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Update on otitis externa

Professor John Birchall gives an overview of how to treat this common problem and advice to prevent recurrence

Professor John Birchall gives an overview of how to treat this common problem and advice to prevent recurrence

The vast majority of cases of otitis externa will be cured with a single course of topical antibiotic drops. Recurrence will largely be prevented by counselling the patient and explaining what otitis externa is, how it occurs and how they can avoid it.

However, cases that fail to respond to two consecutive treatments with topical antibiotics should be referred to ENT, as should patients with abnormalities of the external auditory meatus or tympanic membrane, and those with conductive hearing loss.If hearing loss is a feature when the patient presents, it is usually mild and tuning fork tests would show air conduction better than bone conduction (Rinne +ve). A completely occluded external auditory meatus or underlying middle ear disease results in bone conduction being better than air conduction (Rinne -ve).

The following regimen is recommended in a patient with no previous otological history and particularly if there has been an obvious cause for the otitis externa such as a recent holiday, swimming in untreated water, in the sea or possibly in poorly treated water in hotel swimming pools.

If the patient has no antibiotic allergies, start with a 10-day course of gentamicin and hydrocortisone drops, two to three drops three times each day. It is important to instruct the patient on how to use these drops.They should lie on their side with the affected ear uppermost, and preferably have the drops applied by another person. Tragal pressure should be applied two or three times to stop a bubble forming at the entrance to the meatus and the patient should stay in a lying position for about five minutes.

Anaerobic bacteria are commonly found, particularly Pseudomonas aeruginosa, so oral antibiotics are not indicated.Review the patient in three weeks' time, and if the infection is settled and the anatomy of the external meatus and tympanic membrane is normal, reassure and advise about avoidance and factors that may precipitate further attacks.

If the infection has not settled, again re-emphasise the importance of using the drops properly and complying with the full course, and try them with a 10-day course of dexamethasone, framycetin and gramicidin drops. Two to three drops are given three times a day, and reviewed three weeks later.If the ear then settles, proceed as above.

If it hasn't, further inquiries need to be made. Again check the compliance and consider the following:

  • Might the patient have lost a cotton bud in their ear while cleaning it?
  • Is there any history of dermatological conditions such as eczema or psoriasis?
  • Is there any evidence of diabetes mellitus or anything else that could immunocompromise the patient?
  • On examination, is there any evidence of granulation tissue, polyps, bare bone, foreign body, perforation or attic retraction?
  • Are there any fungi such as the small, black fruiting heads of Aspergillus niger?

At this point it is worth considering two courses of action: a course of anti-fungal ear drops such as clotrimazole; or referral to ENT.There is a risk of causing sensorineural hearing loss due to otoxicity when using topical aminoglycoside antibiotic ear drops. The British Association of Otorhinolaryngologists and Head and Neck Surgeons recommends that the risk of causing otoxicity is very small even if a perforation to the tympanic membrane is present, providing the treatment does not exceed 10 days.

ENT departments have microscopes and suction devices enabling effective aural toilet, providing the ear isn't too painful. The purpose of the toilet is to prove or exclude underlying pathology such as chronic suppurative otitis media or cholesteatoma ­ it is not used primarily as a form of treatment.

Aspirating exudate from the ear canal is only of short-term benefit as it re-forms within minutes or hours. Pure-tone audiometry is a more sensitive method of picking up a conductive hearing loss and raising the suspicion of middle ear pathology. If a foreign body is present, usually cotton wool, this can be easily removed.

More intensive ear treatment can be provided in an ENT department if the meatus is grossly narrowed because of skin inflammation and oedema. A Pope ear wick can be inserted, which expands on the application of antibiotic drops. Dressings can be applied to the ear and changed every few days. If nothing else, this does ensure there is true patient compliance and, furthermore, they cannot be doing additional damage to the ears by poking.

John Birchall is professor of otolarygology and head and neck surgery, Queen's Medical Centre NHS Trust, University of Nottingham

Preventing further attacks

Following resolution it is vital to explain to patients that if further attacks are to be prevented, they have a role to play. They should understand that repeated treatment with topical antibiotic drops is not the best solution, and that prevention is the key.·

If they are prone to wax build-up, they should be told that use of olive oil once or twice a week can prevent the problem. If attacks are triggered by water in the ear (bathing, swimming or showering), they should take precautions. When bathing and showering, for example, cotton wool with Vaseline placed in the conchal bowl should prevent water and irritants entering.

Patients should be counselled not to put anything in the ears that can damage the skin and predispose to infection, eg cotton wool buds, hair grips and ear plugs· Some patients have been advised not to swim; however, this would be reasonable only if they had had repeated attacks.

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