Necrotizing Otitis Externa

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

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II. Epidemiology

  1. Incidence: 1.1 in 100,000

III. Risk Factors

  1. No predisposing factors (other than Otitis Externa) in 20% of cases
  2. Water exposure
    1. Associated with the initial Otitis Externa risk
  3. Diabetes Mellitus (90% of cases)
    1. Microangiopathy, impaired Wound Healing, increased cerumen pH allow for Bacterial growth
  4. Elderly
    1. Risk increases with age (very rare in children)
    2. Elderly are at higher risk of complications including higher mortality
  5. Immunocompromised state
    1. Chemotherapy
    2. Hematologic Malignancy
    3. Status post organ transplant
    4. Chronic Kidney Disease
    5. Human Immunodeficiency Virus (HIV, AIDS)

IV. Causes

  1. Bacteria
    1. See Bacterial Otitis Externa
    2. Pseudomonas Aeruginosa (50-90% of cases)
    3. Proteus
    4. Klebsiella
    5. Staphylococcus (including MRSA)
  2. Fungi (esp. male, Diabetes Mellitus)
    1. See Fungal Otitis Externa
    2. Aspergillus
    3. Candida

V. Pathophysiology

  1. Triad allows for Malignant Otitis Externa
    1. Epidermal disruption
    2. Immunocompromised state
    3. Otitis Externa infection
  2. Necrotizing infection of the soft tissue of the external auditory canal
    1. Infection invades Temporal Bone and skull base
    2. Pseudomonas Aeruginosa is most common causative organism (accounts for 95% of cases)
    3. Staphylococcus Aureus accounts for the remaining cases
  3. Skull Base Osteomyelitis is a complication of Otitis Externa
    1. Infection extends into ear canal cartilage and ultimately into Temporal Bone
    2. Temporal Bone surrounds the inner two thirds of the ear canal (outer third is cartilage)
    3. Fissures of santorini in the cartilage may allow Otitis Externa to spread to deeper structures
  4. Severe extension of external Otitis Media
    1. Mastoiditis
    2. Osteitis of Temporal Bone

VI. 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

VII. 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. Parotitis
    3. TMJ Involvement
      1. Trismus
      2. Preauricular tenderness
      3. Pain worse with chewing
    4. Facial Nerve Palsy or paralysis (Bell's Palsy)
      1. Facial Nerve Paralysis is most common Cranial Nerve Involvement (20% of malignant otitis cases)
      2. Suggests infection an inflammation at the Temporal Bone's stylomastoid foramen
    5. Other Cranial Nerves
      1. Other Cranial Nerves may be affected with infection of the skull base and jugular foramen
      2. Cranial Nerve Involvement indicates significant progression and associated with increased morbidity and mortality
  6. Intracranial spread (neurologic findings specific to involvement)
    1. Intracranial Abscess
    2. Otogenic Meningitis
    3. Jugular vein Thrombophlebitis
    4. Cerebral Venous Sinus Thrombosis

VIII. Labs

  1. Complete Blood Count
    1. Often normal in Malignant Otitis Externa
  2. Chemistry panel
    1. Serum Glucose
    2. Serum Creatinine
  3. 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
  4. C-Reactive Protein (CRP) and Erythrocyte Sedimentation Rate (ESR)
    1. Often markedly elevated and may be used to track progression
    2. May be unreliable in Immunocompromised patients
    3. C-Reactive Protein (CRP) >10 mg/L (LR+ 8)
    4. Erythrocyte Sedimentation Rate (ESR) >26 mm/h (LR+ 10)
      1. Elevated in nearly 70% of patients (mean 65 mm/h)

IX. Imaging

  1. High Resolution CT Scan of Temporal Bone (and consider CT Brain with contrast)
    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
      1. Test Sensitivity for bony erosions 48%
      2. Test Sensitivity for early findings (canal thickening, fat stranding, contrast enhancement): 95%
    3. CT may also demonstrate abscess formation
  2. Ear MRI with contrast
    1. MRI identifies soft tissue changes and earlier findings (e.g. retrocondylar fat pad, Medullary bone, dura involvement)
    2. Identifies changes in medial skull base and Medullary bone spaces
  3. CT or MR Venogram
    1. Consider for evaluation of dural venous sinus thrombosis (NOE complication)
  4. 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

X. Differential Diagnosis

  1. See Otalgia
  2. Otitis Media
  3. Otitis Externa
  4. Mastoiditis
  5. Malignancy
  6. Cholesteatoma

XI. 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)

XII. Precautions

  1. Typical patient is an elderly, diabetic man with 1-2 weeks of progressive Ear Pain
  2. Malignant Otitis Externa is an easily missed diagnosis early in course
    1. Difficult to distinguish from Acute Otitis Externa
    2. Delayed diagnosis is associated with increased morbidity and mortality

XIII. Management

  1. Admit most patients to hospital
    1. Cranial Nerve Involvement
    2. Septic thrombosis
    3. Cerebral Venous Sinus Thrombosis
    4. Intracranial Abscess
    5. Meningitis
    6. Comorbid Diabetes Mellitus (for optimal Glucose control)
  2. Consult Otolaryngology (ENT) early
    1. Surgical Debridement may rarely be required
    2. Close follow-up with ENT is also needed for the first year (high Antibiotic failure and recurrence rate)
  3. Anti-Pseudomonal Antibiotics
    1. Pseudomonas is the most causative Bacteria (esp. in Diabetes Mellitus)
    2. Intravenous Antibiotic options (adult dosing is listed)
      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
        1. Imipenem is preferred in children
      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. MRSA is also more common in non-diabetic patients
      3. MRSA is associated with a worse prognosis
    4. Antifungal (e.g. Voriconazole, Liposomal Amphotericin B) Indications
      1. Consider empirically (or after culture) in HIV Infection, Diabetes Mellitus or transplant history
      2. Fungi have increased morbidity/mortality, delayed diagnosis, extensive spread, Cranial Nerve Involvement
      3. Voriconazole is preferred
      4. Cover Aspergillus and candida
      5. Consult infectious disease
    5. Oral Antibiotic options (after initial IV course or for mild, early involvement)
      1. Ciprofloxacin 750 mg orally every 12 hours
    6. Course
      1. Start with IV Antibiotics
      2. Continue Antibiotics for 6 to 8 weeks if bone involvement (shorter courses if not)
    7. 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. Topicals do not add value in NOE once systemic Antibiotics are initiated
      2. May alter culture results and not needed in aggressive intravenous Antibiotic management
      3. 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]

XIV. 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

XV. Prognosis

  1. Untreated mortality reportedly as high as 20 to 53%
  2. One year mortality: 2-4%
  3. Treatment failure 22%
  4. Recurrence within 1 year: 7%

XVI. 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

XVII. References

  1. (2019) Sanford Guide, accessed on IOS, 11/28/2019
  2. Bardakos, Raj and Mehta (2026) Crit Dec Emerg Med 40(2): 4-12
  3. Khoujah (2013) Crit Dec Emerg Med 27(4): 12-21
  4. Werner and Long (2023) EM:Rap, accessed 7/2/2023
  5. Bath (1998) J Laryngol Otol 112:274-7 [PubMed]
  6. Handzel (2003) Am Fam Physician 68(2):309-12 [PubMed]
  7. Sander (2001) Am Fam Physician 63:927-42 [PubMed]
  8. Selesnick (1994) Am J Otol 15:408-12 [PubMed]
  9. Takata (2023) Clin Otolaryngol 48(3): 381-94 [PubMed]
  10. Vaca (2024) Eur Arch Otorhinolaryngol 281(2): 737-42 [PubMed]

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