Introduction

Paranasal sinus mucoceles are benign indolent cystic lesions filled with mucus and recovered by respiratory epithelium occurring due to an obstruction of sinus ostia.^{1 2} They are locally expansive and destructive, causing resorption, erosion, and bone remodeling.²

Mucoceles are often unilateral and may involve more than one sinus. Most commonly affected are the frontal (60 to 65%) and ethmoidal (20 to 30%) sinuses, followed by the maxillary (10%) and sphenoidal (2 to 3%) sinuses.³

Case Report

The patient was a 46-year-old woman with diagnosis of severe myopia since childhood, with routine periodic monitoring. There were no other comorbidities. In 2007, a sudden nasal hemianopsia appeared in the left eye. After further ophthalmologic investigation, she was referred for neurologic imaging study. A computed tomography (CT) scan showed soft tissue occupying some of posterior left ethmoid cells, adjacent to the lamina papyracea. In this topography, it presented tenuous irregularities that could correspond to erosion of its walls (Figs. 1 and 2). Magnetic resonance imaging (MRI) showed hyperintense image in T2 sequence, with no significant enhancement by contrast (Figs. 3 and 4).

Fig. 1 Coronal bone computed tomography image shows soft tissue content occupying some posterior left ethmoid cells, adjacent to the lamina papyracea. 

Fig. 2 Axial bone computed tomography reveals irregularities possibly corresponding to erosion of lamina papyracea. 

Fig. 3 Axial magnetic resonance imaging sequences show hyperintense signal in the corresponding tissue. 

Fig. 4 Axial magnetic resonance imaging sequences show hyperintense signal in the corresponding tissue. 

Possible ethmoidal mucocele with orbital involvement and optic nerve injury was considered during ear, nose, and throat evaluation. Surgical treatment was proposed then. For personal reasons, the patient opted not to be operated at the time, and she returned 2 years later with the same ophthalmic presentment. Another CT scan identified just slight thickening of the mucous lining and hypodense content in some posterior ethmoid cells, bilaterally, mostly in left side, with no difference in papyraceous plate (Fig. 5).

Fig. 5 Axial bone computed tomography reveals thickness of mucous lining and small content in posterior ethmoid cells, bilaterally, mostly in the left side. 

With no specific treatment performed, tomographic study in 2012 showed no lesions, but ophthalmic involvement remained unchanged (Figs. 6 to 7 8). Current eye examination found vision in the right eye of 20/100 and in the left eye, finger counting (temporal).

Fig. 6 Coronal bone computed tomography with normal findings. 

Fig. 7 Axial bone computed tomography with normal findings. 

Fig. 8 Another axial bone computed tomography with no abnormalities. 

Discussion

Paranasal sinus mucoceles are more common during the third and fourth decades, with slight predominance of male sex.² It is mainly related to previous sinus surgery, face trauma, and chronic rhinosinusitis.⁴ Nasal tumors, fibrous dysplasia, and cystic fibrosis are rarely associated causes, and the last one should be remembered in cases in children.^{5 6}

Paranasal sinus mucoceles are oligosymptomatic, slow-growing, expansive lesions. However, they may be locally aggressive and evolve to neurologic, skin, or eye complications. Substances such as prostaglandin E2 and collagenase are detectable in the capsule of the mucocele and seem to be related to its ability to resorb bone.^{3 7}

Imaging study allows easy identification of the injury and its extent. CT scan is the ideal method for detecting bone erosion and remodeling. MRI should be performed when intracranial invasion is suspected.⁸

Usually, ocular complications arise from absorption of papyraceous lamina, with possibility of proptosis due to displacement of the eyeball by the mucocele. Depending on the extent of bone erosion, the optic nerve can be compressed or stretched, resulting in transient or permanent visual impairment.

Surgical treatment must always be performed and, when done in a timely manner, may avoid optic nerve injury or even allow it to recover in cases of mild involvement.

Nasal endoscopic surgery has developed in the latest decades, and the endonasal approach is widely used. It has fewer postsurgical complications and minimal mucosal damage and offers a better postoperative view for close observation.^{7 8}