Focal Myositis of the Masseter Muscle Masquerading as Temporomandibular Disorder: Diagnostic Challenges and Management

The Journal of Orthopaedic & Sports Physical Therapy is pleased to publish selected abstracts of the Congresso Internacional de Reabilitação Neuromusculoesquelética e Esportiva, which took place in Vitória, Brazil, May 18 to 21, 2011. This collection of abstracts provides a brief summary of the research presented at that meeting. These abstracts do not permit a full evaluation of the scientific rigor with which the work was conducted, but they provide an idea of the type of clinical questions being researched by individuals participating in that meeting. J Orthop Sports Phys Ther 2011;41(10):A1–A4. doi:10.2519/jospt.2011.0301

BackgroundThe aim of the present study was to analyse the influence of temporomandibular disorder (TMD) on electromyographic activity in the masseter and temporal muscles of adolescents and investigate a possible association with the number of occlusal contacts.MethodsThe Helkimo Index was administered for the diagnosis of TMD and classification of the adolescents into three groups: without TMD; with mild TMD; and with moderate/severe TMD. Carbon paper was used for the determination of occlusal contact points. A standardised electromyographic evaluation was performed on the masticatory muscles at rest, during habitual chewing and during maximum voluntary clenching. The readings were normalised to maximum voluntary clenching. Statistical analysis involved the chi-squared test and Fisher’s exact test. The Kruskal-Wallis test and one-way analysis of variance with Dunn’s post hoc test were used to compare differences between groups. Pearson’s correlation coefficients (r) were calculated for the determination of correlations between the number of occlusal contacts and RMS values.ResultsElectromyography revealed significant differences in the right and left masseter and temporal muscles at rest and during chewing among the three groups. These differences were not observed during maximum voluntary clenching. No statistically significant differences were found between the groups with and without TMD regarding the number of occlusal contacts.ConclusionElectromyographic activity in the masseter and temporal muscles was greater among adolescents with moderate to severe TMD.

Differential diagnosis of facial pain and guidelines for management

Immediate effects of rhythmic joint mobilization of the temporomandibular joint on pain, mouth opening and electromyographic activity in patients with temporomandibular disorders

To explore the effects of head and neck posture training on the electrical activity of the temporalis and masseter muscles in patients with myogenic temporomandibular disorder(TMD) under different head and neck postures. Fourteen patients with TMD who attended Hainan West Central Hospital from July 2022 to February 2023 with presence of head forward posture were selected for the study. All patients received head and neck posture training for 4 weeks, 2-3 times per week for 30 min each time. Changes in the electrical activity of bilateral temporalis and masseter muscles were compared between pre- and post-intervention patients in the natural relaxed position, the teeth lightly touching position, and the neutral head and neck position. Mandibular function, pain intensity, and maximal pain-free mouth opening were assessed for pre- and post-comparisons. In TMD patients, the electromyographic amplitude of the anterior fasciculus of the left temporalis muscle and the right masseter muscle was higher in the natural relaxed position than in the neutral head and neck position (3.4±1.4 vs. 2.5±1.0, 2.4±1.6 vs. 1.8±1.1, P＜0.05). After head and neck posture training, the patients had lower basal EMG amplitudes of bilateral temporalis and left masseter muscles in the natural relaxed position and the neutral head and neck position compared with the pre-treatment position, and the mandibular function scores and pain were significantly improved(P＜0.05). Different head and neck postures can affect the basal electromyographic amplitude of the masticatory muscles in patients with myogenic TMD, and postural training can effectively relax the temporalis and masseter muscles in patients with TMD, resulting in pain reduction and promoting functional recovery.

Context: Temporomandibular disorders are musculoskeletal condition presenting with pain and dysfunction in masticatory muscles, temporomandibular joint (TMJ) and related structure. Aim: To determine the role of myofascial release technique on mobility and function in TMJ Disorder patients with neck pain. Settings and Design: Experimental study design conducted in Dr. D.Y. Patil College of Physiotherapy, Pimpri, Pune. Subjects and Methods: Overall 30 subjects who fulfilled the inclusion criteria were randomly divided into two groups. Experimental group (Group A) was given nonsteroidal anti-inflammatory drugs (NSAID's) and myofascial release to Upper trapezius, Sternocleidomastoid, Masseter and Temporalis three times a week for 2 weeks. Control group (Group B) was given NSAID's. At the end of treatment prepost comparison was done for temporomandibular (TM) joint range of motion and function. Statistical Analysis Used: Data was analysed with Primer software using Wilcoxon signed rank sum test and Mann–Whitney U-test. Results: Mobility in terms of mouth opening and lateral excursion post intervention in both groups have been significantly improved, however, in the experimental group significant improvement was seen in lateral excursions only. Limitation of daily function score reduced from 22.2 to 5 in the experimental; group and 21.3–13.5 in the control group. However more statistical reduction was seen in the experimental group (P = 0.001). Conclusions: Myofascial release technique along with NSAIDSs was able to improve mobility and function among the TM joint disorder patients with neck pain.

Introduction: Temporomandibular disorders (TMDs) are non-dental orofacial pain conditions with a high prevalence in the general population (5-12%). One of the clinical peculiarities is the fact that TMD is often associated with various changes in mechanical pain sensitivity (MPS) at the level of the structures of the stomatognathic system (temporomandibular joint, masticatory muscles), which has the impact of increasing the difficulties of diagnosing this problem for the clinicians. Objective of the study: to evaluate options for clinical investigation of the expression and spatial distribution of mechanical pain sensitivity (MPS) in temporomandibular disorders. Material and methods: We performed the analysis of the variation in the expression of mechanical pain sensitivity (MPS) based on the data obtained by algometry (thresholds of sensitivity/tolerance to pressure) collected in 55 patients. The investigation was carried out in the projection of acupuncture points ST6 (masseter muscle), ST7 (temporomandibular joint). Data collection was carried out in 2 states (relative rest conditions, operational stress modeling). The investigation of the spatial distribution of mechanical pain sensitivity (MPS) was carried out through pain maps at the level of the masseter muscle (30 patients with temporomandibular disorders and 30 asymptomatic people - control group). Results: In the study, it was identified that the expression of mechanical pain sensitivity (MPS) varies according to the test conditions (relative rest/modeled operational stress), being attested statistically significant reductions at the masseter muscle level (tolerance threshold and sensitivity/tolerance threshold ratio) under stress conditions. This state reveals a hypoalgesia occurring after the stressful event, which reflects the complexity of the mechanisms involved in the pathogenesis and evolution of TMD. The observed spatial distribution of mechanical pain sensitivity (MPS) revealed the importance of using complex synthetic indices, which allow the processing of raw data (sensitivity/tolerance thresholds), including the reflection at the level of MPS heterogeneity/homogeneity. Conclusions: Investigating the particularities of mechanical pain sensitivity at the level of the stomatognathic structure, especially masticatory muscles in temporomandibular disorders, which represent a reliable interdisciplinary approach, which requires investigation in multiple standardized conditions (relative comfort/operational stress modeling), with the evaluation of the sensitivity distribution (pain maps). The integral view of TMD through the prism of MPS aspects provides new clinical evaluation criteria (expression intensity, spatial distribution, heterogeneity).

(1) Background: A sedentary lifestyle may aggravate temporomandibular disorder (TMD) symptoms, increasing pain sensitivity and functional limitations. Physical exercise is recommended for pain management and improving quality of life. Comparing CrossFit® athletes to sedentary individuals allows for examining whether regular high-intensity exercise impacts pain sensitivity and functional limitations associated with TMD. This cross-sectional study assessed the signs and symptoms of TMD in CrossFit® athletes compared to sedentary individuals. (2) Methods: Participants (n = 121) were divided into four groups: sedentary with TMD (n = 39), sedentary without TMD (n = 37), CrossFit® athletes with TMD (n = 23), and CrossFit® athletes without TMD (n = 22). TMD signs and symptoms were evaluated using the Research Diagnostic Criteria for TMD (RDC/TMD) axis I, including mandibular movement patterns, range of motion, joint sounds, muscle pain, and jaw dysfunctions. Statistical analyses included chi-square and Dunn's post hoc tests, ANOVA, and Kruskal-Wallis tests. Correlation and regression analyses were performed to examine associations between CrossFit® practice and TMD (p ≤ 0.05). (3) Results: Myofascial pain was the most common diagnosis. All athlete groups exhibited greater mandibular movement amplitudes (unassisted opening without pain, p < 0.001, and protrusion, p = 0.039) and less pain (p < 0.001) than sedentary individuals. Pain reports and palpation-induced pain in muscles and joints were significantly associated with a sedentary lifestyle and TMD (p < 0.001). Joint and muscle pain were more prevalent (frequent) among sedentary participants, regardless of TMD diagnosis. Linear regression analysis showed that sedentary individuals without TMD had significantly reduced unassisted mouth opening amplitudes compared to athletes without TMD (p < 0.05). (4) Conclusions: Pain in the masseter, temporalis, posterior digastric, and medial pterygoid muscles was the most common symptom in sedentary individuals with TMD. They experience higher frequency and intensity of pain, as well as greater limitations in mouth movement. Athletes showed higher frequency of joint noises.

Role of the masseter, anterior temporalis, and sternocleidomastoid muscles in myofascial temporomandibular disorder pain: evaluation of thickness and stiffness by ultrasonography.

Temporomandibular disorder (TMD) is a collective term that encompasses a set of clinical problems that affect the masticatory muscles, the temporomandibular joint, and associated structures. Despite their high clinical prevalence, the mechanisms of chronic craniofacial muscle pain are not yet well understood. Treatments for TMD pain relief and control should be minimally invasive, reversible, and conservative. Photobiomodulation (PBM) is a promising option once it is known to inhibit inflammatory response and to relief painful symptoms. Herein, the effects of PBM (660nm, 30mW, 16J/cm2, 0.2cm2, 15s in a continuous frequency) on the pain sensitivity of rats submitted to an experimental model of TMD induced by CFA was evaluated. Experimental TMD was induced in rats by the injection of complete Freund's adjuvant (CFA) injection into the masseter muscle. Nociceptive behavior was evaluated by electronic von Frey before CFA and after 1h, 3h, 6h, and 24h and 7, 14, and 21days after PBM treatment. Inflammatory infiltrate was evaluated by histology of the masseter muscle and fractalkine expression was evaluated by immunohistochemistry of the trigeminal ganglia. PBM reversed the mechanical hypersensitivity of the animals by inhibiting the local inflammatory response, observed by the decrease of the inflammatory infiltrate in the masseter muscle of rats and by a central inhibition of fractalkine observed in the trigeminal ganglion. These data provide new insights into the mechanisms involved in the effects of photobiomodulation therapy emphasizing its therapeutic potential in the treatment of TMD.

This article describes two cases of masseteric nerve neurectomy with radiofrequency done with the intention to treat temporomandibular disorders and related symptoms; the patients then visited our clinic complaining of side-effects after the procedure. A literature review was conducted to find scientific evidence relevant to masseteric nerve neurectomy with radiofrequency. A 21-year-old male patient visited with the chief complaint of swelling of both cheeks, dizziness, and generalized lethargy occurring after masseteric nerve neurectomy using radiofrequency. His mouth opening range was restricted. Magnetic resonance imaging indicated post-procedural inflammation with hemorrhage within both masseter muscles. A 28-year-old male patient visited with the chief complaint of occlusal discomfort and disocclusion after masseteric nerve neurectomy using radiofrequency. His occlusion was abnormal with only both second molars occluding. Overbite was −1 mm. Cone-beam computed tomography indicated degenerative joint disease of both condyles. In case 1, pharmacotherapy and physical therapy relieved overall symptoms. In case 2, although exacerbation of symptoms repeatedly occurred, long-term stabilization splint and physical therapy alleviated the temporomandibular disorders symptoms. However, the occlusion remained unstable. Scientific evidence of masseteric nerve neurectomy using radiofrequency for the treatment of temporomandibular disorders is still lacking. Therefore, conservative treatment should remain as the first line approach for temporomandibular disorders.

Electromyographic studies have been conducted on the time factors of the silent periods that occur during chin tapping with a view to utilizing these factors as criteria for prosthetic treatment.In the present study, the authors examined the relationship between the time factors of such silent periods and the activity of temporal muscles, masseter muscles, and bite force in normal subjects.The findings are as follows:1. The time factors of the chin tap silent periods varied greatly depending upon subjects.2. At a time when the bite force of each subject reached the maximum, there was a great difference in their muscle activity, ranging from 40 to 190μv.3. Any significant difference was not observed in the relations between the time factors of the chin tap silent periods and muscle activity.4. The relations between the time factors of the chin tap silent periods and bite force showed highly significant differences with respect to latency (L), duration (D) and L+D. As the bite force decreased, L shortened while D and L+D lengthened.5. Patients with temporomandibular joint (TMJ) dysfunction have a weak bite force. However, it remains to be seen whether changes in the time factors of the silent period in the people examined are comparable to those in the patients with TMJ dysfunction.

the incidence and duration of the masseteric silent period (SP) during tooth tapping. Six subjects (5 males and 1 female, 24 to 27 years in age) with normal occlusion and no signs of temporomandibular joint (TMJ) syndrome were investigated. Electromyographic recordings were made from their masseter muscles with bipolar surface electrodes. The TA induced by the occlusal contact during tooth tapping was recorded with an accelero-pickup placed on the forehead of the subject. The following results and conclusion were obtained: 1. The incidence of the SP decreased according to the decrease of TA. A marked reduction of less than 0. 3 G of TA was observed. 2. The duration of the SP increased according to the decrease of TA. The relationship between the duration of the SP and TA could be approximated with a logarithmic function. 3. The relationship between the TA and the incidence or the duration of the SP can be useful for the diagnosis of the masticatory system and TMJ syndrome.

Despite the association of masticatory function with head posture and mandible movement, the impact of head posture on masseter muscle electrical activity remains unclear. This study aimed to investigate the electrical activity of the anterior temporal, masseter, superior trapezius, and sternocleidomastoid muscles in temporomandibular disorder (TMD) patients in three different head positions and compare the findings with those for healthy subjects. The study included 16 TMD patients and 17 healthy subjects. Surface electromyography (sEMG) was used to assess the bilateral anterior temporalis, masseter, superior trapezius, and sternocleidomastoid muscle activities. The maximal voluntary contraction (MVC) and root mean square (RMS) sequence of each muscle were measured in three head positions. Mixed analysis of variance was used to evaluate the effects of head posture on muscle electrical activity in each group. The group differences for the bilateral masseter muscles were significant in the relaxation position, neutral head position (NHP), and relaxation position with tooth contact (P<0.05). In both groups, the basal RMSs of the bilateral anterior temporalis muscle in the relaxation position with tooth contact was significantly higher than that in the NHP (P<0.05). In both groups, the basal RMSs of the bilateral masseter muscles in the relaxation position with tooth contact was higher than that in the relaxation position and NHP, with significant differences (P<0.05). During the management of TMD patients, physical therapists should focus on patient education regarding maintenance of a relaxed position and establish appropriate rehabilitation programs to reduce muscle activity.

There is no consensus on the role of electromyographic analysis in detecting and characterizing the asymmetries of jaw muscle excitation in patients with temporomandibular disorders (TMD). To analyze the TMD patients (n = 72) in comparison with the healthy controls (n = 30), the surface electromyography (sEMG) of the temporalis anterior muscle (TA) and masseter muscle (M) was recorded while a maximal biting task was performed. The differences in the asymmetry of the relationship between the masseter muscles were assessed in a module to determine the sensitivity (Sn) of binomial logistic models, based on the dominance of the TA or the M muscle, in accurately predicting the presence of TMD. All assumptions were met, and comparisons between the groups showed significant differences for the TA muscle ratio (p = 0.007), but not for the M muscle ratio (p = 0.13). The left side was predominant over the right side in the TMD group for both the TA (p = 0.02) and M muscles (p = 0.001), while the non-TMD group had a higher frequency of the right side. Binary logistic regression showed a significant model (χ2 = 9.53; p = 0.002) for the TA muscle with Sn = 0.843. The model for the M muscle also showed significance (χ2 = 8.03; p = 0.005) with Sn = 0.837. The TMD patients showed an increased TA muscle ratio and asymmetry of left dominance, compared to the healthy subjects. Both of the binomial logistic models, based on muscle dominance TA or M, were moderately sensitive for predicting the presence of TMD.