Journal of Oral & Facial Pain and Headache, 04/1994

Two temporomandibular joints from one specimen were investigated using magnetic resonance imaging and cryosectioning. Magnetic resonance images, photography of the tissue block surface, and on-tape histologic sections were compared. The left joint was imaged and sectioned in a coronal plane, and the right joint in an angulated coronal plane parallel to the long axis of the condyle. The temporomandibular joint disc could be seen in coronal and angulated coronal scans. The posterior band was imaged in angulated coronal magnetic resonance scans throughout the temporomandibular joint both medically and laterally. In coronal scans only parts of the disc proper could be seen, depending on the level of imaging or sectioning. The densely plaited fibrous tissue of the intra-articular tissues could be seen in magnetic resonance imaging, primarily anterior to the condyle; this tissue corresponded to the low signal intensity in magnetic resonance imaging. Medical and lateral disc attachments as well as the temporomandibular joint capsule were imaged in some of the magnetic resonance scans in both the coronal and the angulated coronal scans. In diagnosing anteromedial, medial, and lateral disc displacements, angulated coronal temporomandibular joint scanning is preferred over coronal scanning.

Although it has been suggested that bruxism is a cause or a risk factor in myofascial pain of the masticatory muscles, the prevalence of pain in bruxers and its characteristics have not been assessed or compared to those of myofascial pain patients in general. In this study, self-reports of pain and quality of life were recorded on 100-mm visual analogue and five-point category scales from two research populations: (1) 19 nocturnal bruxers who participated in a polysomnographic study and (2) 61 patients with myofascial pain of the masticatory muscles with no evidence of bruxism who participated in a controlled clinical trial on the efficacy of oral splints. The data show that pain was more intense in those bruxers who reported pain than among the myofascial pain patients, even though pain was not the chief complaint of bruxers. Both conditions reduced the patient's quality of life, although pain patients (either bruxism or myofascial pain) appeared to be much more affected than bruxers who were pain-free. The fact that pain from bruxism was worst in the morning suggests that it is possibly a form of postexercise muscle soreness. Myofascial pain, which was worst late in the day, is likely to have a different etiology.

A self-administered questionnaire consisting of 21 questions, diagrams for chief pain location, and a digital pain scale was used prospectively to sort 92 patients with orofacial pain into three categories: (1) musculoligamentous (ie, temporomandibular disorders); (2) neurologically based (ie, migraine, trigeminal neuralgia, tension-type headache, cluster headache, and atypical facial pain); and (3) dentoalveolar pain. Sensitivity, specificity, as well as negative and positive predictive values suggest that this questionnaire may be used reliably to identify patients with orofacial pain that fits the above-described pain categories without prior knowledge of the clinical diagnosis. Digital pain scale findings indicated that on presentation, pain level could not be correlated with any particular pain category, but when using this scale to describe past pain experience, patients with neurologically based pain selected the highest digital pain scale values up to six times more frequently than patients with musculoligamentous or dentoalveolar pain. Patients with musculoligamentous or dentoalveolar pain selected the lowest digital pain scale values up to 15 times more frequently than those with neurologically based pain. Although this questionnaire may be used for initial categorization of pain, there is still no substitute for a thorough history and clinical examination.

Neurosensory deficit is a major complication encountered in maxillofacial surgery. This study assessed the ability of electronic thermography to identify inferior alveolar nerve deficits in a pilot clinical study. The study population comprised six patients with inferior alveolar nerve deficit and 12 normal subjects. Frontally projected facial thermograms were taken on 18 subjects and measured using an Agema 870 unit and thermal image computer. Mathematical analysis of thermal measurements included temperature and delta T calculations of the anatomic zone over the mental region of the face. Results included (1) high levels of thermal symmetry of the chin in normal subjects (delta T = 0.1 degree C, standard deviation = 0.1 degree C); (2) low levels of thermal symmetry in patients with inferior alveolar nerve deficits (delta T = +0.5 degree C, standard deviation = 0.2 degree C); (3) statistically significant differences in delta T values (t = 4.82, P > .001) in patients with inferior alveolar nerve deficit; and (4) absolute temperature variations of the mental region in both groups. This pilot study demonstrated thermal asymmetry in patients with inferior alveolar nerve deficit and suggests that electronic thermography has promise as a simple, objective, noninvasive method for evaluating nerve deficits. However, more extensive studies are needed before thermographic procedures are accepted clinically.

The purpose of this study was to investigate thermography's potential as a diagnostic alternative for evaluating neurosensory deficits of the inferior alveolar nerve. Electronic thermography was used to evaluate the alterations in facial thermal patterns attendant to a conduction defect of the inferior alveolar nerve induced in 12 subjects using 2% lidocaine. The rates of onset and duration of sensory block, as visualized by thermography, were related to the results of conventional neurosensory testing. Comparison of the rate of response change within each measurement system revealed that changes in facial skin temperature manifest the induced deficit earlier than discriminative tests. Also, the prolonged elevation of thermal asymmetry suggested that electronic thermography has the ability to detect subtle changes in nerve function that are not discernible by physical neurosensory tests relying on patient response. Although cutaneous temperature increases were highest in the field of observation near the sensory distribution of the mental nerve, an inexplicable warming of the contralateral side of the face and neck was also observed. These attendant findings emphasize the need for further studies on the pathophysiologic mechanisms of facial thermal changes to better understand thermography's diagnostic accuracy and clinical utility for monitoring inferior alveolar nerve dysfunction.

Pain and tenderness at trigger points and referral sites may be modified in subjects with myofascial pain in the head and neck region by injecting local anesthetic into active trigger points, but the effect of injection on jaw muscle pain-pressure thresholds has not been measured. The mechanism by which trigger-point injection affects muscle tenderness is also unclear and may be related to the hyper-stimulation analgesia induced by stimulation of an acupuncture point. A pressure algometer was used before and after an active trigger point injection in the masseter to measure the pain-pressure threshold in the masseter and temporal muscles of 10 subjects with jaw muscle pain of myogenous origin. The pain-pressure threshold in the masseter and temporal muscles was also measured in a matched control group before and after an acupuncture-point injection in the masseter. The pain-pressure threshold was significantly lower in myofascial pain subjects than in control subjects at all recording sites. Pain-pressure thresholds increased minimally in the masseter after trigger-point injection, whereas the temporal region was relatively unaffected. In the control group, the pain-pressure threshold increased significantly at all recording sites in the masseter after acupuncture-point injection. Although local anesthetic injection acts peripherally at the painful site and centrally where pain is sustained, pain-pressure thresholds were not dramatically increased in myofascial pain subjects, in contrast to controls. This suggests that in subjects with myofascial pain, there was continued excitability in peripheral tissues and/or central neural areas which may have contributed to the persistence of jaw muscle tenderness.

Traumatic injury to the peripheral nerves often results in persistent discomfort. Substance P has been implicated as a mediator of pain, and depletion of this neurotransmitter has been shown to reduce pain. Subjects suffering from traumatic dysesthesia of the trigeminal nerve were treated with capsaicin, a substance P depleter with significant long-term effects. This form of therapy may be used individually or in combination with other pharmacologic interventions in the treatment of traumatic trigeminal dysesthesia.

The effects of cognitive-behavioral treatment for patients with temporomandibular disorders were studied by comparing active treatment to a wait-list control condition. Patients were predominantly women and had been referred to the study after having poor response to dental/physical medicine care. Patients' conditions were evaluated pretreatment and posttreatment based on self-report measures of pain, distress, and jaw function problems. They were examined by a dentist who assessed pain-free opening, muscle palpation pain, and tenderness of the temporomandibular joints. The 5-week cognitive-behavioral treatment included relaxation training, self-monitoring of stressors, and cognitive coping strategies. Treatment had its greatest impact on improving mood, especially anxiety; however, there were some effects on the patients' experiences of pain.

There is a general assumption that temporomandibular disorders and the pain and tenderness of mastication muscles may be caused by hyperactivity. Five asymptomatic men, five asymptomatic women, and five women with temporomandibular disorders participated in this study. Multiple examinations were performed to provide information concerning the reproducibility of the rest electromyographic signals. No significant differences between groups were noted. This study supports the contention that the mean rest activity in women with pain and dysfunction is less than or equal to that of sex-matched controls.

Seventy-one patients (128 joints) who underwent temporomandibular arthroscopies with lysis and lavage, capsular stretch, and release of adhesions and lateral capsular fibrosis were followed for an average of 24 months. Prearthroscopic and postarthroscopic temporomandibular joint tomograms were compared; 77.3% of the temporomandibular joints showed no postoperative changes, and 22.7% of the temporomandibular joints studied showed changes. The majority of these tomographic changes involved increase in condylar flattening and beaking. However, postoperative painful symptoms significantly decreased regardless of the radiographic findings.