Otitis Externa

Question 1

What is otitis externa?

Answer 1

Inflammation of external auditory canal that can be acute or chronic.

=> very common presentation in primary care

=> affects 10% of people with increased risk after first episode

Question 2

What causes otitis externa?

Answer 2

1. Infection

=> Bacterial i.e. staph. aureus, pseudomonas aeruginosa

=> Fungal

2. Seborrheic dermatitis
3. Contact dermatitis (irritant or allergic)

Question 3

What are the risk factors for otitis externa?

Answer 3

Swimming

Warm/humid climates

Underlying skin conditions e.g. eczema

Immunosuppression e.g. diabetes

Trauma e.g. excessive cleaning or scratching

Hearing aids that reduce ventilation or introduce infection into the canal

Question 4

What are the signs and symptoms of otitis externa?

Answer 4

=> ear pain especially on moving pinna/tragus

=> itch

=> purulent discharge

=> hearing loss

=> external auditory swelling - tympanic membrane may not always be visible

=> check for tympanic membrane perforation = otitis externa secondary to otitis media

Signs:

=> otoscopy shows erythematous, swollen or eczematous canal

Question 5

What are the complications of otitis externa?

Answer 5

1. Peri-auricular cellulitis
2. Necrotising otitis externa

=> check if pain is out of proportion with exam findings ; almost always unilateral

=> hx of diabetes / failure to respond to antibiotics = necrotising otitis externa

=> non-neoplastic infection that spreads to the bone resulting in osteomyelitis of the lateral skull base

=> it can cause lower cranial nerve palsies

Question 6

What are the investigations for otitis externa?

Answer 6

Swab the external ear canal for microscopy culture & specificity

Urgent CT scan if necrotising otitis externa suspected (unilateral, severe ear pain, elderly and/or immunocompromised i.e. diabetes)

Question 7

How is otitis externa treated?

Answer 7

1. Topical antibiotic or combined topical antibiotic with a steroid
   * if tympanic membrane is perforated ahminoglycosides not used
2. If canal debris present = removal by micro suction
3. If canal is swollen then insert pope wick = helps antibiotic come in contact with the canal wall & helps stents open a severely oedematous ear canal
   * pope wick = small thin sponge that expands in the ear canal when wet
4. Admit for diabetic control, IV antibiotics and regular aural toilet (micro suction) if suspected necrotising otitial externa
   * If patient fails to respond to topical antibiotics = refer to ENT

Question 8

What are the 2nd line treatment options for otitis externa?

Answer 8

1. Consider contact dermatitis secondary to neomycin
2. Oral antibiotics (flucloxacillin) if infection is spreading
3. Taking a swab inside the ear canal
4. Empirical use of an anti fungal agent

Question 9

What is necrotising otitis externa aka malignant otitis externa?

What causes it?

Answer 9

=> Uncommon type of otitis externa found in immunocompromised (90% in diabetics)

=> Commonly caused by pseudomonas aeruginosa

=> Non-neoplastic infection begins in the soft tissue of the external auditory meatus and progresses to the bony ear canal and results in osteomyelitis of temporal bone.

Question 10

What are the key features that help identify necrotising otitis externa?

Answer 10

1. Diabetes (90%) or immunocompromised (illness or treatment-related)
2. Severe, unrelenting, deep-seated otalgia
   => almost exclusively unilateral
3. Temporal headaches
4. Purulent otorrhoea
5. Possibly dysphagia, hoarseness ± lower facial nerve palsies

Question 11

How is necrotising otitis externa diagnosed and treated?

Answer 11

Diagnosis:
=> CT scan

Treatment:

1. Non-resolving otitis externa with worsening pain => referred urgently to ENT
2. IV antibiotics that cover pseudomonal infections