Overview
Also known as malignant otitis externa, necrotising otitis externa is a potentially life-threatening and progressive infection of the external ear canal which can spread to the temporal bone and other surrounding structures causing osteomyelitis.
It is usually caused by Pseudomonas aeruginosa.
Epidemiology
- Usually seen in:
- People with diabetes – most common
- Elderly patients
- People who are immunocompromised
Risk Factors
- Diabetes mellitus
- Increasing age
- Immunodeficiency
- Any of the risk factors for otitis externa
Presentation
Patients usually have features of otitis externa but have severe and unrelenting ear pain that is out of proportion to clinical findings. Features may be:
- Unrelenting deep ear pain
- Headaches
- Purulent otorrhoea
- Systemically unwell
- Facial nerve palsy
If a patient with immunodeficiency has ear pain/discharge that has not responded to treatment within 72 hours, suspect necrotising otitis externa
Investigations
All patients
- Immediate ENT referral if suspected. Features that suggest necrotising otitis externa are:
- Pain and headaches out of proportion to clinical findings
- Exposed bone in the ear canal
- Facial nerve paralysis
- CT scan with IV contrast:
- May show bony erosion
- MRI of brain and internal auditory canal:
- May be performed alongside a CT with contrast to assess soft tissues
Management
All patients
- Immediate referral to ENT
- 1st-line: ciprofloxacin immediately
- IV antibiotics that cover Pseudomonas aeruginosa are used
- IV or oral routes are given depending on the severity
Complications
- Cranial nerve palsy
- Osteomyelitis of the base of the skull – has a significant mortality rate
Prognosis
- Necrotising otitis externa can be life-threatening
- The mortality rate associated with temporal bone osteomyelitis can be as high as 20%
