Masticatory muscle tendon-aponeurosis hyperplasia: A new clinical entity of limited mouth opening

Application of Ultrasonic Bone Scalpel in Surgery for Masticatory Muscle Tendon-Aponeurosis Hyperplasia

Masticatory muscle tendon-aponeurosis hyperplasia (MMTAH) is a disease that presents as a hard trismus due to hyperplasia of the masseter and temporalis aponeurosis. Standard surgical methods for MMTAH include masseter resection, temporalis aponeurosis, and coronoidectomy. The operation of resecting the tendon aponeurosis attached to the posterior surface of the coronoid process carries the risk of bleeding and nerve damage because it cannot be observed directly. Therefore, the authors introduce a safer method by using an ultrasonic bone scalpel for this procedure. The authors used an ultrasonic bone scalpel with a long neck blade to scrape the posterior side of the coronoid process from the bottom to the top. The authors have treated 4 cases using this technique, and in all cases, the surgical procedure was performed safely and easily. In conclusion, ultrasonic bone scalpels are effective in MMTAH surgery for removing the attachment of the stiffened temporalis muscle tendon and aponeurosis.

Congenital mandibular coronoid process hyperplasia and associated diseases

Coronoid process hyperplasia (CPH) is an oral and maxillofacial surgical disease that can result in restricted jaw movement due to an enlarged and elongated mandibular coronoid process. It is characterized by the painless progressive restriction of unilaterally or bilaterally mouth opening. Clinically, unexplained bilateral CPH is less common and therefore often overlooked or misdiagnosed, and coronoidectomy can be very effective on improving mouth opening. Currently, the exact etiology and mechanism of congenital CPH have not yet been fully understood, but it is generally believed to be genetically related. In this paper, the relationship of the congenital mandibular CPH with the related diseases was examined based on cases collected in our clinic and literature review for the clinical diagnosis and treatment of patients with restricted mouth opening associated with CPH.

Masticatory muscle tendon-aponeurosis hyperplasia that was initially misdiagnosed for polymyositis: a case report and review of the literature

BACKGROUND

Masticatory muscle tendon-aponeurosis hyperplasia (MMTAH) is a relatively newly identified clinical condition that manifests as trismus with a square-shaped mandible. Herein, we report a case of MMATH that was initially misdiagnosed for polymyositis due to trismus and simultaneous lower limb pain, with literature review.

CASE PRESENTATION

A 30-year-old woman had a history of lower limb pain after exertion for 2 years. Initial physical examination had been performed at the Department of General Medicine in our hospital. There was also redness in the hands and fingers. Although polymyositis was suspected, it was denied. The patient visited our department for right maxillary wisdom tooth extraction. Clinical examination revealed that the patient had a square-shaped mandible. The maximal mouth opening was 22 mm. There was no temporomandibular joint pain at the time of opening. Furthermore, there was awareness of clenching while working. Panoramic radiography revealed developed square mandibular angles with flattened condyles. Computed tomography showed enlarged masseter muscles with high-density areas around the anterior and lateral fascia. Magnetic resonance imaging also showed thickened tendons and aponeuroses on the anterior surface and inside bilateral masseter muscles. Finally, the patient was diagnosed with MMTAH. Bilateral aponeurectomy of the masseter muscles with coronoidectomy and masseter muscle myotomy was performed under general anesthesia. The maximum opening during surgery was 48 mm. Mouth opening training was started on day 3 after surgery. Histopathological examination of the surgical specimen showed that the muscle fibers were enlarged to 60 μm. Immunohistochemistry testing for calcineurin, which was associated with muscle hypertrophy due to overload in some case reports, showed positive results. Twelve months after surgery, the mouth self-opening and forced opening were over 35 mm and 44 mm, respectively.

CONCLUSIONS

Herein, we report a case of MMATH. Lower limb pain due to prolonged standing at work and overload due to clenching were considered risk factors for symptoms onset of MMATH.

Gene expression profiling of the masticatory muscle tendons and Achilles tendons under tensile strain in the Japanese macaque Macaca fuscata

Both Achilles and masticatory muscle tendons are large load-bearing structures, and excessive mechanical loading leads to hypertrophic changes in these tendons. In the maxillofacial region, hyperplasia of the masticatory muscle tendons and aponeurosis affect muscle extensibility resulting in limited mouth opening. Although gene expression profiles of Achilles and patellar tendons under mechanical strain are well investigated in rodents, the gene expression profile of the masticatory muscle tendons remains unexplored. Herein, we examined the gene expression pattern of masticatory muscle tendons and compared it with that of Achilles tendons under tensile strain conditions in the Japanese macaque Macaca fuscata. Primary tenocytes isolated from the masticatory muscle tendons (temporal tendon and masseter aponeurosis) and Achilles tendons were mechanically loaded using the tensile force and gene expression was analyzed using the next-generation sequencing. In tendons exposed to tensile strain, we identified 1076 differentially expressed genes with a false discovery rate (FDR) < 10-10. To identify genes that are differentially expressed in temporal tendon and masseter aponeurosis, an FDR of < 10-10 was used, whereas the FDR for Achilles tendons was set at > 0.05. Results showed that 147 genes are differentially expressed between temporal tendons and masseter aponeurosis, out of which, 125 human orthologs were identified using the Ensemble database. Eight of these orthologs were related to tendons and among them the expression of the glycoprotein nmb and sphingosine kinase 1 was increased in temporal tendons and masseter aponeurosis following exposure to tensile strain. Moreover, the expression of tubulin beta 3 class III, which promotes cell cycle progression, and septin 9, which promotes cytoskeletal rearrangements, were decreased in stretched Achilles tendon cells and their expression was increased in stretched masseter aponeurosis and temporal tendon cells. In conclusion, cyclic strain differentially affects gene expression in Achilles tendons and tendons of the masticatory muscles.

Temporal Tendinitis in Craniomandibular Dysfunction (CMD) - Does it Really Exist? A Temporomandibular MRI Investigation

OBJECTIVES

 The aim of the study was to analyze the role of temporal muscle and particularly tendon pathology in patients suffering from craniomandibular dysfunction (CMD) using magnetic resonance imaging.

MATERIALS AND METHODS

 Retrospective analysis of MRI examinations was carried out with regard to temporal muscle fibrosis and fatty degeneration and particularly temporal tendon rupture, thickening, and degenerative signal alterations. Descriptive statistics and the Mann-Whitney U-test were used for statistical evaluation.

RESULTS

 Structural lesions of temporal muscle parenchyma were the absolute exception. PD hyperintensity, pronounced contrast enhancement, or peritendinous fluid collections along the temporal tendon were found only to a small extent, and a (partial) rupture occurred in only one case. The tendon diameter showed only slight variability. The Mann-Whitney U-test provided no results indicating a causal connection between degenerative joint or disc disease and temporal tendon pathology.

CONCLUSION

 A large sample of 128 magnetic resonance imaging examinations provided no evidence of a major role of temporal tendinitis in clinical CMD syndrome.

KEY POINTS

  · Retrospective analysis of temporal tendon in CMD patients.. · Abnormal structural findings along the tendon seen only rarely.. · Obviously no crucial role of temporal tendon lesions in CMD syndrome..

CITATION FORMAT

· Stimmer H, Grill F, Waschulzik B et al. Temporal Tendinitis in Craniomandibular Dysfunction (CMD) - Does it Really Exist? A Temporomandibular MRI Investigation. Fortschr Röntgenstr 2022; DOI: 10.1055/a-1829-6134.

Masticatory muscle tendon-aponeurosis hyperplasia accompanied by limited mouth opening

Patients with masticatory muscle tendon-aponeurosis hyperplasia (MMTAH) experience limited mouth opening due to restricted muscle extension. Hyperplastic aponeurosis and tendons lead to the restriction of muscle extension. The criteria for the diagnosis of MMTAH are limited mouth opening that progresses very slowly from adolescence, intraoral palpation reveals a hard cord-like structure along the overhang of the anterior border of the masseter muscle on maximum mouth opening, and a square mandible. Conservative treatment, including pharmacotherapy, occlusal splint and physical therapy are ineffective. The standard therapy is surgical treatment, such as anterior partial aponeurectomy of the masseter muscle and coronoidectomy. The long-term results are very satisfying.

Possible association of oestrogen and Cryba4 with masticatory muscle tendon-aponeurosis hyperplasia

OBJECTIVE

Masticatory muscle tendon-aponeurosis hyperplasia, which is associated with limited mouth opening, progresses very slowly from adolescence. The prevalence rates of this disease are higher among women than among men, suggesting oestrogen involvement. As parafunctional habits are frequently observed, mechanical stress is likely involved in the pathogenesis and advancement of this disease. To elucidate the pathological condition, we examined the effect of oestrogen on tenocyte function and the relationship between mechanical stress and crystallin beta A4 (Cryba4), using murine TT-D6 tenocytes.

MATERIALS AND METHODS

Cell proliferation assays, RT-PCR, real-time RT-PCR, Western blot analysis and mechanical loading experiments were performed.

RESULTS

The physiological dose of oestrogen increased the levels of scleraxis and tenomodulin in TT-D6 tenocytes. In contrast, forced expression of Cryba4 inhibited scleraxis expression in these cells. Surprisingly, oestrogen significantly promoted cell differentiation in the Cryba4-overexpressing TT-D6 tenocytes. Moreover, tensile force induced Cryba4 expression in these tendon cells.

CONCLUSION

Oestrogen and Cryba4 may be associated with the progression of masticatory muscle tendon-aponeurosis hyperplasia.