Malignant (necrotising) otitis externa: a serious ear infection explained

Ordinary otitis externa, often called swimmer's ear, is inflammation of the skin of the ear canal. Nottinghamshire primary care guidance defines necrotising (malignant) otitis externa as a potentially life-threatening progressive infection which may spread to cause osteomyelitis, bone infection, of the temporal bone and adjacent structures, often caused by Pseudomonas aeruginosa.

NHS England adds that Pseudomonas aeruginosa is the organism most commonly isolated from the ear discharge, in more than 90% of cases according to its policy document, that it is an uncommon condition, and that it was first reported in the literature in 1838. The word "malignant" has nothing to do with cancer but describes the aggressive behaviour of the infection.

The Bristol pathway says risk factors include older age, diabetes and immunocompromise. NHS England says it is mainly found in the elderly or in diabetics. Nottinghamshire guidance emphasises that diabetic and immunocompromised patients are particularly susceptible to aggressive destruction of cartilage by Pseudomonas aeruginosa.

This is why people with diabetes who develop ear pain that is out of proportion to what is seen, or an ear infection that is not responding to drops, should not wait before mentioning their diabetes to the doctor.

NHS England lists severe ear pain and headaches, exposed bone visible in the ear canal and facial nerve palsy, where the face droops on the side of the affected ear. The Bristol pathway describes the red flags that should prompt discussion with ENT on call.

• Ear pain that is unremitting and disproportionate, particularly overnight.

• Being systemically unwell and/or having a high fever.

• Facial weakness or other cranial nerve involvement, typically on the same side as the ear.

• Granulation tissue or exposed bone on the floor of the ear canal at the bone-cartilage junction.

• Spreading redness or swelling of the outer ear or face.

NHS England says malignant otitis externa can occasionally be complicated by infection of nearby parts of the body, causing parotitis, mastoiditis, jugular vein thrombosis, meningitis and death. It also notes that the aim of treatment is to cure the infection.

These complications are the reason the condition is treated as an emergency in people who are at risk and have worrying symptoms.

NHS England says diagnosis is based upon clinical, microbiological and radiological findings. In practice this means an ENT specialist examining the ear, testing the discharge for the organism, and imaging to look for involvement of the bone at the skull base. The sources used here state the three categories but not the specific tests.

The Bristol pathway notes that ear swabs are rarely helpful in primary care for uncomplicated otitis externa but can be considered if symptoms persist after 14 days of appropriate topical treatment or if a fungal infection is suspected.

NHS England describes the goal as curing the infection. The treatment is taking antibiotics for a long period of time, which may be given through a vein or by mouth, and in some cases surgery may be needed to remove dead or damaged tissue. It adds that stringent diabetes control is part of the mainstay.

Hyperbaric oxygen therapy, in which oxygen is breathed in a pressurised chamber, has been suggested as an additional treatment. NHS England reviewed the evidence in 2018 and concluded there was not enough evidence to routinely commission it, so it is not routinely funded in England.

The sources used here do not give survival or recovery figures. NHS England states that complications can include meningitis and death, which illustrates why early recognition matters. It describes the mainstay of treatment as prolonged antibiotic therapy, so recovery is measured over a long course rather than days.

Your ENT team will explain how long treatment is expected to last and how progress will be checked.

On the NHS, suspected cases are discussed with the on-call ENT team, in line with local pathways such as the Bristol one, which says to discuss with ENT on call if there is suspicion of necrotising otitis externa or severe regional spread of infection likely to require intravenous antibiotics.

Because this is an emergency condition, the usual route is via a GP, NHS 111 or emergency department rather than private referral. Private ENT services may see people for follow-up but suspected cases should not be delayed waiting for an appointment.