case_images: PMC7686843_01
case_images: Noncontrast computed tomography imaging of the paranasal cavity at the initial diagnosis. (a) Axial and (b) coronal views. We confirmed the presence of soft tissue contrast, suggesting a retention cyst at the rear sphenoid sinus, with thinning at the sella turcica and left internal carotid artery and elimination of the clivus (white arrows).
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case_images: PMC7686843_01_CRIOT2020-8897868.001.jpg
case_images: fig1
case_images: The presence of an expansive lump, likely originating from the rear sphenoid sinus, was confirmed on noncontrasted computed tomography (CT) (Figure 1).
case_images: Noncontrast magnetic resonance T2-weighted imaging of the paranasal cavity at the initial diagnosis. (a) Axial, (b, c) coronal, and (d) sagittal views. The basilar artery located adjacent to the cyst (c) is indicated with the red arrow, and the cyst located adjacent to the brainstem (d) is indicated with the white arrow; however, the signal intensity of the lesion's contents is determined to be different from that of cerebrospinal fluid, therefore suggesting a primary cyst.
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case_images: PMC7686843_01_CRIOT2020-8897868.002.jpg
case_images: fig2
case_images: Additionally, the presence of a space-occupying lesion at the same location with compression and an expansive growth pattern was confirmed by MRI (Figure 2).
case_images: Noncontrast computed tomography imaging of the paranasal cavity and Hess screen test results at the emergency reexamination. CT images with (a) axial and (b) coronal views. The sphenoid sinus mucocele shows apparent growth, with increased impingement on the left superior orbital fissure (white arrow). (c) The Hess screen test confirms a disturbance in the left eye abduction and overaction in the right eye adduction.
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case_images: fig3
case_images: Fifteen months after the initial diagnosis, the patient experienced acute diplopia upon waking one morning and immediately visited our department for an emergency reexamination (Figure 3).
case_images: Surgical findings. (a) Remedial surgery is performed on the nasal septum with exfoliation of the vomer bone. (b) Approximately one-third of the lower middle nasal concha is removed on both sides. (c) The rear end of the membranous septa is removed on both sides. (d) The vomer bone is removed by drilling, and (e) the frontal cystic wall is resected with the pituitary scalpel. (f) Bones of the cranial base showed thinning, with pulsations and dura mater observed through them (black arrow). r IC, right internal carotid artery and l IC, left internal carotid artery. (g), (h) Cranial base reinforcement using fat and fascia collected from the femur, and (i) hemostatic packing.
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case_images: fig4
case_images: For treatment, we performed a decompression of the mucocele using an endoscopic nasal approach (Figure 4).
case_images: Hematoxylin and eosin staining. (a) Magnifying glass image and (b) 200x magnification. The cyst displays fibrous walls with squamous metaplasia of the ciliated pseudostratified epithelium due to chronic inflammation (red arrow).
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case_images: fig5
case_images: Histopathology of the cystic wall showed a mucocele with fibrous walls, with squamous metaplasia of the ciliated pseudostratified epithelium in some portions due to chronic inflammation (Figure 5).
case_images: Postoperative evaluations. (a), (b) Postoperative computed tomography (plain) imaging of the paranasal cavity with a diminished sphenoid sinus mucocele, and (c) Hess screen test showing improvement in the abduction disturbance.
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case_images: fig6
case_images: No recurrence had occurred as of 30 months after the surgery (Figure 6).