AKT · ENT/Ear & hearing

Otitis externa

Diffuse inflammation/infection of the external ear canal

Overview

Inflammation of the external auditory canal ("swimmer's ear"), usually bacterial (Pseudomonas aeruginosa, Staphylococcus aureus). Pain, itch and discharge with a tender, oedematous, debris-filled canal. The must-not-miss is necrotising (malignant) otitis externa in the diabetic/immunocompromised.

Recognise

Ear pain (worse on moving the tragus/pinna), itch, and discharge (otorrhoea)
Red, oedematous, debris-filled canal; conductive hearing loss if the canal occludes
Risk factors: swimming/water exposure, eczema/psoriasis, cotton-bud trauma, hearing aids

Red flags

Severe deep pain, granulation tissue in the canal, cranial nerve palsy (esp. facial) in a DIABETIC/immunocompromised patient → necrotising (malignant) otitis externa — urgent ENT, IV antipseudomonal, imaging

Differentials & how to tell them apart

Acute otitis mediapain is deep with a bulging/red tympanic membrane and a preceding URTI; otitis externa pain is on tragal/pinna movement with a normal middle ear

Necrotising (malignant) otitis externasevere pain, granulation, cranial nerve palsy in a diabetic/immunocompromised — an emergency, not simple OE

Furuncle (localised OE)a single tender boil in the outer canal

Ramsay Hunt syndromevesicles in the canal/pinna + facial palsy (zoster) — see neurology

Otitis externa — oedematous, debris-filled canal
James Heilman, MD / CC BY 3.0 — Wikimedia Commons

Investigations

Clinical (otoscopy). Swab if treatment fails or it is severe/recurrent. Suspected necrotising OE → CT/MRI + raised inflammatory markers, urgent ENT.

Management

Aural toilet + topical antibiotic/corticosteroid ear drops (acetic acid for mild)

1Analgesia + keep the ear dry; mild OE → acetic acid 2%; otherwise topical antibiotic/corticosteroid drops for ~7 days, with aural toilet (microsuction) if debris obstructs.Gate: Avoid AMINOGLYCOSIDE drops (neomycin/gentamicin) if the tympanic membrane may be PERFORATED (ototoxic) — use a quinolone (ciprofloxacin) instead; and severe pain + granulation + cranial nerve palsy in a DIABETIC = necrotising OE → urgent ENT + IV antipseudomonal, not just drops
2Not settling → swab-guided drops, ENT referral for microsuction/wick; necrotising OE → admit, IV ciprofloxacin, imaging, prolonged treatment.

Topical aural toilet + acetic acid 2% spray — mild OE; restores an acidic environment

Topical antibiotic/corticosteroid drops — e.g. ciprofloxacin/dexamethasone, or neomycin/betamethasone

Avoid aminoglycoside drops if the eardrum is perforated — ototoxicity risk — use a non-ototoxic agent (e.g. ciprofloxacin) if perforation possible

Systemic antibiotics (ciprofloxacin) — reserved for spreading cellulitis or necrotising OE

Key points

Pain on moving the tragus/pinna points to the canal (OE) rather than the middle ear (OM). Necrotising OE is the diabetic emergency — facial nerve palsy is the red flag.

Monitor & prognosis

Response at ~1 week; necrotising OE needs prolonged treatment + ENT follow-up.

Usually resolves with topical treatment; necrotising OE is serious.

Source: NICE CKS Otitis externa