malignant otitis externa

Last edited 04/2021 and last reviewed 07/2021

Malignant otitis externa is otitis externa which has spread to cause osteomyelitis of the skull base

• all tissues (soft tissue, cartilage, and bone) area affected as osteomyelitis spreads along the skull base

It is due to Pseudomonas aeruginosa and anaerobes causing a mound of tissue in the external canal

• P aeruginosa is isolated from exudate in the ear canal in more than 90% of cases (1)
  
  
• a facial nerve palsy occurs in 50% of patients with this condition, and nerves IX to XII may also be involved
  • initial clinical features are those of the initiating acute otitis externa, but untreated disease develops into a skull base osteomyelitis that can invade soft tissue, the middle ear, inner ear, or brain
  • facial nerve paralysis may be an early sign, with the glossopharyngeal and spinal accessory nerves less frequently involved (1)
    
    
• affects immunocompromised patients, especially elderly diabetics
  • lavage of the ear canal for cerumen impaction in elderly or diabetic patients has been implicated as a contributing factor in malignant otitis externa (1)
    
    
• may be life threatening
  
  
• clinical diagnosis of necrotizing otitis externa can be confirmed with a raised CRP plus an abnormal computed tomography or magnetic resonance imaging
  scan
  
  
• treatment includes surgical debridement and systemic antibiotics adequate to cover pseudomonal and staphylococcal infection, including methicillin-
  resistant S aureus
  
  
• biopsy may be necessary to detect neoplasia if the diagnosis of malignant otitis externa is uncertain or response to therapy is incomplete (1)
  
  
• if you suspect malignant otitis externa arrange an urgent (same day) ear, nose, and throat (ENT) review. A computed tomography imaging
  scan is typically required to confirm the diagnosis (2)

Reference:

• Rosenfeld RM, Schwartz SR, Cannon CR, etal. Clinical practice guideline: acute otitis externa.Otolaryngol Head Neck Surg2014;150(Suppl):S1-24.doi: 10.1177/0194599813517083 pmid: 24491310
• Barry V et al. 10-Minute Consultation - Otitis externa. BMJ2021;372:n714http://dx.doi.org/10.1136/bmj.n714