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Outer Ear: Anomalies of Development, Trauma, Foreign Bodies, and Inflammatory Diseases

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I. EMBRYOLOGY & NORMAL DEVELOPMENT

• 5 weeks gestation: The auricle develops from the first (mandibular) and second (hyoid) branchial arches. Six distinct condensations — the Hillocks of His — give rise to auricular components: Hillock 1 → tragus; Hillock 2 → helical crus; Hillock 3 → helix; Hillock 4 → antihelix; Hillock 5 → antitragus; Hillock 6 → lobule.
• 8 weeks gestation: The cartilaginous (outer third) of the external auditory canal (EAC) derives from invagination of the concha cavum (first branchial groove). The bony EAC (inner two-thirds) derives from the meatal plug — a solid epithelial core that grows from the primary meatus toward the primitive tympanic cavity.
• 21 weeks gestation: Epithelial cells of the meatal plug resorb to canalize the bony EAC. Incomplete resorption results in atresia or stenosis.

• Medial EAC ossifies by 2 years; reaches adult size by 9 years.
• Tympanic membrane is almost adult size at birth but horizontally oriented; becomes more vertical as EAC elongates.
• Pinna is 80% of adult size by age 5, adult size by age 9; the lobule may continue to grow thereafter.

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II. ANOMALIES OF DEVELOPMENT

A. Preauricular Tag

• Most common ear anomaly.
• Caused by supernumerary hillock formation.
• May be associated with Branchio-Oto-Renal (BOR) syndrome (hearing loss + branchial cleft cyst + renal anomalies) or other craniofacial syndromes.
• Management: elective surgical removal.

B. Preauricular Pit / Sinus

• Likely due to failure of fusion of the hillocks.
• Most commonly located at the helical root; a pit below the tragus is more likely a first branchial cleft anomaly.
• May be associated with BOR syndrome.
• Acute infection: antibiotics + incision and drainage if needed.
• Definitive treatment: complete surgical excision after resolution of inflammation, including the entire tract plus cartilage at its base — to prevent recurrence and postoperative infection.

C. Microtia

• Absence of lobule is unusual; more commonly associated with retinoic embryopathy or CHARGE syndrome.

• Bone conduction ABR before 4 months of age.
• Rule out concomitant atresia or associated syndrome.

• Masking with longer hair
• Adhesive-retained prosthesis

1. Bone-Anchored Auricular Prosthesis (BAAP) — good for burns, auricular avulsion, or failed microtia repair; disadvantages: removes auricular remnant, requires daily maintenance.
2. Microtia repair — performed at age 5–6 years when rib cartilage is large enough; reconstruction performed 3–4 months before atresia repair.
   • Autogenous rib graft (Brent: 3-stage; Nagata: 2-stage) — maintenance-free after healing; risks include pneumothorax, infection, poor cosmesis.
   • Synthetic implant (Medpore) — can be done as early as age 3; varied success, risk of extrusion.
   • Irradiated rib — largely abandoned due to high resorption rate.

D. Aural Atresia

• Incidence: 1:20,000 live births.
• More common in males, unilateral, right side predominant.
• Associated syndromes: Apert, Crouzon, Pfeiffer, Goldenhar (hemifacial microsomia), Treacher Collins, Duane, Turner, trisomies 13/14/15/18/21/22, renal dysgenesis.
• Embryologically: results from failed or incomplete involution of the meatal plug, causing conductive hearing loss and risk of canal cholesteatoma.

• Bone conduction ABR prior to 4 months.
• High-resolution CT temporal bone if canal stenosis — to rule out canal cholesteatoma or if drainage is present.

• Monitor hearing; early amplification.
• Unilateral: early repair only if canal cholesteatoma present; bone conduction hearing aid on atretic side.
• Bilateral: early bone conduction hearing aid.

1. Percutaneous BAHA — bone conduction threshold must be ≤40–45 dB; superior and consistent hearing; no water precautions; disadvantages: failure to osseointegrate, infection.
2. Transcutaneous magnet-retained device — improved cosmesis but skin breakdown risk.
3. Atresia repair — usually after age 5, performed after microtia repair. Jahrsdoefer criteria (CT-based scoring, score ≥8/10 predicts good outcomes):
   • Stapes present (2 pts), oval window patent (1), round window patent (1), incus-stapes connection (1), malleus-incus complex (1), facial nerve position (1), middle ear space aerated (1), mastoid aeration (1), external ear appearance (1).

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III. TRAUMA TO THE OUTER EAR

A. Lacerations of the Auricle

• Simple (with or without involved cartilage)
• Stellate (from blunt trauma)
• Partial or total avulsion

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B. Auricular Hematoma

• Typically occurs from blunt trauma (common in wrestlers, boxers, martial artists).
• Blood accumulates between cartilage and perichondrium, stripping the perichondrium and cutting off blood supply to cartilage.

• Incision and drainage
• Through-and-through mattress sutures with bolster dressing (to prevent re-accumulation)
• Systemic antibiotics — fluoroquinolones preferred

• Fibrosis → "Cauliflower ear" / wrestler's ear (irregular fibrocartilaginous deformity)
• Perichondritis

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C. Frostbite

• Occurs from exposure to subfreezing temperatures and wind, leading to disruption of the endothelial layer with extravasation of erythrocytes, platelet aggregation, and sludging of blood.

• Slow rewarming (no rubbing or massage)
• Systemic antibiotics
• Anticoagulants
• Debridement of necrotic tissue only after demarcation
• No pressure or pressure dressings to the ear

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D. Bites

• The ear lobe is the most common site.
• Human bites carry greater risk of infection than animal bites (polymicrobial flora, Eikenella corrodens).

• Meticulous cleaning
• Systemic antibiotics
• Surgical repair and/or debridement

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E. Keloids and Hypertrophic Scars

• Common at earlobe piercings.
• Increased rates in African American and Hispanic populations (up to 30%).

• Intralesional steroid injection
• Surgical excision
• Pressure dressing
• Rarely radiation therapy

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IV. FOREIGN BODIES OF THE EXTERNAL EAR CANAL

• Do NOT irrigate — vegetable matter (beans, nuts) will absorb water and expand, worsening obstruction.
• Avoid blind instrumentation — may cause bleeding, swelling of the canal, or impale the foreign body through the tympanic membrane.
• Live insects: instill mineral oil or lidocaine first to immobilize/kill the insect before removal.

• Local anesthetic block (auricular block)
• Microscopic examination
• Careful instrumentation (hooks, alligator forceps, suction) under direct visualization
• Mineral oil or antibiotic solution to facilitate removal
• After removal: assess canal and TM; topical antibiotic drops if canal is traumatized

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V. INFLAMMATORY DISEASES OF THE OUTER EAR

A. Seborrheic Dermatitis and Psoriasis

• Psoriasis affects 2–5% of the population; the ear is involved in 18% of those with systemic psoriasis. The scalp and postauricular sulcus are frequently affected.
• Eczema-related external otitis is the most common dermatologic condition of the external canal; may be associated with dandruff.

• Frequent cleaning to prevent debris accumulation
• 1% hydrocortisone solution or lotion for maintenance
• Betamethasone for acute flares

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B. Acute Diffuse Otitis Externa ("Swimmer's Ear")

• Loss of the protective cerumen (wax) barrier and acidic environment (normally pH 4–5).
• Maceration from water exposure disrupts the epithelium.
• Most common organisms: Pseudomonas aeruginosa (most common), Staphylococcus aureus.

• Thorough aural toilet (suction/cleaning)
• Topical antibiotic ± corticosteroid drops (ciprofloxacin/dexamethasone or acetic acid drops)
• Wick insertion if canal severely edematous
• Analgesics; avoid water

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C. Malignant (Necrotizing) Otitis Externa

• Severe, unrelenting otalgia
• Purulent otorrhea
• Cranial nerve involvement (CN VII — facial nerve palsy most common; CN IX, X, XI via jugular foramen involvement)
• Can progress to skull base osteomyelitis, meningitis, sigmoid sinus thrombosis, and death

• Prolonged IV/oral antipseudomonal antibiotics (fluoroquinolones — ciprofloxacin; or anti-pseudomonal β-lactams for severe cases)
• Duration: 6–8 weeks minimum, guided by clinical response and gallium-67 scan
• Aggressive aural toilet
• Surgical debridement for refractory disease
• Strict glycemic control in diabetics

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D. Keratosis Obturans

• Rapid accumulation of keratin debris forming wax casts that plug the EAC.
• Causes painless erosion and expansion of the bony EAC.
• May be associated with drainage, foul odor, and secondary external otitis.
• Pathology: Chronic inflammation and poor epithelial migration.
• Treatment: Frequent cleaning; topical 1% hydrocortisone; betamethasone for acute flares.

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E. External Canal Cholesteatoma

• Keratin accumulation within the EAC associated with osteitis and bone necrosis.
• Usually occurs on the floor of the external canal.
• Commonly associated with pain and keratin invasion of bone.
• Treatment:
  • Regular cleaning; topical steroids
  • Surgical debridement of osteitic bone if needed
  • Canal wall-down mastoidectomy if extensive bone erosion is present

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F. Perichondritis

• Systemic fluoroquinolones (ciprofloxacin)
• Surgical drainage of any abscess
• Removal of infected cartilage if necrosis present

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G. Exostoses and Osteoma of the EAC

• Lamellar thickening of the bony EAC walls — associated with cold water/air exposure (common in surfers and swimmers; "surfer's ear").
• Multiple broad-based lesions, involving the anterior and posterior canal walls.
• Consequences: canal stenosis, cerumen impaction, moisture retention, recurrent OE, rarely hearing loss.
• Treatment: Canaloplasty ± skin graft when symptomatic.

• Pedunculated bone mass at the tympanosquamous or tympanomastoid suture lines.
• Usually solitary and unilateral.
• Treatment: Surgical removal if occluding the canal.

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VI. SUMMARY TABLE

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