Unsafe Chronic Suppurative Otitis Media (CSOM)

Definition & Terminology

Classification of CSOM

Cholesteatoma: Structure & Composition

• An outer matrix of keratinizing squamous epithelium
• A perimatrix (fibrous subepithelial layer rich in inflammatory cells)
• Keratin debris (desquamated squames) at the centre

Types

1. Congenital Cholesteatoma

• Behind an intact tympanic membrane with no prior otitis or surgery
• Appears as white mass anteromedial to malleus

2. Primary Acquired Cholesteatoma (most common unsafe CSOM)

• Arises from retraction pocket of pars flaccida (attic retraction) due to Eustachian tube dysfunction
• Also called attic/epitympanic cholesteatoma

3. Secondary Acquired Cholesteatoma

• Keratinizing epithelium migrates through a pre-existing perforation of pars tensa into the middle ear

Pathogenesis

A. Retraction Pocket / Invagination Theory (most accepted)

B. Epithelial Invasion (Migration) Theory

C. Basal Cell Hyperplasia Theory

D. Mucosal Traction Theory

Mechanism of Bone Erosion

• Historically attributed to pressure necrosis — now refuted (cholesteatoma pressure ~1.3–11.9 mm Hg, well below capillary perfusion pressure of ~25 mm Hg)
• Current understanding: osteoclast-mediated resorption activated by inflammatory signalling
• The cholesteatoma perimatrix expresses RANKL (receptor activator of NF-κB ligand) on stromal cells and activated T-cells → triggers osteoclastogenesis
• Osteoclasts secrete acid phosphatase, collagenase, and acid proteases into the resorption lacunae
• The endochondral bone of the otic capsule is more resistant than the intramembranous bone of the middle ear and mastoid
• Enzymes involved include cathepsin-like proteases active at pH 4.0

Clinical Features

Symptoms

• Otorrhoea: scanty but offensive/foul-smelling (anaerobic bacteria in keratin matrix)
• Hearing loss: progressive conductive, occasionally mixed or sensorineural if labyrinth eroded
• Aural polyp: infected cholesteatoma may present as a bleeding polyp
• Otalgia: usually absent unless complicated
• Symptoms of complications (see below)

Signs (Otoscopy/Microscopy)

• Attic perforation or retraction pocket in the posterosuperior quadrant/pars flaccida
• Scutum erosion (lateral attic wall)
• Keratin/epithelial debris or "pearly white" mass within the retraction
• Granulation tissue or aural polyp obscuring view
• Crusting may mask the underlying pathology — thorough canal débridement is mandatory

Investigations

Complications

Extracranial / Intratemporal

Intracranial

Management

Unsafe CSOM is a surgical disease. There is no definitive non-surgical treatment.

Pre-operative

• Aural toilet (canal débridement)
• Topical antibiotic drops (quinolone-based) to control active infection
• Systemic antibiotics if acutely infected or complication suspected
• CT temporal bone for surgical planning
• Audiometric assessment

Surgical Options

Canal Wall-Up (CWU) Mastoidectomy — Intact Canal Wall

• Posterior canal wall preserved
• Better cosmesis and hearing aid tolerance; faster healing
• Higher recidivism rate: 25–45% — often requires staged "second-look" at 6–12 months
• Preferred when disease is limited and follow-up is reliable

Canal Wall-Down (CWD) Mastoidectomy — Open Cavity

• Posterior canal wall removed → creates open mastoid bowl
• Better exposure of epitympanum and mesotympanum → easier complete disease removal
• Lower recidivism: 6–20%
• Requires long-term cavity debridement; bowl care issues (cerumen retention, infections)
• Preferred in: only-hearing ear, poor anesthetic risk, unreliable follow-up, extensive/recurrent disease, or when CWU leaves residual disease

Radical Mastoidectomy

• Obliteration of the middle ear; combines mastoid and middle ear into one cavity
• Reserved for extensive, unresectable disease or poor surgical candidates

Modified Radical Mastoidectomy (Bondy)

• Canal wall-down with preservation of ossicular chain and intact tympanic membrane remnant

Intraoperative Considerations for Specific Complications

• Matrix over fistula carefully preserved during dissection
• Decision to use CWU vs CWD based on ability to completely eradicate cholesteatoma

• Tympanomastoidectomy with removal of matrix from epineurium
• Decompression proximal and distal to the dehiscent segment
• Opening the epineurium only if cholesteatoma has invaded the nerve sheath
• Recovery to HB Grade I–II in 52–83% of patients

Post-operative Surveillance

• Regular follow-up with otoscopy/microscopy
• DWI-MRI at 12–18 months post-op to detect residual/recurrent disease (avoids second-look surgery in many centres)
• Audiological assessment and hearing rehabilitation as needed
• Hearing aids can be challenging in CWD cavities (↑ infection risk from mold occlusion and moisture trapping)

Key Points Summary

1. Unsafe CSOM = CSOM with cholesteatoma — always associated with bone erosion and risk of serious complications
2. Distinguishing feature: attic/posterosuperior perforation, foul-smelling scanty discharge, bony erosion on CT
3. Bone destruction is osteoclast-mediated via RANKL/RANK pathway, not pressure necrosis
4. Labyrinthine fistula occurs in ~7–10%; horizontal SCC is affected in 98% of cases
5. Facial nerve palsy from cholesteatoma follows a slow progressive course
6. Surgery is mandatory — CWU vs CWD choice balances recidivism risk against cavity morbidity
7. Post-operative non-EPI DWI-MRI has replaced routine second-look surgery in many centres