Necrotizing Otitis Externa

Aka: Necrotizing Otitis Externa, Malignant External Otitis, Malignant Otitis Externa, Osteitis of the Skull Base, Malignant Otitis Externa due to Pseudomonas aeruginosa, Osteomyelitis of Temporal Bone

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II. Risk Factors

  1. Diabetes Mellitus
  2. Elderly
  3. Immunocompromised state (e.g. Chemotherapy)
  4. Human Immunodeficiency Virus (HIV, AIDS)

III. Pathophysiology

  1. Necrotizing infection of the soft tissue of the external auditory canal
    1. Pseudomonas aeruginosa is most common causative organism (accounts for 95% of cases)
    2. Staphylococcus aureus accounts for the remaining cases
  2. Complication of Otitis Externa
    1. Infection extends into ear canal cartilage
    2. Passes to Temporal Bone via Santorini's Fissures
  3. Severe extension of external Otitis Media
    1. Mastoiditis
    2. Osteitis of Temporal Bone

IV. Symptoms: Severe Otitis Externa

  1. Severe, unrelenting Ear Pain and Headache
  2. Persistent discharge
  3. Hearing Loss
  4. Does not respond to Topical Medications
  5. Commonly associated with Diabetes Mellitus
  6. Fever is typically absent

V. Signs

  1. Purulent Otorrhea
  2. Tender and swollen external auditory canal
  3. Tympanic Membrane spared
  4. Granulation tissue in posterior and inferior canal and possible exposed bone
    1. Pathognomonic for necrotizing otitis
    2. Occurs at bone-cartilage junction
  5. Extra-auricular findings
    1. Cervical Lymphadenopathy
    2. Trismus (TMJ involvement)
    3. Facial Nerve Palsy or paralysis (Bell's Palsy)
      1. Associated with poor prognosis

VI. Labs

  1. Complete Blood Count
  2. Culture ear discharge
  3. Erythrocyte Sedimentation Rate (ESR) markedly elevated
  4. Serum Glucose
  5. Serum Creatinine
  6. Histology of granulation tissue excised from canal

VII. Imaging

  1. CT Scan or MRI of ear
    1. CT findings lag behind clinical findings (but best for bony involvement evaluation)
  2. Nuclear imaging
    1. Technetium Tc 99m medronate methylene bone scanning
    2. Gallium citrate Ga 67 scintography
      1. High sensitivity for current infection
      2. Useful for follow-up for resolution

VIII. Management

  1. Admit to hospital
  2. Anti-pseudomonal antibiotics
    1. Intravenous Antibiotic options
      1. Ciprofloxacin 400 mg IV every 8 hours (preferred)
      2. Imipenem 0.5 mg IV q6 hours
      3. Meropenem 1.0 grams IV q8 hours
      4. Ceftazidime 2.0 grams IV q8 hours
      5. Cefepime 2.0 grams IV q12 hours
      6. Piperacillin-Tazobactam 4.5 g IV every 6-8 hours AND Aminoglycoside (Tobramycin or Gentamicin)
    2. Oral antibiotic options (after initial IV course or for mild, early involvement)
      1. Ciprofloxacin 750 mg PO q12 hours
    3. Course
      1. Start with IV antibiotics
      2. Continue antibiotics for 4-6 weeks if bone involvement (shorter courses if not)
    4. Alternative course in a well appearing reliable patient
      1. Ceftazidime can be given IM and could be used with follow-up within 8-12 hours
      2. Hospital admission with IV antibiotics is safest course
  3. Consult Otolaryngology (ENT)
    1. Surgical Debridement may be required
  4. Clean ear canals meticulously on a daily basis
    1. Clean and debride canal
    2. Apply topical antibiotic agents
  5. Other modalities to consider
    1. Hyperbaric oxygen chamber
    2. Davis (1992) Arch Otolaryngol Head Neck Surg 118:89 [PubMed]

IX. Complications

  1. Skull Osteomyelitis
  2. Cranial Nerve palsy
  3. Septic venous sinus thrombosis
  4. Meningitis
  5. Cerebral Abscess

X. Prognosis

  1. Mortality reportedly as high as 20 to 53%

XI. Prevention

  1. Avoid use of cotton swabs in ear and other canal Trauma
  2. Use caution when irrigating ear of high risk patients
  3. Treat Eczema of ear canal and other pruritic dermatitis

XII. References

  1. (2019) Sanford Guide, accessed on IOS, 11/28/2019
  2. Khoujah (2013) Crit Decis Emerg Med 27(4): 12-21
  3. Bath (1998) J Laryngol Otol 112:274-7 [PubMed]
  4. Handzel (2003) Am Fam Physician 68(2):309-12 [PubMed]
  5. Sander (2001) Am Fam Physician 63:927-42 [PubMed]
  6. Selesnick (1994) Am J Otol 15:408-12 [PubMed]

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