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FIG 1. Coronal CT of a control subject. Measurement of the vidian-rotundum distance with electronic calipers shows a nonpneumatized greater sphenoid wing on the right (caliper 1), and a pneumatized greater sphenoid wing on the left (caliper 2). The vidian-rotundum distance was measured from the nearest bony margin of each canal, whether the foramen rotundum was visible on the coronal image as a semicircle, as noted in this subject, or as a complete ring.
FIG 2. Coronal CT of a control subject. The sinus wall adjacent to the groove for the internal carotid artery (arrows) was the most common site of thinning noted in the controls.
FIG 3. Coronal CT of a control subject with bilateral pneumatized greater sphenoid wings. The shape of vidian's canal varied from ovoid or circular in subject with nonpneumatized or slightly pneumatized greater wings (straight arrow), to an appearance of an "eye on a stalk" when the wing and pterygoid process were extensively pneumatized (curved arrow).
FIG 4. Mucocele in a 46-year-old man (patient 1). Coronal CT reveals unequivocal expansion of the right sphenoid sinus. The wall of vidian's canal is eroded (arrow), as is the sinus roof, right lateral wall, and floor. The left rotundum margins are intact, and the left sphenoid sinus is clear. The vidian-rotundum distance was 7 mm on the affected side, and was best measured on an adjacent section (not shown).
FIG 5. Mucocele in a 22-year-old woman (patient 3). Coronal CT reveals less pronounced but still unequivocal expansion of the sphenoid sinus, including enlargement of the anterior clinoid process. The margin of vidian's canal is eroded, with only a shallow groove remaining (straight arrow), while the foramen rotundum is flattened but not eroded (curved arrow). The floor of the sinus medial to vidian's canal was also eroded on an adjacent section (not shown). The vidian-rotundum distance on the affected side measured 16 mm, representing one of two patients with measurements greater than 11.4 mm.
FIG 6. Mucocele in a 51-year-old woman reveal by coronal CT (patient 7). When unequivocal expansion is not present, as in this patient, erosion of the margin of vidian's canal (arrow) and sinus floor medial to canal (on adjacent section, not shown) suggest mucocele rather than simple chronic sinusitis. The left foramen rotundum appears slightly thinned on this section, but did not demonstrate definite erosion on any adjacent image.
FIG 7. Mucocele of lateral recess in a 46-year-old woman revealed by coronal CT (patient 2). Erosion of the lateral aspect of vidian's canal (straight arrow) and inferior foramen rotundum (arrowhead) represents the only features differentiating this mucocele of the lateral recess of the sinus from a polyp or retention cyst. Compare eroded canal with normal contralateral canal (curved arrow). This very early surgically proven mucocele had not yet resulted in unequivocal expansion or other areas of sinus wall erosion.
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