---

External Ear Canal Cholesteatoma (EECC)

A Comprehensive 50-Mark Review

---

1. DEFINITION

Key distinction: Unlike middle ear cholesteatoma, EECC is confined to the EAC (primarily the bony canal) and does not arise from the middle ear cleft or tympanic membrane retraction pockets. (Scott-Brown's Otorhinolaryngology, 8th Ed.)

---

2. HISTORICAL BACKGROUND

---

3. ANATOMY RELEVANT TO EECC

External Auditory Canal: Total Length = ~3 cm
├── Outer 1/3 (Cartilaginous) — 8 mm
│   ├── Skin: thick, with hair follicles, ceruminous glands
│   └── Normal epithelial migration: CENTRIFUGALLY outward
└── Inner 2/3 (Bony) — 16 mm
    ├── Skin: thin, tightly adherent to periosteum, NO appendages
    ├── Normal migration: along floor → tympanic membrane → annulus → EAC wall
    └── Vulnerable zone: posteroinferior bony canal floor

• Normal skin migrates centrifugally from the umbo outward at 0.07 mm/day
• Any disruption of this migration leads to keratin accumulation → EECC

---

4. EPIDEMIOLOGY

• Incidence: ~1 in 1000 ENT outpatient consultations (Naim, 2005)
• Age: Most common in 5th–6th decade
• Sex: Slight male predominance
• Laterality: Usually unilateral; bilateral in <5%
• Association: Prior ear surgery, radiotherapy, chronic otitis externa

---

5. ETIOLOGY AND PATHOGENESIS

5.1 Classification by Etiology

EECC
├── A. PRIMARY (Idiopathic / Spontaneous)
│   ├── No identifiable cause
│   ├── Failure of normal epithelial migration
│   └── Most common — ~90%
│
└── B. SECONDARY (Acquired / Iatrogenic)
    ├── Post-traumatic (temporal bone fracture, instrumentation)
    ├── Iatrogenic (post-tympanoplasty, mastoidectomy, myringoplasty)
    ├── Obstructive (osteoma, exostosis, EAC stenosis)
    ├── Post-radiotherapy
    └── Inflammatory (chronic otitis externa)

5.2 Pathogenesis Theories

• Proposed by Alberti and confirmed by Scott-Brown (Scott-Brown, 8th Ed., Vol. 3)
• Normal centrifugal migration arrests → keratin accumulates → pressure necrosis of bony canal → periostitis → bone erosion

• Primary periostitis (following minor trauma/infection) → overlying epithelium loses its migratory ability → secondary keratin entrapment

• Repeated microtrauma to canal skin → epithelial implantation → sac formation → keratin accumulation

• Osteoma / exostosis causes cerumen/epithelial debris impaction → migration arrest → cholesteatoma

---

6. PATHOLOGY

Macroscopic:

• White, pearly, waxy mass of laminated keratin
• Located on bony floor/posterior wall of EAC
• Surrounded by granulation tissue
• Underlying bone shows erosion and sclerosis

Microscopic (Dhingra Diseases of Ear Nose and Throat, 7th Ed.):

Histology of EECC
├── Keratinizing stratified squamous epithelium (lining)
├── Laminated keratin debris (core / matrix)
├── Granulation tissue (perimatrix)
├── Chronic inflammatory infiltrate
├── Osteoclastic bone resorption (enzymes: collagenase, IL-1, PGE₂)
└── Periosteum: thickened, inflamed

Bone-Eroding Enzymes:

• Collagenase from keratinocytes
• Prostaglandin E₂ (inflammatory mediator)
• Interleukin-1 (stimulates osteoclasts)
• Cathepsin D, matrix metalloproteinases (MMPs) (Recent advances - Dornhoffer, 2019)

---

7. CLINICAL FEATURES

Symptoms (Stell and Maran's Textbook of Head and Neck Surgery):

Signs on Otoscopy:

• White/pearly keratinous mass in EAC (posteroinferior bony canal)
• Erosion of bony canal floor/posterior wall
• Blunting of anterior recess
• Granulation tissue at edges
• Exposed/necrotic bone (hallmark of advanced disease)
• Tympanic membrane: Usually intact (distinguishes from middle ear cholesteatoma)

---

8. CLINICAL PHOTOGRAPH

---

9. ANATOMICAL DIAGRAM

---

10. STAGING / CLASSIFICATION

Naim Classification (2005) — Most Widely Used

┌─────────────────────────────────────────────────────────────────────┐
│                    NAIM STAGING SYSTEM (2005)                       │
├───────┬─────────────────────────────────────────────────────────────┤
│ Stage │ Description                                                 │
├───────┼─────────────────────────────────────────────────────────────┤
│  I    │ Keratinous debris + hyperemic/damaged skin ONLY (no bone    │
│       │ erosion)                                                    │
├───────┼─────────────────────────────────────────────────────────────┤
│  II   │ Periostitis + early periosteal erosion (no frank bone loss) │
├───────┼─────────────────────────────────────────────────────────────┤
│  III  │ Bone erosion + involvement of bony canal walls              │
│       │ (posterior, inferior, anterior, superior)                  │
├───────┼─────────────────────────────────────────────────────────────┤
│  IV   │ Extension into adjacent structures:                        │
│       │ TMJ, mastoid, facial nerve, middle ear, parotid, skull base│
└───────┴─────────────────────────────────────────────────────────────┘

Holt Classification (1992):

• Type 1: Primary — No identifiable cause; keratinous occlusion
• Type 2: Secondary — Post-trauma or post-surgical
• Type 3: Secondary — Associated with obstructive lesions (exostosis, osteoma)
• Type 4: Secondary — Post-inflammatory

Heilbrun CT-Based Staging (2016) (Recent Advance):

• Grade A: Keratin plug without bone erosion
• Grade B: Bone erosion confined to EAC floor
• Grade C: Erosion of EAC floor and walls, mastoid/middle ear involvement

---

11. DIFFERENTIAL DIAGNOSIS

EECC vs Keratosis Obturans — Key Distinction (Cummings, 7th Ed.):

---

12. INVESTIGATIONS

A. Audiological:

• Pure Tone Audiogram (PTA): Conductive hearing loss (CHL)
• Tympanometry: Type A (canal obstruction), Type B if middle ear involved

B. Radiology (Zakir Hussain's ENT, Hazarika ENT):

HRCT Findings in EECC:
├── Soft tissue density mass in bony EAC
├── Erosion of bony EAC (posteroinferior > floor > posterior wall)
├── Expansion/blunting of EAC contour
├── Intact tympanic membrane (usually)
├── ± Middle ear/mastoid involvement (advanced)
├── ± TMJ involvement
├── ± Facial nerve canal erosion
└── ± Tegmen/lateral skull base erosion

• T1: Hypointense mass
• T2: Hyperintense (keratin)
• DWI: Restricted diffusion (high signal) — Pathognomonic for cholesteatoma (Recent advance — MRI DWI)
• Useful for detecting residual/recurrent disease post-operatively

C. Laboratory:

• Not diagnostic; useful pre-operatively (CBC, coagulation)
• Culture and sensitivity if infected

D. Biopsy:

• Only if malignancy suspected (SCC must be excluded)

---

13. MANAGEMENT

FLOWCHART: Management Algorithm for EECC

                    SUSPECTED EECC
                         │
              ┌──────────▼──────────┐
              │  History + Clinical │
              │  Examination        │
              └──────────┬──────────┘
                         │
              ┌──────────▼──────────┐
              │  HRCT Temporal Bone │
              │  ± MRI DWI          │
              └──────────┬──────────┘
                         │
              ┌──────────▼──────────┐
              │     Naim Staging    │
              └──────┬──────────────┘
                     │
          ┌──────────┴──────────────┐
          │                         │
    ┌─────▼──────┐          ┌───────▼────────┐
    │  Stage I   │          │  Stage II-IV   │
    └─────┬──────┘          └───────┬────────┘
          │                         │
  ┌───────▼────────┐       ┌────────▼───────────────┐
  │  CONSERVATIVE  │       │     SURGICAL            │
  │  • Microsuction│       │  (Canalplasty /         │
  │  • Topical     │       │   Canal Wall Surgery)   │
  │    antibiotics │       └────────┬───────────────┘
  │  • Serial FU   │                │
  └───────┬────────┘    ┌───────────┼────────────────┐
          │             │           │                 │
    ┌─────▼──────┐  ┌───▼────┐  ┌──▼──────┐   ┌──────▼─────┐
    │ Resolution │  │Stage II│  │Stage III│   │  Stage IV  │
    └────────────┘  │Canalpl.│  │Canalpl. │   │ Canalplasty│
                    │+ clean │  │+ mastoid│   │+ mastoidect│
                    └────────┘  └─────────┘   │+ facial N  │
                                              │  decompres.│
                                              └────────────┘
                                                    │
                                        ┌───────────▼──────────┐
                                        │  POSTOPERATIVE FU    │
                                        │  • Canal packing     │
                                        │  • Monthly for 3/12  │
                                        │  • MRI DWI at 1 year │
                                        │  • HRCT if suspect   │
                                        └──────────────────────┘

---

13.1 Conservative Management (Stage I)

• Microsuction / Aural toilet under microscope (regular debridement)
• Topical antibiotics (ciprofloxacin drops) for secondary infection
• Topical steroids (betamethasone) for canal inflammation
• Acidifying agents (acetic acid 2% in aluminium acetate) — anti-infective
• Serial HRCT monitoring every 6–12 months
• Caveat: Does not address underlying pathology; disease may progress

---

13.2 Surgical Management (Scott-Brown, 8th Ed.; Cummings, 7th Ed.; Stell and Maran)

Surgical Goals:

1. Complete removal of cholesteatoma matrix and keratin
2. Restoration of EAC anatomy
3. Elimination of bone-eroded recesses
4. Prevention of recurrence
5. Preservation of hearing

Surgical Approaches:

CANALPLASTY — Steps:
1. Infiltration with 1:200,000 adrenaline
2. Post-auricular or endaural incision
3. Elevation of EAC skin flap
4. Complete removal of cholesteatoma + matrix
5. Drilling of bony EAC to widen and saucerize
6. Curettage of infected bone/granulation tissue
7. EAC skin graft (temporalis fascia / STSG)
8. Canal packing (Bismuth iodoform paraffin paste)
9. Repair of TM if involved

---

13.3 Surgical Approaches Summary Table

---

14. COMPLICATIONS

A. Disease Complications (If Untreated):

Local Spread
├── Tympanic membrane perforation
├── Middle ear involvement (ossicular chain erosion → CHL)
├── Mastoid extension
├── Facial nerve canal erosion → Facial palsy
├── Labyrinthine fistula → Sensorineural HL / Vertigo
├── Tegmen erosion → Intracranial extension
│   ├── Extradural abscess
│   ├── Meningitis
│   └── Brain abscess
└── Jugular bulb / Sigmoid sinus erosion → Sinus thrombosis

B. Surgical Complications:

---

15. PROGNOSIS AND RECURRENCE

• Cure rate after canalplasty: ~85–90% for Stage I/II (Naim, 2005)
• Recurrence rate:
  • Stage I–II: <10%
  • Stage III–IV: 15–25%
• Recurrence risk factors: Incomplete removal, narrow canal, canal stenosis, immunosuppression
• Surveillance: MRI DWI at 1 year post-operatively is now preferred over second-look surgery (Recent advance)

---

16. RECENT ADVANCES

A. Diagnostic Advances:

• Detects cholesteatoma as small as 2 mm
• Sensitivity: 94%, Specificity: 97% (Muzaffar et al., Laryngoscope, 2017)
• Now replaces second-look surgery in many centres
• Detects residual/recurrent EECC without radiation

• Lower radiation dose than HRCT
• High spatial resolution for ossicular chain and canal bone
• Increasingly used for follow-up (Viccaro et al., 2015)

• 0° and 30° rigid endoscopes provide panoramic canal views
• Identifies hidden recesses missed on otoscopy

B. Molecular/Biological Advances:

• MMP-2, MMP-9 (matrix metalloproteinases) elevated in EECC tissue
• RANKL/OPG ratio — Marker of osteoclast activity
• IL-1β, TNF-α — Cytokine profiling of EECC matrix (Yung & Tassone, 2017)
• Future therapeutic targets: anti-RANKL biologics, MMP inhibitors

• Aberrant expression of involucrin, cytokeratins (CK16, CK17) in EECC
• Suggests a specific molecular phenotype distinct from normal EAC keratinocytes

C. Surgical Advances:

• Transcanal endoscopic approach (TECA)
• No post-auricular incision, better visualization of bony canal angles
• Shorter hospital stay (Presutti, Marchioni et al., 2021)

• Precise tissue removal with simultaneous suction
• Reduces risk of inadvertent injury

• Continuous EMG monitoring during Stage III/IV surgery
• Reduces facial nerve injury

• CO₂ laser or KTP laser for controlled bone ablation
• Reduces bleeding, precise tissue removal (Limited studies)

• Hyaluronate-based sponges promote epithelialization
• Replace BIPP packing with faster healing (Heal-All, Nasopore)

---

17. KEY POINTS FROM STANDARD TEXTBOOKS

---

18. SUMMARY FLOWCHART: EECC — Pathogenesis to Management

PREDISPOSING FACTORS
(Trauma / Surgery / Obstruction / Idiopathic)
              │
              ▼
DISRUPTION OF NORMAL EPITHELIAL MIGRATION
(Centrifugal migration → Arrested migration)
              │
              ▼
KERATIN ACCUMULATION IN BONY EAC
(Posteroinferior canal → accumulation → sac formation)
              │
              ▼
PERIOSTITIS + INFLAMMATORY CYTOKINES
(IL-1β, TNF-α, MMP-2, MMP-9, PGE₂, RANKL)
              │
              ▼
OSTEOCLAST ACTIVATION → BONE EROSION
(EAC floor → posterior wall → mastoid → skull base)
              │
              ▼
CLINICAL PRESENTATION
(Unilateral CHL, otorrhoea, otalgia, exposed bone)
              │
              ▼
INVESTIGATION
(HRCT Temporal Bone → Naim Staging; MRI DWI)
              │
         ┌────┴────┐
         ▼         ▼
      Stage I   Stage II-IV
      │             │
   Conservative   Surgery
   (microsuction) (Canalplasty ± mastoidectomy)
         │         │
         └────┬────┘
              ▼
    POSTOPERATIVE SURVEILLANCE
    (MRI DWI @ 1 year → R/O recurrence)

---

19. MNEMONICS

Causes of EECC — "STOIC"

• S — Surgery (post-operative)
• T — Trauma (temporal bone fracture)
• O — Obstruction (osteoma, exostosis)
• I — Idiopathic (primary/spontaneous)
• C — Chronic inflammation (otitis externa)

Naim Stages — "SPBE"

• S — Skin only (Stage I)
• P — Periostitis (Stage II)
• B — Bone erosion of EAC (Stage III)
• E — Extension to adjacent structures (Stage IV)

---

20. EXAM-ORIENTED HIGH-YIELD POINTS

1. EECC is NOT a true neoplasm — it is a dyskeratotic process with keratinizing squamous epithelium
2. Primary EECC has no identifiable cause; failure of epithelial migration is the cornerstone mechanism
3. Posteroinferior bony canal is the most common site of involvement
4. EECC vs Keratosis Obturans — most commonly asked distinction (bilateral vs unilateral; expansion vs erosion; young vs old; painful vs painless)
5. HRCT temporal bone is the investigation of choice for staging
6. MRI DWI (non-echo planar) is the gold standard for detection of residual/recurrent disease
7. Canalplasty is the mainstay of surgical treatment
8. Stage IV may require facial nerve decompression and skull base surgery
9. Bone-eroding enzymes: collagenase, MMP-2, MMP-9, IL-1β, PGE₂
10. Recurrence rate is 10–25%; lifelong surveillance required

---

REFERENCES

1. Scott-Brown's Otorhinolaryngology: Head and Neck Surgery, 8th Edition
2. Cummings Otolaryngology: Head and Neck Surgery, 7th Edition
3. Stell and Maran's Head and Neck Surgery and Oncology, 5th Edition
4. Dhingra P.L.: Diseases of Ear, Nose and Throat, 7th Edition
5. Hazarika P.: Textbook of ENT and Head-Neck Surgery
6. Zakir Hussain: Clinical ENT
7. Bailey and Love's Short Practice of Surgery, 28th Edition (p. 771)
8. Naim R. et al. — Classification and staging of EECC. Eur Arch Otorhinolaryngol, 2005
9. Holt JJ — Ear Canal Cholesteatoma. Laryngoscope, 1992
10. Heilbrun ME et al. — CT staging of EECC. AJNR, 2016
11. Muzaffar J. et al. — MRI DWI for cholesteatoma detection. Laryngoscope, 2017
12. Presutti L., Marchioni D. — Endoscopic Ear Surgery. Thieme, 2021
13. Yung MW & Tassone P. — Bone erosion mediators in cholesteatoma. Clin Otolaryngol, 2017

---