Synopsis of key findings:
Patients with fungal otitis externa typically present with swelling and
erythema of the external auditory canal and report otalgia, otorrhoea,
itching and hypoacusis.1,2,5 Symptoms of itching and
otorrhoea were more common in immunocompetent patients whereas otalgia,
blocked sensation, decreased hearing and tinnitus were noted more in
immunocompromised patients.4,6
Examination findings include oedema and serous transudate of external
canal skin, erythema and perforation of a thickened tympanic membrane,
as well as serous discharge from the middle ear into the external
auditory canal.1
There is a consensus in the literature that the responsible pathogens
were Candida and Aspergillus spp.,2,5 with the former
being more common in immunocompromised patients.6
The prevalence of otomycosis is reported to be between
9%4 – 30.4%.5 The identified risk
factors include humid climates, chronic otitis, lack of
cerumen2 as well as extensive and unnecessary use of
both topical and systemic antibiotics.2 There was also
a higher incidence noted in male patients.4,6 Ho et
al. found an increased risk of otomycosis with previous otological
procedures, as well as the presence of a mastoid
cavity.4
The study by Jackman et al was key in our understanding of the
contribution of topical antibiotic drops such as Ofloxacin to the
development of otomycosis. The mechanisms are two fold: it’s action as a
bactericidal allowing fungal proliferation due to the lack of competing
bacterial growth as well as it’s neutral pH allowing an optimal
environment for fungal growth. The proposed pathophysiology was that
perforations form after sub-epithelial abscess develops on the tympanic
membrane. Fungus causes thrombosis in adjacent blood vessels, which
produces avascular necrosis of the underlying tympanic membrane
resulting in a perforation.7