Journal Reading

Otitis Externa
Investigation and Evidence-Based
Treatment
Susanne Wiegand, Reinhard Berner, Antonius Schneider,
Ellen Lundershausen, Andreas Dietz

By:
Cynthia Isra Mandahuta
M. Fadli
M. Beni Septima
Sonya Andzil M. Tori
Viona Ayu Safitri
SUMMARY
Background: Lifetime prevalence of 10% and can arise in acute, chronic,
and necrotizing forms.
Methods: This review is based on publications retrieved by a selective
search of the pertinent literature.
SUMMARY
Results:
• Treatment w/ analgesia, cleansing , and the antiseptic and
antimicrobial agents
• Local antibiotic and corticosteroid preparations-> no large-scale RCT
of their use
• Cure rate of topical antimicrobial > placebo
• Corticosteroid preparations lessen swelling, erythema, and secretions
SUMMARY
Results:
• Oral antibiotics-> spread beyond the ear canal / poorly controlled DM
or immunosuppression
• Chronic otitis externa <-underlying skin disease
• Malignant otitis externa w/ osteomyelitis, elderly DM or
immunosuppressed patients and can be life threatening.
SUMMARY
Conclusion: With correct assessment of the different types of
otitis externa, rapidly effective targeted treatment can be initiated, so
that complications will be avoided and fewer cases
will progress to chronic disease.
• Otitis externa is one of the more common diseases in otorhinolaryngological
practice and is also frequently encountered in primary and pediatric care.
• It ranges in severity from a mild infection of the external auditory canal to
life-threatening malignant otitis externa.
• Its correct treatment requires a good understanding of the anatomy,
physiology, and microbiology of the ear canal.
• No German guidelines deal specifically with otitis externa; it is briefly
discussed in the AWMF-S2k guidelines on ear pain of the German College of
General Practitioners and Family
• Physicians (Deutsche Gesellschaft für Allgemeinmedizinund
Familienmedizin, DEGAM) (1).
• Here we discuss the epidemiology, etiology, and treatment of otitis externa
in the light of the current scientific evidence.
Learning objectives

• Readers of this article should gain an overview of the epidemiology,

anatomical setting, and causes of otitis externa,
• understand the different forms of the disease,
• become acquainted with their treatment.
Methods

• We selectively searched the PubMed database for con_x0002_trolled

trials, guidelines, and reviews that appeared up to 30 April 2018 with
the key words “otitis externa,” “acute external otitis,” “otitis externa
diffusa,” “otitis externa circumscripta,” “chronic external otitis,” “otitis
externa maligna,” and “otitis externa necroticans.”
OTITIS EXTERNA
Definition
• Otitis externa is defined as an infection of the cutis and subcutis of
the external auditory canal, possibly involving the tympanic
membrane and the pinna as well.
• Its different forms include acute diffuse otitis externa, circumscribed
otitis externa, chronic otitis externa, and malignant (i.e., necrotizing)
otitis externa.
• Its differential diagnoses include perichondritis, erysipelas,
otomycosis, herpes zoster oticus, otitis externa bullosa sive
hemorrhagica, otitis media (with perforation), and eczema,
cholesteatoma, or carcinoma involving the external auditory canal (2).
Anatomy and Physiology

• The external auditory canal (ear canal) has lateral cartilaginous and medial bony portions, with an
overall length of 2–3.5 cm and a diameter of 5–9 mm (Figure 1a).
• The skin of the bony ear canal is firmly bound to the periosteum, while the skin of the cartilaginous ear
canal lies on a layer of connective tissue and contains hair follicles, sebaceous glands, and apocrine
ceruminous glands, whose exudates, combined with desquamated epithelial cells, form cerumen.
• The cartilaginous ear canal has a roof of connective tissue; its floor contains the connective-tissue clefts
of Santorini, along which infections can spread to the parotid gland, infratemporal fossa, and skull base.
• The sensory innervation of the ear canal is from the auriculotemporal nerve, the auricular branch of the
vagus nerve, the greater auricular nerve, and the posterior auricular nerve.
• The ear canal is normally colonized by bacteria, above all Staphylococcus and Corynebacterium species
and streptococci (3).
• Its pH is normally in the range of 5–5.7; the acid environment and the hydrophobic properties of the
cerumen inhibit bacterial growth (2)
 Epidemiology
• Otitis externa is common all over the world, with a higher incidence in tropical
than in temperate zones because of the higher temperature and humidity.
• Its lifetime prevalence is estimated at 10% (4).
• It affects adults most commonly, and children only rarely (generally aged 7 to
12) (e1).
• Studies from the Netherlands and the United Kingdom have shown an annual
incidence of circa 1% (5, 2).
• The incidence is increased fivefold in swimmers (6); thus, the condition is also
called “swimmer’s ear.”
Etiology
• The pathogenesis of otitis externa is multifactorial; a list of predisposing factors is shown in Table 1.
• More than 90% of cases of otitis externa are due to bacteria (6), most commonly Pseudomonas
aeruginosa(22–62%) and Staphylococcus aureus (11–34%).
• Polymicrobial infection is common (8, e3–e5).
• Fungi are a rare cause of acute otitis externa (10%) (e6) and a more common cause of chronic otitis
externa; typical pathogens are Aspergillus (60–90%) (9) and Candida species (10–40%) (e7).
Predisposing factors for fungal otitis externa include long-term antibiotic use, immunosuppression,
and diabetes mellitus.
• The changes in the ear canal that are seen in otitis externa (e.g., hyperkeratosis of the epidermis,
chronic granulation tissue, edema, or fibrosis of the dermis) tend to narrow the canal.
• Epithelial cell migration normally rids the ear canal of cerumen, cellular detritus, and
microorganisms. Interference with this process by inflammation or stenosis predisposes to the
development and maintenance of otitis externa.
Symptoms
•
• The characteristic symptom of acute otitis externa is
• severe pain in the ear (otalgia) due to irritation of the
• periosteum just under the thin dermis of the bony ear
• canal, which has no subcutis. The pain is typically
• worsened by pressure on the tragus or tension on the
• pinna. Further symptoms are otorrhea, itch, erythema,
• and swelling of the ear canal, potentially leading to
• conductive hearing loss.
Diagnosis

• Otitis externa is diagnosed from the history and physi_x0002_cal examination, including, as a minimum,
otosopic or otomicroscopic examination of the ear canal and tympanic membrane (if visible), as well as
examination of the pinna, the surrounding lymph nodes, and the skin.
• Especially if the tympanic membrane cannot be seen, screening tests of hearing or an audiological exami
nation should be performed to rule out inner ear
• involvement. When the ear canal is swollen, the tuning fork examination and the tone threshold audiogram
typically reveal conductive hearing loss.
• The characteristic findings in acute otitis externa are pain induced by pressure on the tragus and tension on
the pinna, along with swelling of the ear canal, perhaps to the point of total obstruction; the skin of the ear
canal can be either erythematous or pale because of edema (Figures 1b, c).
• Secretion is common and can be swabbed for culture and pathogen resistance testing. Rarely, swelling makes
the pinna protrude (pseudomastoiditis).
• Mild fever (up to 39°C) may be present; markedly higher temperatures suggest spread of the infection
beyond the ear canal.
Figure 1:
a) Normal

b) Swollen introitus

c) Bacterial otitis
externa.

d) Otomycosis
Treatment
• The treatment of uncomplicated acute otitis externa consists of cleansing the ear
canal, topical antiseptic and antimicrobial treatment, and adequate analgesia.
• Primary oral antibiotic treatment should be given only if the infection has spread
beyond the ear canal, in the setting of poorly controlled diabetes mellitus or
immunosuppression, or if topical treatment is not possible (10) (Figure 2).
• The DEGAM, in its guideline on ear pain, accordingly recommends cleansing the
ear canal and using local antibiotics and/or corticosteroids as indicated, in
consideration of their availability, costs, and risks.
• Systemic antibiotic treatment should be considered in individual cases if there
are systemic manifestations, or whenever problematic organisms are found (1).
1. Cleansing the ear canal

• Atraumatic cleansing of the ear canal consists of the removal of cerumen and exudate;
the exudate may contain toxins (e.g., Pseudomonas exotoxin A [e8]) that sustain the
inflammatory process and limit or prevent the efficacy of topical drugs.
• Cleansing should be performed by an experienced otorhinolaryngologist under
microscopic vision with suction or an aural hook; injury to the ear canal must be avoided.
• Once a defect of the tympanic membrane has been ruled out, the ear canal can
alternatively be cautiously rinsed with distilled water or normal saline.
• In rural areas without otolaryngology coverage, this can also be done by a general
practitioner or pediatrician.
• Patients should not clean their own ears with cotton swabs, because microtrauma
encourages bacterial invasion.
2. Topical treatment
• Topical treatment with antiseptic agents, antibiotics, cor_x0002_ticosteroids, and combinations of these is recommended for the treatment of uncomplicated
acute otitis externa because of its safety, efficacy compared to placebo, and excellent results in randomized trials and meta-analyses (10–12, e9–e11).
• Whichever topical agent is used, 65–90% of patients improve clinically in 7–10 days (8).
• In a Cochrane meta-analysis of randomized controlled trials, antiseptic agents and antibiotics yielded equally good clinical results; no difference was found
between single agents and combinations of agents, with or without additional corticosteroids (10).
• Nonetheless, the additional administration of topical steroids can lessen erythema and secretions
• .A few trials have shown different results from monotherapy as opposed to combination therapy, but the heterogeneity of the substances used makes it hard
to draw any general conclusions (10).
• In a systematic review, topical antimicrobial drugs were found to increase the clinical cure rate by 46% and the bacteriological cure rate by 61% compared to
placebo (11).
• Ototoxic substances must be avoided if the eardrum is perforated. No randomized trials have been performed on the insertion of a drug-soaked gauze strip
into the ear canal as the sole treatment, but this method does seem to improve the local efficacy of topical treatment and to lessen inflammatory edema (10).
• The decisive factor for optimal topical treatment is patient instruction in how to apply the eardrops.
• The patient should lie on his or her side with the affected ear up, apply the drops in the ear canal, and keep lying on one side for 3–5 minutes thereafter.
Gently moving the ear back and forth helps convey the drops to their site of ac_x0002_tion (8). The drops should be applied two to five times daily,
depending on the preparation (Table 2).
• Topical treatment leads to a cure of acute otitis externa in 65–90% of patients in 7–10 days, whatever agent is chosen (8).
• In the past, dyes such as gentian violet and acid brilliant green were commonly used for the local antiseptic and desiccating therapy of various ear diseases,
but these are toxic and no longer approved for aural use.
 Figure 2
Treatment algorithm
(modified from
Rosenfeld et al)
3. Topical antiseptic agents

• The treatment of acute otitis externa with various topical antiseptic agents has been
described, including acetic acid, chlorhexidine, aluminum acetate, silver
• nitrate, N-chlorotaurine, fuchsin, and eosin (5, 13, 14, e12–e14).
• The advantage of topical antiseptic agents is their broad-spectrum efficacy.
• Many preparations contain alcohol, which is an effective disinfectant and, in high
concentration, removes water from tissue and thus lessens edema. pH reduction by acid
preparations (e.g., 2% acetic acid) inhibits bacterial growth (3, 14), as most bacteria
prefer a pH-neutral environment.
• Thus, otitis heals more rapidly if treated in this way rather than with placebo. Acetic acid
is comparably effective to antibiotic or corticosteroid drops after 7 days of treatment, but
significantly less effective if treatment is needed for 2–3 weeks (10)
4. Topical antibiotics
• Topical antibiotics should cover the most common pathogens, i.e., Pseudomonas aeruginosa and Staphylococcus aureus, and should be
tailored to the drug resistance and sensitivity patterns of the cultured pathogen, if possible
• .The approved types of antibiotic eardrops in Germany contain quinolones (ciprofloxacin), amino -glycosides (neomycin), or polymyxins
(polymyxin B) (Table 2).
• Compared to placebo, these lead to more rapid symptomatic relief and cure, and to lower recurrence rates (11).
• Quinolones are highly effective and cause no local irritation, but prolonged exposure to them can lead to resistance against this important
class of antibiotics.
• Neomycin is effective but ototoxic and should be given only if the eardrum is intact. It also causes contact dermatitis in 15–30% of patients
(9, 15–17, e15).
• Polymyxin monotherapy is not effective against? staphylococci and other Gram-positive microorganisms (9).
• A Cochrane analysis showed no difference in the clinical efficacy of quinolone versus non-quinolone preparations (10).
• In clinical practice, just as in clinical trials, ophthalmological antibiotic preparations are sometimes used off label to treat otitis externa; the
most common active substance is ofloxacin (10, 11).
• Topical administration results in a high local concentration of drug without the side effects of systemic treatment.
• Nonetheless, for the reasons just explained, topical antibiotics such as ciprofloxacin or ofloxacin should not be given any longer than
necessary.
• Ototoxic substances must not be used if the eardrum is perforated.
Topical corticosteroids

• Topical corticosteroids are used mainly because they lessen edema; antibacterial
and antifungal effects have also been described (3).
• Only individual case reports on topical corticosteroid monotherapy are available
(18, 19), so the evidence for this practice is still weak (10).
• In a few randomized controlled trials, treatment with topical combinations of
antibiotics and corticosteroids lessened swelling, erythema, and secretions more
effectively than antibiotics alone.
• The greatest difference was seen during the first few days of treatment (20, 21).
• High-potency corticosteroids are probably more effective than low-potency
corticosteroids against pain, inflammation, and swelling (22) (Table 2).
Antifungal treatment

• In case of fungal infection (Figure 1d), strips soaked in a solution of

antifungal drug (ciclopirox, nystatin, clotrimazole, or miconazole)
should be laid in the ear canal.
• Dye solutions are no longer recommended because of their potential
toxicity to the inner ear and their low efficacy (23).
• If the eardrum is perforated, systemic antifungal treatment should be
given according to the resistance and sensitivity pattern
(e.g.,fluconazole or itraconazole) (23).
Analgesia

• Pain relief is an essential part of the treatment of acute otitis externa.

• Severe ear pain arises because the highly sensitive periosteum of the
bony ear canal is usually involved in the inflammatory process.
• Suitable analgesia should, therefore, be provided, e.g., with ibuprofen or
acetaminophen. Topical local anesthetics can be used as well (Table 2),
unless the eardrum is perforated or a myringostomy tube is in place.
• Local anesthetics, however, can also mask progressive disease; if they are
used, the patient should be followed up clinically in 48 hours so that the
effect of treatment can be judged (8).
Oral antibiotic treatment

• Despite the well-documented safety and efficacy of topical preparations, 20–40% of

patients treated for acute otitis externa receive systemic antibiotics as their primary
treatment (24, 25).
• This should be avoided in uncomplicated acute otitis externa because of the side
effects and the risk of inducing drug resistance.
• On the other hand, oral antibiotics are indicated to treat acute otitis externa if the
patient suffers from poorly controlled diabetes mellitus or
immunosup_x0002_pression, or if the infection extends beyond the ear canal.
• Antibiotics should be given that are effective against both Pseudomonas aeruginosa
and Staphylococcus aureus (e.g., quinolones). Optimally, antibiotics should be tailored
to the findings of bacterial culture and sensitivity testing.
Follow-up and secondary prevention

• The response to treatment should be checked in 48–72 hours.

• If there is no response, the correctness of the diagnosis and the adequacy of
treatment should be critically reconsidered, and the causative pathogen should
be identified if possible. Known risk factors should be avoided to prevent
further episodes of infection.
• In particular, the ear canal should be kept dry and should be dried with a hair
dryer if water enters it (10).
• If the self-cleansing mechanism of the ear canal is dysfunctional, then the ear
canal should be cleansed by a physician whenever the patient intends to spend
a considerable amount of time swimming (e.g., a beach holiday).
Circumscribed otitis externa
Definition

• Circumscribed otitis externa is an abscess-forming infection of a hair

follicle (i.e., a furuncle) in the cartilaginous part of the external
auditory canal
Etiology
• Mostly due to Staphylococcus aureus.
Treatment
• If mild, it is treated with topical antibiotic eardrops, salves, or salve
strips, along with analgesics.
• If more severe, it is additionally treated with oral antibiotics and
lancing of the furuncle, as needed.
Chronic otitis externa
• Manifestations of otitis externa lasting longer than three months, or more than four attacks of otitis externa per year,
are designated as chronic otitis externa. This
• may result from inadequately treated acute otitis externa, although 15% of cases of acute otitis externa heal
• within 10 days (e16), but the cause usually lies else_x0002_where. Involvement of the ear canal by a skin disease
• such as atopic dermatitis or psoriasis is common. An
• alkaline pH in the ear canal due to the inflammatory
• process can also predispose to chronic otitis externa
• (e17). The chronic form of the condition affects both
• ears in more than half of patients (26). Its typical symp_x0002_toms are itch and conductive hearing loss due to
ob_x0002_struction, while ear pain is rare. There are two main
• clinical presentations: the seborrheic form is character_x0002_ized by a lack of cerumen and by dry, scaly, red, or
• shiny skin in the ear canal, the eczematous form by
• moist, erythematous skin (26). Itching can lead the pa_x0002_tient to manipulate the ear canal, leading to excoriation
• and, in turn, to acute inflammation. Chronic inflam_x0002_mation causes progressive fibrosis of the ear canal.
Treatment
• Treatment
• The goals of treatment are to return the skin of the ear
• canal to its original, normal state and to promote the
• production of cerumen. All potential irritants, such as
• shampoo or soap, should be kept away from the ear, and
• the ear canal should be kept dry. The treatment of
• underlying illnesses, such as skin diseases or auto -
• immune disorders, is the basis of therapy. Only a few
• randomized controlled trials on drug therapy for
• chronic otitis externa have been carried out, generally
• on a mixture of patients with acute or chronic otitis
• externa, so that no explicit recommendations can be
• derived for the treatment of chronic otitis externa as a
• distinct entity (e18–e20).
Treatment
• The goal of topical treatment
• is to suppress chronic inflammation. Swabbing for cul_x0002_ture, to exclude bacterial or fungal infection as the
• cause, is recommended. The application of strips
• soaked in alcohol or corticosteroid solution can locally
• lessen edema. In case of an acute exacerbation, topical
• antibacterial or antifungal drugs may be needed.
• Chronic otitis externa often fails to respond to treatment
• administered for several weeks.
• Oral corticosteroids can be effective in cases
• resistant to other forms of treatment (27). Local treat_x0002_ment with tacrolimus has been described as well
(28).

• Surgical canaloplasty to widen the ear canal is only

• indicated if the canal is stenotic.
Malignant (necrotizing) otitis externa
• Malignant (necrotizing) otitis externa is a destructive
• infection of the external auditory canal with invasive
• perichondritis and osteomyelitis of the lateral skull
• base, arising mainly in elderly men who are either
• diabetic or immunosuppressed (29). Its incidence is not
• precisely known. Rare cases have been described in se_x0002_verely immunocompromised children, such as
children
• with acute leukemia or who have undergone bone
• marrow transplantation (e21, e22). Early diagnosis is
• essential; intractable otitis externa should always
• prompt the suspicion that the patient might actually be
• suffering from the malignant (necrotizing) form of the
• condition.
Diagnosis and manifestations
• In about 90% of cases, Pseudomonas aeruginosa can be
• isolated from the exudate in the ear canal (6, e23). Pro_x0002_teases released into the surrounding tissue can cause
• marked tissue destruction and accompanying vasculitis
• (30). The infection can spread along the clefts of Santori_x0002_ni to the parotid gland, the periauricular soft tissue, and
• the temporomandibular joint. Spread of infection along
• the skull base can lead to inner ear damage, cranial nerve
• deficits, venous sinus thrombosis, meningitis, and brain
• abscess. Otalgia is intense, but nonspecific (frequency,
• 84–100% [29]); along with conductive hearing loss and
• fetid otorrhea (frequency, 17.6–100% [29]), granulations
• or polyps are typically found in the floor of the ear canal
• (frequency, 42.1–100% [29]), sometimes with exposed
• bone, particularly at the junction of the bony and
• cartilaginous portions of the canal, due to the underlying
• osteitis (8) (Figure 3)
Diagnosis and manifestations
• . Further manifestations can arise
• that reflect further complications. Imaging studies typi_x0002_cally reveal soft-tissue swelling in the external auditory
• canal. Petrous osteomyelitis is manifested by bony
• destruction, usually (80%) spreading toward the tempo_x0002_romandibular joint and the clivus (31). The gold standard
• for the diagnostic imaging of petrous osteomyelitis is a
• combination of static and functional imaging (where
• available), with fluorodeoxyglcose positron-emission
• tomography and magnetic resonance imaging (FDG_x0002_PET/MRI) as well as high-resolution computed
• tomography (CT). Functional imaging enables the detec_x0002_tion of osteitis in an early stage before bone erosion can
• be seen on CT (31). The advantages and disadvantages of
• each imaging modality for the evaluation of petrous
• osteomyelitis are listed in Table 3. A biopsy should
• always be performed to rule out a malignant tumor or
• cholesteatoma of the external auditory canal. Malignant
• otitis media is very rare in children; when it is suspected,
• MRI is the imaging study of choice.
Treatment
•
• High-grade evidence on the treatment of malignant otitis
• externa is lacking (29). Pathogen-specific parenteral or
• oral antibiotics, tailored to the findings of sensitivity and
• resistance testing, are recommended for at least 4–6
• weeks (29, 32), as it takes this long for the involved bone to become revascularized (33). If the sensitivity and
re_x0002_sistance testing is not yet definitive, empirical antibiotic
• treatment against Pseudomonas aeruginosa should be
• begun, depending on the severity of the condition. Topi_x0002_cal treatment with antiseptic or antimicrobial strips in
the
• ear canal can be given in addition. If the condition takes
• a protracted course or fails to respond to medical treat_x0002_ment, necrotic tissue and bone sequestra should be
surgi_x0002_cally removed, because they impair the penetration of
• antibiotics and the body’s own defensive substances into
• the involved tissue (34).
Treatment
• Extensive resection in the
• region of the lateral skull base does not improve the
• outcome. Optimal blood sugar control is mandatory. Ac_x0002_companying hyperbaric oxygen therapy may increase the
• cure rate, but no randomized controlled trials on this
• topic are available (35). Regular clinical and radiological
• follow-up examinations are needed to document the
• response to treatment and to detect any recurrence. The
• suggested strategies range from imaging only if new
• symptoms arise to intermittent imaging at 2–6 week in_x0002_tervals until no infectious process can be seen any longer
• (36). Petrous bone osteomyelitis in malignant otitis ex_x0002_terna is associated with a mortality of 10–21% (17,
• 37–39, e24). Mortality is elevated if two or more of the
• following factors are present: age >70, diabetes mellitus,
• facial nerve palsy, or a positive CT (bone erosion, soft-
• tissue swelling) (40).
Conclusions for routine clinical practice

• Otitis externa is diagnosed from the history and physi_x0002_cal examination. Uncomplicated acute otitis externa
• can be treated to good effect with cleansing of the ear
• canal, antiseptic or antibiotic eardrops with or without
• corticosteroids, and preventive measures. Otomycosis
• should be treated with antifungal agents. For patients
• with chronic otitis externa, irritating substances should
• be kept away from the ear, and potential underlying
• diseases should be treated. Persistent otitis externa,
• granulation tissue, or freely exposed bone in the
• external auditory canal may be a sign of malignant
• (necrotizing) otitis externa. Early diagnosis and the
• rapid initiation of a 4- to 6-week course of antibiotics
• help lower the morbidity and mortality of this condi_x0002_tion