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|LETTER TO EDITOR
|Year : 2012 | Volume
| Issue : 3 | Page : 332-333
Cholesterol granuloma of the sphenoid sinus: An unusual sphenoid sinus lesion
Munawwar Ahmed1, Elizabeth Joseph1, Sunithi Mani1, Geeta Chacko2, Vedantam Rajshekhar3
1 Department of Radiodiagnosis, Christian Medical College, Vellore, Tamil Nadu, India
2 Department of Pathology and Neurological Sciences, Christian Medical College, Vellore, Tamil Nadu, India
3 Department of Neurological Sciences, Christian Medical College, Vellore, Tamil Nadu, India
|Date of Submission||04-Dec-2011|
|Date of Decision||04-Dec-2011|
|Date of Acceptance||28-Apr-2012|
|Date of Web Publication||14-Jul-2012|
Department of Radiodiagnosis, Christian Medical College, Vellore, Tamil Nadu
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Ahmed M, Joseph E, Mani S, Chacko G, Rajshekhar V. Cholesterol granuloma of the sphenoid sinus: An unusual sphenoid sinus lesion. Neurol India 2012;60:332-3
Sphenoid sinus is a very rare location for the occurrence of cholesterol granuloma (CG), and we present one such case.
A 48-year-old man presented with gradual loss of vision of the right eye since 1 year and headache since 4 years. On examination, visual acuity in the right eye was finger counting at a distance of two feet. Humphrey-automated perimetry showed right inferior temporal quadrantanopia. Fundoscopy revealed right optic atrophy. Blood biochemistry was normal. Magnetic resonance imaging (MRI) of the brain and orbit showed a hyperintense expanded sphenoid sinus on T1-weighted image (T1WI) [Figure 1]a. This was isointense to grey matter on the T2-weighted image (T2WI) and Fluid-Attenuated Inversion Recovery (FLAIR) sequence, with few hypointense areas [Figure 1]b and c. The right optic nerve was compressed by the expanded sinus [Figure 1]a. No diffusion restriction was noted on diffusion-weighted imaging (DWI) [Figure 1]d and e. He underwent an endoscopic transnasal evacuation of the sphenoid sinus with excision of the mucosa. Erosion of the planum sphenoidale with pulsating dura was clearly visible. The evacuated material was thick pus like and negative for fungal or mycobacterial growth. Histological examination revealed fibrocollageneous tissue with a polymorphic inflammatory infiltrate composed of lymphocytes, plasma cells, foamy macrophages and a few neutrophils. Also present was a CG of an aggregate of cholesterol crystals surrounded by a foreign body giant cell reaction [Figure 1]f and g. A diagnosis of CG of the sphenoid sinus was made.
|Figure 1: (a) Sagittal T1-weighted image shows hyperintese lesion in the expanded sphenoid sinus (large arrow) compressing the right optic nerve (small arrow). Axial T2-weighted image and FLAIR images (b and c) show lesion isointense to grey matter with low-intensity foci (arrow) due to breakdown blood products. There was no diffusion restriction on diffusion-weighted imaging (arrow) (d) and ADC map (arrow) (e). (f and g) Photomicrographs illustrating low- and high-power views of the cholesterol granuloma composed of an aggregate of cholesterol crystals surrounded by a foreign body giant cell reaction (H and E, ×100 and H and E, ×400)|
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CG is commonly seen in air cells of the temporal bone. The middle ear is the most common site for CG. Paranasal sinuses are uncommon sites, maxillary sinus being the most common site. CG of the sphenoid sinus has rarely been reported. ,, Symptoms of CG are usually related to the pressure effect on the adjacent structures. Rarely, CG of the sphenoid sinus can present with gradual loss of vision.  CG usually results from a foreign body reaction of the bone to an obstructed airless bony cavity.  Typical MRI features of CG include a hyperintense lesion on both T1WI and T2WI with a peripheral T2WI hypointense hemosiderin rim and/or hypointense foci due to breakdown products of blood.  Hyperintensity on T1WI is attributed to by-products of hemorrhage and cholesterol crystals. It is predominantly due to paramagnetic intracellular methemoglobin. There is usually no enhancement on post-gadolinium T1WI images, but, occasionally, peripheral enhancement may be seen. CG is usually hypointense on DWI but sometimes can be hyperintense on DWI. , Imaging differential diagnosis of T1 hyperintense sphenoid lesions include mucocele, craniopharyngioma, Rathke's cleft cyst, epidermoid and dermoid cyst. Dermoid can be differentiated by their fatty attenuation on CT scan. Mucocele, craniopharyngioma, Rathke's cleft cyst and epidermoid are usually hypointense on T1WI and hyperintense on T2WI. T1W hyperintensity of these lesions is due to the high protein content. Epidermoid would show restricted diffusion on DWI. A hypointense peripheral rim and/or hypointense foci on T2WI are characteristic imaging features of CG. However, these may be difficult to differentiate in the absence of typical MRI findings of CG. In the present case, CG was not considered in the list of imaging differentials because of its extreme rarity in the sphenoid sinus.
CG of the sphenoid sinus is of clinical significance due to its granulomatous nature, unlike mucocele and other expansile T1W hyperintense lesions. It can cause erosion and destruction of the bone of origin and invasion of the adjacent vital structures with resultant symptoms and complications as seen in its usual location in the temporal bone.  Endoscopic drainage is now the safe and effective treatment.
In conclusion CG should be included in the differential diagnosis of T1W hyperintense expansile lesion of the sphenoid sinus. It may be difficult to differentiate CG from other expansile T1W hyperintense lesions in the absence of characteristic MRI findings.
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