Otitis Externa

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Definition

OE is an inflammatory (typically infectious) disorder of the external ear canal. There are several forms of OE

1 Acute Bacterial

2 Acute Fungal

3 Chronic

4 Malignant Otitis externa

Incidence and Epidemiology

4 of every 1000 children and adults per year

80% of the cases occur in the summer, particularly in warm, humid environments

    Pathophysiology

       Ear wax has natural protection

-Acidic pH

-It is Hydrophobic

-Lysozyme

-Rich blood supply

-Hairs

-Self cleaning mechanism: lateral migration of epithelium

Predisposing Factors

Anythings that affects the above predisposes to OE

-Pt factor-swimming/ hot pools, cotton buds

-Medical factors-local-exostosis, trauma, previous surgery, XRT, use of prologed topical drops

         -Systemic-Diabetes, immune, allergy-dermatitis

Aetiology

Bacterial

Pseudomonas aeruginosa 40%

Staphylococcus epidermidis

Staphylococcus types

Other gram-negative rods (e.g., Enterobacter, Klebsiella, Proteus, Escherichia coli)

Anaerobes Enterococcus

Fungal

Candida followed by bacterial infection

Aspergillus

Note fungal OE:either black spores (aspergillus Niger) or white fluff (A fumigates)

Fungal OE

Chronic

Usually typed of dermatitis

Eczema

Psoriasis

Chronic candida infection

Malignant OE (skull base osteomyelitis)

Pseudomonas

Fungal

Granulation tissue in the EAC 

Clinical Symptoms

Acute otitis externa:     is painful, short duration

Fungal otitis externa:   is not as painful, blocked ear canal reduced hearing is more common

Chronic otitis externa:   is not painful, itchy can have secondary acute bacterial infection 

Malignant OE:   Immune compromised mostly diabetic, deep seeded ear pain out of keeping with findings

Clinical Signs

Acute OE:   Narrow swollen canal, pain with tragus pressure

Fungal OE:  white black spores, fungal material

Chronic:      Dermatitis, may involve the pinna

Malignant OE:   Granulation tissue the bone cartilage junction, in severe cases may get crania nerve palsy.

Treatment

General principles

Through ear suction (by ENT), avoid water or trauma to the ear canal

If Oedema need a ear wick inserted and immediately drops applied (wick must be soaked with drops)

Good analgesia including NSAIDS

Mainstay treatment  is topical, in severe cases systemic therapy may be given

Acute OE

Usually sofradex ear drop would suffice

non resolving cases may need a swab and Ciproxin HC

if wick inserted this should be kept moist by Q 4 hr use of 4-5 ear drops

Wick helps deliver drops: must be soaked.

Fungal OE

Aspergillus may cause tympanic membrane damage

early diagnosis is important

suction with either Kenocomb era drops, or filling of the canal with Otocomb drops

if mild infection- boric acid powder may be applied via a puffer (Gold dust in Melbourne, ABI powder in NZ)

Chronic OE

Avoid application o topical drops

Steroid lotions Elocon lotion

Un resolving type may respond to immune modulators as Tacrolimus

Malignant OE

Need confirmation of diagnosis with TC 99 imaging

CT is not sensitive in the early stages 

Later resolution is guided by a Gallium scan

Need dual anti pseudomonas therapy with close observation 

Good diabetic control must be achieved