Otitis Externa

Definition & Overview

Classification

1. Acute Localized OE (Furunculosis)

• One or more pustules/furuncles in the EAC
• Causative organism: S. aureus
• Symptoms: itching, pain, swelling, redness, occasionally decreased hearing

2. Acute Diffuse OE ("Swimmer's Ear" / "Tropical Ear")

• Rapid onset (<48 hours) of canal inflammation
• Most common causative organism: P. aeruginosa (>90% of AOE is bacterial; P. aeruginosa and S. epidermidis are the dominant pathogens)
• Associated with water exposure or local trauma

3. Erysipelas of the Ear

• Caused by group A Streptococcus (S. pyogenes)
• Diffusely red, painful ear; hemorrhagic bullae may appear on canal walls

4. Chronic Otitis Externa (COE)

• Prolonged EAC inflammation; bilateral in >50% of patients; affects 3–5% of the population
• Mild discomfort, pruritus, aural fullness; skin shows atrophy ± stenosis
• Causes include: allergic/contact reactions (commonly neomycin), systemic diseases (psoriasis, seborrhoea, sarcoidosis, Sjögren), and chronic infection

5. Eczematous (Dermatitic) OE

• Severe pruritus, scaling, crusting, oozing, erythema
• Underlying skin conditions: contact dermatitis, seborrhoeic or atopic dermatitis

6. Malignant (Necrotizing) OE

• Aggressive, life-threatening form
• Predominantly in diabetics and immunocompromised patients
• Organism: P. aeruginosa
• Progression: apparent OE → canal maceration, granulation tissue → temporal bone osteomyelitis → intracranial extension → cranial nerve palsies (VII, IX, X, XII) or meningitis
• Bacteria are thought to access the temporal bone via the fissures of Santorini between ear cartilages

7. Fungal OE (Otomycosis)

• ~10% of AOE cases
• Severe pruritus, clear drainage, "cotton-like" debris filling the canal
• Candida: typical white discharge
• Aspergillus flavus: "wet newspaper" appearance — moist white plug with black dots

8. Viral OE (Rare)

• Organisms: varicella, measles, herpesvirus
• Herpes Zoster Oticus (HZO): canal involvement without facial palsy
• Ramsay Hunt syndrome: HZO + facial paralysis ± sensorineural hearing loss or vertigo

Predisposing Factors

Clinical Features

• Moderate-to-severe otalgia worsened by pinna manipulation (key distinguishing feature vs. mastoiditis, where tenderness is over the mastoid tip)
• Pruritus → progresses to seropurulent discharge, oedema, aural fullness, conductive hearing loss
• Signs: circumferential EAC erythema and oedema, otorrhoea, preauricular/cervical lymphadenopathy
• Weber test lateralises to the affected side (conductive loss from canal obstruction)

• Predominantly pruritus with mild discomfort
• Secretory (wet) or dry/squamous type
• Periodic waxing and waning course; may progress to medial canal fibrosis

Investigations

• Clinical diagnosis in most cases; examination under binocular microscopy preferred
• Canal culture (bacteria + fungi) for persistent or recurrent infection
• Biopsy if treatment-resistant — to exclude malignancy
• Imaging (CT/MRI): reserved for suspected spread beyond EAC
  • CT: demonstrates bony erosion in necrotizing OE
  • MRI with gadolinium: preferred for soft tissue and intracranial extension in malignant OE

Treatment

Acute OE (Uncomplicated)

• Canal debridement/cleaning — removes obstructive debris, allows drop penetration
• Topical antibiotic drops — effective for most cases; systemic antibiotics are not indicated in immunocompetent patients with infection confined to the canal
  • Fluoroquinolone drops (e.g., ciprofloxacin/ofloxacin): first choice; safe with tympanic membrane perforation
  • Aminoglycoside drops (e.g., neomycin, gentamicin): effective but contraindicated with TM perforation (ototoxic)
  • Topical corticosteroids often combined to reduce inflammation
• Acidifying drops (acetic acid) useful for mild cases and prophylaxis

Fungal OE

• Topical antifungal agents after thorough canal cleaning

Chronic OE

• Address underlying cause (allergic: remove offending agent; systemic disease: treat primary condition)
• Periodic aggressive debridement

Malignant (Necrotizing) OE

• Systemic antipseudomonal antibiotics — ciprofloxacin is standard initial therapy
• Aggressive debridement by an otolaryngologist
• MRI with gadolinium for extent assessment
• Surgical intervention for refractory cases
• Coordination with ENT is mandatory

Clinical Images

Acute otitis externa: erythema, oedema, and desquamation of the EAC skin

Impetiginised OE with honey-coloured crusts — secondary bacterial infection (S. aureus / S. pyogenes)

Exudative OE with canal narrowing from oedema and debris