Describe keratosis obturans and external canal cholesteatoma.

Keratosis Obturans

• It is a disorder of the migration mechanism, not of wax. The keratin that should be carried outward accumulates instead, forming a hard, laminated, pearly-white plug that is firmly adherent and quite unlike wax
• It occurs in younger patients, is frequently bilateral, and has a recognised association with bronchiectasis and chronic sinusitis — suggesting a generalised abnormality of ciliary or epithelial function.

External Canal Cholesteatoma

• External canal (external auditory) cholesteatoma is invasion of localised bone by squamous epithelium, with bony erosion and sequestration, of the inferior or posterior canal wall
• It is a fundamentally different process from keratosis obturans, and the two are set as a comparison because they were once confused: keratosis obturans is a circumferential accumulation without erosion; canal cholesteatoma is a localised erosion of bone
• It occurs in older patients, is unilateral, and may be spontaneous (idiopathic) or secondary to trauma, previous ear surgery, radiotherapy, canal stenosis or obstruction
• Symptoms — dull, chronic pain and chronic otorrhoea; the hearing is normal unless the disease is extensive.
• Signs — a localised pocket of keratin debris overlying exposed, eroded bone, with granulation tissue and sometimes a visible bony sequestrum
• Investigation — high-resolution CT defines the extent of bony erosion and its relation to the facial nerve, mastoid and temporomandibular joint
• Biopsy IS essential, because the appearance of granulations over eroded bone in an older patient is exactly that of carcinoma of the canal and of malignant otitis externa. This differential is the reason the condition matters
• Treatment — surgical: removal of the keratin and sequestra, drilling out the diseased bone, and canalplasty with skin grafting to create a wide, self-cleaning canal. Small lesions may be managed by regular debridement in an unfit patient
• Complications if neglected — extension into the mastoid, the middle ear, the temporomandibular joint and to the facial nerve, causing palsy; and labyrinthine fistula
• Follow up long term, since recurrence and re-stenosis are common
• Keratosis obturans is a migration defect, not a wax problem.
• Widening without erosion distinguishes it from canal cholesteatoma, which erodes bone locally
• Ask about cough and sinus symptoms; bronchiectasis and chronic sinusitis are recognised associations