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3.02 Otitis Externa (Swimmer's Ear)


Presentation

The patient complains of ear pain, always uncomfortable and sometimes unbearable, often accompanied by drainage and a blocked sensation, sometimes by fever. When the condition is mild or chronic there may be itching rather than pain. Pulling on the auricle or pushing on the tragus of the ear classicly causes increased pain. The tissue lining the canal may be swollen and in severe cases the swelling can extend the the soft tissue surrounding the ear. Tender erythematous swelling or an underlying furuncle may be present, and it may be pointing or draining. The canal may be erythematous and dry or it may be covered with fuzzy cotton-like grayish or black fungal plaques. Most often, the canal lining is moist, covered with purulent drainage and debris, and cerumen is characteristically absent. The canal may be so swollen that it is difficult or impossible to view the tympanic membrane, which when seen often looks dull.

What to do:

What not to do:

Discussion

Otitis externa has a seasonal occurrence, being more frequently encountered in the summer months, when the climate and contaminated water will most likely precipitate a fungal or Pseudomonas aeruginosa bacterial infection. Various dermatoses, diabetes, aggressive ear cleaning with cotton-tipped applicators, previous external ear infections and furunculosis also predispose patients to developing otitis externa.

The healthy ear canal is coated with cerumen and sloughed epithelium. Cerumen is warer-repellant and acidic, and contains a number of antimicrobial substances. Repeated washing or cleaning can remove this defensive coating. Moisture retained in the ear canal is readily absorbed by the stratum corneum. The skin becomes macerated and edematous and the accumulation of debris may block gland ducts, preventing further production of the protective cerumen. Finally, endogenous or exogenous organizms invade the damaged canal epithelium and cause the infection.

Malignant or necrotizing external otitis is a life-threatening condition that occurs primarily in elderly diabetic patients as well as any immunocompromised individual. The pathognomonic sign of malignant external otitis is the presence of active granulation tissue in the ear canal. Early consultation should be obtained if there is any suspicion of this condition in a susceptable patient with a draining ear.

The ear is innervated by the fifth, seventh, ninth and tenth cranial nerves and the second and third cervical nerves. Because of this rich nerve supply, the skin is extremely sensitive. Otalgia may arise directly from the seventh cranial nerve (geniculate ganglion), ninth cranial nerve (tympanic branch), the external ear, the mastoid air cells, the mouth, teeth, or esophagus. Ear pain can result from sinusitis, trigeminal neuralgia and temperomandibular joint dysfunction opr be referred from disorders of the pharynx and larynx. A mild pain referred to the ear may be felt as itching, cause the patient to scratch the ear canal, and present as an external otitis. When the source of ear pain is not readily apparent, the patient should be referred for a more complete otolaryngologic investigation.


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from Buttaravoli & Stair: COMMON SIMPLE EMERGENCIES
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