Malignant (Necrotizing) Otitis Externa

How it develops

It usually begins as a typical outer ear infection (swimmer's ear). In someone with diabetes or reduced immunity, the bacteria spread through natural gaps in the cartilage of the ear canal into the soft tissue and then the temporal bone and skull base. The infection causes bone inflammation (osteomyelitis) and can damage nerves that run through the skull base.

Small blood vessel disease in diabetes reduces blood flow to tissues and weakens immune defenses, which explains why diabetes is the main risk factor. Ear irrigation to remove wax can sometimes trigger it in susceptible people.

Risk factors

• type 2 diabetes or type 1 diabetes, especially in older adults, present in most cases
• older age
• HIV, chemotherapy, organ transplant medicines and other causes of immune suppression
• kidney failure
• ear canal trauma or irrigation

Symptoms

• severe, constant ear pain, deeper and worse than ordinary swimmer's ear, often worse at night
• pain when chewing, from involvement of the jaw joint area
• persistent discharge, which may be foul-smelling
• headache on the affected side
• hearing loss and ear fullness
• granulation tissue (red, raw tissue) on the floor of the ear canal
• fever is often absent

Nerve involvement

As infection spreads, cranial nerves can be affected:

• facial nerve: weakness of one side of the face (facial nerve palsy), the most common nerve complication
• nerves to the throat: hoarseness and difficulty swallowing
• other nerves: shoulder weakness, tongue weakness, double vision

Diagnosis

• ear examination: swelling, discharge and granulation tissue
• swab or tissue culture to identify the organism and its antibiotic sensitivities, ideally before antibiotics
• blood tests: inflammatory markers (ESR and CRP), often very raised and used to monitor response, plus blood sugar and HbA1c
• CT scan: shows bone erosion
• MRI: shows soft tissue spread and skull base involvement
• nuclear scans in some centers to show infection activity and monitor recovery
• biopsy to rule out cancer of the ear canal, which can look similar

Treatment

• Long-course antibiotics: usually anti-pseudomonal antibiotics such as ciprofloxacin, ceftazidime or piperacillin-tazobactam, often starting IV. Treatment typically lasts at least 6 weeks and often 3 months or longer, guided by symptoms, inflammatory markers and imaging.
• Antifungal treatment if fungi are the cause.
• Tight blood sugar control.
• Ear cleaning by an ENT specialist.
• Pain control.
• Surgery to remove dead tissue or bone, or for abscesses, in selected cases.
• Hyperbaric oxygen occasionally as an add-on.

Antibiotic-resistant Pseudomonas is increasing, making culture results important.

Complications

• facial nerve palsy, which may be permanent
• other cranial nerve palsies affecting swallowing and speech
• spread to the jaw joint and neck, or to the mastoid bone (mastoiditis)
• venous sinus thrombosis
• meningitis and brain abscess
• death in advanced, untreated cases

Outlook

With early diagnosis and long antibiotic treatment, most people recover. The outlook is worse when cranial nerves are involved or treatment is delayed. Relapse can occur months later, so follow-up continues after treatment ends.

Frequently asked questions

What is malignant otitis externa?

Malignant otitis externa is a serious infection that starts in the outer ear canal and spreads into the bone at the base of the skull. It is called malignant because of how aggressively it spreads, not because it is cancer. It mainly affects older people with diabetes.

What are the symptoms of malignant otitis externa?

Symptoms include severe, persistent ear pain that is often worse at night, ear discharge, pain on chewing, headache and hearing loss. In advanced cases, facial weakness, hoarseness or difficulty swallowing can occur as nerves are affected.

Why does diabetes increase the risk?

Diabetes damages small blood vessels and weakens immune defenses, so infections in the ear canal can spread into deeper tissues and bone more easily. Most people with malignant otitis externa have diabetes, often older adults.

How is malignant otitis externa treated?

Treatment involves long courses of antibiotics, usually against Pseudomonas, often starting IV and continuing for 6 weeks to several months. Blood sugar control, regular ear cleaning by an ENT specialist and, sometimes, surgery are also part of treatment.

Is malignant otitis externa cancer?

No. Despite its name, it is an infection, not cancer. The term "malignant" describes its aggressive, spreading nature. It is also called necrotizing otitis externa. A biopsy is sometimes taken to make sure a cancer of the ear canal is not present.