Otoscopy :: THE EXTERNAL CANAL :: Fig7_29
 THE EXTERNAL CANAL  
Chronic Otitis Externa

Chronic Otitis Externa

Description : Definition
A prolonged or recurrent diffuse inflammatory condition of the skin of the external auditory canal.

Etiology
Acute diffuse otitis externa can become chronic if incompletely treated or if the initial predisposing factors (e.g. local trauma, moisture, etc.) remain.

Many cases of chronic otitis externa are self-inflicted due to repeated contamination of the ear with water or by self manipulation.

Chronic diffuse otitis externa can also occur secondarily to active chronic otitis media.

The presence of pus in the ear canal arising from infected middle ear mucosa does not normally by itself induce infection of the canal skin, and it is probable that skin involvement develops only after scratching or inept aural toilet.

Symptoms
The symptoms of chronic otitis externa consist primarily of itching, fullness, hearing loss and otorrhoea, whilst severe pain is not generally a prominent feature.

Normal desquamation and ventilation of the ear canal are impaired and since the ear tends to itch and feel blocked, a vicious cycle of itching and scratching is established.

Otoscopic appearances
The otoscopic appearances in chronic otitis externa can be quite variable. The skin of the meatus is often thickened, with partial or complete stenosis sometimes occurring. Foul smelling debris is usually found within the meatus, although in some patients the only signs of chronic otitis externa may be a slight redness of the epithelium and a complete absence of any wax or debris.

Further investigations
The first step is to send a swab for bacterial and fungal studies to identify the causative organisms and to assist in the selection of an appropriate topical antibiotic or antimycotic agent.

The possibility of an underlying dermatological disorder, systemic disease, or evena malignancy should always be considered in unresponsive cases.

Treatment guidelines
The aim of treatment is to restore the skin of the meatus to its normal state. In practice this can be extremely difficult; despite energetic prolonged therapy, many of these patients are only free of disease for short periods of time.

The mainstay of treatment is thorough aural toilet and a modification of any factors in the patient's behavior which have contributed to the development of the disease, e.g. scratching and exposure of the ear to moisture.

Thorough aural toilet can be accomplished either by dry mopping with cotton wool or by suction under microscopic control.

It is crucial to remove every vestige of debris from the ear canal if topical therapy is to be successful.

In those cases in which the lumen is moderately narrow, a selvedged half inch (1 cm)ribbon gauze wick saturated with Burrows solution is then introduced into the canal.

If the canal is almost obliterated and will not admit a wick, triamcinolone otic ointment can usually be
inserted into the ear canal from a syringe fitted with a soft fine polyethylene tip.

Repeated thorough toilet with the reapplication of topical therapy modified in the light of results obtained from culture studies is generally rewarded byimprovement.

Here again, the examiner should be on the look out for allergic reactions to the medications used, or the presence of a more serious underlying disease.

The skin of the external bony canal is thickened and the lumen is blocked with a yellowish brown plug of infected cerumen.

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