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Otitis externa
Otitis externa

Otitis externa

Pathophysiology

Inflammation of the skin within the external ear allows for debris and discharge accumulation → narrowing of the canal → trapping of pathogens and worsening of infection.

Otitis externa is also known as swimmer’s ear.

The causes can be:

  1. Bacterial infection - most commonly P. aeruginosa, S. aureus, S. epidermidis.
  2. Fungal infection - most commonly Candida spp. and Aspergillus spp., this is often following a course of antibiotics as the antibiotics can kill of the microflora, allowing opportunistic fungi to overgrow.
  3. Dermatitis
    1. Sebhorreic dermatitis -
    2. Contact dermatitis - allergy or irritants.
    3. Atopic dermatitis (eczema)
  4. Swimming - swimming is often the cause and water in the ear canal provides a suitable moist environment for bacterial grow
💊
For p. aeruginosa we use ciprofloxacin (a quinolone) or gentamicin (an aminoglycoside).
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⚠️ Risk factors

  • Swimming
  • Narrow ear canals
  • Humid environment
  • Eczema or psoriasis
  • Local trauma
  • Immunocompromised or diabetic patients

😷 Presentation

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☝🏼
On examination:

⭐️ The ear will be red swollen (especially around the pinna), and tender (around the tragus).

Lymphadenopathy may be present.

  • ⭐️ Ear pain
  • ⭐️ Purulent discharge
    • The colour of the discharge is important for differentiating the cause:
      1. White/yellow - bacterial.
      2. Thick white/grey with visible hyphae or spores - fungal.
      3. Grey - otitis media.
  • ⭐️ Itchy ear
  • Conductive hearing loss - if the ear is blocked.
  • Red tympanic membrane - if the otitis externa extends to the membrane, however if it is ruptured it may be from otitis media.
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🔍 Investigations

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It is predominantly a clinical diagnosis with otoscopic findings.

Swabs may be taken if the symptoms are refractory to antibiotic treatment, or if there are signs of fungal infection (thick white/grey discharge and hyphae).

A High Resolution CT may be taken to investigate the extent of the infection.

🧰 Management

Management of course depends on the cause of the disease:

🦠
Bacterial
  • Prophylaxis - acetic acid 2% (EarCalm). It is available OTC and is both anti-fungal and anti-bacterial. To be used before and after swimming.
  • Mild otitis externa - acetic acid 2% (EarCalm).
  • Moderate otitis externa - topical antibiotics (neomycin, gentamicin, ciprofloxacin) and a steroid (hydrocortisone, dexamethasone).

    • If the ear is too blocked with discharge or wax, we need to refer the patient to ENT for micro-suction before topical treatment.

  • Severe otitis externa - oral antibiotics.
🍄
Fungal

→ Clotrimazole (Canestan) - as ear drops.

🚨
It is important to remember that gentamicin is an ototoxic drug, so they can cause hearing loss if they get into the middle ear. Therefore, we need to check if tympanic membrane is perforated before we give it. If it is perforated, we do not give it.

Conservative measures include:

  • Keep the ears clean and dry.
  • Ear plugs and or tight fighting cap when swimming.
  • Use acidifying ear drops or spray shortly before swimming, after swimming, and at bedtime.
  • Acute otitis externa > abstain from water sports for at least 7 to 10 days.
  • Using a hair dryer (at the lowest heat setting) to dry the ear canal after hair washing, bathing, or swimming.
  • Keeping shampoo, soap, and water out of the ear.
  • Ensure skin conditions that are associated with the development of otitis externa are well controlled.

🚨 Complications

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  • Malignant otitis externa - a life threatening condition that can lead to → temporal osteomyelitis. It is also known as acute necrotising otitis externa.
    • It is most common in diabetic patients.
    • There will be granulation tissue present at the junction between bone and cartilage in the ear (about halfway through the canal).
    • Severe otalgia.
    • Temporal headaches.
    • Purulent otorrhoea.
    • Dysphagia, hoarse voice, facial nerve dysfunction may also be present.