Infectious Diseases

Otitis Externa

OVERVIEW: What every practitioner needs to know

  • The external ear canal is a cul-de-sac lined by a thin layer of skin and may be the site of inflammation and infection. Infections include pustules, furuncles, and cellulitis. Inflammation of the canal may result in edema and occlusion of the canal accompanied by severe pain.

  • Swimmer's ear is due to maceration of the skin of the canal in a warm and moist environment that results in edema and inflammation and may become secondarily infected.

  • Pus exuding from the middle ear during the course of acute otitis media may result in irritation of the external canal.

  • Malignant external otitis is a severe, necrotizing infection of the skin of the canal that may occur in diabetic, immunocompromised, and debilitated patients. The infection spreads from the skin of the ear canal to adjacent tissues including blood vessels, cartilage, and bone.

  • Children may place foreign bodies in the ear canal and adults may use hair pins or cotton swabs which may result in inflammation and possible occlusion of the canal.

  • Whatever the cause, external otitis may result in severe pain that requires assessment of the etiology and management with cleansing the canal of debris and consideration of otic antimicrobial agents.

Are you sure your patient has otitis externa? What should you expect to find?

  • Because the external ear canal is long (approximately 2.5cm) and narrow any swelling may lead to obstruction of the canal. Signs may vary from itching to severe pain.

  • If the canal is patent the observer may see the site of inflammation including desquamation of skin, pustules, or furuncles. If the canal is occluded by the inflammation the examiner may not be able to identify the location of the lesion. Pus may be evident in the canal.

How did the patient develop disease otitis externa? What was the primary source from which the infection spread?

  • The external auditory meatus is a skin-lined cul-de-sac and infection of the canal is similar to that of skin and soft tissue infection elsewhere in the body. The canal is narrow and tortuous and fluid and foreign objects may become trapped and cause irriation of the skin resulting in some cases in obstruction of the canal. The primary sources may include pustules or furuncles associated with hair follicles; maceration of the skin by a moist, warm environment (swimmer's ear); a foreign body; or pus exuding through the a perforation of the tympanic membrane in a patient with acute otitis media.

Which individuals are of greater risk of developing otitis externa?

  • Swimmers are subject to maceration of the skin of the canal.

  • Children and adults who are prone to place objects in the ear canal are at risk of the object becoming fixed in the canal.

  • Diabetics, debilitated, and immunocompromised patients are subject to the severe, necrotizing infection of malignant external otitis.

Beware: there are other diseases that can mimic otitis externa:

  • The itching and severe pain associated with external otitis and the examination of the ear canal restrict the differential diagnosis to the various diseases noted above as causes of external otitis. Early manifestations of herpes zoster oticus (Ramsey Hunt syndrome) may also be associated with itching and ear pain in or around the ear canal. Subsequent development of vesicles establishes the diagnosis of herpes zoster.

What laboratory studies should you order and what should you expect to find?

Results consistent with the diagnosis

  • White blood cell counts and other nonspecific tests of inflammatory reaction are of minimal, if any, value in diagnosis of external otitis.

Results that confirm the diagnosis

  • Blood cultures should be considered in patients with the necrotizing infection of malignant external otitis. The various other causes of external otitis are local and not systemic diseases and are not associated with bacteremia.

  • Pus may exude from the canal and provide specific information about the bacterial pathogen.

What imaging studies will be helpful in making or excluding the diagnosis of otitis externa?

  • Imaging studies may be important to consider in patients with malignant otitis externa because of possible spread to intracranial structures.

What consult service or services would be helpful for making the diagnosis and assisting with treatment?

  • If the patient has spread of the infection to adjacent tissues, as occurs in malignant external otitis media, the health care worker may need to consult an otolaryngologist.

If you decide the patient has otitis externa, what therapies should you initiate immediately?

  • The following steps should be considered in management of the patient with external otitis:

    • gentle cleansing to remove debris including irrigation with hypertonic saline (3%) and cleansing with mixtures of alcohol (70-95%) and acetic acid

    • a cotton wick may be of value in enhancing distribution of the cleansing fluid

    • administration of a 10-day course of an otic antimicrobial agent, including a fluoroquinolone otic solution such as ofloxacin otic or ciprofloxacin-demethasone otic or neomycin alone or with polymyxin combined with hydrocortisone

  • Patients with malignant otitis externa may require systemic therapy with parenteral antibiotics including coverage for skin organisms, Staphylococcus aureus, and Pseudomonas species.

1. Anti-infective agents

If I am not sure what pathogen is causing the infection what anti-infective should I order?

  • The bacterial flora of the external canal is similar to the flora of skin elsewhere.

  • The ototopical agents that are available (noted above) have been successful in clinical studies and this suggests that they are effective against the skin organisms that are responsible for most cases of external otitis.

2. Next list other key therapeutic modalities.

What complications could arise as a consequence of otitis externa?

  • The vast majority of cases of external otitis remain localized. Malignant otitis externa may spread to adjacent areas including meningitis and other intracranial structures.

What should you tell the family about the patient's prognosis?

  • The patient and family can be assured that the infection, though painful, can be managed by local cleansing and otic antibiotics. Ear plugs may be necessary for swimmers who are prone to swimmer's ear. Patients should be advised about the consequences of placing foreign objects, including cotton swabs, in the external canal.

How can otitis externa be prevented?

  • Swimmers may choose to use ear plugs that will keep the ear canal free of moisture. Patients who are prone to use cotton swabs to clean the ear should be cautioned about the potential for irritation of the skin of the canal. Parents should be alert to the child who is prone to place foreign objects in the ear canal.

What's the Evidence?

Clark, WB, Brook, I, Bianki, D, Thompson, DH. "Microbiology of otitis externa". Otolaryngol Head Neck Surg. vol. 116. 1997. pp. 23-25.

(A study of the pathogens responsible for otitis externa.)

Roland, PS, Dohar, JE, Lanier, BJ. "Topical ciprofloxacin-dexamethasone otic suspension is superior to ofloxacin otic solution in the treatment of children with acute otitis media with otorrhea through tympanostomy tubes". Pediatrics. vol. 113. 2004. pp. 340-6.

(A study of a steroid-antibiotic combination that was demonstrated to be effective in the external otitis media resulting from acute otitis media.)

Jones, RN, Milazzo, J, Seidlin, M. "Ofloxacin otic solution for treatment of otitis externa in children and adults". Arch Otolaryngol Head Neck Surg. vol. 123. 1997. pp. 1193-2000.

(Otic antibiotics were demonstrated to be effective in treatment of otitis externa.)

Kenna, MA, Alpter, CM, Bluestone, CD, Casselbrant, ML. "Intravenous antibiotics for otorrhea". Advanced therapy of otitis media. BC Decker. 2004. pp. 261-265.

(Management of malignant external otitis media with parenteral antibiotics.)
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