Abstract
The occurrence of postoperative secondary cholesterol cysts in the mastoid has been previously reported, however the occurrence of a primary large cholesterol cyst in the mastoid with bony destruction of the facial nerve has rarely been reported. The case report of a 17-year-old female patient with a primary large cholesterol cyst with dysgeusia is presented. Computed tomography and magnetic resonance imaging findings for the lesion distinguish a cholesterol granuloma, cholesteatoma and vascular tumor. The patient underwent a canal wall down mastoidectomy with mastoid obliteration. A dehiscent portion of the mastoid segment of the facial nerve was visible within the cavity; the gross finding of the facial nerve was edematous in appearance. Five years later, there has been no recurrence of disease.
A large cholesterol cyst is generally found to occur at the petrous apex in patients with a well-pneumatized middle ear and mastoid and without a history of chronic otitis media. The occurrence of postoperative secondary cholesterol cysts in the mastoid have been previously reported (1-3), however, the occurrence of a primary large cholesterol cyst in the mastoid with bony destruction of the facial canal associated with dysgeusia has rarely been reported. To date, only one report has been found in a search using the Medline database (4). Here, the case of a primary large cholesterol cyst in the mastoid presenting with a dysgeusia and mastoid otalgia is presented.
Case Report
A 17-year-old female presented with a three-month history of intermittent tinnitus, dysguesia and mild mastoid otalgia. The medical history was unremarkable. An otological examination revealed a dome-shaped dark blue mass displacing the lower half of the tympanic membrane laterally and extending into the hypotympanum. The patient had no facial weakness but dysgeusia and mastoid otalgia were noted. No changes in hearing were noted despite the obstruction of the external auditory canal. An audiogram demonstrated normal hearing thresholds. A high-resolution temporal bone computed tomography (CT) scan revealed a multilobulated non-enhanced 1.5×2.0 cm mass with evidence of significant erosive bony changes that extended to the external auditory canal and hypotympanum (Figure 1). A magnetic resonance imaging (MRI) scan of the temporal bone was obtained with and without gadolinium enhancement. A multilobulated 1.5×2.0 cm mass was identified deep in the right external auditory canal and mastoid, adjacent to the mastoid segment of the facial nerve. The mass demonstrated the same signal intensity on T1-weighted images and increased signal intensity on T2-weighted images (Figures 2A and B), with no enhancement of the mass seen on postgadolinium images. The patient underwent a canal wall down mastoidectomy. A giant blue-domed cyst was identified from a location below the fossa incuidus to the mastoid tip, adjacent to the mastoid segment of the facial nerve. The cyst contained clear, straw-colored fluid. A dehiscent portion of the mastoid segment of the facial nerve was visible within the cavity; the gross finding of the facial nerve was edematous and inflamed in appearance. The cyst wall was peeled off from the nerve using a small cotton ball that was soaked in 1:1,000 epinephrine solution. The cyst extended to the middle ear cavity with destruction of the lateral wall of the hypotympanum. The ossicle was intact. The cyst was completely removed (Figure 3). The mastoid obliteration was carried out with canal wall down tympanomastoidectomy. The pathological examination confirmed the presence of a cholesterol cyst (Figure 4). Five year later, there has been no recurrence of disease.
An axial temporal bone CT image showing a multilobulated non-enhanced 1.5×2.0 cm mass with evidence of significant erosive bony changes that extended to the external auditory canal and hypotympanum (arrows).
A, An axial T1-weighted pregadolinium MR image showing an isointense multilobulated mass in the right mastoid extending to the external ear and hypotympanum (arrows). B, An axial T2-weighted pregadolinium MR image showing hyperintense signal intensity of the same lesion (arrows).
The exposed mastoid segment of the facial nerve that was edematous and inflamed was noted after removal of the cholesterol cyst (arrows). The hypotympanum was packed with Surgicel.
The pathological examination demonstrated the cholesterol cyst. (Hematoxylin eosin stain, ×100).
Discussion
The etiology of a cholesterol cyst has been the subject of considerable debate (5). The development of large cysts may be slow and extend over a period of years or even decades. When CT imaging reveals a soft tissue density area in the mastoid cavity with destruction of the posterior wall of the external auditory canal, a cholesteatoma and facial nerve schwannoma should be differentiated (6).
In the present case, MRI localized the cystic lesion in the mastoid with extension into the canal and hypotympanum. The isointense signal relative to the brain on T1-weighted images, and non-enhancement with the use of gadolinium narrowed the differential diagnosis considerably to either a cholesterol cyst or a cholesteatoma. Despite the destruction of the canal wall in this case, there was no previous history of otitis media and the presence of a well-pneumatized mastoid and the dome-shaped dark blue mass displacing the lower half of the tympanic membrane were helpful to narrow the diagnosis. A cholesterol granuloma presents with a hyperintense signal on both T1- and T2-weighted images (7).
A cholesterol cyst in the mastoid can be treated by a simple mastoidectomy with marsupialization. In this case, it was necessary to perform a canal wall down mastoidectomy due to the large destruction of the canal wall and lateral wall of the hypotympanum. The exposed facial nerve was inspected carefully; it appeared edematous and inflamed. It is believed that removal of the cyst wall and granulation tissue is sufficient if the nerve is anatomically intact and opening the sheath of the facial nerve is unnecessary.
Acknowledgements
This study was supported by grants from the Ministry of Science and Technology (MOST), Korea, and from the Korea Science and Engineering Foundation through the Research Center for Resistant Cells (R13-2003-009).
- Received June 2, 2008.
- Revision received November 26, 2008.
- Accepted December 2, 2008.
- Copyright © 2009 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved
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