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Skull Base, Petrous Apex, Tumors Workup

  • Author: Michael J Fucci, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
 
Updated: Mar 03, 2016
 

Laboratory Studies

No specific laboratory evaluation is indicated in petrous apex lesions. Leukocytosis is often seen with infectious lesions, but, otherwise, laboratory findings are not helpful.

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Imaging Studies

Imaging studies are the primary method used to diagnose these lesions. CT scanning is often the initial study used in evaluating the lesions. Contrast enhancement is helpful in the diagnosis, and its administration is recommended if no contraindications exist.

MRI provides valuable information in accurately diagnosing these lesions. The CT scan and MRI characteristics of each petrous apex lesion are outlined in Tables 1 and 2, respectively.

Table 1. Petrous Apex Lesion Characteristics on CT Scanning* (Open Table in a new window)

Lesion Bone Erosion Eroded Margin Contralateral Apex Contrast Enhancement
Cholesterol granuloma + Smooth Highly pneumatized -
Cholesteatoma + Smooth Often not pneumatized -
Petrous apicitis + Irregular Variable -
Effusion - - Usually pneumatized -
Bone marrow asymmetry - - Variable -
Carotid aneurysm + Smooth Variable +
Neoplasia + Variable Variable +
*From Jackler RK and Parker D: The radiographic differential diagnosis of petrous apex lesions. AJO 1992;13:561-574[5]

Table 2. Petrous Apex Lesion Characteristics on MRI Scanning (Intensity Compared with Adjacent Brain)* (Open Table in a new window)

Lesion T1 Images T2 Images T1-Gadolinium
Cholesteatoma Hypo Hyper No enhancement
Cholesterol granuloma Hyper Markedly hyper No enhancement
Petrous apicitis Hypo Hyper Rim enhancement
Effusion Hypo Hyper Mucosal enhancement
Bone marrow asymmetry Hyper Hypo No enhancement
Neoplasia Hypo Hyper Enhancing
Carotid aneurysm Hypo Mixed Rim enhancement
*From Jackler RK and Parker D: The radiographic differential diagnosis of petrous apex lesions. AJO 1992;13:561-574[5]

Preoperative angiography is required for suspected aneurysms. In rare cases, branches of the external carotid artery supply these lesions and preoperative embolization may be beneficial. The status of the internal carotid artery and vertebral-basilar systems are important in determining whether the carotid artery can be sacrificed. A balloon occlusion test is occasionally used to determine the neurologic status from a unilateral carotid occlusion.

Arteriography remains helpful in determining other lesions responsible for pulsatile tinnitus, such as glomus tumors.

MRI arteriography and venography determine dural sinus patency, although angiography remains the diagnostic criterion standard.

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Diagnostic Procedures

See the list below:

  • Imaging studies, including CT scanning and MRI, usually narrow the differential diagnosis. MRI venography and angiography help in defining vascular lesions.
  • Preoperative histologic diagnosis is difficult because safe access to tissue is nearly impossible.
  • Cultures and sensitivities in bacterial disorders are helpful and are obtained from discharge within the ear canal or through a myringotomy.
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Histologic Findings

Infectious lesions and inflammatory lesions

Petrous apicitis shows a white cell infiltrate consistent with an abscess.

Congenital and acquired cholesteatoma show sheets of stratified keratinizing squamous epithelium without evidence of abnormal mitosis. Granulation tissue and fibrosis often surround them.

Cholesterol granulomas represent a foreign body granulomatous response to cholesterol crystals arising secondary to hemorrhage. Poor ventilation facilitates accumulation of byproducts.

Mucoceles are cysts lined by pseudostratified ciliated columnar epithelium. Fibrosis, granulation tissue, hemorrhage, and squamous metaplasia are common.

Neoplastic lesions

Chordomas are malignant neoplasms arising from the embryonic remnants of the notochord. This pseudoencapsulated tumor contains cells that are epithelioid with vesicular nuclei and abundant cytoplasm that appears granular to vacuolated. Extensive vacuolization can appear as soap bubbles, compressing the nucleus and creating the classic physaliferous cells.

Chondrosarcomas are malignant tumors of cartilage with lobulated hypercellular areas characterized by hyperchromatic pleomorphic nuclei and prominent nucleoli.

Meningiomas are benign neoplasms arising from arachnoid cells. Four subgroups of meningiomas exist: syncytial or meningothelial, fibroblastic, transitional (both syncytial and fibroblastic), and angioblastic. The cells are whorled, and the nuclei have a punched out or empty appearance resulting from intranuclear cytoplasmic inclusions. Psammoma bodies are typical in meningothelial meningiomas.

Schwannomas are benign tumors arising from Schwann cells, typically on the eighth cranial nerve. Antoni A areas are composed of compact spindle cells, and Antoni B areas are composed of loose hypocellular areas. Most tumors have a mixture of both types. The nuclei are vesicular to hyperchromatic, elongated, and twisted with cells arranged in short interlacing fascicles. Whorling or palisading of nuclei is common.

Glomus tumors are benign and arise from the extra-adrenal neural crest paraganglia. Cell nests or zellballen patterns are characteristic of paragangliomas. Chief cells primarily compose the tumor, with uniform nuclei, dispersed chromatin, and abundant eosinophilic, granular, or vacuolated cytoplasm. Mitosis and necrosis are rare. The chief cells are argyrophilic, and reticulin staining delineates the cell nests.

Nasopharyngeal carcinoma arises from the surface epithelium of the nasopharynx. The World Health Organization subtypes these squamous cell tumors into 3 histologic variants: keratinizing, nonkeratinizing, and undifferentiated.

Keratinizing tumors represent 25% of all nasopharyngeal tumors. This is a classic squamous cell carcinoma often graded as well, moderately, and poorly differentiated.

Nonkeratinizing tumors represent 15% of all nasopharyngeal carcinomas. The growth pattern is similar to transitional cell carcinoma of the bladder. No desmoplastic response to tissue invasion occurs.

Undifferentiated tumors account for 60% of nasopharyngeal tumors. A syncytial growth pattern with oval or round vesicular nuclei, prominent eosinophilic nucleoli, scant cytoplasm, and increased mitosis is noted. Lymphoepithelioma is incorrectly diagnosed in some of these cases because of a significant nonneoplastic lymphoid composition.

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Staging

No staging system currently exists for primary neoplasms of the petrous apex.

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Contributor Information and Disclosures
Author

Michael J Fucci, MD Medical Director, Arizona Hearing and Balance Center

Michael J Fucci, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Otolaryngology-Head and Neck Surgery, American Medical Association, Arizona Medical Association, American Neurotology Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Gerard J Gianoli, MD Clinical Associate Professor, Departments of Otolaryngology-Head and Neck Surgery and Pediatrics, Tulane University School of Medicine; President, The Ear and Balance Institute; Board of Directors, Ponchartrain Surgery Center

Gerard J Gianoli, MD is a member of the following medical societies: American Otological Society, Society of University Otolaryngologists-Head and Neck Surgeons, Triological Society, American Neurotology Society, American Academy of Otolaryngology-Head and Neck Surgery, American College of Surgeons

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Vesticon<br/>Received none from Vesticon, Inc. for board membership.

Chief Editor

Arlen D Meyers, MD, MBA Professor of Otolaryngology, Dentistry, and Engineering, University of Colorado School of Medicine

Arlen D Meyers, MD, MBA is a member of the following medical societies: American Academy of Facial Plastic and Reconstructive Surgery, American Academy of Otolaryngology-Head and Neck Surgery, American Head and Neck Society

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Cerescan;RxRevu;SymbiaAllergySolutions<br/>Received income in an amount equal to or greater than $250 from: Symbia<br/>Received from Allergy Solutions, Inc for board membership; Received honoraria from RxRevu for chief medical editor; Received salary from Medvoy for founder and president; Received consulting fee from Corvectra for senior medical advisor; Received ownership interest from Cerescan for consulting; Received consulting fee from Essiahealth for advisor; Received consulting fee from Carespan for advisor; Received consulting fee from Covidien for consulting.

Acknowledgements

Douglas D Backous, MD Director of Listen for Life Center, Department of Otolaryngology-Head and Neck Surgery, Virginia Mason Medical Center

Douglas D Backous, MD is a member of the following medical societies: American Academy of Otolaryngology-Head and Neck Surgery, American Auditory Society, American College of Surgeons, American Laryngological Rhinological and Otological Society, American Medical Association, Association for Research in Otolaryngology, North American Skull Base Society, Society for Neuroscience, and Washington State Medical Association

Disclosure: Nothing to disclose.

References
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Petrous apicitis. An axial CT scan of the temporal bone shows an air-fluid level within the right petrous apex and fluid within the middle ear space and mastoid.
Petrous apicitis. A coronal CT scan of the temporal bones shows an air-fluid level in the right petrous apex.
Cholesterol cyst. A coronal T1-weighted image of the temporal bone shows high-intensity signal in the left petrous apex.
Cholesterol cyst. An axial T2-weighted image shows a lesion in the left petrous apex.
Trigeminal schwannoma. An axial T1-weighted MRI shows an enhanced lesion of the left petrous apex.
Chondrosarcoma. An axial T1-weighted MRI image with gadolinium shows an enhanced mass in the petrous apex.
Nasopharyngeal carcinoma. An axial CT scan of the temporal bones shows a mass in the nasopharynx.
Nasopharyngeal carcinoma. An axial CT scan of the temporal bones shows an erosive and invasive mass of the left petrous apex.
Basal cell carcinoma. An axial T1-weighted MRI shows an isointense lesion of the left temporal bone that invaded the petrous apex.
Sigmoid sinus obstruction. An MRI venogram shows no flow in the left sigmoid sinus.
Table 1. Petrous Apex Lesion Characteristics on CT Scanning*
Lesion Bone Erosion Eroded Margin Contralateral Apex Contrast Enhancement
Cholesterol granuloma + Smooth Highly pneumatized -
Cholesteatoma + Smooth Often not pneumatized -
Petrous apicitis + Irregular Variable -
Effusion - - Usually pneumatized -
Bone marrow asymmetry - - Variable -
Carotid aneurysm + Smooth Variable +
Neoplasia + Variable Variable +
*From Jackler RK and Parker D: The radiographic differential diagnosis of petrous apex lesions. AJO 1992;13:561-574[5]
Table 2. Petrous Apex Lesion Characteristics on MRI Scanning (Intensity Compared with Adjacent Brain)*
Lesion T1 Images T2 Images T1-Gadolinium
Cholesteatoma Hypo Hyper No enhancement
Cholesterol granuloma Hyper Markedly hyper No enhancement
Petrous apicitis Hypo Hyper Rim enhancement
Effusion Hypo Hyper Mucosal enhancement
Bone marrow asymmetry Hyper Hypo No enhancement
Neoplasia Hypo Hyper Enhancing
Carotid aneurysm Hypo Mixed Rim enhancement
*From Jackler RK and Parker D: The radiographic differential diagnosis of petrous apex lesions. AJO 1992;13:561-574[5]
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