What is Mastoid Cholesteatoma?
A mastoid cholesteatoma is a benign but progressive cystic lesion composed of keratinized squamous epithelium that develops within the mastoid portion of the temporal bone, capable of causing extensive bone erosion and serious complications if left untreated. 1
Pathophysiology and Classification
Cholesteatomas are non-neoplastic lesions characterized by progressive accumulation and exfoliation of squamous epithelium. 2 They can be classified into two main types:
- Acquired cholesteatomas: Most common, typically resulting from chronic otitis media with tympanic membrane perforation or retraction pockets 1
- Congenital cholesteatomas: Rare (up to 5% of all cholesteatomas), arising from embryologic epithelial rests, with isolated mastoid involvement being exceptionally uncommon 3, 4
Clinical Presentation
Common Symptoms
- Painless otorrhea is the typical presenting symptom in acquired cases 1
- Unilateral conductive hearing loss with or without tinnitus and dizziness 2
- Retro-auricular pain and swelling in the temporal area, particularly in congenital mastoid cholesteatomas 4
Important Clinical Pitfall
Patients with unilateral conductive hearing loss who have a normal tympanic membrane on examination should raise suspicion for a progressive cholesteatoma, as mastoid cholesteatomas can remain subclinical for many years before causing symptoms. 2, 4 The location of mastoid cholesteatomas allows for considerable growth before symptoms develop, which can lead to diagnostic challenges. 4
Anatomic Extent and Complications
Mastoid cholesteatomas can cause:
- Ossicular erosion (malleus, incus necrosis) 5
- Lateral semicircular canal erosion 5
- Facial canal dehiscence 5
- Tegmen erosion with potential intracranial extension 5, 2
- Scutum erosion 5
- In rare cases, extension into the foramen magnum or development of epidural abscess 2, 6
Diagnostic Approach
Imaging Strategy
CT temporal bone without IV contrast is the cornerstone imaging modality for diagnosis and presurgical planning, providing excellent anatomic detail of bony structures and determining the extent of disease. 1, 7
- CT accurately detects ossicular erosion, scutum erosion, tegmen erosion, and lateral semicircular canal erosion 1
- MRI with diffusion-weighted imaging (DWI) is essential for tissue characterization, differentiating cholesteatoma from scar tissue, granulation tissue, and other soft tissue pathology with high sensitivity and specificity 1
Avoid These Pitfalls
- Do not order CT with IV contrast for cholesteatoma evaluation, as it provides no additional necessary bony detail 1
- Plain radiography has no role in cholesteatoma diagnosis 1
- Do not rely on CT alone for tissue characterization due to poor specificity 1
Management Principles
Any patient with suspected cholesteatoma should be referred to an otolaryngologist for definitive management, as surgery is the treatment of choice. 1, 3 Preoperative HRCT combined with audiological assessment provides good estimates of ossicular erosion degree and guides surgical approach. 1
Postoperative Surveillance
- CT temporal bone without IV contrast is the primary modality for detecting recurrent cholesteatoma by identifying abnormal, new, or enlarging lobulated material 1
- MRI with DWI and delayed postcontrast T1-weighted imaging differentiates recurrent cholesteatoma from postoperative granulation tissue and scar 1
Special Considerations
Long-standing cholesteatomas can be a precursor for squamous cell carcinoma, and the enormity of lesions with extensive bony erosions can raise strong clinical suspicion of malignancy. 8 However, histopathological examination confirms the benign nature of cholesteatoma despite its locally aggressive behavior.