Tympanic Membrane Perforation — Classification

1. By Location (Most Clinically Important)

A. Central Perforation

• Involves only the pars tensa; the annulus (fibrous ring) is intact on all sides
• Does not reach the bony canal margin
• Typically caused by acute otitis media (AOM) or trauma
• Generally safe — lower risk of cholesteatoma
• Located in any quadrant of the pars tensa (anterior, posterior, inferior, or subtotal)

B. Marginal Perforation

• Reaches the annulus — the fibrous ring is disrupted
• The edge of the perforation abuts the bony canal wall
• Higher risk of cholesteatoma because squamous epithelium can migrate into the middle ear through the disrupted annular margin
• Most dangerous when in the posterosuperior quadrant (close to ossicular chain, facial nerve)

C. Attic (Pars Flaccida) Perforation

• Located in the pars flaccida (above the notch of Rivinus, superiorly)
• The pars flaccida is less rigid and lacks the fibrous layer of the pars tensa
• Strongly associated with primary acquired cholesteatoma — keratin debris accumulates as the membrane retracts into the epitympanum
• Even a small perforation here carries significant pathological significance

2. By Aetiology

3. By Size

• Loss of the areal ratio between TM and oval window
• Disruption of the catenary lever effect
• Sound reaching both windows simultaneously (phase cancellation)

4. By Chronicity

• Acute — < 3 months duration; high rate of spontaneous healing
• Chronic — > 3 months; unlikely to heal without surgical intervention; associated with COM

5. Safe vs. Unsafe Perforation (Classic ENT Distinction)

Clinical Images

Key Clinical Pearls

• Posterosuperior quadrant perforations — even if seemingly small — warrant urgent ENT referral due to proximity to the incudostapedial joint, facial nerve canal, and higher cholesteatoma risk
• Attic perforations can be deceptively small on otoscopy but harbour extensive cholesteatoma medially
• Successful myringoplasty/tympanoplasty depends critically on Eustachian tube function; ongoing dysfunction (OME, negative middle ear pressure in the contralateral ear) predicts poorer outcomes
• Spontaneous healing rates: traumatic > AOM-related > COM-related perforations

Cholesteatoma

Definition

Classification

1. Congenital Cholesteatoma

• Arises from retained embryonic keratinizing epithelial rests within the middle ear — specifically from an epidermoid formation (Michaels' epidermoid) in the anterior tympanum that normally involutes by 33 weeks' gestation
• Appears as a white cystic structure medial to an intact tympanic membrane, without prior history of otitis media, perforation, or ear surgery
• More common in children; bilateral cases reported; possible genetic contribution

Congenital cholesteatoma: white, cystic mass visible behind an intact tympanic membrane

2. Acquired Cholesteatoma

A. Primary Acquired (Pars Flaccida / Attic Type)

• Arises from a retraction pocket of the pars flaccida due to chronic negative middle ear pressure (Eustachian tube dysfunction)
• Pocket deepens into the epitympanum → trapped keratin cannot migrate out → cholesteatoma forms
• Classic appearance: defect adjacent to the posterosuperior TM / attic with white keratin debris and scutum erosion
• Associated with cleft palate and underdeveloped mastoid pneumatization

Primary acquired cholesteatoma: attic retraction pocket with keratin debris, eroded scutum

B. Secondary Acquired (Pars Tensa / Marginal Type)

• Keratinizing epithelium migrates through an existing perforation (usually marginal) into the middle ear
• More commonly associated with COM and longstanding TM perforations
• Often presents with a mass at the margin of a perforation

Pathogenesis Theories (Acquired)

Clinical Features

• Slowly progressive conductive hearing loss
• Chronic foul-smelling otorrhea (anaerobic infection of keratin debris)
• May be asymptomatic initially
• Vertigo, SNHL (labyrinthine fistula)
• Facial nerve palsy (erosion of bony fallopian canal — tympanic segment most vulnerable)
• Headache, meningismus (intracranial extension)

• Attic/posterosuperior defect with white keratin debris
• Aural polyp = granulation tissue at the eroding cholesteatoma margin — should be considered cholesteatoma until proven otherwise
• White mass behind intact TM (congenital)

Bone Erosion Mechanism

• RANKL/RANK axis drives osteoclast recruitment
• Enzymes elaborated: acid phosphatase, collagenase, cathepsins, matrix metalloproteinases (MMPs)
• Intermittent osteoclastic resorption explains why some temporal bone specimens show no active erosion

1. Scutum (lateral attic wall) — earliest sign
2. Ossicular chain — incus long process most common; causes conductive HL
3. Tegmen tympani (roof) → intracranial extension
4. Lateral semicircular canal → labyrinthine fistula, vertigo
5. Facial nerve canal (tympanic segment) → facial palsy
6. Sigmoid sinus → lateral sinus thrombosis

Imaging

• Soft tissue density in attic/mastoid with bony erosion
• Scutum erosion (classic sign)
• Ossicular chain destruction
• Labyrinthine involvement, tegmen dehiscence
• Essential for preoperative planning and all revision/complex cases

Axial and coronal CT of left attic cholesteatoma: eroded incus (arrow) and scutum (arrowhead)

• Sensitivity and specificity ~94% for detecting cholesteatoma
• Bright signal on DWI + low ADC = true cholesteatoma
• Increasingly used for postoperative surveillance to detect residual/recurrent disease without second-look surgery

Complications

Management

Surgical Approach Options:

Key Pearls

• Cholesteatoma in 36% of perforated ears vs. 4% of non-perforated ears in COM temporal bones
• An aural polyp = cholesteatoma until proven otherwise
• Poorer Eustachian tube function → greater risk of recurrence post-repair
• Underdeveloped mastoid pneumatization is near-universal in both acquired and congenital cholesteatoma
• In children, even stage IV congenital cholesteatoma carries 67% residual disease — second-look is essential
• Facial nerve palsy from cholesteatoma = surgical emergency