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Otitis externa (OE) more commonly called ‘swimmer's ear' is an extremely common, painful infection of the external ear canal which may also involve the pinna or tympanic membrane. In the Middle East, it is the among the most common ear infections that present in the emergency department. The typical clinical manifestation of otitis externa is pain, followed by erythema, edema, itching, discharge and hearing loss.
The most common precipitating factor of otitis externa is excessive moisture, permitting bacteria and fungi that normally inhabit the skin and ear canal to multiply and infect the ear canal. While OE can occur in anyone, the risk is greater if the skin integrity is breached, for example by minor trauma from cotton swabs or by cracks and fissures arising from a chronic dermatitis such as eczema or psoriasis.
The skin integrity is also weakened if the skin is chronically wet, which is how the infection earned its nickname.
Diagnosing external otitis
External otitis is simple to diagnose, with otalgia (ear discomfort) and otorrhea (discharge in or coming from the external auditory canal) forming the two characteristic presenting symptoms.
If inflammation causes sufficient swelling to occlude the external auditory canal, patients may also complain of muffled hearing on the affected side. Pulling or moving the external ear produces severe pain. Inspection of the ear canal with an otoscope shows the lining to be red, swollen, and covered with pus or fungal debris.
The condition is rarely missed, but it may be over-diagnosed by physicians who do not perform a competent ear examination. Alternative causes of ear pain such as temporomandibular joint dysfunction (or TMJ syndrome) can be mistaken for recurrent external otitis.
Primary dermatologic disorders are frequently a precipitous factor in infectious otitis externa, but they may also be the sole cause of otitis externa. Atopic dermatitis, psoriasis, seborrheic dermatitis, acne and lupus erythematosus may all cause OE. As a result, a thorough dermatologic examination and history should always be part of the evaluation of patients with OE.
Generally it is easy to distinguish bacterial from fungal external otitis. Fungal infection is associated with a distinctive ‘furry' discharge in the external auditory canal, while bacterial infections are associated with cream colored or greenish pus.
The most common bacterium causing external otitis is Pseudomonas aeruginosa and the most common fungus is Aspergillus niger. Fungal infections are often more difficult to cure than are bacterial infections.
Drops may be needed for longer and the ear will need to be cleaned on a weekly basis to remove fungal debris that impairs access of drops to the skin surface.
Some patients may need four weeks of oral antifungal medication (e.g. fluconazole or itraconazole) as well.
Treating external otitis
Standard treatment of OE consists of the following components:
• Cleaning of all infected material from the ear canal by use of a suction cannula and otomicroscope. If the secretions are thick, crusted or adherent, instillation of antibiotic drops or hydrogen peroxide may aid in softening them for removal.
• Applying antibiotic or antifungal ear drops for 10 days. If the ear canal is so swollen that it will not admit drops, a wick should be inserted for the first 48 hours to draw the drops down into the canal beyond the swelling.
Patients should also be advised to maintain strict water precautions for four weeks. Water precautions consist of the use of a cotton ball coated with petroleum jelly in the external ear when showering or bathing in order to exclude moisture from the ear canal.
All patients with recurrent external otitis or with a history of diabetes or other chronic illness should be closely monitored for evidence of malignant otitis externa. This rapidly spreading infection of the soft tissue and bone spreads from the ear canal inward to involve the skull base, resists simple treatment and is often associated with exposed necrotic cartilage in the floor of the ear canal and cranial neuropathies. This condition produces progressive loss of cranial nerve function and can be fatal. It requires aggressive treatment with a prolonged course of intravenous antibiotics for 8-12 weeks.
Complications
The only complication of external otitis is reach of the infection beyond the ear canal. It can spread out to the external ear and involve the skin (auricular cellulitis) and/or cartilage (chondritis/perichondritis), or it can spread on to the face (facial cellulitis).
The most serious complication of external otitis, malignant external otitis, is seen in patients with a weakened immune system, such as diabetics or the elderly. Any case of external otitis that is frequently recurrent, that fails to respond to standard therapy (pain free within 72 hours of initiating ear drops), or that develops spreading cellulitis of the external ear, face, or skull base must be referred to an otolaryngologist.
Preventing recurrence
Prevention of recurrence of otitis externa primarily consists of avoiding the causative factors of OE and treating any underlying dermatologic disorders. Patients should be advised to:
• Avoid mechanical irritation to the ear canal.
• Allow the ears to ‘ventilate' - for example, hearing aid users should take off their aids for 15-20 minutes 3 times daily to let the ear canal dry out.
• Dry the external auditory canal thoroughly after swimming or bathing. A hair dryer used on the lowest heat setting is an effective method.
Patients with a demonstrated tendency to recurrent external otitis can prevent this with use of an ear rinse. A 50:50 solution of 70% isopropyl alcohol and white vinegar is extremely effective. Patients soak a cotton ball with this solution and wring it out to fill the ear canal. The solution is poured in and then poured out again and the canal is allowed to dry (a hairdryer can again be used here). This rinse is conducted at least twice daily and after any water exposure or heavy perspiration. However, that method should only be advised if the tympanic membrane is intact. It should not be used in an ear with a perforation.
National guidelines
Last year, in response to the high incidence of OE and the diversity of treatment interventions, the American Academy of Otolaryngology issued clinical practice guidelines for acute otitis externa. As the first evidence-based recommendations, the guidelines give clinicians up-to-date recommendations for the resolution of OE , while minimising recurrence, cost, complications and adverse events. Specific recommendations are as follows:
• Assess pain and recommend analgesic treatment based on pain severity. Ear pain from AOE is often severe and can interfere with work or leisure activities. With appropriate treatment, pain from AOE usually improves after one day and resolves in four to seven days.
• Distinguish diffuse AOE from other causes of otalgia, otorrhea, and inflammation of the external ear canal
• Evaluate the patient with diffuse AOE for factors that modify management, such as nonintact tympanic membrane, tympanostomy tube, diabetes, immunocompromised state, and/or prior radiotherapy.
• Use topical preparations for initial therapy of diffuse, uncomplicated AOE. Antiseptic and antibiotic eardrops are the preferred therapy for most AOE, because they are safe, give prompt relief, and do not promote bacterial resistance.
• Avoid systemic antimicrobial therapy unless there is extension of cellulitis outside of the ear canal or there are specific host factors suggesting a need for systemic therapy, such as diabetes, immune deficiency, or inability to deliver topical therapy despite cleaning of the ear canal, inserting a wick, or both. Despite the widespread use of oral antibiotics for AOE, they are not recommended for uncomplicated cases because they have more adverse effects and may be less effective than eardrops.
• Choose topical antimicrobial therapy of diffuse AOE based on efficacy, low incidence of adverse events, likelihood of adherence to therapy, and cost.
• Inform patients how to administer topical drops.
• When the ear canal is obstructed, enhance delivery of topical preparations by aural toilet, placing a wick, or both.
• Prescribe a nonototoxic topical preparation when the patient has a tympanostomy tube or known perforation of the tympanic membrane. The newer, quinolone antibiotic eardrops are approved for this purpose and do not cause hearing loss.
• If the patient fails to respond to the initial therapeutic option within 48 to 72 hours, reassess the patient to confirm the diagnosis of diffuse AOE and to rule out other causes of illness.
• Ear candles are not recommended for treating AOE because efficacy has not been demonstrated, and adverse effects may include burns and perforated eardrum.
To access the full American Academy of Otolaryngology guidelines, visit www.guideline.gov/summary/summary.aspx?doc_id=9310 .
