Malignant external otitis, also referred to as skull base osteomyelitis or necrotizing otitis externa, is typically a Pseudomonas osteomyelitis of the temporal bone.
Soft tissue, cartilage, and bone are all affected. The osteomyelitis spreads along the base of the skull and may cross the midline.
Malignant external otitis occurs mainly in elderly patients with diabetes or in immunocompromised patients and is often initiated by Pseudomonas external otitis. It is characterized by a persistent and severe, deep-seated earache (often worse at night), foul-smelling purulent otorrhea, and granulation tissue in the ear canal (usually at the junction of the bony and cartilaginous portions of the canal). Varying degrees of conductive hearing loss may occur. In severe cases, facial nerve, and even lower cranial nerve, paralysis may ensue as the infection spreads along the skull base from the stylomastoid foramen to the jugular foramen and beyond.
Diagnosis is based on a high-resolution CT scan of the temporal bone, which may show increased radiodensity in the mastoid air-cell system and middle ear radiolucency (demineralization) in some areas. Identifying bony erosion confirms the diagnosis. Cultures are done, and, importantly, the ear canal must be biopsied to differentiate the granulation tissue of this disorder from a malignant tumor.
Treatment is typically with a 6-wk IV course of a fluoroquinolone or an aminoglycoside/semisynthetic penicillin combination. However, mild cases may be treated with a high-dose oral fluoroquinolone on an outpatient basis with close follow-up. Consultation with an infectious disease specialist for optimal antibiotic therapy and duration and with an endocrinologist for diabetic control is recommended. Extensive bone disease may require more prolonged antibiotic therapy. Meticulous control of diabetes is essential. Surgery usually is not necessary.
Last full review/revision November 2012 by Bradley W. Kesser, MD