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Conditions of the external auditory canal
Otitis externa
OTITIS externa (OE) refers to
inflammation of the external audi-
tory canal. It can be associated
with infections (bacterial, viral or
fungal) as well as other inflamma-
tory disorders.
Otitis externa can be acute
(less than three weeks) or chronic
(greater than three weeks) and can
result in life threatening compli-
cations in immunocompromised
patients. 4
Epidemiology
Otitis externa may affect as much
as 10% of the population over the
course of their lifetime. The condi-
tion is mostly managed by the GP,
however, despite well-established
guidelines, there remains a vari-
ability in the management of otitis
externa. 5,6
Otitis externa is more common
in Australia, especially during
summer. Living in warm, humid
climates as well as swimming are
risk factors for the development
of OE. 7 Other risk factors relate
to loss of protective cerumen, and
trauma to the ear canal — both of
which can occur from cotton bud
use. 7
Pathophysiology
Infectious acute otitis externa
results when there is disruption of
the protective factors of the exter-
nal auditory canal. This includes
the disruption of normally acidic
environment (by basic solutions
such as shampoos or soaps), lack
of cerumen (for example, frequent
use of cotton buds or other clean-
ing devices), and trauma to the
epithelial lining (such as water
exposure, trauma, underlying skin
disorders). 7
Infectious acute otitis externa is
caused by bacteria in more than
95% of cases. The most common
organisms are P. aeruginosa fol-
lowed by staphylococcus species,
which can occur as a polymicro-
bial infection. 8
Box 1. Risk factors for otitis externa Box 3. Patient advice for administration of ear drops
• Water exposure – swimming, surfing or ear syringing • Loosely roll up the corner of a soft piece of facial tissue and use this to clear
any obvious discharge from your ear canal prior to applying drops. This
should not cause excessive pain.
• Disruption of cerumen – excessive cleaning with cotton buds, soapy water,
or prior radiotherapy to the area
• Trauma to the skin of the external auditory canal – ear syringing, cotton
buds, ear plugs, hearing aids, recent ear surgery or foreign bodies
• If possible, have someone help you administer the ear drops.
• Underlying skin disorder affecting canal – eczema, psoriasis, allergic
dermatitis • Lie down with the affected ear facing up to allow the drops to penetrate
throughout the canal. Stay in this position for five minutes, using a timer or
alarm to ensure you allow enough time.
• Immunocompromised state – diabetes mellitus, HIV or immunosuppressive
medications • A gentle pumping action on the tragus can help the drops penetrate the
canal and should be attempted after instillation if tolerated.
• Anatomical factors – narrow ear canals, exostoses or osteomas can result in
water trapping and predispose to recurrent infections • Do not cover your ear canal following the drops (for example, with a cotton
ball). Allow the ear canal to dry and ventilate following drops to prevent
moisture and excessive discharge building up.
Source: Brant J, Ruckenstein M. Cumming’s Otolaryngology. 2015.
Box 2. Factors that change the management of otitis externa 10
• Immunocompromised state
– Require special consideration for fungal otitis externa and skull base
osteomyelitis
• Radiotherapy
– Radiotherapy disrupts the epithelium of the external auditory canal and
causes chronic changes to the glands of the canal. This predisposes
individuals to more severe infections requiring the early introduction of
systemic antibiotics in addition to standard topical therapy
• Concurrent middle ear disease
– A perforation in the tympanic membrane or tympanostomy tubes can
result in a purulent discharge from the middle ear into the external auditory
canal, causing dermatitis and otitis externa. These patients require early
specialist review with systemic antibiotic therapy. Non-ototoxic topical
medications, such as ciprofloxacin hydrochloride, should be used when a
perforation is suspected.
Box 4. When to add systemic antibiotics to standard topical antibiotic
therapy
• Immunodeficiency conditions such as diabetes mellitus, HIV or patients
taking immunosuppressive medications
• Radiotherapy around the ear – both current radiotherapy or previous history
of radiotherapy
• If there is evidence of cellulitis beyond the confines of the ear canal into the
pinna, skin of the face or neck
• Systemic signs such as documented fevers or a history of rigors
• Severe external auditory canal swelling preventing adequate aural toilet or
wick placement
Please note: Skull base osteomyelitis requires systemic therapy but this is a
special scenario where prolonged intravenous anti-infective agents are prescribed
with specialist input.
Source: Rosenfeld et al. Otolaryngology — Head and Neck Surgery 2014.
PATIENTS WITH OTITIS
EXTERNA COMPLAIN
OF SEVERE PAIN ON
MANIPULATION OF THE
TRAGUS OR PINNA.
Figure 6a and
figure 6b: Otitis
externa. Note the
diffuse erythema
and oedema of the
auditory canal,
with a partially
obscured view
of the tympanic
membrane.
Acute bacterial otitis externa
Acute otitis externa (swimmer’s
ear) is often associated with water
exposure, which can be in the
form of either swimming or ear
syringing. Additional risk factors
are listed in box 1. 9
The typical presentation of acute
bacterial otitis externa begins with
an itchy ear canal. As the dis-
ease progresses, there is a rapid
onset (within two days) of addi-
tional symptoms such as severe
pain, swelling, aural fullness and
purulent discharge. 9 A history of
diabetes, HIV and other immu-
nocompromised states should be
identified as well as a history of
radiotherapy and the presence of
recent tympanic membrane perfo-
ration (including tympanostomy
tube placement). 10 Please see box
2 for factors that change the man-
agement of otitis externa.
On examination, patients with
otitis externa complain of severe
pain on manipulation of the tragus
or pinna. There is often associated
erythema and swelling of the pinna
and skin with pre-auricular and
cervical lymphadenopathy. Otos-

copy reveals diffuse erythema and
swelling of the canal with debris
and discharge. It can be difficult
or impossible to visualise the tym-
panic membrane in severe cases of
canal swelling. It is important to
perform a complete cranial nerve
examination to assess for sequelae
of skull base osteomyelitis such
as facial nerve paresis. In patients
with persistent disease, swabs of
the discharge should be sent for
bacterial and fungal cultures. 9
Treatment consists of sympto-
matic relief, removal of the debris
and optimisation of drug delivery
via topical antimicrobial agents.
The pain associated with otitis
externa often seems out of propor-
tion with the clinical findings. This
is explained by the highly sensitive
periosteum lying very close to the
inflamed, infected skin. Analgesia
cont’d page 22
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