Harvey's Garden

Otitis externa

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4 min read

Epidemiology & Risk Factors

  • Water exposure / excess moisture (“swimmer’s ear”).
  • Mechanical trauma (cotton swabs, hearing aids, earplugs).
  • Pathogens:
  • Necrotizing (Malignant) Otitis Externa:
    • Elderly pts with DM (uncontrolled).
    • Immunocompromised pts (e.g., HIV/AIDS, chemotherapy, post-transplant).
    • Primary pathogen: Pseudomonas aeruginosa (>90%).

Clinical Features

  • Acute Otitis Externa (AOE):
    • Otalgia, pruritus, sensation of ear fullness, conductive hearing loss.
    • Otorrhea (purulent or serosanguineous).
    • PE: Marked pain on tragal pressure or pinna traction (hallmark sign).
    • Otoscopy: Erythematous, edematous external auditory canal (EAC) with purulent debris.
    • Tympanic membrane (TM): Mobile on pneumatic otoscopy (critical distinction from AOM); may be obscured by canal edema.
  • Necrotizing (Malignant) Otitis Externa (NOE):
    • Severe, unrelenting, deep-seated otalgia (worse at night, radiates to temporomandibular joint).
    • PE: Granulation tissue at the bony-cartilaginous junction of the EAC floor.
    • Foul-smelling, persistent purulent discharge.
    • Neurologic findings: Cranial neuropathy (most commonly CN VII causing facial droop; less commonly CN IX, X, XI).

Diagnosis

  • Initial / AOE:
    • Clinical diagnosis via otoscopy (tragus tenderness + EAC inflammation).
    • Routine cultures and labs are not indicated for mild-to-moderate uncomplicated AOE.
  • Necrotizing (Malignant) OE:
    • Key Labs: Markedly ↑ ESR and ↑ CRP (useful for monitoring response to therapy); normal/mildly elevated WBC count.
    • Microbiology: Canal exudate/drainage culture to confirm P. aeruginosa and antibiotic sensitivities.
    • Imaging:
      • CT scan of temporal bone with IV contrast (initial): Identifies cortical bone erosion and soft tissue extension.
      • Technetium-99m bone scan: Highly sensitive for osteomyelitis (remains abnormal long after resolution; poor for tracking cure).
      • Gallium-67 scan: Highly sensitive for active inflammation/infection; used to monitor treatment response.
      • MRI: Superior for evaluating soft tissue spread, dural enhancement, and intracranial extension.
    • Biopsy: Biopsy of EAC granulation tissue is indicated if response is poor to rule out squamous cell carcinoma of the EAC.

Differential Diagnostics

  • Acute Otitis Media (AOM):
    • Diff: Middle ear effusion with bulging, hypomobile TM, fever; no pain with tragus/pinna manipulation.
  • Contact Dermatitis of EAC:
    • Diff: Predominant intense pruritus, erythematous and scaling skin, lacks severe otalgia or tenderness with tragal pressure; often triggered by topical neomycin or cosmetics.
  • Otomycosis:
    • Diff: Prominent itching over pain; otoscopy shows white/black fungal hyphae/spores (Aspergillus niger = black dots; Candida = fluffy white debris).
  • Ramsay Hunt Syndrome (Herpes Zoster Oticus):
    • Diff: Severe otalgia accompanied by vesicular lesions in the EAC and concha, combined with peripheral facial nerve palsy (CN VII) and vestibulocochlear symptoms (vertigo, sensorineural hearing loss).
  • Squamous Cell Carcinoma of the Canal:
    • Diff: Chronic ulcerated mass in EAC unresponsive to Abx; confirmed via biopsy.

Management

  • Acute Uncomplicated Otitis Externa:
    1. Aural Toilet: Gentle debridement and cleaning of the EAC (only if TM is verified intact).
    2. First-line: Topical fluoroquinolones (e.g., ciprofloxacin + dexamethasone drops or ofloxacin drops). c
      • Non-ototoxic; safe to use if TM perforation cannot be ruled out.
    3. Alternative: Topical neomycin/polymyxin B/hydrocortisone (contraindicated if TM is perforated or non-visualized due to ototoxicity risk).
    4. Severe Edema: Insert an ear wick to facilitate delivery of topical drops into the canal.
    5. Systemic (oral) Abx: Indicated only if infection extends beyond EAC (e.g., cellulitis of auricle/face) or pt is immunocompromised.
  • Necrotizing (Malignant) Otitis Externa:
    1. First-line / Immediate: Systemic IV antipseudomonal Abx (e.g., IV Ciprofloxacin; alternatives include IV piperacillin-tazobactam, cefepime, or meropenem).
    2. Long-term Therapy: Transition to oral fluoroquinolones once stabilized; require prolonged treatment (6–8 weeks) guided by ESR/CRP normalization and Gallium-67 scans.
    3. Strict Glycemic Control: Critical in diabetic patients.
    4. Surgical Debridement: Reserved for refractory osteomyelitis, extensive soft tissue necrosis, or abscess drainage (not initial first-line).

Complications

  • Periauricular cellulitis.
  • External auditory canal stenosis.
  • TM perforation.
  • Skull base osteomyelitis (clivus involvement).
  • Multiple cranial neuropathies (CN VII, IX, X, XI, XII).
  • Intracranial spread: Meningitis, sigmoid/lateral sinus thrombosis, brain abscess.

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