A translation and validation of the French version of the Gothenburg Trismus Questionnaire 2 (F-GTQ-2)

BACKGROUND

Limitation of mouth opening, widely known as trismus, is a major symptom altering quality of life in individuals presenting from temporomandibular joint disorder or head and neck cancer. A French-language instrument addressing jaw opening limitation following treatment for head and neck cancer (HNC) or temporomandibular joint disorder (TMD) is lacking.

OBJECTIVE

The aim of this study was to translate and validate the Gothenburg Trismus Questionnaire-2 (GTQ-2) into French.

METHODS

A French translation of the GTQ-2 was performed according to established international guidelines, leading to the French-GTQ-2 (F-GTQ-2). The validation study included 154 participants with trismus (minimum interincisal opening of ≤35 mm) following treatment for TMD or HNC and 149 age-matched participants without trismus. All participants completed the F-GTQ-2 and participants with trismus completed additional health-related quality of life questionnaires to allow for analysis of convergent validity.

RESULTS

The F-GTQ-2 demonstrated retained psychometric properties with Cronbach's alpha values above 0.70 for the domains, jaw-related problems, eating limitations, facial pain and somewhat lower for muscular tension (0.60). Mainly moderate correlations were found when comparing the F-GTQ-2 to other instruments, which was in line with the pre-specified hypotheses, indicating satisfactory convergent validity. Discriminant validity was found with statistically significant differences in all domains of the F-GTQ-2 between trismus and non-trismus participants.

CONCLUSION

The F-GTQ-2 can be considered a reliable and valid instrument to assess jaw-related difficulties in individuals with trismus due to HNC or TMD.

The effect of different pain characteristics on jaw functional limitations in patients with temporomandibular disorders

BACKGROUND

Patients with painful temporomandibular disorders (TMD) more often experience jaw functional limitations. The study of jaw functional limitations should be primarily focused on painful TMD.

OBJECTIVES

The impact of TMD pain characteristics (source, chronicity and intensity) on jaw functional limitations were evaluated using Jaw Functional Limitation Scale (JFLS).

METHODS

This cross-sectional study reviewed the dental records and self-report questionnaires of patients with painful TMD. The pain source, chronicity and intensity were evaluated to study the TMD pain characteristics. The jaw functional limitations were analysed using the Thai version of the JFLS.

RESULTS

A total of 176 patients with painful TMD were included in this study. The jaw functional limitations were affected only by pain intensity. Patients with TMD with severe pain intensity had significantly higher jaw functional limitations than those with mild-to-moderate pain intensity (p < .05). A significant association was observed between pain intensity and jaw functional limitations (p < .05). Mastication was highly restricted by pain intensity (odd ratio = 1.39, 95% confidence interval = 1.16-1.67).

CONCLUSION

The present study found a significant effect of TMD pain intensity on jaw functional limitations. Patients with severe TMD pain intensity were more likely to experience jaw functional limitations, particularly mastication limitation. Management focusing on reduction of pain intensity may improve jaw functions in patients with 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.

Association between oxidative stress and chronic orofacial pain and potential druggable targets: Evidence from a Mendelian randomization study

BACKGROUND

Oxidative stress indicators affect chronic orofacial pain (COFP), but how to reduce these effects is uncertain.

OBJECTIVES

11 oxidative stress biomarkers were collected as exposures, while four forms of COFP were chosen as outcomes for Mendelian randomization (MR) study.

METHODS

The effect estimates between oxidative stress and COFP were calculated using inverse variance-weighted MR (IVW-MR). Then, functional mapping and annotation (FUMA) was utilized in order to carry out SNP-based functional enrichment analyses. In addition, the IVW-MR method was applied to combine effect estimates when using genetic variants associated with oxidative stress biomarkers as an instrument for exploring potential druggable targets.

RESULTS

The results indicated that oxidative stress biomarkers (causal OR of uric acid (UA), 0.998 for myofascial pain, 95% CI 0.996-1.000, p < .05; and OR of glutathione transferase (GST), 1.002 for dentoalveolar pain, 95% CI 1.000-1.003, p < .05) were significantly linked with the probability of COFP. Functional analysis also demonstrated that UA and myofascial pain genes were prominent in nitrogen and uracil metabolism, while GST and dentoalveolar pain genes were enriched in glutathione metabolism. Also, the study provided evidence that solute carrier family 2 member 9 (SLC2A9) and glutathione S-transferase alpha 2 (GSTA2) cause discomfort in the myofascial pain (OR = 1.003, 95% CI 1.000-1.006; p < .05) and dentoalveolar region (OR = 1.001, 95% CI 1.000-1.002; p < .05), respectively.

CONCLUSIONS

In conclusion, this MR study indicates that genetically predicted myofascial pain was significantly associated with decreased UA and dentoalveolar pain was significantly associated with increased GST level. SLC2A9 inhibitor and GSTA2 inhibitor were novel chronic orofacial pain therapies and biomarkers, but clinical trials are called to examine if these oxidative biomarkers have the protective effect against orofacial pain, and further research are needed to explore the underlying mechanisms.

Influence of psychometric and sleep quality features on painful mechanical sensitivity and pain modulation in patients with temporomandibular disorders

Investigating the collective impact of psychometric properties and sleep quality on pain sensitivity in temporomandibular disorder (TMD) patients could improve clinical management strategies.

OBJECTIVE

Assessing whether combined psychometric properties and sleep quality impact painful mechanical sensitivity and pain modulation in TMD patients.

MATERIALS AND METHODS

A cross-sectional study using secondary data analysis of 77 TMD patients and 101 controls. All participants completed questionnaires characterizing their psychometric profile (anxiety, depression, stress and catastrophizing) and sleep quality, alongside psychophysical tests for painful mechanical sensory (mechanical pain threshold (MPT), pressure pain threshold (PPT), and wind-up ratio (WUR)) and conditioned pain modulation (CPM). Participants were grouped into "High distress" or "Low distress" categories based on psychometric properties and sleep quality using hierarchical cluster and k-means analyses. Multiple linear regression evaluated the influence of TMD, age, and the distress cluster on MPT, WUR, PPT, and CPM in masseter and thenar muscles. Differences were statistically significant when p < 0.05.

RESULTS

The presence of TMD was the strongest predictor of mechanical painful sensitivity in the trigeminal region (MPT[F(3,174) = 51.902;p < .001;R2 = .463]; TMD presence (β = -.682) / PPT[F(3,174) = 15.573;p < .001;R2 = .198] TMD presence (β = -.452), and extra-trigeminal (MPT[F(3,174) = 35.897;p < .001;R2 = .382] TMD (β = -.647) / CPM [F(3,174) = 4.106;p < .05;R2 = .050] TMD presence (β = .197). Furthermore, neither the high distress group nor the low distress group were able to significantly influence the variation of the values of any of the psychophysical variables evaluated (p > .05).

CONCLUSIONS

There is not a significant influence of impairment clusters based on psychological variables and sleep quality on painful mechanical sensitivity and pain modulation, regardless of the presence of TMD.

CLINICAL RELEVANCE

This outcome suggests that psychosocial factors and sleep quality may not play a decisive role in the sensory-discriminative aspect of pain, particularly concerning painful TMD.

Differential Activation of Colonic Afferents and Dorsal Horn Neurons Underlie Stress-Induced and Comorbid Visceral Hypersensitivity in Female Rats

Chronic Overlapping Pain Conditions, including irritable bowel syndrome (IBS) and temporomandibular disorder (TMD), represent a group of idiopathic pain conditions that likely have peripheral and central mechanisms contributing to their pathology, but are poorly understood. These conditions are exacerbated by stress and have a female predominance. The presence of one condition predicts the presence or development of additional conditions, making this a significant pain management problem. The current study was designed to determine if the duration and magnitude of peripheral sensitization and spinal central sensitization differs between restraint stress-induced visceral hypersensitivity (SIH) and chronic comorbid pain hypersensitivity (CPH; stress during pre-existing orofacial pain). SIH in female rats, as determined by the visceromotor response, persisted at least four but resolved by seven weeks. In contrast, CPH persisted at least seven weeks. Surprisingly, colonic afferents in both SIH and CPH rats were sensitized at seven weeks. CPH rats also had referred pain through seven weeks, but locally anesthetizing the colon only attenuated the referred pain through four weeks, suggesting a transition to colonic afferent independent central sensitization. Different phenotypes of dorsal horn neurons were sensitized in the CPH rats seven weeks post stress compared to four weeks or SIH rats. The current study suggests differential processing of colonic afferent input to the lumbosacral spinal cord contributes to visceral hypersensitivity during comorbid chronic pain conditions. PERSPECTIVE: Chronic Overlapping Pain Conditions represent a unique challenge in pain management. The diverse nature of peripheral organs hinders a clear understanding of underlying mechanisms accounting for the comorbidity. This study highlights a mismatch between the condition-dependent behavior and peripheral and spinal mechanisms that contribute to visceral pain hypersensitivity.

Internalizing problems are associated with oral health-related quality of life in early childhood: Outcomes from an Asian multi-ethnic prospective birth cohort

Oral health status ideally warrants for a holistic biopsychosocial approach to health and wellness. Little is known about the impact of behavioral problems on oral health-related quality of life (OHRQoL) in children due to the paucity of studies in early childhood, particularly in Asian multi-ethnic populations. This study evaluated the relationship between early child's socioemotional factors and OHRQoL, as well as its association with orofacial pain (OFP) and early childhood caries (ECC) in the Asian GUSTO birth cohort. Mother-child dyads were postnatally assessed at 3 time points. The Child Behavior Checklist (CBCL) was used to assess the child's socioemotional and behavioral problems at age 4-4.5 years together with other validated questionnaires to evaluate maternal anxiety and depression. ECC detection was performed at age 5, and OHRQoL (primary) and OFP (secondary) outcomes were assessed at age 6 from a total of 555 mother-child dyads. After a univariate regression analysis was performed to identify potential predictors and confounders, a multivariate regression model was run with predisposing factors (CBCL internalization and externalization problems, OFP, ECC) and adjusted for confounders (maternal psychosocial states, maternal education) to determine associations with OHRQoL. Results showed an association between CBCL internalization scores and poorer OHRQoL (RR = 1.03, p = 0.033, 95% CI 1.01 to 1.05), although the limited risk ratio may not have a practical applicability in psychosocially healthy children, alike the majority of those evaluated in this cohort. The average OHRQoL overall score among children with OFP was 2.39 times more than those without OFP (OR = 2.39, p < 0.001, 95% CI 2.00 to 2.86). Thus, in early childhood, OFP, and to lesser extent internalizing behaviors, may negatively impact OHRQoL. This study therefore highlights the complex relationship between OHRQoL and its predisposing socioemotional and somatic pain factors, and demands further investigations in clinically relevant populations.

Reduced activity of GAD67 expressing cells in the reticular thalamus enhance thalamic excitatory activity and varicella zoster virus associated pain

Within the reticular thalamic nucleus neurons express gamma aminobutyric acid (GABA) and these cells project to the ventral posteromedial thalamic nucleus. When GABA activity decreases the activity of excitatory cells in the ventral posteromedial nucleus would be expected to increase. In this study, we addressed the hypothesis that attenuating GABAergic cells in the reticular thalamic nucleus increases excitatory activity in the ventral posteromedial nucleus increasing varicella zoster virus (VZV) associated pain in the orofacial region. Adeno-associated virus (AAV) was infused in the reticular thalamic nucleus of Gad1-Cre rats. This virus transduced a G inhibitory designer receptor exclusively activated by designer drugs (DREADD) gene that was Cre dependent. A dose of estradiol that was previously shown to reduce VZV pain and increase GABAergic activity was administered to castrated and ovariectomized rats. Previous studies suggest that estradiol attenuates herpes zoster pain by increasing the activity of inhibitory neurons and decreasing the activity of excitatory cells within the lateral thalamic region. The ventral posteromedial nucleus was infused with AAV containing a GCaMP6f expression construct. A glass lens was implanted for miniscope imaging. Our results show that the activity of GABA cells within the reticular thalamic region decreased with clozapine N-oxide treatment concomitant with increased calcium activity of excitatory cells in the ventral posteromedial nucleus and an increased orofacial pain response. The results suggest that estradiol attenuates herpes zoster pain by increasing the activity of inhibitory neurons within the reticular thalamus that then inhibit excitatory activity in ventral posteromedial nucleus causing a reduction in orofacial pain.

Efficacy and Safety of Botulinum Toxin Type A on Persistent Myofascial Pain: A Randomized Clinical Trial

This study assessed the safety and efficacy of three different doses of BoNT-A for persistent myofascial pain (MFP). One hundred female subjects were randomly assigned into five groups (n = 20): oral appliance (OA), saline solution (SS) and three BoNT-A groups with different doses. Pain intensity and pressure pain threshold were evaluated up to 24 weeks after treatment. Adverse effects related to muscle contraction, masticatory performance, muscle thickness and mandibular bone volume were also assessed. Changes over time were compared within and between groups. The “nparLD” package and Wilcoxon signed-rank test were used to analyze the data. BoNT-A reduced pain intensity (p < 0.0001) and increased pressure pain threshold (p < 0.0001) for up to 24 weeks compared to the placebo. No differences were found between BoNT-A and OA at the last follow-up. A transient decline in masticatory performance (p < 0.05) and muscle contraction (p < 0.0001), and a decrease in muscle thickness (p < 0.05) and coronoid and condylar process bone volume (p < 0.05) were found as dose-related adverse effects of BoNT-A. Regardless of the dose, BoNT-A was as effective as OA on MFP. Notwithstanding, due to BoNT-A dose-related adverse effects, we suggest the use of low doses of BoNT-A in MFP patients that do not benefit from conservative treatments.

Temporomandibular Disorders and Oral Features in Systemic Lupus Erythematosus Patients: An Observational Study of Symptoms and Signs

Aims: Systemic Lupus Erythematosus (SLE) is a connective tissue disease characterized by a wide range of pleomorphic pictures, including mucocutaneous, renal, musculoskeletal and neurological symptoms. It involves oral tissues, with hyposalivation, tooth decay, gingivitis, angular cheilitis, ulcers and glossitis. Temporomandibular disorders represent a heterogeneous group of inflammatory or degenerative diseases of the stomatognatic system, with algic and/or dysfunctional clinical features involving temporomandibular joint (TMJ) and related masticatory muscles. The aim of this study was to investigate the prevalence of oral manifestations and temporomandibular disorders (TMD) in SLE patients (Lp) compared with a control group. Methods: Fifty-five patients (9 men and 46 women) with diagnosed Lupus were recruited in the study group. A randomly selected group of 55 patients, matched by sex and age, served as control group. The examination for TMD symptoms and signs was based on the standardized Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) through a questionnaire and clinical examination. Results: Lupus patients complained more frequently (95.8%) of oral and TMJ symptoms (dysgeusia, stomatodynia, masticatory muscle pain during function, neck and shoulder muscles pain and presence of tinnitus) but only xerostomia (χ2=4,1548 p=0,0415), temple headache (χ2=4,4542 p=0,035) and the sensation of a stuck jaw (Mid-p-test p=0,043) were significant. About signs, cheilitis (p=0,0284) oral ulcers (χ2=4,0104 p=0,045) and fissured tongue are significantly more frequent in study group. The salivary flow was significantly decreased in the study group respect to the control one (p<0.0001). As regard to the oral kinematics, restricted movements (RM) in protrusion and left lateral movement were significantly different between study group and controls. In particular, 85,2% of Lp showed limited protrusion versus 56,4% of controls (χ2= 10,91 p<0,001); 59,3% of Lp had also a limitation during left lateral movement versus 47,3% of controls (T=2,225 p=0,0282). About bruxism, only the indentations on the lateral edges of the tongue were found in Lp group (72,7%), with a significant difference respect to controls (χ2=7,37 p=0,007). Conclusions: While masticatory muscles have an overlapping behavior in both groups, the findings collected show a more severe TMJ kinematic impairment in Lp than in controls, with protrusion and left lateral movements significantly different. In addition, a remarkable reduction of salivary flow has been detected in Lp compared to controls. In conclusion, this autoimmune disease seems to play a role in oral manifestations and TMJ disorders, causing an increase in orofacial pain and an altered chewing function.

The efficacy of transcranial direct current stimulation and transcranial magnetic stimulation for chronic orofacial pain: A systematic review

BACKGROUND

Transcranial Direct Current Stimulation (tDCS) and Transcranial Magnetic Stimulation (TMS) have been described as promising alternatives to treat different pain syndromes. This study evaluated the effects of TMS and tDCS in the treatment of chronic orofacial pain, through a systematic review.

METHODS

An electronic search was performed in major databases: MEDLINE, Scopus, Web of Science, Cochrane, Embase, LILACS, BBO, Open Gray and CINAHL. The eligibility criteria comprised randomized clinical trials (RCTs) that applied TMS or tDCS to treat chronic orofacial pain. The variables analyzed were pain, functional limitation, quality of life, tolerance to treatment, somatosensory changes, and adverse effects. The risk of bias was assessed through the Cochrane Collaboration tool, and the certainty of evidence was evaluated through GRADE. The protocol was registered in the PROSPERO database (CRD42018090774).

RESULTS

The electronic search resulted in 636 studies. Thereafter, the eligibility criteria were applied and the duplicates removed, resulting in eight RCTs (four TMS and four tDCS). The findings of these studies suggest that rTMS applied to the Motor cortex (M1), the dorsolateral prefrontal cortex (DLPFC) and the secondary somatosensory cortex (S2) provide adequate orofacial pain relief. Two studies reported significant pain improvement with tDCS applied over M1 while the other two failed to demonstrate significant effects compared to placebo.

CONCLUSIONS

rTMS, applied to M1, DLPFC or S2, is a promising approach for the treatment of chronic orofacial pain. Moreover, tDCS targeting M1 seems to be also effective in chronic orofacial pain treatment. The included studies used a wide variety of therapeutic protocols. In addition, most of them used small sample sizes, with a high risk of biases in their methodologies, thus producing a low quality of evidence. The results indicate that further research should be carried out with caution and with better-standardized therapeutic protocols.

Differences between palpation and static/dynamic tests to diagnose painful temporomandibular disorders in patients with Lyme disease

OBJECTIVES

The aim was to determine the frequency of Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD)-based pain diagnoses and dynamic/static tests-based pain diagnoses, and to assess the agreement of palpation tests with static/dynamic tests.

MATERIALS AND METHODS

Eighty-six (N = 86) adult patients with Lyme disease (mean age 57.0 ± 14.3 years; male/female ratio was 42/44) were examined according to techniques described in the RDC/TMD. Additionally, dynamic/static tests were performed. For RDC/TMD-based pain diagnoses and dynamic/static tests-based pain diagnoses, descriptive frequencies were calculated. Differences between the frequency of palpation-based diagnoses and of dynamic/static-based diagnoses as well as the agreement between pain diagnoses established with the two diagnostic approaches were assessed.

RESULTS

RDC/TMD-based pain diagnoses were made in 61 patients for myofascial pain and in 11 patients for arthralgia and/or osteoarthritis. Based on dynamic/static tests, mainly myogenous pain was diagnosed in 6 patients, and a mainly arthrogenous pain in 5. The agreement of palpation tests with static/dynamic tests in Lyme disease population was poor.

CONCLUSION

A high prevalence of TMD symptoms was found in patients with Lyme disease. The results suggest that using palpation tests alone could overestimate primary TMDs when comorbid conditions are present.

CLINICAL RELEVANCE

Dynamic/static tests should be used as part of the routine TMD assessment. In case of Lyme disease as the actual cause of the facial pain, while the dentist might be suspecting TMD when dynamic/static TMD tests are negative, referral to an appropriate specialist for the diagnosis and treatment of Lyme disease needs to be made.

Evidence of Altered Trigeminal Nociception in an Animal Model of Fibromyalgia

Objective

Fibromyalgia (FM) is a debilitating chronic condition that significantly affects quality of life. A strong association has been demonstrated between FM and chronic pain in the trigeminal region in clinical studies. This study was performed to evaluate the response to acute and chronic noxious stimuli applied to the facial region.

Methods

Adult male Wistar rats (250-270 g, N = 10 for each group) were used in the current study. A subchronic swim stress model was used as the animal model of FM. Anxiety-like behaviors and response to acute and chronic noxious stimuli were assayed using the elevated plus maze, eye wiping test, and orofacial formalin test, respectively. Balance and motor function were evaluated using rotarod and wire grip tests.

Results

An increased anxiety-like behavior was observed in swim stress rats in comparison with control and sham subjects. Response to acute and chronic noxious stimuli in the trigeminal region was increased in the stressed rats. Motor and balance function were not altered following stress.

Conclusions

Results of the current study demonstrated a hyperalgesic state in the trigeminal region in a possible animal model of FM. This study provides a reliable animal model for further research on the possible mechanisms of orofacial pain in FM.

Reliability of Mechanical Sensitivity Mapping in the Orofacial Region of Healthy Chinese Individuals: Towards Standardized Assessment of Somatosensory Function

AIMS

To investigate the test-retest reliability of mechanical sensitivity mapping in the masseter and temporomandibular joint (TMJ) regions between sessions, days, and examiners with a fixed and standardized pressure stimulus, as well as to compare mechanical sensitivity between sides and sites.

METHODS

A total of 20 healthy young volunteers participated. Pressure stimulation was applied to 15 sites in the masseter region with a Palpeter device of 1.0-kg force and to 9 sites in the TMJ region with a Palpeter of 0.5-kg force. All participants were tested twice in two separate sessions on the same day by Examiner 1 with an interval of 3 hours between tests. After 1 week, the protocol was repeated in the same manner in two separate sessions by Examiner 1 and Examiner 2 (one session each).

RESULTS

Analysis of variance (ANOVA) of numeric rating scale (NRS) scores and center of gravity (COG) values in both regions showed no significant main effects of examiner, day, or session (P ≥ .167). The test-retest reliability of data implied excellent agreement (intra-class correlation coefficients all > 0.75) between different examiners, days, and sessions. In addition, the ANOVA of the mean NRS scores in both regions showed significant main effects of site (P = .001).

CONCLUSION

This feasible and reliable technique may provide a new tool for comprehensive evaluation of mechanical allodynia and hyperalgesia in the orofacial region, which are common features related to temporomandibular disorders and other chronic craniofacial pain conditions.

Tapentadol in an Experimental Animal Model of Acute Orofacial Pain

OBJECTIVE

Tapentadol exhibits a synergistic dual effect effect (MOR / NRI) -agonist effect on noradrena-line reuptake inhibition (NRI). Tapentadol is effective on pain with neuropathic characteristics, therefore we decided to use it in an experimental model of acute orofacial pain.

METHODS

The Orofacial Stimulation Test, developed by Ugo Basile, measures hypersensitivity to thermal or mechanical stimulation of the trigeminal area. In the experiment, rats had to voluntarily contact a thermal or mechanical stimulator with their unshaved vibrissal pad in order to access a food reward. Twenty adult laboratory rats (average weight 345 grams) were tested. Intraperitoneal tapentadol was used in doses of 1 mg/kg and 2 mg/kg.

RESULTS

The results of the pilot study indicate that intraperitoneal administration of tapentadol (2 mg/kg) increased mechanical anti-nociception in rats.

Association Between Pain Sensitivity and Endogenous Supraspinal Pain Modulation in Patients with Orofacial Pain

Address correspondence to: Dr. Carla S. Enriquez, Physical Therapy Program, Stockton University School of Health Sciences, 101 Vera King Farris Drive, Galloway, NJ 08205-9441, USA. Tel 609-626-3508, fax 609-652-4858. carla.enriquez@stockton.edu.

PURPOSE

To investigate the association between pain sensitivity and endogenous supraspinal pain modulation activity using quantitative sensory tests (QST) in patients with orofacial pain.

METHODS

Temporal summation (TS) testing and conditioned pain modulation (CPM) are QSTs used to quantify individual pain processing mechanisms. TS testing was used to assess pain sensitivity which correlates to central sensitization and CPM for endogenous pain modulation. These tests were administered to a convenience sample of patients with orofacial pain (n=40) seen for initial examination in an orofacial pain clinic. Bivariate correlation analyses were conducted on TS and CPM scores, including age and gender.

RESULTS

A strong linear correlation was found between pain sensitivity and endogenous pain modulation (r=0.69, p<0.001). QST outcomes suggest that inefficient endogenous pain modulation is positively correlated with the magnitude of pain sensitivity among individuals who seek treatment for orofacial pain. A weak linear correlation was also found between TS and age (r=0.37, p=0.02).

CONCLUSION

QSTs demonstrated a strong association between heightened pain sensitivity and inefficient endogenous pain modulation revealed from higher pain report on TS and CPM testing in patients with orofacial pain. Our findings provide supporting evidence on the impairments in pain-processing mechanisms that require consideration when evaluating orofacial pain etiology, where increased pain sensitivity and aberrant pain modulation appear to significantly contribute in prolonged and persistent pain experience.

Sleep and Orofacial Pain

Sleep and pain share a bidirectional relationship. Therefore, it is important for practitioners managing patients experiencing either sleep and/or pain issues to recognize and understand this complex association from a neurobiological perspective involving neuroanatomic and neurochemical processes. Accounting for the influence of pain on the various aspects of sleep and understanding its impact on various orofacial pain disorders assists in developing a prudent management approach. Screening for sleep disorders benefits practitioners in identifying these individuals. Instituting evidence-based multidisciplinary management strategies using both behavioral and pharmacologic strategies enhances the delivery of appropriate care.

Mind-Body Considerations in Orofacial Pain

This article summarizes the cognitive, behavioral, and emotional factors that contribute to the onset and maintenance of orofacial pain. These orofacial pain conditions illustrate the dynamic interplay of the mind and body and the importance of multimodal treatment approaches addressing simultaneously the cognitive, behavioral, and physiologic dimensions of facial pain. Cognitive and behavioral treatments of temporomandibular disorders based on the outcomes of randomized controlled trials are also discussed with an emphasis on using a biopsychosocial perspective when working with the persons who have temporomandibular disorders.

Gender differences in temporomandibular disorders in adult populational studies: A systematic review and meta-analysis

The objective of this study was to systematically evaluate gender differences in the prevalence of TMD. A systematic review was performed in PubMed, EMBASE, Web of Science and LILACS in duplicate by two independent reviewers. The inclusion criteria were cross-sectional studies that reported the prevalence of TMD for men and women and that used the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) Axis I group diagnostic criteria:(group I = muscle disorders; group II = disc displacements; group III = arthralgias/arthritis/arthrosis).To be eligible for inclusion, studies must include adult individuals (>18 years) from a non-clinical population (ie without pre-diagnosis of TMD); in other words, from population-based studies. There were no restrictions on the year and language of publication. The quality of the articles was assessed by an adapted version of the Newcastle-Ottawa Scale(NOS), and the publication bias was assessed by a funnel plot graph. Data were quantitatively analysed by meta-analysis using odds ratio (OR) as the measure effect. The electronic search retrieved a total of 6104 articles, of which 112 articles were selected for full-text reading according to the eligibility criteria. By means of manual search, one study was retrieved. Five articles were selected for meta-analysis with a combined sample of 2518 subjects. Women had higher prevalence of TMD in all RDC/TMD diagnostic groups. The meta-analysis yielded the following results: (a) OR = 2.24 for global TMD (groups I, II and III combined), (b) OR = 2.09 for group I, (c) OR = 1.6 for group II and (d) OR = 2.08 for group III. The importance of gender in the development of TMD has been demonstrated, with a two times greater risk of women to develop it as compared to men.

Electrical Synapses are Involved in Orofacial Neuropathic Pain

Accumulated evidences suggest important roles of glial GAP-junctions in pain. However, only a few studies have explored the role of neuronal GAP-junctions or electrical synapses in neuropathic pain (NP). Therefore, the present study explores the role of connexin 36 (Cx36) in NP using the chronic constriction injury of the infraorbital nerve (CCI-IoN) model in rat. A significant increase in Cx36 labeling was observed in the medullary dorsal horn (MDH) of CCI-IoN-lesioned compared to sham rats. The expression of Cx36 in CCI-IoN-lesioned rats revealed a rostroventral gradient of punctuate labeling within lamina IIo of the MDH. Cx36-positive somata and processes were also observed in MDH laminae IIi and III-V. These somata were mostly of the Gamma aminobutyric acid (GABA) and occasionally Glycine transporter 2 (GlyT2) cell subtypes. Moreover the GABA cell subtypes are highly coupled in lamina IIo as revealed by the intense Cx36 staining in this lamina. Pharmacological Cx36 blockade by intracisternal administration of mefloquine decreased significantly the mechanical allodynia observed in CCI-IoN-lesioned rats. Altogether, our findings demonstrated that Cx36 play an important role in mechanical allodynia by coupling GABA cells. Increasing cell coupling by enhancing Cx36 expression favors neuropathic pain while disrupting this coupling alleviates it. This mechanism may constitute a novel target for the treatment of orofacial mechanical allodynia.

[Electromyographic characteristics of temporal and masticatory muscles in patients with compression-dislocation dysfunction of temporomandibular joints of different severity]

OBJECTIVE

Introduction: The main causes of dysfunctional conditions of the temporomandibular joints (TMJ), are occlusal, neurogenic, orthodontic disorders. The muscular component of TMJ is determines the dynamic anatomical and functional state of the mandible Therefore, in the diagnosis of dysfunctions and understanding of their pathogenesis belongs to the electromyographic method of investigation. The aim of the work was a comparative assessment of the bioelectrical activity of the actual chewing and temporal muscles in patients with musculo-articular compressiondislocation dysfunction of the TMJ of various severity.

PATIENTS AND METHODS

Materials and methods: Electromyographic studies of temporal and masticatory muscles were performed in 43 patients. Was assess maximal parameters were recorded with the greatest compression of teeth and in the periods of chewing on the side of the pain symptom and on the opposite side (μV), the frequency of filling the myogram (Hz), the time of activity (Ta) and the resting time (Tc), coefficient "K", which determines the ratio of the processes of activity and rest with functional samples (K = Ta / Tc).

RESULTS

Results and conclusions: The main feature of the functional properties of the studied muscles in the compression-dislocation dysfunction of the TMJ is the prevalence of the maximum indices of their bioelectrical activity on the side of the joint with the dislocation of the articular head of the mandible in comparison with the joint, which is in a compression state both during periods of compression of the teeth and mastication. This kind of discoordination in the work of the muscular masticatory apparatus is reflected in the severity of the course of dysfunction.

Effect of Testosterone on TRPV1 Expression in a Model of Orofacial Myositis Pain in the Rat

Recent clinical studies have revealed sex differences in response to transient receptor potential vanilloid 1 (TRPV1) agonist-induced pain. However, the mechanism of these differences in TRPV1-related chronic pain remains unclear. In the present study, we investigate the effects of inflammation and gonadal hormones on TRPV1 expression in trigeminal ganglia. Inflammatory pain was modeled by injecting complete Freund's adjuvant (CFA) into the left masseter muscle in rats. TRPV1 mRNA and protein levels in the trigeminal ganglia of male and female rats following CFA injection were assessed. CFA-induced changes in TRPV1 mRNA and protein expression in the trigeminal ganglia from orchidectomized (ODX) male rats and testosterone-replaced ODX rats were examined. Additionally, TRPV1 mRNA levels in the trigeminal ganglia from ovariectomized (OVX) female and ODX male rats treated with tamoxifen were assessed. We found that the levels of TRPV1 mRNA and protein in the trigeminal ganglia from female rats following CFA injection were significantly higher than in the ganglia from naïve female rats. CFA-induced inflammatory hyperalgesia did not alter TRPV1 expression in the trigeminal ganglia from male rats. The TRPV1 mRNA and protein expression levels in the ODX male trigeminal ganglia were significantly upregulated on day 3 following the initiation of inflammation. However, CFA-induced inflammatory pain had no significant effect on TRPV1 mRNA or protein expression in testosterone-replaced ODX rats. Furthermore, tamoxifen was unable to inhibit the upregulation of TRPV1 expression in OVX female and ODX male rats after CFA injection. In summary, these data indicate that gender differences in TRPV1 function may be, in part, mediated by sex-dependent TRPV1 expression in sensory ganglia. Testosterone plays a key role in the inhibition of TRPV1 expression in this rat chronic inflammatory pain model.

Neuron-Glia Crosstalk and Neuropathic Pain: Involvement in the Modulation of Motor Activity in the Orofacial Region

Neuropathic orofacial pain (NOP) is a debilitating condition. Although the pathophysiology remains unclear, accumulating evidence suggests the involvement of multiple mechanisms in the development of neuropathic pain. Recently, glial cells have been shown to play a key pathogenetic role. Nerve injury leads to an immune response near the site of injury. Satellite glial cells are activated in the peripheral ganglia. Various neural and immune mediators, released at the central terminals of primary afferents, lead to the sensitization of postsynaptic neurons and the activation of glia. The activated glia, in turn, release pro-inflammatory factors, further sensitizing the neurons, and resulting in central sensitization. Recently, we observed the involvement of glia in the alteration of orofacial motor activity in NOP. Microglia and astroglia were activated in the trigeminal sensory and motor nuclei, in parallel with altered motor functions and a decreased pain threshold. A microglial blocker attenuated the reduction in pain threshold, reduced the number of activated microglia, and restored motor activity. We also found an involvement of the astroglial glutamate–glutamine shuttle in the trigeminal motor nucleus in the alteration of the jaw reflex. Neuron–glia crosstalk thus plays an important role in the development of pain and altered motor activity in NOP.

Entropy of Masseter Muscle Pain Sensitivity: A New Technique for Pain Assessment

AIMS

To test whether manipulation of mechanical pain sensitivity (MPS) of the masseter muscle is reflected in quantitative measures of entropy.

METHODS

In a randomized, single-blinded, placebo-controlled design, 20 healthy volunteers had glutamate, lidocaine, and isotonic saline injected into the masseter muscle. Self-assessed pain intensity on a numeric rating scale (NRS) was evaluated up to 10 minutes following the injection, and MPS was evaluated after application (at 5 minutes and 30 minutes) of three different forces (0.5 kg, 1 kg, and 2 kg) to 15 different sites of the masseter muscle. Finally, the entropy and center of gravity (COG) of the pain sensitivity scores were calculated. Analysis of variance was used to test differences in means of tested outcomes and Tukey post hoc tests were used to adjust for multiple comparisons.

RESULTS

The main findings were: (1) Compared with both lidocaine and isotonic saline, glutamate injections caused an increase in peak, duration, and area under the NRS pain curve (P < .01); (2) A pressure of 2 kg caused the highest NRS pain scores (P < .03) and entropy values (P < .02); (3) Glutamate injections caused increases in entropy values when assessed with 0.5 kg and 1.0 kg but not with 2.0 kg of pressure; and (4) COG coordinates revealed differences between the x coordinates for time (P < .01) and time and force for the y coordinates (P < .01).

CONCLUSION

These results suggest that manipulation of MPS of the masseter muscle with painful glutamate injections can increase the diversity of MPS, which is reflected in entropy measures. Entropy allows quantification of the diversity of MPS, which may be important in clinical assessment of pain states such as myofascial temporomandibular disorders.

St36 electroacupuncture activates nNOS, iNOS and ATP-sensitive potassium channels to promote orofacial antinociception in rats

Orofacial pain is pain perceived in the face and/or oral cavity, generally caused by diseases or disorders of regional structures, by dysfunction of the nervous system, or through referral from distant sources. Treatment of orofacial pain is mainly pharmacological, but it has increased the number of reports demonstrating great clinical results with the use of non-pharmacological therapies, among them electroacupuncture. However, the mechanisms involved in the electroacupuncture are not well elucidated. Thus, the present study investigate the involvement of the nitric oxide synthase (NOS) and ATP sensitive K⁺ channels (KATP) in the antinociception induced by electroacupuncture (EA) at acupoint St36. Thermal nociception was applied in the vibrissae region of rats, and latency time for face withdrawal was measured. Electrical stimulation of acupoint St36 for 20 minutes reversed the thermal withdrawal latency and this effect was maintained for 150 min. Intraperitoneal administration of specific inhibitors of neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase (iNOS) and a KATP channels blocker reversed the antinociception induced by EA. Furthermore, nitrite concentration in cerebrospinal fluid (CSF) and plasma, increased 4 and 3-fold higher, respectively, after EA. This study suggests that NO participates of antinociception induced by EA by nNOS, iNOS and ATP-sensitive K⁺ channels activation.

[Pathophysiology and treatment of orofacial pain.]

"Pain" is one of body defense mechanisms and crucial for the life support. However, orofacial pain such as myofascial pain syndrome, burning mouth syndrome and trigeminal neuralgia plays no part in body defense mechanisms and requires therapeutic intervention. Recent studies have indicated that plastic changes in the activities of trigeminal neurons, satellite glial cells in trigeminal ganglion, secondary neurons, microglia and astrocytes in trigeminal spinal subnucleus following orofacial inflammation and trigeminal nerve injury are responsible for orofacial pain mechanisms. Clinically, it is well known that the etiologic differential diagnosis which consists of careful history-taking and physical examination is essential for therapeutic decision in patients with orofacial pain. This report outlines the current knowledge on the pathophysiology, diagnosis, treatment of orofacial pain.

Role of diode lasers in oro-facial pain management

With the increasing use of low level laser therapy (LLLT) in clinical dentistry, the aim of the present study was to assess the effectiveness of diode lasers in the management of orofacial pain. Indexed databases were searched without language and time restrictions up to and including July 2016 using different combinations of the following key words: oral, low level laser therapy, dental, pain, diode lasers, discomfort and analgesia. From the literature reviewed it is evident that LLLT is effective compared to traditional procedures in the management of oro-facial pain associated to soft tissue and hard tissue conditions such as premalignant lesions, gingival conditions and dental extractions. However, it remains to be determined which particular wavelength will produce the more favorable and predictable outcome in terms of pain reduction. It is highly recommended that further randomized control trials with well-defined control groups should be performed to determine the precise wavelengths of the diode lasers for the management of oro-facial pain. Within the limits of the present review, it is concluded that diode lasers therapy is more effective in the management of oro-facial pain compared to traditional procedures.

Endurance during Chewing in Whiplash-associated Disorders and TMD

We have previously shown an association between neck injury and disturbed jaw function. This study tested the hypothesis of a relationship between neck injury and impaired endurance during chewing. Fifty patients with whiplash-associated disorders (WAD) were compared with 50 temporomandibular disorders (TMD) patients and 50 healthy subjects. Endurance was evaluated during unilateral chewing of gum for 5 min when participants reported fatigue and pain. Whereas all healthy subjects completed the task, 1/4 of the TMD and a majority of the WAD patients discontinued the task. A majority of the WAD patients also reported fatigue and pain. These findings suggest an association between neck injury and reduced functional capacity of the jaw motor system. From the results, we propose that routine examination of WAD patients should include jaw function and that an endurance test as described in this study could also be a useful tool for non-dental professionals.

Increase of Galanin in Trigeminal Ganglion during Tooth Movement

It is known that nerve fibers containing neuropeptides such as galanin increase in the periodontal ligament during experimental tooth movement. However, the origin of galanin-containing nerve fibers in the periodontal ligament remains unclear. This study was conducted to examine our hypothesis that the increased galanin nerve fibers have a sensory neuronal origin, and that the peptide is associated with pain transmission and/or periodontal ligament remodeling during experimental tooth movement. In control rats, galanin-immunoreactive trigeminal ganglion cells were very rare and were observed predominantly in small ganglion cells. After 3 days of experimental tooth movement, galanin-immunoreactive trigeminal ganglion cells significantly increased, and the most marked increase was observed at 5 days after experimental tooth movement. Furthermore, their cell size spectrum also significantly changed after 3 and 5 days of movement: Medium-sized and large trigeminal ganglion cells began expressing, and continued to express, galanin until 14 days after experimental tooth movement. These findings suggest that the increase of galanin in the periodontal ligament during experimental tooth movement at least partially originates from trigeminal ganglion neurons and may play a role in pain transmission and/or periodontal remodeling.

Orofacial Pain in Cancer: Part I—Mechanisms

The mechanisms involved, and possible treatment targets, in orofacial pain due to cancer are poorly understood. The aim of the first of this two-part series is to review the involved pathophysiological mechanisms and explore their possible roles in the orofacial region. However, there is a lack of relevant research in the trigeminal region, and we have therefore applied data accumulated from experiments on cancer pain mechanisms in rodent spinal models. In the second part, we review the clinical presentation of cancer-associated orofacial pain at various stages: initial diagnosis, during therapy (chemo-, radiotherapy, surgery), and in the post-therapy period. In the present article, we provide a brief outline of trigeminal functional neuro-anatomy and pain-modulatory pathways. Tissue destruction by invasive tumors (or metastases) induces inflammation and nerve damage, with attendant acute pain. In some cases, chronic pain, involving inflammatory and neuropathic mechanisms, may ensue. Distant, painful effects of tumors include paraneoplastic neuropathic syndromes and effects secondary to the release of factors by the tumor (growth factors, cytokines, and enzymes). Additionally, pain is frequent in cancer management protocols (surgery, chemotherapy, and radiotherapy). Understanding the mechanisms involved in cancer-related orofacial pain will enhance patient management.

Noninvasive transcranial direct current stimulation (tDCS) for the treatment of orofacial pain

OBJECTIVE

tDCS is a promising method for the treatment of chronic pain. Electrode placement locations must be chosen in accordance with the density and the time course of the current in order to prevent pathological changes in the underlying tissue. In order to reduce current spatial variability, more electrodes of the same polarity are placed in a circle around the second electrode of the opposite polarity. The applied current produced the greatest changes directly beneath the electrodes: the cathode reduces the excitability of cortical neurons, while the anode has the opposite effect.

METHODS

Based on inclusion criteria, 10 patients with chronic orofacial pain, secondary trigeminal neuralgia after oral surgery, were enrolled and underwent both anode and cathode stimulation. Before the first session we measured pain intensity on a numeric pain rating scale and tactile and thermal stimulation were used to assess somatosensory status. tDCS was applied for five consecutive days. At the end of tDCS application, somatosensory status was assessed again.

RESULTS

From our results we can conclude that the application of tDCS improves the perception of some types of pain. When we increase our sample size, we would expect confirmation not only on our positive results, but also some additional findings for explaining the pathophysiology of orofacial pain. These pathophysiological findings and explanations are very important for the application of tDCS in the treatment of orofacial pain and also for other types of neuropathic pain.

Evidence for the involvement of TNF-α and IL-1β in the antinociceptive and anti-inflammatory activity of Stachys lavandulifolia Vahl. (Lamiaceae) essential oil and (-)-α-bisabolol, its main compound, in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Stachys lavandulifolia Vahl (Lamiaceae) is a medicinal plant widely used in Turkey and Iranian folk medicine due to its analgesic and anti-inflammatory properties, but little is known about its essential oil.

AIM OF THIS STUDY

We studied the antinociceptive and anti-inflammatory effects of S. lavandulifolia essential oil (EOSl) and (-)-α-bisabolol (BIS), its main compound, in algogen-induced orofacial nociceptive behavior in mice, and assessed the possible involvement of pro-inflammatory cytokines in these profiles.

MATERIALS AND METHODS

The GC-FID and GC-MS analysis of EOSl demonstrated the presence of (-)-α-bisabolol (56.4%), bicyclogermacrene (5.3%), δ-cadinene (4.2%) and spathulenol (2.9%) as the main compounds. Male Swiss mice were pretreated with EOSl (25 or 50mg/kg, p.o.), BIS (25 or 50mg/kg, p.o.), morphine (3mg/kg, i.p.) or vehicle (saline 0.9% with two drops of tween 80, 0.2%), before formalin- (20μl, 2%), capsaicin- (20μl, 2.5µg) or glutamate- (20μl, 25Mm) injection into the right upper lip (perinasal area) in mice. The anti-inflammatory profile of EOSl or BIS (50mg/kg) was assessed by the inflammatory response induced by carrageenan (2% in 0.2mL) in mice (pleurisy model).

RESULTS

Our results showed that p.o. treatment with EOSl and BIS displayed significant inhibitory (p<0.05 or p<0.01 or p<0.001) effects in different orofacial pain tests on mice, but BIS proved to be more effective, significantly reducing nociceptive behavior in all tests including both phases of the formalin test. The analgesic effect is not related to any abnormality since EOSl- or BIS-treated mice exhibited no performance alteration in grip strength. Moreover, EOS1 and BIS exhibited a significant anti-inflammatory effect (p<0.001) in the pleurisy model of inflammation, which seems to be related to a significant reduction (p<0.05) of the pro-inflammatory cytokine TNF-α in BIS treatment, and of the pro-inflammatory cytokine IL-1β (p<0.01) in EOS1 treatment.

CONCLUSION

Our results corroborate the use of S. lavandulifolia in traditional medicine as an analgesic and anti-inflammatory, which seems to be related to (-)-α-Bisabolol, the main compound of EOSl.

Orofacial Neuropathic Pain Leads to a Hyporesponsive Barrel Cortex with Enhanced Structural Synaptic Plasticity

Chronic pain is a long-lasting debilitating condition that is particularly difficult to treat due to the lack of identified underlying mechanisms. Although several key contributing processes have been described at the level of the spinal cord, very few studies have investigated the supraspinal mechanisms underlying chronic pain. Using a combination of approaches (cortical intrinsic imaging, immunohistochemical and behavioural analysis), our study aimed to decipher the nature of functional and structural changes in a mouse model of orofacial neuropathic pain, focusing on cortical areas involved in various pain components. Our results show that chronic neuropathic orofacial pain is associated with decreased haemodynamic responsiveness to whisker stimulation in the barrel field cortex. This reduced functional activation is likely due to the increased basal neuronal activity (measured indirectly using cFos and phospho-ERK immunoreactivity) observed in several cortical areas, including the contralateral barrel field, motor and cingulate cortices. In the same animals, immunohistochemical analysis of markers for active pre- or postsynaptic elements (Piccolo and phospho-Cofilin, respectively) revealed an increased immunofluorescence in deep cortical layers of the contralateral barrel field, motor and cingulate cortices. These results suggest that long-lasting orofacial neuropathic pain is associated with exacerbated neuronal activity and synaptic plasticity at the cortical level.

Possible Mechanisms of Pain Perception in Patients with Episodic Tension-Type Headache. A New Experimental Model of Myofascial Pain

A new experimental human model of myofascial pain using intramuscular infusion of a combination of bradykinin, serotonin (5-hydroxytryptamine), histamine, and prostaglandin E2 was applied to patients with episodic tension-type headache (ETTH) in order to examine pain perception. Fifteen patients with ETTH and 15 healthy controls completed the randomized, balanced, double-blinded, placebo-controlled study. Pain intensity, punctate hyperalgesia and allodynia, and pain quality were recorded. The combination induced a moderate and prolonged pain in both patients (median 51 min) ( P = 0.001) and controls (median 22 min) ( P = 0.001). Patients reported more pain than controls both after the combination ( P = 0.045) and after placebo ( P < 0.001). The McGill pain score [PRI(R)] was significantly higher in patients ( P = 0.002) and in controls ( P = 0.001), whereas pain quality and hyperalgesia were similar after the combination compared with placebo in the two groups. Due to side-effects nine subjects did not complete the study. The increased pain response, but similar qualitative pain perception, in ETTH patients may be explained by sensitization of peripheral nociceptors even though central mechanisms may also be involved.

Facial pain in a Neurological Tertiary Care Centre — Evaluation of the International Classification of Headache Disorders

The aim of this study was to examine the diagnostic spectrum of facial pain and to evaluate the clinical features relevant to the differential diagnosis in a neurological tertiary care centre. This is the first investigation comparing the first with the second edition of the International Classification of Headache Disorders (ICHD-I, ICHD-II) in consecutively referred patients comprising a broad spectrum of disorders without restricting the inclusion to certain diagnoses. Studying 97 consecutive patients referred for facial pain, we found trigeminal neuralgia or other types of cranial neuralgia in 38% and 39% according to ICHD-I and ICHD-II, respectively; persistent idiopathic facial pain was diagnosed in 27% and 21%, respectively. The proportion of patients who could not be classified was 24% in ICHD-I and 29% in ICHD-II. Six per cent of the patients had cluster headache or chronic paroxysmal hemicrania, the remaining 5% had various other disorders. The agreement between ICHD-I and ICHD-II was very good to perfect. In ICHD-II, sensitivity and specificity were similar to ICHD-I, the specificity and negative predictive value were imrpoved in single features of trigeminal neuralgia, but were widely unchanged in persistent idiopathic facial pain. The number of patients who could not be classified was larger in ICHD-II than in ICHD-I. Modifying the diagnostic criteria for different types of facial pain, in particular changes in the criteria of persistent idiopathic facial pain, might be helpful in reducing the number of patients with unclassifiable facial pain.

Comparison of Clinical Symptoms and Magnetic Resonance Angiographic (MRA) Results in Patients with Trigeminal Neuralgia and Persistent Idiopathic Facial Pain. Medium-Term Outcome after Microvascular Decompression of Cases with Positive MRA Findings

To evaluate whether NC could be demonstrated preoperatively, high-resolution magnetic resonance angiography (MRA) was performed in 287 consecutive patients with TN and persistent idiopathic facial pain (PIFP) on a 0.5-T and a 1-T MR unit. Depending on the clinical symptoms, the TN cases were divided into typical TN and trigeminal neuralgia with non-neuralgic interparoxysmal pain (TNWIP) groups. Microvascular decompression (MVD) was performed in 103 of the MRA-positive cases. The patients were followed up postoperatively for from 1 to 10 years. The clinical symptoms were compared with the imaging results. The value of MRA was assessed on the basis of the clinical symptoms and surgical findings. The outcome of MVD was graded as excellent, good or poor. The clinical symptoms were compared with the type of vascular compression and the outcome of MVD. The MRA image was positive in 161 (56%) of the 287 cases. There were significant differences between the clinical groups: 66.5% of the typical TN group, 47.5% of the TNWIP group and 3.4% of the PIFP group were positive. The quality of the MR unit significantly determined the ratio of positive/negative MRA results. The surgical findings corresponded with the MRA images. Six patients from the MRA-negative group were operated on for selective rhizotomy and no NC was found. Venous compression of the trigeminal nerve was observed in a significantly higher proportion in the background of TNWIP than in that of typical TN on MRA imaging (24.1% and 0.8%, respectively) and also during MVD (31.2% and 1.2%, respectively). Four years following the MVD, 69% of the patients gave an excellent, 23% a good and 8% a poor result. The rate of some kind of recurrence of pain was 20% in the typical TN and 44% in TNWIP group. The rate of recurrence was 57% when pure venous compression was present. The only patient who was operated on from the PIFP group did not react to the MVD. The clinical symptoms and preoperative MRA performed by at least a 1-T MR unit furnish considerable information, which can play a role in the planning of the treatment of TN.

Pathophysiology and Management of Surgical and Chronic Oral Pain in Dogs and Cats

Pain involves a myriad of physiochemical responses leading to the perception of an unpleasant sensation arising from tissue damage. An understanding of the terminology and basic neurophysiology involved with the pain process is helpful in preventing and treating discomfort in our patients. A general understanding of the concepts of nociception, peripheral sensitization, and central sensitization will allow decisions to be made on the choices of analgesic agents in each individual patient based upon the type, duration, and severity of the pain. Using preemptive pain management with a multimodal approach provides the most consistent and predictable results. Analgesic protocols should be closely scrutinized on an individual basis with careful patient pain assessment during the postoperative period. Chronic pain mechanisms, particularly significant in cancer pain and stomatitis, require aggressive and perhaps unique approaches to ensure maximum patient comfort.

Novel Use of Ultrasound Elastography to Quantify Muscle Tissue Changes After Dry Needling of Myofascial Trigger Points in Patients With Chronic Myofascial Pain

OBJECTIVES

To compare a mechanical heterogeneity index derived from ultrasound vibration elastography with physical findings before and after dry-needling treatment of spontaneously painful active myofascial trigger points in the upper trapezius muscle.

METHODS

Forty-eight patients with chronic myofascial pain enrolled in a prospective interventional trial of 3 weekly dry-needling treatments for active myofascial trigger points. Trigger points were evaluated at baseline and at treatment completion using palpation, the pressure-pain threshold, and the mechanical heterogeneity index. Thirty patients were reevaluated at 8 weeks. Trigger points that "responded" changed to tissue that was no longer spontaneously painful, with or without the presence of a palpable nodule. Trigger points that "resolved" changed to tissue without a palpable nodule. The mechanical heterogeneity index was defined as the proportion of the upper trapezius muscle that appeared mechanically stiffer on elastography. Statistical significance for comparisons was determined at P < .05.

RESULTS

Following 3 dry needle treatments, the mechanical heterogeneity index decreased significantly for the 38 myofascial trigger points (79% of 48) that responded to treatment. Among these, the baseline mechanical heterogeneity index was significantly lower for the 13 trigger points (27% of 38) that resolved, but the decrease after 3 dry needle treatments did not reach significance. The pressure-pain threshold improved significantly for both groups. At 8 weeks, the mechanical heterogeneity index decreased significantly for the 22 trigger points (73% of 30) that responded and for the 10 (45% of 22) that resolved. The pressure-pain threshold improvement was significant for trigger points that responded but did not reach significance for resolved trigger points.

CONCLUSIONS

The mechanical heterogeneity index identifies changes in muscle tissue properties that correlate with changes in the myofascial trigger point status after dry needling.

Zeroing in on the cause of your patient's facial pain

The overlapping characteristics of facial pain can make it difficult to pinpoint the cause. This article, with a handy at-a-glance table, can help.

Analysis of pain in the rabbit temporomandibular joint after unilateral splint placement

AIMS

To determine whether behavioral, anatomical, and physiologic endpoints widely used to infer the presence of pain in rodent models of temporomandibular disorders (TMD) were applicable to the rabbit model of TMD associated with altered joint loading.

METHODS

Unilateral molar dental splints were used to alter temporomandibular joint (TMJ) loading. Changes in nociceptive threshold were assessed with a mechanical probing of the TMJ region on nine splinted and three control rabbits. Fos-like immunoreacitivty in the trigeminal subnucleus caudalis was assessed with standard immunohistochemical techniques from three splinted and six control animals. Retrogradely labeled TMJ afferents were studied with patch-clamp electrophysiologic techniques from three splinted and three control animals. Remodeling of TMJ condyles was assessed by histologic investigations of three splinted and three control animals. A Student t test or a Mann-Whitney U test was used with significance set at P < .05 to compare splinted to control samples.

RESULTS

While variable, there was an increase in mechanical sensitivity in splinted rabbits relative to controls. The increase in Fos+ cells in splinted rabbits was also significant relative to naïve controls (86 ± 8 vs 64 ± 15 cells/section, P < .05). The rheobase (364 ± 80 pA) and action potential threshold (-31.2 ± 2.0 mV) were higher in TMJ afferents from splinted rabbits compared to controls (99 ± 22 pA and -38.0 ± 2.0 mV, P < .05). There was significant remodeling in the condylar fibrocartilage layers as manifested by a change in glycosaminoglycan distribution and a loss of defined cell layers.

CONCLUSION

Behavioral and anatomical results were consistent with an increase in nociceptive signaling in concert with condylar remodeling driven by altered TMJ loading. Changes in excitability and action potential waveform were consistent with possible compensatory changes of TMJ afferents for an overall increase in afferent drive associated with joint degeneration. These compensatory changes may reflect pain-adaption processes that many patients with TMJ disorders experience.

Pain. Part 1: Introduction to pain

This series of papers aims to provide the dental and medical teams with an update in pain, both acute and chronic orofacial conditions, relevant to dentistry and medicine. Pain is the most common symptom for patients presenting to their dentist, and is increasingly commonly presenting to doctors as well, in general practice and A & E departments. Most of the dental team take for granted their knowledge and ability to manage acute dental pain. However, the education and preparation in managing patients with chronic pain conditions remains poor in many medical and dental schools. Conversely, medics are better educated and exposed to chronic pain during their undergraduate education, however, with regards to orofacial pain education, exposure is diminishing due to decreased exposure to dentistry, ENT, otolaryngology, OMFS and oral surgery. Thus many clinical teams remain disadvantaged when diagnosing and managing orofacial pain. Clinical Relevance: Significant advances that have been made in understanding the pain mechanisms are not to be overlooked and have a huge impact on how we manage patients in pain.

A pilot study of ambulatory masticatory muscle activities in temporomandibular joint disorders diagnostic groups

OBJECTIVE

To determine differences in masticatory muscle usage between temporomandibular joint disorders diagnostic groups.

SETTING AND SAMPLE POPULATION

Seventy-one informed and consented subjects (27 men; 44 women) participated at the University at Buffalo.

MATERIAL AND METHODS

Research diagnostic criteria and imaging data were used to categorize subjects according to the presence/absence +/- of TMJ disc placement (DD) and chronic pain (P) (+DD+P, n=18; +DD-P, n=14; -DD-P, n=39). Electromyographic (EMG)/bite-force calibrations determined subject-specific masseter and temporalis muscle activities per 20 N bite-force (T20N , μV). Over 3 days and nights, subjects collected EMG recordings. Duty factors (DFs, % of recording time) were determined based on threshold intervals (5-9, 10-24, 25-49, 50-79, ≥80% T20N ). anova and Tukey-Kramer post hoc tests identified 1) diagnostic group differences in T20N and 2) the effects of diagnostic group, gender, time and interval on muscle DFs.

RESULTS

Mean (±SE) temporalis T20N in +DD+P subjects was significantly higher (71.4±8.8 μV) than masseter T20N in these subjects (19.6±8.8 μV; p=0.001) and in -DD-P subjects (25.3±6.0 μV, p=0.0007). Masseter DFs at 5-9% T20N were significantly higher in +DD-P women (3.48%) than +DD-P men (0.85%) and women and men in both other diagnostic groups (all p<0.03), and in +DD+P women (2.00%) compared to -DD-P men (0.83%; p=0.029). Night-time DFs at 5-9% T20N in +DD-P women (1.97%) were significantly higher than in -DD-P men (0.47%) and women (0.24%; all p<0.01).

CONCLUSIONS

Between-group differences were found in masticatory muscle activities in both laboratory and natural environmental settings.

Diagnostic group differences in temporomandibular joint energy densities

OBJECTIVES

Cartilage fatigue, due to mechanical work, may account for precocious development of degenerative joint disease in the temporomandibular joint (TMJ). This study compared energy densities (mJ/mm³) in TMJs of three diagnostic groups.

SETTING AND SAMPLE POPULATION

Sixty-eight subjects (44 women, 24 men) gave informed consent. Diagnostic criteria for temporomandibular disorders (DC/TMD) and imaging were used to group subjects according to presence of jaw muscle or joint pain (+P) and bilateral disk displacement (+DD).

MATERIAL AND METHODS

Subjects (+P+DD, n=16; -P+DD, n=16; and -P-DD, n=36) provided cone-beam computed tomography and magnetic resonance images, and jaw-tracking data. Numerical modeling was used to determine TMJ loads (Fnormal). Dynamic stereometry was used to characterize individual-specific data of stress-field dynamics during 10 symmetrical jaw-closing cycles. These data were used to estimate tractional forces (Ftraction). Energy densities were then calculated as W/Q (W=work done or mechanical energy input=tractional force×distance of stress-field translation, Q=volume of cartilage). anova and Tukey-Kramer post hoc analyses tested for intergroup differences.

RESULTS

Mean±standard error energy density for the +P+DD group was 12.7±1.5 mJ/mm³ and significantly greater (all adjusted p<0.04) when compared to -P+DD (7.4±1.4 mJ/mm³) and -P-DD (5.8±0.9 mJ/mm³) groups. Energy densities in -P+DD and -P-DD groups were not significantly different.

CONCLUSION

Diagnostic group differences in energy densities suggest that mechanical work may be a unique mechanism, which contributes to cartilage fatigue in subjects with pain and disk displacement.

The impact of cigarette smoking on sleep quality of patients with masticatory myofascial pain

AIM

To evaluate the impact of cigarette smoking on the sleep quality of patients with masticatory myofascial pain and to determine whether the association between smoking and impaired sleep is influenced by other factors such as demographic, psychological, and behavioral variables.

METHODS

Data from a retrospective case series of 529 patients diagnosed with masticatory myofascial pain according to group I of the Research Diagnostic Criteria for Temporomandibular Disorders were obtained. Patients completed a standardized pain questionnaire and psychometric tests. Differences between smokers and nonsmokers were evaluated using independent samples t tests and chi-square tests. Hierarchical linear multiple regression models were used to examine predictors of sleep disturbances.

RESULTS

Of the entire sample, 170 (32%) reported that they were smokers. Smokers reported higher pain severity and more sleep disturbances and psychological distress than nonsmokers. Cigarette smoking significantly predicted sleep disturbance (β = 0.229, P < .001), but this relationship was attenuated after controlling for pain severity and psychological distress (β = 0.122, P < .001).

CONCLUSION

Cigarette smoking is associated with numerous adverse health outcomes, including pain severity, alterations in mood, and disrupted sleep, and seems to be a significant predictor of sleep quality in patients with masticatory myofascial pain.

PKCγ-positive neurons gate light tactile inputs to pain pathway through pERK1/2 neuronal network in trigeminal neuropathic pain model

AIMS

To explore the possible relationship between protein kinase C gamma (PKCγ) and phosphorylated forms of extracellular signal-regulated kinases 1/2 (pERK1/2) in the rat medullary dorsal horn and the facial hypersensitivity indicative of dynamic mechanical allodynia (DMA) following chronic constriction of the infraorbital nerve (CCI-IoN).

METHODS

A well-established rat model of trigeminal neuropathic pain involving CCI-IoN was used. Facial mechanical hypersensitivity was tested with non-noxious dynamic mechanical stimulation (air-puff), and the medullary dorsal horn was examined immunohistochemically using PKCγ and pERK1/2 as pain markers. Statistical analysis was performed using Student t test or one-way analysis of variance (ANOVA).

RESULTS

Increased PKCγ and pERK1/2 expressions within the medullary dorsal horn were associated with DMA following CCI-IoN. A segmental network composed of PKCγ-positive cells located in medullary dorsal horn laminae II/III, contacting more superficially located pERK1/2-expressing cells, was identified. Ultrastructural analysis confirmed the presence of PKCγ to pERK1/2-positive cells. Moreover, intracisternal administration of the selective PKCγ inhibitor KIG31-I blocked both the DMA and pERK1/2 expression in a dose-dependent manner. Although the number of pERK1/2-positive cells was significantly elevated with air-puff stimulation, DMA rats not receiving air-puff stimulation showed significant pERK1/2 expression, suggesting they were experiencing spontaneous pain.

CONCLUSION

PKCγ cells in the medullary dorsal horn may be involved in DMA following CCI-IoN through the activation of pERK1/2-expressing cells, which then may relay non-nociceptive information to lamina I cells in the medullary dorsal horn.

Mechanical and thermal hypersensitivities associated with orthodontic tooth movement: a behavioral rat model for orthodontic tooth movement-induced pain

AIM

To test whether orofacial mechanical and thermal hypersensitivities occur in rats during orthodontic tooth movement (OTM).

METHODS

Sprague-Dawley rats (140 to 160 g) were divided into an experimental (E) group (n =7), with an active orthodontic spring placed in the right side of their mouth, and a sham (S) group (n = 7), with an inactive orthodontic spring. Mechanical sensitivity was tested preoperatively (1 day before attaching the orthodontic spring) and postoperatively (1 hour, 3 hours, 6 hours, days 1 to 7, day 14, day 21, and day 28 after orthodontic spring attachment) on the cheek, upper lip, and maxillary incisor labial gingiva bilaterally by recording the threshold for a head withdrawal response evoked by von Frey filaments. Thermal sensitivity was also tested preoperatively and postoperatively on the cheek bilaterally by applying a noxious thermal stimulus and measuring head withdrawal response duration, response score, and response percentile rate. Statistical analyses involved a mixed-model repeated-measures analysis of variance (MMRM ANOVA).

RESULTS

The mechanical and thermal sensitivities at all bilateral sites were significantly increased (P < .01) in the E group in the early postoperative period (1 to 5 days), with peaks reached on day 1, and then returned to and remained at preoperative levels until postoperative day 28. However, there was no significant change from the preoperative levels in mechanical and thermal sensitivities for the S group for all the tested sites.

CONCLUSION

This rat OTM-induced pain model correlates with the time course of OTM-induced pain in humans and suggests that OTM-induced mechanical and thermal hypersensitivities may be useful measures of OTM-induced pain.

Activation of rostral ventromedial medulla neurons by noxious stimulation of cutaneous and deep craniofacial tissues

The rostral ventromedial medulla (RVM) projects to the medullary and spinal dorsal horns and is a major source of descending modulation of nociceptive transmission. Traditionally, neurons in the RVM are classified functionally as on, off, and neutral cells on the basis of responses to noxious cutaneous stimulation of the tail or hind paw. On cells facilitate nociceptive transmission, off cells are inhibitory, whereas neutral cells are unresponsive to noxious stimuli and their role in pain modulation is unclear. Classification of RVM neurons with respect to stimulation of craniofacial tissues is not well defined. In isoflurane-anesthetized male rats, RVM neurons first were classified as on (25.5%), off (25.5%), or neutral (49%) cells by noxious pinch applied to the hind paw. Pinching the skin overlying the temporomandibular joint (TMJ) altered the proportions of on (39.2%), off (42.2%), and neutral (19.6%) cells. To assess the response of RVM cells to specialized craniofacial inputs, adenosine triphosphate (ATP; 0.01-1 mM) was injected into the TMJ and capsaicin (0.1%) was applied to the ocular surface. TMJ and ocular surface stimulation also resulted in a reduced proportion of neutral cells compared with hind paw pinch. Dose-effect analyses revealed that on and off cells encoded the intra-TMJ concentration of ATP. These results suggest that somatotopy plays a significant role in the functional classification of RVM cells and support the notion that neutral cells likely are subgroups of on and off cells. It is suggested that a portion of RVM neurons serve different functions in modulating craniofacial and spinal pain conditions.

Trigemino-hypoglossal somatic reflex in the pharmacological studies of nociception in orofacial area

Disorders involving the orofacial area represent a major medical and social problem. They are a consequence of central nociceptive processes associated with stimulation of the trigeminal nerve nucleus. A rat model of trigeminal pain, utilizing tongue jerks evoked by electrical tooth pulp stimulation during perfusion of the cerebral ventricles with various neuropeptide solutions, can be used in the pharmacological studies of nociception in orofacial area. The investigated neuropeptides diffuse through the cerebroventricular lining producing an analgesic effect either directly, through the trigemino-hypoglossal reflex arc neurons or indirectly through the periaqueductal central gray, raphe nuclei or locus coeruleus neurons. The aim of this review is to present the effect of pharmacological activity of various neuropeptides affecting the transmission of the sensory information from the orofacial area on the example of trigemino-hypoglossal reflex in rats.