Congenital and Acquired Stenosis of the External Ear Canal

ANATOMY REVIEW (Brief)

PART I: CONGENITAL STENOSIS OF THE EXTERNAL EAR

1. Definition and Spectrum

• Membranous - soft tissue obstruction only
• Bony - osseous narrowing or plate (atretic plate)
• Mixed - combination of both

2. Embryology and Etiology

• Chromosomal aberrations and multifactorial inheritance
• Autosomal dominant and recessive patterns
• Haploinsufficiency of the HOXA2 gene - associated with bilateral microtia and hearing loss
• 18q deletion (de Grouchy or 18q deletion syndrome) - associated with bilateral aural atresia
• Known teratogens: retinoic acid, thalidomide, cadmium, vincristine, colchicine
• Possible role of tissue ischemia from obliteration of the stapedial artery in utero
• Associated with increasing maternal age (some studies)

3. Epidemiology

• Incidence: 0.83 to 17.4 per 10,000 live births
• Right-sided: 58%, Left-sided: 32%, Bilateral: 9%
• Male:Female ratio = 63:37
• Familial recurrence: 4.9% (immediate family), 10.3% (extended family)

4. Associated Syndromes and Deformities

• Facial asymmetry: 36.5%
• 7th nerve weakness: 15.2%
• Cleft lip/palate: 4.3%
• Urogenital defects: 4%
• Cardiovascular malformations: 2.5%

5. Schuknecht Classification of Congenital Aural Atresia

6. Clinical Features

• Conductive hearing loss - usually maximal (approximately 60 dB) because the ossicular chain is often fused or malformed
• Normal cochlear (sensorineural) function in the vast majority
• Abnormal or absent auricle (microtia)
• Inability to examine the ear canal and tympanic membrane
• Cerumen accumulation and impaction
• Recurrent otitis media that may go undetected
• Canal cholesteatoma - occurs in ~1 in 5 ears (20%) with CEACS; risk significantly higher than in complete CAA

A child with EAC diameter 2.5 mm or more at birth, managed every 6 months, may outgrow the problem by age 4-5 years. Canal cholesteatoma is much more likely if diameter is 2 mm or less.

7. Investigation

• Severity and type of atresia
• Size and pneumatization of the middle ear cleft
• Appearance of ossicles - especially stapes superstructure and oval window
• Course of the facial nerve (the posterior genu is often more anteriorly and laterally positioned than normal - at risk during surgery)
• In oval window atresia: facial nerve tends to lie at the level of the atretic oval window

8. Jahrsdoerfer Grading Scale (CT-based candidacy for atresiaplasty)

• Score ≥7: Favorable for atresiaplasty
• Score <6: Unfavorable for atresiaplasty
• Middle ear volume >305 mm³ is predictive of better hearing outcomes

9. Management of Congenital EAC Stenosis

A. Hearing Habilitation (Urgent in Bilateral Cases)

• Bone conduction hearing device (BCHD) on a soft Velcro band - should be placed in early infancy once normal bone conduction confirmed on ABR
• Options include: BAHA Connect (percutaneous), BAHA Attract/Sophono (transcutaneous), BoneBridge (active bone conduction implant)
• FDA minimum age for implantable devices: 5 years (BAHA, Ponto, Sophono)
• Unilateral CAA: BCHD benefit is more controversial

B. Conservative Management for CEACS

• Regular otolaryngology review (every 6 months) for examination and cleaning
• Canal diameter ≥2.5 mm: likely to outgrow by age 4-5 years without surgery
• If cholesteatoma is suspected (otorrhea, odor, stenosis with debris): CT urgently; surgery indicated

C. Surgical Management: Atresiaplasty

• If Medpor repair: atresia surgery precedes Medpor
• If autologous rib graft: atresiaplasty follows rib graft reconstruction

1. Endaural approach (Lempel) - for CEACS; approaches stenotic EAC lateral to medial
2. Standard anterior approach (Jahrsdoerfer) - canal drilling parallels stenotic bony canal, hugs tegmen to identify ossicular chain; fascia underlay graft + skin graft + wide meatoplasty

• Drilling along the atretic plate guided by tegmen and facial nerve
• Liberation of ossicles
• Fascia graft (underlay technique medial to native TM)
• Skin graft lining canal
• Wide meatoplasty

• EAC stenosis (most common complication; 0-25%) - most common reason for revision
• Facial nerve injury: 0-7%
• SNHL: 0-7.5%
• Lateralization of the tympanic membrane (0-18%)
• Persistent/delayed conductive hearing loss
• Ossicular refixation
• New bone growth (especially during puberty)
• Mucosalization of the skin graft

• Triamcinolone injection into meatal skin
• Pedicled full-thickness skin graft lining the meatus
• Wicks, stents, molds (for up to 6 months)

PART II: ACQUIRED STENOSIS OF THE EXTERNAL EAR

1. Definition

2. Etiology and Causes

A. Inflammatory / Infective Causes

• Chronic otitis externa - most common cause; recurrent infection leads to fibrosis and skin thickening
  • Pathogens: Staphylococcus, Pseudomonas, fungal (otomycosis)
  • Dermatological conditions: seborrheic dermatitis, psoriasis (affects 2-5% of population; ear involved in 18%), eczema
  • Symptoms: itching, weeping, dry/scaly/fissured skin, crusting, canal stenosis
• Lichen planus of the EAC (rare, more common in women)
• Necrotizing (malignant) otitis externa - progressive osteonecrosis; predisposed by diabetes, immunosuppression

B. Traumatic Causes

• Temporal bone fractures (especially longitudinal fractures involving the EAC)
  • Fracture line traps epithelium medial to the stenosis leading to canal cholesteatoma
  • Canal stenosis progresses if not managed early
• Burns or chemical trauma
• Iatrogenic - post-surgical stenosis (e.g., after atresiaplasty - most common surgical complication)

C. Bony Causes (Luminal Narrowing)

• Lamellar thickening of bone of the EAC; most common cause of bony stenosis
• Associated with cold air/water exposure (cold water diving, surfers - "surfer's ear")
• Usually involve anterior and posterior canal walls
• Bilateral and multiple
• Can cause cerumen impaction, retention of moisture/skin, rarely hearing loss
• Treatment: canaloplasty and possible skin graft

• Pedunculated bone mass developing along tympanosquamous and tympanomastoid suture lines
• Usually unilateral, solitary
• Typically medial and may be multiple
• Occluding osteoma requires surgical removal

D. Neoplastic Causes

• Squamous cell carcinoma, basal cell carcinoma (most common malignancies of EAC)
• Adenoid cystic carcinoma, ceruminal gland adenocarcinoma
• Present as ulcerated or nodular lesions with chronic bloody otorrhea and deep-boring otalgia
• Treatment: temporal bone resection + postoperative radiation

E. Miscellaneous

• Keratosis obturans - accumulation of keratin debris causing canal expansion (different from stenosis but related condition)
• Post-radiation change
• Bisphosphonate-related osteonecrosis of the EAC

3. Pathological Effects of Acquired Stenosis

• Cerumen and debris accumulation
• Conductive hearing loss
• Chronic infection and otorrhea
• Canal cholesteatoma - most important complication; a lateral stenosis should NEVER be allowed to persist even if benign in appearance, because of the very high probability of cholesteatoma formation
• Difficulty in examining the tympanic membrane

4. Clinical Features

• Progressive conductive hearing loss
• Recurrent or chronic otorrhea
• Itching, pain (otalgia)
• Sensation of fullness in the ear
• Visible narrowing on otoscopy; tympanic membrane may not be visualized

5. Investigations

• Otoscopy and microscopic examination
• Audiometry (pure tone audiogram) - degree of conductive hearing loss
• HRCT temporal bone - to assess extent of stenosis, bony vs. soft tissue, middle ear status, cholesteatoma formation
• Biopsy if malignancy suspected

6. Treatment of Acquired EAC Stenosis

A. Conservative / Medical Management

• Treatment of underlying cause (antibiotics, antifungals, topical steroids)
• Regular cleaning and debridement
• For inflammatory stenosis: 1% hydrocortisone lotion or betamethasone drops
• Dilation with Otowicks saturated with non-ototoxic antibiotic drops (replaced every few days) - for early/soft stenosis after trauma
• After dilation: Merocel sponge insertion to maintain lumen
• Custom-vented ear mold throughout the day for 3-6 months after severe canal injuries

B. Surgical Management: Canaloplasty

• Stenosis is complete and dilation is not possible
• Bony stenosis (exostoses, osteoma)
• To prevent or treat cholesteatoma

1. Vascular strip incisions made as far medially as safe and practicable
2. Post-auricular incision made
3. Vascular strip elevated out of the canal
4. Mass of scar tissue elevated from posterior canal wall until middle ear space entered
5. Posterior and anterior fibrous stenotic tissue excised (drum remnant preserved if possible)
6. Canal enlarged with drill until air cells visible through bone
7. Drum and canal grafted with fascia; canal filled with ointment

• Canaloplasty with diamond burr drilling of bony protuberances
• Skin graft to resurface the canal
• Meatal widening

• Triamcinolone injection into meatal skin to prevent re-stenosis
• Stenting with Merocel wick or custom ear mold for months after surgery
• Regular follow-up and cleaning essential (the reconstructed canal is not self-cleaning)

7. Complications if Left Untreated

• Progressive deafness
• Chronic otitis externa
• External canal cholesteatoma - with bone erosion and potential for:
  • Facial nerve paralysis
  • Labyrinthitis / SNHL
  • Intracranial complications (rare)
• Difficulty managing middle ear disease

Summary Comparison Table

• Cummings Otolaryngology Head and Neck Surgery (7th ed.) - Chapters 197, 138, 137
• Shambaugh Surgery of the Ear - Chapter 22 (Acquired EAC stenosis and canaloplasty)
• Scott-Brown's Otorhinolaryngology Head & Neck Surgery Vol. 2
• K.J. Lee's Essential Otolaryngology
• Grainger & Allison's Diagnostic Radiology