Orbital cellulitis secondary to giant sino‐orbital osteoma: A case report

Abstract Background Although osteoma is a common benign tumor of the paranasal sinuses, its orbital extension is not common. Secondary orbital cellulitis has rarely been reported in association with sino‐orbital osteoma. Case A 30‐year‐old woman presented with left side proptosis, orbital pain and inflammation. Orbital CT scan showed a well‐defined giant osteoma in the superonasal part of the left orbit originating from the left ethmoidal sinus associated with opacity of the ipsilateral ethmoidal sinus and infiltration of orbital soft tissue. After treatment by systemic antibiotics, osteoma was resected with combined external and endoscopic surgery and the patient recovered uneventfully. Conclusion Sino‐orbital osteoma may manifest primarily as orbital cellulitis and needs early surgical intervention.


| INTRODUCTION
Osteoma, as the most common benign tumor of the paranasal sinuses, 1 is seen in 3% of the CT scan of sinuses. 2 Most of the sinus osteomas are asymptomatic and only 5% become symptomatic. 2 Giant osteomas are defined as those larger than 3 cm or heavier than 110 g. 3 These tumors may rarely extend from the sinus territory to intracranial or intraorbital spaces. 3 The latter, based on the site and extension of the orbital involvement, may produce proptosis, diplopia, visual complaints and epiphora. [1][2][3] Orbital emphysema and cellulitis have been rarely reported after extension of osteoma to the orbit. 2,[4][5][6] Herein we report a case of orbital cellulitis secondary to orbital extension of a giant ethmoidal osteoma, which was treated with a combination of endoscopic and external approach in addition to systemic antibiotics.

| CASE REPORT
A 30-year-old woman was referred to our clinic because of abrupt onset of proptosis, pain, blurred vision, eyelid edema and conjunctival injection of the left eye. She also complained from headache, general weakness and fever. She had a history of congenital strabismus in the left eye but no history of head trauma.
On general examinations, her temperature was 38.5 C. Her corrected visual acuity was 10/10 and 7/10 in the right and left eyes, respectively. She had a 5-mm non axial proptosis and a temporal and downward displacement of the left-sided globe. In addition to conjunctival injection and chemosis, the eyelids were edematous and

| DISCUSSION
In this article we reported a rare case of orbital cellulitis secondary to a giant sino-orbital osteoma and its successful management.
Osteoma is a slow-growing mesenchymal tumor which often involves periorbital sinuses in the craniofacial area. 1,2 It is more common in the male gender and in the fronto-ethmoidal sinuses. 1,2,7 Most of the sinus osteomas are asymptomatic and can be an accidental finding of craniofacial imaging. 2 Osteoma of paranasal sinuses rarely invade the adjacent anatomic spaces including cranium and orbit, and usually present clinically after intracranial or intraorbital extension. The reported incidence of orbital extension was 1%-5%. 2,3 Signs and symptoms of orbital extension of sinus osteoma can be divided into two categories. The first category is the result of pressure effect of the tumor including proptosis, orbital pain, diplopia, decrease in visual acuity, palpable mass and epiphora. The second category includes clinical findings secondary to sinusitis which may be the result of obstruction or damage to the involved sinus and presenting as orbital emphysema, orbital cellulitis and subperiosteal abscess formation adjacent to the involved sinus. [2][3][4][5][6]8 The orbital extension of the infection in some reports was suggested that occurred via the bony erosion of the tumor and involvement of the orbital periosteum. 5,9 On the other hand, an intact periosteum has been shown in cases of orbital invasion of infection, suggesting that the sinus contents may gain access to the orbit not only via the emissary vessels and nerves but also through the paper like thin medial wall of the orbit. [1][2][3] It was demonstrated that giant osteomas, as reported in our case, have more probability to induce sinusitis and signs of orbital invasion. 3 Trauma, infection and developmental anomalies are suggested as the etiologic background of osteoma. In rare cases it may be seen in a genetic background such as Gardner syndrome that was rolled out in our case. 1,2,6,[10][11][12] For symptomatic cases of sino-orbital osteoma specially giant osteomas, as reported in our patient, different surgical approaches are recommended from a pure external approach to a complete endoscopic technique. 1,2,[13][14][15][16][17] In the recent medical literatures, difficult cases are treated by endoscopic approaches and the indications for the external approach is limited to giant dense osteomas that cannot be excised by pure endoscopic techniques. [13][14][15][16][17] Although pure endoscopic approach, due to the less morbidities and time of hospitalization, is the preferred method for excision of the sinus osteomas, in cases with large and dense osteomas, to avoid damage to the orbital soft tissues and lengthening the operation time, the surgeon must be flexible to change the approach to the external one. [13][14][15][16][17] A combination of external and endoscopic approaches was implemented in our patient.
In cases with obstructed sinus openings and development of sinusitis, mucocele or cellulitis in the adjacent tissues, repair of the sinus drainage pathway and returning the sinus aeration, similar to what performed in our case, are mandatory. 2,5,6 Although partial removal of the sino-orbital osteomas was reported to be successful in many cases but tumor recurrence was reported in a few cases. 2,18 With the total removal of the tumor in our case, no recurrence was observed up to a 3-year follow up.
In conclusion orbital cellulitis is a rare complication of sino-orbital giant osteomas, which needs urgent intervention to not only treat the infection but also to remove the tumor and establish the sinus drainage.

ACKNOWLEDGEMENTS
Not applicable.

ETHICS STATEMENT
The study protocol was approved by the scientific and ethics committee of the Ophthalmic Research Center at Shahid Beheshti University of Medical Sciences and adhered to the principles outlined in the Declaration of Helsinki. Written informed consent was obtained from patient to use her medical data and face photographs.

CONFLICT OF INTEREST
The authors have no financial interest in the subject of this article.  writing-original draft.

DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.