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|LETTER TO EDITOR
|Year : 2011 | Volume
| Issue : 6 | Page : 927-929
Cholesterol granuloma of the petrous apex: A benign lesion with aggressive behavior
Vijay Bohra1, SS Sangha1, Sunil Goyal2, G Manoj3
1 Department of Internal Medicine, Armed Forces Medical College, Pune, India
2 Department of ENT, 151 Base Hospital, Guwahati, India
3 Department of Pathology, Armed Forces Medical College, Pune, India
|Date of Submission||29-Aug-2011|
|Date of Decision||30-Aug-2011|
|Date of Acceptance||28-Sep-2011|
|Date of Web Publication||2-Jan-2012|
Department of Internal Medicine, Armed Forces Medical College, Pune
|How to cite this article:|
Bohra V, Sangha S S, Goyal S, Manoj G. Cholesterol granuloma of the petrous apex: A benign lesion with aggressive behavior. Neurol India 2011;59:927-9
Cholesterol granulomas (CGs) of the petrous apex are uncommon benign lesions, often with an indolent course. We report a case of CG with an unusually aggressive behavior.
A 28-year-old male sailor presented to the emergency department with severe, throbbing right hemicranial headache, tinnitus, vertigo and two episodes of non-projectile vomiting of one-day duration. At admission he was in agonizing pain and would prefer to lie supine and still and his vitals were normal. Neurological examination revealed Grade I rotatory nystagmus with fast component to the right, positive Rinne's test, and Weber's test lateralized to the left ear. There was no mastoid tenderness, aural discharge, or hyperemia of tympanic membranes. Over the next 12 h he developed diplopia and slurring of speech. Repeat neurological examination revealed right lower motor facial palsy (House-Brackmann classification: Grade II), right lateral gaze palsy, and hypoesthesia in the distribution of the maxillary division of the trigeminal nerve. Contrast computed tomography (CCT) head scan revealed a well-defined, sharply marginated, lobulated hypodense mass lesion measuring 3.4 × 2.9 × 3.1 cm in the right petrous apex. The lesion was seen eroding the posterior surface of the petrous bone, porus acousticus and the posterior wall of the carotid canal. A non-enhancing expansile lesion was also seen in the left petrous apex [Figure 1]. Magnetic resonance imaging (MRI) of brain revealed a well-defined lesion in the right petrous apex which was hyperintense on both T1 and T2-weighted images. The lesion had a fluid-fluid level with mass effect on the right V, VII, and VIII cranial nerves with protrusion into the middle cranial fossa [Figure 2]a and b. A similar but smaller lesion was seen in the left petrous apex as well. Patient underwent endoscopic drainage and resection of cyst wall through transsphenoidal approach. A brownish fluid was drained along with debris. Histopathological examination revealed irregular cholesterol clefts surrounded by multinucleated foreign body giant cells and histiocytes [Figure 3]. Evidence of fresh hemorrhages and hemosiderin deposits were also seen confirming the diagnosis of CG. Patient tolerated the procedure well and the postoperative period was uneventful.
|Figure 1: CCT showing well-defined hypodense mass lesion in the right petrous apex (arrow). A non-enhancing expansile lesion was also seen in the left petrous apex (arrow head)|
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|Figure 2: MRI brain showing cholesterol granuloma in the right (arrow) and left (arrowhead) petrous apex (a). Lesion of the right petrous apex with a fluid-fluid level with mass effect on the right-sided V, VII and VIII cranial nerves with protrusion into the middle cranial fossa (b)|
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|Figure 3: Microphotograph showing granulation tissue, multinucleated giant cells, clefts of cholesterol crystals and fresh hemorrhages|
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CGs of the petrous apex are rare because the petrous apex is pneumatized in only 20-30% of temporal bones  and the reported incidence is less than 0.6 cases per million population. These lesions are indolent and remain clinically silent until they involve the adjacent cranial nerves and anatomical structures and the symptoms include imbalance, hearing loss, facial weakness, and/or diplopia. Differentiating CGs from other lesions of the petrous apex is challenging. Other mass lesions in the same anatomical location include cholesteatoma, epidermoid cyst, mucocele, chordoma, petrous apicitis and metastasis.  On CT scan CGs are non-enhancing and well marginated with frequent bone erosion. CGs on MRI show high signal intensities on both T1- (T1WI) and T2-weighted (T2WI) images and do not enhance on gadolinium administration. On the contrary cholesteatomas and petrous apicitis are hypointense on T1WI and hyperintense on T2WI.  Preoperative study of the extent of lesion using MRI and high-resolution CT scan is mandatory to define the anatomy of the VII cranial nerve, jugular bulb, bony labyrinth, sigmoid sinus, internal carotid artery and posterior wall of the sphenoid.
CGs of the petrous apex are reported to be more aggressive than CGs of the middle ear. , Macroscopic distinction between a benign and an aggressive CG has been described by Martin et al,  in the benign variant agglomeration of cholesterol- rich fluid is the feature while the aggressive variants have a cystic cavity with a thick wall of inflammatory tissue. The petrous apex lesions are considered to be more aggressive due to the persistence of the hematopoietic rests in the petrous apex even in adulthood. However, such an aggressive nature of petrous apex CG as seen in our patient has not been documented earlier in the literature. Possibly the aggressive course in our case can be explained by recent hemorrhage (fluid-fluid level in the MRI) which would have led to sudden increase in the volume of the lesion.
Treatment strategies for CGs of the petrous apex include drainage and excision of the capsule or drainage of the cyst. Surgical approaches depend on the location, complex anatomy of surrounding structures, extension of the lesion and degree and quality of hearing. The trans-sphenoidal, transclival approach in such cases would provide drainage of the lesion bilaterally into the paranasal sinus system and preserves hearing, although it may place the optic nerve at risk. 
| » References|| |
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|2.||Hentschel S, Durity F. Petrous apex granulomas. CT and MR imaging. Can J Neurol Sci 2002;29:169-70. |
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[Figure 1], [Figure 2], [Figure 3]