Association of decrease in insula fMRI activation with changes in trait anxiety in patients with craniomandibular disorder (CMD)

Pain Catastrophizing and Functional Activation During Occlusion in TMD Patients-An Interventional Study

In temporomandibular disorder (TMD), the effects of standard interventions such as using an occlusal splint and its impact on pain relief and pain catastrophizing are poorly understood. Earlier work pointed to a crucial role of insula activation with changes in pain relief by occlusal splint treatment. We performed a functional imaging study using specially developed splint systems to allow for a placebo-controlled longitudinal design. Using functional MRI we examined 20 TMD patients during repetitive occlusal movements at baseline and over the course of splint therapy and also collected self-reported pain catastrophizing. For balancing performance between baseline and after intervention we used occlusion force measures in an individualized fMRI-splint system. Splint therapy lasted for approximately 7 weeks with one group selected by randomization wearing a palatine placebo splint over the first 3 weeks (delayed start; 11 individuals). As expected, fMRI activation in areas involved in pain processing (insula, primary and secondary somatosensory cortex) decreased with intervention. At baseline a positive correlation between activation of the left anterior insula and pain catastrophizing was present. Both parameters decreased over intervention while associations were primarily observable for patients with rather mild TMD.

Pain and salivary biomarkers of stress in temperomandibular disorders were affected by maxillary splints

BACKGROUND

Longitudinal intervention studies on treatment options in temporomandibular dysfunction (TMD) including self reports and salivary biomarkers of stress are rare and the exact therapeutic function of occlusal splints widely unknown.

METHODS

We examined the therapeutic effects of a Michigan splint with occlusal relevance in patients with TMD using a placebo-controlled, delayed-start design. Two intervention groups received a Michigan splint, while one of them had a placebo palatine splint for the first 3 weeks. We collected pain intensities (at rest and after five occlusal movements), salivary measures associated with stress (cortisol and alpha-amylase) and self-reported psychological distress (stress, anxiety, catastrophizing) at baseline and 3 and 7 weeks after onset of intervention.

RESULTS

At baseline, we observed increased pain intensity and psychological distress in TMD patients compared to 11 matched healthy controls. Baseline anxiety was linked to movement pain intensity through stress. Over therapy reductions in pain intensity and morning cortisol were more pronounced in those patients starting immediately with the Michigan splint, while psychological distress decreased similarly in both groups.

CONCLUSION

Our results suggest that perceived stress plays a role for the association between anxiety and TMD pain and underlines the need for an interdisciplinary perspective on the pathogenesis and therapy of TMD in a setting where psychotherapeutic knowledge is still scarce or rarely applied.

Anxiety mediates association between sex and jaw function limitation in temporomandibular disorder patients from China

Aim

The objective of this study is to explore the relationship between sex and jaw function and to test whether anxiety mediates the causal relationship between sex and jaw function in temporomandibular disorders (TMDs) patients.

Methods

A total of 488 participants with TMD were included in the analysis. Demographic data were collected. Generalized anxiety symptoms and anxiety severity were initially assessed using the GAD-7 questionnaire. And jaw function limitation was measured using the JFLS-8 scale. A directed acyclic graph (DAG) was used in this study to evaluate the hypotheses. Mediation analysis was conducted to explore causality and to calculate the total effect, natural direct effect (NDE) and natural indirect effect (NIE).

Results

In TMD patients, there was a significant association between female and jaw function (r = 0.17, p < 0.001), female and anxiety (r = 0.15, p = 0.002), anxiety and jaw function (r = 0.35, p < 0.001). In addition, sex can directly lead to differences in impaired jaw function (NDE: 3.719, 95% CI: 1.619-5.828, p < 0.001), and can also be causally related to jaw function through anxiety (NIE: 1.146, 95% CI: 0.267-2.024, p = 0.011). And the total effect was 4.865 (95% CI, 2.709-7.029, p < 0.001).

Conclusion

A causal mechanism was found that anxiety acts as a mediator of sex effects on jaw function. Therefore, psychological factors need to be taken into account in the treatment of female TMD patients. Further clinical trials are needed to explore whether psychotherapy is more beneficial to improve jaw function in female TMD patients.

Neuroimaging meta-analysis of brain mechanisms of the association between orofacial pain and mastication

BACKGROUND

Temporomandibular disorders (TMD) are characterized by pain and impaired masticatory functions. The Integrated Pain Adaptation Model (IPAM) predicts that alterations in motor activity may be associated with increased pain in some individuals. The IPAM highlights the diversity of patients' responses to orofacial pain and suggests that such diversity is related to the sensorimotor network of the brain. It remains unclear whether the pattern of brain activation reflects the diversity of patients' responses underlying the association between mastication and orofacial pain.

OBJECTIVE

This meta-analysis aims to compare the spatial pattern of brain activation, as the primary outcome of neuroimaging studies, between studies of mastication (i.e. Study 1: mastication of healthy adults) and studies of orofacial pain (i.e. Study 2: muscle pain in healthy adults and Study 3: noxious stimulation of the masticatory system in TMD patients).

METHODS

Neuroimaging meta-analyses were conducted for two groups of studies: (a) mastication of healthy adults (Study 1, 10 studies) and (b) orofacial pain (7 studies), including muscle pain in healthy adults (Study 2) and noxious stimulation of the masticatory system in TMD patients (Study 3). Consistent loci of brain activation were synthesized using Activation Likelihood Estimation (ALE) with an initial cluster-forming threshold (p < .05) and a threshold of cluster size (p < .05, familywise error-corrected).

RESULTS

The orofacial pain studies have shown consistent activation in pain-related regions, including the anterior cingulate cortex and the anterior insula (AIns). A conjunctional analysis of mastication and orofacial pain studies showed joint activation at the left AIns, the left primary motor cortex and the right primary somatosensory cortex.

CONCLUSION

The meta-analytical evidence suggests that the AIns, as a key region in pain, interoception and salience processing, contributes to the pain-mastication association. These findings reveal an additional neural mechanism of the diversity of patients' responses underlying the association between mastication and orofacial pain.

Tooth-Cutting-Induced Maxillary Malocclusion Exacerbates Cognitive Deficit in a Mouse Model of Vascular Dementia

Treatments to restore the balance of the temporomandibular joint (TMJ) are performed in the field of complementary and alternative medicine; however, evidence supporting this approach remains weak. Therefore, this study attempted to establish such evidence. Bilateral common carotid artery stenosis (BCAS) operation, which is commonly used for the establishment of a mouse model of vascular dementia, was performed, followed by tooth cutting (TEX) for maxillary malocclusion to promote the imbalance of the TMJ. Behavioural changes, changes in nerve cells and changes in gene expression were assessed in these mice. The TEX-induced imbalance of the TMJ caused a more severe cognitive deficit in mice with BCAS, as indicated by behavioural changes in the Y-maze test and novel object recognition test. Moreover, inflammatory responses were induced via astrocyte activation in the hippocampal region of the brain, and the proteins involved in inflammatory responses were found to be involved in these changes. These results indirectly show that therapies that restore the balance of the TMJ can be effectively used for the management of cognitive-deficit-related brain diseases associated with inflammation.

Relationship between dental occlusion and brain activity: A narrative review

Objectives

Occlusal function stimulates different areas of the cerebral cortex. The purpose of this narrative review was to identify the relationship between occlusion and brain activity so as to provide theoretical support to enable future studies on the subject.

Study selection, data, and sources

Relevant case-control studies, clinical trials, and systematic reviews available in English were retrieved from the following databases: MEDLINE, PubMed, ScienceDirect, Wiley Online Library, and Biblioteca Virtual en Salud (BVS). Of the 53 articles obtained, 12 were included.

Conclusion

The sensorimotor cortex is affected by changes in occlusion. It is speculated that occlusion could play an important role in the development of diseases, from anxiety and stress to Alzheimer’s disease and senile dementia. Further investigations into the interactions between occlusion and brain function are needed to elucidate the parts of the brain that are affected when occlusion is disturbed and to determine whether brain function is altered.

Clinical significance

Dentists must consider that alterations in the occlusal pattern during mastication can lead to changes in the activation of different brain regions related to memory, learning, anticipatory pain, and anxiety. This suggests that mastication maintains the integrity of certain brain areas and that it may be a key factor in the onset of neurodegenerative diseases.

State and Trait Anxiety Share Common Network Topological Mechanisms of Human Brain

Anxiety is a future-oriented unpleasant and negative mental state induced by distant and potential threats. It could be subdivided into momentary state anxiety and stable trait anxiety, which play a complex and combined role in our mental and physical health. However, no studies have systematically investigated whether these two different dimensions of anxiety share a common or distinct topological mechanism of human brain network. In this study, we used macroscale human brain morphological similarity network and functional connectivity network as well as their spatial and temporal variations to explore the topological properties of state and trait anxiety. Our results showed that state and trait anxiety were both negatively correlated with the coefficient of variation of nodal efficiency in the left frontal eyes field of volume network; state and trait anxiety were both positively correlated with the median and mode of pagerank centrality distribution in the right insula for both static and dynamic functional networks. In summary, our study confirmed that state and trait anxiety shared common human brain network topological mechanisms in the insula and the frontal eyes field, which were involved in preliminary cognitive processing stage of anxiety. Our study also demonstrated that the common brain network topological mechanisms had high spatiotemporal robustness and would enhance our understanding of human brain temporal and spatial organization.

Complex Regional Pain Syndrome: Thalamic GMV Atrophy and Associations of Lower GMV With Clinical and Sensorimotor Performance Data

Results on gray matter alterations in complex regional pain syndrome (CRPS) showed heterogeneous findings. Since CRPS is a rare disease, most studies included only small and heterogeneous samples resulting in a low reliability of findings between studies. We investigated 24 CRPS patients with right upper limb affection in the chronic stage of disease using structural MRI and clinical testing. We focused on gray matter volume (GMV) alterations of the brain in comparison to 33 age matched healthy controls, their association to clinical characteristics (duration of pain syndrome and pain intensity ratings) and sensorimotor performance (finger dexterity and spatiotactile resolution). When applying an explorative whole brain analysis CRPS patients showed lower GMV in the bilateral medial thalamus. No other areas showed a relevant GMV difference for the group comparisons. When applying a region of interest driven approach using anatomical masks of the thalamus, ACC/mPFC, putamen, and insula we found relevant associations of clinical and behavioral data in ACC and insula. Whereas, the GMV in ACC showed negative associations with pain intensity and CRPS duration, the GMV of the left posterior insula was negatively associated with sensorimotor performance of the affected hand side. Overall, our results are in accordance to results of others describing a thalamic reduction of GMV in patients with neuropathic pain and are also in accordance with associations of pain intensity and duration with reduced ACC in general in patients with chronic pain syndromes. Sensorimotor performance seems to be related to posterior insula GMV reduction, which has not been described yet for other patient groups.

Severe Pain in Chronic Pancreatitis Patients: Considering Mental Health and Associated Genetic Factors

Pain is the most distressing and disruptive feature of recurrent acute pancreatitis (RAP) and chronic pancreatitis (CP) resulting in low quality of life (QOL) and disabilities. There is no single, characteristic pain pattern in patients with RAP and CP. Abdominal imaging features of CP accurately reflect morphologic features but they do not correlate with pain. Pain is the major driver of poor quality of life (QOL) and it is the constant pain, rather than intermittent pain that drives poor QOL. Furthermore, the most severe constant pain experience in CP is also a complex condition. The ability to target the etiopathogenesis of severe pain requires new methods to detect the exact pain mechanisms in an individual at cellular, tissue, system and psychiatric levels. In patients with complex and severe disease, it is likely that multiple overlapping mechanisms are simultaneously driving pain, anxiety and depression. Quantitative sensory testing (QST) shows promise in detecting alterations in central processing of pain signals and to classify patients for mechanistic and therapeutic studies. New genetic research suggests that genetic loci for severe pain in CP overlap with genetic loci for depression and other psychiatric disorders, providing additional insights and therapeutic targets for individual patients with severe CP pain. Well-designed clinical trials that integrate clinical features, QST, genetics and psychological assessments with targeted treatment and assessment of responses are required for a quantum leap forward. A better understanding of the context and mechanisms contributing to severe pain experiences in individual patients is predicted to lead to better therapies and quality of life.