Dentomaxillofacial Radiology (2006) 35, 55-59
© 2006 British Institute of Radiology
doi: 10.1259/dmfr/52275596
The value of three-dimensional computed tomography in diagnosis and management of Jacob's disease
H Akan* and
N Mehreliyeva
Ondokuz Mayis University, Faculty of Medicine, Department of Radiology, Samsun, Turkey
*Correspondence to: Hüseyin Akan, Ondokuz May
s University, Faculty of Medicine, Department of Radiology, 55139 Samsun, Turkey;; E-mail: akanhus{at}yahoo.com
Received 15 September 2004;
revised 21 April 2005;
accepted 2 May 2005
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Abstract
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This study reports a case of Jacob's disease characterized with limited mouth opening due to bilateral coronoid hyperplasia forming pseudojoints with zygomatic arches. Magnetic resonance (MR) examination of temporomandibular joint (TMJ) is usually the imaging method chosen in patients with such symptoms. However, the coronoid processes can not be displayed because they are not included in field of view in MR imaging of TMJ. For that reason, these patients may be treated for a misdiagnosis of TMJ disorders. In this study, the aetiology and diagnostic methods of Jacob's disease, the pre-operative/post-operative role of three-dimensional computed tomography and some measurements used in diagnosis were evaluated.
Keywords: coronoid hyperplasia; Jacob's disease; three-dimensional CT
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Introduction
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Coronoid hyperplasia is an abnormality characterized by malocclusion and restricted jaw movements caused by pressure of the coronoid process of the mandible, which is longer than normal size, on the posterior aspect of the zygomatic arch.1 In Jacob's disease, this hyperplastic segment makes a pseudoarticulation with the inner aspect of the zygomatic arch.2 Cases of coronoid hyperplasia are rarely reported in literature, and Jacob's disease even more rarely mentioned (16 case reports).3,4 Patients usually complain of restricted and painful mouth opening. Therefore, these patients may be treated for a misdiagnosis of temporomandibular joint (TMJ) disorders.3–5 Coronoid hyperplasia can occur unilaterally or bilaterally. Patients may have facial asymmetry, especially on mouth opening, in case of unilateral hyperplasia.4,5 Endocrine stimulation, increased TMJ activity, trauma, genetic and familial factors have been reported as the aetiology of the disease.
In this report, we present a case with Jacob's disease which was initially misdiagnosed as a TMJ disorder. We also investigated the value of three-dimensional computed tomography (3D CT) with some measurements in diagnosis as well as in pre-operative surgical planning.
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Case report
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A 24-year-old man was admitted to the department of maxillofacial surgery in faculty of dentistry with a 4 year history of progressive restriction of mouth opening. The patient is the first child of non-relative parents. The patient's brother does not have a similar complaint. There was no facial asymmetry on physical examination and the patient had no pain at the rest position.
He had been initially diagnosed by a clinician as having bilateral TMJ disorder and, subsequently, arthroscopic procedure had been performed. Magnetic resonance imaging (MRI) performed before arthroscopy was evaluated as being normal: volume and intensity of masticatory muscles were normal; joint surfaces were smooth; displacement or deformation of disks, and obliteration of the joint spaces and any area of low signal intensity suggesting fibrous change were not observed. No improvement was observed during the 9 month period after arthroscopy. Therefore, the patient was referred to the department of radiology for a new MR examination. MR images showed an obliteration of the medial compartment of the right joint space and a band-like area of low signal intensity on retrodiscal tissue (Figure 1a
). Disks were in normal position and configuration (Figure 1b). Since the MRI findings supported the clinical diagnosis of TMJ fibrous ankylosis, the patient underwent surgery by an oral surgeon.
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Figure 1 Sagittal gradient-recalled echo (GRE) MR image of the right temporomandibular joint (TMJ) 9 months after arthroscopy (a) showing an obliteration of the medial compartment of the joint space (arrow) and a band-like area of low signal intensity on retrodiscal tissue (arrowhead). (b) Disk (arrow) is in normal position and configuration. C: condyle
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As the complaint of the patient was not relieved after surgical intervention to the right TMJ, he was referred for post-operative MRI and later CT examination of TMJ. MR images revealed post-operative changes in the joint and surrounding tissues. On 3D CT images, bilateral coronoid processes were seen frankly above the zygomatic arch (Figure 2). Axial CT slices and sagittal reconstructed images showed a bilateral pseudoarticulation between the hyperplastic coronoid processes and exostoses which developed on the inner aspect of the zygomatic arches (Figure 3). It was noted that there was a concavity in the coronoid processes facing the exostosis-like hyperplasia on the posteromedial surfaces of the zygomatic bones. To be certain about the findings we performed some measurements on the 3D CT images. By drawing a line passing tangent to the mandibular incisura (deepest point of the curvature between the condyle and coronoid process) and parallel to the mandibular plane, the coronoid length over this line and the angle between mandibular plane and coronoid plane were measured (Figure 4a). The length of segment of coronoid process remaining upon the zygomatic arch was also measured in the case (Figure 4b). For comparison, the same measurements were also performed on the records of 30 patients with no complaints of TMJ disorder which were randomly selected from the departmental archive. Eighteen of them were male, the others were female. Their ages ranged from 21 years to 76 years, with a mean age of 38.8 years. There is not sufficient published data about average coronoid length, but in a normal population it must not extend above the zygomatic arch. We aimed to determine the amount of elongation and the degree of anterior movement of the hyperplastic coronoid process and sought whether there was significant difference between values obtained from our case and values in control subjects. While Asaumi et al6 made some measurements in two patients with coronoid hyperplasia, their landmarks were quite different and the results can not be directly compared.
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Figure 2 In three dimensional CT image, coronoid protrusion is seen above zygomatic arch. (a) Right side, (b) left side
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Figure 3 (a) Axial CT slice, and (b) 3D reformatted image show the extent of coronoid processes into temporal fossa and their pseudojoint with exostoses of zygomatic arches (arrows). Note the concavity of the articulating face of the coronoid (white arrow)
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Figure 4 Coronoidal measurements on 3D CT image. (a) Normal subject. (b) Patient with Jacob's disease. MP: mandibular plane, A: parallel line from incisura mandibulae to mandibular plane, BC: coronoid process length, ABC: coronoid process angle with mandibular plane, CZ: the part of the coronoid process above the zygomatic arch
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The angle between the mandibular plane and coronoid plane (80°) was not significantly different from the values that were obtained from the control group (average 84°±0.6; P=0.8) (Table 1). However, the length of coronoid process (3.2 cm) was found to be significantly higher than that of the control group (average 1.92±0.38 cm). In our case, the segment that passed the zygomatic arch measured about 1.3 cm.
The patient underwent an intraoral bilateral coronoidectomy. Pseudojoint was found between the hyperplastic coronoid processes and exostoses on the posteromedial aspect of the zygomas at the operation. The pseudojoint was surrounded by the fibrous pseudocapsule. Both sides of the bony parts of the pseudojoint showed histologically normally bone structure covered with cartilaginous layers. Mouth opening measured 1.5 cm before the operation and 3 cm after the operation. The patient was recommended post-operative physiotherapy and jaw exercises. On 3D CT performed post-operatively, it was observed that the excessive part of the coronoid process was completely removed on the right side and partially on the left side.
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Discussion
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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. Coronoid hyperplasia is a rare condition of unknown aetiology that might be unilateral or bilateral.7 Jacob's disease is rarer than isolated coronoid hyperplasia. In the literature, only 16 cases were found from 1899 to 2002.3,4 Different proportions of bony versus cartilaginous components have led to several histological diagnoses: osteochondroma, osteoma, cartilage capped exostosis and hyperplasia. In most of the patients with Jacob's disease, the involved coronoid segment was diagnosed histologically as osteochondroma, whereas hyperplasia was diagnosed in a few.3–5 McLoughlin et al reported that in both cases the bone was histologically normal, but its abnormal prolongation caused progressive restrictive jaw opening.8 The hyperplastic coronoid process is compressed posterior to the zygomatic arch, which causes the restriction of jaw movements. In the chronic condition, hypertrophy and fibrosis develop at masticatory muscles and symptoms become more evident. Facial asymmetry may be found if there is unilateral involvement. Coronoid hyperplasia incidence is more frequent in men at puberty.8,9 Endocrine stimulation, increased TMJ activity, trauma, genetic and familial predisposition are mentioned as aetiological factors.10
In some cases of coronoid hyperplasia, the same symptoms may be found in relatives or family members. In addition, coronoid hyperplasia can be a component of some syndromes like basal cell nevus syndrome and trismus-pseudocamptodactyly syndrome.9
In patients with restricted mouth opening, the differential diagnosis should include TMJ disorders, muscle diseases, coronoid hyperplasia and Jacob's disease. Most authors noted that when patients presented with restricted mouth opening, clinicians initially tended to diagnose TMJ disorder and to manage it as such.1,3–5 Although TMJs are not the common cause of restricted mouth opening, the relationship between enlarged coronoid processes and the TMJ disorders are significant. In a study of 163 patients with restricted jaw movement, Isberg et al found bilateral coronoid hyperplasia in 8 and TMJ disk displacement without reduction in 4 patients.11 Furthermore, delay in true diagnosis causes development of secondary TMJ ankylosis.7 Some significant pathoses of muscles of mastication that contribute to such limitation include enlargement, dense band of muscular tissues, fibrosis, surgical or pathological scarring, hyalinization and calcification.5 The MRI may show some TMJ abnormalities such as displacement or perforation of disk, fibrous changes, ankylosis, stuck disk, bony changes, and abnormalities of surrounding muscles and soft tissues. However, it is a limitation that coronoid process cannot be displayed because it is not included in field of view in MRI of TMJs.
To establish the diagnosis of Jacob's disease, we need to show a direct contact between hyperplastic coronoid process and posterior wall of maxilla or zygomatic arch and joint surfaces at this location. Panoramic radiography and Water's occipitomental view may be the first steps in radiographic examination. However, an observer usually does not pay attention to the coronoid processes because of focusing only on TMJs. Water's radiography displays coronoid hyperplasia, but it can not show the relationship between the hyperplastic segment and zygomatic arch.3
CT has an important role in diagnosis and is useful for an adequate surgical planning by allowing assessment of the size of impingement of the coronoid processes.12 On axial CT images, protrusion of hypertrophic segment to temporal fossa and articulation of this segment with the inner aspect of zygomatic arch can be clearly seen. 3D CT shows the elongated coronoid process passed above the zygomatic arch and joint formation. Joint formation can occur in two different models: (1) impingement of the coronoid process on the concavity formed at the zygomatic arch,5 (2) concavity on a coronoid process caused by the new bone formation on the medial surface of zygoma.2,6 The type of joint formation might determine a surgical approach. In our case, CT images showed exostosis-like hyperplasia on the inner aspect of the zygoma and its bulging into the infratemporal fossa, forming a joint with the concavity of the hyperplastic coronoid process.
Furthermore, 3D CT provides some additional measurement information for surgeons. Our measurements showed that there was no significant difference between the values of the patient and the values of healthy subjects apart from the coronoid process length. Measurement of the length and determining of the differences from normal range may be useful and important for planning the operation. It is notable that coronoid process plane has angled more posteriorly in the patient than in the normal subjects, although the difference was not significant. This might be due to the hyperplasia of the zygomatic part of the pseudojoint and its compression on the coronoid process.
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Conclusion
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In patients who complain of limited mouth opening and malocclusion, TMJ pathologies are first considered. Incorrect and careless examination may cause the delay of diagnosis and treatment. In patients referred with such complaints, consideration of coronoid hyperplasia or Jacob's disease facilitates the diagnosis. Axial and 3D CT in pre- and post-operative evaluation of these cases is very important. 3D reformatted images can clearly demonstrate hyperplastic coronoid process and joint surfaces. CT has an important role in diagnosis and is useful for an adequate surgical planning by allowing assessment of the length of the coronoid processes and changes on inner aspect of the zygomatic arch.
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References
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- Loh HS, Ling SY, Lian CB, Shanmuhasuntharam P. Bilateral coronoid hyperplasia – a report with a view on its management. J Oral Rehabilitation 1997; 24: 782–787.[CrossRef]
- Jacob O. Une cause rare de constriction permanente des machoires. Bull et Mem de la Société Anatomique de Paris 1899; 1: 917–919.
- Escuder i de la Torre O, Vert Klok E, Mari i Roig A, Mommaerts MY, Pericot i Ayats J. Jacob's disease: report of two cases and review of the literature. Craniomaxillofac Surg 2001; 29: 372–376.
- Emekli U, Aslan A, Onel D, Çizmeci O, Demiryont M. Osteochondroma of the coronoid process (Jacob's disease). J Oral Maxillofac Surg 2002; 60: 1354–1356.[Medline]
- Hernandez-Alfaro F, Escuder O, Marco V. Joint formation between an osteochondroma of the coronoid process and the zygomatic arch (Jacob disease): report of case and review of literature. J Oral Maxillofac Surg 2000; 58: 227–232.[Medline]
- Asaumi J, Kawai N, Honda Y, Shigehara H, Wakasa T, Kishi K. Comparison of three-dimensional computed tomography with rapid prototype models in the management of coronoid hyperplasia. Dentomaxillofac Radiol 2001; 30: 330–335.[Abstract]
- Colquhoun A, Cathro I, Kumara R, Ferguson MM, Doyle TC. Bilateral coronoid hyperplasia in two brothers. Dentomaxillofac Radiol 2002; 31: 142–146.[Abstract]
- McLoughlin PM, Hopper C, Bowley NB. Hyperplasia of the mandibular coronoid process: an analysis of 31 cases and a review of the literature. J Oral Maxillofac Surg 1995; 53: 250–255.[Medline]
- Leonardi R, Sorge G, Caltabiano M. Bilateral hyperplasia of the mandibular coronoid processes associated with the nevoid basal cell carcinoma syndrome in an Italian boy. Br Dent J 2001; 190: 349–350.[Medline]
- Totsuka Y, Fukuda H. Bilateral coronoid hyperplasia: report of two cases and review of the literature. J Craniomaxillofac Surg 1991; 19: 172–177.[Medline]
- Isberg A, Isacsson G, Nah KS. Mandibular coronoid process locking: a prospective study of frequency and association with internal derangement of the temporomandibular joint. Oral Surg Oral Med Oral Pathol 1987; 63: 275–279.[Medline]
- Pregarz M, Fugazzola C, Consolo U, Andreis IA, Beltramello A. Computed tomography and magnetic resonance imaging in the management of coronoid process hyperplasia: review of five cases. Dentomaxillofac Radiol 1998; 27: 215–220.[Abstract]
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Abstract
Introduction
