Distinguishing Otitis Externa from Acute Otitis Media
Otitis externa is an infection of the external ear canal characterized by tragal/pinna tenderness and normal tympanic membrane mobility, while acute otitis media (AOM) is a middle ear infection behind the tympanic membrane characterized by bulging or immobile tympanic membrane without tragal tenderness. 1
Anatomical Location
- Otitis externa affects the skin and subcutaneous tissue of the external auditory canal, sometimes involving the auricle (pinna) 2
- Acute otitis media involves inflammation and infection of the middle ear cavity behind the tympanic membrane, with middle ear effusion (fluid) present 1
Key Clinical Distinguishing Features
Physical Examination Findings
- Hallmark sign: Intense tenderness when pushing the tragus or pulling the pinna - this tenderness is often disproportionate to the appearance of the ear canal
- Diffuse ear canal edema and erythema visible on otoscopy
- Normal (good) tympanic membrane mobility on pneumatic otoscopy
- Normal peaked curve (Type A) on tympanometry
- Possible otorrhea or debris in the ear canal
- Regional lymphadenitis or cellulitis of the pinna may be present
- No tenderness with tragus or pinna manipulation - pain is not exacerbated by ear manipulation
- Moderate-to-severe bulging of the tympanic membrane, or mild bulging with recent (<48 hours) onset of ear pain
- Absent or limited tympanic membrane mobility on pneumatic otoscopy
- Flat tracing (Type B) on tympanometry
- Intense erythema of the tympanic membrane
- Possible air-fluid level visible behind the tympanic membrane
Symptoms
Otitis Externa: 1
- Otalgia (70% of cases)
- Itching (60% of cases)
- Fullness (22% of cases)
- Hearing loss (32% of cases)
- Pain with chewing due to jaw movement affecting the ear canal
Acute Otitis Media: 1
- Rapid onset of ear pain
- Fever
- Irritability (especially in children)
- General illness symptoms
- Often preceded by viral upper respiratory tract infection
Predisposing Factors
Otitis Externa: 1
- Humidity or prolonged water exposure (swimmer's ear)
- Dermatologic conditions (eczema, seborrhea, psoriasis)
- Anatomic abnormalities (narrow canal, exostoses)
- Trauma from cotton swabs, earplugs, or hearing aids
- Ear canal obstruction by cerumen or foreign objects
Acute Otitis Media: 1
- Viral upper respiratory tract infection causing Eustachian tube dysfunction
- Peak incidence in children 6-47 months of age
- Following viral infection, 37% develop AOM and 24% develop OME
Microbiology
- Pseudomonas aeruginosa (most common)
- Staphylococcus aureus
- Fungal organisms (Aspergillus, Candida) after prolonged antibiotic use
Acute Otitis Media: 1
- Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
- Viral pathogens may be present alone (5% of cases) or with bacteria
Critical Diagnostic Pitfall
Otitis externa can mimic AOM because erythema may involve the tympanic membrane. 1, 3 The key to proper differentiation is pneumatic otoscopy: good tympanic membrane mobility indicates otitis externa, while absent or limited mobility with middle ear effusion indicates AOM. 1, 3 This distinction is essential because AOM may require systemic antimicrobials, while otitis externa is treated with topical preparations. 1
Treatment Implications
- Topical preparations are the mainstay of treatment
- Aural toilet (cleaning) necessary when ear canal is obstructed
- Systemic antibiotics NOT recommended as initial therapy unless infection extends beyond the ear canal or specific host factors present (diabetes, immunocompromise)
- Pain assessment and management is essential
- Symptomatic management is the mainstay for most cases
- Antibiotics reserved for children with severe, persistent, or recurrent infections
- Bilateral or unilateral AOM in children 6 months to 2 years warrants antibiotic therapy
Reassessment
For both conditions, reassessment is necessary if symptoms don't improve within 48-72 hours. 3, 2