J Korean Assoc Oral Maxillofac Surg.  2019 Aug;45(4):174-179. 10.5125/jkaoms.2019.45.4.174.

Masticatory muscle tendon-aponeurosis hyperplasia accompanied by limited mouth opening

• Yoda T

• KMID: 2456034
• DOI: http://doi.org/10.5125/jkaoms.2019.45.4.174

Abstract

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.

Keyword

Masticatory muscle; Tendon; Aponeurosis; Limited mouth opening

MeSH Terms

Adolescent
Diagnosis
Drug Therapy
Humans
Hyperplasia*
Mandible
Masseter Muscle
Masticatory Muscles*
Mouth*
Occlusal Splints
Palpation
Tendons

Figure

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  Fig. 1 Photograph of a typical square mandibular shape.

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  Fig. 2 Three-dimensional computed tomography of MMTAH showing a small gonial angle and flattening of the mandibular plane. Both coronoid processes are thickened anteroposteriorly, but there is no contact between the coronoid process and the zygomatic arch on mouth opening. Adapted from the book of Yoda (Ishiyaku Publishers; 2012)13 with original copyright holder's permission.

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  Fig. 3 Horizontal section on magnetic resonance imaging (repetition time/echo time [TR/TE], 620.00/13.00) showing overhang of masseter muscle along the anterior border of the mandibular ramus and the aponeurosis as a black area on the outside and inside.

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  Fig. 4 A hard cord-like structure found along the anterior border of the masseter muscle on intraoral palpation.

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  Fig. 5 Optical microscopy findings (H&E staining) of the tendon tissue in masticatory muscle tendon-aponeurosis hyperplasia. The tendon fibers are normal.

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  Fig. 6 Electron microscopy shows mineralized nodules in the tendon tissues of a patient with masticatory muscle tendon-aponeurosis hyperplasia.

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  Fig. 7 A hyperplastic aponeurosis (a silvery-white color tissue) outside the masseter muscle.

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  Fig. 8 A hyperplastic tendon (a silvery-white color tissue) attached to the coronoid process.

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