Otitis Externa

By

Dr. T. Balasubramanian M.S. D.L.O.

Synonyms: Infections of the external ear

Definition: Otitis externa is defined as infection / inflammation of the external auditory canal / auricle. It can range in its severity between mild infection to a more severe one. It is one of the most common disease involving the external ear.

Classification:

Otitis externa is classified as follows:

1. Acute diffuse otitis externa (commonly caused by bacteria)

2. Acute localised otitis externa (commonly furuncle)

3. Chronic otitis externa

4. Eczematous otitis externa

5. Fungal otitis externa

6. Malignant otitis externa

Predisposing factors responsible for otitis externa:

Under normal conditions the skin lining the external auditory canal is well protected by its self cleansing mechanism. In diseased conditons several factors may come into play in the pathogenesis of otitis externa.

1. Absence of cerumen: The cerumen plays an important role in the protection of the external canal. It protects the external canal from moisture. It also has anti bacterial properties which helps in the protection of the external canal. The cerumen also lowers the pH of the external canal making it difficult for the bacterial pathogens to colonize.

2. Removal of cerumen by ear buds: is one of the common causes of otitis externa. The act of removal traumatises the skin lining of the external canal making it vulnerable to infections.

3. Frequent exposure to water: external canal when constantly bathed in water loses its ability to protect itself. The presence of water macerates the skin lining of the external canal and also increase the pH of the external canal making it more favourable for bacterial colonisation. This condition is common in swimmers.

Acute diffuse otitis externa:

This is also known as the swimmers ear. This is an inflammatory condition involving the external canal in a diffuse manner. This condition is common in swimmers because of the propensity for the external canal to be exposed to water for long durations. This exposure leads to maceration of the external canal skin, and also lowers the pH of the external canal providing an environment favorable to infections.

Main symptoms:

1. Itching in the external canal

2. Tenderness on palpation

3. Aural fullness rarely occur due to the reduction in size of the external canal lumen due to oedema

4. Rarely stenosis of the external canal may occur causing accumulation of debris and secretions

Common signs:

1. Erythema of the external canal

2. Oedema of external canal

3. Secretions from the external canal (weeping canal)

4. Pain on mastigation

5. Pulling of helix in a postero superior direction cause pain

6. In advanced cases fever and lymphadenopathy may occur (pre and post auricular nodes may be involved)

Stages of acute diffuse otitis externa: (Senturia)

Preinflammatory stage: is characterised by intense itching, edema and sensation of fullness in the ear.

Inflammatory stage: may be divided into mild, moderate and severe.

Mild acute inflammatory stage: here the cardinal features are increased itching, pain, mild erythema and oedema of the external canal skin. At later stages exfoliation of skin with minimal amount of cloudy secretions may be seen in the external canal.

Moderate acute inflammatory stage: in this stage the itching and tenderness of the external canal intensifies. The external canal is narrowed due to oedema and accumulation of epithelial debris.

Severe acute inflammatory type: In this stage pain becomes intolerable to such an extent the patient may refuse to eat, the lumen of the external canal becomes totally obliterated due to oedema and accumulated epithelial debris. Otorrhoea may become purulent. In addition regional nodes may also be involved. Infections from the external canal may involve the parotid gland via the fissure's of santorini.

Common organisms involved: Psuedomonas aeruginosa and staphylococcus aureus are commonly cultured from the external canal of these patients. The normal commensols like staphylococcus epidermidis and corynebacteria are conspicously absent.

Management:

The aim is two fold:

1. Resolving the infection

2. Promoting the external canal skin's recovery to its original state.

Firstly the canal is cleaned atraumatically by gentle suctioning and debridement under microscope. Topical hydrogen peroxide solution instilled will help the process of debridement.

A cotton wick dipped in I.G. paint can be inserted in to the external canal and allowed to stay for a day. This will reduce the external canal skin oedema and will increase the size of the meatus. Ear drops containing a mixture of neomycin and 1% hydrocortisone may be instilled as ear drops atleast three times a day. In addition to the antibiotic and antiinflammatory effects this drug reduces the pH of the external canal making it more resistant to the organisms.

In severe cases oral antibiotics and anti inflammatory drugs can be resorted to. Quinolones are commonly used oral antibiotic.

Acute localised otitis externa: This condition is otherwise known as furunculosis or circumscribed otitis externa. This is a localised infection usually found to involve the lateral 1/3 of the external canal. It also has a propensity to involve the posterior superior aspect of the external canal. This is caused due to obstruction of the apopilosebaceous units found extensively in this area.

Trauma to skin in this area followed by infection is commonly attributed cause. The organism responsible is commonly staph aureus.

Symptoms:

1. Localised pain

2. Localised itching

3. Purulent discharge if the abscess ruptures

4. If oedema or abscess occludes the external canal hearing loss can occur.

Fig showing furuncle of external auditory canal

Signs:

1. Erythema of the skin

2. Localised abscess formation

Management:

If the abscess is pointing it can be treated by incision and drainage. Oral antibiotics should be used. The preferred drug of choice is penicillin of first generation cephalosporins. Anti inflammatory drugs can be used to reduce inflammation and pain.

These patients must be advised to cut their nails short and to keep their hands clean, since this is the commonest route of infection.

Chronic otitis externa:

This is a chronic infection / inflammation involving the skin lining of the external canal. There is thickening of the skin lining of the external canal due to persistent low grade infection / inflammation.

Symptoms:

1. Unrelenting pruritus

2. Mild pain

3. Presence of dry skin in the external canal

Signs:

1. Asteatosis (lack of ceumen)

2. Hypertrophic external canal skin

3. Presence of dry flaky skin in the external canal

4. Mild tenderness on ear manupulation

5. Rarely muco purulent otorrhoea

Cultures from the external canal of these patients are highly unreliable because they would have been using various antibiotic drops to surmount the problem.

Management:

Involves extensive use of acetic acid ear drops. This helps to reduce the pH of the skin lining the external canal making it more resistant to bacterial infections. In intractable cases steriod drops can be tried. Antibiotic drops may not be useful in these patients.

Surgery is indicated in extreme cases. A canalplasty is performed to widen the external canal. The involved skin may be removed to be replaced by a split thickness graft.

Eczematous otitis externa:

This condition includes various dermatologic conditions involving the skin of the external canal. It may range from atopic dermatitis, contact dermatitis, seborrheic dermatitis, neuro dermatitis, infantile eczema etc.

This condition is characterised by intense itching, infact this could be the only complaint of the patient. On examination, erythema of the external canal skin may be seen. There may also be associated scaling and oozing from the canal skin.

Success lies in the management of the underlying dermatologic condition.

Otomycosis:

It is also known as Fungal otitis externa. This is the commonest type of otitis externa in tropical countries. This condition is associated with increased ear canal moisture, or following treatment of otitis external by prolonged use of topical antibiotics. The protective cerumen layer is absent in these patients. This condition is more common in diabetics.

Symptoms:

1. Intense itching

2. Pain when otitis externa is coexistant

3. Blocking sensation due to the presence of fungal balls

Signs:

1. Inflammed external canal skin

2. External canal tenderness

3. Fungal debris (black in case of aspergillus and white in the case of candida). Invariably the infection is mixed type.

Management:

The condition is managed by careful aural toileting to remove the fungal balls. The best way to remove fungus from the ear canal is by aural syringing. Antifungal ear drops of clotrimazole can be administered. If secondary infections are present oral antibiotics and antiinflammatory drugs may be resorted to.