Disclaimer: The information contained within the Grand Rounds Archive is intended for use by doctors and other health care professionals. These documents were prepared by resident physicians for presentation and discussion at a conference held at Baylor College of Medicine in Houston, Texas. No guarantees are made with respect to accuracy or timeliness of this material. This material should not be used as a basis for treatment decisions, and is not a substitute for professional consultation and/or peer-reviewed medical literature. Otitis Externa Acute Otitis Externa is an infection of the skin of the cartilaginous portion of the ear canal. Contributing factors include moisture, canal occlusion, local trauma, and allergic disease. These factors lead to a loss of the protective wax layer, causing edema of the squamous epithelium with plugging of the glandular secretory ducts. Consequent scratching induces local trauma, allowing bacteria to invade through the skin, leading to inflammation and production of exudate. The pathogens in acute otitis externa are pseudomonas (41%), peptostreptococcus (22%), Staph. aureus (15%), and Bacteroides (11%). The differential diagnosis includes malignant external otitis, chronic external otitis, furunculosis, otomycosis, herpes zoster oticus, bullous external otitis, granular external otitis, chondritis, cellulitis, and eczematoid dermatitis. Malignant external otitis is a complication of acute otitis externa. The disease starts as a local infection of the external auditory canal and spreads through the fissures of Santorini (in cartilage of ear canal) towards the parotid gland and mastoid. This can lead to facial nerve paralysis. As the disease progresses, there is spread along the skull base to the jugular foramen (paralysis of CN IX, X, and XI), and finally to the hypoglossal canal (paralysis of CN XII). Symptoms are similar to acute otitis externa, however, the main difference is that the disease is not responsive to several weeks of conventional local therapy. On physical exam, there may be granulation tissue present in the ear canal, cranial nerve dysfunction, or a palpable bony defect in the anterior wall of the ear canal. Risk factors include diabetes, elderly, and immunocompromised status. The pathogen in malignant external otitis is nearly always Pseudomonas (99.2%). Relevant laboratory studies include an erythrocyte sedimentation rate (ESR) and a fasting glucose level. A bone scan is important to demonstrate osteomyelitis. It will remain positive for years after a full recovery, so it is not useful in following response to therapy. A gallium scan will demonstrate active inflammation in either soft tissue or bone, and it will return to normal if the disease is effectively treated. A CT scan is useful to determine bony erosion and soft tissue involvement, however its sensitivity for detecting osteomyelitis is low (30%). Therapy for malignant external otitis includes meticulous control of blood glucose, local debridement of granulation tissue, and possibly hyperbaric oxygen (Davis et al., 1992). Traditional antibiotic therapy is 6-8 weeks of IV drugs (usually an anti-pseudomonal penicillin or cephalosporin, and an aminoglycoside). Recent studies have demonstrated that oral ciprofloxacin has been 96.4% successful in treating mild to moderate malignant external otitis (Gehanno, 1994). In severe disease, IV therapy is recommended initially, and then a long course of oral ciprofloxacin is needed. Therapy is continued until the gallium scan is clear. Case Presentation A 59-year-old female was referred from the General Medicine Clinic for a 1 month history of bilateral ear pain and otorrhea. She had been treated with Cortisporin otic drops without benefit for several weeks. Her past history was unremarkable. She had no history of diabetes or immunosuppressed states. Physical exam revealed the left ear canal to be erythematous and tender. There was scant mucoid discharge and no granulations. The right ear canal was also erythematous, swollen, and tender. There was abundant mucoid discharge, and granulation tissue was present at the cartilaginous/bony junction posteriorly. Both tympanic membranes were normal. The rest of the exam was unremarkable. Laboratory studies revealed a slightly elevated WBC of 12.7, a greatly elevated ESR of 92, a normal random blood glucose of 100, and a slightly elevated glycosylated Hgb of 7.4. The patient was admitted to the hospital with the diagnosis of malignant external otitis. Her ears were debrided and cultures were sent, which eventually grew Pseudomonas aeruginosa. A CT scan done on admission showed soft tissue thickening around the ear canals, but was otherwise normal. A technetium bone scan was negative, and a gallium scan was positive for bilateral temporal inflammation. The patient was placed on ceftazidime and gentamicin otic drops. Her ear canals were regularly debrided. Twice daily blood glucose checks during hospitalization were all normal. After 10 days, her ear canals had no granulation tissue or discharge, and she was discharged to home on ciprofloxacin. In follow-up, she has been seen in at 2 weeks and 4 weeks post-discharge and has a normal exam. She is still taking ciprofloxacin. Bibliography Agius AM, Reid AP, Hamilton C. Patient compliance with short-term topical aural antibiotic therapy. Clin Otolaryngol 1994;19:138-141. Barrow HN, Levenson MJ. Necrotizing 'malignant' external otitis caused by Staphylococcus epidermidis. Arch Otolaryngol Head Neck Surg 1992;118:94-96. Benecke JE Jr. Management of osteomyelitis of the skull base. 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New York: Thieme Medical, 1992. 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 Otolaryngol Head Neck Surg 1991;117:623-626. Weinroth SE, Schessel D, Tuazon CU. Malignant otitis externa in AIDS patients: case report and review of the literature. Ear Nose Throat J 1994;73:772-778. Wilde AD, England J, Jones AS. An alternative to regular dressings for otitis externa and chronic supperative otitis media? J Laryngol Otol 1995;109:101-103. Wormald PJ. Surgical management of benign necrotizing otitis externa. J Laryngol Otol 1994;108:101-105. Grand Rounds Archive | Department Home page BCM Public | BCM Intranet | Privacy Notices | Contact BCM | BCM Site Map | ©2001-2006 Baylor College of Medicine
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