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Otitis externa (OE), also referred to as external otitis, is inflammation of the auricle, external ear, or tympanic membrane. The severity can range from mild inflammation to life-threatening infection.[1] It is commonly seen by family physicians and affects 4 out of each 1000 Americans every year.[2] In most cases the significant pain of OE compels the patient to seek care urgently.

OE can be categorized as localized or diffuse. When it persists for more than 6 months, it is considered chronic and is more commonly bilateral. It is thought to be caused by local trauma to the external canal, diabetes, high humidity, loss of the canal's protective coating of cerumen, eczema, use of a hearing aid or stethoscope, or glandular obstruction. It is commonly seen in swimmers, particularly in the summer months.[1] The most frequent symptoms are discharge, pain, hearing loss, itching, and tinnitus.

Necrotizing (malignant) otitis externa (NOE) is the most severe form of OE and is most often seen in elderly patients with diabetes. One case series in a referral population found a mortality rate of 53%.[3] Pain, purulent discharge, bilateral involvement, and external canal granulation tissue are common symptoms.

KEY WORDS Otitis externa; ear canal; infection. (J Fam Pract 2001; 50:353-360)

KEY POINTS

* Otitis externa (OE) is a clinical diagnosis. Diagnostic testing is not necessary.

* The combination of ear cleaning, ear wicks, and topical medications is most effective for the treatment of OE. Use of a single topical intervention or oral antibiotics may be effective but is less well supported.

* Necrotizing otitis externa (NOE) is also a clinical diagnosis that is based on poor response to treatment and the presence of granulation tissue. It is more common in persons with diabetes, especially older patients.

* Ear cleaning, debridement, and oral ofloxacin or ciprofloxacin for up to 3 months are the preferred treatment for NOE.

PATHOPHYSIOLOGY

The ear canal is a blind sac with an anterior recess. Trauma to the canal, accumulation of keratin, or a change in pH can trigger inflammation and infection. One study[4] found that aerobic bacteria account for 91% of bacterial causes; anaerobes, 4%; and mixed infections, 4%. The most common offending organisms are Pseudomonas aeruginosa (50%), Staphylococcus aureus (23%), anaerobes and gramnegative organisms (12.5%), and yeast, such as Aspergillus and Candida (12.5%). The increased pH of pool water is believed to make infection more likely, since bacteriologic studies fail to show a direct link between swimming pool contamination and the organisms of OE.

DIAGNOSIS

There are no published studies of the accuracy of the medical history, physical examination, or office laboratory tests for the diagnosis of OE. Diagnosis is usually made based on physical examination findings: pain on movement of the auricle, edema, redness, and foul-smelling discharge.[5] Swelling often obscures the tympanic membrane.

NOE is also a clinical diagnosis and requires a high index of suspicion. A study by Zaky and colleagues[3] considered 2 new cases and 32 that were retrospectively reviewed from the literature. They found the following frequencies of symptoms: pain (100%0), purulent discharge (97%), bilateral involvement (21%), and a polyp in the external canal (88%). Diabetes was common in this group of patients (82%), confirming that it is consistently a predisposing risk factor, and 91% of these patients were aged 55 years and older.

Few papers have been published concerning diagnostic studies for NOE. One found that temporal radiographs and tomograms are positive in most cases of NOE but were not necessary for diagnosis.[6] The erythrocyte sedimentation rate is usually increased,[3] but this is true in many other illnesses. Many studies[3,8-9,31-35] have reported that Pseudomonas is the primary offending organism for NOE. Because most ear cultures are positive for Pseudomonas, these cultures are of questionable value.[10]

There are 4 studies that consider more aggressive diagnostic testing for NOE using conventional temporal radiographs, tomographic temporal radiographs, qualitative and single photon emission computed tomography [67]gallium scans, and qualitative and quantitative [99]technetium bone scans.[6-9] These studies were limited by the use of unclear[7] or poor quality[6,8] reference standards (radiograph or poor response to antibiotics). The diagnosis of NOE does not require additional studies. Expert opinion supports a diagnosis based on the history and physical examination and poor response to treatment. The most common symptom of NOE is persistent pain that is constant and severe. The leukocyte count may be normal or mildly elevated.[3] Physicians should consider the diagnosis of NOE in any patient with diabetes who has OE, particularly older patients. Characteristics of OE and NOE are presented in Table 1.

TREATMENT

Otitis Externa

The main principles of treatment are local cleansing of debris, drainage of the infection, re-establishment of the normal acidic environment, use of topical and systemic antimicrobials, and prevention of recurrent infections. The evidence regarding these treatments is summarized in Table 2. The best evidence (grade of evidence: A) demonstrates equivalent results with ear cleaning, an ear wick, and any of the choices of topical agents[12-13]--acidifying agents, antibiotics, antibiotic and steroid combinations, or antifungal agents. Frequent dosing (3 to 4 times daily) for at least 4 days is supported by the studies. Two studies demonstrated equivalent efficacy with topical ciprofloxacin or ofloxacin dosed twice daily compared with antibiotic and steroid combinations dosed 4 times daily.[16-17] However, these agents are also more expensive than older topical antibiotics. The evidence for single topical treatments and oral antibiotics is weaker[14-29] (grade of evidence: B). Physicians should treat patients with one of the following regimens for at least 4 days:

* ear cleaning + ear wick + acidifying agent dosed 4 times daily

* ear cleaning + ear wick + topical antibiotic dosed 4 times daily (twice daily if quinolone)

* ear cleaning + ear wick + topical antibiotic/steroid combination dosed 4 times daily (twice daily if quinolone)

The ear is best cleaned by simply irrigating the canal. Be sure to look for a foreign body, particularly in younger patients. For a wick, use either the Pope ear wick (Merocel Corporation, Mystic, Conn) or a fourth-inch sterile gauze. The wick helps draw topical medications into the affected canal, particularly when it is obstructed. The patient should return in approximately 2 days for removal of the wick and reassessment. Do not forget analgesics; this is a painful condition.

NECROTIZING OTITIS EXTERNA

The treatment for NOE must be aggressive. As the infection invades through the soft tissues into surrounding bony structures, it can be life threatening.[10] The evidence for various treatments is presented in Table 3. The studies are weaker than those for treatment of otitis externa (grade of recommendations: B and C). They support twice daily dosing with oral ofloxacin 400 mg orally twice daily or ciprofloxacin 750 mg orally twice daily for up to 3 months.[31-33] There is weak evidence that hyperbaric oxygen is effective.[34] Intravenous anti-Pseudomonal antibiotics are often used initially, based on expert opinion (grade: D) and the high mortality rate.

The oral fluoroquinolones (ofloxacin and ciprofloxacin) show promise for treating NOE. The choice of parenteral or oral antibiotics still rests with clinician judgment, based on the patient's clinical presentation. If oral antibiotics are started, the length of treatment should be based on the severity of illness.

PROGNOSIS

The prognosis for cure of OE is excellent, although the actual natural history of untreated disease has not been studied. OE complicated by NEO is more common in persons with diabetes who have a persistent course and granulation tissue visualized in the external auditory canal. Untreated NEO can lead to osteomyelitis and paralysis of cranial nerves. Death can result from sepsis and central nervous system infection.

REFERENCES

[1.] Agius AM, Pickles JM, Burch KL. A prospective study of otitis externa. Clin Otolaryngol 1992; 17:150-54.

[2.] Diagnosis and treatment of acute otitis media: an interdisciplinary update. Proceedings of a roundtable discussion. Ann Otol Rhinol Laryngol 1999; 108:2-23.

[3.] Zaky DA, Bentley DW, Lowy K, Betts RF, Douglas RG. Malignant external otitis: a severe form of otitis in diabetic patients. Am J Med 1976; 61:298-302.

[4.] Clark WB, Brook I, Bianki D, Thompson DH. Microbiology of otitis externa. Otolaryngol Head Neck Surg 1997; 116:23-25.

[5.] Leung AKC, Fong JHS, Leong AG. Otalgia in children. J Natl Med Assoc 2000; 92:254-60.

[6.] Kim BH. Roentgenographic findings of malignant external otitis. Am J Roentgenol Radium Ther Nucl Med 1971; 112:366-72.

[7.] Stokkel MPM, Boot ICN, vanEck-Smit BLF. SPECT gallium scintigraphy in malignant external otitis: initial staging and follow-up: case reports. Laryngoscope 1996; 106:338-40.

[8.] Uri N, Gips S, Front A, Meyer SW, Hardoff R. Quantitative bone and 67Ga scintigraphy in the differentiation of necrotizing external otitis from severe external otitis. Arch Otolarngol Head Neck Surg 1991; 117:623-26.

[9.] Hardoff R, Gips S, Uri N, Front A, Tamir A. Semiquantitative skull planar and SPECT bone scintigraphy in diabetic patients: differentiation of necrotizing (malignant) external otitis from severe external otitis. J Nucl Med 1994; 35:411-15.

[10.] Brook I. Treatment of otitis externa in children. Pediatric Drugs 1999; 1:283-89.

[11.] Densert O, Toremalm NG. Pain relief with indomethacin in external otitis. Arch Otolaryng 1972; 95:460-63.

[12.] Ordonez GE, Kime CE, Updegraff WR, Glassman JM, Soyka JP. Effective treatment of acute diffuse otitis externa: I. a controlled comparison of hydrocortisone-acetic acid, non-aqueous and hydrocortisone-neomycin-polymyxin b-colistin otic solutions. Curr Ther Res 1978; 23:ss3-14.

[13.] Kime CE, Ordonez GU, Updegraff WR, Glassman JM, Soyka JP. Effective Treatment of acute diffuse otitis externa: II. a controlled comparison of hydrocortisone-acetic acid, non-aqueous and hydrocortisone-neomycin-polymyxin b otic solutions. Curr Ther Res 1978; 23:ss15-28.

[14.] Freedman R. Versus placebo in treatment of acute otitis externa. Ear Nose Throat J 1978; 57:28-37.

[15.] Gyde MC, Norris D, Kavalec EC. The weeping ear: clinical reevaluation of treatment. J Int Med Res 1982; 10:333-40.

[16.] Arnes A, Dibb WL. Otitis externa: clinical comparison of local ciprofloxacin versus local oxytetracycline, polymyxin B, hydrocortisone combination treatment. Curt Med Res Opin 1993; 13:182-86.

[17.] Jones RN, Milazzo J, Seidlin M. Ofloxacin otic solution for treatment of otits externa in children and adults. Arch Otolaryngol Head Neck Surg 1997; 123:1193-200.

[18.] Wadston CJ, Bertilsson CA, Sieradzki H, Edstrom S. A randomized clinical trial of two topical preparations (framycitin/gramicidin and oxytetracycline/hydrocortisone with polymyxin b) in the treatment of external otitis. Arch Otorhinolaryngol 1985; 242:135-39.

[19.] Barton RPE, Wright JLW, Gray RFE. The clinical evaluation of a new clobetasol propionate preparation in the treatment of otitis externa. J Laryngol Otol 1979; 93:703-06.

[20.] Treatment of otitis externa: a clinical trial of local applications. Br J Clin Pract 1967; 21:507-10.

[21.] Bain DJG. A double-blind comparative study of otoseptil ear drops and otosporin: ear drops in otitis externa. J Int Med Res 1976; 4:79-81.

[22.] Worgan D. Treatment of otitis externa: report of a clinical trial. Practitioner 1969; 202:817-20.

[23.] Yelland MJ. The efficacy of oral cotrimoxazole in the treatment of otitis externa in general practice. Med J Aust 1993; 158:697-99.

[24.] Barr GD, Al-Khabori M. A randomized prospective comparison of two methods of administering topical treatment in otitis externa. Clinical Otolaryng Allied Sci 1991; 16:547-48.

[25.] Clayton MI, Osborne JE, Rutherford D, Rivron RP. A double-blind, randomized, prospective trial of a topical antiseptic versus a topical antibiotic in the treatment of otorrhea. Clin Otolaryngol 1990; 15:7-10.

[26.] Cannon S. External otitis: controlled therapeutic trial. Eye Ear Nose Throat Monthly 1970; 49:56-61.

[27.] Slack RWT. A study of three preparations in the treatment of otitis externa. J Laryngol Otol 1987; 101:533-35.

[28.] Smith RB, Moodie J. A general practice study to compare the efficacy and tolerability of a spray ("Otomize") versus a standard drop formulation ("Sofradex") in the treatment of patients with otitis externa. Curr Med Res Opin 1990; 12:12-18.

[29.] McGarry GW, Swan IRC. Endoscopic photographic comparison of drug delivery by ear-drops and by aerosol spray. Clin Otolaryngol 1992; 17:359-60

[30.] Wilde AD, England J, Jones AS. An alternative to reguler dressings for otitis externa and chronic supperative otitis media? J Laryngol Otol 1995; 109:101-03.

[31.] Gehanno P. Ciprofloxacin in the treatment of malignant external otitis. Chemotherapy 1994; 40:35-40.

[32.] Levy R, Shpitzer T, Shvero J, Pitlik SD. Oral ofloxacin as treatment of malignant external otitis: a study of 17 cases. Laryngoscope 1990; 100:548-51

[33.] Zikk D, Rapoport Y, Redianu C, Shalit I, Himmelfarb MZ. Oral ofloxacin therapy for invasive external otitis. Ann Otol Rhinol Laryngol 1991; 100:632-37.

[34.] Mader JT, Love JT. Malignant external otitis: cure with adjunctive hyperbaric oxygen therapy. Arch Otolaryngol 1982; 108:38-40.

[35.] Neu HC. Contemporary antibiotic therapy in otolaryngology. Otolaryngol Clin N Am 1984; 17:745-60.

* Submitted, revised, March 4, 2001.

From the Clinton Memorial Hospital Family Practice Residency, Wilmington, and the University of Cincinnati Department of Family Medicine. Reprint requests should be addressed to Keith B. Holten, MD, Family Health Center, 825 W. Locust St, Wilmington, OH 45177. E-mail: keholtenmd@cmhregional.com.

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