Otitis Externa
Otitis externa is infection (cellulitis) of the external auditory canal. It is classically associated with swimming. The most common cause is bacterial infection. The most common pathogen is Pseudomonas aeruginosa. Diagnosis is clinical. Investigations for otitis externa are only carried out if there is recurrent or treatment resistant otitis externa, or immunocompromised state. If otitis externa is recurrent, rule out diabetes and chronic underlying infection of the nasal passages which might be spread to the ears by the patient’s fingers.
Classification of otitis externa
| Classification | Examples |
|---|---|
| Infectious | Localised acute otitis externa (furuncle), diffuse acute otitis externa, otomycosis, herpes zoster oticus, otitis externa hemorrhagica |
| Reactive | Eczematous otitis externa, seborrhoeic otitis externa, neurodermatitis |
- Causes
- Bacterial infections (the most common cause; common organisms include Pseudomonas aeruginosa, Staphylococcus aureus)
- Fungal infection (Otomycosis – Aspergillus niger, A. fumigatus or Candida albicans. )
- Viral infection (Herpes zoster oticus)
- Allergies
- Eczema
- Psoriasis
- Risk factors
- Swimming
- Humidity
- Ear canal obstruction (cerumen impaction)
- Trauma (ear devices)
- Narrow ear canals
- Radiotherapy and chemotherapy
- Stress
- Immunocompromised states
- Signs and symptoms
- Ear Pain (especially with manipulation of the ear)
- Itching of the external auditory canal
- Draining of the external auditory canal
- Sensation of fullness
- Decreased hearing
- Cervical lymphadenopathy
- Pain on moving the jaw
- Otoscopic examination
- Erythematous and oedematous ear canal with debris
- Tympanic membrane may be difficult to visualize through the swollen ear canal (makes it difficult to rule out concomitant otitis media)
- Fungal mass on otoscopic examination in case of otomycosis
- Treatment
- Aural toilet and incision and drainage if an abscess has formed
- Topical antibiotics and steroid preparation
- Polymyxin B, neomycin, and hydrocortisone 3 to 4 drops to the affected ear four times a day.
- Ofloxacin 5 drops to the affected ear twice daily
- Ciprofloxacin with hydrocortisone 3 drops to the affected ear twice daily
- Analgesia – acetaminophen, NSAIDs
Malignant Otitis Externa
Malignant otitis externa is a life-threatening osteomyelitis of the skull base. It should be considered if simple otitis externa does not respond to antibiotics. It involves the external ear canal, temporal bone and skull base.
- Risk factors
- Diabetes
- Elderly
- Male
- Immunocompromised – chemotherapy, HIV, malignancy
- Persistent otitis externa
- Common microorganisms
- Pseudomonas aeruginosa – most common
- Proteus spp
- Klebsiella spp
- Staphylococcus aureus, with an increasing presence of methicillin-resistant S aureus (MRSA) strains
- S epidermidis
- Aspergillus spp
- Candida spp
- Investigations
- CT/MRI: best initial test
- Bone biopsy: most accurate test
- Complications
- Cranial nerve palsies
- Brain abscess
- Meningitis
- venous sinus thrombosis
- Treatment
- IV Ciprofloxacin → PO Ciprofloxacin
- Topical drops
- IV Ciprofloxacin → PO Ciprofloxacin
