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Patients with temporomandibular disorder ( TMD) report poor sleep quality on the Pittsburgh Sleep Quality Index ( PSQI). However, polysomnographic ( PSG) studies show meagre evidence of sleep disturbance on standard physiological measures. The present aim was to analyse self-reported sleep quality in TMD as a function of myofascial pain, PSG parameters and depressive symptomatology. PSQI scores from 124 women with myofascial TMD and 46 matched controls were hierarchically regressed onto TMD presence, ratings of pain intensity and pain-related disability, in-laboratory PSG variables and depressive symptoms (Symptoms Checklist-90). Relative to controls, TMD cases had higher PSQI scores, representing poorer subjective sleep and more depressive symptoms (both P < 0·001). Higher PSQI scores were strongly predicted by more depressive symptoms ( P < 0·001, R2 = 26%). Of 19 PSG variables, two had modest contributions to higher PSQI scores: longer rapid eye movement latency in TMD cases ( P = 0·01, R2 = 3%) and more awakenings in all participants ( P = 0·03, R2 = 2%). After accounting for these factors, TMD presence and pain ratings were not significantly related to PSQI scores. These results show that reported poor sleep quality in TMD is better explained by depressive symptoms than by PSG-assessed sleep disturbances or myofascial pain. As TMD cases lacked typical PSG features of clinical depression, the results suggest a negative cognitive bias in TMD and caution against interpreting self-report sleep measures as accurate indicators of PSG sleep disturbance. Future investigations should take account of depressive symptomatology when interpreting reports of poor sleep. [ABSTRACT FROM AUTHOR]

Sleep bruxism ( SB), primarily involving rhythmic grinding of the teeth during sleep, has been advanced as a causal or maintenance factor for a variety of oro-facial problems, including temporomandibular disorders ( TMD). As laboratory polysomnographic ( PSG) assessment is extremely expensive and time-consuming, most research testing this belief has relied on patient self-report of SB. The current case-control study examined the accuracy of those self-reports relative to laboratory-based PSG assessment of SB in a large sample of women suffering from chronic myofascial TMD ( n = 124) and a demographically matched control group without TMD ( n = 46). A clinical research coordinator administered a structured questionnaire to assess self-reported SB. Participants then spent two consecutive nights in a sleep laboratory. Audiovisual and electromyographic data from the second night were scored to assess whether participants met criteria for the presence of 2 or more (2+) rhythmic masticatory muscle activity episodes accompanied by grinding sounds, moderate SB, or severe SB, using previously validated research scoring standards. Contingency tables were constructed to assess positive and negative predictive values, sensitivity and specificity, and 95% confidence intervals surrounding the point estimates. Results showed that self-report significantly predicted 2+ grinding sounds during sleep for TMD cases. However, self-reported SB failed to significantly predict the presence or absence of either moderate or severe SB as assessed by PSG, for both cases and controls. These data show that self-report of tooth grinding awareness is highly unlikely to be a valid indicator of true SB. Studies relying on self-report to assess SB must be viewed with extreme caution. [ABSTRACT FROM AUTHOR]

Despite theoretical speculation and strong clinical belief, recent research using laboratory polysomnographic ( PSG) recording has provided new evidence that frequency of sleep bruxism ( SB) masseter muscle events, including grinding or clenching of the teeth during sleep, is not increased for women with chronic myofascial temporomandibular disorder ( TMD). The current case-control study compares a large sample of women suffering from chronic myofascial TMD ( n = 124) with a demographically matched control group without TMD ( n = 46) on sleep background electromyography ( EMG) during a laboratory PSG study. Background EMG activity was measured as EMG root mean square ( RMS) from the right masseter muscle after lights out. Sleep background EMG activity was defined as EMG RMS remaining after activity attributable to SB, other orofacial activity, other oromotor activity and movement artefacts were removed. Results indicated that median background EMG during these non- SB event periods was significantly higher ( P < 0·01) for women with myofascial TMD (median = 3·31 μV and mean = 4·98 μV) than for control women (median = 2·83 μV and mean = 3·88 μV) with median activity in 72% of cases exceeding control activity. Moreover, for TMD cases, background EMG was positively associated and SB event-related EMG was negatively associated with pain intensity ratings (0-10 numerical scale) on post-sleep waking. These data provide the foundation for a new focus on small, but persistent, elevations in sleep EMG activity over the course of the night as a mechanism of pain induction or maintenance. [ABSTRACT FROM AUTHOR]

A study of the forces exerted by cats against the ground when jumping from a platform equipped with force transducers, was carried out. The study, complemented by film analysis of the jump, attempted to disclose some of the mechanisms underlying the decrease in efficiency and accuracy in releasing a moving piece of liver observed after dorsal funiculi section above C level. The results showed that after the lesion, peak force and height of jump were significantly reduced. However, angle of take-off, an index of force distribution in the three axes of rectangular coordinates remained unchanged. Intact cats consistently extend their forelimbs in a smooth and progressive way toward the liver in order to release it. The distance between the tips of the forelimbs remained more or less constant during the flight. Postoperatively, instead of the regular pattern described, the extension of the limbs was interrupted by fast marked flexion movements and the distance between their tips increased significantly during the flight. Peak extension of the forelimbs was also decreased after surgery. The results are interpreted in terms of the different disruption of the various components (proprio and exteroceptive) that make up fasciculus gracilis and cuneatus of the dorsal funiculi. [ABSTRACT FROM AUTHOR]

Quantitative evaluation was carried out on the ability of cats to execute a sequential act requiring precise timing for its initiation (jump), accurate projection of the forelimb and appropriate visual tracking during motor performance. Comparison of results before and after section of the Dorsal Columns at the first cervical level revealed obvious postoperative inefficiency in the overall performance of the act. The accuracy of extrapersonally projected movements of the forelimbs (reaching towards a moving target) was seriously affected, as was the capacity to visually track a target in space during the jump. Testing which did not require jumping up towards the target, but merely rearing on the hindlimbs, showed no improvement in the performance of lesioned animals when compared to controls. The deficits mentioned also persisted in animals subjected to preoperative overtraining and prolonged postsurgical testing, a procedure which in certain tasks allows the animal to perform normally after surgery. Physiologically, the Dorsal Columns have been shown to be the exclusive path of fibers from muscle spindles and low threshold joint receptors from the forelimbs. The corresponding fibers from the hindlimbs reach higher centers via different pathways. The loss of this information from forelimbs resulting from high cervical Dorsal Column section may then help to explain the deficits described. [ABSTRACT FROM AUTHOR]

The effects of 18-hydroxydeoxycorticosterone (18-OH-DOC) on central nervous system excitability were studied in adrenalectomized rats. Sixty-four evoked potentials (EP) recorded from the pontine reticular formation were averaged before and after the injection of vehicle and hormone. 750 μg of 18-OH-DOC dissolved in 0.5 ml of a 4∶1 saline Cremophor-EL solution were injected i.v. A decrease of 55.7±6.1% in the amplitude of the EPs was observed with the hormone 16.3 min±2.7 (SE) after injection. Amplitude values returned to baseline levels 38 min±6.8 (SE) after injection. The secretion of 18-OH-DOC is greatly increased by ACTH and might modulate central nervous system function. [ABSTRACT FROM AUTHOR]