![]() ![]() ![]() ![]() The features which made keratosis obturans less likely was the chronic history and the irregular bony erosions instead of the smooth scalloping seen in keratosis. Keratosis obturans is the pathological condition characterised by accumulation of desquamated keratin in the external auditory meatus. The imaging differentials include keratosis obturans and mycetoma. The features of facial palsy alerted the ENT surgeon to a pathology not confined to the external auditory canal but extending to the middle ear. Our patient had a previous history of trauma which could be the inciting event for the secondary cholesteatoma formation. Īn external auditory canal cholesteatoma can be mimicked by many conditions like keratosis obturans, carcinoma etc, computed tomographic imaging of the temporal bone is useful in arriving at the correct diagnosis, to determine the extent of the lesion and the bony involvement. In case of involvement of the mastoid air cells as in our case, the appropriate procedure should be canaloplasty with mastoidectomy. The management of the external auditory canal cholesteatoma depends on the extent of the lesion. The case under discussion is in stage III. There is extension beyond the temporal bone in stage IV. In stage III there is involvement of mastoid air cells. There is involvement of tympanic membrane and middle ear in stage II. In stage I, the disease limited to the external auditory canal. However, a homogenously hyperdense appearance is not described which is peculiar to our case.Īccording to the clinical and computed tomography staging by Seung-Ho Shin et al there are four groups of external auditory canal cholesteatoma. Ĭholesteatoma of the external auditory canal appears as a soft tissue attenuating lesion with bone erosion and with intramural bone fragments. Usual symptoms include otalgia, otorrhea and hearing loss. Most of the cases are spontaneous but can occur secondary to trauma or surgery. External auditory canal cholesteatomas are rare occurring in about 1-5 of every 1000 otologic cases. The broad auricular cartilage has numerous holes (see Figure 1-1), which are traversed by branches arising from the caudal auricular artery.Cholesteatomas occur due to the ingrowth of the stratified squamous epithelium of the external auditory canal into the middle ear. It is the largest cartilage of the external ear. The shape and size of the external ear vary greatly among different breeds of dogs, mainly owing to the auricular cartilage that forms the skeleton of the pinna. The skin covering the auricular cartilage may show breed-specific pigmentation. The skin on the concave surface of the pinna is very tightly connected to the underlying auricular cartilage, accentuating all the auricular prominences (see Figure 1-3). The caudal margin of the pinna exhibits a cutaneous pouch called the marginal pouch (Figure 1-3). The leaf-shaped pinna of the external ear is broad with medial (rostral) and lateral (caudal) margins. The ear is moved by three sets of muscles (rostral, ventral, and caudal) that are innervated by branches of the facial nerve (cranial nerve VII). It is designed to localize and collect sound waves and transmit them to the tympanic membrane (eardrum). Carriage of the pinna is breed-specific in the dog but mostly upright in the cat. The pinna, or auricle, is a highly visible structure. ![]()
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