Chronic Suppurative Otitis Media (CSOM)

Definition

Classification

Pathogenesis / Etiology

1. ET dysfunction → negative middle ear pressure → mucosal edema
2. Bacterial infection → purulent effusion → inflammatory mediators
3. Chronic inflammation → mucosal gland metaplasia (secretory transformation) → perpetuates effusion
4. Granulation tissue forms: bacterial toxins rupture the epithelial basement membrane; inflammatory cells and lamina propria extrude into the middle ear lumen
5. Angiogenic and epithelial growth factors → fibroblast recruitment, neovascularization, polyp formation
6. TM collagen skeleton degraded by enzymes in the granulation tissue → weakening, retraction pockets, perforation
7. Deep retraction pockets or frank perforations → cholesteatoma genesis (squamous epithelium migration into the middle ear)

Microbiology

• Pseudomonas aeruginosa - the most common gram-negative organism; requires higher-dose or specialized antibiotics
• Staphylococcus aureus (including MRSA)
• Proteus, Klebsiella, anaerobes
• Fungal overgrowth is surprisingly common - Candida species grow in ~10% of ears with purulent otorrhea, and in up to 35% of ears treated with topical ciprofloxacin for 3 weeks
• Biofilm formation (bacterial and fungal) is well-established and contributes to treatment resistance

Clinical Features

Symptoms

• Otorrhea - intermittent, sometimes foul-smelling (hallmark symptom)
• Hearing loss - typically conductive; sensorineural component possible
• Otalgia and headache are uncommon - if present, raise suspicion for intracranial complication or malignancy
• Vertigo - suggests labyrinthitis or perilymphatic fistula

Examination

• Tympanic membrane perforation (central or marginal/attic)
• Otorrhea may obscure the TM
• EAC polyps, granulation tissue
• Scutal or ossicular erosion (in advanced/cholesteatoma disease)

Audiometry

• Conductive hearing loss (CHL) is common
• CHL >30 dB suggests ossicular erosion
• Note: hearing can occasionally be preserved despite ossicular erosion if the cholesteatoma itself transmits sound to the oval window
• Sensorineural hearing loss (SNHL) ranging 5-33 dB has been documented and must be recorded preoperatively

Cholesteatoma

• It is expansile, locally destructive
• Erodes ossicles, tegmen, labyrinth, facial nerve canal
• Creates pathways for intracranial spread

• Acquired (most common) - from retraction pocket deepening or epithelial migration through a marginal perforation
• Congenital - white pearly mass behind an intact TM, typically anteromedial quadrant

Investigations

1. Otomicroscopy - gold standard for TM and middle ear evaluation
2. Audiometry (pure tone + tympanometry) - mandatory baseline
3. CT temporal bone (HRCT) - extent of disease, ossicular chain, mastoid pneumatization, tegmen integrity, sigmoid sinus position
4. MRI - superior for soft tissue; DWI-MRI detects cholesteatoma (restricted diffusion) and is useful for follow-up after canal-wall-down mastoidectomy
5. Ear swab - for culture and sensitivity to guide topical/systemic antibiotic choice

Management

Medical (First-line for CSOM without cholesteatoma)

1. Aural toilet - meticulous microsuction/dry mopping to clear discharge
2. Topical antibiotic ear drops - first-line; fluoroquinolone drops (ciprofloxacin, ofloxacin) are preferred as they are non-ototoxic and have excellent gram-negative coverage including Pseudomonas
3. Systemic antibiotics - reserved for acute exacerbations, systemic spread, or when topical therapy fails; guided by culture results
4. Antifungal - if fungal overgrowth suspected (clotrimazole ear drops)
5. Water precautions - protect ear from water ingress

2025 Cochrane evidence update: Three simultaneous Cochrane systematic reviews (Brennan-Jones et al., Head et al., Chong et al., June 2025 - PMIDs 40484407, 40484400, 40484405) confirm that topical antibiotics outperform topical antiseptics and systemic antibiotics for CSOM, reinforcing current practice of prioritizing ototopical fluoroquinolones.

Surgical

• Cholesteatoma (near-absolute indication)
• Medically refractory CSOM (failed multiple medical treatments)
• Complications (vertigo, facial weakness, headache)
• Hearing restoration (ossiculoplasty, tympanoplasty)

1. Eradication of disease
2. Prevention of recurrence
3. Preservation or restoration of hearing

• CWD offers better disease control and lower recurrence but requires lifelong cavity maintenance and restricts water exposure
• CWU preserves anatomy and shorter recovery but higher recurrence; needs second-look surgery

Complications

Extracranial

• Mastoiditis (most common)
• Subperiosteal abscess (postauricular swelling - see image below)
• Facial nerve palsy (VII nerve canal erosion)
• Labyrinthitis / labyrinthine fistula
• Bezold's abscess (pus tracks along sternocleidomastoid)
• Petrositis (Gradenigo's syndrome: otorrhea + diplopia + facial pain)

Intracranial

• Meningitis (most common intracranial complication)
• Brain abscess
• Epidural abscess
• Subdural empyema
• Lateral (sigmoid) sinus thrombosis
• Otitic hydrocephalus

Special Situation: CSOM and Cochlear Implantation

• Dry ear at time of implantation is the key criterion
• Staged approach: (1) mastoidectomy ± ET obliteration to dry the ear; (2) CI 2-6 months later
• Risk of cholesteatoma formation in a closed cavity must be monitored long-term
• Biofilm eradication before electrode insertion is essential to prevent device infection

Summary Table