cholesteatoma

**Definition:** A non-neoplastic cyst-like collection of desquamated keratin lined by keratinizing squamous epithelium (with underlying perimatrix/granulation tissue) in the middle ear or mastoid. The name is a misnomer: it has no cholesterol and is not a tumor ("-oma").

**Types and pathophysiology:** - *Acquired (most common):* Chronic Eustachian tube dysfunction causes negative middle ear pressure. This retracts the tympanic membrane, usually the pars flaccida in the attic (epitympanum), forming a retraction pocket. Keratin accumulates in the pocket and cannot be cleared. Other mechanisms include perforation with epithelial migration inward, and implantation after trauma or surgery. Chronic otitis media is a major association. - *Congenital:* An epithelial rest behind an intact tympanic membrane in a child with no history of infection, perforation, or ear surgery. It is classically seen in the anterior-superior quadrant. - The mass expands and is locally destructive. Bone resorption is driven by inflammatory mediators (e.g., IL-1, TNF-α, MMPs) and osteoclast activation. The ossicles (especially the long process of the incus) are eroded first.

**Clinical features:** - Chronic, painless, foul-smelling otorrhea that is refractory to antibiotics - Conductive hearing loss (ossicular erosion) - Otoscopy: white/pearly debris-filled mass behind the tympanic membrane, or an attic retraction pocket or perforation - Possible tinnitus, vertigo, or ear fullness

**Complications (from bony erosion):** - Facial nerve (CN VII) palsy via erosion of the fallopian canal (tympanic segment) - Labyrinthine fistula (horizontal semicircular canal) → vertigo, sensorineural hearing loss - Mastoiditis - Intracranial extension: meningitis, epidural/brain abscess, sigmoid sinus thrombosis - Tegmen tympani erosion → CSF leak

**Diagnosis:** Clinical (otoscopy/otomicroscopy). Audiometry shows conductive hearing loss. High-resolution CT of the temporal bone shows a soft-tissue mass with bony erosion. MRI with diffusion-weighted imaging helps differentiate it from granulation tissue and detects recurrence.

**Treatment:** Surgical excision (tympanomastoidectomy). Antibiotic drops treat infection temporarily but are not definitive. Recurrence is common, so follow-up and sometimes second-look surgery are needed.

**Boards pearls:** - "Pearly white mass behind the TM + chronic foul otorrhea + conductive hearing loss" → cholesteatoma - Acquired cases are typically from the pars flaccida (attic) - Most common complication is hearing loss; know the facial nerve palsy and labyrinthine fistula associations - Differential: chronic suppurative otitis media, tympanosclerosis (chalky white plaques in the TM, not a mass), glomus tympanicum (pulsatile tinnitus, red mass)