Cholesteatoma

A cholesteatoma is a destructive, expanding "skin in the wrong place" — keratinising stratified squamous epithelium trapped within the middle ear cleft. Despite the misleading name it contains neither cholesterol nor is it a true tumour; it is a high-yield ENT topic because of its relentless bone erosion and life-threatening intracranial complications.

Definition & basic concept

Cholesteatoma is the presence of keratinising squamous epithelium (skin) within the middle ear and/or mastoid, where it does not normally belong. The epithelium forms a sac that continuously desquamates keratin into a closed space; the trapped keratin cannot escape, so the sac enlarges, gets secondarily infected, and erodes surrounding bone.

The classic description has three zones:

1. Cystic content — central mass of keratin debris (the "amorphous" core).
2. Matrix — the keratinising squamous epithelium lining the sac.
3. Perimatrix (lamina propria) — subepithelial connective tissue containing the osteolytic enzymes that destroy bone.

High-yield: Cholesteatoma is "skin in the wrong place." It is NOT a neoplasm and contains NO cholesterol — the name is a historical misnomer (Johannes Müller, 1838). Do not confuse it with cholesterol granuloma (a foreign-body giant cell reaction to cholesterol crystals, blue-domed/bluish drum, treated by drainage).

Classification

Cholesteatomas are broadly divided into congenital and acquired; acquired is further split into primary and secondary.

Feature	Congenital	Primary acquired	Secondary acquired
Origin	Embryonic epidermal rest behind intact drum	Retraction pocket (attic/pars flaccida)	Through a pre-existing perforation (pars tensa)
Drum status	Intact tympanic membrane	Intact but retracted	Perforated (usually marginal/attic)
Classic site	Anterosuperior quadrant (white mass)	Attic / pars flaccida	Posterosuperior quadrant / attic
Typical age	Children (2–5 yrs)	Older children / adults	Any age, post-infective
Associated otorrhoea	Usually absent	Scanty foul discharge	Profuse foul discharge

High-yield: Congenital cholesteatoma = white pearly mass behind an INTACT drum, no prior otorrhoea/perforation/surgery, classically anterosuperior quadrant in a child. This is the favourite single-best-answer trigger.

Levenson criteria for congenital cholesteatoma: white mass medial to a normal pars tensa, normal pars flaccida and tensa, no history of otorrhoea or perforation, and no prior otologic surgery.

Etiology & pathogenesis (theories)

Acquired cholesteatoma arises by several proposed mechanisms — examiners love these:

1. Invagination / retraction pocket theory (Wittmaack) — the most accepted for primary acquired. Eustachian tube dysfunction → persistent negative middle-ear pressure → retraction of the weakest part of the drum (pars flaccida / attic) → a pocket forms that traps keratin.
2. Migration / immigration theory (Habermann) — squamous epithelium migrates through a pre-existing marginal perforation into the middle ear → secondary acquired.
3. Basal cell hyperplasia (Ruedi) — proliferating basal cells of pars flaccida invade the subepithelial space via "cones."
4. Squamous metaplasia (Sadé) — middle-ear mucosa undergoes metaplasia to keratinising squamous epithelium under chronic inflammation.

High-yield: Primary acquired = invagination (retraction) of pars flaccida. Secondary acquired = migration through a (marginal) perforation. Pin this dichotomy.

How the bone is destroyed (the money point)

Bone erosion is not simply pressure necrosis. The perimatrix is biologically active:

• Enzymatic osteolysis — release of collagenase, acid phosphatase, and matrix metalloproteinases.
• Osteoclast activation — driven by cytokines (IL-1, IL-6, TNF-α) and RANKL.
• Pressure necrosis of the expanding sac contributes secondarily.

High-yield: The enzyme classically credited with bone erosion in cholesteatoma is collagenase. The most commonly eroded ossicle is the long process of incus; the commonest bony site of erosion overall is the scutum (attic), and the lateral semicircular canal is the commonest site of labyrinthine fistula.

Atticoantral vs tubotympanic CSOM

Cholesteatoma defines the atticoantral (unsafe) type of chronic suppurative otitis media. Distinguishing it from the benign tubotympanic (safe) type is heavily tested.

Feature	Tubotympanic ("safe")	Atticoantral ("unsafe") = cholesteatoma
Perforation	Central (pars tensa)	Marginal or attic (pars flaccida)
Discharge	Profuse, mucoid, odourless	Scanty, purulent, foul-smelling
Cholesteatoma	Absent	Present
Bone erosion / granulations	Absent	Present (cholesteatoma, granulation tissue, polyp)
Complications	Rare	Common & dangerous
Hearing loss	Mild–moderate conductive	Variable; may have a false negative (erosion bridging ossicles conducts sound)

High-yield: A foul-smelling scanty ear discharge is the hallmark of cholesteatoma — the smell is due to osteitis/saprophytic infection. Central perforation = safe; marginal/attic perforation = unsafe.

Clinical features

• Otorrhoea — scanty, persistent, foul-smelling, sometimes blood-tinged; classically does not respond to conventional aural toilet/antibiotics.
• Hearing loss — usually conductive (ossicular erosion); may become mixed/sensorineural if labyrinth is breached. A peculiar feature: hearing may be paradoxically preserved when the cholesteatoma bridges an eroded ossicular gap ("cholesteatoma hearer").
• Otoscopy — attic/posterosuperior retraction pocket, an attic perforation filled with whitish flakes, keratin debris, or an aural polyp. A bleeding granulation/polyp on the posterosuperior canal wall is suspicious.
• Tinnitus, vertigo, otalgia — late; vertigo suggests a labyrinthine fistula.
• Facial weakness / headache / fever — herald complications.

High-yield: A fistula test (applying positive pressure with Siegle's speculum → vertigo + nystagmus) is positive when there is a labyrinthine (lateral semicircular canal) fistula — a strong sign of an erosive cholesteatoma. A false-negative fistula test occurs in a dead labyrinth.

Diagnosis & investigation of choice

Diagnosis is primarily clinical (otoscopy/otomicroscopy), supported by imaging.

Diagnostic flow: Otomicroscopy (debris/retraction pocket) → Pure tone audiometry (type & degree of hearing loss) → HRCT temporal bone (bony anatomy & extent) → DW-MRI (residual/recurrent disease) → confirm at surgery + histopathology.

HRCT temporal bone — investigation of choice for bony detail

• Non-dependent soft-tissue mass in attic / Prussak's space / antrum.
• Bone erosion: scutum blunting, ossicular erosion, widening of the aditus/antrum, erosion of tegmen tympani or sigmoid plate.
• Lateral semicircular canal fistula, facial canal dehiscence.
• HRCT cannot reliably distinguish cholesteatoma from granulation tissue/effusion (both are soft-tissue density).

Diffusion-weighted MRI — investigation of choice for "is it cholesteatoma?"

• Non-echo-planar (non-EPI) DWI shows cholesteatoma as a bright (restricted diffusion) lesion — high signal — because of its keratin content.
• Best modality for detecting residual or recurrent disease and avoiding "second-look" surgery.

High-yield: HRCT temporal bone = best for bony anatomy/extent and surgical planning. Non-EPI DWI MRI = best for confirming cholesteatoma vs granulation and for residual/recurrent disease (shows restricted diffusion / bright on DWI).

Management

Cholesteatoma is a surgical disease — there is no medical cure. The aims, in order: (1) eradicate disease and render the ear safe & dry, (2) prevent/treat complications, (3) preserve/restore hearing. Safety first, hearing second.

Medical therapy (aural toilet, topical antibiotic–steroid drops, oral antibiotics) is only adjunctive — to control active infection before surgery; it never substitutes for surgery.

Surgical approaches

The core operation is mastoidectomy to exenterate disease, choosing between two philosophies:

	Canal-Wall-Up (CWU) = intact canal wall / combined approach tympanoplasty	Canal-Wall-Down (CWD) = modified radical / radical mastoidectomy
Posterior bony canal wall	Preserved	Removed (creates a common cavity)
Anatomy	More physiological, dry ear, easier hearing aid	Open mastoid cavity needs lifelong care
Recurrence/residual disease	Higher — often needs a planned "second look"	Lower
Mastoid bowl care	Not needed	Needs periodic cleaning; water precautions
Best for	Limited disease, good ET function, reliable follow-up	Extensive disease, only/better hearing ear at risk, poor follow-up, labyrinthine fistula, sclerotic mastoid

• Modified radical mastoidectomy (Bondy) — removes disease, preserves the middle ear/ossicles and hence hearing; the standard CWD operation for most cholesteatomas.
• Radical mastoidectomy — removes the entire middle-ear contents (drum remnant, malleus, incus) leaving only the stapes footplate and Eustachian tube orifice; reserved for extensive disease/complications; poor hearing outcome.
• Atticotomy / atticoantrostomy — for limited attic disease.
• Tympanoplasty ± ossiculoplasty — to reconstruct hearing, often staged.

High-yield: CWU vs CWD: CWU preserves the canal wall and gives a better, more physiological ear but has a higher residual/recurrent rate (mandating a second-look operation in ~6–12 months); CWD has the lowest recurrence but leaves a mastoid cavity needing lifelong care. Modified radical mastoidectomy preserves hearing; radical mastoidectomy sacrifices it.

Complications

Cholesteatoma complications follow the route of bony erosion and are split into intratemporal (extracranial) and intracranial.

Spread map: erosion of scutum/attic → labyrinthine fistula (lateral SCC) → facial canal (facial palsy) → tegmen (extradural abscess, temporal lobe abscess, meningitis) → sigmoid plate (sigmoid sinus thrombosis) → petrous apex (Gradenigo).

Intratemporal (extracranial)	Intracranial
Mastoiditis (coalescent), subperiosteal abscess	Meningitis (commonest intracranial complication)
Labyrinthine fistula / labyrinthitis (lateral SCC)	Extradural / subdural abscess
Facial nerve palsy (LMN)	Temporal lobe abscess & cerebellar abscess
Petrositis → Gradenigo syndrome	Lateral (sigmoid) sinus thrombophlebitis
Sensorineural hearing loss	Otitic hydrocephalus

High-yield: Meningitis is the most common intracranial complication of cholesteatoma; the temporal lobe is the commonest site of an otogenic brain abscess (cerebellar abscess is the second). Gradenigo's triad = otorrhoea + retro-orbital pain (V) + lateral rectus palsy (VI) from petrous apicitis.

High-yield: Citelli's abscess = subperiosteal abscess in the digastric/occipital region; Bezold's abscess = pus tracking through the mastoid tip into the sternocleidomastoid/upper neck; Luc's abscess = pus deep to the temporalis. Griesinger's sign (oedema over the mastoid emissary vein) suggests sigmoid sinus thrombosis.

Key differentials

• Cholesterol granuloma — bluish/blue-domed intact drum, foreign-body reaction to cholesterol crystals; not skin; treated by drainage/ventilation. (Most common cause of a primary petrous apex cystic lesion.)
• Granulation tissue / aural polyp — bleeds on touch, arises from middle-ear mucosa; HRCT density overlaps with cholesteatoma — DWI distinguishes.
• Tympanosclerosis / myringosclerosis — chalky white plaques in the drum, not a sac of keratin.
• Keratosis obturans — keratin plug filling the bony external auditory canal (not middle ear), bilateral, in young patients, associated with bronchiectasis/sinusitis; canal is widened circumferentially (vs EAC cholesteatoma which causes localised bony erosion in older patients, often painful).
• Glomus tumour — pulsatile reddish retrotympanic mass, rising sun sign, Brown's sign positive.
• Congenital epidermoid of the petrous apex / CPA — DWI bright, same tissue but different location.

	Keratosis obturans	EAC cholesteatoma
Age	Young	Older adults
Laterality	Often bilateral	Usually unilateral
Pain / discharge	Painful, no discharge	Discharge, dull ache
Canal change	Circumferential widening	Localised erosion/sequestrum
Association	Bronchiectasis, sinusitis	Idiopathic / post-trauma

Mnemonics & named points

• "CHOLESTEAToma erodes via Collagenase" — link the C's.
• Intracranial complications — "MEALS-B": Meningitis, Extradural abscess, Abscess (brain), Lateral sinus thrombosis, Subdural abscess, B = otitic hydrocephalus (Brain swelling). Meningitis first (commonest).
• Prussak's space — the attic recess between the pars flaccida laterally and the neck of malleus medially; the earliest site of primary acquired cholesteatoma.
• Levenson criteria — congenital cholesteatoma. Bondy — modified radical mastoidectomy. Wittmaack (invagination), Habermann (migration), Ruedi (basal hyperplasia), Sadé (metaplasia).

Recently asked / exam angle

• Single-best-answer: "White mass behind an intact drum in a 4-year-old with no h/o ear discharge or surgery" → Congenital cholesteatoma (Levenson criteria).
• Enzyme responsible for bone destruction → Collagenase (also accept matrix metalloproteinases / osteoclast activation).
• Investigation of choice to differentiate cholesteatoma from granulation tissue / detect residual disease → Non-EPI Diffusion-Weighted MRI (restricted diffusion, bright); HRCT for bony extent.
• Most common ossicle eroded → long process of incus; commonest labyrinthine fistula site → lateral (horizontal) semicircular canal.
• Most common intracranial complication → meningitis; commonest site of otogenic abscess → temporal lobe.
• CWU vs CWD matching: higher recurrence → CWU; lowest recurrence but needs cavity care → CWD.
• Type of perforation: marginal/attic = unsafe (cholesteatoma); central = safe.
• Fistula test positive → labyrinthine fistula; Griesinger's sign → sigmoid sinus thrombosis; Gradenigo triad → petrous apicitis.
• Image-based: HRCT showing non-dependent attic soft tissue with scutum erosion → cholesteatoma.

Rapid revision

1. Cholesteatoma = keratinising squamous epithelium (skin) in the middle ear/mastoid — not a tumour, no cholesterol.
2. Congenital → intact drum, anterosuperior white mass, child; Levenson criteria.
3. Primary acquired → invagination of pars flaccida (retraction pocket, Wittmaack); secondary acquired → migration through a marginal perforation (Habermann).
4. Bone erosion via collagenase + osteoclast (RANKL/cytokines), not mere pressure.
5. Hallmark = scanty, foul-smelling otorrhoea with a marginal/attic perforation = unsafe (atticoantral) CSOM.
6. Prussak's space = earliest site; scutum = commonest bony erosion; long process of incus = commonest ossicular erosion.
7. HRCT temporal bone = bony extent/planning; non-EPI DWI MRI = confirm cholesteatoma & residual disease (bright/restricted diffusion).
8. Treatment is surgical — mastoidectomy; medical therapy only adjunctive. Safety > hearing.
9. CWU = higher recurrence, needs second look; CWD/modified radical (Bondy) = lowest recurrence, preserves hearing, needs cavity care.
10. Lateral SCC = commonest fistula; positive fistula test = labyrinthine fistula.
11. Meningitis = commonest intracranial complication; temporal lobe = commonest brain abscess site.
12. Know the named abscesses (Bezold, Citelli, Luc), Griesinger's sign, Gradenigo's triad, and differentials cholesterol granuloma & keratosis obturans.