Necrotising (malignant) otitis externa
A severe ear canal infection that spreads into the skull base bone, mainly in older people with diabetes. Not cancer, but it can kill without long treatment.
What it is
An aggressive infection of the external ear canal that spreads to the temporal bone and skull base as osteomyelitis. «Malignant» refers to its course, not to cancer; it can involve cranial nerves, the venous sinuses and the brain.
Who gets it
Rare. It occurs mostly in older adults with diabetes mellitus, and in people with HIV, chemotherapy or other immunosuppression. With the growing number of people with diabetes in Colombia, it should be suspected in any diabetic patient with a severe ear infection that does not improve.
Causes
- Pseudomonas aeruginosa in most cases
- Less often Staphylococcus aureus (including MRSA) and other gram-negative bacteria
- Fungi (Aspergillus, Candida), especially in immunosuppressed people
- Spread from the canal floor through natural clefts in the cartilage to the skull base
Risk factors
- Diabetes mellitus, especially poorly controlled
- Older age
- Immunosuppression: HIV, chemotherapy, transplant, corticosteroids
- Ear canal trauma, such as irrigation or instrumentation
- Radiotherapy to the head and neck
Classification
- Limited to the ear canal and adjacent soft tissue
- Skull base osteomyelitis
- With cranial nerve palsy (facial nerve first, then glossopharyngeal, vagus, accessory and hypoglossal)
- With intracranial spread: venous sinus thrombosis, meningitis, abscess
Symptoms and signs
- Severe, persistent ear pain, often worse at night and out of proportion to the findings
- Purulent ear discharge
- Granulation tissue on the floor of the canal at the bony-cartilaginous junction
- Headache and pain at the temporomandibular joint
- Hearing loss and fullness
- Fever is often absent
Diagnosis
- Clinical
- Suspected from severe otalgia and granulation tissue in the canal floor in a diabetic or immunosuppressed person. Examination includes the cranial nerves, especially the facial nerve.
- Tests
- Raised ESR and CRP (useful to follow response); blood glucose and HbA1c; culture of the discharge or deep tissue before antibiotics when possible; biopsy of granulation tissue to exclude squamous cell carcinoma.
- Imaging
- CT of the temporal bone shows bone erosion; MRI shows soft tissue and intracranial spread. Technetium bone scan is sensitive early; gallium or labelled white cell scans help follow activity.
Differential diagnosis
- Severe acute otitis externa
- Squamous cell carcinoma of the ear canal
- Cholesteatoma of the external canal
- Mastoiditis
- Granulomatous diseases (tuberculosis, granulomatosis with polyangiitis)
Treatment
- Acute
- Hospital admission, strict glycaemic control and referral to otolaryngology and infectious diseases; samples for culture are taken before antibiotics when possible.
- Medical
- Prolonged systemic antipseudomonal antibiotics (a fluoroquinolone such as ciprofloxacin, or an antipseudomonal beta-lactam), guided by culture, for at least six weeks; antifungals for fungal disease.
- Medical
- Regular aural toilet and topical antibiotic drops as an adjunct.
- Surgical
- Surgical debridement of necrotic bone or abscess drainage in selected cases; biopsy to exclude malignancy.
- Procedure
- Hyperbaric oxygen therapy is sometimes used as an adjunct in refractory disease.
- Follow-up
- Follow-up with symptoms, ESR or CRP and functional imaging to decide when to stop antibiotics; relapse can occur months later.
Complications
- Facial palsy and lower cranial nerve palsies
- Sigmoid or lateral sinus thrombosis
- Meningitis and brain abscess
- Hearing loss
- Death, especially with multiple cranial neuropathies or intracranial spread
Prognosis
With early diagnosis and prolonged antibiotics, most patients are cured, and mortality has fallen a great deal. Cranial nerve palsies, intracranial spread and fungal infection worsen the outlook; relapse is possible.
Test yourself
Think of the answer, then tap the question to see it.
Which organism causes most cases of necrotising otitis externa?
Pseudomonas aeruginosa.
What is the typical patient?
An older adult with diabetes mellitus, or an immunosuppressed person, with severe otalgia and granulation tissue in the ear canal.
Which cranial nerve is affected first, most often?
The facial nerve (VII), at the stylomastoid foramen.
Why is a biopsy of the granulation tissue taken?
To exclude squamous cell carcinoma of the ear canal, which can look similar.
Which laboratory markers are used to follow treatment response?
ESR and CRP.
Why it happens
In ENT
- External ear problems: wax, otomycosis, furuncle, perichondritis, exostoses and keratosis obturans
- Imaging in ENT: which study for which question
Connections
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Necrotizing (Malignant) Otitis Externa (StatPearls (NCBI Bookshelf), 2023).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.