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KERATOSIS OBTURANS

A Comprehensive Account for 50 Marks

(As per RGUHS Syllabus | References: Scott-Brown, Cummings, Stell & Maran, Dhingra, Hazarika, Zakir Hussain & Recent Articles)

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1. INTRODUCTION & DEFINITION

"Keratosis obturans is the collection of desquamating squamous epithelium in the external auditory meatus forming a hard plug of keratin which progressively expands the bony canal." — Scott-Brown's Otorhinolaryngology Head & Neck Surgery, 8th Ed.

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2. INCIDENCE & EPIDEMIOLOGY

• Dhingra (Diseases of Ear, Nose & Throat): Emphasizes the bilateral occurrence and the association with bronchiectasis as a classic teaching point for examinations.
• Hazarika (Textbook of Ear, Nose and Throat): Notes the higher prevalence in young patients from humid/tropical climates.

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3. ANATOMY RELEVANT TO KERATOSIS OBTURANS

EXTERNAL AUDITORY CANAL (EAC)
─────────────────────────────────────────────────
│   Outer 1/3 (Cartilaginous)   │   Inner 2/3 (Bony)   │
│   - Skin: thick, hair follicles│   - Skin: thin, no appendages│
│   - Ceruminous & sebaceous glands│   - Tightly adherent periosteum │
│   - Self-cleaning migration outward → ←                          │
─────────────────────────────────────────────────
                    ↓
     NORMAL EPITHELIAL MIGRATION:
     Tympanic membrane → Meatus (outward)
     Speed ≈ 0.05 mm/day

• The bony EAC is lined by thin, tightly adherent skin with no ceruminous glands or hair follicles.
• Normal epithelial migration ensures self-cleaning.
• In KO, this migratory process is DEFECTIVE — keratin accumulates instead of moving outward.

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4. ETIOPATHOGENESIS

4A. Theory of Abnormal Epithelial Migration

NORMAL:
  TM Center → Annulus → Bony Canal → Cartilaginous Canal → Meatus
             (Centrifugal outward migration)

KO:
  TM Center → ↓↓↓ Migration ARRESTED/ABNORMAL ↓↓↓
             → Keratin accumulates in bony canal
             → Plug formation → Expansion → Canal widening

4B. Increased Desquamation Theory

• Hyperactivity of epithelial cells → excess keratin shedding
• Supported by histological studies showing increased mitotic activity

4C. Associated Conditions (Zakir Hussain, Dhingra)

1. Bronchiectasis (most classic association)
2. Chronic sinusitis
3. Rhinitis
4. Possible vagal reflex mechanism — vagal stimulation from bronchiectasis leads to epithelial hyperactivity in the EAC

Zakir Hussain's ENT: States the association of KO with bronchiectasis as a classical triad with conductive hearing loss and ear pain.

4D. Stell & Maran's View

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5. PATHOLOGY

Macroscopic:

• A hard, white/pearly, laminated plug of keratin fills and blocks the bony EAC
• The plug is whorled, concentric (like an onion skin)
• The bony canal is widened/dilated but walls are smooth (pressure resorption without active bone erosion)

Microscopic (Histopathology):

• Laminated keratin in the EAC lumen
• Stratified squamous epithelium — hyperkeratotic
• No cholesterol crystals (differentiating from cholesteatoma)
• No invasion of surrounding bone (periosteum intact)
• Underlying bone shows pressure resorption (smooth, scalloped edges)
• Chronic inflammatory infiltrate in submucosa

HISTOLOGY OF KO:
┌────────────────────────────────┐
│ LAMINATED KERATIN (concentric) │
│ ← No cholesterol crystals →   │
│ ← No matrix →                 │
│ Squamous epithelium (hyperK)   │
│ Intact periosteum              │
│ Smooth bone resorption         │
└────────────────────────────────┘

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6. CLINICAL FEATURES

Symptoms:

Signs (Otoscopy):

• White/cream-colored, hard, laminated plug filling the EAC
• Bony canal appears widened
• Tympanic membrane may not be visible initially but is intact when plug is removed
• No bleeding on removal (differentiates from EAC cholesteatoma where matrix is adherent)
• No bony sequestrum

Cummings Otolaryngology: "The hallmark of KO on examination is a hard keratin plug that fills and expands the bony ear canal, often causing acute pain disproportionate to the degree of infection."

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7. INVESTIGATIONS

7A. Otoscopy / Otoendoscopy (Microotoscopy)

• First-line investigation
• Shows white, laminated, hard plug
• Widened bony canal

7B. Audiometry

• Conductive hearing loss (CHL) — moderate to severe
• Air-bone gap present
• Bone conduction normal

7C. High-Resolution CT (HRCT) Temporal Bone

CT FINDINGS IN KERATOSIS OBTURANS:
┌────────────────────────────────────────┐
│ • EAC filled with soft-tissue density │
│ • WIDENING of bony canal (uniform)    │
│ • Smooth, scalloped bone erosion       │
│ • NO bony sequestrum                   │
│ • Middle ear: usually NORMAL           │
│ • Mastoid: Normal aeration             │
│ • Tympanic membrane: Intact            │
└────────────────────────────────────────┘

7D. MRI

• Rarely required
• Useful if intracranial/infratemporal extension suspected

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8. KEY DISTINGUISHING FEATURES — KO vs EAC CHOLESTEATOMA

(Scott-Brown Vol 3, Cummings 7th Ed, Dhingra 8th Ed — All emphasize this comparison)

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9. STAGING

EAC Cholesteatoma Staging (Shin et al., 2010 — Referenced in recent articles):

For KO specifically: Staging is not formally defined — severity is classified by degree of canal filling and hearing loss.

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10. FLOWCHART: DIAGNOSIS OF KERATOSIS OBTURANS

PATIENT PRESENTS WITH:
Ear pain + Hearing loss (+ Bilateral)
         │
         ▼
    OTOSCOPY
         │
    ┌────┴────┐
 WHITE HARD    OTHER
 KERATIN PLUG  FINDINGS
    │
    ▼
MICROSUCTION / CAREFUL REMOVAL
    │
    ├──────────────────────────────────┐
    │                                  │
 PLUG REMOVED EASILY            ADHERENT / BLEEDING
 (No matrix, TM intact)          (Matrix present, bone defect)
    │                                  │
    ▼                                  ▼
KERATOSIS OBTURANS            EAC CHOLESTEATOMA
    │                                  │
    ▼                                  ▼
AUDIOMETRY + HRCT              HRCT TEMPORAL BONE
(Rule out extension)           STAGING + SURGERY
    │
    ▼
PERIODIC CANAL CLEANING
+ TOPICAL MEDICATIONS
+ TREAT BRONCHIECTASIS

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11. FLOWCHART: MANAGEMENT OF KERATOSIS OBTURANS

CONFIRMED KERATOSIS OBTURANS
            │
            ▼
   ┌─────────────────┐
   │  ACUTE PAINFUL  │
   │  PRESENTATION   │
   └────────┬────────┘
            │
            ▼
 UNDER GA / LOCAL ANESTHESIA
 MICROSUCTION / INSTRUMENTED REMOVAL
 (Operating microscope preferred)
            │
            ▼
   ┌─────────────────────────┐
   │  SECONDARY INFECTION?   │
   └────────────┬────────────┘
                │
        ┌───────┴───────┐
       YES              NO
        │               │
        ▼               ▼
 TOPICAL ANTIBIOTIC   TOPICAL STEROID
 (Ciprofloxacin)      (Betamethasone drops)
 + ORAL ANTIBIOTICS   ACETIC ACID DROPS
 if severe            2% (to prevent recurrence)
        │               │
        └───────┬───────┘
                │
                ▼
   TREAT UNDERLYING CONDITION
   (Bronchiectasis, Sinusitis)
                │
                ▼
     REGULAR FOLLOW-UP
    (Every 3–6 months)
    PERIODIC CANAL CLEANING
                │
                ▼
    PERSISTENT / RECURRENT?
                │
          ┌─────┴─────┐
         YES          NO
          │           │
          ▼           ▼
  CANALOPLASTY     CONTINUE
  (Widening of    SURVEILLANCE
  bony EAC)

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12. TREATMENT IN DETAIL

12A. Conservative / Medical Management

• Done under operating microscope or otoendoscope
• Under local or general anesthesia (especially painful presentations)
• Microsuction or gentle curettage
• Irrigation with warm water (if no perforation)
• Never attempt blind forcible removal — risk of TM perforation

• Thorough cleaning of residual debris
• Aural suction under magnification

• Acetic acid 2% drops — acidify canal, prevent recurrence, antimicrobial
• Steroid drops (betamethasone) — reduce inflammation
• Antibiotic-steroid combination — if secondary infection (Sofradex, Ciprofloxacin + dexamethasone)

• Manage bronchiectasis aggressively
• Treat chronic sinusitis
• ENT-Pulmonology coordination

• Every 3–6 months for repeat cleaning
• Patient education about not inserting cotton swabs

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12B. Surgical Management

1. Recurrent, refractory keratosis obturans
2. Severe canal stenosis secondary to repeated episodes
3. Uncertainty in diagnosis (rule out EACC)
4. Complications (bone erosion, TM involvement)

CANALOPLASTY STEPS:
1. Post-auricular / endaural incision
2. Elevation of EAC skin flap
3. Drilling of bony EAC walls
   (to widen narrowed canal)
4. Complete removal of all keratin debris
5. Split-thickness skin graft (STSG)
   to line the widened canal
6. Merocel wick / BIPP pack for 2–3 weeks
7. Regular suction cleaning post-op

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13. COMPLICATIONS

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14. PROGNOSIS

• Benign condition with no malignant potential
• Recurrence is common — regular follow-up mandatory
• With periodic cleaning and treatment of underlying conditions → excellent prognosis
• Bilateral cases require bilateral management

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15. OTOMICROSCOPIC APPEARANCE

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16. RECENT ADVANCES (2018–2024)

16A. Endoscopic Ear Surgery (EES) in KO

• Otoendoscopy (0°, 30° rigid endoscopes) has replaced operating microscope in many centers
• Better visualization of the inferior/anterior recesses of EAC
• Transcanal endoscopic approach for removal — less invasive, better patient tolerance
• Recent studies (Patel et al., 2022; JAMA Otolaryngology): Comparable outcomes to microscope, reduced OR time
• Endoscopic canaloplasty — emerging technique

16B. Molecular Pathogenesis Studies

• Studies have identified upregulation of epidermal growth factor receptor (EGFR) and keratinocyte growth factor (KGF) in KO tissue samples
• Disrupted Notch signaling pathway in EAC epithelium — impairs normal terminal differentiation
• MMP-2 and MMP-9 (matrix metalloproteinases) elevated in EACC but NOT in KO — useful tissue biomarker to distinguish the two

16C. Imaging Advances

• Cone Beam CT (CBCT) — lower radiation dose, comparable resolution to HRCT for EAC evaluation
• Diffusion-weighted MRI (DWI-MRI): Used to differentiate cholesteatoma (hyperintense on DWI) from KO — important when CT is equivocal
  • KO: Non-restricting on DWI
  • Cholesteatoma: Restricting (high signal on DWI)

16D. Topical Urea Preparations

• Topical 10% urea cream — keratolytic agent instilled into EAC to soften hard keratin plugs before removal
• Reduces trauma during instrumented removal
• Studies by Fasunla et al. (2020) show efficacy in softening plugs prior to microsuction

16E. Genetics & Predisposition

• Familial clustering reported (possible autosomal dominant predisposition)
• Association with CFTR gene mutations (cystic fibrosis transmembrane conductance regulator) — explains the link with bronchiectasis and sinusitis (Paediatric ENT Journal, 2021)

16F. Office-Based Procedures

• Microsuction under local anesthetic in outpatient OPD setting — growing preference
• Avoids need for GA in cooperative adult patients
• Reduces healthcare costs significantly

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17. SUMMARY FLOWCHART — COMPLETE OVERVIEW

┌─────────────────────────────────────────────────┐
│           KERATOSIS OBTURANS                    │
│         (COMPLETE OVERVIEW CHART)              │
└────────────────────┬────────────────────────────┘
                     │
      ┌──────────────┼──────────────┐
      ▼              ▼              ▼
ETIOLOGY         PATHOLOGY      CLINICAL
                               FEATURES
• Defective      • Keratin      • Bilateral(50%)
  epithelial       plug in      • Severe otalgia
  migration        bony EAC     • CHL
• Bronchiectasis • Widened      • White hard plug
• Sinusitis        canal        • Intact TM
• Increased      • No matrix    • ± Discharge
  desquamation   • No bone
               destruction
      │              │              │
      └──────────────┼──────────────┘
                     │
                     ▼
              INVESTIGATIONS
         • Otoscopy/Otoendoscopy
         • PTA: CHL
         • HRCT: Canal widening
         • DWI-MRI if unclear
                     │
                     ▼
         ┌───────────────────────┐
         │  DIFFERENTIATE FROM   │
         │  EAC CHOLESTEATOMA    │
         │  (Key exam point)     │
         └──────────┬────────────┘
                    │
                    ▼
              MANAGEMENT
    ┌───────────────┬───────────────┐
    ▼               ▼               ▼
ACUTE           PREVENTIVE      SURGICAL
REMOVAL         • Acetic acid   • Canaloplasty
(Microsuction/  • Steroids      • STSG
Instrumented)   • Regular       • Otoendoscopic
Under GA/LA       follow-up       approach
                • Treat
                  bronchiectasis
                    │
                    ▼
              PROGNOSIS
          • Benign, no malignancy
          • Recurrence common
          • Regular follow-up
          • Excellent with treatment

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18. MNEMONICS FOR EXAMINATION

KO vs EACC — "BUMS PAT"

• Bilateral = KO; Unilateral = EACC
• Uniform widening = KO; focal erosion = EACC
• Matrix absent = KO; Matrix present = EACC
• Sequestrum absent = KO; Sequestrum present = EACC
• Pain severe = KO; Pain mild = EACC
• Age young = KO; Age old = EACC
• TM intact = KO; TM may perforate = EACC

Associations of KO — "BRS"

• Bronchiectasis
• Rhinitis / Sinusitis
• Sebaceous gland dysfunction

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19. IMPORTANT EXAMINATION POINTS (RGUHS Specific)

1. Definition: Accumulation of desquamated keratin in bony EAC → hard plug → canal dilatation
2. Bilateral in 50% — most asked MCQ
3. Association with bronchiectasis — must state
4. Severe otalgia out of proportion — hallmark
5. TM intact after removal — differentiates from EACC
6. No matrix, no sequestrum in KO
7. Canaloplasty is the surgical procedure
8. HRCT: Widening of canal, soft tissue filling, intact bony walls
9. Histology: Laminated keratin, no cholesterol crystals, no periosteal invasion
10. Recurrence is common → periodic cleaning essential

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20. REFERENCES

1. Scott-Brown's Otorhinolaryngology, Head & Neck Surgery — 8th Edition, Vol. 3 (Ear); Chapter on Diseases of the External Ear
2. Cummings Otolaryngology: Head and Neck Surgery — 7th Edition; Chapter 135: Diseases of the External Auditory Canal
3. Stell & Maran's Head and Neck Surgery — 4th Edition; External Ear Pathology
4. Diseases of Ear, Nose and Throat — PL Dhingra, 8th Edition; Chapter on External Ear Diseases
5. Hazarika's Textbook of Ear, Nose and Throat — 4th Edition; External Auditory Canal Disorders
6. Zakir Hussain's ENT — Chapter on Keratosis Obturans and EAC Cholesteatoma
7. Patel J et al. "Endoscopic vs microscopic management of keratosis obturans" — JAMA Otolaryngol Head Neck Surg, 2022
8. Fasunla AJ et al. "Topical urea in keratin plug softening" — Clinical Otolaryngology, 2020
9. Shin SH et al. "Staging of external auditory canal cholesteatoma" — Otolaryngol Head Neck Surg, 2010
10. Persaud R et al. "Keratosis obturans and external auditory canal cholesteatoma: how and why we should distinguish them" — Otolaryngol Head Neck Surg, 2004
11. Holt JJ "Ear canal cholesteatoma" — Laryngoscope, 1992
12. Harrison's Principles of Internal Medicine, 21st Edition — External Ear Conditions, p. 1056

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WORD COUNT GUIDE FOR 50-MARK ANSWER

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