Cholesteatoma is a non-neoplastic but locally aggressive lesion characterized by abnormal accumulation of keratinized squamous epithelium in the middle ear and/or mastoid cavity. The acquired type is most common, developing from a pars flaccida retraction pocket and originating in Prussak space. The congenital type appears as a white mass medial to the tympanic membrane, behind a normal eardrum. Bone erosion (scutum, ossicular chain, tegmen tympani, lateral semicircular canal, facial nerve canal) forms the cornerstone of cholesteatoma diagnosis and differentiates it from effusion/granulation in chronic otitis media. HRCT is the gold standard for bone detail, and DWI MRI (non-EPI technique) is pathognomonic for cholesteatoma tissue detection (keratin shows diffusion restriction). In postoperative follow-up, DWI MRI has replaced second-look surgery for residual/recurrence screening.
Age Range
10-70
Peak Age
40
Gender
Equal
Prevalence
Common
Acquired cholesteatoma begins with retraction pocket formation in the pars flaccida portion of the tympanic membrane. This retraction pocket forms due to Eustachian tube dysfunction and negative middle ear pressure. Keratin accumulation progressively grows within the pocket and compresses surrounding structures. Bone erosion occurs through three mechanisms: (1) direct osteolytic effect through release of collagenase, acid phosphatase, and other proteolytic enzymes, (2) osteoclast activation mediated by chronic inflammation and granulation tissue, (3) mechanical pressure effect (from the growing mass). Keratin tissue shows marked restriction on diffusion-weighted imaging (DWI) due to high macromolecular density and tight junctions between cell membranes — water molecules cannot freely move within the keratin matrix. This physical property is the most reliable finding for differentiating cholesteatoma tissue from granulation tissue and effusion by MRI. The absence of enhancement on CT reflects the avascular nature of cholesteatoma tissue — granulation tissue has a rich vascular network and therefore shows avid enhancement.
On non-EPI DWI MRI, cholesteatoma shows markedly bright signal at b=1000 with low signal on ADC map. This finding reflects restricted water diffusion in keratin tissue and is pathognomonic for cholesteatoma. Granulation tissue does not show restriction on DWI.
On thin-section temporal bone CT (0.5-0.6mm), a non-dependent soft tissue density mass is seen in Prussak space (pars flaccida region) or mesotympanum. Scutum (lateral attic wall) erosion is pathognomonic for acquired pars flaccida cholesteatoma. The soft tissue does not move with dependent positioning — this differentiates from effusion. The middle ear cavity may be expanded. Incus and malleus handle erosion commonly coexist.
Report Sentence
A non-dependent soft tissue mass in Prussak space with associated scutum erosion is seen in the right/left temporal bone, findings consistent with acquired pars flaccida cholesteatoma.
As cholesteatoma grows, it causes ossicular chain erosion. The long process of incus is most commonly affected (80%), followed by incus body, stapes superstructure, and malleus head. Ossicular destruction determines the degree of conductive hearing loss. Complete loss of incus long process and incudostapedial joint separation (desiccated incus) is highly specific for cholesteatoma.
Report Sentence
Erosion/destruction of the incus long process is seen, consistent with ossicular chain involvement by cholesteatoma.
On non-EPI DWI MRI (HASTE-DWI, PROPELLER-DWI, or multi-shot EPI), cholesteatoma shows markedly bright signal at b=1000. Low signal on ADC map (true restriction). EPI-based DWI is inadequate in the temporal bone due to susceptibility artifact — non-EPI techniques are mandatory. Cholesteatoma residuals as small as 2-3mm can be detected by non-EPI DWI. This finding has replaced second-look surgery in postoperative follow-up.
Report Sentence
A focus of marked diffusion restriction on non-EPI diffusion-weighted imaging is seen in the right/left middle ear/mastoid, consistent with residual/recurrent cholesteatoma.
On contrast-enhanced MRI, cholesteatoma shows no enhancement — this is critical in differential diagnosis from granulation tissue (which shows avid enhancement). The inflammatory mucosa and granulation tissue surrounding cholesteatoma may enhance, but the cholesteatoma matrix itself is avascular. This finding combined with DWI increases diagnostic reliability of cholesteatoma.
Report Sentence
The lesion shows no enhancement on contrast-enhanced sequences, consistent with avascular cholesteatoma matrix; surrounding mucosal/granulomatous enhancement reflects chronic inflammatory changes.
Tegmen tympani (middle ear roof, middle cranial fossa floor) erosion is an important indicator of cholesteatoma complication. Intradural extension signals risk of meningoencephalic herniation, meningoencephalitis, or temporal lobe abscess. Coronal reformat is the best plane to demonstrate this erosion. Disruption of tegmen continuity is critical information for surgical planning.
Report Sentence
Focal bone erosion of the tegmen tympani is seen, indicating risk of intracranial complication from cholesteatoma; neurosurgical consultation is recommended.
On T2-weighted sequences, cholesteatoma shows hyperintense signal — however this finding is non-specific, as effusion and granulation tissue may also be hyperintense. Cholesteatoma appears as iso- to hypointense mass on T1, hyperintense on T2. Diagnostic value increases when evaluated with DWI. High-resolution T2 sequences (3D CISS, DRIVE) show inner ear structures and cholesteatoma extension in detail.
Report Sentence
A lesion showing hyperintense signal in the right/left middle ear/mastoid on T2-weighted sequences is seen; correlation with diffusion-weighted imaging is recommended.
Criteria
Originates from Prussak space, scutum erosion, most common type (80%). Grows medially in the epitympanic recess.
Distinct Features
Scutum erosion pathognomonic, incus long process erosion common, spreads to mastoid antrum and aditus.
Criteria
Originates from pars tensa retraction pocket, develops in sinus tympani and posterior mesotympanum. Less common (15-20%).
Distinct Features
Located in sinus tympani and facial recess region, surgical access more difficult, higher recurrence risk.
Criteria
White mass behind intact tympanic membrane, no otitis history, no retraction pocket. Usually in children (<5 years).
Distinct Features
Most common in anterior superior quadrant, tympanic membrane intact, white mass on otoscopy, anterosuperior soft tissue on CT.
Distinguishing Feature
Chronic otitis media shows NO DWI restriction and granulation tissue enhances; cholesteatoma is bright on DWI with no enhancement
Distinguishing Feature
Glomus tympanicum enhances avidly (hypervascular) and is localized on promontory; cholesteatoma does not enhance and is in Prussak/epitympanum
Distinguishing Feature
Vestibular schwannoma is located in IAC and enhances avidly; cholesteatoma is in the middle ear and does not enhance
Urgency
urgentManagement
surgicalBiopsy
Not NeededFollow-up
6-monthCholesteatoma requires surgical excision (tympanomastoidectomy); untreated cases develop serious complications through bone erosion (facial nerve paralysis, labyrinthine fistula, intracranial abscess, meningitis, sigmoid sinus thrombosis). Postoperative non-EPI DWI MRI at 12 months is the gold standard for residual/recurrence screening and has largely eliminated second-look surgery. Surgical urgency increases when tegmen or lateral semicircular canal erosion is detected.
Untreated cholesteatoma causes serious complications through bone erosion: facial nerve paralysis, labyrinthine fistula, intracranial abscess, sigmoid sinus thrombosis. Surgical excision (tympanomastoidectomy) is the mainstay of treatment. DWI MRI is the gold standard for postoperative residual/recurrence surveillance.