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Neuroradiology Case of
the Week
Case 165
Keegan Markhardt, MD and Henry Z. Wang, MD, PhD
Clinical
Presentation: A 17-year-old male presents with long history of progressive limited ability to open the mouth.
Radiological Findings: Maxillofacial CT with the mouth in closed and open position was preformed. Closed mouth position shows hyperplasia of the coronoid processes bilaterally, extending above the level of the zygomatic arch into the superficial temporal fossa bilaterally. Open mouth position study demonstrates the coronary processes to collide with the zygomatic bone bilaterally causing limitation of mouth opening.
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| Figure 1: Selected CT axial slices with mouth closed (right) and open (left). |
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| Figure 2: Selected sagittal CT reconstruction slices with mouth closed (top) and open (bottom). |
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| Figure 3: 3D MIP reconstruction images with mouth closed (top) and open (bottom) |
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| Figure 4: 3D reconstruction views with mouth closed (top) and open (bottom) |
Diagnosis: Bilateral mandibular coronoid process hyperplasia
Discussion: Enlargement of the coronoid process was first described by Jacob in 1899 [1] and is considered an uncommon condition [2]. Coronoid process hyperplasia (CPH) presents clinically with long standing, progressive reduction of mandibular opening. In CPH, the cause of restricted mandibular movement is an impingement of an elongated coronoid process with the temporal surface of the zygomatic arch preventing further mouth opening. Clinically the differential diagnosis of CPH comprises all causes of ankylosis and pseudoankylosis of the temporomandibular joint [3]. Diagnosis may be made with the presence of three features: difficulty in mouth opening, subclinical progression and hyperplastic change of the coronoid process [4].
Izumi et al. (2005) compared the CT features of 13 cases of CPH with 61 controls and found that height compared to the zygomatic arch and axial configuration just inferior to most cephalic portion of the coronoid process were statistically different. They found that a middle (extending to the level of the zygomatic arch) or high (extending above the zygomatic arch) and an angular (triangular shaped) or round (rounded anteriorly) coronoid process may identify patients with clinically significant CPH. The majority of normal patients had low (below the level of the zygomatic arch) coronoid processes with stick-like (narrow and round) configuration.
CPH appears to be a disorder predominately of young adult males, with a 5 to 1 male to female ratio and an average age at first presentation is 25 years-of-age. CPH may be unilateral or bilateral. The bilateral form predominates, with a bilateral to unilateral incidence of 4.7 to 1 [2].
Multiple etiologies have been proposed, including: endocrine stimulus, increased temporalis muscle activity, genetic inheritance and familial occurrence [2]. There is some evidence to support the increased temporalis muscle hypothesis [4], but no consensus has been made as to an etiology. Additionally, conditions that widen the coronoid process, including trauma, chondroma and osteochondroma, may cause the same symptoms [4].
Current surgical options have yielded good results in improvement of mouth opening [4,5]. Treatment consists of intraoral coronoidotomy and physiotherapy to prevent scar tissue formation. Satisfactory and stable long-term results have been seen using this method [5].
References:
- Jacob O: Bulletins et memoires de la societe d’anatomic de Paris, 1899.
- 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 Mar;53(3):250-5. [Medline]
- Lyon LZ, Sarnat BG. Limited opening of the mouth caused by enlarged coronoid processes: Report of case. J Am Dent Assoc. 1963 Nov;67:644-50. [Medine]
- Izumi M, Isobe M, Toyama M, Ariji Y, Gotoh M, Naitoh M, Kurita K, Ariji E. Computed tomographic features of bilateral coronoid process hyperplasia with special emphasis on patients without interference between the process and the zygomatic bone. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005 Jan;99(1):93-100. [Medline]
- Gerbino G, Bianchi SD, Bernardi M, Berrone S. Hyperplasia of the mandibular coronoid process: long-term follow-up after coronoidotomy. J Craniomaxillofac Surg. 1997 Jun;25(3):169-73. [Medline]
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