External auditory canal cholesteatoma
External auditory canal cholesteatomas are an uncommon locations for cholesteatomas, which are usually in the middle ear or petrous apex. When they occur lateral to the tympanic membrane, they are referred to as external auditory canal cholesteatomas.
The external acoustic canal is a rare location for a cholesteatoma with an estimated incidence around 1.2 per 1,000 new otological patients. The overall incidence rate in one large study was 0.30 per year per 100,000 inhabitants 1. For comparison, the annual incidence of middle ear cholesteatoma is around 9.2 per 100,000.
A distinction from keratosis obliterans has been introduced only in the last few decades. Both mainly consist of epithelial debris in the external acoustic canal. The most useful findings confirming an external auditory canal cholesteatoma are focal osteonecrosis with or without sequestration and lack of epithelial covering of the bony surface 2. The distinction between keratosis obliterans and cholesteatomas is not merely one of pedantry, but impacts on treatment strategy 3.
External auditory canal cholesteatoma can be divided into:
- no antecedent cause identified
- more common
- postoperative, postinflammatory, posttraumatic, radiation-induced
A special type of secondary cholesteatoma of the external auditory canal which is worth mentioning separately are those associated with congenital atresia of the external auditory canal.
High-resolution bone window CT is the method of choice to localise the lesion and to demonstrate bony erosions. They appear as soft tissue attenuating lesions.
Cannot show early involvement of compact bone. Its role in EACC is unknown.
Treatment and prognosis
Small lesions can be treated endoscopically under local anaesthesia, whereas larger lesions need surgery to remove the cholesteatoma and affected bone areas. Grafting of defects may be necessary. Prognosis depends on the extent at the time of diagnosis.
History and etymology
External auditory canal cholesteatomas were first reported by Toynbee in 1850.
General imaging differential considerations include
- 1. Owen HH, Rosborg J, Gaihede M. Cholesteatoma of the external ear canal: etiological factors, symptoms and clinical findings in a series of 48 cases. BMC Ear Nose Throat Disord. 2006;6 : 16. doi:10.1186/1472-6815-6-16 - Free text at pubmed - Pubmed citation
- 2. Heilbrun ME, Salzman KL, Glastonbury CM et-al. External auditory canal cholesteatoma: clinical and imaging spectrum. AJNR Am J Neuroradiol. 2003;24 (4): 751-6. AJNR Am J Neuroradiol (full text) - Pubmed citation
- 3. Persaud RA, Hajioff D, Thevasagayam MS et-al. Keratosis obturans and external ear canal cholesteatoma: how and why we should distinguish between these conditions. Clin Otolaryngol Allied Sci. 2004;29 (6): 577-81. doi:10.1111/j.1365-2273.2004.00898.x - Pubmed citation