A 76-year old woman presents has severe otalgia in her left ear that has been gradually worsening over the past few weeks. She describes the pain as being ‘unrelenting’ and she has been unable to sleep for several nights. Her family have noticed that the left side of her face appears to be ‘drooping’. Her past medical history includes poorly controlled type 2 diabetes mellitus. She was diagnosed with otitis externa by a colleague a few weeks earlier but the pain has failed to settle despite two separate courses of antibiotic drops. On examination she has a left-sided lower motor neuron facial nerve palsy. Her left ear canal is very swollen and purulent exudate is visible (a photo of her ear is shown below). You are unable to clearly view her tympanic membrane. A swab of the ear taken last week has cultured Pseudomonas aeruginosa.
1. What is the most likely diagnosis?
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This patient has a diagnosis of malignant otitis externa (MOE). MOE, which is also known as necrotizing otitis externa, is a rare form of otitis externa that most commonly affects elderly diabetic patients, especially if their diabetes is poorly controlled.
MOE starts as an infection of the ear canal and progressively spreads into the bony ear canal and underlying soft tissues. Pseudomonas aeruginosa is the responsible pathogen in 98% of cases.
It usually presents with severe otalgia and refractory otitis externa. The pain is characteristically described as being ‘unrelenting’ and is often worse at night. Pain can persist even after swelling of the ear canal has resolved with topical antibiotics. Purulent otorrhoea and temporal headaches can also be present. A facial nerve palsy is present in approximately 50% of patients and cranial nerves IX to XII may also be involved.
Image sourced from Wikipedia
Courtesy of James Heilman CC BY-SA 3.0
2. What further investigations should be organized?
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Investigation is with technetium scanning and contrast-enhanced CT scanning. Imaging evidence of extension of the infection into surrounding bony structures is usually needed to confirm the diagnosis.
3. What complications can occur?
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Untreated it can be life-threatening and serious complications include:
- Skull base osteomyelitis
- Subdural empyema
- Cerebral abscess
4. How is this condition treated?
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Treatment usually involves prolonged courses of intravenous antibiotics. MOE is not amenable to surgical treatment, but exploratory surgery may facilitate culture of unusual organisms that are not responding adequately to treatment with intravenous antibiotics.
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