Malignant external otitis is typically a Pseudomonas osteomyelitis of the temporal bone. Methicillin-resistant Staphylococcus aureus (MRSA) can also cause malignant external otitis.
Soft tissue, cartilage, and bone are all affected by malignant external otitis. The osteomyelitis spreads along the base of the skull and may cause cranial neuropathies (VII usually affected first followed by IX, X, and XI) and may cross the midline.
Malignant external otitis occurs mainly in older patients with diabetes or in immunocompromised patients. It is often initiated by Pseudomonas external otitis; methicillin-resistant Staphylococcus aureus (MRSA) can also cause this infection.
Malignant external otitis is characterized by persistent and severe, deep-seated ear pain (often worse at night), foul-smelling purulent otorrhea, and granulation tissue or exposed bone 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 paralysis, and even lower cranial nerve (IX, X, or XI) paralysis, may ensue as this erosive, potentially life-threatening infection spreads along the skull base (skull base osteomyelitis) from the stylomastoid foramen to the jugular foramen and beyond.
Diagnosis of Malignant External Otitis
CT scan of the temporal bone
Culture
Biopsy
Diagnosis of malignant external otitis is suggested by high-resolution CT of the temporal bone, which may show increased radiodensity in the mastoid air-cell system, middle ear radiolucency (demineralization) in some areas, and bony erosion.
Cultures are done, and the ear canal must be biopsied to differentiate this disorder from a malignant tumor or neoplastic process (eg, squamous cell carcinoma).
Treatment of Malignant External Otitis
Systemic antibiotics, typically a fluoroquinolone and/or an aminoglycoside/semisynthetic penicillin combination
Rarely surgical debridement
Pseudomonas
Consultation with an infectious disease specialist for optimal antibiotic therapy and duration of therapy is recommended. Extensive bone disease may require more prolonged antibiotic therapy.
Hyperbaric oxygen may be a useful adjunctive treatment, but its definitive role remains to be elucidated.
If the patient has diabetes, meticulous control of diabetes is essential, and consultation with an endocrinologist for strict diabetic control is recommended. In immunocompromised patients, immunotherapy may be stopped.
Frequent debridement, done in office, is necessary to remove granulation tissue and purulent discharge. Usually surgery is not necessary, but surgical debridement to clear necrotic tissue may be used for more extensive infections (1).
Treatment reference
1. Al Araj MS, Kelley C: Malignant Otitis Externa. In: StatPearls (Internet). 2021; Treasure Island (FL): StatPearls Publishing: 2022 Jan PMID: 32310598.
