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. Water exposure
    1. Associated with the initial Otitis Externa risk
  2. Diabetes Mellitus (90% of cases)
    1. Microangiopathy, impaired Wound Healing, increased pH allowing for Bacterial growth
  3. Elderly
    1. Risk increases with age (very rare in children)
    2. Elderly are at higher risk of complications including higher mortality
  4. Immunocompromised state
    1. Chemotherapy
    2. Status post organ transplant
    3. 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
    1. Often progressing over 1 to 2 weeks
    2. Contrast with typical Otitis Externa in which symptoms are more mild
  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 Temporal 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 (obtain in all cases of suspected Malignant Otitis Externa)
    1. Bacterial cultures
    2. Fungal Cultures
    3. Histology of granulation tissue excised from canal
  3. C-Reactive Protein and Erythrocyte Sedimentation Rate (ESR) often markedly elevated
  4. Serum Glucose
  5. Serum Creatinine

VII. Imaging

  1. CT Scan of Temporal Bone
    1. CT is best for bony involvement (e.g. erosions) evaluation and more readily available than other imaging
    2. CT findings lag behind clinical findings and may miss early cases
    3. CT may also demonstrate abscess formation
  2. Ear MRI
    1. MRI identifies soft tissue changes and earlier findings (e.g. retrocondylar fat pad involvement)
    2. Identifies changes in medial skull base and Medullary bone spaces
  3. 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. Staging

  1. Stage 1
    1. Severe local Otalgia with granulation tissue
  2. Stage 2
    1. Limited skull base Osteomyelitis
    2. Facial Nerve Palsy
  3. Stage 3
    1. Severe, extensive temporal and skull base Osteomyelitis with bony erosions
    2. Multiple Cranial Nerve Involvement (CN 7, CN 9, CN 10, CN 11)

IX. Management

  1. Admit to hospital
  2. Consult Otolaryngology (ENT) early
    1. Surgical Debridement may rarely be required
  3. Anti-pseudomonal Antibiotics
    1. Pseudomonas is the most causative Bacteria (esp. in Diabetes Mellitus)
    2. Intravenous Antibiotic options
      1. Ciprofloxacin 400 mg IV every 8 hours (preferred)
        1. Combine with beta-lactam broad coverage (agents below) in septic patients
      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)
    3. Other coverage to consider
      1. MRSA coverage (e.g. Vancomycin) in those with abscess or MRSA history
      2. Antifungals (e.g. Voriconazole, Liposomal Amphotericin B)
        1. Consider empirically (or after culture) in HIV Infection or transplant history
        2. Cover Aspergillus and candida
        3. Consult infectious disease
    4. Oral Antibiotic options (after initial IV course or for mild, early involvement)
      1. Ciprofloxacin 750 mg PO q12 hours
    5. Course
      1. Start with IV Antibiotics
      2. Continue Antibiotics for 6 to 8 weeks if bone involvement (shorter courses if not)
    6. 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
  4. Clean ear canals meticulously on a daily basis
    1. Clean and debride canal
    2. Topical Antibiotic agent use is controversial
      1. May alter culture results and not needed in aggressive intravenous Antibiotic management
      2. However, in borderline cases, where diagnosis is initially unclear, may continue during evaluation
  5. Other modalities to consider
    1. Hyperbaric oxygen chamber
      1. May offer benefit, but no strong evidence to support use
      2. Byun (2020) World J Otorhinolaryngol Head Neck Surg 7(4):296-302 +PMID: 34632343 [PubMed]
      3. Davis (1992) Arch Otolaryngol Head Neck Surg 118:89 [PubMed]

X. Complications

  1. Skull Osteomyelitis
  2. Cranial Nerve palsy
    1. Facial Nerve Palsy (CN 7) is most common
    2. With spread of infection toward jugular foramen at skull base, CN 9, CN 10 and CN 11 may become involved
  3. Septic Cerebral Venous Sinus Thrombosis
  4. Meningitis
  5. Cerebral Abscess

XI. Prognosis

  1. Untreated mortality reportedly as high as 20 to 53%

XII. 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

XIII. References

  1. (2019) Sanford Guide, accessed on IOS, 11/28/2019
  2. Khoujah (2013) Crit Decis Emerg Med 27(4): 12-21
  3. Werner and Long (2023) EM:Rap, accessed 7/2/2023
  4. Bath (1998) J Laryngol Otol 112:274-7 [PubMed]
  5. Handzel (2003) Am Fam Physician 68(2):309-12 [PubMed]
  6. Sander (2001) Am Fam Physician 63:927-42 [PubMed]
  7. Selesnick (1994) Am J Otol 15:408-12 [PubMed]

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