Myofascial pain of the temporomandibular region (M-TMD) is a common, but poorly understood chronic disorder. It is unknown whether the condition is a peripheral problem, or a disorder of the central nervous system (CNS). To investigate possible CNS substrates of M-TMD, we compared the brain morphology of 15 women with M-TMD to 15 age- and gender-matched healthy controls. High-resolution structural brain and brainstem scans were carried out using magnetic resonance imaging (MRI), and data were analyzed using a voxel-based morphometry approach. The M-TMD group evidenced decreased or increased gray matter volume compared to controls in several areas of the trigeminothalamocortical pathway, including brainstem trigeminal sensory nuclei, the thalamus, and the primary somatosensory cortex. In addition, M-TMD individuals showed increased gray matter volume compared to controls in limbic regions such as the posterior putamen, globus pallidus, and anterior insula. Within the M-TMD group, jaw pain, pain tolerance, and pain duration were differentially associated with brain and brainstem gray matter volume. Self-reported pain severity was associated with increased gray matter in the rostral anterior cingulate cortex and posterior cingulate. Sensitivity to pressure algometry was associated with decreased gray matter in the pons, corresponding to the trigeminal sensory nuclei. Longer pain duration was associated with greater gray matter in the posterior cingulate, hippocampus, midbrain, and cerebellum. The pattern of gray matter abnormality found in M-TMD individuals suggests the involvement of trigeminal and limbic system dysregulation, as well as potential somatotopic reorganization in the putamen, thalamus, and somatosensory cortex.

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Pain tolerance in the masticatory muscles increased significantly more with acupuncture than sham acupuncture.

Objective A network meta‐analysis (NMA) of randomised clinical trials (RCTs) was performed aiming to compare the treatment outcome of dry needling, acupuncture or wet needling using different substances in managing myofascial pain of the masticatory muscles (TMD‐M). Method An electronic search was undertaken to identify RCTs published until September 2019, comparing dry needling, acupuncture or wet needling using local anaesthesia (LA), botulinum toxin‐A (BTX‐A), granisetron, platelet‐rich plasma (PRP) or passive placebo versus real active placebo in patients with TMD‐M. RCTs meeting the inclusion criteria were stratified according to the follow‐up time: immediate post‐treatment to 3 weeks, and 1 to 6 months post‐treatment. Outcome variables were post‐treatment pain intensity, increased mouth opening (MMO) and pressure threshold pain (PPT). The quality of evidence was rated according to Cochrane's tool for assessing risk of bias. Mean difference (MD) was used to analysed via frequentist NMA using Stata software. Results Twenty‐one RCTs involving 959 patients were included. The quality of evidence of the included studies was low or very low. There was significant pain decrease after PRP when compared to an active/passive placebo and acupuncture. There was a significant improvement of MMO after LA (MD = 3.65; CI: 1.18‐6.1) and dry needling therapy (MD = 2.37; CI: 0.66‐4) versus placebo. The three highest ranked treatments for short‐term post‐treatment pain reduction in TMD‐M (1‐20 days) were PRP (95.8%), followed by LA (62.5%) and dry needling (57.1%), whereas the three highest ranked treatments at intermediate‐term follow‐up (1‐6 months) were LA (90.2%), dry needling (66.1%) and BTX‐A (52.1%) (all very low‐quality evidence). LA (96.4%) was the most effective treatment regarding the increase in MMO followed by dry needling (72.4%). Conclusion Based on this NMA, one can conclude that the effectiveness of needling therapy did not depend on needling type (dry or wet) or needling substance. The outcome of this NMA suggests that LA, BTX‐A, granisetron and PRP hold some promise as injection therapies, but no definite conclusions can be drawn due to the low quality of evidence of the included studies. This NMA did not provide enough support for any of the needling therapies for TMD‐M.

Neither the etiology of muscle-related temporomandibular disorders (TMD) nor the reason for the disproportionate number of women suffering from these disorders is well-established. We tested the hypothesis that physiologically relevant exercise (i.e., chewing bubble gum for 6 min) increases masticatory muscle pain in patients, but not in asymptomatic control subjects, and that female patients experience a significantly greater increase than males. Chewing increased pain in both female and male patients and, unexpectedly, also in female control subjects. One hour after chewing, the pain remained above pre-test levels for female patients but not for the other groups. Thus, sex differences in chewing-induced pain were found in control subjects but not as hypothesized in patients. Because chewing-induced masticatory muscle pain was significantly greater in female control subjects than in males, and persisted longer in female patients than in males, these results suggest greater susceptibility in women.