ENT · Otitis Externa
The facts most likely to be tested
Pseudomonas aeruginosa is the most common bacterial pathogen associated with acute otitis externa.
Physical exam reveals tragal tenderness and auricular pull tenderness, which are pathognomonic for external ear canal inflammation.
First-line treatment for uncomplicated acute otitis externa is topical fluoroquinolone drops, such as ciprofloxacin or ofloxacin.
Topical aminoglycoside-containing drops are strictly contraindicated if there is a suspected or confirmed tympanic membrane perforation due to ototoxicity.
Malignant (necrotizing) otitis externa is a life-threatening complication typically seen in elderly diabetic or immunocompromised patients.
Malignant otitis externa is characterized by granulation tissue at the bony-cartilaginous junction of the ear canal and requires systemic anti-pseudomonal antibiotics.
Cranial nerve palsies, particularly involving CN VII (facial nerve), are a hallmark sign of advanced malignant otitis externa requiring urgent imaging.
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A 72-year-old male with a history of poorly controlled type 2 diabetes mellitus presents to the emergency department with severe, persistent right-sided ear pain and purulent otorrhea for three weeks. On physical examination, he has significant edema and erythema of the external auditory canal, and granulation tissue is visualized at the floor of the canal. He has no history of recent swimming. Cranial nerve testing reveals a new-onset ipsilateral facial nerve palsy.
What is the most appropriate next step in management?
CT scan of the temporal bone
The patient presents with signs of malignant otitis externa, a severe infection requiring imaging to assess for skull base osteomyelitis and systemic anti-pseudomonal therapy.
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Etiology / Epidemiology
Common in swimmers and those with ear canal trauma; Pseudomonas aeruginosa is the most common pathogen.
Clinical Manifestations
Tragal tenderness and otic pruritus are classic; pain is exacerbated by auricle manipulation.
Diagnosis
Clinical diagnosis via otoscopy showing erythematous, edematous canal with debris.
Treatment
Ciprofloxacin/dexamethasone drops are first-line; avoid aminoglycosides if tympanic membrane is perforated.
Prognosis
Usually resolves in 7-10 days; malignant otitis externa is a life-threatening complication in diabetics.
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Epidemiology & Etiology
Often called swimmer's ear, it results from moisture-induced maceration of the canal skin. Pseudomonas aeruginosa and Staphylococcus aureus are the primary causative organisms. Frequent use of cotton swabs or hearing aids increases risk by disrupting the protective cerumen barrier.
Pertinent Anatomy
The external auditory canal consists of a lateral cartilaginous portion and a medial bony portion. The skin here is thin and lacks a subcutaneous layer, making it highly susceptible to inflammation and intense pain upon movement of the pinna.
Pathophysiology
Excessive moisture alters the canal's pH, facilitating bacterial overgrowth. Inflammation leads to edema, which further traps moisture and debris, creating a self-perpetuating cycle of infection. In immunocompromised patients, the infection can invade the skull base, leading to osteomyelitis.
Clinical Manifestations
Patients present with otalgia, otorrhea, and a sensation of fullness. Tragal tenderness and pain with auricle manipulation are pathognomonic. Red flags include cranial nerve palsies or granulation tissue at the bony-cartilaginous junction, suggesting malignant otitis externa.
Diagnosis
Diagnosis is primarily clinical via otoscopy. Findings include erythema, edema, and purulent debris in the canal. If the canal is too swollen to visualize the tympanic membrane, pneumatic otoscopy or referral for microscopic cleaning may be required to rule out perforation.
Treatment
First-line therapy is ciprofloxacin/dexamethasone otic drops. If the canal is severely swollen, an ear wick must be inserted to facilitate medication delivery. Avoid aminoglycoside-containing drops (e.g., neomycin) if the tympanic membrane status is unknown due to potential ototoxicity.
Prognosis
Most cases resolve within one week with proper topical therapy. Malignant otitis externa requires prolonged IV antipseudomonal antibiotics and carries a high mortality rate if untreated. Patients should be advised to keep the ear dry until symptoms resolve.
Differential Diagnosis
Otitis Media: tympanic membrane is immobile and bulging
Furunculosis: localized abscess in the outer third of the canal
Otomycosis: presence of fungal hyphae and spores
Contact Dermatitis: history of exposure to topical agents or jewelry
Malignant Otitis Externa: severe pain and granulation tissue in diabetics