Dentomaxillofacial Radiology (2006) 35, 47-49
© 2006 British Institute of Radiology
doi: 10.1259/dmfr/55048928
Pneumatization of the sphenoid sinus
ER Terra*,1,
FR Guedes1,
FR Manzi2 and
FN Bóscolo1
1 Oral Radiology, Department of Oral Diagnosis, Piracicaba Dental School, State University of Campinas, Piracicaba, SP, Brazil;
2 Oral Radiology, Department of Oral Diagnosis, School of Dentistry, Pontificy Catholic University, Belo Horizonte, MG, Brazil
*Correspondence to: Etienne Romanelli Terra, Oral Radiology, Piracicaba Dental School, UNICAMP, Av. Limeira, 901. Areão, Zip Code: 13414-018, Piracicaba – SP – Brazil; E-mail: radiologia{at}fop.unicamp.br
Received 24 November 2004;
revised 16 March 2005;
accepted 2 May 2005
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Abstract
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This paper describes a case of pneumatization of the sphenoid sinus in the pterygoid process and greater wing of the sphenoid bone, observed on a panoramic radiograph. Conventional radiographs and computerized tomography in axial and coronal sections confirmed the presence of the pneumatization of these structures.
Keywords: pneumatization; sphenoid sinus; panoramic radiography
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Case report
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A 58-year-old white woman was referred to the radiological clinical service at Piracicaba Dental School-UNICAMP for a routine panoramic radiograph. The patient was asymptomatic and did not have history of previous trauma. On the panoramic radiograph (Figure 1
), a well-defined radiolucent image with a sclerotic margin in the region of the pterygoid process on the left side could be observed, similar to a cystic lesion. A lateral skull radiograph (Figure 2) showed the head in a different projection, but the image remained superimposed on the same region in the pterygoid process and, therefore, the diagnosis was not conclusive.
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Figure 1 Panoramic radiograph showing a well-defined radiolucent image with a sclerotic margin in the area of the pterygoid process on the left side (black arrow)
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To obtain a better diagnosis, the patient was submitted to a computerized tomography (CT) exam with axial scans obtained at 5.0 mm thickness and coronal scans at 3.0 mm thickness. The axial and coronal CT images (Figures 3–5) showed the presence of pneumatization on the left side of the sphenoid sinus extending 11.0 mm to the middle of the left greater wing of sphenoid bone and 5.0 mm to the superior portion of the pterygoid process.
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Figure 4 Axial CT scan showing the extension to the superior portion of the pterygoid process on the left side
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Discussion
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The sphenoid sinus is situated within the body of the sphenoid bone, and is widely recognized to be an irregular cavity, with the degree of pneumatization varying from absent to extensive.1 Usually, the pneumatization of the sphenoid sinus is discovered incidentally by means of skull radiographs, CT or even through panoramic radiography, as presented in this case, since in the great majority of the cases the patient does not relate any symptom and no treatment is necessary.2
According to Gray,3 the extension of the nasal cavity into the body of the sphenoid bone, to form the sphenoid sinus, is present before birth and does not reach its full extension until adolescence, continuing its development until after puberty.4 The pneumatization does occasionally extend into the vomer, palatine bone, ethmoid bone, occipital bone, anterior clinoid processes, lesser wings, greater wings, pterygoid process and its plates, and may cross the synchondrosis into the basilar part of the occipital bone.5–7 Excessive pneumatization of the sphenoid sinus renders its contents near the optic nerve, cavernous sinus, internal carotid artery, maxillary and the cranial nerves III, IV and VI, and some of these structures may bulge or also be involved by the sphenoid sinus.1,8
Because of its deep location and intimate structural relationship with intracranial structures,8 the pneumatization of sphenoid sinuses can make radiographic diagnosis difficult, particularly with conventional radiographic techniques or panoramic radiography. The pneumatization of the pterygoid process can appear radiographically in three ways: an image with aspect similar to the pterygomaxillary fissure; a radiolucent image superimposed on part of the zygomatic arch or, when the image is loculated, similar to a cystic lesion.2,9 In the present case, the pneumatization could cause a misdiagnosis because it mimicked a cystic lesion.
Generally, the extensions of the sphenoidal sinus are symptomless; however, Morton4 reported a case of excessive pneumatization that caused a swelling in the temporal region and a slight degree of axial proptosis of the left eye, which required surgery.
In conclusion, anatomical variations may frequently be encountered in routine radiographs, and they should be reported by the radiologist. It is particularly important to know and recognize these variations that can distort the image in skull and panoramic radiographs leading the radiologist to a possible mis-diagnosis.
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References
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Abstract
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