Otitis Externa
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Direct answer
Otitis externa is inflammation of the external auditory canal, most often diffuse bacterial infection presenting with severe ear pain, itching and tragal tenderness, frequently triggered by water exposure or scratching. It includes three classical varieties examiners expect: the circumscribed furuncle of the cartilaginous canal, fungal otomycosis, and malignant or necrotising otitis externa — a life-threatening Pseudomonas infection of the diabetic elderly that spreads to the skull base.
What you must remember
- Diffuse otitis externa: hot humid climate, water entry (swimmer's ear) and trauma from ear buds; presents with otalgia, discharge and pain on tragal pressure or auricle traction, with an oedematous canal lined by debris.
- Furuncle: a staphylococcal abscess of a hair follicle, so it occurs only in the cartilaginous outer third of the canal where hair and ceruminous glands exist; treat with analgesics, warm local heat, antibiotic–steroid drops, and incision only if pointing.
- Otomycosis: caused most often by Aspergillus species and Candida; intense itching with a wet, creamy or black-specked ("wet newspaper") debris; treat by meticulous aural toilet followed by antifungal drops such as clotrimazole, and keep the ear dry.
- Malignant otitis externa: Pseudomonas aeruginosa in elderly diabetics and immunosuppressed patients; severe deep pain, granulation at the bony–cartilaginous junction, cranial nerve involvement and raised inflammatory markers.
- Diagnosis of malignant disease: computed tomography and bone scanning define skull base osteomyelitis; biopsy is needed to exclude carcinoma.
- Management principles: dry aural toilet is the mainstay; topical antibiotic with steroid drops, a wick when the canal is stenosed, and systemic antibiotics only for cellulitis, fever or malignant disease — long-course fluoroquinolones for malignant otitis externa.
- Prevention: avoid scratching and cotton buds, keep water out during bathing and swimming, and control diabetes.
Common confusion
Otitis externa is distinguished from acute otitis media by tenderness on pressing the tragus or pulling the pinna, absent in middle ear disease, and by a swollen, tender canal. Discharge through a perforation in acute otitis media comes with drum abnormality and no tragal tenderness. A furuncle is wrongly placed in the bony canal — no hair follicles exist medial to the cartilaginous portion.
Exam-focused takeaway
For theory, classify the disease into diffuse, furunculosis, otomycosis and malignant forms with features and management of each, giving the malignant form full space. In viva, expect the organism of malignant otitis externa, the site of furuncle, the appearance of fungal debris and the danger of blind probing. In the outpatient posting, practise speculum examination for canal oedema, debris colour and tragal tenderness, and learn atraumatic aural toilet, which is itself treatment.
Frequently asked questions
Which organism causes malignant otitis externa?
Pseudomonas aeruginosa, typically in elderly diabetic or immunosuppressed patients, producing skull base osteomyelitis with deep pain and possible cranial nerve palsies.
Why does a furuncle occur only in the outer third of the canal?
Hair follicles and ceruminous glands are confined to the cartilaginous part; the bony canal has thin skin without appendages.
How is otomycosis recognised and treated?
By intense itching and debris that looks wet or carries black spores; treatment is thorough aural toilet with topical antifungal drops and strict dry ear precautions.
What is the role of a wick in otitis externa?
When the canal is too oedematous for drops to enter, an impregnated wick carries the medicament along the canal and is removed as swelling subsides.
Why are systemic antibiotics avoided in ordinary otitis externa?
The infection is localised and topical therapy with aural toilet is effective; oral antibiotics are reserved for spreading cellulitis, fever or malignant otitis externa.
How is malignant otitis externa treated?
Diabetic control, prolonged systemic fluoroquinolone therapy active against Pseudomonas, meticulous local care, and surgical debridement only in selected refractory cases.