Otitis media with tympanic perforation and discharge into the auditory canal may be confused with otitis externa. Pain on movement of the pinnae or tragus, typical of otitis externa, is not present. Local and systemic signs of mastoiditis indicate a process more extensive than otitis externa. Malignancies or cholesteatoma presenting in the auditory canal are rare in children but may present with discharge, unusual pain, or hearing loss.
Topical antimicrobial/corticosteroid otic preparations (such as ofloxacin, ciprofloxacin with hydrocortisone or dexamethasone, and polymyxin B-neosporin-hydrocortisone) are sufficient in most cases of otitis externa. These preparations are equally effective and are active against S. aureus and most gram-negative bacteria, including P. aeruginosa. None of these antibiotics has any antifungal activity. Use of aminoglycosides such as neomycin should be avoided in cases of tympanic membrane rupture due to their ototoxicity. Tympanostomy tube otorrhea is best treated with quinolone otic drugs, which is considered less likely to be ototoxic.
Treatment with topical otic analgesics and cerumenolytics is usually unnecessary. It is important with any topical therapy to remove purulent discharge from the external auditory canal with a swab or with suction to permit instillation of the solution. Excess water should be removed after bathing and the ear canal dried using a hairdryer. The predisposing activity, such as swimming or diving, should be avoided until the inflammation has resolved.
Fungi such as Aspergillus, Candida, and dermatophytes occasionally are isolated from the external ear. It may be difficult to determine whether they represent normal flora or are the cause of inflammation. In most cases, local therapy and restoration of normal pH as recommended for bacterial otitis externa are sufficient.
Malignant otitis externa is treated by parenteral antimicrobials with activity against P. aeruginosa, such as an expand-ed-spectrum penicillin (mezlocillin, piperacillin-tazobactam) or a cephalosporin with activity against P. aeruginosa (ceftazidime, cefepime) plus an aminoglycoside.
Acute otitis externa usually resolves promptly without complications within 1 to 2 days of initiating treatment. Persistent pain, especially if severe or if accompanied by other symptoms such as fever, should prompt re-evaluation for other conditions.
Complications of malignant otitis externa include invasion of the bones of the base of the skull, which may cause cranial nerve palsies. A mortality of 15% to 20% occurs in adults with malignant otitis media. Relapses within the first year after treatment are common.
Overvigorous cleaning of an asymptomatic auditory canal should be avoided. Drying the auditory canals with acetic acid (2%), Burow solution, or diluted isopropyl alcohol (rubbing alcohol) after swimming may be used prophylactically to help prevent the maceration that facilitates bacterial invasion. Often underwater gear, such as earplugs or diving equipment, must be avoided to prevent recurrent disease. There is no role for prophylactic otic antibiotics.