Otoscopy :: THE EXTERNAL CANAL :: Fig7_7
 THE EXTERNAL CANAL  
Keratosis Obturans

Keratosis Obturans

Description : Definition
Blockage of the deep meatus by a hard plug of white keratin debris.

Etiology
The normal self cleansing mechanism of the external ear canal is the net result of the finely co ordinated processes of keratin maturation and lateral cell migration. In keratosis obturans, these mechanisms are nonfunctional.

While the exact etiology of keratosis obturans remains unclear, it appears that there is an increased rate of desquamation of corneocytes within the deep canal and a failure of the normal outward migration of these epithelial cells from the surface of the tympanic membrane laterally along the surface of the skin lining the external canal.

This plug of accumulated keratin remains stuck within the deep canal, exerting pressure on the walls and gradually stimulating resorption of the bony walls of the surrounding canal, which is clinically seen as widening.

Increased hyperaemia of the external canal also seems to play a significant role.

Symptoms
A conductive hearing loss is the most common symptom. Severe pain may result from laceration of the canal skin during an attempt at cleansing with the development of an otitis externa or a keratin foreign body granuloma.

In some cases keratosis obturans is associated with bronchiectasis and chronic sinusitis.

Otoscopic appearances
The bony meatus is occluded by a plug of compressed pearly white keratin debris. On palpation this plug is found to be very hard.

After removal of this plug of compressed keratin squames, hyperaemia of the underlying canal skin and superficial granulations arising from the underlying inflamed skin are frequently seen.

In any event, great care must be taken in removing the plug because the erosion may uncap the facial nerve in its vertical portion and also expose the jugular bulb.

Treatment guidelines
The aim of treatment is firstly to remove the keratin plug safely and completely, and secondly to prevent any recurrence.

The hardness of the keratin plug and its adherence to the underlying skin may make the removal of the plug technically difficult, requiring the use of the operating microscope, and in some cases a general anesthetic may be necessary.

Any inflammation of the ear canal skin or secondary otitis externa should be treated with a suitable topical antibiotic ear drop.

As this idiopathic condition has a tendency to recur, these patients should be seen in follow up on a regular basis, so that any accumulation of keratin can be readily removed before the lumen of the canal becomes totally obstructed.

A large plug of keratin debris is occluding the external meatus and is adherent to the skin of the canal.

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