Necrotizing (malignant) otitis externa
Necrotizing (malignant) otitis externa is skull-base osteomyelitis, almost always from Pseudomonas aeruginosa, that spreads from otitis externa into the temporal bone of older diabetics and other immunocompromised patients. Otalgia out of proportion to exam plus granulation tissue at the bony-cartilaginous junction of the canal is the hallmark, and treatment is weeks of antipseudomonal therapy, not a course of ear drops.
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What this article covers
- Overview
Skull-base osteomyelitis arising from otitis externa: an invasive infection that penetrates the cartilaginous and bony structures of the ear canal and extends into the temporal bone, causing osteomyelitis of the skull base.
- Epidemiology
Older adults with diabetes are the dominant group: classically described in elderly patients with diabetes mellitus, whose impaired microvascular perfusion and phagocytic function in the ear canal permit invasion.
- Risk factors
Poorly controlled diabetes mellitus: the single most consistently described risk factor.
- Pathophysiology
Infection begins in the external auditory canal: the same superficial process as otitis externa, typically Pseudomonas aeruginosa colonizing a moist, traumatized, or occluded canal.
- Clinical features
Otalgia severe and out of proportion to the visible exam findings: the dominant early symptom, often disproportionately intense for what uncomplicated otitis externa would produce, reflecting bone…
- Differential diagnosis
Uncomplicated otitis externa: pain and discharge are milder, there is no bony-cartilaginous junction granulation tissue or bone erosion, and it resolves with topical therapy alone; see otitis-externa.
- Diagnosis
The diagnosis is confirmed by tissue sampling in a compatible clinical picture, worked up the same way as any suspected osteomyelitis: there is no formal scored criteria set; it rests on…
- Management
Start empiric intravenous antipseudomonal antibiotics as soon as the diagnosis is suspected, before culture results return: ciprofloxacin 400 mg IV every 8 to 12 hours is the drug of choice; do not…
- Complications
Cranial nerve palsy, most often facial nerve (CN VII): the most commonly described neurologic complication, from osteomyelitic extension along the skull base into the nerve's bony canal.
- Prognosis
Outcome tracks how early treatment starts: disease treated before extensive bone destruction or cranial neuropathy carries a better course than disease with cranial nerve palsy or intracranial extension already present.
- Prevention
Treat uncomplicated otitis externa promptly and completely: mild otitis externa is treated with topical acetic acid for 7 to 10 days, and moderate otitis externa with a topical antibiotic and steroid…
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Related articles
- Otitis externa
Otitis externa is diffuse inflammation of the external auditory canal, usually bacterial (Pseudomonas or Staphylococcus aureus) and diagnosed clinically by tragal tenderness and canal erythema with otorrhea. Uncomplicated disease is treated with topical antibiotic-steroid otic drops for 7 days, while malignant (necrotizing) otitis externa in a diabetic or immunocompromised patient is skull-base osteomyelitis requiring systemic antipseudomonal therapy and urgent otolaryngology referral.
- Mastoiditis
Acute mastoiditis is a suppurative infection of the mastoid air cells, almost always arising as an extension of untreated or inadequately treated acute otitis media. It is diagnosed clinically by postauricular erythema, tenderness, and swelling with the auricle displaced anteriorly, and is treated with intravenous antibiotics escalating to myringotomy or mastoidectomy when abscess or complications are present.
- Osteomyelitis
Osteomyelitis is bone infection from hematogenous seeding or contiguous spread, most often from Staphylococcus aureus, presenting as subacute pain with or without a draining sinus tract and confirmed by bone biopsy culture. Empiric antibiotics are withheld until biopsy in a stable patient, and treatment combines source control with 4 to 6 weeks of culture-directed antibiotics, extended to 6 weeks or indefinite suppression for hardware-associated or chronic disease.
- Cavernous sinus thrombosis
Septic thrombosis of the cavernous sinus from spreading facial, sinus, or orbital infection, marked by fever, proptosis, chemosis, and cranial nerve palsies that classically become bilateral. It is a neuro-ophthalmic emergency treated with immediate broad-spectrum IV antibiotics, source control, and consideration of anticoagulation.
- Brain abscess
Brain abscess is a focal, ring-enhancing suppurative infection of the brain parenchyma most often from contiguous sinus, ear, or dental spread or hematogenous seeding, diagnosed by contrast MRI and image-guided aspiration and treated with predisposing-source-directed empiric antibiotics plus drainage of abscesses larger than 2.5 cm.