Keratosis obturans is a rare external auditory canal (EAC) disease characterized by abnormal accumulation and consequently occlusion and expansion of the bony portion of the EAC by a plug of desquamated keratin. It can be confused for EAC cholesteatoma but they are completely different entities requiring different treatment.
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Epidemiology
Keratosis obturans is seen in younger patients usually less than 40 years old and is bilateral in 50% of cases.
Clinical presentation
Patients present with acute severe pain and conductive hearing loss.
Pathology
The cause is not clear in the majority of cases.
Keratosis obturans is characterized by:
- dense plug of keratin debris within the deep meatus
- hyperplasia of the underlying epithelium
- chronic inflammation within the subepithelial tissue
- remodeling and expansion of the canal
- no evidence of erosion or necrosis of the underlying bone
Associations
- bronchiectasis
- chronic paranasal sinus disease
NB particularly in the pediatric group which these concurrent findings approach 80%; but only in 20% of adult patients.
Radiographic features
CT
- well-defined soft tissue mass within the bony EAC which may diffusely enlarge the canal with no bony erosion, as opposed to EAC cholesteatoma
- tympanic canal is usually spared but may be slightly thickened
Treatment and prognosis
Usually treated by EAC toilet; due to a high incidence of recurrence, it may require several excisions of keratin plugs. It rarely needs surgical intervention.
Differential diagnosis
- external auditory canal debris, which partially fills the EAC and usually shows air foci
- external auditory canal cholesteatoma: EAC soft tissue density with bony erosion
- external auditory canal carcinoma: irregular mass with or without bony erosion
- otitis externa: surrounding inflammatory fat stranding