Otitis externa Flashcards

1
Q

Definition

A

Infection of the external auditory canal (EAC)

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2
Q

Aetiology

A

MC caused by:
- Pseudomonas aeruginosa
- Staphylococcus aureus
10-15% are fungal predominantly:
- Aspergillus
- Candida spp

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3
Q

Epidemiology and Risk Factors

A

Otitis externa is a common GP presentation, with an incidence >1% per year:
- Diabetes
- Dermatitis : any disruption of the normal skin barrier
- Trauma
- Moisture: swimming, humid environment

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4
Q

Risk factors for necrotising otitis externa

A
  • Head & neck radiotherapy
  • Diabetes
  • Advancing age
  • Immunosuppression
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5
Q

What is the cerumen?

A

Produced by glands in the EAC is acidic, providing a protective barrier for the thin dermis of the canal

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6
Q

Pathophysiology

A

Disruption of the cerumen barrier can occur with instrumentation (cotton buds, hearing aids, earplugs) leading to accumulation of moisture and a rise in pH.
This environment is conducive to the proliferation of organisms, invasion and inflammation.

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7
Q

Necrotising otitis externa (NOE)

A

AKA: malignant otitis externa
Invasive form of otitis externa that can lead to osteomyelitis of the temporal bone, multiple cranial nerve palsies and death.
The tight binding of the skin layer to the periosteum in the deep portions of the EAC accounts for the severe otalgia experienced by these patients.

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8
Q

Signs

A

Ottohoea
Erythema: EAC, may extend to pinna
Fever
Cranial nerve palsies: NOE
Granulation tissue in EAC: NOE

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9
Q

Symptoms

A
  • Pain: ear, jaw, headache. Severe in NOE (patients may wake at night)
  • Discharge
  • Pruritus
  • Hearing loss: conductive resolve with treatment
  • Facial weakness (NOE)
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10
Q

Diagnosis

A

Not required in uncomplicated cases in primary care.
- Swab: for microbiological analysis when there are persistent or recurrent symptoms, or suspicion of necrotising otitis externa
Blood glucose: poor blood glucose control in a diabetic may exacerbate infection

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11
Q

Investigations for potential NOE

A
  • FBC (leukocytosis), CRP, ESR,
  • Biopsy: granulation tissue in the EAC or any polyp = sent for MC+S and histology to exclude malignancy
  • Contact CT temporal bones: thickened + enhanced tissue (EAC) + bone erosion in NOE
  • Technetium-99m bone scan : increased uptake with bony involvement, highly sensitive for NOE
    Gallium-67 citrate scan : detects granulocyte: Assess treatment success, as changes to bone turnover detected by technetium scanning will persist through infection clearance
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12
Q

Treatment AOE

A
  • Analgesia: Para, Ibuprofen, Codiene
  • Topical therapy:
    = ACETIC ACID (mild)
    = Abx +/- topical steroids:
  • Ciprofloxacin 3%
  • Dexamethasone 0.1%
    or Clotrimazole 1%
    ENT referral
  • Microsuction - to allow topical Abx to reach affected tissue
  • Wick insertion = aids delivery of topical therapy
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13
Q

Treatment NOE

A
  • Admission under ENT : potentially with joint input from medical/infectious diseases team
  • Vascular access : for long term therapy (minimum 6 weeks)
  • IV antibiotics: ceftazidime/as per local formulary
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14
Q

Complications

A
  • Pinna cellulitis
  • Chronic otitis externa: prolonged topical antibiotics are a risk factor for fungal overgrowth
  • Myringitis

Necrotising otitis externa:
- Meningitis
-Cranial nerve palsies
- Subdural empyema
- Dural sinus thrombophlebitis (dural sinus occlusive disease)

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