Otitis Externa Flashcards
What is otitis externa?
Otitis externa is inflammation of the skin in the external ear canal.
Oto- refers to ear, -itis refers to inflammation, and externa refers to the external ear canal. The infection can be localised or diffuse. It can spread to the external ear (pinna). It can be acute (less than three weeks) or chronic (more than three weeks).
What are the risk factors for otitis externa?
- External auditory canal obstruction
- High environmental humidity
- Warmer environmental temperatures
- Swimming
- Local trauma
- Allergy
- Skin disease
- Diabetes
- Immunocompromised state
- Prolonged used of topical antibacterial agents
What can cause otitis externa?
The inflammation in otitis externa may be caused by:
- Bacterial infection
- Fungal infection (e.g. aspergillus or candida)
- Eczema
- Seborrhoeic dermatitis
- Contact dermatitis
What bacteria commonly cause otitis externa?
The two most common bacterial causes of otitis externa are:
- Pseudomonas aeruginosa
- Staphylococcus aureus
Briefly describe Pseudomonas aeruginosa
It is a gram-negative aerobic rod-shaped bacteria.
It likes to grow in moist, oxygenated environments. Other than causing otitis externa, it can colonise the lungs in patients with cystic fibrosis, significantly increasing their morbidity and mortality.
It is naturally resistant to many antibiotics, making it very difficult to treat in children with cystic fibrosis. It can be treated with aminoglycosides (e.g. gentamicin) or quinolones (e.g. ciprofloxacin).
What are the clinical features of otitis externa?
The typical symptoms of otitis externa are:
- Ear pain
- Discharge
- Itchiness
- Conductive hearing loss (if the ear becomes blocked)
How does otitis externa present on otoscopy?
Examination can show:
- Erythema and swelling in the ear canal
- Tenderness of the ear canal
- Pus or discharge in the ear canal
- Lymphadenopathy (swollen lymph nodes) in the neck or around the ear
The tympanic membrane may be obstructed by wax or discharge. It may be red if the otitis externa extends to the tympanic membrane. If it is ruptured, the discharge in the ear canal might be from otitis media rather than otitis externa.
How is otitis externa diagnosed?
The diagnosis can be made clinically with an examination of the ear canal (otoscopy).
An ear swab can be used to identify the causative organism but is not usually required.
Briefly describe the management of mild otitis externa
Mild otitis externa may be treated with acetic acid 2% (available over the counter as EarCalm). Acetic acid has an antifungal and antibacterial effect. This can also be used prophylactically before and after swimming in patients that are prone to otitis externa.
Briefly describe the management of moderate otitis externa
Moderate otitis externa is usually treated with a topical antibiotic and steroid, for example:
- Neomycin, dexamethasone and acetic acid (e.g., Otomize spray)
- Neomycin and betamethasone
- Gentamicin and hydrocortisone
- Ciprofloxacin and dexamethasone
What is the risk of topical aminoglycosides in the ear?
Aminoglycosides (e.g., gentamicin and neomycin) are potentially ototoxic, rarely causing hearing loss if they get past the tympanic membrane. Therefore, it is essential to exclude a perforated tympanic membrane before using topical aminoglycosides in the ear. This can be difficult if the patient has discharge, swelling or wax blocking the ear canal. Patients with a blocked ear canal may need to be seen by ENT to microsuction the debris from the canal and visualise the tympanic membrane. They will also require a referral if the canal is so blocked or swollen that topical treatments cannot reach the site of infection.
Briefly describe the management of severe otitis externa
Patients with severe or systemic symptoms may need oral antibiotics (e.g., flucloxacillin or clarithromycin) or discussion with ENT for admission and IV antibiotics.
What is the role of an ear wick in treating otitis externa?
An ear wick may be used if the canal is very swollen, and treatment with ear drops or sprays will be difficult. An ear wick is made of sponge or gauze. They contain topical treatment for otitis externa (e.g., antibiotics and steroids). Wicks are inserted into the ear canal and left there for a period of time (e.g., 48 hours). As the swelling and inflammation settle, the ear wick can be removed, and treatment can continue with drops or sprays.
Briefly describe the management of fungal otitis externa
Fungal infections can be treated with clotrimazole ear drops.
What is malignant otitis externa?
Malignant otitis externa is a severe and potentially life-threatening form of otitis externa. The infection spreads to the bones surrounding the ear canal and skull. It progresses to osteomyelitis of the temporal bone of the skull.
