Definition of otitis externa
- Most commonly used to indicate a bacterial infection of the external auditory canal.
- Technically means inflammation and can be due to various aetiologies.
- Involvement of the pinna is commonly due to a spreading cellulitis (including the lobule and can spread to facial skin) or perichondritis (cartilaginous infection excluding the lobule).
Epidemiology of otitis externa
- Affects 10% of the population at some time and 1 in 100 people will have it diagnosed per year.
- More common in swimmers.
- Be careful in people with diabetes: Increased risk of malignant/necrotizing otitis externa which is osteomyelitis of the skull base.
Causes of otitis externa
- Bacterial (Pseudomonas, Staph aureus)
- Fungal (aspergillus or candida)
- Less commonly viral (zoster)
- Inflammatory skin diseases of any sort
- Dermatitis (contact or seborrheic); psoriasis; acne
- Earplugs, hairspray, hearing aids, swimming-pool water, sweat, ear syringing. These can also precipitate infective otitis externa
Features of otitis externa
- Earache (can be severe)
- Make sure to ask about diabetes
USMLE-based video on otitis externa
Examination in otitis externa
- Narrowed and inflamed ear canal
- Debris and discharge in the ear
- Usually whitish. If hyphae/black think fungal causes
- Polyp due to recurrent inflammation
- Necrotising/malignant otitis externa
- Extension of the infection into the mastoid bone, which gives severe pain and headache, facial nerve palsy (sometimes), failure of treatment and a positive bone scan.
- Usually caused by pseudomonas
Treatment of otitis externa
- Topical eardrops
- Ciprofloxacin, sofradex, gentisone-HC.
- Ciprofloxacin if safe if there is a perforation.
- Aural toilet
- Either dry mop or microsuction (required secondary care referral)
- If canal is very narrowed may require a small expanding sponge (‘pope wick’) in the canal to help drops get in.
- These should be removed after 48 hours.
- Oral medication alone will not treat it unless there is spread to pinna/face. This requires admission as well as above treatment.
- Send a swab if no improvement after 1 week.
- In necrotising otitis externa, pseudomonas is usually the cause, and treatment with several weeks of intravenous antibiotics and topical ear drops is required.
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