External auditory canal cholesteatoma: Description, Causes and Risk Factors:
External auditory canal cholesteatoma is an uncommon otologic entity. The predominant findings are erosion of the bony structure of the external auditory canal and accumulation of keratin debris.
External auditory canal cholesteatoma is uncommon and is estimated to occur in about 0.1% of otologic patients. Researchers first described external auditory canal cholesteatomas as "specimens of molluscum contagiosum developed in the external auditory canal" in 1850. External auditory canal cholesteatoma presented as localized "diverticulum" eroding into adjacent mesenchymal tissue and the bony auditory canal. They occur predominantly in the inferior part of the external auditory canal.
External auditory canal cholesteatoma is associated with a focal area of osteitis and bone sequestration surrounded by inflammation of the skin of the external auditory canal. The uninvolved epithelium of the ear canal is usually normal. Researchers also demonstrated that irregularities in the bony external ear canal and local inflammation stop the migration of skin from the canal. This leads to a build-up of keratin debris and cholesteatoma.
Researchers classified external auditory canal cholesteatoma into four stages on the basis of histopathology and clinical symptoms:
Stage I, hyperplasia of the canal epithelium.
- Stage II, periostitis.
- Stage III, defective bony canal.
- Stage IV, erosion of the adjacent anatomic structure.
External auditory canal cholesteatomas arise through several different mechanisms. Occlusion or narrowing of the external meatus results in retention of squamous epithelial debris in the medial portion of the external auditory canal. Implantation of squamous epithelium results in cyst formation deep to the skin of the external auditory canal. Finally, erosion of the bone of the external canal allows ingrowth of squamous epithelium into the defect. The potential for development of external auditory canal cholesteatoma in congenital and acquired aural stenosis is well recognized. External auditory canal cholesteatoma are described as late complications of temporal bone trauma, tympanomastoid operation, and radiation therapy. Chronic inflammatory disorders may also stimulate the development of external auditory canal cholesteatoma. Development of an external auditory canal cholesteatoma after irradiation was reported by researchers. Perhaps recurrent trauma combined with a vascular ischemia predisposes patients to periostitis and bone sequestration, which are associated with cholesteatoma of the external ear canal.
Thirteen cases of external auditory canal cholesteatoma were retrospectively reviewed. Clinical data were reviewed for the history, presentation, and physical examination findings. High-resolution temporal bone CT scans were examined for a soft-tissue mass in the external auditory canal cholesteatoma, erosion of adjacent bone, and bone fragments in the mass. The middle ear cavity, mastoid, facial nerve canal, and tegmen tympani were evaluated for involvement.
- The authors present a series of 12 ears in 10 patients ranging from 18 to 72 years old with external auditory canal cholesteatomas seen over an 8 year period. Males and females were equally involved. The left ear was involved 3 times as frequently as the right. No association with sinus or bronchial diseases was seen. Two cases were examined, 3 1/2 and 7 years before the development of any external auditory canal symptoms, and were normal. Two cases of bilateral involvement by external auditory canal cholesteatomas were reported. The clinical findings of external auditory canal cholesteatomas in this series are discussed. The authors describe a method of surgical treatment used in 12 ears with an average 3 year follow-up and excellent results. The technique involves the excision of the involved skin and periosteum followed by bone debridement. Fascia was used when 1. a large amount of skin had been removed, 2. mastoid air cells were exposed, 3. a soft tissue graft was used to fill a bony defect, or 4. when a portion of the tympanic membrane was sacrificed or its continuity interrupted.
The most common presenting symptoms reported in the literature are otalgia and otorrhea
has been described as a more vague or mild discomfort, but also as a chronic dull pain, and in some cases severe pain; thus, the symptom is not described consistently. The incidence of major symptoms has been extracted from selected studies only data from primary cases are included, since they contain the more substantial number of cases.
Diagnosis of external auditory canal cholesteatomais based on history and physicalexamination. Radiographic assessment is useful for defining the extent of the lesion and delineating its proximity tothe middle ear and to neurovascular structures. A findingcommon to all cases of external auditory canal cholesteatoma is retained squamous epithelium debris within the external auditory canal and localized bone destruction. The middle ear is normal unlessthere is secondary invasion by the external auditory canal cholesteatoma.CT imagingshows cortical bone erosion with abnormal soft tissue,which may be indistinguishable from malignancy.
On otoscopic examination, it can be difficult todistinguish external auditory canal cholesteatoma fromother inflammatory, infectious, or neoplasticprocesses. Examples of these include keratosisobturans, malignant otitis externa, and squamous cellcarcinoma [SCC]. The most closely related non-neoplasticcondition may be keratosis obturans. Keratosisobturans generally occurs in a younger age group. It isoften bilateral, and it has a definite relationship tobronchiectasis and sinusitis. CT imaging ofkeratosis obturans typically demonstrates a soft-tissueplug in bilateral external auditory canals, without focalbone erosion, which may be different from externalauditory canal cholesteatoma.
The management of external auditory canal cholesteatoma depends on the site and the extent of bone destruction. He recommended the following approaches for surgical removal of external auditory canal cholesteatomas: for stage I, a transcanal approach; for stages II and III, an endaural approach with local anesthesia; and for stage IV, a postauricular incision followed by a canal wall down technique. Small sequestrations in the ear canal may be removed by curettage under local anesthesia. However, larger and more invasive external auditory canal cholesteatomas should be managed by surgical debridement through a postauricular approach. The auditory canal may be lined with fascia to give a soft tissue base for re-epithelialization or may be allowed to heal by secondary means.
After the removal of the external auditory canal cholesteatoma, the auditory canal generally requires longer to heal than after a tympanoplasty; however, most cases heal within 10 weeks. After healing, the ear canal requires periodic cleaning to prevent re-accumulation of the keratin debris within the bony depressions. Skin grafting is beneficial for large canal skin defects. Canal wall down mastoidectomy is used for large posterior wall defects and instances of Eustachian tube dysfunction or middle ear disease. Intact canal wall mastoidectomy is used when middle ear function is normal. Cortical bone is used to reconstruct the external canal.
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