Shear wave elastography of temporomandibular joint disc and masseter muscle stiffness in healthy children and adolescents: a preliminary study

Ultrasound Elastography in Temporomandibular Disorders: A Narrative Review

A class of intricate musculoskeletal diseases known as temporomandibular disorders (TMDs) affects the temporomandibular joint (TMJ) and its supporting structures. The majority of individuals will at some point in their lives experience some degree of TMD symptoms, as these diseases are highly prevalent in the general population. TMDs are multifactorial and are attributed to various physical and biopsychosocial factors. The TMD patients typically experience preauricular pain, tenderness of masticatory muscles, and joint sounds, and these in turn affect their quality of life. To carry out the appropriate course of treatment, it is critical to make an accurate and timely diagnosis. The TMDs are classified as myofascial pain, internal disc derangement, and degenerative disorders of TMJ. Myofascial pain, which is identified by palpating the affected muscles of mastication and tenderness, is one of the most common findings. The muscles in this condition become stiff due to the contraction of myofibrils and are known as trigger bands. The diagnosis of trigger bands involving the masticatory muscles commonly involving the masseter muscle in myofascial pain to date is subjective, and palpation is the only tool used for its diagnosis. An objective assessment of the masticatory muscles is desirable for accurate diagnosis and treatment planning. Various tools like electromyography and hardness meters have been for assessing muscle stiffness, but their application in TMJ muscle disorders has not yielded valuable results. A novel diagnostic method called ultrasound elastography evaluates muscle stiffness both qualitatively and quantitatively using an elastogram and the muscular elasticity index. In this paper, we will review the ultrasound elastographic techniques utilized for the diagnosis and management of TMDs.

The role of scoliosis on temporomandibular joint disease: a cross-sectional study based on ultrasonography

AIM

To investigate the relationship between temporomandibular disorders (TMD) and the stomatognathic system and spine through a multidisciplinary approach, utilising ultrasound to assess the temporomandibular joint.

MATERIALS AND METHODS

Between October 2020 and January 2021, 50 patients aged 12-18 years with adolescent idiopathic scoliosis and 50 healthy individuals were enrolled. All participants underwent clinical examinations based on the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) protocol. Additionally, ultrasound evaluations were performed of the temporomandibular joint and masseter muscles. Subsequently, the data from both groups were compared and analysed.

RESULTS

The mean age of participants was 14.69 ± 2.73 years in the scoliosis group (SG) and 14.68 ± 1.81 years in the control group (CG). Among scoliosis patients, a moderate negative correlation was observed between the Cobb angle (indicative of curvature severity) and mouth opening (p=0.023; r=-0.320). Furthermore, the incidence of TMD was significantly higher in the scoliosis group compared to the control group (p<0.001). Additionally, it was found that a 1-unit increase in joint space elastography value led to a 4.81-fold higher likelihood of diagnosing disc displacement with reduction (p=0.009; 95% CI: 1.47-15.73).

CONCLUSION

This pioneering study, the first of its kind to explore the connection between scoliosis and ultrasound-based temporomandibular joint screening, suggests that scoliosis may be a predisposing factor for TMD. Moreover, the present findings underscore the importance of joint elastography as a valuable quantitative tool in TMD diagnosis.

Determination of masseter and temporal muscle thickness by ultrasound and muscle hardness by shear wave elastography in healthy adults as reference values

OBJECTIVES

The purpose of this study is to prospectively investigate the reference values of masseter and temporal muscle thicknesses by ultrasonography and muscle hardness values by shear wave elastography in healthy adults.

METHODS

The sample of the study consisted of a total of 160 healthy individuals aged between 18 and 59, including 80 women and 80 men. By examining the right and left sides of each participant, thickness and hardness values were obtained for 320 masseter muscles and 320 temporal muscles in total.

RESULTS

The mean masseter muscle thickness was found to be 1.09 cm at rest and 1.40 cm in contraction. The mean temporal muscle thickness was found to be 0.88 cm at rest and 0.98 cm in contraction. The thickness values of the masseter and temporal muscles were significantly greater in the male participants than in the female participants (P < .001). While there were significant differences between the right and left masseter muscle thickness values at rest and in contraction, the values of the temporal muscles did not show a significant difference between the sides. While the resting hardness (rSWE) of the masseter muscle was transversally 6.91 kPa and longitudinally 8.49 kPa, these values in contraction (cSWE) were found, respectively, 31.40 and 35.65 kPa. The median temporal muscle hardness values were 8.84 kPa at rest and 20.43 kPa in contraction. Masseter and temporal muscle hardness values at rest and in contraction were significantly higher among the male participants compared to the female participants (P < .001).

CONCLUSION

In this study, reference values for the thickness and hardness of the masseter and temporal muscles are reported. Knowing these values will make it easier to assess pain in the masseter and temporal muscles and determine the diagnosis and prognosis of masticatory muscle pathologies by allowing the morphological and functional assessments of these muscles, and it will identify ranges for reference parameters.

Ultrasound Elastography in Children

Ultrasound elastography is a novel ultrasound technique, being extensively researched in children in the last decade. It measures tissue elasticity with the observation of tissue response after an external stimulus. From research to clinical practice, ultrasound elastography has evolved significantly in liver fibrosis evaluation in children; however, several other applications of the technique are available in both clinical practice and research environments. Practically, in children any organ can be assessed, including the brain in early ages, along with muscle and connective tissue elasticity evaluation, spleen, kidney, skin, lymphatic tissue, etc. The elastography method, age, body mass index and technical points should be considered when performing ultrasound elastography. This review highlights its vast potential as a diagnostic tool in the pediatric population, where ultrasound is a dominant imaging tool; however, the indications and exam protocol for its clinical use in several fields in pediatrics have yet to be elucidated.

Shear Wave Elastography in Bruxism-Not Yet Ready for Clinical Routine

Ultrasound shear wave elastography (SWE) is an emerging modality for the estimation of stiffness, but it has not been studied in relation to common disorders with altered stiffness, such as bruxism, which affects almost one-third of adults. Because this condition could lead to an increased stiffness of masticatory muscles, we investigated SWE in bruxism according to a proof-of-principle and feasibility study with 10 patients with known bruxism and an age- and gender-matched control group. SWE of the left and right masseter muscles was estimated under three conditions: relaxed jaw, 50% of the subjective maximal bite force, and maximal jaw opening. Rejecting the null hypothesis, SWE was significantly increased during relaxed jaw (bruxism 1.92 m/s ± 0.44; controls 1.66 m/s ± 0.24), whereas for maximal mouth opening, the result was vice versa increased with 2.89 m/s ± 0.93 for bruxism patients compared with 3.53 m/s ± 0.95 in the healthy control, which could be due to limited jaw movement in chronic bruxism patients (bruxism 4.46 m/s ± 1.17; controls 5.23 m/s ± 0.43). We show that SWE in bruxism is feasible and could be of potential use for diagnostics and monitoring, though we also highlight important limitations and necessary methodological considerations for future studies.

Prevalence of temporomandibular disorders in people with multiple sclerosis: A systematic review and meta-analysis

OBJECTIVE

To explore the prevalence of temporomandibular disorders (TMD) in patients affected by multiple sclerosis (MS) and whether there is a correlation between TMD prevalence and MS severity.

METHODS

PubMed, Web of Science, and Lilacs were systematically searched until July 30 2022, to identify studies presenting patients affected by MS and whether there is a correlation between TMD prevalence and MS severity.

RESULTS

Out of 292 papers, 8 studies were included with 1312 study participants. Among the 8 studies, 5 had a control group; 5 used the RDC/TMD criteria, 1 used the NOT-S instrument, and 2 did not define a standardized method to define TMD symptoms. Meta-analysis revealed that the MS group had a higher rate than the control group, showing an association between MS and TMD (RR 2.10; 95% CI: 1.21-3.65).

CONCLUSION

These findings show an association between TMD and MS.

ABBREVIATIONS

Australian Longitudinal Study of MS (AMSLS); Computed Tomography (CT); Community Periodontal Index of Treatment Needs (CPITN); Central Nervous System (CNS); Decayed, Missing, and Filled (DMF); Decayed, Missing, or Filled Teeth Index (DMFT); Expanded Disability Status Scale (EDSS); European Academy of Craniomandibular Disorders (EACD); Healthy Controls (HC); International Prospective Register of Systematic Reviews (PROSPERO); Multiple Sclerosis (MS); Nordic Orofacial Test-Screening (NOT-S); Participants, model of Intervention, Comparison and Outcome (PICO); Preferred Reporting Items for Systematic Reviews (PRISMA); Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD); Temporomandibular Joint (TMJ); Temporomandibular Disorders (TMD); World Health Organization (WHO).

Stiffness of the Masseter Muscle in Children-Establishing the Reference Values in the Pediatric Population Using Shear-Wave Elastography

In children, the quality and muscle function are altered in many pathologic conditions, including temporomandibular disorders. Although several methods have been used to evaluate muscle tonus, none became a golden standard. Moreover, the masseter muscle characteristics in children have not been investigated to date. This study aimed to measure the stiffness of the masseter muscle using shear-wave elastography in healthy children. We enrolled 30 healthy children (mean age 10.87 ± 3.38 years). The stiffness of masseter muscles was measured with shear wave elastography. Stiffness for the total sample was 6.37 ± 0.77 kPa. A comparison of the measurements did not show significant differences between the right and the left masseter muscles (left—6.47 ± 0.78 kPa; right—6.24 ± 0.76 kPa; p = 0.3546). A significant difference was seen between boys and girls (boys—5.94 ± 0.50 kPa; girls—6.63 ± 0.80; p = 0.0006). Shear-wave elastography is a promising diagnostic tool. It may help to detect changes in the stiffness of the masseter muscle and draw attention to pathological processes within the jaw muscles. Directions for further research shall include determining stiffness values in pathological conditions and the impact of biological and functional factors on the stiffness of the masseter muscle.