J Korean Assoc Oral Maxillofac Surg.  2014 Dec;40(6):301-307. 10.5125/jkaoms.2014.40.6.301.

Mouth opening limitation caused by coronoid hyperplasia: a report of four cases

• Kim SM
• Lee JH
• Kim HJ
• Huh JK

• KMID: 1799565
• DOI: http://doi.org/10.5125/jkaoms.2014.40.6.301

Abstract

Coronoid process hyperplasia is a rare condition that causes mouth opening limitation, otherwise known as trismus. The elongated coronoid processes impinge on the medial surfaces of the zygomatic arches when opening the mouth, which limits movement of the mandible and leads to trismus. Patients with trismus due to coronoid process hyperplasia do not have any definite symptoms such as temporomandibular joint pain or sounds upon clinical examination, and no significant abnormal signs are observed on panoramic radiographs or magnetic resonance images of the temporomandibular joint. Thus, the diagnosis of trismus is usually very difficult. However, computed tomography can help with the diagnosis, and the condition can be treated by surgery and postoperative physical therapy. This paper describes four cases of patients who visited our clinic for trismus and were subsequently diagnosed with coronoid process hyperplasia. Three were successfully treated with a coronoidectomy and postoperative physical therapy.

Keyword

Trismus; Temporomandibular joint disorders; Hyperplasia; Mandible; Diagnosis

MeSH Terms

Diagnosis
Humans
Hyperplasia*
Mandible
Mouth*
Temporomandibular Joint
Temporomandibular Joint Disorders
Trismus
Zygoma

Figure

• 

  Fig. 1 A. Panoramic radiograph showing hyperplasia of the bilateral coronoid processes. B, C. Sagittal computed tomography scans showing hyperplasia of the bilateral coronoid processes in case 1. The elongated bilateral coronoid processes impinged on the zygomatic arch (arrows).

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  Fig. 2 A. Magnetic resonance imaging of the right temporomandibular joint in a closed-mouth position. B. An open-mouth position in case 2.

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  Fig. 3 A. Preoperative panoramic radiograph showing hyperplasia of the right coronoid process. B, C. Preoperative computed tomography scans for case 2: three-dimensional view showing the elongated right coronoid process and heterotopic bone formation on the inside of the zygomatic bone (arrows).

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  Fig. 4 A. Panoramic radiograph showing hyperplasia of the bilateral coronoid processes. B, C. Sagittal computed tomography scans from case 3 showing hyperplasia of the bilateral coronoid processes. The elongated bilateral coronoid processes had impinged on the zygomatic arches (arrows).

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  Fig. 5 A. Transoral approach to the coronoid process. B. The right coronoid process from case 3. C. The left coronoid process from case 3.

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  Fig. 6 A. Preoperative maximum mouth opening distance for case 4. B. Postoperative maximum mouth opening distance for case 4.

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  Fig. 7 A. Panoramic radiograph showing hyperplasia of the right coronoid processes. B, C. Sagittal computed tomography scans from case 4 showing hyperplasia of the right coronoid processes. The elongated right coronoid process had impinged on the zygomatic arch (arrow).

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