Otitis externa: A clinical overview.

Diseases of the external ear can be classified as nonspecific and specific inflammations. Among the latter are bacterial and viral diffuse otitis externa, furunculosis, herpes zoster oticus, bullous myringitis, fungal and yeast infections, and even malignant otitis externa. The differential diagnosis of specific inflammations includes tuberculosis, syphilis, frostbite, and burns.

Nonspecific inflammation

The acute exudative inflammatory phase of a nonspecific inflammation is marked by swelling and the presence of fetid debris. It can then develop into a nidus for gramnegative bacteria and anaerobes. Swelling of the retroauricular lymph nodes and even signs of pseudomastoiditis might also occur. True mastoiditis does not occur, but the tissues of the retroauricular region can become very painful.

The acute phase is followed by the chronic inflammatory phase, which is characterized by atrophic epithelium, intense pruritus, and a superinfection accompanied by acute dermatitis. Perichondritis also occurs in some cases.

The pathogenesis of nonspecific inflammation involves a maceration of the meatal skin (as a result of mechanical or chemical damage), allergy, or diabetes. The consequences of these factors include a reduction in skin elasticity, atrophy of the ceruminous and sebaceous glands, the loss of protective films and secretions, and a chemical imbalance (i.e., a pH level >6). In my opinion, the dryness and the atrophy of the ceruminous and sebaceous glands are the key issues with regard to chronic or recurrent otitis externa.

Nonspecific inflammations are localized in the auricle, external auditory meatus, and regional lymph nodes. Myringitis is not common, and the middle ear and mastoid are not affected. The onset of pain on pressure to the tragus strongly suggests otitis externa. The differential diagnosis includes otitis media, mastoiditis, and the acute forms of chronic middle ear inflammation.

The investigation of a nonspecific inflammation should involve otoscopy, bacteriology and mycology, irrigation and cleaning, audiography and tuning-fork tests, and sometimes Schuller's-view radiography to exclude mastoiditis.

The high pH level in patients with nonspecific inflammation can lead to the growth of bacteria and fungi. The most common bacteria are Staphylococcus aureus and Pseudomonas aeruginosa; Escherichia coli and streptococci are seen occasionally. The most common fungi are Aspergillus spp. and occasionally Candida albicans.

Our first treatment step is cleaning under vision, irrigation, and drying the ear. Since 2000, we have used topical ciprofloxacin/ hydrocortisone, and I'm very happy with it. We no longer use aminoglycosides. One alternate treatment is 70% alcohol on a fine gauze wick, which reduces swelling by absorbing the moisture. But alcohol can be ototoxic, so we do not use it if we cannot see the tympanic membrane.

For fungal infections, I use natamycin drops, and I have no problem with fungal otitis externa. Approximately 4% of my patients have a fungal infection.

Specific inflammation

Otitis externa. Two specific forms of otitis externa are (1) erysipelas in streptococcal infection and (2) swimmer s ear with phlegmonous inflammation and perichondritis. Treatment involves cleaning and topical antibiotics, although systemic antibiotics might be needed, as well.

Furunculosis. In Switzerland and Germany, we apply 70% alcohol on gauze wicks until the furuncle bursts spontaneously. Only seldom do we incise furuncles. In most cases, no systemic antibiotic is needed.

Herpes zoster oticus. Herpes zoster oticus is characterized by multiple herpetic vesicles on the auricle or in the external meatus; occasionally, we see them on the tympanic membrane. We treat it topically with famciclovir cream. If a systemic antibiotic is needed, we use either acyclovir, valacyclovir, or famciclovir. I prefer the latter.

Bullous myringitis. Bullous myringitis is usually accompanied by influenza and occasionally by otitis media. In these patients, the physician should obtain an audiogram to look for inner hearing loss. Treatment includes simple toilet of the external meatus and antibiotics for secondary infections. Bullous myringitis is particularly painful, so analgesia is also important.

Malignant otitis externa. This most severe form of specific inflammation is associated with diabetes. The serious complications of this disease are osteomyelitis of the temporal bone, sinus thrombosis, and septicemia; some cases are fatal. Treatment includes diabetes control, systemic antibiotics against anaerobes (usually P aeruginosa), and surgical management (debridement, drainage of the retromandibular space, and ligation or resection of the internal jugular vein). Otolaryngologists in Switzerland measure serum glucose levels and even treat diabetes, and I do both.

Otomycosis. Otomycosis is marked by a fine, easily removable coating and loose, fluffy, whitish-yellow to greenish-black flakes. Its primary symptom is pruritus; it is seldom painful. The diagnosis is based on culture results. Otomycosis can be treated with a topical antimycotic agent delivered via an atomizer; systemic agents are seldom necessary. Approximately 2 to 4% of treatment failures can be attributed to fungal infections.

Eczema. The acute stage of eczema of the ear is marked by a deep-red inflammatory swelling and the presence of moist vesicles and pustules. Later on, we see the formation of crusts, rhagades, and fetid debris. The chronic phase is characterized by irritation and dry, scaly, lichenified skin. Occasionally, stenosis of the outer ear canal, myringitis, or granulations will be present. Patch testing will help exclude contact dermatitis, and swabs will help identify bacterial and fungal pouches. The treatment strategy is to find and eliminate the source of the allergen and to administer a short-term topical steroid locally.

Contact dermatitis. At my institution, we studied 62 patients who had either chronic eczema of the ear or otitis externa that recurred more than three times a year. (1) We performed patch testing on these patients to determine if they would exhibit any signs of a contact dermatitis reaction to neomycin, and eight of them (12.9%) did. The most common contact allergen was nickel sulfate, which was seen in nine patients (14.5%); nickel allergy was twice as common in women as in men.

All patients who had a contact allergic reaction to neomycin were also allergic to neomycin-containing eardrops. However, none of the 62 patients had any allergy to topical ciprofloxacin. We found this to be very convincing in determining what we should use. Among the 62 patients, there were only two treatment failures with ciprofloxacin, both as a result of a fungal superinfection. Ciprofloxacin was highly effective, not ototoxic, and not a contact allergen. This is a key finding in otology, and it should be a key issue in allergic rhinitis and sinusitis, as well.

Comments

Dr. Croxson: One of the most difficult problems in managing otitis externa is cleaning the external canal. What can we do to improve the quality of cleaning at the general practitioner level?

Dr. Schapowal: I teach the GPs I work with how to irrigate, how to use the otoscope, and how to use the tuning fork. Our GPs are quite capable of cleaning the external canal. If they should fail, they can refer those patients to me.

Dr. Croxson: Is there a place for ceruminolytics in otitis externa?

Prof. Hawke: I don't think I've ever seen a patient with acute otitis externa who had any cerumen in the ear canal. Some of these patients have inflammatory debris, but not cerumen. One of the best things we can do for GPs is to provide them with the tools they need to clean the ears of both cerumen and other debris. In addition to sharing with them our knowledge and skill, we could provide them with a suitable ear syringe that's inexpensive, practical, and works. You can remove a lot of things from the ear canal simply with a syringe and a bit of water if you're taught how to do it. I don't think GPs would be very interested in dry mopping, aspirating, and things like that, but if we can teach them how to syringe and provide them with the tool--I suspect many GPs don't even have a suitable ear syringe--then we'd probably be taking a giant step forward.

Dr. Croxson: One of the problems might be their anxiety about the medicolegal implications of flushing ears. I'm sure that's the case in the United States, and it's certainly the case in Australia, where a number of cases have come to litigation because it was alleged that flushing caused a perforation and/or hearing loss. Is there a better way of flushing?

Prof. Hawke: It seems that the Otoclear tip is a reasonably better way. The tip directs the stream laterally; it doesn't allow it to go forward. There will always be lawsuits over adverse events. Probably the best defense is to ask the patient whether there is any history of ear disease and to adhere to the accepted standards of practice in your area.

Reference

(1.) Schapowal A. Contact dermatitis to antibiotic ear drops is due to neomycin but not to ciprofloxacin [abstract]. Allergy 2001; 56(Suppl 68):148.

Andreas Schapowal, MD

Dr. Schapowal is a specialist in ear, nose, and throat diseases, allergology, and clinical immunology in Landquart, Switzerland. His primary research interest is allergology. He is also president of the Swiss Academy of Medicine and Ethics and a Lieutenant Colonel in the Swiss Army Medical Corps.