Sunday, January 15, 2006

external otitis

External otitis is inflammation of the external auditory canal. This disorder may be classified as infectious (inflammatory), eczematoid, or seborrheic and may be acute, recurrent, or chronic. Although external otitis can affect all age groups, the elderly are more susceptible. The symptoms common to all forms are itching, edema, pain, and discharge from the ear canal. Heat and humidity lower the canal skin's resistance to infection. This accounts for an increased frequency of infection during the summer months. In inflammatory external otitis the infecting organisms are usually staphylococcus (for acute localized), Pseudomonas aeruginosa (for acute diffuse) and Aspergillus niger, actinomyces, or yeasts (for chronic diffuse). Topical and systemic antibiotics are used in treatment followed by dilute alcohol solutions to keep the canal dry and clean. The major causes of eczematoid external otitis are topical antibiotics or ear vehicles (as in dermatatis medicamentosa); allergy to chemicals or metals used around the ear, such as hair sprays or earrings (as in contact dermatitis); or atopic reaction due to ingested antigen (as in atopic dermatitis). Eczematoid external otitis is most difficult to treat because causative agents often remain undiagnosed. Corticosteroids combined with antibiotics in an otic solution produce rapid healing and are usually used for five days. Any ear preparation used for more than 10 days may itself produce an eczematoid reaction. Skin testing may be necessary in contact dermatitis. Atopy (hypersensitivity) is detected by a family history of allergy plus manifestations of asthma and hay fever. Each of these types represent a distinct form of allergy and are characterized by histamine release in the tissue. Because of its allergic nature, eczematoid external otitis tends to be recurrent. Each episode tends to make the ear more susceptible to future attacks. Control of seborrheic dermatitis of the scalp is necessary to control seborrheic external otitis. The best agent for this is a selenium sulfide shampoo once a month. Silver nitrate and diluted alcohol are used on the canal and concha to keep them clean and dry.
Malignant external otitis is a special form of acute diffuse external otitis typically occurring in elderly diabetic patients. This infection is usually unilateral and begins with itching, which is followed by painful discharge and swelling.
Topical therapy is ineffectual and the disease progresses to involve the surrounding tympanic bone. Intense pain develops, and profuse granulation blocks the ear canal. Facial nerves may become involved causing peripheral paresis or paralysis. Temporizing treatments are contraindictated as the disease will extend to involve the surrounding areas of the temporal bone: the mastoid squamous and petrous portions. Sequestration (isolation) of the temporal bone and even death have occurred in a number of these patients, thus the ominous name-malignant external otitis.
This pathology is a progressive osteomyelitis (inflammation of the bone and bone marrow) with Pseudomonas aeruginosa as the usual infecting organism. Standard treatment is hospitalization of the patient together with the use of high doses of antibiotics specific for Pseudomonas for an extended length of time.
Special attention to diabetic management and to proper aural hygiene is indicated to prevent recurrence of the problem.
See also OTITIS MEDIA.
Ballenger, J. J. Diseases of the Nose. Throat. Ear, Head and Neck. 13th ed. Philadelphia: Lea & Febiger, 1985.

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