Monday, 11 February 2013

Otitis Externa

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


2 comments:

  1. will u use boric acid powder for treatment of suppurative otitis media?

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    Replies
    1. Hello
      I have used mixture of Boric acid 4g, hydrocortisone 1g, and ciproxin 1g for suppuraltive OME with some good outcome. However proven safety is with Ciproxin HC drops

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