the Pain-Free group. In contrast to the Pain-Free group, blood pressure level did not influence ischemic or thermal pain perception for TMD patients. Similar to the lack of effect of resting blood pressure on experimental pain perception in TMD patients, resting blood pressure was not related to measures of clinical orofacial pain in TMD patients. CONCLUSIONS: These findings confirm our previous findings that TMD patients are more sensitive to noxious stimuli and suggest that painful TMD may result, at least in part, from an impairment in central pain regulatory systems that are influenced by resting arterial blood pressure.

Recent evidence suggests that a past history of physical and/or sexual abuse is more frequently reported among chronic pain populations; however, the prevalence of reported abuse has not been examined in patients with chronic orofacial pain caused by temporomandibular disorders (TMD). This study compares reported physical/sexual abuse among female TMD subjects recruited from the general population with that of age-matched female control subjects. The association of reported abuse with clinical pain, experimental pain responses, and psychologic variables was examined in the TMD group. Results indicated that a slightly but not statistically greater percentage of TMD subjects (44.8%) reported a history of sexual or physical abuse compared to control subjects (33.3%). Reported abuse among TMD subjects was not related to clinical pain or psychologic variables. Regarding experimental pain responses, TMD subjects reporting a history of abuse exhibited longer ischemic pain tolerances compared to those not reporting abuse; however, the groups did not differ on other experimental pain measures. Results indicate that the reported prevalence of physical/sexual abuse is similar among TMD subjects compared to other chronic pain populations; however, the relationship of abuse to clinical and psychosocial variables remains unclear.