Comparison of magnetic resonance imaging and gross findings regarding masseter muscle aponeuroses in cadavers

Ultrasound-guided five-point injection of botulinum toxin for patients with trapezius hypertrophy

OBJECTIVES

Our study aimed to explore the clinical therapeutic effects of ultrasound-guided five-point injection of botulinum toxin type A for patients with trapezius hypertrophy.

METHODS

Twenty female patients diagnosed with trapezius hypertrophy were enrolled in this study. The thicknesses of the trapezius muscle were measured by using the ultrasound scanner to locate the thickest point of trapezius, followed by labelling the other four points around the first point. Botulinum toxin type A was injected bilaterally (50 IU/side, 5 points/side) in the trapezius muscle of these patients. The surgery effects were evaluated by thicknesses of the trapezius muscle, intramuscular needle electromyographic and electroneurographic examinations, appearance changes and patients' satisfactions.

RESULTS

Statistically significant differences in thicknesses of the trapezius muscle were observed at 4 weeks (p < 0.001), 12 weeks (p < 0.001), 20 weeks (p < 0.001), 28 weeks (p = 0.011), 36 weeks (p = 0.022), and 44 weeks (p = 0.032) after surgery. The latencies of trapezius muscle became longer at 12 weeks after surgery (left: 2.40 ms, right: 2.53 ms vs. left: 1.75 ms, right: 2.00 ms). Electroneurographic results showed amplitude reduction of compound muscle action potentials (CMAPs) at 12 weeks after surgery (left: 1.91 uV, right: 3.10 uV vs. left: 15.00 uV, right: 15.40 uV). Obvious appearance changes were revealed at 12 weeks after surgery. All of 80% patients were very satisfied, 15% patients were relatively satisfied, and 5% patients were not satisfied with the surgery.

CONCLUSION

Ultrasound-guided five-point injection of botulinum toxin type A might be effective for patients with trapezius hypertrophy.

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.

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

Limited mouth opening is a common health problem that interferes with eating, makes examination of the oral cavity difficult, and may increase the mortality rate during emergency intubation. Here we introduce a disease designated as masticatory muscle tendon-aponeurosis hyperplasia, which is a new clinical condition of limited mouth opening. Most oral surgeons and dentists are still unaware of this disease condition, thus increasing the risk of incorrect diagnosis as some other disease, such as temporomandibular joint disorder. We will review the clinical features, epidemiology, pathophysiology, etiology, diagnosis, treatment, and prognosis of this disease and also appraise the literature available on the subject.

Surgical Intervention for Masticatory Muscle Tendon-Aponeurosis Hyperplasia Based on the Diagnosis Using the Four-Dimensional Muscle Model

OBJECTIVES

The surgical target of Masticatory muscle tendon-aponeurosis hyperplasia (MMTAH) is the masseter or temporal muscle. In our clinic, the 4-dimentional muscle model (4DMM) has been used to decide if we should approach to the masseter or temporal muscle. The aim of this study is validate the clinical usefulness of 4DMM on the basis of the surgical results.

METHODS

The 4DMM was constructed from the digital data of 3D-CT and 4-dimentional mandibular movements of the patients. It made us to able to visually observe the expansion rate of masticatory muscles at maximum mouth opening comparing to their length at closed mouth position. Fifteen patients were applied the 4DMM before the surgical treatment and 2 healthy volunteers were enrolled as control group.

RESULTS

The expansion rate of temporal muscle at the maximum mouth opening in the patient group was significantly less than that in the control group (P < 0.05). On the other hand, the masseter muscles of all patients were expanded as same as the control group. Therefore the main cause of limitation of mouth-opening was suggested to be a contracture of the temporal muscle. Consequently, we performed successful bilateral coronoidectomy with no surgical intervention to the masseter muscles in all patients.

CONCLUSION

The present 4DMM would be valuable modality to decide the target muscle of surgical treatment for patients with MMTAH. In this pathology, contracture of the temporal muscle seems to be main cause of limited mouth opening.

Long-term results of surgical therapy for masticatory muscle tendon-aponeurosis hyperplasia accompanied by limited mouth opening

Masticatory muscle tendon-aponeurosis hyperplasia is a new disease entity characterized by limited mouth opening due to contracture of the masticatory muscles, resulting from hyperplasia of tendons and aponeuroses. In the case of masseter muscle type, the face displays a square mandible configuration. Pharmacotherapy, occlusal splints and physical therapy are ineffective. This study evaluated the long-term results of aponeurectomy of the masseter muscle with coronoidectomy to release the temporal muscle tendon. The subjects were 10 patients who underwent surgery between 2000 and 2005. Mean maximum mouth opening before surgery was 21.8mm (range 17-29 mm). All patients received bilateral aponeurectomy of the masseter muscle and coronoidectomy. Three patients additionally underwent bilateral anglectomy for esthetic reasons. After discharge, one patient did not return to the hospital. Data from the other nine patients were analyzed. The mean duration of follow-up was 4 years. At final follow-up, the maximum mouth opening was >44 mm in four patients, 40-44 mm in three patients, and 35-39 mm in two patients. Overall satisfaction was excellent or good in all patients.

Regional differences of metabolism in human masseter muscle by two-dimensional 31P-chemical shift imaging

Many reports have demonstrated significant region-dependent differences in the fiber-type composition of the human masseter muscle. Therefore, it is considered that there is intramuscular heterogeneity of metabolic activity in the muscle. The present study was carried out, with two-dimensional Chemical Shift Imaging, to detect differences between the deep and superficial parts of the human masseter muscle at rest. Masseter muscle from 11 volunteers, from 20 to 27 years old, was examined, and characteristic spectra of the inorganic phosphate (Pi), phosphocreatine (PCr), and alpha-, beta-, and gamma-adenosine triphosphate (ATP) from each part of the muscles were obtained. In this study, the deep and superficial parts of the masseter muscle were distinguished by the existence of aponeurosis. The Pi/PCr, PCr/beta-ATP, and Pi/beta-ATP ratios as well as the pH in the deep and superficial parts were calculated from the peak spectra. Compared with the deep part, the Pi/PCr of the superficial part was lower (p < 0.05) and the PCr/beta-ATP was higher (p < 0.01). The Pi/beta-ATP and pH showed no significant differences between the two parts. The results indicate that the superficial part of the masseter muscle contains more PCr than the deep part, and this may be related to functional differences between these two parts. In future examinations of the metabolic activity of the human masseter muscle, the deep and superficial parts must be measured separately.