Cholesterol Granuloma of the Sphenoid Sinus: An Insidious Entity

Abstract

Pathology of sphenoid sinus is uncommon and may pose a diagnostic challenge in view of its vague symptoms together with its relatively inaccessible location at the skull base. Radiological imaging is of utmost importance in diagnosis. We present an insidious case of a sphenoid sinus cholesterol granuloma.

Introduction

Pathological lesions primarily involving the sphenoid sinus are uncommon and only accounts for less than 3% of sinus pathologies [1]. These lesions are often hard to detect as its initial symptoms are vague and non-specific with an insidious course. Isolated sphenoid sinus disease (ISSD) was first described in detail by Wyllie et al. [2] and covers a spectrum of pathologies ranging from infectious/inflammatory etiologies to benign or malignant neoplasms. We encountered a case of a cholesterol granuloma of the sphenoid sinus.

Case Report

A 62 year old female presented with a four month history of diplopia and right upper eyelid drooping. She did not have any headaches, photophobia or seizures suggestive of an intracranial pathology.

Examination of the eye revealed right cranial nerve III, IV and VI palsies. Visual acuity was normal. Examination of the ear, nose and throat was unremarkable. Nasal endoscopy did not reveal any mass or pus discharge.

Computed tomography (CT) scan of the paranasal sinuses detected a non-enhancing expansile mass in the right sphenoid sinus causing elevation of the sella turcica. There was bony erosion of the walls of the right sphenoid sinus, sella turcica, right petrous apex and right carotid canal (Fig. 1). Magnetic resonance imaging (MRI) scan of the brain showed an extracranial, infrasellar mass compressing the right cavernous sinus and exhibiting hyperintensity on T1W (Fig. 2) with mixed hyperintensity on T2W. The lesion did not show any enhancement post-contrast. The pituitary gland was present with normal appearance. Endocrine workup was normal.

Fig. 1.

Sagittal view CT image of expansile mass measuring 3.2 cm × 3.9 cm × 3.5 cm within the right sphenoid sinus

Fig. 2.

T1-weighted MRI showing a mass with high signal intensity within the right sphenoid sinus

Patient underwent endoscopic endonasal transsphenoidal excision which revealed a brownish encapsulated mass filling up the sphenoid sinus with a soft consistency and adhered to the dura. The diaphragma sellae was intact with no cerebrospinal fluid leak. The tumour and its capsule was dissected out using suction and curettage.

The histopathological analysis showed chronic inflammatory cells with CD68 positivity, cholesterol clefts, hemosiderin-laden macrophages, calcifications and multinucleated giant cells with aggregates of foamy histiocytes suggestive of a cholesterol granuloma. Postoperatively, patient had no residual ptosis and recovered full range of movement of the right extraocular muscles.

Discussion

It is believed cases of isolated sphenoid sinus disease (ISSD) have been underreported previously. However, with the introduction of endoscopic cameras and radiological imaging, sphenoid sinus lesions have been detected more frequently. It is estimated that less than 3% of inflammatory lesions of the paranasal sinuses seem to affect the sphenoid [1]. Based on a review of published papers on ISSD, inflammatory lesions account for 50.3%, mucoceles made up 20.2% and neoplasms account for 13.6% [3].

Sphenoid sinus lesions often present insidiously due to its relatively inaccessible location and potential space which allows tumours to grow. The symptoms can be correlated anatomically by the involvement of structures surrounding the sphenoid sinus. Vision impairment is commonly encountered and is due to the mass extending laterally and affecting the VI cranial nerve causing lateral rectus muscle palsy. Further enlargement of the lesion may lead to involvement of the II, III, IV and V cranial nerves causing double vision, decreased visual acuity and numbness over the face [4].

Radiological imaging is invaluable in diagnosing ISSD. CT imaging allows for crucial information regarding the extensions of the lesion, bony remodeling or erosion and relations to the optic nerve and carotid artery. Tumours of the sphenoid sinus are often associated with bony erosion on CT as evidenced in a case review conducted by Pearlman [1] where 83% of patients with tumours in the sphenoid sinus had bony erosion. In contrast, there was no evidence of bony erosion for cases of inflammatory lesions of the sphenoid [1]. In addition to CT, MRI scan gives further evaluation on the involvement of the dura, cavernous sinus, optic nerve and hypophysis. In our patient, the bony erosion noted on CT scan suggested a neoplastic etiology while MRI enhancement indicated proteinaceous content with calcifications. Based on our patient’s presentation with cranial nerve involvement and findings of an expansile mass with bony erosion, we had anticipated a mucocele or a neoplasm of the sphenoid sinus possibly craniopharyngioma. However, histopathological examination showed a characteristic features of cholesterol granuloma. Another differential that should be considered is a hemangioma of the paranasal sinus which is noted to cause expansile bony remodeling and erosion. These vascular lesions characteristically appear as a heterogenous mass on MRI with intermediate signal intensity on T1- and high signal intensity T2-weighted MRI images [5].

Cholesterol granulomas are uncommon in the paranasal sinus and have mostly been reported to be found in the temporal bone, liver, kidney, mandible, brain, testis and breast [6]. In a literature review by Durgam and Batra [6], cholesterol granuloma (CG) of the paranasal sinuses occurs primarily in the maxillary and frontal sinus. Typical MRI findings in this disease are hyperintensity on both T1- and T2-weighted imaging as a result of paramagnetic methemoglobin accumulation [6]. However, up to 12.5% of lesions showed low to moderate intensity on T2-weighted imaging similar to this case. In contrast, a mucocele typically has hyperintensity on T2-weighted imaging with hypointensity on T1-weighted imaging. It should be noted however, that signal characteristics of mucocele change over time due to the changes in the protein content and viscosity [6].

Treatment of cholesterol granuloma of the paranasal sinus is generally surgical excision either endoscopically or via open approach. In our case, the lesion was confined to the sphenoid sinus and was amenable to endoscopic transsphenoidal surgery. Complete excision could be achieved successfully and open surgery was avoided. Following excision, recurrence rates are low and have been reported to be 3.7% in a review by Durgam [6]. In fact, endoscopic techniques were more successful than open resection as recurrence only occurred in cases which underwent open approaches.

Conclusion

Cholesterol granuloma of the sphenoid sinus is an uncommon clinical entity which may mimic other pathologies of the sphenoid sinus. The diagnosis relies on radiological imaging and histopathological confirmation. Treatment of this condition is complete surgical excision either endoscopically or via open approaches depending on its location and accessibility.

Author contributions

All authors contributed to the study conception and design. Material preparation, data collection and drafting of the article were performed by RLCA. Critical revision of the article was done by EKK and SH. All authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Funding

None.

Declarations

Conflict of interest

The authors declare that they have no conflict of interest.

Consent to participate

Informed consent was obtained from the patient.

Consent for publication

Informed consent was obtained from the patient for submission of the case report for publication.