Otitis externa

Otitis externa is inflammation of the outer-ear canal, commonly due to infection. It usually causes swelling, a discharge, and, in some people, eczema around the opening of the ear canal. The ear may be itchy and painful and blocked with pus, causing deafness. 

Causes

Generalized infection of the canal, and sometimes of the pinna (external ear), may be due to a fungal or bacterial infection. The ear may also sometimes become inflamed as part of a generalized skin disorder such as atopic eczema or seborrhoeic dermatitis.

Treatment

Often, the only treatment required is to keep the ear clean and dry until the infection has cleared. Locally acting preparations that contain antibiotic drugs, antifungal drugs, or corticosteroid drugs may be used. Oral antibiotics may be given to treat bacterial infections if they are severe.

Acute otitis externa in detail - technical

Otitis externa is also known as swimmer’s ear.

Definition

Acute otitis externa (AOE) is an acute bacterial infection of the subdermis of the external auditory canal.

Etiology

The infection occurs more commonly in summer months, often in association with water sports, and is commonly referred to as “swimmer’s ear.”

Predisposing factors, in addition to warmth and moisture, are micro-trauma from scratching or instrumenting the ear, preexisting seborrheic dermatitis of the ear canal, and alkalization of the external canal (Coffin 1963; Fabricant and Perlestein 1949). The most commonly recovered pre-therapy isolates are Pseudomonas species (most commonly aeruginosa), and Staphylococcus aureus. Less frequently, other gram negatives, especially Proteus sp. and Klebsiella, are encountered (Hawke et al. 1984; Roland and Stroman 2002).

Clinical Presentation

The principal symptom is pain, which is sometimes very severe. Pain is exacerbated by movement of the auricle or tragus which helps distinguish the pain of AOE from the pain of acute otitis media. Pain develops steadily over hours to a day or two. Hearing loss is common only in moderate to severe cases when swelling compromises the patency of the external auditory canal (Marple and Roland 1997).

The infection is often accompanied by a scanty, milky drainage but it is usually neither copious nor thick. Both swelling of the ear canal and erythema are often present but severe swelling tends to limit erythema and sometimes, if swelling is very severe, the canal skin is blanched (Hawke et al. 1984). Diagnosis Diagnosis rests mainly on physical findings and no additional diagnostic testing or laboratory evaluation is needed.

Differential Diagnosis

  • Herpes Zoster Oticus
  • Carcinoma of the external auditory canal or temporal bone
  • Eczematous dermatitis
  • Otitis media with perforation
  • Folliculitis
  • Malignant otitis externa

Prophylaxis

In patients prone to recurrent acute otitis media, dry ear precautions can be helpful in preventing infection. If the patient will or cannot avoid water, drying the ear canal with a blow-dryer on a low setting or using alcohol-containing otic drops can prevent recurrent infections. Foreign bodies such as cotton swabs should be avoided.

Therapy

Treatment should include cleansing of the external auditory canal (aural toilet) and use of an antimicrobial topical ear drop (Rosenfeld et al. 2006a). Both antiseptic and antibiotic drops are used with equal efficacy. Since alkalization of the normally slightly acidic EAC is important in the pathophysiology of the AOE, acidic solutions are useful (and may be sufficient) in resolving the infection (Coffin 1963; Rosenfeld et al. 2006b). Among the antibacterial agents, the fluoroquinolones may be slightlymore effective than the aminoglycosides and are not ototoxic (Roland et al. 2004).

Preparations without potential ototoxicity should be used unless it is certain that the tympanic membrane is intact.

Antibiotic drops are commercially available as 2–3% solutions which have antibiotic concentrations of 2,000–3,000 mcg/mL: concentrations which greatly exceed the MICs of any known relevant pathogen (Rosenfeld et al. 2006b; Roland et al. 2004). Consequently, antibiotic sensitivity profiles performed in commercial laboratories are not relevant and topical antibiotic solutions will be effective even against organisms labelled “resistant” provided only that the antibiotic solution comes into contact with infected tissues.

Successful treatment depends on contact of the topically administered ear drop with the infected skin of the ear canal. If the ear canal is swollen, then a wick should be utilized to help keep the canal open and to draw the medication into the canal and keep it in contact with the canal skin.

Assuming that the infection is bacterial, as is most commonly the case, failures of topical therapy are failures of delivery. Systemic antibiotics are rarely indicated for the treatment of acute otitis externa but an exception to this rule is appropriate for persons with diabetes or other immunocompromising conditions.

Acute otitis externa is often painful and appropriate management of pain is an important aspect of comprehensive treatment. When the condition is severe, oral narcotic analgesics are sometimes necessary for adequate pain control.

Prognosis

The prognosis is excellent for patients with routine acute otitis externa. In immunocompromised patients, otitis externa can progress to malignant otitis externa. This is a potentially life-threatening infection requiring intravenous antibiotics and possible surgery.

References

Coffin P (1963) pH as a factor in the external otitis. N Engl J Med 268:287–289

Fabricant N, Perlestein M (1949) pH of the cutaneous surface of the external auditory canal; a study of 27 infants, 44 children and 60 adults. Arch Otolaryngol 49(2):201–209

Hawke M, Wong J, Krajden S (1984) Clinical and microbiological features of otitis externa. J Otolaryngol 13(5): 289–295

Marple B, Roland P (1997) External auditory canal. In: Roland PS, Marple BF, Meyerhoff WL (eds) Hearing loss. Thieve, New York, pp 133–153

Roland P, Stroman D (2002) Microbiology of acute otitis externa. Laryngoscope 112(7 Pt 1):1166–1177

Roland P, Pien F, Schultz C et al (2004) Efficacy and safety of topical ciprofloxacin/dexamethasone versus neomycin/ polymyxin B/hydrocortisone for otitis externa. Curr Med Res Opin 20(8):1175–1183

Rosenfeld RM, Brown L, Cannon CR, Dolor RJ, Ganiats TG, Hannley M, Kokemueller P, Marcy SM, Roland PS, Stinnett SS, Witsell DL (2006a) Clinical practice guideline: acute otitis externa. Otolaryngol Head Neck Surg 134(4 Suppl):S4–S23

Rosenfeld R, Singer M, Wasserman J et al (2006b) Systematic review of topical antimicrobial therapy for acute otitis externa. Otolaryngol Head Neck Surg 134(4):24–28.