Journal of Oral & Facial Pain and Headache, 04/2011

This article reviews the existing literature of the common anatomic and physiologic aspects of cluster headache and sleep-related breathing disorders to point out evidence suggesting potential therapies beneficial for both maladies. A search of PubMed, as well as relevant textbooks, was conducted using the terms cluster, headache, sleep, apnea, pain, and chronobiology to find any previously published work that may connect the two disorders. Relevant references in the literature were also investigated. As a group, cluster headache patients tend to have a higher incidence of sleep-related breathing disorders as compared to the noncluster headache population. While commonalities in anatomy and physiology exist, robust evidence linking the two disorders is currently lacking. Many people are unaware that they suffer with a sleep-related breathing disorder. The high incidence of these two disorders occurring together should prompt the clinician who treats cluster headache patients to be acutely aware that a yet undiagnosed sleep disorder may also be present. Keywords: cluster headache, hypercapnia, hypoxia, sleep apnea, sleep-related breathing disorders

Aim: To assess the scientific evidence on the efficacy of low-level laser therapy (LLLT) in the treatment of temporomandibular disorders (TMD). Methods: The databases of PubMed, Science Direct, Cochrane Clinical Trials Register, and PEDro were manually and electronically searched up to February 2010. Two independent reviewers screened, extracted, and assessed the quality of the publications. A meta-analysis- was performed to quantify the pooled effect of LLLT on pain and function in patients with chronic TMD. Results: The literature search identified 323 papers without overlap between selected databases, but after the two-phase study selection, only six randomized clinical trials (RCT) were included in the systematic review. The primary outcome of interest was the change in pain from baseline to endpoint. The pooled effect of LLLT on pain, measured through a visual analog scale with a mean difference of 7.77 mm (95% confidence interval [CI]: -2.49 to 18.02), was not statistically significant from placebo. Change from baseline to endpoint of secondary outcomes was 4.04 mm (95% CI 3.06 to 5.02) for mandibular maximum vertical opening; 1.64 mm (95% CI 0.10 to 3.17) for right lateral excursion and 1.90 mm (95% CI: -4.08 to 7.88) for left lateral excursion. Conclusion: Currently, there is no evidence to support the effectiveness of LLLT in the treatment of TMD. Keywords: laser, meta-analysis, systematic review, temporomandibular disorders, temporomandibular joint

Aims: To examine the association between temporomandibular joint (TMJ) symptoms and the global self-rating of oral health, concerns about oral health, and a history of jaw injury or third molar extraction in a representative Korean population. Methods: From the Korean National Oral Health Survey 2006, 4,546 adults aged 18 years and older were included in the analysis. The dependent variable was TMJ symptoms. The independent variables were the global self-rating of oral health, concerns about oral health, and a history of jaw injury or third molar extraction. The demographic information (age and gender), socioeconomic status (education level, monthly household income, vocation, and residence), and behavioral factors (recent dental visit and smoking) were evaluated as confounders. Multivariate linear and logistic regression analyses were applied. Results: The overall prevalence of TMJ symptoms in Koreans was 15.3%. The younger, more educated, middle class, those employed in office and sales, and those who resided in city areas had more TMJ symptoms. The TMJ symptoms were significantly associated with the global self-rating of oral health, concerns about oral health, and history of jaw injury. No significant association was found between the TMJ symptoms and a history of a third molar extraction. The global self-rating of oral health, concerns about oral health, and history of jaw injury had a dose-effect relationship with the severity of TMJ symptoms. Age and gender modified the effect of the global self-rating of oral health, concerns about oral health, and the history of jaw injury on TMJ symptoms. Conclusion: The global self-rating of oral health, concerns about oral health, and a history of jaw injury might be associated with TMJ symptoms. Keywords: jaw injury, self-rated oral health, temporomandibular joint disorders, third molar removal

Aims: To determine in a representative sample of the Australian adult population the relationship between age, gender, and two components of perceived stress (distress and control) and to investigate whether the relationship of perceived stress and temporomandibular disorder (TMD)-related orofacial pain symptoms was modified by gender or age. Methods: Data were from the National Survey of Adult Oral Health conducted in Australia in 2004-2006 and were collected from 3,954 adults aged 18 to 91 years. TMD-related orofacial pain symptoms were evaluated using seven validated screening questions. Perceived stress was measured with the 14-item Perceived Stress Scale and was investigated to empirically test its two theoretical components (distress and sense of control), using principal components analysis. Results: Prevalence of TMD-related orofacial pain symptoms was 10.1% in the Australian adult population. Prevalence was higher in females than in males, inversely related to age, and positively related to distress and current cigarette smoking. Principal component analysis confirmed the theoretical presence of two factors labeled here as distress and control. An inverse relationship of age and distress was more pronounced in females than in males (P value for interaction = .005). In the adjusted binary logistic regression model, age, smoking, and distress remained positively associated with symptoms. A sense of control was protective against TMD-related orofacial pain symptoms, but only for males (P value for interaction = .040). Conclusion: The higher prevalence of TMD-related orofacial pain symptoms in females was better explained by their lower perception of control than from a greater perception of distress. Keywords: effect modification, emotional stress, facial pain, population-based study, sex

Aims: To determine the efficacy in pain reduction of a topical 1% lidocaine compared to a placebo cream in patients with oral mucosal lesions due to trauma or minor oral aphthous ulcer. Methods: The design was a double-blind, randomized, placebo-controlled, six-center trial on 59 patients. Pain intensity and relief were measured using a 100-mm visual analog scale (VAS). One-tailed Student t test and ANOVA analyses were used for statistical analyses. Results: Independent of the pain origin (oral mucosal trauma or minor oral aphthous ulcer), the application of the 1% lidocaine cream led to a mean reduction in VAS pain intensity of 29.4 mm ± 17.0, which was significantly greater than the decrease obtained with the placebo cream. Analysis showed a statistically significant efficacy of the 1% lidocaine cream (P = .0003). Its efficacy was not related to the type of lesion, and no adverse drug reaction, either local or systemic, was reported by any of the patients. Conclusion: A significant reduction in pain intensity occurred after application of 1% lidocaine cream and was significantly greater than that with the placebo cream. Taking into account the study's limitations, this product seems safe to use. Keywords: acute pain, aphthous, lidocaine, mucosal trauma, topical

Aims: To describe the cause, clinical signs, and symptoms of patients presenting to a tertiary care center with iatrogenic lesions to the mandibular branches of the trigeminal nerve. Methods: Pain history, pain scores using the visual analog scale, and mechanosensory testing results were recorded from 93 patients with iatrogenic lingual nerve injuries (LNI) and 90 patients with iatrogenic inferior alveolar nerve injuries (IANI). Results were analyzed using the SPSS statistical software. Chi-square tests were applied for nonparametric testing of frequencies, where P = .05 indicated statistical significance. Appropriate correlations were also carried out between certain data sets. Results: Significantly more females were referred than males (P .05). Overall, third molar surgery (TMS) caused 73% of LNI, followed by local anesthesia (LA) (17%). More diverse procedures caused IANI, including TMS (60%), LA (19%), implants (18%), and endodontics (8%). Approximately 70% of patients presented with neuropathic pain coincident with anesthesia and/or paresthesia. Neuropathy was demonstrable in all patients with varying degrees of loss of mechanosensory function, paresthesia, dysesthesia, allodynia, and hyperalgesia. Functionally, IANI and LNI patients mostly had problems with speech and eating, where speech was affected amongst significantly more patients with LNI (P .001). Sleep, brushing teeth, and drinking were significantly more problematic for IANI patients (P .05, P .001, and P .0001, respectively). Conclusion: Neuropathic pain, as well as anesthesia, frequently occurs following iatrogenic trigeminal nerve injury similar to other posttraumatic sensory nerve injuries. This must be acknowledged by clinicians as a relatively common problem and informed consent appropriately formulated for patients at risk of trigeminal nerve injuries in relation to dentistry requires revision. Keywords: anesthesia, neuropathic pain, paresthesia, trigeminal nerve injury

Aims: To use the ultrashort time-to-echo magnetic resonance imaging (UTE MRI) technique to quantify short T2* properties (obtained through gradient echo) of a disc from the human temporomandibular joint (TMJ) and to corroborate regional T2* values with biomechanical properties and histologic appearance of the discal tissues. Methods: A cadaveric human TMJ was sliced sagittally and imaged by conventional and UTE MRI techniques. The slices were then subjected to either biomechanical indentation testing or histologic evaluation, and linear regression was used for comparison to T2* maps obtained from UTE MRI data. Feasibility of in vivo UTE MRI was assessed in two human volunteers. Results: The UTE MRI technique of the specimens provided images of the TMJ disc with greater signal-to-noise ratio (~3 fold) and contrast against surrounding tissues than conventional techniques. Higher T2* values correlated with lower indentation stiffness (softer) and less collagen organization as indicated by polarized light microscopy. T2* values were also obtained from the volunteers. Conclusion: UTE MRI facilitates quantitative characterization of TMJ discs, which may reflect structural and functional properties related to TMJ dysfunction. Keywords: indentation, magnetic resonance imaging, osteoarthritis, temporomandibular joint disc, ultrashort time-to-echo

Aims: To develop a behavioral model in mice that is capable of mimicking some distinctive symptoms of human posttraumatic trigeminal neuropathic pain such as spontaneous pain, cold allodynia, and chemical/inflammatory hyperalgesia, and to use this model to investigate the antinociceptive effects of clomipramine and tramadol, two drugs used for the treatment of neuropathic pain. Methods: A partial tight ligature of the right infraorbital nerve by an intraoral access or a sham procedure was performed. Fourteen days later, mice were subcutaneously injected with saline or drugs and the spontaneous nociceptive behavior, as well as the responses to topical acetone and to formalin or capsaicin injected into the ipsilateral vibrissal pad, were assessed. Data were analyzed by ANOVA. Results: Neuropathic mice exhibited an increased spontaneous rubbing/scratching of the ipsilateral vibrissal pad, together with enhanced responses to cooling (acetone) and the chemical irritants (formalin, capsaicin). Clomipramine and tramadol produced an antihyperalgesic effect on most of these nociceptive responses, but tramadol was ineffective on capsaicin-induced hyperalgesia. Conclusion: Nociceptive responses in this neuropathic pain model in mice exhibited a pattern consistent with the pain described by posttraumatic trigeminal neuropathic patients. The selective antihyperalgesic effect obtained with two commonly used drugs for treating neuropathic pain confirms the validity of this preclinical model. Keywords: clomipramine, infraorbital nerve ligation, mice, neuropathic trigeminal pain, tramadol

Aims: To investigate systematically whether conditioned pain modulation (CPM) evoked by tonic mechanical stimuli applied to the craniofacial region is intensity-, assessment site-, and gender-dependent. Methods: Twenty healthy men and 20 women participated in four sessions. Tonic painful mechanical stimulation was applied to pericranial muscles by a mechanical headband pressure device. The pressures applied to four probes were adjusted via pain feedback from a 0 to 10 electronic visual analog scale (VAS) to generate different pain levels (VAS0, VAS1, VAS3, or VAS5) for 10 minutes. Pressure pain thresholds (PPTs) and pressure pain tolerance thresholds (PPTols) were assessed from right masseter muscle and left forearm by pressure algometry before, during, immediately after, 10 minutes after, and 20 minutes after the conditioning stimulus (CS). Data were analyzed with multilevel ANOVAs. Results: PPT values normalized to baseline recordings were not dependent on gender or assessment site, but dependent on intensity (P .001) and time (P .001). The most painful CS (VAS5) was associated with the highest PPT increases (32.6% ± 3.3%, mean value for the two assessment sites and two genders) during CS compared to all other intensities of CS (P .001). PPTol values normalized to baseline recordings were also not dependent on gender or assessment site, but dependent on intensity (P .001) and time (P .001). The most painful CS (VAS5) was associated with higher PPTol increases (11.2% ± 2.8%, mean value for the two assessment sites and two genders) during CS (P .001). Conclusion: CPM evoked by mechanical stimulation of the craniofacial region is intensity-dependent but not assessment site- or gender-dependent. Keywords: conditioned pain modulation (CPM), diffuse noxious inhibitory control (DNIC), experimental craniofacial pain, gender differences, trigeminal system