Keratosis Obturans

Keratosis obturans is an accumulation of a plug of desquamated keratin in the external auditory canal. It forms a hard, cholesteatoma like mass that expands the bony canal, due to abnormal epithelial migration and excessive production of keratin.

It is rare (about 4 to 5 per 1,000 otology patients). It occurs in young individuals (age 5 to 40 years, mean 20 to 30) and is often bilateral (about 50 percent). It is associated with chronic sinusitis and bronchiectasis (the "sinobronchial syndrome", in 40 percent) and with abnormal ciliary function.

It is characterised by a plug of keratin debris in the deep canal, with inflammation of the underlying skin, painful onset and expansion (widening) of the bony canal. This contrasts with external ear canal cholesteatoma, a localised bony erosion from keratin debris in a localised area.

The proposed mechanism is a defect in the epithelial migration of the canal skin, with an increased turnover of keratin, together with chronic inflammation. An inflammatory cause is suggested by chronic otitis externa and the increased vascularity.

Complications:

• canal widening (bony erosion of the canal walls, with the canal enlarged symmetrically)
• conductive hearing loss
• severe pain
• secondary infection
• osteitis
• rarely, bony erosion of the facial canal or mastoid and facial paralysis
• tympanic membrane thickening or perforation

• Acute severe otalgia (the hallmark, with a sudden onset, due to pressure on the periosteum of the canal), which is often worse at night, with a feeling of ear fullness.
• Conductive hearing loss (from plug), tinnitus, and otorrhoea in some (secondary infection).
• Occasionally bilateral, and associated with chronic rhinosinusitis, bronchiectasis and recurrent respiratory infection, with a history of repeated ear plugging.
• Otoscopy: a plug of white or yellow white keratin, laminated and hard, filling the canal medially, close to the drum and adherent to the canal wall, with inflamed, granulating and swollen canal skin, with a widened canal after the plug is removed; the tympanic membrane may be thickened, congested or have a retracted drum.
• Unlike cholesteatoma of the external canal, there is no focal bony erosion and the skin is diffusely inflamed.

• Otoscopic examination after the removal of the plug (under microscope), showing a widened canal with a raw, erythematous skin, with a thick and congested tympanic membrane (a layer of keratin).
• Audiometry: conductive hearing loss, normal after the plug is cleared; tympanometry.
• CT of the temporal bone (when the diagnosis is uncertain, or in recurrent cases): a widened bony ear canal, with soft tissue plug and without focal bony erosion, a normal middle ear and mastoid; to differentiate from canal cholesteatoma (focal bony erosion with sequestrum), osteoma, exostoses and carcinoma.
• Swab for culture when infected; assess for associated sinusitis and bronchiectasis (sinus CT, chest imaging, spirometry, and ciliary function testing).
• Biopsy if the appearance is atypical, or in an adult (to exclude squamous cell carcinoma).

• Removal of the keratin plug under the operating microscope is the principal treatment. Use local anaesthesia (or general anaesthesia in children or when the plug is adherent and painful).
• Soften the plug first with ceruminolytic drops (olive oil, sodium bicarbonate 5 percent or hydrogen peroxide drops, for 3 to 5 days) or by soaking. Then remove it with gentle suction, alligator forceps and curettage.
• The canal wall skin is often raw and bleeds after removal, and must be treated gently. Syringing is avoided because of pain and the risk of trauma.
• Post-removal care: topical antibiotic steroid drops (ciprofloxacin 0.3 percent with dexamethasone 0.1 percent, 3 to 4 drops twice daily for 7 to 14 days) for the inflamed skin, and analgesia (paracetamol 1 g every 6 hours, ibuprofen 400 mg every 8 hours); acetic acid 2 percent drops or boric acid powder may help.
• Prevention of recurrence (recurrence is common, up to 50 percent): regular aural toilet by microsuction every 3 to 6 months (under the microscope) for years. Use ceruminolytic or keratolytic drops (such as 2 percent salicylic acid in 70 percent alcohol, or dilute hydrogen peroxide 3 percent) and 2 percent acetic acid drops (to maintain the canal acidity). Avoid trauma and cotton buds.
• Treat the underlying chronic sinopulmonary disease: nasal saline irrigation, intranasal corticosteroid (mometasone 2 sprays each nostril daily), antibiotics for sinusitis (amoxicillin clavulanate 625 mg three times daily for 10 to 14 days), management of bronchiectasis with chest physiotherapy, and referral to a pulmonologist.
• Surgery for refractory, recurrent disease with severe canal skin disease: canalplasty with skin grafting (meatoplasty with split thickness skin graft, after removing the diseased skin), or canal wall reconstruction, often in refractory cases, and a mastoidectomy if the middle ear or mastoid is involved; success rates are high but recurrence can occur.
• Follow up: every 3 months initially, then 6 to 12 months once stable; counsel to seek review with severe ear pain, hearing loss or discharge.
• Prognosis: good with regular follow up, though it is a chronic condition with periodic recurrences; hearing returns to normal in most.