Necrotising (Malignant) Otitis Externa

Definition and epidemiology

Necrotising otitis externa is a serious disease in which an infection starting in the ear canal spreads to the soft tissues, the temporal bone and the skull base, causing osteomyelitis. It was first described as temporal bone osteomyelitis in 1959, and the term ‘malignant external otitis’ was established by Chandler (1968) (Stocker and Hempel, 2025). ‘Malignant’ refers not to cancer but to the destructive course of a disease that can progress despite treatment. This entry covers in detail the necrotising form mentioned briefly in the otitis externa entry.

The disease is rare. A university clinic in Munich treated 13 patients between 2009 and 2020; their mean age was 79.9 years and 76.9% were men (Stocker and Hempel, 2025). Mortality in Chandler’s original series was reported as 46% (Handzel and Halperin, 2003). Early diagnosis and prolonged antibiotic treatment have improved outcomes markedly; in a French series of 32 patients, all had a favourable outcome after treatment (Pulcini et al., 2012).

Symptoms and signs

The key symptom is severe, deep earache (otalgia) that is typically worse at night. It comes with offensive, purulent discharge (otorrhoea), and canal oedema and discharge can cause reduced hearing and fullness (Handzel and Halperin, 2003). In the Munich series, every patient had earache and discharge at the first visit (Stocker and Hempel, 2025). Symptoms often begin like an ordinary otitis externa but do not settle with standard drops.

Examination shows granulation tissue at the bony-cartilaginous junction of the canal, usually on its floor, a finding of great diagnostic importance. Spread to the skull base can cause difficulty opening the mouth (trismus), enlarged neck lymph nodes and tenderness over the masseter. The facial nerve is the cranial nerve most often and first affected, and cranial nerve involvement indicates a poor prognosis (Handzel and Halperin, 2003). In the Munich series, 7 of 13 patients (53.8%) developed facial palsy, and one later developed vestibulocochlear and vagal involvement (Stocker and Hempel, 2025). Involvement of the glossopharyngeal, vagus and accessory nerves shows as difficulty swallowing and hoarseness, and intracranial spread can lead to fatal complications such as sigmoid sinus thrombosis (Handzel and Halperin, 2003).

Causes and risk factors

Diabetes is the main risk factor; AIDS, cancer, chemotherapy and other causes of immunosuppression also raise the risk, and the disease occurs mostly in older people (Handzel and Halperin, 2003). In the Munich series, 12 of 13 patients (92.3%) had type 2 diabetes, with a mean HbA1c of 8.35% where known (Stocker and Hempel, 2025). Small-vessel disease and impaired immune responses in diabetes make it easier for infection to progress from the canal skin into bone.

The commonest organism is Pseudomonas aeruginosa (Handzel and Halperin, 2003). In the French series, 30 of 32 patients had proven or suspected P. aeruginosa infection (Pulcini et al., 2012). In the Munich series 76.9% of canal swabs were positive, P. aeruginosa was the commonest isolate and Candida albicans grew in three swabs (Stocker and Hempel, 2025). Fungi such as Aspergillus and Candida can be responsible, particularly with severe immunosuppression; because treatment differs, culture and, where needed, tissue sampling are important. Avoiding factors that damage the canal skin, such as cotton buds and frequent exposure to chlorinated pool water, is advised (Handzel and Halperin, 2003).

Audiological and clinical assessment

The diagnosis rests on clinical findings, laboratory tests, culture, imaging and, where needed, biopsy taken together. Cohen and Friedman (1987) proposed clinical diagnostic criteria for the disease, and many later studies have relied on them. The AAO-HNS guideline on acute otitis externa recommends asking about modifying factors such as diabetes and immunosuppression and reassessing patients who fail to respond within 48-72 hours (Rosenfeld et al., 2014). In an older person with diabetes, persistent night pain and granulation tissue on the canal floor should be treated as necrotising otitis externa until proven otherwise.

• Laboratory tests: the erythrocyte sedimentation rate is usually raised and is used to monitor response; full blood count, glucose and renal function are also checked (Handzel and Halperin, 2003). In the Munich series, CRP was only 0.7-5.9 mg/dl in most patients, so near-normal values do not exclude the diagnosis (Stocker and Hempel, 2025).
• Culture and biopsy: discharge is cultured before antibiotics are started, and biopsy of granulation tissue is needed to exclude cancer of the ear canal (Handzel and Halperin, 2003).
• Computed tomography (CT): shows the site and extent of disease, but bone changes appear late and resolve late, limiting its value for follow-up (Handzel and Halperin, 2003).
• Magnetic resonance imaging (MRI): preferred for assessing soft-tissue spread, bone marrow change and intracranial complications.
• Nuclear medicine: a technetium-99m bone scan shows bone involvement early but stays positive during bone repair, so it is not useful for follow-up. Gallium-67 scintigraphy is sensitive to ongoing infection and is recommended for diagnosis and follow-up (Handzel and Halperin, 2003).
• Audiological assessment: a conductive loss from canal oedema, or a sensorineural component suggesting inner ear involvement, may be found; age-related loss is also common in this group. Probe tests and ear impressions are postponed in the acute phase, and any fall in bone-conduction thresholds is reported to the doctor.

The differential diagnosis includes refractory acute otitis externa, cancer of the ear canal, external auditory canal cholesteatoma and chronic otitis media. The table below summarises the distinction from acute otitis externa.

Treatment and audiological rehabilitation

Necrotising otitis externa needs urgent referral; treatment is planned jointly by ENT and infectious diseases specialists, and the choice and duration of medicines rest with the doctor. The mainstay is systemic antibiotics active against P. aeruginosa, adjusted to culture results. Tight glucose control, correction of immunosuppression where possible, and regular canal cleaning with removal of dead tissue are integral to treatment. Treatment lasts at least four weeks and is tailored to night pain, examination findings, sedimentation rate and imaging (Handzel and Halperin, 2003).

In the French series, after a standard protocol was adopted the mean antibiotic course fell from 9.4 to 5.8 weeks and hospital stay from 18.2 to 11.6 days, with a favourable outcome in every patient. In the authors’ literature review, combination therapy was associated with better outcomes than a single agent (97% versus 83%), and for susceptible P. aeruginosa they recommended three weeks of high-dose combination therapy followed by three weeks of a single agent (Pulcini et al., 2012). Fungal cases need antifungal treatment.

Surgery is reserved for bone sequestra and abscesses, and extensive surgery has been said to risk exposing healthy bone to infection. Hyperbaric oxygen can be used as an adjunct, but the evidence comes from uncontrolled studies (Handzel and Halperin, 2003). Practice varies between centres: in the Munich series 11 of 13 patients (84.6%) had surgery, most of them a mastoidectomy (Stocker and Hempel, 2025).

In a hearing aid user, the aid is left out of the affected ear on medical advice until the infection has resolved, and the mould and aid are cleaned and disinfected. After recovery, hearing is reassessed and the fit of the mould is checked. If canal narrowing or persistent discharge remains, an open fitting or bone conduction implants can be considered with the doctor. Patients with facial palsy need eye protection and referral for physiotherapy.

Impact on quality of life and advice

The disease mostly affects older people with several long-term conditions. Prolonged antibiotic treatment and hospital admission restrict daily life considerably; the mean hospital stay in the Munich series was 26.2 days (Stocker and Hempel, 2025). Facial palsy affects speech, eating and eye closure, and lower cranial nerve involvement can cause swallowing difficulty and a risk of aspiration. Nutrition, eye care and physiotherapy support should therefore be planned during treatment.

Practical advice: if you have diabetes, monitor your blood glucose regularly and do not dismiss earache as a minor problem. Do not put cotton buds or other objects in your ear, and do not syringe it yourself. If night pain returns or discharge recurs after treatment has ended, seek help at once, as the disease can relapse. If you use a hearing aid, clean the aid and mould every day, and check with your doctor before wearing it when the ear is painful or discharging. Making sure family members know the warning signs helps with early presentation.