⚠️ Necrotizing external otitis should be suspected when patients with diabetes mellitus or other immunocompromised states present with persistent, severe external otitis, especially with nocturnal pain.
🔥 Malignant otitis externa indicates extension to osteomyelitis of the temporal bone – this is a surgical emergency requiring urgent ENT referral, admission for IV antibiotics, and possible surgery.
ℹ️ About
- 🦠 Infection of the external auditory canal (EAC), commonly referred to as “swimmer’s ear”.
- 🌡️ Common in hot, humid climates, but severe cases occur in immunocompromised patients (especially diabetics).
- 💀 Malignant otitis externa = infection spreading to the temporal bone → osteomyelitis with risk of cranial nerve involvement.
Microbiology
- Pseudomonas aeruginosa – most common and aggressive pathogen 🧫.
- Staphylococcus aureus, S. epidermidis.
- Streptococcus pneumoniae.
- Occasionally Gram negatives and fungi (e.g. Aspergillus, Candida).
Aetiology & Risk Factors
- 🏊 Swimming in chlorinated or contaminated water (high halogen concentration).
- 🧴 Minor trauma from cotton buds, hearing aids, or scratching the EAC.
- 🧴 Underlying skin conditions (eczema, psoriasis).
- ⚠️ Diabetes mellitus – microvascular disease + pseudomonal vasculitis → poor perfusion and impaired healing.
- Severe spread: via fissures of Santorini to temporal bone → osteitis, mastoid involvement, petrous apex spread.
🩺 Clinical Features
- 🎯 Localised: Severe otalgia (often worse at night), itching, erythema, and otorrhoea.
- 🔎 Tenderness over tragus/pinna, oedema, and canal debris.
- 🚨 Malignant form:
- Granulation tissue at the bone–cartilage junction (classic sign).
- Facial nerve palsy (CN VII) ± other cranial neuropathies if advanced.
- Risk of skull base osteomyelitis.
🔎 Investigations
- 🧪 Baseline: FBC, U&E, LFTs, glucose, calcium, ALP, CRP.
- 📸 Imaging:
- CT temporal bone → bony erosion.
- Technetium-99m bone scan → detects osteomyelitis.
- Gallium-67 scintigraphy → helpful for monitoring treatment response.
- 🧫 Ear swab/culture to guide antibiotics.
💊 Management
- 🧴 Simple cases:
- Keep ear dry, no cotton buds/hearing aids during infection.
- Topical antibiotic + steroid drops (e.g. ciprofloxacin/dexamethasone).
- Ear wick insertion if canal is swollen/occluded.
- ⚠️ Malignant otitis externa:
- Urgent ENT admission.
- IV antibiotics active against Pseudomonas (e.g. ciprofloxacin, piperacillin–tazobactam, ± aminoglycosides).
- Correction of underlying immunosuppression (e.g. optimise diabetes).
- Local debridement; surgery only if refractory or complications (abscess, osteomyelitis progression).
⚠️ Complications
- Facial nerve palsy.
- Extension to skull base → cranial neuropathies (IX, X, XI).
- Intracranial spread (abscess, meningitis).
🧾 Clinical Case – Malignant Otitis Externa
A 70-year-old man with poorly controlled type 2 diabetes presents with severe ear pain, foul-smelling discharge, and hearing loss.
Examination reveals a swollen, tender external auditory canal with granulation tissue at the floor of the canal.
He also reports new-onset facial weakness.
CT temporal bone shows extension into the skull base.
👉 Diagnosis: Malignant otitis externa caused by Pseudomonas aeruginosa.
👉 Management: prolonged IV antipseudomonal antibiotics (e.g. ceftazidime), strict glycaemic control, and ENT referral for monitoring of cranial nerve involvement.
