Assessment of somatosensory changes in Chinese temporomandibular disorders arthralgia patients by quantitative sensory testing

Visual psychosocial profiling of Chinese temporomandibular disorder pain patients and correlations with somatosensory function

BACKGROUND

Psychosocial function of Chinese temporomandibular disorders (TMD) pain patients and the correlation with somatosensory function has not been sufficiently studied.

OBJECTIVE

The study aims at assessing the psychosocial function of Chinese TMD pain patients by visualisation method and evaluating the correlations with somatosensory function quantitatively.

METHODS

The Symptom Checklist 90 (SCL-90) questionnaire and standardised quantitative sensory testing (QST) were administered to 70 Chinese TMD pain patients and age- and gender-matched healthy controls (HCs). Of these, 40 TMD arthralgia patients received QST before and after medication. Psychosocial and somatosensory parameters were transformed into standardised scores. Differences within groups were assessed through t tests. Correlations between psychosocial and somatosensory profiles were explored through correlation analyses with Bonferroni correction for multiple comparisons.

RESULTS

100% of the Chinese TMD pain patients exhibited psychosocial distress in contrast to HCs. Anger and hostility showed negative correlation with the thermal nonnociceptive parameter (thermal sensory limen, p =.002) and nociceptive parameters (cold pain threshold and pain pressure threshold, p<.001). Correlation analysis indicated that cold detection threshold was negatively correlated with somatization and mechanical pain sensitivity had a negative correlation with anger and hostility through medical treatment (p <.001).

CONCLUSIONS

Visual psychosocial profiles provided an easy overview of psychosocial function in Chinese TMD pain patients. Anger and hostility was associated with increased thermal nonnociceptive and nociceptive sensitivity to stimuli. Psychosocial distress might be negatively associated with TMD treatment response which indicated a possible need for psychological intervention during treatment.

Forced mouth opening induces post-traumatic hyperalgesia and associated peripheral sensitization after temporomandibular joints injury in mice

Temporomandibular disorder (TMD) is the most prevalent painful condition in the craniofacial area. The pathophysiology of TMD is not fully understood, and it is necessary to understand pathophysiology underlying painful TMD conditions to develop more effective treatment methods. Recent studies suggested that external or intrinsic trauma to TMJ is associated with chronic TMD in patients. Here, we investigated the effects of the TMJ trauma through forced-mouth opening (FMO) in mice to determine pain behaviors and peripheral sensitization of trigeminal nociceptors. FMO increased mechanical hyperalgesia assessed by von Frey test, spontaneous pain-like behaviors assessed by mouse grimace scale, and anxiety-like behaviors assessed by open-field test. In vivo GCaMP Ca 2+ imaging of intact trigeminal ganglia (TG) showed increased spontaneous Ca 2+ activity and mechanical hypersensitivity of TG neurons in the FMO compared to the sham group. Ca 2+ responses evoked by cold, heat, and capsaicin stimuli were also increased. FMO-induced hyperalgesia and neuronal hyperactivities were not sex dependent. TG neurons sensitized following FMO were primarily small to medium-sized nociceptive afferents. Consistently, most TMJ afferents in the TG were small-sized peptidergic neurons expressing calcitonin gene-related peptides, whereas nonpeptidergic TMJ afferents were relatively low. FMO-induced intraneural inflammation in the surrounding tissues of the TMJ indicates potentially novel mechanisms of peripheral sensitization following TMJ injury. These results suggest that the TMJ injury leads to persistent post-traumatic hyperalgesia associated with peripheral sensitization of trigeminal nociceptors.

Evidence for alterations to dynamic quantitative sensory tests in patients with chronic temporomandibular myalgia: a systematic review of observational studies with meta-analysis

BACKGROUND

Conflicting results exist between somatosensory profiles of patients with temporomandibular myalgia (TMDm). The objective of this review was to examine whether adults with TMDm show altered responses to dynamic quantitative sensory tests compared with healthy controls.

METHODS

We searched five electronic databases for studies, excluding those without suitable controls or where TMDm was associated with confounding non-musculoskeletal disorders. Risk of bias was assessed with the SIGN case-control study checklist. Findings were structured around dynamic quantitative sensory tests and their localization. Where possible, we performed meta-analysis with a random inverse variance model to compare patients with TMDm and healthy controls. Statistical heterogeneity was estimated with Chi² test and inconsistency index, I².

RESULTS

We extracted data from 23 studies comprising 1284 adults with chronic TMDm and 2791 healthy controls. Risk of bias was assessed as high for 20 studies. Mechanical temporal summation, the most studied phenomenon (14 studies), is increased in the upper limb of patients with TMDm (SMD = .43; 95% CI: .11 to .75; p = .0001) but not in the jaw area (p = .09) or in the cervical area (p = .29). Very little evidence for altered thermal temporal summation (five studies), conditioned pain modulation (seven studies), exercise-induced hypoalgesia (two studies), placebo analgesia (two studies), stress-induced hypoalgesia (one study) and offset analgesia (one study) was found.

DISCUSSION

A major limitation of this review was the risk of bias of included studies. Future studies would benefit from following methodological guidelines and consideration of confounding factors.

Quantitative sensory testing in patients with the muscle pain subtype of temporomandibular disorder: a systemic review and meta-analysis

OBJECTIVES

This meta-analysis aimed to evaluate quantitative sensory testing (QST) evidence for pain processing in patients with the muscle pain subtype of temporomandibular disorders (mTMD).

MATERIALS AND METHODS

A comprehensive systematic electronic search strategy was performed in online literature databases. All full-text observational studies published up to July 2021 with the aim of investigating pain sensitization in humans with mTMD using QST measures were eligible for inclusion. Meta-analysis of QST data was performed using a random effects model, which included results comparing patients with mTMD to healthy controls, and standard mean difference (SMD) results were analyzed.

RESULTS

Twelve studies with 732 participants (371 patients with mTMD and 361 healthy controls) were analyzed following screening and quality appraisal. Compared with healthy controls, patients with mTMD had significantly lower pressure pain threshold (SMD - 1.10, 95% confidence interval [CI] - 1.52 to - 0.68) with high heterogeneity (Tau2 = 0.61, I2 = 86%), and significantly lower mechanical pain threshold (SMD - 0.64, 95% CI - 0.95 to - 0.32) with no heterogeneity (Tau2 = 0.00, I2 = 0%). No difference was observed in the cold pain threshold (SMD 0.16, 95% CI - 0.13 to 0.45), heat pain threshold (SMD - 0.13, 95% CI - 0.40 to 0.15), and wind-up ratio (SMD 0.63, 95% CI - 0.11 to 1.38) between patients with mTMD and healthy controls. Other QST parameters were also discussed.

CONCLUSIONS

The study results suggest that the pain processing of deep tissues is likely sensitized in mTMD and calls for more QST studies with standard procedures to reduce inter-study heterogeneity.

CLINICAL RELEVANCE

The major findings of this meta-analysis support using PPT to examine the pain processing in patients with mTMD in clinical scenario.

Preclinical models of deep craniofacial nociception and temporomandibular disorder pain

Chronic pain in temporomandibular disorder (TMD) is a common health problem. Cumulating evidence indicates that the etiology of TMD pain is complex with multifactorial experience that could hamper the developments of treatments. Preclinical research is a resource to understand the mechanism for TMD pain, whereas limitations are present as a disease-specific model. It is difficult to incorporate multiple risk factors associated with the etiology that could increase pain responses into a single animal. This article introduces several rodent models which are often employed in the preclinical studies and discusses their validities for TMD pain after the elucidations of the neural mechanisms based on the clinical reports. First, rodent models were classified into two groups with or without inflammation in the deep craniofacial tissues. Next, the characteristics of each model and the procedures to identify deep craniofacial pain were discussed. Emphasis was directed on the findings of the effects of chronic psychological stress, a major risk factor for chronic pain, on the deep craniofacial nociception. Preclinical models have provided clinically relevant information, which could contribute to better understand the basis for TMD pain, while efforts are still required to bridge the gap between animal and human studies.

Sensory recovery and oral health-related quality of life following tongue reconstruction using non-innervated radial forearm free flaps

OBJECTIVES

This study aimed to monitor the recovery of somatosensory function and oral health-related quality of life after tongue reconstruction using a non-innervated radial forearm free flap (RFFF).

METHODS

Twenty patients (9 men, age: 42-67 years) underwent tongue reconstruction with non-innervated RFFFs, and twenty age- and sex-matched controls were included in this study. Quantitative sensory testing (QST), including cold, warm, and mechanical detection thresholds (CDT, WDT, MDT); cold, heat, and mechanical pain thresholds (CPT, HPT, MPT); and static two-point, sharp/blunt, and direction discrimination (S2-PD, S/BD, DD) were determined 9 months and 18 months after surgery on the surgical (9 M, 18 M) and contralateral sides (9Mc, 18Mc). Oral Health Impact Profile-49 (OHIP-49) was used to determine the oral-related quality of life of participants.

RESULTS

All parameters showed significantly lower sensitivity at 9 M and 18 M (p < 0.001) compared to those for the controls and the contralateral side, except for DD (p = 0.101). In addition, the parameters showed a significant decrease in sensitivity for 9Mc and 18Mc (p ≤ 0.043) compared to those for the controls, except for MPT, HPT, S/SD, and DD (p ≥ 0.453). Findings on WDT, MPT, S2-PD, and DD (p ≤ 0.046) indicated significantly higher somatosensory function at 18 M than that at 9 M. MDT and MPT (p ≤ 0.038) showed significantly higher sensitivity at 18Mc than at 9Mc. Scores for all dimensions of OHIP-49 were significantly higher in patients (decrease in quality of life, p ≤ 0.002) than in controls, except for physical discomfort (p = 0.51). However, the scores were significantly higher at 18 M than at 9 M (p ≤ 0.011), except for handicap (p = 0.36). Postoperative chemotherapy was significantly correlated with impaired thermal sensitivity of the flaps (WDT, p = 0.049).

CONCLUSION

The present findings showed significant impairment in somatosensory function on both the surgical and contralateral sides of patients with RFFFs. However, a significant increase in somatosensory function was observed on both sides over time. Somatosensory disturbances observed after surgery were associated with poor oral health-related quality of life.

A comprehensive review on biomarkers associated with painful temporomandibular disorders

Pain of the orofacial region is the primary complaint for which patients seek treatment. Of all the orofacial pain conditions, one condition that possess a significant global health problem is temporomandibular disorder (TMD). Patients with TMD typically frequently complaints of pain as a symptom. TMD can occur due to complex interplay between peripheral and central sensitization, endogenous modulatory pathways, and cortical processing. For diagnosis of TMD pain a descriptive history, clinical assessment, and imaging is needed. However, due to the complex nature of pain an additional step is needed to render a definitive TMD diagnosis. In this review we explicate the role of different biomarkers involved in painful TMD. In painful TMD conditions, the role of biomarkers is still elusive. We believe that the identification of biomarkers associated with painful TMD may stimulate researchers and clinician to understand the mechanism underlying the pathogenesis of TMD and help them in developing newer methods for the diagnosis and management of TMD. Therefore, to understand the potential relationship of biomarkers, and painful TMD we categorize the biomarkers as molecular biomarkers, neuroimaging biomarkers and sensory biomarkers. In addition, we will briefly discuss pain genetics and the role of potential microRNA (miRNA) involved in TMD pain.