原文題目

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口腔病理科 On-Line KMU Student Bulletin

原文題目(出處)： Osteochondroma of the coronoid process (Jacob's disease):

an unusual cause of restricted jaw motion. Am J Otolaryngol 2011;32:52-4

原文作者姓名： Nicholas D'Ambrosio, Robert M. Kellman, Sasan Karimi 通訊作者學校： Crouse Hospital, Upstate Medical University, Memorial

Sloan Kettering Cancer Center 報告者姓名(組別)：葉彥宏(Intern J 組)

報告日期： 100.05.10

內文：

Abstract

1. Osteochondromas are the most common benign bone tumor, most commonly found in the ends of long bones;

2. They rarely involve facial bones, particularly the mandible.

3. Osteochondromas involving the coronoid process have rarely been reported in the literature but pose a diagnostic dilemma.

4. When large enough, osteochondromas of the mandibular coronoid process can form a joint with the zygomatic arch (Jacob's disease).

5. This pseudoarticulation results in restricted jaw motion, which can clinically be mistaken for temporomandibular joint dysfunction.

6. We report a case of a 39- year-old man with chronic restricted jaw motion undiagnosed for several years.

Introduction

1. Osteochondroma, or osteocartilaginous exostosis, is a cartilage-capped exophytic lesion that arises from the cortex of a bone.

2. It constitutes 20% to 50% of all benign tumors and 10% to 15% of all bone tumors.

3. It is relatively uncommon in the jaw.

4. The rare osteochondroma of the mandible occurs at the condyle or the tip of the coronoid process.

5. This cartilage capped growth accounts for 35.8% of benign bony tumors and for 8.5% of bony tumors overall.

6. Enlargement of the coronoid process of the mandible was first described by Langenbeck in 1853, and joint formation between the coronoid process and the zygoma was first described by Jacob in 1899.

7. The most consistent clinical feature of this condition is reduction in mouth opening.

8. A review of the literature reveals only 34 histologically proven cases of osteochondroma of the coronoid process of the mandible.

9. The disease appears to involve males (73.5%) more often than females, with a mean age of 35 years.

10. The treatment is surgical, with an intraoral approach being the most preferred among most reported cases. None of the reported cases showed a recurrence.

Case report

1. A 39-year-old white man complained of progressive limitation in mouth opening for approximately 3 years.

2. The patient was treated for temporomandibular joint (TMJ) dysfunction, without improvement. Physical examination revealed no palpable mandibular mass or facial asymmetry.

3. For several years, the patient had undergone several magnetic resonance imaging

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(MRI) of the TMJ, revealing degenerative changes of the articular disk bilaterally, without evidence of abnormal displacement.

4. After clinical complaints of maxillary sinus pressure and suspected sinus disease, computed tomography (CT) examination of the paranasal sinuses demonstrated a large mushroom-shaped exostosis arising from the left coronoid process.

5. During the

following month, the patient was referred to a head and neck surgeon.

Using an intraoral approach, we

endoscopically

excised the coronoid mass and

removed it from the masticator space.

6. Pathology revealed an osteochondroma, measuring 2.0 × 1.0 × 0.8 cm, with a cartilaginous cap measuring 0.3 cm

in maximal thickness. Shortly after surgery, the patient reported much improved jaw motion and opening.

Discussion

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1. Although osteochondroma is the most common tumor of skeletal bones, it is relatively uncommon in the jaw, occurring at the condyle or the tip of the coronoid process.

2. Initial signs and symptoms include tightness within the joint area and gradual reduction in mouth opening. The slow development of trismus and painless facial mass typify the later stages.

3. Jacob's disease involves the development of an osteochondroma of the coronoid process and leads to the formation of a pseudo joint between the zygoma and the coronoid process.

4. The zygoma remodels, forming a pseudo joint that results in decreased mouth opening. The growth enlarges to push out the cortices of the zygoma, Because of its insidious clinical onset, Jacob's disease is often overlooked and misdiagnosed as a TMJ disorder. Magnetic resonance examination of the TMJ is usually the imaging method chosen in patients with such symptoms.

5. However, the coronoid processes are not evaluated because they are not included in the field of view in MRI of TMJ. In addition to plain film radiographs, CT has become the standard in preoperative assessment and surgical planning.

6. Three-dimensional reformatted images also allow for the assessment of the length of the coronoid processes and changes on the inner aspect of the zygomatic arch.

7. Endocrine stimulation, increased TMJ activity, trauma, and genetic and familial predisposition are mentioned as etiologic factors for coronoid hyperplasia.

8. Although rare, peripheral chondrosarcoma can arise from a sessile osteochondroma, especially if the cartilaginous cap, accurately demonstrated on MRI, exceeds 2 cm .

9. Different surgical approaches have been advocated to treat this Jacob's disease.

Most of the previously reported cases of coronoid hyperplasia and Jacob's disease had been treated through an intraoral approach.

10. Until 1961, nearly all reported tumors were resected via a zygomaticofacial approach, with or without temporary severing of the zygomatic arch.

11. The intraoral approach, first described in 1958 by Antoni, is safer and generally allows complete removal of the tumor. None of the reported cases showed a recurrence after several years of follow-up.

Conclusion

1. An osteochondroma of the coronoid process can pose a diagnostic dilemma.

Jacob's disease is defined as a condition consisting of new joint formation between the hyperplastic coronoid process of the mandible and the inner aspect of the zygomatic arch.

2. Because of the history, as in this case, which includes an insidious clinical onset, this condition has often been overlooked and treated initially as a TMJ disorder.

CT has an important role in diagnosis and is useful for an adequate surgical planning.

題號題目

1 Which statement about coronoid hyperplasia is wrong?

(A) Male-to-female ratio : 5:1 (B) Bilateral > Unilateral (C) Restrict mouth opening

(D) Painful exophytic mass is common

答案(D ) 出處：Oral & Maxillofacial Pathology 2ed edition (P16)

題號題目

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2 Which statement about coronoid hyperplasia is wrong?

(A) Heredity plays a role in coronoid hyperplasia (B) MRI is more effective than CT

(C) Long-term results of surgery sometimes can be disappointing due to surgically induced fibrosis

(D) Mandible may deviate toward the affected side in unilateral coronoid hyperplasia

答案(B ) 出處：Oral & Maxillofacial Pathology 2nd edition (P16)